Innovative Small, Heavy Fuel Engine Concepts - A Separate Process Diesel (SPD) Engine for Unprecedented Power Density

A novel Separate Process Diesel (SPD) engine design with an unconventional gas cycle is presented which uses three interdependent chambers to process the working fluid; a piston compressor, a rotating combustor unit and a piston expander. The SPD cycle outperforms current lightweight high power density engines primarily due to its increased mass induction per cycle. The SPD compressor cylinder inducts as much fresh mass as a two cylinder four stroke engine with similar displacement since an induction stroke occurs each revolution. If boosted, the piston compressor of the SPD engine can exceed mass flow rates of conventional light-weight 4-stroke diesels while operating at peak pressures typical of gasoline engines since the expansion ratio of the piston expander is much lower than the compression ratio of the piston compressor. Fresh mass from the turbocompressor is forced through the expander piston every revolution as well with anticipated scavenging efficiencies near 70%. This mass is subsequently compressed in the expander piston and combines with a fuel rich mixture of partially burned gases from the combustor near TDC allowing for additional diffusion controlled burning during the expansion stroke. It is anticipated that this unique SPD design will induct nearly two and a half times the fresh mass of a similarly sized naturally aspirated light-weight diesel without exceeding peak pressures typical of gasoline engines. With its excellent higher speed potential, since burning is initiated in a constant volume combustor rotating at one-half of the output shaft speed, it is believed that the SPD design will exceed power/weight ratios of 1.0 while meeting specific fuel consumption limits.