Development of the X4: a 30kW heavy fueled rotary engine with target 45% brake thermal efficiency
This paper presents a progress towards the development of the LiquidPiston 'X4' 30kW heavy fueled rotary Compression Ignition engine prototype. The X4 Engine is the newest version of the LiquidPiston unique rotary 'X' engine architecture, which can be likened to a Wankel type rotary engine that has been inverted. The engine operates on an optimized thermodynamic cycle, called the High Efficiency Hybrid Cycle (HEHC), which combines: 1) a high compression ratio; 2) constant volume combustion, effected by a dwell in combustion volume for a significant period of time; and 3) over-expansion, e.g. a greater expansion ratio compared to compression ratio. The engine development is funded by DARPA, and the long term objectives of the program target: 45% brake thermal efficiency; > 1 hp / lb operating in CI of heavy fuel; and the 30kW (40hp) engine will fit in a 10" box and weight <40lbs.