SBIR-STTR Award

Project objective is to examine an air-assisted mechanical fuel injection concept from the 1916-1950 era for use on JP-8 fuel in a small 2-stroke engine. Patent literature shows a method to vigorously inject a carbureted fuel/air mixture into a working cylinder by use of a 5x-smaller auxiliary piston. Injection pressure of 5 to 7 atm is available which would effectively atomize a heavy-fuel and air mixture for combustion in a stratified-charge spark-ignition engine. By injecting a fuel/air mixture rather than "solid" fuel, the in- jector size is increased about 500 times, which allows less precision for the injector working parts. This in turn allows the entire engine size to be scaled down to the 5-15 hp range. Fuel is injected after exhaust port closure. We propose exploratory development of the injector components (piston, nozzle check valve, and carburetor) for phase I, which will show the feasibility of the fuel injection hardware. The full size layout of the anticipated single-cylinder engine shown in the appendix should produce a 9 hp output at 7750 rpm on JP-8 fuel. The double-piston single-cylinder engine would be constructed for Phase II demonstration, with multiple cylinders for future effort. Incidentally, the engine layout in appendix is different than prior art, a US patent on the improved Herbrandson version is in work. We call the fuel injection process Direct Mixture Injection (DMI).

Benefits:
The DMI two-stroke engine can be used in military ground power APU applications on JP-8 fuel with one or two cylinders, probable as an in-line twin. Airborne applications such as Maneuver (UAV-M) could benefit from this engine as an in-line twin, in-line-three, or an opposed four-cylinder boxer.

Keywords:
multi-fuel Spark-ignition Flight-weight Compact UAV-Maneuver Direct-injection Modular Two-stroke