ON SAVING ELECTRICAL ENERGY BY INCREASING THE EFFICIENCY OF FANS

A. G. BYCHKOV

(Presented by the scientific seminar of the Department of Mining Mechanics)

In connection with the planned program for the development of the national economy of the USSR for 1959–1965, it is advisable to consider the question of the prospects for the development of fan engineering and the economic effectiveness of measures to increase the efficiency of fans.

It should be noted that, with the development of technology and with the increasing requirements for labor protection and for ensuring comfortable conditions in public and residential premises, the relative share of the useful (hydraulic) power of fan installations, in relation to the total electrical power consumed in the national economy, will increase.

Because of the absence of precise information on the number and power of fans installed and operating in the USSR, and of summarized data on their operating regimes, some of the quantities used in the calculations below have been adopted on the basis of general considerations and are approximate. However, in our opinion, the possible inaccuracy of these quantities cannot affect the correctness of the conclusions drawn.

Figure 1 gives curves characterizing the growth of coal and electric-power production in the USSR. This graph is used below in considering the question of the necessary development of fan engineering.

Fig. 1. Growth of coal and electric-power production in the USSR. 1—total coal output; 2—coal output by underground mining; 3—total generation of electric power; 4—generation of electric power at thermal power stations.

Mine fans. In coal mining, a considerable amount of electric power is expended on ventilating underground workings. According to Donuglemash, in 1955 the mines of the USSR had 4,109 main-ventilation fans installed, of which 2,122 were centrifugal and 1,997 axial. In 1960, with the expected output of coal by the underground method of 440 million \(t\) per year, the number of fans should increase to approximately 5,600. In view of the fact that most fan installations have reserve, non-operating fans, it may be assumed that, of the indicated number of fans, about \(55\%\), i.e., 3,100 units, will operate continuously (around the clock).

It is known that for each ton of coal mined, the main-ventilation fans deliver from 3 to 10 \(m\) of air into the mines. If it is assumed that, on average, 6 \(m\) of air is supplied per ton of coal, then in 1960 the total capacity of the main-ventilation fans will be approximately 70,000 \(m^3/sec\).

The pressures produced by these fan installations range from 30 to 450 \(kg/m^2\). Taking the average pressure as 180 \(kg/m^2\), the average operating efficiency of fan installations as 0.55, and the efficiency of electric motors as 0.9, we obtain an average continuously consumed power of the main fans of about 224 thousand \(kW\), and a continuously expended electrical power of about 250 thousand \(kW\).

In addition, in underground workings there operates a large number of portable fans for local (partial) ventilation, whose total power amounts to 25–30% of the power of the main fans.

Thus, the total continuously consumed power of mine fans will be about 330 thousand \(kW\) and, accordingly, the expenditure of electric power for their operation about 2.9 billion \(kW\text{-}h\) per year, which constitutes \(1\%\) of all electric power generated in the USSR. With the cost of electric power at mines being 0.1 ruble/\(kW\text{-}h\), the expenditures for paying for energy will amount to 290 million rubles per year.

From 1960 to 1970 the increase in coal production will occur mainly through an increase in open-pit workings; coal production by the underground method is to grow by only 10%. Therefore, a substantial increase in the average operating efficiency of mine fans is possible mainly through measures to improve the economy of operation of existing installations with old-type fans.

Taking into account the need for further improvement of mine ventilation, as well as the circumstance that in open-pit mining, in some cases, special fans will be required for removing dust and gases from poorly ventilated zones of open pits, it may be assumed that by 1970 the power consumed by fans will increase by approximately 20%.

In the further calculations (Table 1), the possible saving of electric power through increasing the efficiency of mine fans is taken as equal to \(3\%\).

Draft-and-blast machines of thermal power stations. At present, at thermal power stations, about \(3\%\) of all electric power generated by these stations is expended on the operation of draft-and-blast machines (smoke exhausters and forced-draft fans). At new large thermal power stations this energy consumption can apparently be reduced to approximately \(2.5\%\) by decreasing the resistance of the air and gas ducts of boiler units.

In 1960, the year of the average, the continuously consumed electric power of draft-and-blower machines will be about 820 thousand kW, and the consumption of electric energy 7.2 billion kWh, i.e., about 2.5% of all electric energy generated in the country. The expenditures on electric energy consumed by draft-and-blower machines, at its cost at stations of 0.1 ruble/kWh, will be about 720 million rubles per year.

