Research On The Spraying And Combustion Of Diluted Ethanol/Hydrogen Peroxide Gas Generator

Diluted ethanol spraying and evaporation, hydrogen peroxide catalytic decomposition, ignition and combustion of diluted ethanol in decomposed hydrogen peroxide were studied in detail by means of theoretic analysis, experimental investigation and numerical simulation. And many significant results, which are important to design and optimize diluted hydrogen peroxide/ethanol gas generator, have been acquired.The discharge and atomization characteristics of five types of gas generator injectors in different configurations were tested. The influences of injector configurations and test parameters on the discharge and atomization characteristics were experimentally studied in detail. The pressured container was designed to study the atomization performance under high pressure environment. Some important conclusions have been obtained from experimental results. Firstly, the discharge coefficient of gas and liquid in external-mixing injectors, which have gas channels and liquid channels separately, is affected obviously by injector configurations but rarely by test parameters. Secondly, the discharge coefficient of two phase flow in internal-mixing injectors is affected distinctly by both injector configurations and test parameters. Finally, the pressure affects the atomization through the velocity of gas. In the high pressure environment, the velocity of gas is subsonic, and the velocity decreases while the pressure rises, which worsens the atomization performance.The evaporation model of multi-composition droplet was presented, which was validated by experiments. The process of combustion in the model gas generator was simulated using the evaporation model, and the results showed that during the evaporation of diluted ethanol droplet, ethanol evaporates faster than water on the droplet surface because of different distillation characteristics, which makes the temperature of the combustion chamber increase at the beginning and then decrease along the axis. The high temperature around the injection panel is good to flame stabilization.The combustion experiments of model gas generator equipped with quarts windows were conducted. The law of flame propagation during ignition and stable combustion, and infuences of the ethanol concentration and the injector configuration on the flame and the combustion performance were investigated. The results showed that the coaxial shear injector with larger indent distance or exit angle has better mixing performance and higher combustion efficiency. When the intensity of combustion is low, combustion has little effect on the spraying and atomization, and the angles of the flame taper and non-reacting spraying taper are almost the same. When the intensity of combustion is high, combustion has obvious effect on the spraying and atomization, and the angle of flame taper is larger than that of non-reacting spraying taper.Hydrogen peroxide catalytic decomposition performance and the low frequency instability of catalyst bed were investigated by numerical simulations and experiments. The results show that the decalescence of catalyst bed affects the process of hydrogen peroxide catalytic decomposition greatly. If the catalyst bed is preheated or made up of materials with low thermal conductivity, that influence can be depressed. At the same time, the response characteristic of catalyst bed and the efficiency of catalytic decomposition can be improved. The low frequency pressure instability of catalyst bed occurs because of the coupling of catalytic decomposition and supplying. The decomposition plane pushes all the way through the catalyst bed during pressure oscillations, causing unreacted liquid hydrogen peroxide to be exhausted from the bed and leading to the appearance of liquid hydrogen peroxide channeling. Consequently, how to prevent or at least limit this channeling is the key to eliminate the pressure instability of catalyst bed. It was found that adding clapboard to the catalyst bed can depress the pressure instability efficiently.On the basis of the investigations above, the ignition and combustion performances of the diluted hydrogen peroxide/ethanol gas generator were studied systematically. Furthermore, the influences of the oxygen coefficient, the combustor character length and the injection rate of hydrogen peroxide on the performance of gas generator were analyzed. Adopting part of hydrogen peroxide through catalytic bed or reducing the flux and injecting rate of decomposed hydrogen peroxide can improve the ignition performance of this gas generator. Increasing the oxygen coefficient and the combustor character length can enhance the combustion efficiency likewise.