Associate Professor S. V. GOLASHEVSKY, Assistant A. M. BUZYNNIK, Assistant D. M. LEVIN
and Assistant Yu. N. SOKOLOV.

On the Question of the Use of Artificial Liquid Fuels in Internal-Combustion Engines.

I. THE USE OF FUEL OIL FROM THE SEMI-COKING TAR OF SAPROPELITES OF THE 3rd BARZAS DEPOSIT IN DIESEL ENGINES.

Preface.

The production of liquid fuel by artificial means from coals, oil shales, and sapropelites is a problem of all-Union importance in connection with the year-by-year growing demand for liquid products for the motor-vehicle and tractor fleet, the motor fleet, and stationary installations with internal-combustion engines.

In particular, the present absence on the territory of the Siberian Territory, which has an enormous extent, of developed natural oil deposits, on the one hand, and the presence of colossal reserves of coals yielding large amounts of volatiles and tars, on the other, have brought forward for solution the task of finding the most expedient methods of processing bituminous coals and sapropelites into liquid fuel (semi-coking, hydrogenation, etc.), linked with the interests and the general plan for the development of the national economy of the Territory.

To the young branch of industry being created on the basis of a close linkage of theory and practice—the industry of artificial liquid fuel—belongs an honorable place in socialist construction; at the same time, however, it bears the responsible task of mastering, in the shortest possible time, a number of highly complex technological processes ensuring the sound quality of the product being issued.

The final decision on the suitability for operation in internal-combustion engines of one or another type of artificial liquid fuel must, without doubt, be preceded by serious study and experimental testing of them directly in operation on engines.

From this point of view, the Laboratory of Internal-Combustion Engines of the Siberian Mechanical-Engineering Institute

fuel oil in Tomsk, sufficiently equipped for carrying out scientific research on the study of the properties of new types of fuels directly in engines, is closely connected with the coal industry of the region.

The first steps in this direction were experiments conducted by the former head of the laboratory, Professor A. V. Kvasnikov, in 1930¹), when the first batches of artificial gasoline and kerosene, obtained by semi-coking Barzas sapropelites in the laboratory of Prof. Gebler in Tomsk, were tested in automobile and tractor engines.

After the start-up of the 1st experimental semi-coking plant in the city of Kemerovo in 1931, the possibility arose of developing research work on a broader scale.

At the beginning of 1932, a sample of heavy liquid fuel was received by the laboratory of the Department of Internal Combustion Engines, this fuel being a residue from the distillation of semi-coking tar of sapropelites from the Third Barzas deposit, for the purpose of determining the possibility of using it in Diesel engines.

The study of this fuel was carried out by a group of research workers of the Department of Internal Combustion Engines under the direction of Associate Professor S. V. Golashevsky, with broad involvement of students specializing in internal combustion engines, and with the active participation of the laboratory mechanic, Comrade A. Ya. Tkachenko, who constructed a number of precise measuring instruments and devices necessary for conducting the tests, some of which are his inventions.

The work was carried out simultaneously by three brigades:

1. Brigade for the laboratory study of the fuel: assistant D. M. Levin and students V. G. Panov and Ya. Gavrilyuk.

2. Brigade for testing the Yu. M. T. compression engine: assistant A. M. Buzynnik and students A. V. Dzenskewich, T. Meshcheryakov, and A. Z. Solomyanny.

3. Brigade for testing the Deutz compressionless engine: assistant Yu. N. Sokolov and students V. I. Mukhin, A. Ya. Nusberg, A. N. Sulimov, and V. F. Frolov.

Such organization of the work made it possible, on the basis of socialist competition and shock-work methods, to carry out the research in the shortest possible time.

The results obtained were reported at the 1st expanded plenum of the Regional Committee for the Chemization of the National Economy of Western Siberia (March 15–20, 1932), at the 1st Regional Energy Congress of Western Siberia²) (June 18–22, 1932),

¹) A. V. Kvasnikov, “Preliminary Tests in Engines of Trial Fuels from Tar of Barzas Sapropelites.” Journal For Coal of the East, Novosibirsk, 1931, No. 13, p. 32.

²) S. V. Golashevsky, “Use of Liquid Products of Semi-Coking of Barzas Sapropelites in Internal-Combustion Engines.” Proceedings of the First Regional Energy Congress of Western Siberia. Novosibirsk, 1932, pp. 359–372.

and the full technical report was transferred to the trust “Ugleregonka,” with whose funds the present investigations were carried out.

The former Siberian Branch of the All-Union Heat-Engineering Institute (SOVTI), which provided financial assistance for carrying out the preparatory work, took part in organizing and preparing the experiments.

The work here published consists of four parts:

Part I—laboratory investigations to determine the physicochemical properties of sapropelite fuel oil;

Part II—comparative tests of a compressor engine on petroleum motor fuel and sapropelite fuel oil;

Part III—comparative tests of a Deutz-type “PM” non-compressor prechamber engine on petroleum motor fuel and sapropelite fuel oil;

Part IV—general conclusions and findings.

The degree of participation of each scientific worker in carrying out and preparing the present work was as follows:

1. Assistant D. M. Levin—supervision and monitoring of the laboratory investigation of the fuel.

2. Assistant A. M. Buzynnik—direction of the team testing the Yu. M. T. compressor engine and processing of the experimental material.

3. Assistant Yu. N. Sokolov—direction of the team testing the Deutz non-compressor engine, processing of the experimental material, and literary preparation of Part III.

4. Docent S. V. Golashevsky—general direction of the test methodology, literary preparation of Parts I, II, and IV, and overall editing of the entire work.

Part I.

CHARACTERISTICS OF FUEL OIL FROM SAPROPELITE TAR.

The heavy fuel obtained by the Kemerovo Experimental Semi-Coking Plant and sent for investigation to the Laboratory of Internal Combustion Engines of the SMMI is the residue after distilling gasoline and kerosene fractions from sapropelite tar of the Third Barzas deposit. According to the terminology adopted in the oil-refining industry, it has been given the name “sapropelite fuel oil.”

In external appearance, sapropelite fuel oil is a rather viscous liquid, dark brown in color, with a specific odor revealing the presence in it of aromatics and phenols.

In its elemental composition, presented in Table I, this fuel differs from petroleum fuel by a lower percentage content of carbon and hydrogen and by a larger amount of oxy-

of hydrogen included in its oxygen compounds (phenol and its homologues), which substantially distinguishes sapropelite fuel oil from analogous types of liquid fuels obtained from natural petroleum and brings it closer to products from coal tar.

The laboratory study of sapropelite fuel oil yielded a number of constants characterizing it as a fuel for Diesel engines. The results are summarized in Table II. The latter gives analogous investigations of the petroleum motor fuel used for the comparative tests and the figures established as standards for petroleum fuel, adopted by the Fourth All-Union Heat-Engineering Congress.

Table I.

Elementary composition of sapropelite fuel oil and petroleum motor fuel.

Nos.	Name of elements	Symbol	Sapropelite fuel oil¹)	Petroleum motor fuel (average composition)
1	Carbon	C	84.30%	86.0%
2	Hydrogen	H	9.73%	12.7%
3	Oxygen	O
4	Nitrogen	N	5.48%	1.3%
5	Sulfur	S	0.48%

1. Specific gravity, used in tests of petroleum motor fuel and sapropelite fuel oil, falls outside the limits of the standards. This constant is not a criterion for assessing the suitability of a fuel as motor fuel. Nevertheless, it makes it possible to judge its qualitative composition, the predominance in it of particular hydrocarbon compounds, and the quantitative content in it of the principal elements—carbon and hydrogen.

Repeated comparison of the specific gravity of liquid fuels with their calorific value allows some authors²) to give an (approximate) formula for determining the calorific value of a liquid fuel as a function of its specific gravity.

In those cases, too, when in engine tests the fuel consumption is determined by the volumetric method, knowledge of its specific gravity is absolutely necessary.

In view of the absence of literature data on temperature corrections for reducing the value of the specific gravity to normal technical conditions, we carried out special experiments

¹) The analysis was carried out in the Laboratory of Analytical Chemistry of the SHTI.
²) Kants[e]r K. M.—Ship internal-combustion engines, 1931, p. 23.

to determine the dependence of the specific gravity of the sapropelite fuel oil under investigation on temperature.

Table II.

Results of the investigation of the fuels used in the experiments.

