Research On Calculation Of Vibration Characteristics And Test Of Stirling Engine

From the last decade of the 20^th century,Stirling engines have been applied in both military and civil fields due to their unique characteristics of low pollution,excellent NVH performance and high theoretical heat efficiency.The NVH property of a Stirling engine has significant impacts on acoustic stealth of military equipment.Therefore,the NVH property is one of the most important indexes need to be optimized.The research was carried out on the multi-body dynamics,the stimulating force and its relationship with the natural frequency,which are of great significance and industrial application value.The research on the vibration prediction of Stirling engine is carried out in this paper,which will provide the theoretical foundation on noise and vibration control of Stirling engine.The main work and conclusion are as follows:1.By comparing different mesh size and element type of certain components,the ideal mesh size and element type are decided.Through the modal analysis,the correctness of the FEM model has been testified.After importing the testified FEM model o ANSYS and defining the master DOFTs,the condensed model is created in AVL EXCITE.2.The analysis of piston knocking force:after building GUID?Piston-Liner Guidance?and EPIL?Elastic Piston-Liner Contact?connecting element,the force between the piston and liner is calculated respectively,where the conclusion that the results are highly accordant are made,while the GUID connecting method needs much less master nodes and model-condensing time compared with EPIL connecting method.3.The analysis of the balance shafts'impact on excitation force:by comparing the stimulating force on the complete multi-body transmission system with the transmission system without balance shaft in both time and frequency domain.The bearing load on balance shaft is 2 orders of magnitudes less than that of the main bearing.In the frequency domain,the gear meshing frequency component is not obvious,while the master nodes on balance shafts make up more than half of the master nodes of the whole model.In conclusion,the neglect of balance shaft will not bring significant influence on the results,while the model scale will be reduced to a great extent.4.By comparing the piston knocking force,the ideal connecting method-GUID has been determined.By analyzing the force in multi-body transmission system,the simplified method that the balance shafts are not taken into consideration in the transmission system is generated.The multi-body dynamic model for the whole engine is set up according to the analysis above.5.The vibration measurement of the Stirling engine is conducted.The acceleration comparison between the calculated and measured values in both time and frequency domain testified the correctness of the calculation,which provide the theoretical foundation for the vibration reduction method.