Small, Heavy Fuel, Compression Ignition Small UAV Engines

This Heavy Fuel Engine (HFE) proposal describes an innovative propulsion system that meets the near term Army FCS class II OAV propulsion system requirements. The proposed approach is an innovative Supercharged Injected 60 degree V-twin uniflow four-cycle design of 450cc cylinder capacity designated (SIV-2225). Unlike commercial off the shelf conversions, the proposed SIV-2225 overcomes small scale thermal and specific volume deficiencies by means of positive displacement built-in supercharge with high adiabatic and trapping efficiency resulting in scavenge air delivery ratios approaching 2:1. High thermal and combustion efficiencies are achieved by doubling the trapping volume prior to the compression stroke thereby significantly reducing the effective surface/volume ratio and associated heat losses. Internal pumping losses are kept to minimum due to the maximum port time area associated with uniflow sleeve design, which, affords up to 85% of the cylinder circumference for breathing. This equates to 4 times the breathing capacity when compared to overhead poppet valve designs. As a result this 4-cycle uniflow sleeve valve engine has a breathing capacity well beyond the 12,000 RPM range. In addition, the low profile cylinder head retains complete freedom of the combustion chamber, which is an invaluable feature when optimizing the required heavy fuel combustion system.