No. in order	Name of determination	Technical specifications for petroleum fuel for heavy internal-combustion engines.¹)	Petroleum motor fuel used in the experiments.	Sapropelite fuel oil from tar of the Third Barzas deposit.
1	Specific gravity at 15°C	0.855–0.900	0.911	0.982
2	Engler viscosity at 50°C	Not over 5.0	2.22	5.03
3	Pour point	Not above +5.0	Below −19.0	+13.0
4	Flash point by Marcusson, °C	45–120	78.7	134.7
5	Ignition temperature in the Marcusson apparatus, °C	—	118.7	175.3
6	Initial boiling point, °C	—	—	+248²)
7	Ditto, in the Le Bel–Henninger apparatus	—	118.0°	+261°
8	Residue after 350°C	Not over 45%	—	42.9%²)
9	Ditto, in the Le Bel–Henninger apparatus	—	62%	74.0%
10	Conradson coking value	Not over 3%	1.97%	7.5%
11	Water content	Not over 1%	0.6%	Traces
12	Content of mechanical impurities	Not over 0.3%	0.19%	0.03%
13	Ash content	0.10%	0.08%	0.01%
14	Sulfur content	0.50%	—	0.48%³)
15	Mineral acidity	0.0	—	0.0²)
16	Calorific value by bomb, higher (cal./kg)	—	10640	10060
17	Ditto, lower	—	9960	9520

This dependence is presented graphically in Fig. 1, and the numerical values are brought together in Table III.

As is seen from Fig. 1, the change in the specific gravity of the sapropelite fuel oil with increasing temperature within the limits from +15 to

¹) Developed and adopted by the IV VTS.
²) According to data of the Laboratory of the Kemerovo Experimental Plant.
³) According to data of the Laboratory of Analytical Chemistry of the SKhTI.

+55°C proceeds along a straight line with a somewhat greater inclination to the abscissa axis than for petroleum products. In the diagram presented here, the dotted line shows the curve of change in specific gravity for petroleum motor fuel, constructed according to the equation:

\[ \gamma_t = \gamma_{15} + a(t - t_{15}) \tag{1} \]

where: \(a\)—the magnitude of the correction for each degree of temperature change—is taken according to Mendeleev, equal, for the petroleum motor fuel used, to \(0{,}00062\)¹).

Fig. 1. Dependence of specific gravity on temperature.

Direct determination of the specific gravity by the hydrometric method for sapropelite fuel oil at various temperatures shows that the corrections existing for petroleum fuels are not applicable to this grade of liquid semi-coking products.

Table III.

Dependence of the specific gravity of sapropelite fuel oil on temperature.

No. of experiments	Temperature, °C	Specific gravity, g/cm³
1	15	0,982
2	25	0,974
3	35	0,967
4	45	0,958
5	55	0,952

The resulting difference, shown in Fig. 1 by the segment \(\Delta\gamma\), is quite considerable and at 55°C already affects the second decimal place, amounting to a difference of 1.2%.

¹) Bauman A. G.—Lubricating Oils of the USSR and the Technique of Their Application. 1925, pp. 55–56.

For the grade of sapropelite fuel oil under investigation, the dependence of specific gravity on temperature may be represented by the equation:

\[ \gamma=\gamma_{15}+\beta(t-t_{15}) \ldots \ldots \ldots \ldots \ldots \ldots \ldots (2) \]

where: \(\beta\)—the temperature correction should be taken as equal to 0.00075 for each degree of temperature difference.

1. Viscosity, which is a measure of the fluidity and mobility of a fuel, proved to be considerably greater for sapropelite fuel oil than for petroleum motor fuel.

At \(50^\circ\)C—the temperature conventionally taken as normal for comparing heavy grades of fuel—the viscosity of sapropelite fuel oil is two and a quarter times greater than that of the petroleum motor fuel used, practically coinciding with the upper limit permitted by the standards.

The nature of the dependence of the viscosity of both fuels on temperature is given in Fig. 2. Their numerical viscosity values, determined with Engler’s apparatus, are presented in Table IV.

Fig. 2. Dependence of viscosity on temperature.

In direct connection with viscosity is the tendency of the fuel to thicken. The latter is characterized by the solidification temperature,

1. Solidification temperature, determined by the generally accepted method, proved for sapropelite fuel oil to be considerably above the standard. That is, at the comparatively high temperature of \(+13^\circ\)C, precipitation of its constituent parts in solid form is observed.

This property is a negative indicator, showing that when sapropelite fuel oil is used at low temperatures (wintertime, poorly heated premises), additional heating is necessary in order to impart fluidity to it.

However, from the standpoint of the possibility of using it as a motor fuel, the value obtained for the solidification temperature should not cause concern.

Table IV.

Viscosity of petroleum fuel oil and sapropelite fuel oil.

Experiment Nos.	Temperature	Viscosity in degrees Engler. Petroleum motor fuel	Viscosity in degrees Engler. Sapropelite fuel oil
1	20°C	6.36	29.10
2	50°C	2.22	5.03
3	75°C	1.62	2.09
4	100°C	1.26	1.45

A number of experimental investigations in recent times have shown the possibility of using paraffinic fuel oils in Diesel engines, with a pour point reaching even as high as \(+35^\circ\text{C}\) ^1).

4—5. Flash point and ignition temperature, being quantities not characteristic for evaluating the suitability of a fuel for internal-combustion engines, merely indicate the presence in it of light fractions boiling at comparatively low temperatures.

6. Indeed, fractional distillation, carried out in the Internal-Combustion Engine Laboratory on the Leun-Bord apparatus, showed a higher initial boiling temperature of the sapropelite fuel oil and a larger amount of fractions boiling above \(350^\circ\text{C}\). The residue above \(350^\circ\text{C}\) for the sapropelite fuel oil proved to be 1.2 times greater than for petroleum motor fuel.

The residue above \(350^\circ\text{C}\), as determined by the Laboratory of the Kemerovo plant, amounts to 42.9% of the original product. The same value, obtained by us on the Leun-Bord apparatus, is equal to 72.0%.

Such a large difference must evidently be attributed to the difference in the methods of determination and to the conventions adopted in the methods used in the two cases.

On the Leun-Bord apparatus the thermometer indicating the temperature at which distillation takes place is immersed in the heated liquid, whereas in the Engler–Ubbelohde apparatus the bulb of the thermometer is located in the vapors of the boiling liquid.

The initial boiling temperatures of petroleum motor fuel, \(+118^\circ\text{C}\), and of sapropelite fuel oil, \(+261^\circ\text{C}\), determined by one and the same method (Leun-Bord), indicate a great homo—

^1) News of Soviet and Foreign Transport Technology, issue I, 1931: “Use of paraffinic fuel oils in internal-combustion engines.”

...similarity of the latter. This circumstance should have a favorable effect on the rate of combustion of sapropelite fuel oil in engines.

1. A figure deserving attention is the one characterizing the fuel’s tendency toward carbon-deposit formation, i.e., its coking capacity, determined with the Conradson apparatus.

The conditions under which coke is obtained by this method differ from those in which the fuel burning in the cylinder is placed. Nevertheless, in certain places in the inner cavity of the cylinder we may find so-called dead corners, deprived of a constant supply of fresh portions of air because of the absence of turbulence in them. The conditions of coke formation in these places of the engine combustion chamber differ little from the conditions present in the Conradson laboratory apparatus.

The coke content in sapropelite fuel oil, equal to 7.5%, whereas the standards allow not more than 3%, compels special attention to be paid to this circumstance and, in operation on machines, to observe how far the greater tendency toward coke formation causes incomplete combustion and contamination of the inner cavity, the distribution organs, and the exhaust system of the engine.

11, 12, 13. The contamination of sapropelite fuel oil with mechanical impurities, ash, and water is considerably less than that of petroleum motor fuel, as is seen from Table II.

1. The sulfur content—0.48%—does not go beyond the standards established by the technical specifications for the supply of petroleum motor fuel.

2. The mineral acidity is 0.0.

16–17. The calorific value (higher), determined by direct combustion of an average sample in a bomb, gave a value (the average of three determinations) equal to

\[ Q_{в}^{p} = 10060\ \text{cal/kg}. \]

The lower calorific value, ordinarily used in compiling heat balances, was found by us by calculation after the elemental analysis of the sapropelite fuel oil had been carried out, according to formula 1):

\[ Q_{н}^{p} = Q_{в}^{p} - \left(\frac{W}{100} + \frac{9H}{100}\right) \cdot 600\ \text{cal/kg} \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ . \ (3) \]

where: \(W\)—water content in the fuel, in %%;
\(H\)—hydrogen content in the fuel, in %%.

1) Zas F. Compressorless Diesel Engines. 1931, p. 15.

The lower heating value was found to be:

\[ Q_{H}^{P}=9520\ \text{cal/kg}. \]

For petroleum motor fuel the following values were found by the same method:

\[ Q_{B}^{P}=10640\ \text{cal/kg}; \]

\[ Q_{H}^{P}=9960\ \text{cal/kg}. \]

It is of some interest to compare the values of the heating value determined in the bomb with those calculated by the most widely used formulas.

