Study of Operating Modes of a Pressure Booster
Abstract Generated abstract
This paper investigates the use of a stationary pressure booster for measuring velocity head when flow through a channel can occur in either direction, as in multichannel systems with changing operating conditions. Experiments in an aerodynamic stand measured pressure differences at the throat, diffuser openings, and a total-pressure tube for two booster orientations over air velocities from about 4.45 to 16.5 m/s. The results show that the relationship between selected pressure differences can indicate flow direction, and that in reverse-flow operation the pressure difference between diffuser opening 9 and the throat can be calibrated to determine velocity head, although with a lower amplification coefficient than in the usual orientation. The study also finds that, in reverse operation, opening 9 effectively functions like a total-head tube.
Full Text
STUDY OF OPERATING MODES OF A PRESSURE BOOSTER
V. A. Bragin, B. F. Kalugin, I. N. Konovalov
(Presented by the scientific seminar of the Department of TEE)
In a number of cases it is necessary to use stationary pressure boosters to determine the velocity head of a working-fluid flow when the flow passes over them in the forward and reverse directions. Such a need arises, for example, when testing multichannel systems in which, under different operating conditions, the flow in individual channels may change the direction of its motion.
The stationary pressure booster investigated was made according to the type described in [1]. A longitudinal section of the booster and its principal dimensions are shown in Fig. 1. The layout of the test stand is shown in Fig. 2. In these figures the following are denoted: 1—confuser of the aerodynamic
Fig. 1.
tube; 2—chamber; 3—diffuser of the aerodynamic tube; 4—stationary pressure booster; 5—total-pressure tube; 6—tube for sampling the pressure impulse from the throat of the booster; 7, 8, 9, and 10—openings for sampling pressure impulses along the length of the diffuser part of the pressure booster; 11—adjusting ring of the pressure booster; 12—battery micromanometer; 13—coordinate device; 14—connecting hoses. The diagram (Fig. 2) shows the installation of the pressure booster
with the diffuser part facing the oncoming flow. This operating mode of the pressure booster (we shall designate it as mode I) is the usual one and is widely covered in the literature [1, 2, etc.]. As indicated above, such modes are possible when the pressure booster is turned with the regulating ring 11 facing the oncoming flow. We shall designate this operating mode of the booster by the numeral II. In the chamber
Fig. 2.
2 of the stand, the pressure booster 4 and the total-head tube 5 are secured by means of a special coordinate device 13, by which the booster and the total-head tube can simultaneously be turned through 180°, that is, operating modes I and II of the booster can be created.
In conducting experiments in modes I and II, the change was studied in the difference between the pressure in the total-head tube and the pressure in the throat of the pressure booster, \(\Delta P_{5-6}\), and in the differences between the pressures measured in openings 7, 8, 9, 10 and the pressure in the throat of the pressure booster, \(\Delta P_{7-6}\), \(\Delta P_{8-6}\), \(\Delta P_{9-6}\), \(\Delta p_{10-6}\). The experiments were carried out at velocities of the oncoming air flow ranging from 4.45 to 16.5 m/sec. The results of measurements of the indicated pressure differences in operating modes I and II of the booster at an oncoming air-flow velocity of 4.45 m/sec are given in Table 1. It is evident from the table that, in operating mode II of the pressure booster, the pressure differences \(\Delta P_{7-6}\), \(\Delta P_{8-6}\), \(\Delta P_{9-6}\), \(\Delta p_{10-6}\) are greater than \(\Delta P_{5-6}\). The largest value is attained by the pressure difference \(\Delta P_{10-6}\), but, structurally, taking the pressure at point 10 (Fig. 1) is difficult to accomplish, since in this case it is impossible to use the regulating
ring. From a design standpoint it is simpler to take the pressure at point 9. In this case, as is seen from Table 1, \(\Delta P_{9-6}\) differs little from \(\Delta P_{10-6}\). For the case under consideration, the amplifier coefficient \(K_1\) in mode I, determined by the ratio \(\Delta P_{5-6}\) to \(h_{\text{dyn}}\), is equal to 4.27. Here \(h_{\text{dyn}}\) is the actual velocity head. The point corresponding to this mode lies on the ascending branch of the curve \(K^{\mathrm{I}} = f(Re)\) [2]. For mode II, the ratio \(\Delta P_{9-6}\) to \(h_{\text{dyn}}\) will subsequently be considered the amplification coefficient in operating mode II. Let us denote it by
