1、NASA TECHNICAL I n NOTE LOAN A KIRTI NAS e,/ COP LFWL ,AND NONCAVITATING AND CAVITATING PERFORMANCE OF SEVERAL LOW AREA RATIO WATER JET PUMPS HAVING THROAT LENGTHS OF 3.54 DIAMETERS by Nelson L. Sunger Lewis Research Center Cleuelund, Ohio A TN D-5095 - - Y: RETURN 1 ( w LI L-2) AFB, N MU NATIONAL A
2、ERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. MARCH 1969 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NM I 111111 11111 11111 lllll lllll lllll lllll Ill1 Ill1 NONCAVITATING AND CAVITATING PERFORMANCE OF SEVERAL LOW AREA
3、 RATIO WATER JET PUMPS HAVING THROAT LENGTHS OF 3.54 DIAMETERS By Nelson L. Sanger Lewis Research Center Cleveland, Ohio NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sole by the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151 - CFSTI price $3.00 -_ Pro
4、vided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ABSTRACT Performance of several jet pumps was determined for pumps having diffuser in- The throat length was found to be too short to cluded angles of 2.5 and 6 over a range of spacings of the nozzle exit
5、from the throat entrance of 0 to 3.0 throat diameters. permit matching with a conventional diffuser (6 included angle) because significant mixing continued into the diffuser entrance. However, due to the low rate of diffusion the pump having the 2.5 diffuser achieved the relatively high efficiencies
6、 of 31.5 per- cent for a nozzle-to-throat area ratio of 0.066, and 38.7 percent for an area ratio of 0.197. ii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I CONTENTS Page SUMMARY . 1 INTRODUCTION 2 PERFORMANCE ANALYSIS . 3 Principle of Operation
7、. 3 Assumptions . 4 Basic parameters 4 Noncavitation analysis 4 Cavitation analysis 5 Analyses 4 APPARATUS AND PROCEDURE . 5 Apparatus 8 Test facility . 8 Instrumentation 8 Experimental Procedure 9 TestPump . 5 RESULTS AND DISCUSSSION . 11 Noncavitation Performance . 11 Efficiency and head rise . 11
8、 Best efficiency nozzle position 11 Comparison of theory with experiments 13 Effect of flow ratio 15 Effect of nozzle spacing and diffuser angle . 15 Effect of throat length 19 Cavitation Performance 22 . SUMMARY OF RESULTS . 24 A PPENDME S A.SYMBOLS 27 B . DETERMINATION OF FRICTION LOSS COEFFICIENT
9、S . 29 REFERENCES . 31 iii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NONCAVITATING AND CAVITATING PERFORMANCE OF SEVERAL LOW AREA RATIO WATER JET PUMPS HAVING THROAT LENGTHS OF 3.54 DIAMETERS by Nelson L. Sanger Lewis Research Center SUMMARY Th
10、e noncavitating and cavitating performance of several jet pumps having throat lengths of 3.54 diameters and diffuser included angles of 2.5 and 6 were evaluated in a water facility for four nozzle-to-throat area ratios ranging between 0.066 and 0.197. Area ratio was varied by using different nozzles
11、. Spacing of the nozzle exit from the throat entrance was varied from 0 to 3.0 throat diameters. Deaerated, room- temperature tap water was used as test fluid. Objectives of the investigation were: to experimentally determine overall non- cavitating and cavitating performance; to study the mixing ch
12、aracteristics over a wide range of geometrical and flow conditions; to compare the experimental results with those obtained for previously investigated configurations having longer throat lengths; and to compare the overall experimental performance to noncavitating and cavitating theoretically predi
13、cted performance. The highest efficiencies were achieved in the pump having the 2.5 diffuser included angle; 31.5 percent was achieved for an area ratio of 0.066 and 38.7 percent for an area ratio of 0.197. The throat length of 3.54 throat diameters was found to be too short to allow matching with c
14、onventional diffusers (approximately 6 included angle) because mixing was incomplete at the diffuser entrance. However, when the short throat was matched with the 2.5 diffuser jet pump efficiency was not penalized because the low rate of diffusion permitted mixing to continue efficiently in the upst
15、ream portion of the diffuser; but the small diffuser outlet area of the 2.5 diffuser did not permit high static pressures to be recovered. The noncavitating analysis did not predict jet pump efficiency and head ratio within an acceptable range of accuracy. This was probably due to the mixing which c
16、ontinued into the diffuser. However, the cavitation analysis, which does not depend on mixing characteristics, predicted the conditions at head-rise deterioration within about 10 per- cent for the various geometric conditions investigated. Provided by IHSNot for ResaleNo reproduction or networking p
17、ermitted without license from IHS-,-,-INT RO DU CTl ON One means of supplying large quantities of continuous, on-board electric power for space vehicles is the use of a Rankine cycle system using liquid metal as the working fluid (refs. 1 and 2). In such systems the condensate return pump must conti
18、nuously pump fluid at near saturation conditions to the high pressure environment of the boiler. To suppress cavitation in the main condensate return pump the jet pump has been selected (ref. 2) as one possible auxiliary boost pump. Its cavitation resistance, sim- plicity, and reliability make it we
19、ll-suited for long-term space applications. The combination of high boiler pressure and low condenser pressure leads to the selection of jet pumps having low ratios of nozzle exit area-to-throat area (area ratio R). The lack of detailed information on jet pumps in this geometrical category provided
20、the impetus for a program of research on the noncavitating and cavitating performance of low area ratio jet pumps. for two area ratios, R = 0.066 and 0.197. Nozzle spacing was the principal geometric variable investigated, and particular attention was paid to the mixing characteristics in the pump.