Table V below gives an idea of this. Of the formulas cited, the formula of the Society of German Engineers gives the value of \(Q_{H}^{P}\) that differs least. The difference is

\[ 9520-9465=55\ \text{cal/kg}, \]

or, in percent,

\[ \frac{55\cdot100}{9520}=0.58\%, \]

which may be explained, on the one hand, by the permissible error of the determinations and, on the other, by the presence of endothermic reactions in the process of formation or production of the fuel, which resulted in an increased calorimetric effect upon its direct combustion.

Table V.

Values of the heating value of sapropelite fuel oil, calculated by formulas.

No.	Name of formula	Type of formula	Lower heating value, cal/kg	Difference in %% from that determined in the bomb, %%
1	Dulonga	\(81.4C+342\left(H-\dfrac{O}{8}\right)+25S-6(W+9H)\)	9431	\(-0.935\)
2	Soc. of German Engineers	\(81C+290\left(H-\dfrac{O}{8}\right)+25S\)	9465	\(-0.578\)
3	Mendeleev’s	\(81C+300H-26(O-S)-6.9H\)	9352	\(-1.76\)
4	By specific gravity¹	\(6600+\dfrac{3000}{\gamma}\)	9655	\(+1.42\)

Lower heating value by the bomb:

\[ Q_{H}^{P}=9520\ \text{cal/kg}. \]

¹ Kantser K. M.—Marine Internal-Combustion Engines. 1931, p. 23.

1. For a complete characterization of the fuel under consideration, it is also desirable to know the theoretical quantity of air necessary for its complete combustion. Having the elemental composition of sapropelite fuel oil, one can readily determine \(L_0\) from the formulas.

\[ L_0=\frac{8/3\cdot C+8\cdot H+S-O}{23\cdot \gamma_{\text{air}}} \tag{4} \]

Substituting into formula (4) the values \(C, H, O, S\) for sapropelite fuel oil and \(\gamma\) for air, we find:

\[ L_0^c=\frac{8/3\cdot 84.3+8\cdot 9.7+0.48-5.48}{23\cdot 1.293} =9.92\ \text{m}^3/\text{kg} \]

at \(0^\circ\) and 760 mm Hg,

or \(10.14\ \text{m}^3/\text{kg}\) of air under normal technical conditions
(\(15^\circ\text{C}\) and 737.4 mm Hg).

Analogous calculations for petroleum motor fuel of average composition, given in Table 1, yield:

\[ L_0^n=11.12\ \text{m}^3/\text{kg} \]

at \(0^\circ\text{C}\) and 760 mm Hg,

and

\[ L_0^n=12.05\ \text{m}^3/\text{kg} \]

at \(15^\circ\text{C}\) and 737.4 mm Hg.

Comparison of the values of the theoretical quantities of air for both types of fuel under identical temperature and barometric conditions indicates that 1 kg of sapropelite fuel oil requires

\[ 12.05-10.14=1.91\ \text{m}^3 \]

less air than petroleum motor fuel, or in percent:

\[ \frac{1.91}{12.05}\cdot 100=15.9\sim 16\% \]

less than petroleum motor fuel.

This circumstance is of substantial importance for an internal-combustion engine and cannot fail to affect its economy and the maximum power developed by the engine, both in the cylinder (indicator power) and on the shaft (effective power).

Thus, the laboratory investigation of sapropelite fuel oil from the Third Barzas deposit makes it possible to conclude that, although in comparison with the normal petroleum motor fuel in use it deviates considerably in certain cases from the established standards, nevertheless, as a fuel for heavy internal-combustion engines it may be employed.

A detailed answer regarding the possibility of using it as a fuel for diesels is given in the following chapters, which describe the setup and the results of investigations of the operation of compression and prechamber engines carried out in the Laboratory of Internal Combustion Engines of the SMMKI.

Part II.

COMPARATIVE TESTS OF SAPROPELITE FUEL OIL IN A COMPRESSORLESS DIESEL ENGINE

1. Brief description of the engine and its principal data.

The investigation of the possibility of using sapropelite fuel oil as a fuel for compressorless diesel engines was carried out on a single-cylinder, four-stroke, vertical machine

Fig. 3. Longitudinal section of the compressorless Yu. M. T. engine.

with a power of 15 h.p. at 235 revolutions per minute, built by the diesel shop of the Nikolaev State Shipbuilding Plants named after A. Marti, Yuzhmash Trust (YuMT), 1926 production.

As can be seen from the drawing presented in Fig. 3, the engine tested is a typical representative of stationary machines with an A-shaped frame.

The working process is carried out in four strokes. Fuel is supplied to the cylinder by an injector, the lower part of which is shown in section in Fig. 4. The compressed air required for atomizing the fuel is prepared by a two-stage compressor mounted in the middle part of the engine frame and driven through a rocker arm from the main connecting rod.

The principal data characterizing the engine described are as follows:

Fig. 4. Lower part of the injector of the YuMT engine.

1. Cylinder diameter . . . . . . . . . . . . . . . . . . . . . . \(D = 215\) mm.
2. Piston stroke . . . . . . . . . . . . . . . . . . . . . . . . \(S = 340\) mm.
3. Working volume of the cylinder . . . . . . . . . . . . \(V_h = 12.337\) l.
4. Volume of the combustion chamber¹ . . . . . . \(V_c = 0.975\) l.
5. Compression ratio (in the cold state) . . . . . . . .

\[ \varepsilon = \frac{V_h + V_c}{V_c} = \frac{12.337 + 0.975}{0.975} = 13.65. \]

The diagram in Fig. 5 shows the principal timing points of the engine, referred to the angles of rotation of the main shaft, taken directly from the engine in the cold state.

Points 1 and 2 denote the beginning and end of opening of the intake valve, 5 and 6 the beginning and end of opening of the exhaust valve, and 3 and 4 the beginning and end of lift of the injector needle.

The numerical values of the principal timing points are presented in Table VI, where the minus sign before the number denotes—

¹ Determined by filling with water.

means the number of degrees before, and “plus” after, the corresponding dead center.

Fig. 5. Diagram of the timing points of the UMT engine.

Table VI.

Timing points of the UMT engine.

No.	Name of timing components	Timing points in degrees of crankshaft rotation: opens	Timing points in degrees of crankshaft rotation: closes	Duration of the opening period in degrees
1	Intake valve	−15°	+19°	214°
2	Exhaust valve	−37°	+12°	229°
3	Fuel valve (injector needle)	−4°	+38°	42°
4	Starting valve	−11°	+65°	76°

Fig. 6 shows the general view of the engine, equipped with all instruments necessary for the test.

Fig. 6. General view of the YuMT engine.

II. Methods of Measurements and Observations

1. Fuel consumption.

Determination of the quantity of fuel consumed by the engine was carried out by the volumetric method. In the immediate vicinity of the fuel pump, on the pipeline supplying fuel from the pressure tank (see the diagram in Fig. 7), a measuring instrument was installed, resembling in its design the so-called Zeppelin graduated pipette¹.

The instrument was made by the laboratory mechanic, Comrade A. Ya. Tkachenko. The measuring vessels, as well as the upper and lower reservoirs, were made of brass. The brass vessels are connected to one another by glass tubes 10 mm in diameter.

Before the experiments the instrument was calibrated for each fuel. During the experiments the largest possible number of measurements was made in order to obtain the smallest error in determining the fuel consumption.

From the mean value of the time required for discharge of the calibrated vessel, the hourly fuel consumption in kg was determined by the formula:

\[ G = 3600 \cdot \frac{V}{t} \cdot \gamma_t \ \text{kg/hour} \ldots \ldots \ldots \ldots (5) \]

where:

\(G\)—fuel consumption in kg per hour;
\(V\)—volume of the discharge reservoir of the graduated pipette in liters;
\(t\)—time of fuel discharge in seconds;
\(\gamma_t\)—specific weight of the fuel corresponding to its mean temperature during the time \(t\)².

The temperature of the fuel was measured with a thermometer installed immediately behind the instrument.

The volumetric method of measuring fuel consumption, while possessing a number of advantages (compactness of the instrument, simplicity of operations, hermetic sealing of the instrument, etc.), when applied to heavy fuels loses its valuable qualities owing to the considerable viscosity of the latter.

Work with the indicated instrument on fuels not requiring heating can be performed with sufficient accuracy. Only calibration of the measuring vessels with the working fuel, and not with water, is obligatory.

If it is necessary to heat thick grades of fuel in the pressure tank, then, owing to the comparatively large cooling surface of the instrument and the considerable duration of the measurement, the fuel in it cools to such an extent that either additional heating of it in the measuring instrument is required, or else the instrument must be abandoned and the volumetric method replaced by a weighing method.

The layout of the fuel line with the instruments installed on it is shown in Fig. 7. Its design provides for the possibility of converting the engine to heavy grades of motor fuel.

If necessary, the fuel can be heated by switching the engine to supply from a second pressure tank, fitted with a coil connected to the steam-heating pipeline.