If it is assumed that at new stations machines will be installed having the same efficiencies as those currently manufactured (maximum overall efficiencies 0.7), then by 1969 the consumption of electric energy will increase to 15.8 billion kWh per year, and the total consumption over 10 years will be about 115 billion kWh. Taking the average cost of electric energy at thermal power stations over these years as 0.07 ruble/kWh, we obtain that the average annual expenditures on electric energy for draft-and-blower machines will be about 800 million rubles per year.

In recent years the Moscow branch of TsKTI, ORGRES, and TsAGI have developed aerodynamic designs of centrifugal machines that have maximum efficiencies of 0.85–0.87. Raising the efficiency from 0.7 to 0.85 gives a reduction in consumed power of 17.5%. However, when the output of fans is regulated by guide-vane devices, the power saving decreases. Therefore it may be assumed that the saving of electric energy due to increasing the average operating efficiency of the new machines will be about 10%.

If it is assumed that the new machines will be used at all new electric power stations beginning in 1961, then over the period 1961–1969 about 4.3 billion kWh will be saved, or, at an energy cost of 0.07 ruble/kWh, an average of 33.5 million rubles per year.

Other special-purpose fans. In addition to the two categories of fans considered, the national economy uses mine fans, employed in various branches of the mining industry, and other special-purpose fans (for cement kilns, grain dryers, metropolitan railway stations, etc.), for which we have no data for substantiated quantitative estimates.

It is assumed below that, in the overall balance of electric-energy consumption, the share of these fans is about 9%, and that the saving due to the use of new types of these machines will be about 4% of the total electric-energy consumption for fans of this category.

General-purpose fans. General-purpose fans include centrifugal and axial fans manufactured by plants as standard products and used for sanitary-technical and various production purposes (GOST 5976-55). Carrying out analogous calculations for this category of fans is very difficult because of the absence of data on the number of fans installed at consumers and on their operating conditions, and also because of the large number of their types and sizes. The increase in the output of these fans by plants in recent years is shown in Fig. 2.

It should be noted that, with electric-energy production increasing from 1950 to 1960 by a factor of 3.27, fan output increases by a factor of 3.4, i.e., somewhat more. Such a dependence should be considered quite natural, since the need for and the possibility of using fans is determined by the availability of electric energy. This dependence, in our opinion, can be used to determine the demand for general-purpose fans in the coming years.

Starting from the number of fans produced by plants during the pos-

over the course of 10 years, it may be assumed that the total number of fans installed at consumers’ sites in 1960 will be on the order of 1.2 million units (corresponding to an average age of the fans at consumers’ sites of about 6.5 years). Taking into account that approximately 20% of these fans, for various reasons, are not operating, in the subsequent calculations we take the number of fans operating in 1960 to be equal to 960 thousand units.

By 1970 the number of fans installed at consumers’ sites should increase approximately threefold, i.e., to 3.6 million units, while their production by plants should increase by more than a factor of 3. In 1969 the number of fans produced by plants will apparently have to be on the order of 600 thousand units (Fig. 2).

Fig. 2. Production of general-purpose fans.
1—total number of fans; 2—number of fans with high efficiency.

According to the available data, of the total number of fans produced by plants in recent years, about 80% are centrifugal fans and about 20% are axial fans.

In recent years the plants have chiefly produced centrifugal fans of low and medium pressure of the following types: VR (including EVR electric fans), VRS, VRN, Ts9-55, Ts9-57 (STD-TsAGI), “Sirokko,” and TsP6-46 (“TsAGI dust fans”). In addition, a relatively small number of high-pressure fans of various types has been produced. These fans are not considered separately and are included in the total number of fans indicated below. At present, at the Kryukov and Kharkov plants preparations are under way for the production of TsAGI fans of type Ts4-70 [1, 2, 3].

Figure 3 shows the distribution of the sizes (numbers) of fans produced in 1958 and adopted in the calculations for 1960. In order to simplify the calculations, some intermediate numbers have been excluded and the corresponding quantities of fans assigned to the nearest larger number.

