Capacity Enhancing Design Of9FA Heavy-load Gas Turbine And Numerical Study On The Third Cooling Structure

Since the advent of the gas turbine, it had been widely used in aerospace,mechanical power and so on, and it plays an important role in our industrialconstruction and national economic construction. With the rapid development andthe quick replacement of gas turbine, gas turbine, as a kind of power mechanicaldevices, reflects a country’s overall level of industrial technology. The efficient gasturbine technology had also been included in national development priorities of thekey technologies.In this paper, the capacity of the9FA unit was researched. Removing the powerconsumption of the compressor and other components, the rated output power of theunit was267MW. By rising the capacity of the original unit, the unit power wasrequired to reach300MW. On the basis of this unit, the new unit kept the inlet totaltemperature, total pressure and outlet static pressure as same as the original andchanged its area of the meridional plane which increased the output power.According to this capacity enhancing design, the aerodynamic calculation of initialmodification was completed. Firstly, the new program absorbed and inherited theprototype turbine structure, referring to the overall design of the prototype turbineand air distribution on the overall design. According to the9FA turbine, the new unitcontained three stages of turbine, ensuring the average diameter unchanged and thestructure of the turbine wheel in unaltered condition to ensure the reliability of theturbine and increasing its area of the meridional to meet the requirement of the massflow; secondly, on this basis, adjustments to optimize the profile, and optimizing forinterstage matching, they were to improve the performance of the unit. By thecapacity design, the mass flow of gas increases10%, which basically met therequirements of power. But with power allocation coefficient of each stageschanging, the inlet total temperature changed. In this new conditions, the unit losscaused by profile increased and the overall efficiency decreased by0.4%. Usingisight optimization platform and S2forward problem calculation program andselecting the appropriate optimization scheme, the profile of the original unit wasoptimized to adapt to new working conditions. One scheme used genetic algorithmsand S2calculation program and the other used annealing algorithm and approximatemodel. By comparison of the results, the final optimization scheme were determined.The results showed that after changing the area of the meridional plane, the massflow of gas increased10percent, total temperature before the stage changing, theoriginal unit loss of the profile increasing with the efficiency decreasing by0.4%;Through taking the constraints of mass flow changing by±1%, machine efficiency increased by0.57%. Compared with the unit before the modification, the turbinepower increased to574MW from the521MW, increased10.17%. The new designmet the design requirements.Due to the height increase of the blade which leaded by the flow areaincreasing, referring to9FA blade cooling structure, the new cooling structuraldesign was done. Determined the retrofit design of the profile, taking into accountthe gas flow rate increasing and total temperature before the stage changing, the9FAoriginal cooling solution should be assessed again. For example, to the third stageturbine, its working status was simulated by using CFX software. Compared theaerodynamic and heat transfer conditions before and after retrofit turbine, in order toimprove the cooling effect of the third stage stator, spoilers was added on the innersurface of the radial cooling channels, so as to enhance heat transfer. Comparingblade surface cooling heat transfer coefficient and nusselt coefficient between fourkinds of Oblique spoiler cooling solutions and two kinds of straight spoiler coolingsolutions, analyzing heat transfer between45degrees,60degrees,90degrees ofintermittent spoilers and normal spoilers, finally the program of90degrees normalspoilers was selected as the final cooling program. According to the numericalsimulation results, with90degrees straight ribs, the maximum surface temperatureof the blade was down to1131K, Lower than1145K of the pre-capacity. Andtemperature distribution was also within a reasonable range, to ensure the life of theturbine after compatibilization.