2. Engine-shaft power (effective) was determined by a braking device mounted on the flywheel. A thin brass band encircling the rim of the flywheel (see Fig. 8) was loaded at one end with weights \(G\). The tension of its running end, determined by a dynamometer, was adjusted during engine operation by handle “\(M\)” so that the pointer on traverse “\(T\)” remained in the same position under different loads.

Fig. 7. Layout of the fuel pipelines of the YuMT engine.

The total weight of the entire braking device, “\(g\),” reduced to the point of application of the load “\(G\),” was determined by direct weighing on a specially prepared template.

The effective power was calculated according to the generally known formula:

\[ Ne=\frac{P\cdot R\cdot n}{716.2}\ \text{h.p.}\ .\ .\ .\ .\ .\ .\ .\ .\ .\ (6) \]

where: \(P=(G+g-s)\)—circumferential force on the flywheel rim, in kg;
\(R\)—radius of the flywheel, in m;
\(n\)—number of revolutions per minute;
\(g\)—reduced weight of the brake, in kg;
\(s\)—dynamometer reading, in kg.

To monitor the engine speed, a stationary-type tachometer was used. The exact value of the number of revolutions was deter—

was done by means of a tachoscope (a hand-operated totalizing revolution counter with a stopwatch).

For observing the uniformity of the engine’s operation, a Horn tachograph was installed.

1. The indicated power of the engine was determined by means of an indicator made by Lehman & Michels (Grösse 2), with a piston diameter of 14.35 mm.

Fig. 8. Diagram of the braking device for the UMT engine.

The serviceability of the indicator mechanism, the magnitude of its own friction, and the true scale of the springs used during the tests were determined before the experiments.

The compressor was not indicated. Diagrams of the main cylinder were taken both as normal diagrams along the piston stroke and as displaced diagrams.

The drive to the indicator for obtaining ordinary diagrams was left as the factory (lever) drive. The displaced diagrams were obtained by means of an end-mounted stroke-reducer, displaced correspondingly with respect to the piston stroke by 90°.

The mean indicated pressure was determined with Amsler planimeters.

The formula used for calculating the indicated power was:

\[ N_u = \frac{P_u \cdot \pi \cdot D^2 \cdot S \cdot n}{4 \cdot 60 \cdot 75 \cdot 2} \ \text{h.p.} \ldots \ldots \ldots (7) \]

1. The consumption of water cooling the machine was measured by weighing. The water from the head and the jacket was collected separately in iron tanks mounted on scales.

2. The analysis of the exhaust gases was carried out with an Orsat apparatus. CO₂ and O₂ were determined.

The gases for analysis were taken into the apparatus from the exhaust pipe through a cock located in the immediate vicinity of the place where their temperature was measured.

Fig. 9. Chart for checking the analysis of exhaust gases and determining “α”.

To verify the correctness of the results of the analysis, the graph shown in Fig. 9, constructed for both grades of fuels used, was employed.

6. Excess-air coefficient was determined from the analysis of the exhaust gases with the aid of the curves of variation of “α,” plotted on the graph in Fig. 9 for petroleum motor fuel and sapropelite fuel oil, as a function of the percentage content of \(CO_2\) in the exhaust gases.

7. Determination of the heat carried away by the exhaust gases. This item of the heat balance was calculated by the formula¹:

\[ Q_{o.g}=G\left[\frac{C}{CO_2}(A+B\cdot CO_2)+BH\right](t_{o.g}-t_n)\ldots \tag{8} \]

where: \(G\)—hourly fuel consumption in kg/hour; \(C\) and \(H\)—the content of carbon and hydrogen in it;

\(CO_2\)—the content of carbon dioxide in the products of combustion;

\(A\), \(B\), and \(В\)—coefficients, the values of which are obtained after substitution into the basic formula of the variable heat capacities of diatomic gases, carbon dioxide, and water vapor, taken according to the formulas of Holborn and Henning.

The use of this formula, which is approximate, since it assumes that the exhaust gases contain no products of incomplete combustion (\(CO\), heavy hydrocarbons), has the advantage that, when tables with precomputed values of the coefficients \(A\), \(B\), and \(В\)² are available, it is possible, avoiding laborious calculations, to obtain sufficiently accurate results quickly.

Calculation of the heat carried away by the exhaust gases by the above formula is entirely possible when various grades of liquid fuel are used in the engine. Only knowledge of its elemental composition is obligatory.

8. Measurement of the temperatures of the incoming and outgoing water, fuel, and room was carried out with mercury centigrade thermometers, checked before the experiment.

For measuring the temperature of the exhaust gases on the exhaust pipe, at a distance of two diameters from the exhaust flange of the cylinder head, a mercury glass thermometer with divisions up to \(360^\circ C\) was installed.

Higher temperatures were measured by means of a mercury-spring thermometer graduated up to \(450^\circ C\). The readings of the latter were compared with the readings of the glass thermometer.

9. Conditions of the experiments and testing procedure. The initial test program for both fuels

provided for a fairly substantial amount of research not only to compare the operation of the engine on both fuels under identical conditions, but also to determine the optimum conditions for this new type of fuel, with the aim of studying in detail its properties as a motor fuel.

However, the available quantity of fuel delivered for the tests, and a number of other circumstances, made it necessary to confine ourselves to taking the engine characteristic as a function of power, and to pay special attention to factors of an operational nature: starting, carbon formation, etc., since this was possible even though prolonged tests could not be carried out.

The preliminary tests of the engine on petroleum motor fuel made it possible to determine:

1) the injection-air pressure corresponding to the greatest economy of engine operation at each load;

2) the nozzle-orifice diameter most advantageous from the standpoint of minimum fuel consumption at full load;

3) the best quality of lubrication.

In accordance with these conditions, the experiments were carried out in two series:

1) on petroleum motor fuel,

2) on sapropelite fuel oil from the tar of the Third Barzas deposit, at various loads, beginning with idling and extending to the maximum possible sustained overload.

The injection-air pressure for each load was selected on the basis of preliminary experiments within the range from 50 to 68 atm, and in both series, at identical loads, was maintained as far as possible at the same value.

The injection nozzle had a diameter of 1.98 mm; the number of atomizing rings was 3.

Observations were made only after the engine had reached a steady thermal state, as judged by the temperature of the cooling water, the exhaust gases, the CO₂ content in the products of combustion, the appearance of the indicator diagram, and the constancy of the number of revolutions.

In order to eliminate the influence of the variable factor—the operation of the compressor—on the magnitude of the indicated power of the engine, the pressure in the compressor cooler was maintained, in all experiments, as far as possible at the same value.

The duration of each experiment, after a steady state had been established, was chosen as one hour. Individual measurements were made at ten-minute intervals, simultaneously, on a conventional signal.

III. Results of the Tests and Analysis of the Data Obtained

1. Starting the Engine on Sapropelite Fuel Oil

The increased viscosity of the fuel oil in comparison with normal petroleum fuel, as well as the presence in it of aromatic com-

...compounds and phenols initially raised concerns about the possibility of easy starting of the engine.

The first trials of starting the engine in motion were carried out on fuel oil heated to 50–60° C.

The results obtained were satisfactory.

A gradual lowering of the fuel temperature to 20° C did not cause interruptions in the subsequent operation of the engine. In this first experiment in converting a compressor-type machine to sapropelite fuel oil, the engine operated well at various loads, permitting a considerable overload of up to 20% above its normal power.

Subsequent repeated starts of the cold machine directly on sapropelite fuel oil at a temperature of 17–20° C gave quite favorable results. After accelerating the engine with starting air at a pressure of 50–58 atm to 100 rpm, when the control handle was shifted from the starting to the working position, the engine gave flashes and gradually picked up speed on the first attempt.

Indicator diagrams taken during the starting period on petroleum motor fuel and on sapropelite fuel oil nevertheless indicate that the first flashes of the latter are delayed, causing a more sluggish picking up of speed and somewhat lengthening the starting period.

2. Operation of the engine at various loads

In order to characterize the behavior of the engine under operating conditions at various loads (the normal conditions of its operation in service), two series of comparative experiments were carried out:

1) Series “$H — Ne$”—on petroleum motor fuel,

2) Series “$C — Ne$”—on sapropelite fuel oil.

The results of comparative tests of the engine on both grades of fuel are presented in the form of curves and diagrams in Figs. 10 to 14.

Fig. 10. Curves of fuel consumption, number of revolutions, and fuel temperature of the UMT engine.

In the drawing of Fig. 10 are plotted the curves of the change in hourly ($G$) and specific fuel consumptions: for effective ($g_e$) and indicated ($g_i$) horsepower per hour, the number of revolutions (curve “$n$”), and the fuel temperature $t_T$ as a function of engine load.

Of particular interest are the curves “$g_e$,” which give an idea of the economy of the engine at various loads.

