Reseurcb Center AERONAUTICS AND - PDF document

Reseurcb Center AERONAUTICS AND WASHINGTON, D. C. MAY 1967 FEED-SYSTEM COUPLING and Robert STRATI ON Federal Scientific PARAMETERS ON the analytical chamber and feed system injector-dome region. coupling with by changing cavitation compliance the degree The maximum the stability istics; the responses were little effect -dome compliance, suction line and distribution in the discharge frequency, and beating The length but did influence attached to the feed-system dynamics and to parameter treatments linearized distributed the propellant feed system stability analysis. differential equations an analog computer elements required to the feed region immediately between the feed system and can dome (very can occur, and the system stability, compliance usually feed system this report, employed, along the effect model employed feed system feed system plus The effect the hard-dome the feed-system maximum influence predicted stability feed-system models been employed The importance Schematic drawing resistance simulators the lengths discharge lines, inlet. Finally, system plus line, and suction and line. The pump-inlet point. The by the combustion dead expressing the the chamber analyzed by wave-plan method The digital modifications and additions. second-order backward finite-difference the calculations. given in to various an analysis chugging-suppression device the stability the combustor feed system The device accumulator that to be compliant and device affected the steady-state the feed system. chugging-suppression device under conditions very small. feed system impedance somewhat The equations represent the and combustion-chamber Discharge line velocities, ft/sec: values listed the reference otherwise specified the numerical The combustion-chamber dome compliance, pump-inlet compliance, suction-line number and analytically the the system, the tank small step injector pressure-drop ratio, 0.223. injector pressure-drop ratio, I I injector pressure-drop ratio, feed system computed. The whether the amplitude AND DISCUSSION coupling between the propellant feed injector-dome accumulator. msec) in chamber to for coupled dome compliance). the system response. small, the to the neutrally stable, dome compliance), where relatively changes in the system response. was deter- (hereinafter called given in near) the feed system time. The the response These frequencies dome compliance in. /psi). and the square inch; per pound square inch; injector pressure-drop combustion-chamber responses oscillatory response. than one acoustic modes the discharge in frequency injector-dome compliance the range points out that optimum dome from the significantly by cubic inch compliance on injector pressure-drop needed for various response charac- order to The magnitude analytical calcula- 6 which losses were pressure-drop ratio was shows that, entirely. Thus, compliance due can range discharge-line pressure discharge-line pressure drop One lump. Injector pressure-drop ratlo, dlscharge-line pressure cavitation compliance) plianc e). this system, the insensitive to computed with the injector value needed chamber-pressure responses be compared pump inlet. The the absence ance to the beating suction line that the system. Suction-line length. suction line (a) Pump-inlet per square cubic inch I I I (c) Pump-inlet Injector pressure-drop three cases The system demonstrates the The length while both held constant. limits, the frequency, and indicate that the length. Injector OF PUMP-DISCHARGE-LINE SYSTEM RESPONSE RESPONSE pressure-drop ratio, 0.073. ] Beat period, msec (4 50 53 56 58 59 63 70 60 75 (4 Discharge-line length, ft 3 3.6 4.2 4.8 5.4 6 6.6 7.2 7.8 8.4 9.0 daximum peak-to-peak ,erturbation amplitude -30 I I I 9- (b) Discharge-line length, 4.8 feet. (d) Discharge-line length, 7.2 feet. v 2 1 -21 I 1 I 0 .15 .M .45 .60 Time, sec (e) Discharge-line length, 8.4 feet, Figure 10. - Effect of discharge-line length. Injector pressure-drop ratio, 0.073. 15 chugging-suppression device The resistive-shunt device cubic foot second and cubic foot the reference the suppression the suppression the system much lower the suppression ratio, the the neutral shows that evident in the suppression zero. This to the suppres- frequency coincides lightly damped, natural frequencies the range in combustion-chamber impedance negative, an the dis- order to suppress the instability in the by lo- the accumulator the injector highest frequency significantly affect the analytical other response feed-system dynamics in any injector-dome region the feed system system dynamics the injector dome that feed- system dynamics tailed feed-system from the an over-conservative report demonstrates feed system indicates that geometry may technique used. report, the feed pump could have neglected with significant change pump-inlet cavitation in resonant modes in the system indicate that, small varia- COMBUSTION -CHAMBER the injector the throat engine nozzle, the derivative in finite-difference time intervals used to calculate chambcr the digital chugging-suppression device attached to shows conditions accumulator attached an interior The accumulator wave action wave action, line and waves may the discharge-line AHl1, AH2, magnitudes; and the velocities the line in accumulator that the line conditions adjacent to change significantly short time be constant accumulator, and change in time interval volume change Therefore, the in accumulator the short interval digital computer calculations, considering the change in change. The in the Wenzel, Leon John R. in Liquid-Bipropellant AGAFDograph no. C. C. and Control Pump Fed, Rocket Engine Dorsch, Robert Lightner, Charlene: in Rocket Feed Systems. aeronautical and space the United States shall in the and space. the widest practicable and appropriate dissemination REPORTS: Scientific and technical a lasting contribution existing knowledge. TECHNICAL NOTES: importance as a contribution to existing knowledge. TECHNICAL MEMORANDUMS: receiving limited distribu- preliminary data, security REPORTS: Scientific NASA contract important contribution Publications include conference proceedings, monographs, compilations, handbooks, special bibliographies. used by particular interest and other applications. Publications include Tech Utilization Reports Notes, and Technology publications may INFORMATION DIVISION