Simulation on combustion characteristics of non-crankshaft reciprocating natural gas engine based on equivalent speed method

Internal combustion engines (ICEs) face challenges in balancing efficiency and emissions. This study designed a non-crankshaft reciprocating engine (NCRE) using non-uniform rotational speed technology to optimize combustion and reduce emissions. The NCRE employs natural gas as the primary fuel, with gasoline ignition, to enhance combustion dynamics. A multi-disciplinary framework integrating non-uniform speed models, piston motion dynamics, and computational fluid dynamics (CFD) simulations was developed to analyze performance. The results show that compared with traditional engines, NCRE has improved by approximately 2% on the indicated thermal efficiency (ITE), and releases more energy, burns more thoroughly and more rapidly; nitrogen oxide emissions have been reduced, which is attributed to the improved turbulence and controlled piston movement. The design of NCRE introduces the method of non-uniform rotational speed into the engine, filling the gap caused by the piston movement in changing the airflow inside the cylinder, and providing a way to achieve an efficient and low-emission power system.