In the load range from \(1/4\) to \(3/4\), the curve “\(g_e\)” for sapropelite fuel oil lies above the analogous curve for petroleum motor fuel. This indicates lower efficiency of the engine at low loads when operating on sapropelite fuel oil.

The numerical values of the specific fuel consumptions are given in column “17” of the summary table of test results.

At a load of \(1/4\) of full load, the excess consumption of sapropelite fuel oil was

\[ \text{sapropelite fuel oil by } \frac{583.5 - 423}{423}\cdot 100 = 14.3\%. \]

At a load of \(1/2\), it was

\[ \frac{292 - 273}{273}\cdot 100 = 7.0\%. \]

The consumption at \(3/4\) load becomes practically the same, and at full load the engine consumes \(7.7\ \text{g/e.h.p.-h}\) less sapropelite fuel oil than petroleum motor fuel.

The so-called economic efficiency coefficient, which serves to evaluate heat utilization and represents the ratio of the heat converted into useful work on the shaft to the heat of the fuel, and which is calculated by the formula:

\[ \eta_e=\frac{632.3\cdot Ne}{G\cdot Q_H^P}. \tag{9} \]

for various loads, was plotted as a curve in Fig. 11. From a comparison of the \(\eta_e\) curves for both fuels it is evident that heat utilization in the case of sapropelite fuel oil, under normal operating conditions of the engine at full load, is better by

\[ \frac{30.6 - 28.2}{28.2}\cdot 100 = 8.5\%, \]

amounting to \(30.6\%\) of the heat of the fuel.

Fig. 11. Curves of efficiency coefficients of the UMT engine.

The increased consumption of sapropelite fuel oil in comparison with petroleum motor fuel at low loads, and the practically identical—or even somewhat lower—consumption at higher loads, must be explained entirely by the character of its combustion.

(This question is treated in greater detail below in the chapter “Characteristics of the combustion process.”)

The divergence of the curves \(\eta_m\)—the mechanical efficiency—may be explained by different conditions of piston lubrication in the two series of experiments.

In the “H-Ne” series, the unburned particles of oil, which has a lower viscosity than lubricating oil, settling on the cylinder walls, dilute the lubricant, thereby reducing the friction work of the piston.

The incomplete combustion of sapropelite fuel oil, especially at low loads, causes less dilution of the lubricant because of the greater viscosity of the fuel oil.

The different viscosity of the piston lubricant therefore caused greater mechanical losses and, in connection with this, higher values of the mean indicated pressure in the “C-Ne” series at identical values of \(P_e\) and \(Ne\) in both cases.

The heat distribution in the engine is presented in the form of heat balances for one hour of its operation. Fig. 12-A gives an idea of the nature of the variation of the different heat losses and of the heat converted into useful work under different lo—

Fig. 12. Heat balances in percent for the UMT engine operating on petroleum motor fuel for loads.

Here: \(Q_e\) denotes the heat converted into effective work;
\(Q_v\)—the heat carried away by the cooling water;
\(Q_{og}\)—the heat carried away by the exhaust gases;
\(Q_{ost}\)—unaccounted-for heat (incomplete combustion, mechanical losses, and radiation).

Fig. 12-B represents an analogous balance for operation of the engine on sapropelite fuel oil.

Comparison of the heat balances of the engine’s operation on both fuels makes it possible easily to carry out a quantitative and qualitative comparison of them.

In Figs. 13-A and B the heat balances are plotted in calories per 1 effective horsepower-hour.

The specific heat expenditures are denoted by the letter \(q\), with subscripts having the same meaning as in the balances of Fig. 12.

The figures at the points of the upper curve represent the value of the hourly heat consumption per 1 effective horsepower-hour.

For comparison of the expenditure of thermal energy and its distribution during operation of the engine on both fuels at full load, Figs. 14-a and b give Sankey diagrams obtained from the preceding diagrams.

The losses to the water and with the exhaust gases in both cases prove to be approximately the same.

The increase in the heat flow, equiva-

a. Petroleum motor fuel

b. Sapropelite fuel oil

Fig. 13 A and B. Heat balances in calories per 1 effective h.p.-h of the UMT engine.

Fig. 14 a and b. Sankey diagrams for full load.

useful work of the engine at the shaft, for case “b” (sapropelite fuel oil), by 8.16%, with a smaller absolute value of the heat supplied by 7.6%, occurs at the expense of a reduction in unaccounted losses, chiefly incomplete combustion. This is indicated by the decrease in the residual term when changing from petroleum fuel to sapropelite fuel oil from 19.4% to 16%, i.e., by 17.5%.

IV. Characterization of the combustion process.

In evaluating the operation of an engine on one fuel or another, the experimental investigation of the combustion process is of essential importance.

The latter is made difficult by the fact that the interval of time allotted in heavy-fuel engines for preparation of the working mixture and for combustion proper is very short.

Thus, for example, the entire period of opening of the injector needle, as is evident from the diagram in Fig. 5 and from Table VI, for our case is determined as 40° of crankshaft rotation, which, for the normal speed \(n = 235\) per min., amounts on the average to:

\[ \tau = \frac{40}{6 \cdot n} = \frac{40}{6 \cdot 235} = 0.028 \text{ sec.} \]

Precise study and investigation of the physicochemical processes occurring in the cylinder, beginning from the moment of injection of fuel into it, is complicated by the fact that at the start of the reaction both components are in two phases: the fuel is in the liquid phase, while the oxygen of the air filling the cylinder is in the gaseous phase.^1

Investigations by many researchers in recent times have led to the conclusion that self-ignition occurs when a significant quantity of fuel is still in the droplet-liquid state.

^1 Hartner-Seberich. Der Zündverzug bei flüssigen Brennstoffen. Forschungsheft. 299. 1928.

The entire combustion process may be divided into several successive phases, substantially differing from one another, and, of course, interrelated and influencing one another.

As applied to heavy-fuel engines, the entire period usually called the combustion process may be divided into three phases¹.

The first phase, determined, on the one hand, by the beginning of fuel injection into the combustion space and, on the other, by the beginning of the pressure rise, is characterized by the fact that during it there occurs a whole series of complex phenomena of a physicochemical nature, such as: heating of the droplets of the injected fuel as a result of heat transfer, partial evaporation, adsorption, diffusion, oxidation and decomposition of hydrocarbon molecules, formation of peroxides (peroxides, moloxides), possibly partial pyrogenetic decomposition, and the phenomenon of cracking.

As Prof. K. Neumann² indicates, in the process of heating a droplet of liquid fuel injected into the cylinder of an engine to the autoignition temperature, the chief role belongs not to heat transfer, but to the chemical reactions occurring in the boundary layer of the phase interface.

Experiments carried out by VNIIDI³ show quite convincingly that the heating of hydrocarbon fuels in the presence of atmospheric oxygen is accompanied by the appearance of a “cold flame,” which, with further supply of heat, passes into autoignition.

Therefore this phase may be characterized mainly as a period of “invisible combustion,” preparing the ground for the creation of local flame centers by the beginning of the 2nd phase.

It is generally assumed that the cause of the initial autoignition of individual droplets is the above-mentioned, very unstable peroxide compounds (moloxides)⁴ of the type $C_mH_nO_x$, stable only within very narrow limits of temperature and pressure and rapidly decomposing outside these limits with considerable evolution of heat:

$$ C_mH_nO_x \to xH_2O + C_mH_{n-2x} + Q $$

In the decomposition of the peroxide, the liberated hydrogen atoms, which are very active (in statu nascendi), combine with the oxygen of the air to form $H_2O$. The remaining part of the molecule is an unsaturated hydrocarbon which, owing to the rise in its temperature by the heat $Q$, is activated, reac-

reacts with oxygen, creating a flame front that is the beginning of self-ignition.

Owing to the simultaneous appearance of such flame fronts at different points in the combustion chamber, the prerequisites are created for the transition of the process into the second phase of a violent reaction, accompanied by the release of heat in quantities sufficient for a strong increase in temperature throughout the entire combustion space.

The third phase is the last, concluding the whole process of “visible” combustion. Its course depends mainly on the temperature conditions in the combustion space, the nature of fuel admission, the quality of atomization and mixing, and the rate of the chemical reactions.

The indicator diagrams obtained during the tests—normal, and especially superposed or recorded over time—make it possible to judge the character of the course of the separate phases of the combustion process.

Fig. 15. Indicator diagrams for Dv-lya YuMT.

The diagrams of Fig. 15, obtained when taking indicator readings from the machine tested, indicate a sharp increase in pressure during the second phase of combustion, which is revealed by the steep rise of the curve near the peak of the superposed diagrams.

Knowledge of the moment of fuel delivery (opening of the injector needle), the clearly expressed moment of the beginning of fuel ignition, and the character of the rise of the curve during the second phase of combustion make it possible to compare the course of the combustion process in its separate phases for both grades of fuel.

