Preliminary explorations of the performance of a novel small scale opposed rotary piston engine

With the increasing pressure of fossil fuel consumption and pollutions from vehicles powered by internal combustion engines, much attention has been attracted for hybrid and electric vehicles. With this background, an increasing demand for compact and high power density engines is being developed for the purpose of hybrid vehicles. In this paper, the design of a novel opposed rotary piston engine was investigated. In comparison with conventional reciprocating engines, this design has no crank connecting rods and intake/exhaust valves, and the operation cycle takes 360° crank angle to complete but similar to a four stroke cycle. 3D and 1D simulations were conducted to analyse the in-cylinder flow and evaluate the engine performance. The simulation results indicated the air velocity was very high at the end of intake stroke due to the lack of intake valves. The opposed rotary piston engine had a higher fraction of constant volumetric combustion that yielded to less heat loss, which contributed to a higher power output per combustion cycle than a reciprocating engine at low engine speed. The estimated minimum brake specific fuel consumption and maximum power density were 240 g/(kW·h) and approximately 80 kW/L, respectively. •The novel engine significantly simplified the intake structures.•The engine operation covered four power strokes in one shaft rotation.•Each stroke lasted 120° geometric angle during engine operation.•The maximum power output density was ∼80 kW/L around 5000 rpm.