Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development

Following U.S. Army’s single fuel initiative, Wankel rotary engines used in U.S. Army’s shadow unmanned aerial vehicles (UAVs) need to be retrofitted from running on aviation gasoline (AVGAS) to JP-8. The feasibility of retrofitting the engine with a flash vapor direct fuel injector was investigated. A commercial off-the-shelf direct fuel injector was used in the study. A photo detector measurement tool was developed to measure high frequency (>100 Hz) injection event. A coupled electrical-electomagnetics-fluid-mechanical system was simulated to understand the pintle dynamics during an injection event. Optimal injector power drive was revealed to be a multi-stage current profile. A flash heater was designed and tested to be capable of heating up JP-8 from room temperature to its vaporization temperature (>310F) under one tenth of a second at the required flow rate. An ignition test rig was built to compare ignition behavior between AVGAS and heated JP-8. Test result showed that the 550F pre-heated JP-8 had equal or superior ignition pressure rise / ignition delay time than AVGAS