A novel hydrogen engine one litre two stroke delivering top power 110 kW and brake efficiency 36% within the 25 kg total weight constraints

• Two stroke hydrogen engines can be made more efficient.
• A novel mechanism is proposed to permit external scavenging without valves.
• Top power and efficiency of the 1 L engine are 100 kW and 36% with weight 25 kg.

The paper presents a novel design for a viable two stroke hydrogen engine that delivers excellent fuel economy and low emissions within the constraints of today's cost, weight and size. The engine features asymmetrical port timing through a translating and rotating piston mechanism. The engine is externally scavenged and supercharged, has wet sump and oil pressure lubrication, direct injection, it is lightweight, easy to build, with minimal number of parts, low production cost, ability to be balanced and compact design. The two stroke mechanism produces a linear motion of the pistons as well as an elliptical path on the surface of the cylinder. This allows the piston to sweep as well as travel past the ports. The piston has a raised lip around portion of its circumference that communicates with the inlet and exhaust ports through its sweep and linear motion that assist in creating the port's asymmetry to make the exhaust port to open first and to close first. The inlet port opens approximately 23° after the exhaust port opens, and remains open for some 20° after the exhaust port closes. The inlet port remains open to complete the cylinder charging and allow supercharging. The piston generates a perfect sinusoidal motion. Direct fuel injection and jet ignition are adopted for best results over a wide range of speeds and loads. The load is controlled by the quantity of fuel injected and changing the supercharger speed through a continuously variable transmission. This paper includes design details as well as result of engine performance simulations. The engine has better than traditional two stroke engines (1) top brake efficiency in the high 30% range and (2) range of speed and loads where the efficiency is above 30%.