Counting the time interval, in degrees of crankshaft angle or in seconds, from the moment of opening of the injector needle,

…of the needle up to the moment of the beginning of ignition, we are able to determine the duration of the first phase of combustion, or the period of ignition “delay” (German Zündverzug, English “delay” or “time lag”).

In Fig. 15, at the vertices of the superposed indicator diagrams, the degrees of crank rotation are marked from the upper dead center to the beginning of the second phase (angle \(\alpha\)) and to its end (angle \(\beta\)).

There also are given the numerical values of the pressure jump \(\Delta p\) in atm.

Knowing the moment of opening of the injection needle, which in our case occurred \(4^\circ\) before TDC, one can calculate the duration of the first phase.

The magnitude of the “pressure jump” and the duration of the second phase in degrees, determined by the difference of the angles \((\beta-\alpha)\), make it possible to characterize this phase by the degree of pressure rise per \(1^\circ\) of crank rotation.

In Table VII below these quantities are collected, while the course of the angles \(\alpha\), \(\beta\), \((\beta-\alpha)\), the pressure jump, and the pressure rise per \(1^\circ\) of crank rotation during the 2nd phase,

\[ \frac{\Delta p}{\beta-\alpha}, \]

as a function of engine load when operating on both grades of fuel, is presented in the diagrams of Figs. 16, 17, and 18.

Table VII.

No.	Load in fractions of normal	\(\alpha^\circ\), petroleum motor fuel	\(\alpha^\circ\), sapropel fuel oil	\(\beta^\circ\), petroleum motor fuel	\(\beta^\circ\), sapropel fuel oil	\((\beta-\alpha)^\circ\), petroleum motor fuel	\((\beta-\alpha)^\circ\), sapropel fuel oil	\(\Delta p\), kg/cm², petroleum motor fuel	\(\Delta p\), kg/cm², sapropel fuel oil	\(\dfrac{\Delta p}{(\beta-\alpha)}\), kg/(cm²·degree), petroleum motor fuel	\(\dfrac{\Delta p}{(\beta-\alpha)}\), kg/(cm²·degree), sapropel fuel oil
1	\(0.25\,N_{eн}\)	10.0	10.5	17.0	17.0	7.0	6.5	4.5	3.5	0.64	0.54
2	\(0.50\,N_{eн}\)	7.5	4.0	13.5	10.0	6.0	6.0	7.5	4.7	1.25	0.78
3	\(0.75\,N_{eн}\)	6.0	4.0	14.5	10.0	8.5	6.0	8.5	6.0	1.00	1.00
4	\(1.00\,N_{eн}\)	5.0	2.5	11.5	9.5	6.5	7.0	9.1	7.2	1.40	1.03
5	Maximum overload \( (1.20\) in series \(H—Ne\); \(1.27\) in series \(C—Ne)\)	4.5	3.5	10.0	13.5	5.5	10.0	8.1	8.2	1.47	0.82

The desire to compare petroleum motor fuel and sapropel fuel oil with respect to ignition-delay time led to the need to determine the period from the beginning of the rise of the injection needle, and, consequently, from the beginning of fuel injection into the cylinder, to the beginning of the rise of the pressure line.

Since the beginning of the rise of the injector needle in all experiments corresponded to the position of the crankshaft at \(4^\circ\) before T.D.C., the angle from the beginning of injection to the beginning of self-ignition \(\varphi_s\) will be obtained as the sum

\[ \varphi_s = 4^\circ + \alpha. \]

Fig. 16. Variation of the angles \(\alpha\) and \(\beta\) as a function of \(Ne\).

The values of the angle \(\varphi_s\) are given in Table VIII. The values of the “self-ignition delay,” \(Z_s\), are also calculated there.

The values of the angle \(\varphi_s\) for petroleum motor fuel (see the 6th vertical column of Table VIII), depending on the load, varied from \(14^\circ\) to \(8.5^\circ\) of crankshaft rotation, which corresponds to the limiting values of \(Z_s\) from 0.0097 to 0.0061 seconds.

Accordingly, for sapropelite fuel oil the magnitude of the angle \(\varphi_s\) varied from \(14.5^\circ\) to \(7.5^\circ\), and \(Z_s\) from 0.0101 to 0.0053 sec.

The \(Z_s\) curves plotted in Fig. 18 as a function of \(Ne\) show the character of the variation of this quantity under the different engine conditions.

As is evident from Fig. 18, \(Z_s\), for both one fuel and the other, decreases with increasing load.

Fig. 17. Variation of \(\Delta p\) and \((\beta - \alpha)\) as a function of \(Ne\).

At the same time, the values of the ignition-delay time for the series of experiments with sapropelite fuel oil were smaller, giving a shortening of this period at full load, i.e., under normal operating conditions of the engine, by approximately 27%.

Unfortunately, the absence of any information on the degree of chemical affinity with oxygen, reaction rates, and data on...

Table VIII.

Test No.	Engine power \(N_e\): Petroleum motor fuel	Engine power \(N_e\): Sapropelite fuel oil	Number of revolutions \(n\): Petroleum motor fuel	Number of revolutions \(n\): Sapropelite fuel oil	\(\varphi_s^\circ\): Petroleum motor fuel	\(\varphi_s^\circ\): Sapropelite fuel oil	\(Z_s\), sec.: Petroleum motor fuel	\(Z_s\), sec.: Sapropelite fuel oil
1	3.60	3.78	240	240	14.0	14.5	0.0097	0.0101
2	7.66	7.76	238	239	11.5	8.0	0.0080	0.0056
3	10.85	11.38	237	238	10.0	8.0	0.0070	0.0056
4	15.00	15.14	236	236	9.0	6.5	0.0063	0.0046
5	18.00	19.06	233	236	8.5	7.5	0.0061	0.0053

Fig. 18. Change in the ignition-delay time \(Z_s\) per \(1^\circ\) as a function of load

In the process of preliminary decomposition, under the influence of temperature and pressure, of the components entering into the composition of sapropelite fuel oil, the moment of appearance and the character of the course of the phenomenon of the “cold flame,” and the impossibility of determining experimentally the self-ignition temperature, owing to the absence of suitable apparatus, do not make it possible to establish exactly the causes producing the considerable shortening of the ignition-delay period when operating on sapropelite fuel oil.

It is possible that the cause of the decrease, for sapropelite fuel oil, in \(Z_s\) is the greater homogeneity of the fractional composition and its physicochemical properties, which give grounds to expect a lower temperature for the appearance of the cold flame and, as a consequence of this, a lower self-ignition temperature.

It is also quite probable that the significant content of oxygen compounds in sapropelite fuel oil (see the elemental composition) is one of the factors reducing the ignition delay time.

As shown by the experiments of R. S. Yakovlev on the study of the transition of a cold flame into complete combustion¹, the introduction of pure oxygen into the zone of reactions preceding ignition is “a factor that, to the highest degree, strongly promotes the transition of the cold flame into complete combustion.”

The decomposition of oxygen-containing molecules during the first phase, when the cold flame appears, and the release at that moment of oxygen atoms, may prove to be a powerful agent that substantially accelerates the further course of oxidation and decomposition reactions and promotes a more rapid transition to ignition, reducing the value of \(Z_s\) for sapropelite fuel oil.

Studying the second phase of combustion in the experiments of both series, we note here as well differences in the character of this phase for petroleum and sapropelite fuels.

Indeed, as is seen from Table VII, both the absolute values of the pressure jump and the increase in pressure per \(1^\circ\) of crankshaft rotation were different.

The character of the change in

\[ \frac{\Delta p}{\beta-\alpha} \]

is presented in Fig. 18 as a function of load.

At identical values of the atomizing-air pressure \(p_\phi\) in the corresponding experiments of both series, the different intensity of the pressure rise may be explained by the individual character of the second phase of combustion of the fuels being compared.

The intensity of the combustion of sapropelite fuel oil during this phase is inferior to that for petroleum motor fuel, reaching a maximum at normal load.

The smoother character of combustion in the second phase may be explained by the coarser atomization of sapropelite fuel oil, the rates of the stepwise decomposition reactions of heavy hydrocarbon molecules, the nature of the hydrocarbon compounds constituting the fuel oil, the shorter duration of the first phase of combustion, and the larger excess-air coefficient.

Indeed, with the same atomizing device and the same pressure of the nozzle air, the diameter of the fuel droplets depends on the magnitude of the coefficient of surface tension.

