Numerical Simulation Of Gas-solid Two Phase Rotating Detonation Engines Based On Caol And Air

Rotating detonation engines theoretically having higher thermal efficiency than deflagration engines,are being studied widely.Solid fuels such as coal and carbon may reduce fuel cost and improve the propulsive performance of engines.Due to experimental limitations,particle distribution and flow field in gas-solid two-phase rotating detonation engines are largely unknown.In this paper,numerical simulations of coal-hydrogen-air and carbon-air rotating detonation engines are carried out.The finite reaction rate model is used for the gas reaction,the discrete phase model is used for the solid phase,and the kinetics/diffusion-limited rate model or multiple surface reaction model is employed to determine the combustion of particles.The SST k-ω model is used for turbulence model.The main research contents are summarized as follows:(1)Effects of hydrogen mass flow rate and particle diameter on pulverized coal-hydrogen-air rotating detonation engines are analyzed.The results show that the propagation of detonation waves depends mainly on the hydrogen-air reaction.When the hydrogen flow rate is 1.5 kg/s,the uneven mixing of air and hydrogen leads to the instability of the contact surface.With the increase of particle diameter,the detonation velocity increases first and then keeps almost constant.(2)The flow fields and propagation characteristics of carbon/air two-phase rotating detonation waves are investigated.Since the air injection velocity near the inlet is higher than the particle injection velocity,the particle layer and the air layer cannot completely coincide,resulting in the local equivalent ratio before detonation wave higher than the global equivalent ratio.The air above the particle layer will pass intersection between the detonation wave and the oblique shock wave,forming a lower temperature stripe.According to the distribution of gas-solid phases in the combustor,the flow field can be divided into three regions: filling zones,detonation product zones and the deflagration product zones.With the increase of air flow rates,the detonation velocity first increases and then decreases.The detonation velocity reached the maximum and the mode transition process occurred when the air mass flow rate is 49.03 kg/s.At high equivalent ratios,a new rotating detonation wave is formed by the contact between the high temperature products and fuel-air mixture.(3)The flow field,detonation parameters and propulsion performance of annular and hollow combustors are compared.The results show that the number of incompletely burned particles increases in the hollow combustor,the contact surface is uneven and there is a lack of the low temperature strip behind detonation waves.In the annular combustor,new detonation waves are formed by the collision between detonation waves and combustor walls,whereas in the hollow combustor,new detonation waves are generated through the collision of shock waves downstream of the combustor.Compared with the annular combustor,the detonation pressure of the hollow combustor is lower,and the thrust of the engine decreases and becomes more unstable under the same operating conditions.