The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for ...The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for evaluating the stress distribution and distortion of teeth profiles in a gear/shaft assembly,a transient thermal analysis is necessary for finding the change in mechanical properties.The friction on the contact surface is another important parameter in interaction of the gear with the shaft.Evaluating the gear stress and deformation fields for several modes of heat transfer and friction coefficients showed that the maximum radial or tangential stresses on contact surface of the joint may have more than 8%increase by increasing friction coefficient;while the intensity of heat transfer at cooling stage has lower effect on stress distribution.展开更多
The relationship between engine mechanics and thermo-dynamics has been investigated by means of numerical simulation.The inherent mismatching between the mechanical behaviors and the thermodynamic process in internal ...The relationship between engine mechanics and thermo-dynamics has been investigated by means of numerical simulation.The 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 market.An approach for engine efficiency improvement through optimal matching between mechanics and thermodynamics(OMBMT)is proposed.An 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 mechanism.By 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 engine.The potentials with the OMBMT implemented and the enhancements made by NCG mechanism for engines in terms of overall engine efficiency are reported.Based 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.展开更多
文摘The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for evaluating the stress distribution and distortion of teeth profiles in a gear/shaft assembly,a transient thermal analysis is necessary for finding the change in mechanical properties.The friction on the contact surface is another important parameter in interaction of the gear with the shaft.Evaluating the gear stress and deformation fields for several modes of heat transfer and friction coefficients showed that the maximum radial or tangential stresses on contact surface of the joint may have more than 8%increase by increasing friction coefficient;while the intensity of heat transfer at cooling stage has lower effect on stress distribution.
文摘The relationship between engine mechanics and thermo-dynamics has been investigated by means of numerical simulation.The 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 market.An approach for engine efficiency improvement through optimal matching between mechanics and thermodynamics(OMBMT)is proposed.An 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 mechanism.By 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 engine.The potentials with the OMBMT implemented and the enhancements made by NCG mechanism for engines in terms of overall engine efficiency are reported.Based 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.
