Research On The Overall Performance Of Solid Fuel Scramjet

The solid fuel scramjet has extensive application foreground on future hypersonic weapons system due to its advantages of high specific impulse, simple structure, high reliability, good security, fast response and so on. The investigation on the integrated configuration design optimization and overall performance analysis were carried out by means of theoretical analysis and numerical simulation.A baseline configuration of solid fuel scramjet was designed on the basis of theoretical analysis, and the numerical simulation model of flow and combustion processes in solid fuel scramjet flowpath was established. In order to compare the performances of solid fuel scramjet and ramjet working at low hypersonic speed, the internal flow fields of the two types of engine at flight Mach 6,7,8 were simulated numerically. The results indicate that the advantage of total pressure for solid fuel scramjet is small at flight Mach 6 due to the loss caused by viscosity and obligue shock. The combustion efficiency of solid fuel ramjet is higher, leading to more heat addition in the combustor. When flight Mach increases to 7, the performance of subsonic combustor degrades due to dissociation. The combustion efficiency and heat addition of supersonic combustor is larger, and the scramjet outperforms ramjet.The effect of compression ratio on performances of combustor and the whole engine were studied by means of numerical simulation. The results indicate that when the inlet compression ratio is increased by changing only external turning angle or internal contraction ratio, the fuel mass flow rate declines, leading to the degradation of thrust and specific impulse. The variation of engine performance is affected by both the inlet compression ratio and the area expansion ratio at combustor inlet. With the same combustor inlet area, variation of inlet compression ratio is achieved by changing both the external turning angle and internal contraction ratio. With the increase of external turning angle, inlet compression ratio is increased, and the thrust and specific impulse decrease due to the increase of total pressure loss.An integrated analysis model of solid fuel scramjet was presented. The aerodynamic characteristics were calculated through engineering estimation method, and a propulsion analysis model based on the theory of oblique shock and quasi-one-dimensional flow was established. The analysis model was validated by both the experimental and numerical datas. The design optimization of solid fuel scramjet was conducted by means of theoretical analysis and numerical simulation. The results show that the length of constant area cylindrical section should be as large as possible, and the diversion angle of diverging section should be as small as possible in combustor design. The thrust and specific impulse are optimal at an inlet compression ratio about 25 after the combustor is optimized. Both the thrust and drag coefficients increase with the decrease of air-fuel ratio. The vehicle thrust-drag ratio is maximized at an air-fuel ratio of 11.5 without angle of attack. With the angle of attack increasing, the optimal air-fuel ratio increases gradually. When the angle of attack is increased to 8, the optimal air-fuel ratio is 11.6 for maximized thrust-drag ratio.The effect of inflow conditons on overall performance of solif fuel scramjet was simulated numerically. The results indicate that the fuel mass flow rate decreases with the increase of altitude at the same flight Mach, causing the decrease of thrust and specific impulse. Because of the decrease of thrust coefficient and increase of drag coefficient, the thrust-drag ratio decreases with the increase of altitude. Under constant dynamic pressure, thrust and drag coefficients decline with the increase of flight Mach, and the thurst-drag ratio is optimal at the design point of flight Mach 6.