Research On Quasi Steady Stirling Cycle Analysis Model And Energy Loss Mechanism

A Stirling cycle analysis model plays an important role in design and optimization of a Stirling engine.It cannot be used to study the effects of heat and mass transfer characteristics of oscillating flow and energy loss on heat-power conversion process of Stirling cycle if an oscillating flow model is adopted without pressure gradient equations,which limits flexible design and optimization of a Stirling engine.In order to improve the adaptability of Stirling cycle analysis model the following work is conducted:An improved multi-node Quasi Steady Stirling cycle analysis model is developed,embedding pressure gradient equations and energy loss of oscillating flow.Differential equations were established,considering conservation of mass,energy,momentum for the internal working fluid gas and matrix regenerator.Momentum equations were built based on a quasi steady assumption with pressure drop equations of oscillating flow.Heat transfer characteristics of oscillating flow was considered in the energy equation,and energy loss was coupled into energy equations for compression and expansion process.A proposed model was used to analyze performance characteristics and energy losses based on the GPU-3 Stirling engine.The average prediction errors of indicated power and efficiency were 9.6% and 6.3%,respectively,under the rated conditions of GPU-3 engine using helium as working medium;and the average prediction errors are 15.0% and 10.4% for power 3.8% and 6.7% for efficiency when helium and hydrogen were used as working mediums,respectively.The leakage,shuttle,pumping and flow resistance losses were the main losses,accounting for 73.2% on average based on energy loss analysis at variable speeds.Three characteristic indexes were proposed to express different energy loss mechanisms caused by oscillating flow with pressure gradient in a Stirling cycle.Three characteristic indexes were proposed,i.e.slope ratio,IOU(intersection over union),and pressure ratio,which were expected to express different energy loss mechanisms of Stirling cycle.The simulation results were compared with those of Sage based on a 100 W ?-type Stirling engine when helium was used as working medium at 1.73 ~ 2.85 MPa with an operating speed of 440 ~ 1396 r / min.The average IOU was 8.8% higher than that of Sage at different speeds,and was 10.1% higher at different pressures.The flow resistance loss could cause 'thinner' p-V diagram in a expansion space.The additional gap loss could bring a 'thinner' p-V diagram in a expansion space while could bring a 'fatter' p-V diagram in a compression space'.The leakage loss could cause a 'fatter' p-V diagram in a compression space...