摘要：The relationship between engine mechanics and thermo-dynamics has been investigated by means of numerical *** inherent mismatching between the mechanical behaviors and the thermodynamic process in internal combustion engine is identified,which is believed to be one of the important limiting factors of energy efficiency for conventional engines available in the current *** approach for engine efficiency improvement through optimal matching between mechanics and thermodynamics(OMBMT)is *** ideal matching model is defined and the conflicts due to the constraints among the mapping strokes in a 4-stroke engine are analyzed.A novel mechanical model is built for approaching optimal matching among all 4 individual strokes in a 4-stroke spark-ignition engine,which is composed of non-circular gears(ncg)and integrated with conventional slider crank engine *** means of digital mechanical model and numerical simulation,the matching gains among all 4 strokes are defined and calculated for quantifying the ncg engine efficiency improvement by comparing with a baseline *** potentials with the OMBMT implemented and the enhancements made by ncg mechanism for engines in terms of overall engine efficiency are *** on the results achieved,it is recommended that the feasibility studies and the experimental validations should be conducted to verify the engine matching concept and effectiveness of the ncg mechanism engine model proposed,and the engine performance and ncg design parameters should be further optimized.