21、Measured values of efficiency and head ratio correlated closely with values predicted by a one-dimensional analysis. In reference 4 cavitation performance was examined in detail for the same pumps reported in reference 3. A theoretically-derived cavitation parameter provided good correlation between
22、 predicted and measured flow conditions at the point of head-rise deterioration for both area ratios, and over a wide range of nozzle positions. same two area ratios (R = 0.066 and 0.197). The same good correlation of noncavitating and cavitating results with the respective analyses was observed. Fu
23、rthermore, the re- duction in throat length resulted in an improvement in maximum efficiency values at practically every nozzle position. plants, jet pumps of short length are of interest. In the present investigation, jet pumps having throat lengths of 3.54 throat diameters were evaluated. Two test
24、 sections were utilized, differing only in diffuser configurations (included angles of 2.5 and 6). Ex- perimental results from each test section were compared directly to determine the effect of diffuser angle. Results were also compared directly with data from references 3 to 5 to evaluate the effe
25、ct of throat length. The analysis for noncavitating flow developed in reference 3 and the cavitation prediction parameter developed in reference 4 were ap- plied to the configurations and flow conditions investigated as a further test of their ap- plicability. Both test sections evaluated were const
26、ructed with a circular bellmouth entry and a constant diameter throat having a length of 3. 54 diameters. In both cases, the diffusers 2 In reference 3 a jet pump having a relatively long throat (7.25 diam.) was investigated In reference 5 a shorter throat length (5 .66 diam.) pump was investigated
27、for the Because of the need for minimization of weight and size in space electric power- . , , Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-were the same length but differed in diffuser included angle (2.5 against 6.0). Four nozzles, corresponding
28、 to area ratios of 0.066, 0.108, 0.141, and 0.197, were used in the test section having a 2.5 diffuser included angle. Two nozzles, corresponding to area ratios of 0.066 and 0.197, were used in the other test section with the 6 diffuser. Spacing of the nozzle exit from the throat entrance was varied
29、 between 0 and 3.04 throat diameters. Room-temperature, deaerated tap water was used as test fluid. Primary flow rates varied from 28 to 83 gallons per minute (1. 77lO- to 5.2410- m3/sec) and secondary flow rates from 32 to 185 gallons per minute (2.02X10- to 11. 68X10-3 m3/sec). 3 PER FORMA NC E A
30、NALY S 1 S Principle of Operation A schematic representation of a jet pump is shown in figure 1 and the symbols and nomenclature are presented in appendix A. The principle of operation of a jet pump is the transfer of energy and momentum from the high velocity primary fluid to the pumped, or seconda
31、ry fluid, through a process of turbulent mixing. Secondary fluid CD-9399 I IQ2 I Figure 1. - Schematic reJresentation of jet pump. The primary fluid is pressurized by an independent source and is accelerated to high velocity in the nozzle. The secondary fluid is entrained by and mixed with the pri-
32、mary fluid in the throat or mixing section. The mixed fluids then pass through the dif- fuser in which a portion of the kinetic energy (velocity head) is converted to potential energy (static pressure). The primary fluid leaves the nozzle as a core of high velocity fluid. It is separated from the se
33、condary stream by a thin region of high shear. Turbulent mixing between the 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. two fluids occurs in the mixing or shear region which grows in thickness with increasing axial distance. The lowest local
34、pressures occur in the shear region (ref. 6) and there- fore cavitation inception also takes place in this region. Analyses One-dimensional analyses of the noncavitating and cavitating analyses flows are pre- sented in references 3 and 4. Confined-jet mixing analyses (refs. 7 and 8) are not suffi- c
35、iently developed so that an easily applied jet pump design procedure can be derived. Thus the one-dimensional analyses are generally used; but they must be supplemented by empirical information to determine optimum throat lengths, nozzle positions, diffuser geometry and area ratios for specific appl
