Implementation of Unit Injectors in Small, Heavy Fuel Engines

The U.S. Department of Defense is currently interested in obtaining small engines that are lightweight, reliable, durable, fuel efficient, and low cost for many applications. Some of these applications include providing propulsion and power generation for small unmanned aircraft systems (UAS), unmanned ground systems (UGS), and unmanned maritime systems (UMS), with power requirements in the 8 kW range. Engines of this size will require smaller components that may not be commercially available, such as ignition systems, fuel injectors, and fuel pumps. For fuel injection systems, it would be beneficial to use unit injectors, which combine the fuel pump and nozzle into one unit and allow for much higher fuel injection pressures in a smaller package, improving performance while reducing components and weight compared to conventional systems. Mainstream proposes to develop small unit injectors that would be applicable to small, heavy fuel engines for military applications. First, Mainstream will integrate existing commercial electronic unit injectors into one of Mainstream’s existing large engines and design a control strategy to maximize performance and efficiency. After the benefits of unit injection have been demonstrated with bench-scale tests and simulation models, design of the smaller unit injector for engines in OSD’s 8-kW target power range will follow.