Research On Dynamic Characteristics Of Hydrogen Peroxide Engine

Liquid propellant rocket engine with hydrogen peroxide as its oxidant has prosperious future and one of the most difficult things to develop this type of engine is its dynamic characteristics, as is researched deeply in this thesis by means of theoretical analysis, numerical simulation, and experiment research.A new method used to simulate liquid rocket propulsion system is proposed by the name of mixing-dimensional simulation. And there are three modes of dimension mixing: static parameter mixing, dynamic parameter mixing, dynamic direct mixing, all of which are researched with relative theories. The discharge coefficiency of injector, as is an example of static parameter mixing, is variable with structure parameter and work parameter, considering the injector is so narrow in hydrogen peroxide engine. The modes and frequency response of spring is obtained using 3D CFE method, then spring model is established by means of system identification and the result shows that the equivalent mass occupies 40 percent of total mass because of dead loop. And a pressure adjust valve is simulated based on this spring model. Black-box model and grey-box model of venturi are established based on 2D CFD simulation, results show that the flow rate fluctuates in the range of±3.3% in the conditions of dynamic exit pressure.The starup process of engine is simulated with focusing on the pressure drop before isolation valve. The reasons are found and correlative means to solve this problem are proposed including: (1) change size of supply pipe; (2) regulate the variety of flow rate; (3) install accumulator before isolation valve.The shutdown pocess of hydrogen peroxide/kerosane engine is simulated based on heat transfer and two phase flow aiming at the explosion in experiment. It shows that the peroxide temperature in cooling channel may increases when helium expels in wrong flow rate or in wrong sequence. A scheme of postponing shut of hydrogen peroxide is proposed and the shutdown sequence is optimized through evaluating the effect of peroxide as a coolant or helium as a filling gas on the decrease of temperature.Experiments of engine with low concentration hydrogen peroxide and low concentration ethanol as propellants are conducted. (1) Catalysis decomposition of peroxide is researched especially focused on the catalysis efficiency, activation time and longevity of catalyst bed in order to get the design and use guideline. The low frequency fluctuate in the catalyst bed is elimilated using hole shutter and isolation panel. (2) Combustion performance is researched in different conditions including: different configuration of combustor, structure of injector, efficiency of catalyze and working parameters. Then approachs to improve combustion performance are obtained. (3) The ignition of this low concentration propellant which is very difficult is broken through considering the effect of propellant concentration, pressure drop of injector, ignitor energy and ignition sequence. (4) Low frequency fluctuate which often happens is controlled by analyzing relative factors. Then a series of fast, high efficiency and stable hydrogen peroxide engines are developed with peroxide concentration range of 90%~50%, combustor pressure range of 1.9~4.0MPa, combustion temperature ranges of 900~1800K, flow rate of 0.6~7.7kg/s. And the high temperature gas produced by these engines is very useful in some areas.The mixing-dimension model of experimental propulsion system is established in order to simulate the unstable phenomena. (1) Results from stability simulation show that there is a phenomenon of"ethanol evaporates firstly", as is the reason why injector panel is burnt in experiment. And the combustion efficiency from simulation is consistent with that from experiment; with the maximum deviation is less than 6%. (2) Stability model is established and researched, results show that the propulsion system gets unstable when combustion-lag is more than 12 millisecond. (3) Oscillation frequency from simulation is approximately equal to that from experiment. Then the factors that influence instability degree are checked, including injector pressure drop, excess oxygen coefficient, etc. Results show that too low injector pressure drop leads to unstable but too high drop leads to flameout. (4) And a new concept variable thrust engine using partially catalyzed peroxide is evaluated mainly on its stability and modulation.