Study On Dynamic Characteristic Of Diesel Engine Main Structure System

"Convenient to take"-monitoring and fault diagnosis system for military engines is developed by equipment dynamical engineering center of NEU together with a certain Troop, Shenyang Military Command. Based on the engineering research on the structure of 6BT5.9 diesel engine, as a sub-projects, the dynamic analysis is conducted systematically and intensively in the paper, and experimental verification of main parts is also performed. A comparison shows that the theoretical calculation results are quite consistent with those achieved in experiments.Based on the modal analysis theory, the structure and working conditions of the diesel engine is analyzed, international and native research about the dynamic analysis of the diesel engine is studied systematically, and the finite element method(FEM) is applied to the theoretically. By ANSYS software, the finite element models of the diesel engine with engine block, crankshaft and cylinder head are constructed in this paper. This overcomes the difficulty in application of the finite element modeling with plate and shell, and simultaneously calculates and analyzes every free modal parameter of the models.The diesel engine is composed of a lot of the complex components and parts. How to simulate the boundary conditions of combined structure properly, and it is the heated problem of model analysis area. Traditional methods was not in reason when deal with substructure of relative relationship of components. This paper tries to find a new way to simulate boundary conditions of combined structure effectively at the base of former scholar. A method was initially put forward that is to use anisotropic virtual material to simulate the characteristics of combined parts. That is when entering material parameters, different directions have different value, so it can simulate combined stiffness of every direction, and it will also simulate the relative movement relationship of components effectively. The dynamic analysis of the structures are required to describe structural systems accurately in theory, the method is a detachable structure, continuous system has become distributed relate structure in a node Through the hypotheses of the structural material and shape, the simplification of the structural constraints and joints, the theoretical calculation models are established by finite element techniques, for accumulating bias about model structure, order and parameter, are their results reliability? This is required to be verified in experiment. Based on the modal analysis theory, modal testing system is built, and a set of modal parameter identification program is established by Matlab software. Then the modal parameter of engine block, cylinder head and its Combined Structure are obtained.Based on modal correlation theory, the modal correlation analysis is done by the end of this paper. Modal parameters achieved by finite element method coincide with those achieved in experiment, which shows the correctness of the models and adopts the proper research methods. This work establishes a foundation on the dynamic response calculation, the dynamic characteristic analysis of the diesel engine and failure diagnosis of the Diesel Engine step by step.At last, this paper roughly study the transient analysis of the engine block, the theory of transient analysis of engine block is the heated and also the difficult problem of model parameter identification area. It also proposes the new idea to the monitoring and fault diagnosis of diesel engine.