Exploration And Research On The Key Technologies Of Powdered Fuel Ramjet

Powdered fuel ramjet, which employs high energetic powder as fuel, ram air as oxidizer and working gas, is a new concept propulsion system. It has the advantages of high energy, high volumetric specific impulse, high safety, flexible trust management and multiple start-ups, which make it a perfect propulsion device for next generation supersonic missiles. In this dissertation, exploring researches on the theoretical performance, operating characteristics and working processes of the powdered fuel ramjet system were carried out roundly and systematically by means of theoretical analysis, numerical simulation and direct-connect experiments. The key techniques such as powder fuel feeding, ignition of engine and self-sustaining combustion of fuel were broken through.Based on the thermodynamic calculation and theoretical performance analysis, effects of fuel, air/fuel ratio, combustor pressure, Mach number and flight height on the performance of powdered fuel ramjet and temperature of combustor were analyzed. In addition, the influence of slag accumulation was discussed.A theoretical model of laminar flame propagation in powder dust clouds was established. By solving the energy equation in each regime and matching boundary conditions, an algebraic equation of flame speed was obtained. Numerical calculation method was used to study the effects of pressure, initial temperature, gas-solid mixture ratio, particle size, particle velocity lag and radiant heat transfer on flame speed.Experiments of powdered fuel feeding were carried out. During the test, the real-time mass flux of two-phase mixture was measured with Coriolis Mass Flow Meter. The result shows that powdered fuel can be fed availably and equably. Experiments were carried out in order to investigate the influences of different initial loading states, particle diameter and velocity of piston on the operating characteristics of fuel feeding system. On the basis of the two-fluid model, the two-dimensional unsteady two-phase flow field in the fuel feeding system was studied by numerical simulating. According to the results, effects of different operating conditions on response characteristics of feeding process were analyzed.Hot-firing tests of powdered fuel ramjet were conducted on a direct-connect test bed. Ignition was realized successfully with high temperature combustion gas and high energy spark plug. The feasibility of self-sustaining combustion of powdered fuel was demonstrated by introducing different flame holding techniques into combustor. The multiple start-ups of the engine was also successfully performed using the spark plug as ignition source. To explain experimental phenomena, the three-dimensional two-phase combustion flow field in the combustion chamber was numerically simulated by the particle trajectory model. The low frequency combustion oscillation of the engine was studied. It was found that combustion instability come from the couple of fuel feeding and chamber processes. The oscillation combustion was suppressed by improving the injection pressure drop of powdered fuel.In order to investigate the influences of structure and working parameters on performance of the engine, experiment and numerical simulation were carried out. At last, the feasibility of engine used aluminum powder as fuel was demonstrated by experiment.