No 3 (2020) Technical mechanics
Technical mechanics, 2020, 3, 18 - 29
VERIFICATION OF A HYDRODYNAMIC MODEL OF A LIQUID-PROPELLANT ROCKET ENGINE’S CAVITATING PUMPS USING EXPERIMENTAL AND THEORETICAL PUMP TRANSFER MATRICES
Dolgopolov S. I.
Dolgopolov S. I.
Cavities at the pump inlet may lead to inadmissible cavitation self-oscillations in the feed system of
liquid-propellant rocket engines (LPREs) and to POGO instability if the oscillation frequency of the
liquid is close to that of the rocket structure. Because of this, it is important to prevent both
cavitation and POGO oscillations as early as at the engine and rocket design stage. This calls for
a reliable mathematical model of the dynamics of LPRE cavitating pumps. In this paper, a hydrodynamic
model of LPRE cavitating pumps is verified using theoretical and experimental transfer matrices
of cavitating pumps. The experimental transfer matrix was borrowed from Brennen, Meissner, Lo, and
Hoffman’s work because it features the least spread of values among the matrices reported in the
literature. The theoretical matrix was borrowed from Pilpenko and Kvasha’s work where is was constructed
for a cavitating pump as a distributed-parameter system. Four versions of the hydrodynamic model
of LPRE cavitating pumps are verified, and six possible model coefficients are considered. Only one
coefficient, namely, the liquid inertance at the cavity location, takes a physically meaningless
negative value, which makes its use impossible. The verification results show that a four-coefficient
model of cavitating pipe dynamics adequately describes cavitation effects in LPRE pumps over the
frequency range up to 200 Hz. The four coefficients are the cavitation elasticity, the cavitation
resistance, the cavity-caused disturbance transfer delay time, and the cavity time constant
or the cavitation resistance distribution coefficient.
liquid-propellant rocket engine, inducer-equipped centrifugal pump, cavitation, transfer matrix, hydrodynamic model, delay element, verification
1. Borovsky B. I., Ershov N. S., Ovsyannnikov B. V., Petrov V. I., Chebaevsky V. F., Shapiro A. S. High-Speed Blade Pumps. Moscow: Mashinostroyeniye, 1975. 336 pp. (in Russian).
Copyright (©) 2020 Dolgopolov S. I.
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