Conceptual Study of Throttled Operation of Rocket Engine Turbopump

Abstract

Throttled operation of turbopumps of liquid rocket engines is studied analytically. Two types of pressure drops in the propellant injector are examined, that is, the drop of gas injection and that of liquid injection. Circulation is examined in relation to throttling to operate the pump in the vicinity of the design condition. An enthalpy increase at the pump entrance is derived analytically in the circulation system. With the derived analytical relationships, throttled operating conditions are examined for imaginary LH 2 and LOX turbopumps with a LH 2 /LOX property calculation code. The circulation causes gasification at the entrance of the high-pressure LH 2 pump. This does not occur in the mid-pressure LH 2 pump or the LOX pump. In the liquid propellant injection system, the unstable region becomes narrower than in the gas propellant injection. The ratio of the turbine flow rate to the pump flow rate decreases in line with throttling. Throttling does not degrade the engine specific impulse from the viewpoint of the turbine bleed ratio.

Expander and Coolant-Bleed Cycles of Methane-Fueled Rocket Engines

“…3, 2018 ber pressure. 17,21) Under the condition of maximum throttle, when a pressure drop in the oxygen injector remains at 15%, it will drop further as throttling is reduced. This large pressure drop in injection affects the necessary pump power and operating range of the engines.…”

“…Several studies have been conducted on the thrust control ability of liquid rocket engines, most of which targeted hydrogen-fueled engines and bipropellant engines. [17][18][19][20][21] For example, it was found that the throttled operation of a rocket engine can degrade excessive acceleration during launch while reducing the thrust required when landing a reusable vehicle. Boccaletto conducted studies on the throttling operation of methane-fueled engines ranging from 40% to 125% when using the SC cycle and the GG cycle.…”