Modeling And Control Law Research For Gas Turbine

Research and development of gas turbine have the characteristics of high risk, high costs and high degree of technology difficulty, etc. These characteristics have hindered the development of gas turbine technology. Thus, exploring methods to develop the gas turbine with low cost and short period has become the crucial problem for scientific research departments. Analyzing the effect of fuel and load on the performance of gas turbine and obtaining the flow rate, pressure and temperature of each section of gas turbine under different conditions with the modeling of the gas turbine based on gas turbine general principle and component property will break a new path to reduce the cost, shorten developing periods and reduce technology risk. Based on the analysis of the operating principle, application and structural characteristics of the gas turbine, this article built modules of compressor, combustion, gas turbine, power turbine, starter motor and rotor, etc. Considering the difficulties in predicting low-speed characteristics of the compressor, an extrapolation method of compressor characteristics based on improved exponents of similarity theory was put forward. Ultimately, low-speed characteristics curve of the compressor of 4MW grade gas turbine was fitted, which contributed to the starting model of 4MW grade gas turbine. The article mainly studied the influence of different loads and power of starters on gas turbine operation performance, which laid a foundation for designing the fuel control law of 4MW grade gas turbine, the research details are as follows.Firstly, on the basis of the operating principle and structural characteristics of gas turbine, the modules of compressor, combustion, gas turbine, power turbine, starter motor, rotor were built with considering expansibility and widespread applicability. By comparing the simulation results of inlet temperature of turbine, outlet temperature of gas turbine and operating line of the gas turbine with the calculation results of GasTurb software, the mathematical modeling was characterized by veracity.Secondly, based on operation characteristics at low speed and the application premises of similarity theory, a method for extrapolation of compressor characteristics based on improved exponents of similarity theory was put forward with considering the difficulties in predicting low-speed characteristics of the compressor. As a result, low-speed characteristics curve of the compressor was fitted. Ultimately, the starting model of 4MW grade gas turbine was constructed with the low-speed characteristics.Furthermore, after carefully studying modules of the gas turbine components, we carefully studied the impacts of different loads on shaft speed, power generation as well as the temperature, pressure and flow rate of every component through the mathematical modeling with the experimental data. Also, through the starting model with the extrapolation data, we deeply researched the impact of different power of starters on shaft speed, outlet temperature of turbine and outlet temperature of gas turbine. The results showed that different loads had important effect on inlet temperature of turbine, outlet temperature of turbine, outlet temperature of gas turbine and output power of gas turbine. It also turned out that the speed of gas generator changed faster and outlet temperature of gas turbine became lower with higher starter power.In view of the profound influence of fuel control law on the performance of gas turbine, the principle of fuel control system of 4MW grade gas turbine was analyzed. Further,4MW grade gas turbine fuel control system, which was composed of starting control, shutdown control, gas turbine speed control, power turbine speed control, temperature control and acceleration control subsystem, was designed based on speed closed loop control and multi-channel low selection control principle.