According to Triebnigg¹, the radius of the drops can be calculated by the following formula:

\[ r_1=\frac{2a\cdot g}{\psi\cdot \gamma_{\phi}\cdot w_r^2}\ldots\ldots\ldots\ldots\ldots(10) \]

where:
\(a\)—coefficient of surface tension of the fuel,
\(g\)—acceleration of gravity in \(m/sec^2\),
\(\psi\)—coefficient of friction of the atomized fuel particle against the air,
\(\gamma_{\phi}\)—specific weight of the air at the moment of atomization, taking the temperature of the air entering the working cylinder as \(50^\circ C\), in \(kg/m^3\),
\(w_r\)—relative velocity in \(m/sec\) between the atomizing air and the fuel particles.

In formula (10), \(w_r\) may, without great error, be taken as equal to the theoretical velocity of the outflow of air from the injector at a pressure difference \(p_{\phi}\) and \(p_c\)².

In that case:

\[ w_r=w_1=\sqrt{2gL_{\mathrm{iz.}}}=\sqrt{2g\cdot\frac{p_{\phi}}{\gamma_{\phi}}\ln\frac{p_{\phi}}{p_c}}\ldots\ldots(11) \]

where: \(p_c\)—pressure at the end of compression in the cylinder.

Substituting the value \(w_r=w_1\) from expression (11) into formula (10) and introducing the numerical values of the constant quantities, we obtain:

\[ r_1=25{,}0\cdot\frac{a}{p_{\phi}\cdot \ln\frac{p_{\phi}}{p_c}}\ldots\ldots\ldots\ldots(12) \]

The last formula shows that, with \(p_{\phi}\) and \(p_c\) kept constant, the fineness of atomization of the fuel depends exclusively on the magnitude of the coefficient of surface tension of the fuel.

As for the latter, for petroleums its value varies within comparatively narrow limits, amounting on the average to \(a=0.003\ kg/m^3\).

For other fuels, as Prof. Gurvich⁴ indicates, “in passing from methane hydrocarbons to naphthenes (of course, with the same number of carbon atoms), from these to aromatics, and then to unsaturated compounds, the surface tension in air increases.”

In addition, an increase in surface tension with an increase in the boiling limits of petroleum fractions was observed by Gurvich, Rittman, Egloff, Francis, and Bennett.

On the basis of these indications, it may be assumed that sapropelite fuel oil, containing a larger amount of high-boiling fractions than petroleum motor fuel, and having in its composition aromatics and unsaturated compounds, must possess a higher surface tension.

This gives grounds for concluding that, all other conditions being equal, the atomization of sapropelite fuel oil took place into droplets of larger diameter than in the case of petroleum motor fuel.

From expression (12) it is evident what influence the pressure of the atomizing air has on the quality of atomization.

In operation with both grades of fuel, the pressure of the atomizing air was set at the value most advantageous with respect to fuel consumption on petroleum, on the basis of a series of preliminary experiments, and was not changed when switching to sapropelite fuel oil.

This circumstance, intended to compare the operation of the engine on both fuels under identical conditions, led to coarser atomization of the sapropelite fuel oil and was one of the reasons for the more sluggish course of combustion in the second and third phases of combustion.

According to the existing view of the combustion process, heavy hydrocarbon molecules, before yielding the final oxidation products, \(H_2O\) and \(CO_2\), pass through a whole series of intermediate reactions¹, gradually decomposing into simpler ones; moreover, the length of the stepwise chain will be the greater, the heavier the molecule.

It has been observed that the combustion of aromatic hydrocarbons also proceeds according to an analogous scheme, but of a different structure.

The larger quantity of heavy fractions and the presence of aromatic compounds in sapropelite fuel oil are, therefore, the causes giving rise to a more protracted character of combustion.

The influence of the duration of the first phase on the character of the course of the second is manifested in the fact that the intensity of the pressure rise is greater the longer the ignition-delay period is, since by the moment of ignition a larger portion of fuel will have been injected into the cylinder.

In the case of sapropelite fuel oil, by the beginning of ignition, which occurred earlier than with petroleum motor fuel, there was at that moment a smaller quantity of fuel in the cylinder, which, upon self-ignition, could not cause as sharp an increase in pressure as petroleum fuel.

Finally, a greater or lesser coefficient of excess air cannot fail to exert its influence on such a process as combustion.

¹ F. Sass, Compressorless Diesel Engines. M., 1931, pp. 35 and 38.

As the diagram in Fig. 19 shows, the values of the coefficient of excess air in all experiments of the sapropelite series were higher than in the petroleum series. Owing to this, conditions were present for ensuring a more complete and more rapid course of the combustion process.

The fact of a greater excess of air in identical experiments was an accelerating factor in the combustion process; however, the factors cited above, acting in the opposite direction, proved to be predominant during the second phase.

Fig. 19. Coefficient of excess air and characteristics of combustion products.

As is seen from a comparison of Fig. 19 and the curve of the combustion-line course on the operating diagram at maximum overload in series C—Ne, with the minimum value of \(\alpha\), the combustion process is considerably slowed, with the greater part of it passing into the third phase.

The third phase of combustion in all cases of the sapropelite series proved to be more prolonged in time, which could not but affect the increase in the temperature of the exhaust gases (see Fig. 19), which in this case, as the position of the curve \(t_{\text{exh. g.}}\) shows, lies above the analogous curve for the petroleum series.

The increased temperature of the exhaust gases entailed an increase in the losses with the exhaust gases and with the cooling water (see Fig. 14-b). Nevertheless, a certain increase in the two latter losses does not reduce the economy of the machine, which at normal load proved greater than on petroleum motor fuel, chiefly due to the reduction of losses not directly taken into account by measurement, as a result of the greater completeness of combustion of sapropelite fuel oil, to which the greater value of the coefficient of excess air contributed.

V. Operating characteristics for sapropelite fuel oil.

For completeness of the characterization of the operation of the compressor engine on the new fuel, it is necessary to dwell on several questions of importance for operation.

Starting the engine at room and fuel temperatures close to \(18—20^\circ\text{C}\) is carried out without difficulty.

In the case of operation at lower temperatures it is necessary to heat the fuel tank, with starting

Series N-? — 21.I.32 — 1/4 load
Series S-№ — 16.I.32 — 1/4 load
Series N-? — 21.I.32 — Full load
Series S-№ — 16.I.32 — Full load
Series N-? — 21.I.32 — Overload 20%
Series S-№ — 16.I.32 — Overload 25%

Fig. 20 and 21. Tachograms of the UMT engine when operating on both fuels.

the engine on a more fluid fuel and switching to it before stopping.

Operation at high loads is characterized by increased fuel consumption, reaching an increase of up to 14% at quarter load, as compared with that for petroleum fuel.

Idling and quarter load, as can be seen from the tachograms presented in Figs. 20 and 21, are distinguished by great instability.

This is caused, as the diagrams in Fig. 22 show, by a deterioration of the conditions for the normal course of the combustion process, and sometimes also by misfires.

When operating on sapropelite fuel oil, the overload capacity of the engine increases, owing to the lower value of the theoretically required amount of air for combustion.

During the tests the engine permitted prolonged, stable operation (see the tachogram in Fig. 21), without a reduction in the number of revolutions, at overloads of 25%, which could not be achieved on petroleum motor fuel.

Inspection of the cylinder, piston, valves, and injector after 14 hours of continuous operation at various loads on sapropelite fuel oil showed considerably greater fouling of these engine parts by coke deposits.

Especially heavy accumulation of the latter is noticeable on the injector nozzle.

A series of inspections made after operation at low loads gives grounds to conclude that coke deposition occurs chiefly during engine operation under underload, which is characterized by increased fuel consumption.

Fig. 22. Indicator diagrams of idling and one-quarter load of the UMT engine when operating on sapropelite fuel oil.

The character of carbon formation on the injector nozzle after operation on petroleum and sapropelite fuels is shown in Figs. 23, 24, and 25.

Fig. 23. Clean nozzle of the UMT engine.

Fig. 24. Nozzle of the injector of the UMT engine after 40 h of operation on petroleum motor fuel.

Fig. 25. Nozzle of the injector of the UMT engine after 14 h of operation on sapropelite fuel oil.

The coke obtained from sapropelite fuel oil is looser than that from petroleum motor fuel and is cleaned off more easily.

(To be continued.)

