Performance Simulation Of The Heavy Duty Gas Turbine Containing The Gas Supply System And Problem Research For Performance Deteriaterion

With the increasing awareness of global environmental protection and quick peak shaving demand, the thermal power generation units require the development of the direction of high energy utilization efficiency and good environment protection performance. The heavy duty gas turbine and its combined cycle unit have the advantages of low investment, high efficiency, small pollution and quick stop and fast, and have been irreplaceable in the field of fossil fuel power. A dynamic simulation model of heavy-duty gas turbine in order to grasp the matching relationship between each components and optimization of its operating strategy is important technical method for gas turbine system design and performance prediction. The performance of the gas turbine will inevitably degenerate when the unit is running for a long time, so that the overall performance can be reduced, leading to a negative effect on the economic and safety operation of the gas turbine. So it is necessary to extend the performance of gas turbine based on simulation model to the stage of performance degradation, so as to evaluate the health status of the gas turbine.The gas supply system belonging to the heavy duty gas turbine is responsible for regulating natural gas parameters to demand of the combustion; its dynamic regulation ability will influence the stability of combustion, thereby affecting the performance of the whole machine. Therefore, the research of matching relationship between te gas supply system’s dynamic performance and gas turbine overall performance has a positive significance to the design of heavy duty gas turbine system. Because of the different position and operation mode of gas turbine, the performance of its components is different. Air compressor, combustion chamber and turbine belongs to the combustion engine gas path components, its performance can be reflected through modeling and simulation from the measured thermal parameters; and the performance of rod fastened rotor need to be reflected from the point of view of the dynamics. According to the characteristics of the gas turbine gas path components and rotor, the diversification of the research methods can enrich the theoretical method for the prediction of gas turbine performance.In view of this, the paper introduces the construction process of heavy duty gas turbine simulation model containing natural gas supply system, combustor, turbine and compressor. Based on this model, the performance of the gas turbine under the actual working conditions is simulated and the gas path components performance degradation prediction is carried out. At the same time, a rotor dynamic characteristic calculation method is proposed for the non-continues property of rod fastened rotor, and the rod fastened rotor performance degradation prediction is carried out based on this method. The main contents and results of this research are as follows:⑴The establishment of components characteristic self-adaptive simulation model of the heavy duty gas turbine.The compressor characteristics is predicted based on general characteristics curve step by step superposition method; then the general simulation model of gas turbine containing compressor, combustion chamber and turbine is established via component characteristics method; finally according to the actual gas turbine operating data, the adaptive algorithm is used to modify the general simulation model, forming the heavy duty gas turbine component characteristic self-adaptive model with high precision, this model can be used to predict the performance of the real units.⑵Establishing the gas supply system simulation model.The component model of gas supply system is established component model based on the function of each component; The BP neural network is used to analyze the pressure before flow valve setting criteria and pilot/premix flow distribution criteria, then the whole gas supply system simulation model is constructed by adding the appropriate temperature, pressure and flow controllers. This model can simulate the actual system parameters to provide the reference for the proportion of the initial field controller can also set the integral coefficient.⑶The establishment of heavy duty gas turbine simulation model including natural gas supply chain.The gas turbine component characteristic self-adaptive model and gas supply system model are combined to form a full-system simulation model. A steady-state performance verification and simulation work is operated under variable operating conditions, and also the gas turbine main performance parameters are obtained under different conditions of gas and air condition correction curve. The practical operating strategy of gas turbine is simulated by this simulation model. This research proposed a simulation platform for further gas turbine performance degradation.⑷Performance degradation prediction of heavy duty gas turbine gas path components.The performance degradation factors are introduced to the heavy duty gas turbine component characteristic self-adaptive model. By automatically adjusting the performance degradation factors, the time specified gas turbine performance can be simulated by means of adaptive algorithm. From the change of the degradation factor, it can be judged whether the performance degradation happens. The relationship between the changes of thermal parameters and performance parameters in condition of typical type of gas path components performance degradation is simulated. A hierarchical classification method based on the membership degree of the degradation simulation results is designed. The application of this method in real units proves that it has some accuracy and can be used for the preliminary forecast of gas turbine health status.⑸Performance degradation prediction of heavy gas turbine rod fastened rotor.For the property of face tooth meshing structure of rod-fastened rotor, a stiffness reduction factor is introduced to the traditional Riccati transfer matrix. Using the ANASYS contact problem analysis method to obtain the specific stiffness reduction factor values, thus improving the Riccati transfer matrix method for dynamic characteristic calculation of gas turbine rod fastening rotor The effect of high-temperature creep induced stress relaxation on the bending stiffness of the rotor is studied by using ANASYS finite element creep analysis method, and the dynamic characteristics of the rotor under creep were calculated.. It is found that the contact stiffness of the face tooth is gradually decreased with the creep time, and the critical speed is quickly reduced until to a stable extend, and the amplitude of the correlation vibration is increasing. Taking the critical speed as the degradation parameter of the rotor performance degradation, the rotor performance degradation prediction method with the critical speed as the evaluation criteria is designed.The heavy duty gas turbine performance degradation can be researched from two angles of thermal parameters simulation and rotor dynamic characteristics analysis, which is valuable for the improvement and development of the basic theory and methods for the heavy gas turbine performance degradation, providing a new idea for assessing the state of health of heavy-duty gas turbine all system components.