Experimental Researches of Supersonic Hydrocarbon Fuels Combustion

Abstract

The description of a facility for an experimental research of supersonic hydrocarbon fuels combustion is given. The facility built in result of a large-scale shock tube modernization, includes a variable volume prechamber, changeable supersonic nozzles, combustion chamber, diffuser and exhaust system. The prechamber can consist of one or several vessels having cylindrical form with a minor diameter of 0.5 m and 9 m of length. The maximal pressure in the prechamber can reach 20 Mpa. The heating of air going to the prechamber can implement with the help of ohmic or electric arc preheaters, as a result of hydrogen combustion in an air mixture with heightened contents of oxygen or by an adiabatic compression of air with usage of a light cylinder piston (~ 30 kg), accelerated in a tube with a minor diameter of 0.5 m and length up to 200 m as a result of firing an oxygen-hydrogen mixture. The supersonic air mixture flows going into the combustion chamber realized by statement of wear bushings in a Laval nozzle in Mach numbers range of 1.8 - 6. The nozzles (and also combustion chambers) can be flat or have the axisymmetrical shape. Their maximum cross sectional dimensions can not surpass 0.5 m. It is possible to enter into the combustion chamber any hydrocarbon fuel or hydrogen with the help of a special injection system. The exhaust system includes a gas holder having diameter of 3.2 m and volume 180 м3. With the help of powerful vacuum pumps it is possible to create rarefaction in the gas holder ~ 1Pа for rather short time. It allows to simulate conditions for air-breathing engines at flight altitudes up to 30 km. As example the experimental researches of supersonic hydrogen combustion in the combustion chamber of rectangular section 25х40 мм 2 on an entrance and 25х 80 мм 2 on an exit are presented at a Mach number, equal 1.8. In these experiments the heating of air up to ~800 ° C in a prechamber as a result of hydrogen combustion in an air mixture with the heightened oxygen contents. The description of the experiment technology realization is given and the obtained experimental data are analyzed.