Summary table of the results of comparative testing of the Yu.M.G. engine

No.	Series	Parameter	Symbol / unit	—	H–Ne I	H–Ne II	H–Ne III	H–Ne IV	H–Ne V	C–Ne I	C–Ne II	C–Ne III	C–Ne IV	C–Ne V
1				—	—	—	—	—	—	—	—	—	—	—
2		Test number	—	—	I	II	III	IV	V	I	II	III	IV	V
3		Test date	—	—	21/I 32	21/I 32	21/I 32	21/I 32	21/I 32	6/II 32	6/II 32	16/II 32	16/II 32	16/II 32
4		Beginning of test	h/min	—	10³⁰	12¹⁵	14³⁰	18¹⁵	19⁴⁰	18⁰⁵	19⁵⁰	19¹⁰	17⁴⁵	15⁴⁵
5		End of test	h/min	—	11³⁰	13¹⁵	15³⁰	19¹⁵	20⁴⁰	19⁰⁵	20⁵⁰	20¹⁰	18⁴⁵	16⁴⁵
6		Test duration	h/min	—	1⁰⁰	1⁰⁰	1⁰⁰	1⁰⁰	1⁰⁰	1⁰⁰	1⁰⁰	1⁰⁰	1⁰⁰	1⁰⁰
7		Barometric pressure	\(B\), mm Hg	—	745.1	745.1	745.1	745.1	745.1	760.1	760.1	759.4	759.4	759.4
8		Ambient air temperature	\(t\), °C	—	20	22	20	21	19	20	21	21	20	21
9		Approximate load	—, %	—	0.25	0.50	0.75	1.0	1.2	0.25	0.50	0.75	1.0	1.25
10		Forced-air pressure	\(P_{\varphi}\), ati	—	50	55	60	65	68	50	55	60	60	68
11		Pressure in the cold compressor	\(P_{k}\), ati	—	4.5	5.25	5.30	6.16	6.5	4.75	5.3	5.55	5.45	6.18
12		Number of revolutions per minute	\(n\), rpm	—	240	238	237	236	233	240	239	238	236	236
13		Fuel grade	—	—	Petroleum motor fuel	Petroleum motor fuel	Petroleum motor fuel	Petroleum motor fuel	Petroleum motor fuel	Sapropelite fuel oil	Sapropelite fuel oil	Sapropelite fuel oil	Sapropelite fuel oil	Sapropelite fuel oil
14	Fuel	Higher heating value	\(Q_{b}^{p}\), kcal/kg	—	10640	10640	10640	10640	10640	10060	10060	10060	10060	10060
15	capacity	Lower heating value	\(Q_{H}^{p}\), kcal/kg	—	9960	9960	9960	9960	9960	9520	9520	9520	9520	9520
16	Oil consumption by weight	Hourly	\(G'\), kg/hr	—	1.516	2.09	2.652	3.372	3.891	1.826	2.268	2.786	3.290	4.380
17		Per 1 effective horsepower-hour	\(g_{e}\), g/e.hp.hr	—	423.0	273.0	244.5	225.0	216.3	483.5	292.2	244.8	217.3	229.8
18		Per 1 indicated horsepower-hour	\(g_{i}\), g/i.hp.hr	—	153.8	147.6	154.8	164.6	166.6	172.7	157.1	155.1	148.8	177.0

No.	Group	Quantity	Symbol	Unit	1	2	3	4	5	6	7	8	9	10
19	Power	Effective power	\(N_e\)	hp	3.6	7.66	10.85	15.00	18.00	3.78	7.76	11.38	15.14	19.06
20	Power	Indicated power	\(N_i\)	hp	9.36	14.15	17.14	20.46	23.38	10.57	14.43	17.95	22.1	24.76
21	Power	Mean effective pressure	\(P_e\)	kg/cm²	1.10	2.35	3.45	4.59	5.68	1.15	2.36	3.49	4.68	5.9
22	Power	Mean indicated pressure	\(P_i\)	kg/cm²	3.01	4.34	5.30	6.33	7.32	3.21	4.39	5.5	6.83	7.66
23	Cooling water	Temperature of cooling water at inlet	\(t_1\)	°C	4.5	5.0	4.0	4.0	4.0	4.5	3.0	3.0	2.8	4.0
24	Cooling water	Temperature of cooling water at outlet from the jacket	\(t_2^p\)	°C	37.0	44.2	57.0	53.7	52.3	42.4	46.0	53.3	43.5	55.2
25	Cooling water	Temperature of cooling water at outlet from the heads	\(t_2^r\)	°C	36.0	46.8	54.3	55.0	58.7	44	52.0	52.4	44.0	52.0
26	Cooling water	Heating of water in the jacket	\(\Delta t_p\)	°C	32.5	39.2	53.0	49.7	48.3	37.9	39.0	50.3	40.7	51.2
27	Cooling water	Heating of water in the head	\(\Delta t_r\)	°C	31.5	41.8	50.3	51.0	54.7	39.5	47.5	49.4	41.2	48.0
28	Cooling water	Hourly consumption for the jacket	\(W_p\)	kg/hr	126.5	114.4	94.3	123.5	157.1	114.6	119.6	100.8	190.1	153.2
29	Cooling water	Hourly consumption for the head	\(W_r\)	kg/hr	52.25	49.8	56.5	70.3	81.8	41.6	54.7	62.9	109.3	119.5
30	Cooling water	Total consumption per cylinder	\(W\)	kg/hr	178.75	164.2	150.8	193.8	238.4	156.2	174.3	163.7	299.4	272.7
31	Exhaust gases	Average temperature from the test	\(t_{\mathrm{o.g.}}\)	°C	151.1	204.9	257	321	344	173.4	219	255.1	332.5	358
32	Exhaust gases	Gas analysis	\(RO_2\)	%	2.6	3.8	5.2	7.2	9.2	3.0	4.4	5.3	7.6	9.0
33	Exhaust gases	Gas analysis	\(RO_2 + O_2\)	%	19.9	19.2	19.0	18.6	17.8	19.2	19.1	19.4	18.3	18.4
34	Exhaust gases	Excess-air coefficient	\(\alpha\)	—	5.54	3.88	2.86	2.08	1.65	6.2	4.52	3.22	2.2	1.82

No.	Section	Quantity	Unit	—	H–Ne 1	H–Ne 2	H–Ne 3	H–Ne 4	C–Ne 1	C–Ne 2	C–Ne 3	C–Ne 4	C–Ne 5
35	Coefficients of efficiency	$\eta_e$	%	15,1	23,3	26,0	28,2	29,3	13,7	22,8	27,1	30,6	28,9
36	Coefficients of efficiency	$\eta_i$	%	41,2	42,9	40,9	39	38	38,3	42,3	40,9	44,5	37,5
37	Coefficients of efficiency	$\eta_m$	%	36,5	54,2	63,3	74,1	77,7	35,75	53,80	63,4	68,5	77,0
38	Input	$Q$	cal/hour	15100	20800	26410	33600	38800	17400	21610	26580	31380	41700
39	Input	$Q$	%	100	100	100	100	100	100	100	100	100	100
40	Hourly heat balance of the engine; expenditure	Heat converted into effective work, $Q_e$	cal/hour	2278	4850	6860	9480	11400	2394	4910	7200	9570	12060
41	Hourly heat balance of the engine; expenditure	Heat converted into effective work, $Q_e$	%	15,1	23,3	26,0	28,2	29,3	13,7	22,8	27,1	30,6	28,9
42	Hourly heat balance of the engine; expenditure	Heat carried away by the cooling water, $Q_v$	cal/hour	5750	6560	7840	9730	12060	5985	7260	8170	12250	13590
43	Hourly heat balance of the engine; expenditure	Heat carried away by the cooling water, $Q_v$	%	38,1	31,6	29,7	28,9	31,1	34,4	33,6	30,8	39,1	32,6
44	Hourly heat balance of the engine; expenditure	Heat carried away by the exhaust gases, $Q_{\mathrm{exh}}$	cal/hour	3760	5120	6250	7535	7700	4250	4950	6400	7010	8700
45	Hourly heat balance of the engine; expenditure	Heat carried away by the exhaust gases, $Q_{\mathrm{exh}}$	%	25,0	24,6	23,7	22,4	19,8	24,4	22,9	24,0	22,3	20,8
46	Hourly heat balance of the engine; expenditure	Heat of radiation and other losses, $Q_{\mathrm{res}}$	cal/hour	3312	4270	5460	6865	7640	4770	4490	4810	2550	7350
47	Hourly heat balance of the engine; expenditure	Heat of radiation and other losses, $Q_{\mathrm{res}}$	%	21,8	20,5	20,6	20,5	19,8	27,50	20,7	18,1	8,0	17,7
48	Fuel consumption	Per effective horsepower-hour, $q_e$	cal/e.h.p.-h	4190	*2715	2430	2240	2150	4600	2780	2335	2070	2185
49	Fuel consumption	Per indicated horsepower-hour, $q_i$	cal/i.h.p.-h	1614	1470	1528	1642	1660	1645	1498	1480	1418	1684

1. Triebnigg H. Der Einblase-und Einspritzvorgang bei Dieselmaschinen. Wien, 1925. ↩↩↩↩↩

2. Brilling N. R. Investigation of the Working Process and Heat Transfer in a Diesel Engine. Moscow, 1931. ↩↩↩↩

3. Triebnigg H. p. 17. ↩

4. Gurvich L. G. Scientific Principles of Petroleum Processing, 1925, p. 192. ↩↩

5. Neumann K.—V. D. I. 1932, p. 767. ↩