Table 1
| Pressure difference, mm water column | Amplifier operating mode: 1 | Amplifier operating mode: 2 | Note |
|---|---|---|---|
| \(\Delta p_{5-6}\) | 28.25 | 1.50 | The values \(\Delta p_{7-6}\), \(\Delta p_{8-6}\), \(\Delta p_{9-6}\), and \(\Delta p_{10-6}\) were determined on the inclined scale. To account for the inclination of the scale, the values given must be multiplied by 0.2. |
| \(\Delta p_{7-6}\) | 1.00 | 3.50 | The values \(\Delta p_{7-6}\), \(\Delta p_{8-6}\), \(\Delta p_{9-6}\), and \(\Delta p_{10-6}\) were determined on the inclined scale. To account for the inclination of the scale, the values given must be multiplied by 0.2. |
| \(\Delta p_{8-6}\) | 14.00 | 8.40 | The values \(\Delta p_{7-6}\), \(\Delta p_{8-6}\), \(\Delta p_{9-6}\), and \(\Delta p_{10-6}\) were determined on the inclined scale. To account for the inclination of the scale, the values given must be multiplied by 0.2. |
| \(\Delta p_{9-6}\) | 16.00 | 10.00 | The values \(\Delta p_{7-6}\), \(\Delta p_{8-6}\), \(\Delta p_{9-6}\), and \(\Delta p_{10-6}\) were determined on the inclined scale. To account for the inclination of the scale, the values given must be multiplied by 0.2. |
| \(\Delta p_{10-6}\) | 18.00 | 10.70 | The values \(\Delta p_{7-6}\), \(\Delta p_{8-6}\), \(\Delta p_{9-6}\), and \(\Delta p_{10-6}\) were determined on the inclined scale. To account for the inclination of the scale, the values given must be multiplied by 0.2. |
\(K_{\mathrm{II}}\). In the case under consideration \(K_{\mathrm{II}} = 1.52\), while the ratio of \(\Delta p_{5-6}\) to \(h_{\text{dyn}}\) is less than unity. The change in the pressure differences \(\Delta p_{9-6}\) and \(\Delta p_{5-6}\), as well as in the amplification coefficients \(K_{\mathrm{I}}\) and \(K_{\mathrm{II}}\), was found at several velocities of the incident air flow. The results of the investigation are presented in Table 2.
Analyzing the data of Tables 1 and 2, the following conclusions can be drawn. From the relationship between the values \(\Delta P_{9-6}\) and \(\Delta P_{5-6}\), one can judge the direction
Table 2
| Pressure difference, mm water column | Amplifier operating mode: I | Amplifier operating mode: II | \(h_{\text{dyn}}\), mm water column | \(w\), m/s | Amplification coefficient \(\kappa_{\mathrm{I}}\) | Amplification coefficient \(\kappa_{\mathrm{II}}\) |
|---|---|---|---|---|---|---|
| \(\Delta p_{5-6}\) | 7.70 | 0.46 | 1.80 | 5.440 | 4.275 | 1.390 |
| \(\Delta p_{9-6}\) | 4.80 | 2.50 | 1.80 | 5.440 | 4.275 | 1.390 |
| \(\Delta p_{5-6}\) | 30.60 | 2.50 | 5.70 | 9.825 | 5.375 | 1.718 |
| \(\Delta p_{9-6}\) | 21.20 | 9.80 | 5.70 | 9.825 | 5.375 | 1.718 |
| \(\Delta p_{5-6}\) | 93.00 | 7.50 | 16.00 | 16.400 | 5.810 | 1.910 |
| \(\Delta p_{9-6}\) | 64.8 | 30.60 | 16.00 | 16.400 | 5.810 | 1.910 |
of motion of the working-medium flow in the channel in which the pressure amplifier is installed. In this case the pressure amplifier may be installed stationarily. In those cases where the direction of motion of the working-medium flow in the channel changes and mode II arises, a stationary pressure amplifier with openings 5, 6, and 9 for taking off the pressure impulse—
of pressure is also, to a certain extent, an amplifier of velocity head. True, in this case its amplification factor \(K_{\mathrm{II}}\) is smaller than \(K_{\mathrm{I}}\) in operating mode I. In operating mode II, with appropriate calibration, the pressure booster can be used to determine \(h_{\text{dyn}}\) from the known \(\Delta P_{9-6}\) and \(K_{\mathrm{II}}\). In addition, in mode II a comparison was made between \(\Delta P_{9-6}\) and the difference between the pressure measured by an additionally installed total-head tube (directed against the flow) and the pressure in the throat of the pressure booster. The investigations showed that \(\Delta P_{9-6}\) and the indicated pressure difference are practically indistinguishable. This means that orifice 9 in the diffuser section of the stationary pressure booster, in operating mode II, plays the role of a total-head tube.
REFERENCES
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B. V. Dyadyakin, Z. I. Katasonova. A Venturi tube for measuring small flow rates and velocities in large-diameter pipelines. Teploenergetika, 1965, No. 12.
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P. P. Kremlevskii. Flowmeters. Mashgiz, 1963.