COMBUSTION SCIENCE & ENGINEERING, INC. — Department of Defense SBIR Phase I: AF221-0023

Description

Hypersonic flight is difficult due to the extreme conditions under which the vehicle must operate, including temperature, high aerothermal loads, and the presence of shock waves [1].  Combustion at these conditions is compounded by these factors but have specific issues that have identified over the many decades of development of these vehicles.  The problem of ignition and flame-holding for an efficient combustion, and a high-altitude re-ignition of the air-breathing Scramjet engine is of great importance for creating an efficient hypersonic engine. The main challenges in having sustained and repeatable ignition are the very high flow velocity in the combustion chamber and the low initial temperature of gas and fuel when starting/restarting a cold engine.  Numerous attempts have been made to improve the combustion characteristics with the help of electrical discharges.  However, all existing solutions for ignition systems have significant drawbacks that limit the effectiveness of their use for hypersonic systems. This is mainly due to conflicting requirements for such an ignition system. It must work stably both at moderate and at very high gas velocities; it should provide effective ignition both at low temperatures and at temperatures close to the self-ignition threshold; finally, it must have low energy consumption.  The solution proposed by this team involves high-voltage nanosecond aperiodic discharge with high-nonequilibrium and fast thermalization The technical objectives of Phase I include a) demonstration of the feasibility of the system to promote ignition and flameholding in high-speed combustion flows; b) determine preliminary system requirements to enable ignition and flameholding in the scramjet environment, including power, volume and mass packaging, but also the temporal and polarity distribution of the discharge.  A combination of both experimental and simulation work is proposed to meet these objectives.