The total power consumed by fans may be estimated approximately as follows. The power consumed by a fan may be expressed in the following form:

\[ N=\frac{QH}{102\eta}=\frac{0.0312}{\eta}\,\mathcal{E}H\sqrt{H}\,D^{2}; \]

where

\[ \begin{aligned} Q&\text{—capacity in } \mathrm{m^{3}/sec};\\ H&\text{—total pressure produced, in } \mathrm{kg/m^{2}};\\ \eta&\text{—total efficiency of the fan.} \end{aligned} \]

\(D\) — diameter of the impeller, in m;

\[ \mathcal{E}=\frac{Q}{\sqrt{2H}} \]

— relative equivalent opening of the fan;

\(\overline{Q}\) and \(\overline{H}\) — coefficients of the fan capacity and pressure.

If, for low-pressure centrifugal fans, the average pressure is taken as \(60\ \mathrm{kg}/\mathrm{m}^{2}\) and their number as 80% of the total, and for medium- and high-pressure fans as \(150\ \mathrm{kg}/\mathrm{m}^{2}\) and their number as 20%, then for centrifugal fans we obtain the average pressure at which the fans operate as equal to \(78\ \mathrm{kg}/\mathrm{m}^{2}\). Taking into account that, for centrifugal fans of the indicated types, the relative equivalent opening is on average equal to 0.26, their average operating efficiency is 0.53, and the efficiency of the electric motors and transmissions from them to the fans is 0.8, one may calculate the power consumed by the fans and the electric power consumed from the network.

The general-purpose axial fans produced by our factories, of types MTs, D, and U, have total maximum efficiencies of about 0.6 and are intended for operation at pressures of \(5\text{--}30\ \mathrm{kg}/\mathrm{m}^{2}\).

Taking for these fans an average relative equivalent opening of 0.45, an average operating efficiency of 0.55, and an average pressure at which the fans operate of \(15\ \mathrm{kg}/\mathrm{m}^{2}\), and allowing for the fact that their number is four times smaller than that of centrifugal fans, we find that the total power they consume will be of the order of 4–5% of the power consumed by centrifugal fans. The cost of axial fans is also significantly lower than that of centrifugal fans. Therefore, in approximate calculations, axial fans may be taken into account by increasing the total power by 5% and the cost of centrifugal fans by 10%.

Fig. 3. Estimated output of centrifugal fans in 1960. 1 — number of fans produced in 1958 (total 122 thousand units); 2 — estimated output of fans in 1960 (total 160 thousand units).

In calculating the amount and cost of the electric power consumed by fans, we adopted an average number of fan operating hours of 3000 hours per year and an energy cost of 0.15 rubles/kWh.

For the total number of fans operating in 1960 (960,000 units), we obtain: total electric power consumed from the network, 3.8 million kW; electric-power consumption, about 11.3 billion kWh per year (which amounts to 3.85% of all generated electric power); average continuously consumed electric power, 1.3 million kW; expenses for payment for electric power, about 1.7 billion rubles per year.

It is extremely regrettable that a significant portion of this electric energy, on the order of 25%, is wasted solely because our plants produce very obsolete types of fans, which have low efficiency. If measures are not taken immediately to increase the efficiency of the fans being manufactured, the indicated consumption of electric energy will increase 2.5-fold by 1969.

In 1956–58, TsAGI developed designs for centrifugal fans, of which the simplest have efficiencies of 0.78–0.8. In fans with profiled blades, the maximum efficiency reaches 0.85 [1, 2, 3]. In 1959 the Kriukov and Kharkov plants should begin production of Ts4-70 fans, having an efficiency of 0.8. Raising the efficiency from 0.6 to 0.8 will reduce the power consumed by fans by 25%.

Let us assume that, beginning in 1959, the plants will start producing fans with an efficiency of 0.8, and that their number will gradually increase (Fig. 4) and, having reached 80% by 1965, will remain at this same level in subsequent years. On the basis of these assumptions, the total saving over 10 years (1960–1969) is obtained as approximately 24 billion kWh, or, at the present cost of electric energy, 3.64 billion rubles. Taking into account the reduction in the cost of electric energy, it may be assumed that the saving will average about 260 million rubles per year.

Fig. 4. Assumed growth in the number of fans among consumers.
1—total number of fans; 2—number of fans in operation; 3—number of new operating fans with high efficiency.

An additional source of savings is the reduction in the power and cost of the electric motors of fan installations. When new fans are used, the installed power of the electric motors will be reduced by approximately 40% (25% owing to the increase in efficiency and 15% owing to the reduction of power reserves), while the cost of the electric motors will decrease by approximately 470 million rubles.

