Research On Gas Path Fault Propagation Of Marine Gas Turbine Based On Bond Graph

The marine gas turbine is composed of many complicated components,which cooperate with each other to assure the normal operation of the equipment,thus the gas path failure in the marine gas turbine is not caused simply by a single component.In order to accurately investigate the faults and explore the interactions among various components,it is necessary to study the mechanism of gas turbine fault propagation.This thesis uses gas turbine on ships as the research object and takes the bond graph to conduct the researches.The time-based causal graph model of the marine gas turbine is established based on the causality relations The qualitative reasoning analysis method and fault propagation analysis method are studied Then both the typical qualitative and quantitative gas path fault propagation paths are obtained.This provides useful guidance for marine gas turbine fault diagnosis research.In summary,the main contribution of the thesis is listed as follows:(1)Research on the modeling of marine gas turbine bond graph:The theory of bond graph is studied,where the basic components of the bond graph,multi-bond graph and pseudo bond graph are analyzed.Based on the effort-flow relationship of gas turbine components,a marine gas turbine bond graph model is established,which can reveal the power flows,energy transitions and the causality relations.The simulation results show that the proposed gas turbine bond graph model can well match the experimental data,and the average error is within 2%,which meets the requirement of subsequent fault propagation analysis.(2)Research on gas path fault propagation modeling of marine gas turbine:Based on the proposed marine gas turbine bond diagram,the fault propagation causal graph model is established with respect to the time-based causal graph theory.The proposed fault propagation causal graph model achieves the extraction of time causality among various component variables,and solves the problem that the causal relationship among gas turbine components cannot be visually expressed on the bond graph,which provides a basis for developing the fault propagation path of marine gas turbine.(3)Research on qualitative reasoning analysis for gas path fault propagation of marine gas turbine:The qualitative reasoning analysis method and fault propagation analysis method are studied lied on time-based causal graph,and the evaluation rules of qualitative reasoning are given based on the four fundamental arithmatic operations and calculus conditions.Besides,the impact of different time steps on the results of the analysis is also given.The analysis of effort-flow change under typical fault in the gas path is then carried out,which brings qualitative analysis of effort-flow changes under typical gas path faults.Thus,the separation of gas fault propagation paths is realized,and the fault propagation path under typical gas path fault conditions is obtained.(4)Research on data-driven analysis of gas path fault propagation:For the problem that the effort-flow change cannot be quantified in qualitative reasoning analysis,an axis-based calculation method is proposed based on the size and direction of the bond graph flow.Thus the typical gas path fault is analyzed quantitatively,and the impact of thresholds on quantitative analysis of fault propagation results are also discussed.(5)Research on diagnosing gas path fault based on propagation path:The"IF-THEN"rule for the qualitative identification of gas path fault propagation and the probabilistic neural network for the quantitative identification method for the fault propagation path are introduced,and then simulation examples are used to verify the performance.The results show that the proposed qualitative identification method can describe the changing and evolving of effort-flow in the gas turbine along the time axis,while the quantitative method based on probabilistic neural network achieves the typical fault propagation diagnosis under stable conditions,which provides a new method for gas path fault diagnosis.