36、ications. Assumptions. - The assumptions that are common to both the noncavitating and cavi- tating analyses are: (1) Both the primary and secondary fluids are incompressible. (2) The temperature of the primary and secondary fluids are equal. (3) Nozzle spacing from the throat entrance is zero. (4)
37、Nozzle wall thickness is zero. (5) An additional assumption is used in the noncavitating analysis; namely, that mix- Basic parameters. - There are four fundamental jet pump parameters, all ex- (1) Nozzle to throat area ratio, R = An/At (2) Secondary to primary flow ratio, M = Q2/Q1 (3) Head ratio, N
38、 = (H5 - H2)/(H1 - H5) (4) Efficiency, q = MN the equivalent of net output power divided by net input power A parameter that is useful in the study and comparison of axial static pressure vari- ing is complete at the throat exit. pressed in dimensionless form. These parameters are: ation in constant
39、 diameter jet pumps is the pressure coefficient C defined by P px - p2 c= P v: Y- Noncavitation - analysis. - - The noncavitation analysis is presented in detail in appen- dix B of reference 3 (Conventional Analysis). It consists of a one-dimensional applica- tion of the continuity, momentum, and en
40、ergy relations across the individual components of the pump. Friction losses are taken into account with friction loss coefficients K 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-which are based upon total pressure losses in individual component
41、s of the pump, such as the primary nozzle, throat, and diffuser. The formula for head ratio N resulting from the analysis is 22 2R+2RM - 1-R N= 2 2 R2M2 (1 + Ks) n R (1 + M) (1 + %+ Kd) - (1 - R)L -. 22 2 2 1+$-2R- 2R + R (1 + M) (1 + $+ Kd) 1-R Determination of the various loss coefficient values i
42、s discussed in appendix B. conditions at the cavitation-induced total-head breakdown point, rather than to inception conditions. Cavitation analysis. - The cavitation analysis (appendix B, ref. 4) applies to the The analysis consists of an application of the continuity and energy relations to the se
43、condary fluid. Combined with this is the assumption that at the point where the total head falls off the static pressure in the plane of the primary nozzle exit (and throat en- trance) is equivalent to the vapor pressure of the fluid. expression for the cavitation prediction parameter is The resulti
44、ng nondimensional w= - pv = (:y (1 + Ks) (at total head-rise dropoff) 2 vn Y- (:y v* y- APPARATUS AND PROCEDURE Test Pump The test pump (fig. 2) consisted of the following elements: the primary nozzle, the secondary plenum, nozzle spacing shims, and the test section. The stainless steel plenum upstr
45、eam of the test section was 153 inches (39.35 cm) in diameter, and had a capacity of about 42 gallons (1.7010- m3). Secondary fluid was supplied to it through two diametrically opposed 3-inch (7.61-cm) outside diameter pipes. a means of studying the mixing characteristics in the throat. A shorter th
46、roat length (5.66 throat diameters) was investigated in reference 5 and resulted in improved perfor- mance. 1 1 In reference 3 a test section throat of length 7.25 diameters was used primarily as If mixing could be efficiently completed in a shorter throat length, lighter and 5 Provided by IHSNot fo
47、r ResaleNo reproduction or networking permitted without license from IHS-,-,-1 inlet , Throat staric-pressure-tap location Secondary Diffuser region -0.9 1-0.4 Axial location from throat entrance, xldt 0.11 0.91 1.81 2.6 13.5 14.01 4.6 15.3) 6.41 7.91 9.41 10.9 113.1 115.3 117.5 119.8 29.71 (75.4)-
48、-Throat,d- Diffuser, Ld = 22.09 (56.0)- P z = 4 77 (12 1) Total-pressure probe location 5.0 Ill. 0 116.9 I 1 d? 2. 33 (5.9) L a -. -t 08 u v) v) P) L a -. 04 Throat -. 08 I -4 0 4 8 12 16 20 Axial location from throat entrance, x/dt Axial location from throat entrance, x/dt Figure 11. - Effect of no
49、zzle spacing on static-pressure Figure 10. - Effect of flow ratio on static-pressure dis- tributions. Throat length, 3.54; diffuser included distributions. Throat length, 3.54; diffuser angle, angle, 6“; area ratio, 0.066; nozzle spacing, 0. 6“; area ratio, 0.066; flow ratio, 3.0. This was observed and discu
