Study on off design characters of turbocharged solid propellant ramjet

In order to obtain propulsion systems with a high specific impulse and wide operating envelope, the turbocharged solid propellant ramjet (TSPR) propulsion system was proposed by integrating the turbocharged system of solid propellant air turbo rocket (ATR) and fuel rich gas generator of solid propellant ramjet (SPR). The off-design code was established for TSPR. Two control plans were proposed: constant air residual fraction of combustor, constant mass flow rate of fuel rich gas. The off-design code was validated by the test results of ATR which is similar to TSPR. Regulation characteristics of TSPR with these two control plans were studied. The specific impulse of designed TSPR for the two kinds the control plans are higher than ATR which has same design thrust and specific thrust of designed TSPR. TSPR with constant fuel-rich gas flow rate has larger thrust adjustment range than with constant air residual fraction, and the regulation characteristics is closer to ATR. Designed TSPR can operate within 0~2.4 Ma, 0~16 km with constant physical engine speed. TSPR has maximum thrust in low altitude and has the maximum specific impulse in high altitude. The performance of TSPR with constant fuel rich gas flow rate is slightly lower than constant air residual fraction plan, but regulation is simple and easy to achieve, so constant fuel rich gas flow rate plan is more practical for TSPR.