At the same time, the cost of fans of the new types will increase somewhat, but nevertheless the total cost of fan installations should decrease, which will yield an additional saving of about 20 million rubles per year. Consequently, the total saving will average about 280 million rubles per year. Thus, with the introduction into production of new types of fans, not only a substantial reduction in operating expenses will be obtained, but also a reduction in the initial cost of fan installations.

On measures for improving fan construction. According to the calculations made, it is found that for the operation of fans of the above-mentioned categories in 1960 more than 23 billion kWh will be expended, i.e., about 8% of the total amount of electric energy generated.

energy (general-purpose fans—3.8%, induced-draft and forced-draft machines—2.5%, mine fans—1%, others—0.7%).

The estimated expenditures and possible savings of electrical energy for the period 1960–69 due to an increase in the efficiency of fans are given in Table 1, where \(W\) and \(W'\) are the expenditures of electrical energy at the former and increased fan efficiency.

Table 1

Savings of electrical energy on the average of the order of 3 billion kWh per year correspond to the amount of electrical energy generated by a power station with a capacity of about 625 thousand kW. Thus, it follows that, by organizing the production of modern types of fans, a power station of the indicated capacity can be freed for useful use.

General-purpose fans consume more than 50% of the electrical energy consumed by all fans. In second place are induced-draft and forced-draft machines; in third and fourth place are mine fans and other special-purpose fans.

In terms of power consumed, the share of centrifugal fans is about 90% (95% for general-purpose fans, 100% for induced-draft and forced-draft machines, 30–35% for mine fans, and 70% for the others). Thus, savings of electrical energy can be obtained mainly by improving centrifugal fans and increasing the efficiency of general-purpose fans.

The tasks of developing and producing new induced-draft and forced-draft machines, mine, mining, and other special-purpose fans can apparently be successfully solved by the organizations and plants serving the interested branches of industry.

The situation with general-purpose fans is very poor, since the numerous plants producing these fans, in terms of their equipment and organization of production, do not meet modern requirements and in practice, without any control, manufacture highly obsolete types of fans that do not satisfy the requirements of GOST 5976—55.

To improve the state of affairs in this principal branch of fan manufacture, it is necessary:

1. To create a body in charge of fan-manufacture issues and responsible for its condition (for example, a group within the State Scientific and Technical Committee of the RSFSR).

2. To organize a special design bureau for general-purpose fans and allocate a production base for manufacturing and testing new fan prototypes.

3. To resume publication of the journal Heating and Ventilation, ensure the publication of new literature on fans, and obtain information on advanced foreign technology.

1. And, most importantly, by reconstructing existing plants and building new ones, ensure the production of modern high-quality fans in the quantity required for the national economy of the USSR.

The reorganization of fan manufacturing will require the corresponding capital investments, which can be estimated approximately from the value of the output produced.

At present, the existing fixed production assets of plants producing fans are considerably smaller than required. For the further development of fan manufacturing, it will apparently be possible to use the production base of only a few main plants, with a total value on the order of 30–40 million rubles. Taking into account that capital investments must be made 2–3 years in advance, it may be assumed that about 170 million rubles must be invested in the fixed production assets of the fan industry during 1959–65. Including capital investments in basic nonproduction assets, total capital investments should be on the order of 250 million rubles, or, on average, about 36 million rubles per year. The allocation of the funds necessary for this purpose can be made at the expense of the interested branches of industry.

It should be especially noted that these capital investments are highly economically effective and will be rapidly recovered. If the anticipated savings are obtained with the above-mentioned capital investments, then already in 1962 these savings will exceed the capital investments, and in 1965 the net savings will be on the order of 600 million rubles.

The reorganization of fan manufacturing is absolutely unavoidable; therefore it must be carried out in the shortest possible time, since delay in resolving this question will only lead to large losses of national funds.

References

1. Bychkov A. G., Mazmanyants P. O. New types of TsAGI centrifugal fans. Water Supply and Sanitary Engineering, No. 9, 1957.

2. Bychkov A. G., Lokshin I. L., Mazmanyants P. O. Designs of centrifugal fans developed by TsAGI in 1957–58. Water Supply and Sanitary Engineering, No. 1, 1959.

3. Bychkov A. G., Lokshin I. L., Mazmanyants P. O. New types of TsAGI centrifugal fans. Industrial Aerodynamics, collection No. 12, Oborongiz, 1959.