Numerical Study Of Aeroderivative Gas Turbine Combustor And Outlet Temperature Of The Flue Gas Quality Improvement

Gas turbines are of considerable interest for power generation in the industrial sectors for many reasons including high system efficiency, less investment, minimal onsite construction, and low emission products.Gas turbine engines have been used widely in power production, ship and mechanical drive for many years in industrial countries. Requirements for power generation by land-based gas turbines are increasing dramatically in recently years in China for the purpose of environmental protections. Among various applications of gas turbines, aero-derivative industrial gas turbines have attracted extensively attentions for its shorter design cycle, lower risk and cost, higher performance and reliability.In order to further understand the combustion characteristics in combustor and optimize aero-derivative industrial gas turbines design,fundamental research on this issue is still needed, modeling can play a significant role in achieving these objectives. In this paper, the combustion characteristics of aero-derivative industrial gas turbines combustor have been three-dimensional numerically investigated, advices on the air injection to improve exit temperature quality are presented. The combustion chamber under study is a KW gas turbine form a power plant. The gas turbine combustor is reconstructed by PRO-E software and the grids are generated using GAMBIT software. Finer girds are located in the primary zone where strong reaction is expected, as well as the air entrances where the physical properties change more dramatically. Total amount of 123 grids were used, and grid independence has been checked.The mathematical equations are based on the conservations of mass, momentum, and energy with other equations for the turbulence and combustion. The steady-state Navier-Stokes equations with appropriate boundary conditions were solved using finite-volume method and SIMPLE algorithm. The simulations were performed with three-dimensional k-?turbulent flow model and probability function density(PDF) for chemical reaction. Gas mixtures radiation is considered in the model and computed by DO model. The SIMPLE algorithm is used to handle the pressure and velocity coupling.Firstly, the combustion,flow, heat transfer in the combustor under the design condition is simulate and discussed. The predictions show that, for the design condition, the flame is stabilized in the core region of the primary zone since the fuel and air mixes rapidly in the recirculation zone. Our model successfully predicts this phenomenon. This type of recirculation promotes better mixing and it has been widely used in industrial gas turbine combustor. The highest temperature in the primary combustion zone is around 2376 K. Going downstream, temperature decreases due to air-cooling and dilution. Then a slight increase in mixture temperature is observed downstream the mixing hole zone, this is attributed to the combustion of the unburned gas after injecting the air.Secondly,to improve the exit temperature quality and optimize the air injection, the simulation is performed. Attention is focused on the effects of cyclone installation angle, cone ring hole angel, mixing hole intake air ratio on combustion characteristics and exit temperature. It is indicated that exit temperature quality improves with moderate decreasing the cyclone installation angle, cone ring hole angel and increasing the main hole intake air ratio, and that the high temperature region slightly shifts to the upstream.Finally,an improved air injection method is proposed and the numerical results of the proposed method for the gas turbine combustors are presented. Results shows that the outlet temperature quality improves, the average temperature and hot temperature decrease;the average temperatures, hot temperature, OTDEand RTDF of the combustor outlet decrease from 1278 K, 1409 K, 0.2025, 0.1167 to 1239 K, 1358 K, 0.1968 and 0.1039, respectively.The predicted numerical results of design condition and the proposed advices on improved air injecting method provide guidelines for the design of the combustor and some indications for further improving the combustor performances.