The Design Of Dual-fuel Gas Turbine Nozzle And Combustion Flow Field Numerical Simulation

Chemically recuperated gas turbine (CRGT) can make full use of the exhaust heat to enhance the thermal efficiency and output power, reduce the emission of exhaust gas NOx and get high-quality pyrolysis fuel. The working mode of CRGT determines to install dual-fuel combustion system in the combustor. So, CRGT not only asks combustion for the function to separately burn fuel or pyrolysis gas, but also requires it to burn them at the same time. Nozzle, as a key component of the combustor, whose performance will directly affect the performances of ignition, combustion efficiency, combustion stability, temperature distribution and exhaust pollution as well as the life of flame tube and turbine blades. So in regard to the transformation of the fuel combustor and the achievement of CRGT cycle, it is critical to design a dual-fuel nozzle which can shorten the flame length, cool the wall of flame tube and keep the exit at a moderate temperature to match with the combustor with dual-fuel combustion system.This paper, under the premises that the nozzle's interface size, the structure of the flame tube and the enthalpy value in the exit of the combustor remain stable, designs a set of new dual-fuel nozzle for CRGT combustor and enables it to combust liquid fuel or pyrolysis gas separately, but also mixed fuel. Then the numerical simulation in regard to the combustion flow fields of the combustors was carried out with the aid of CFD method and finally the contrastive analysis was made. In the numerical simulation, RNG k-εturbulence model, Realizable k-εturbulence model and PDF combustion model were applied; the upwind scheme was used to disperse the equations; the SIMPLE algorithm method is applied to solve the equations.When the dual-fuel nozzle structure was designed in this paper, gas channel swirler vane, gas pore, guided flow dome were tried and made them optimization and integration. In order to validate and optimize the proposed design, the paper draws support from CFD technology to make numerical simulation and comparative analysis to the combustion flow fields in the combustors in which the nozzles'structure and the position of assembly are different. According to the contrast of these nozzle structure models'flame length, position of the high temperature zone, wall temperature and the evenness of exit temperature field as the key influencing factors of the combustor, we could know that the gas swirling dual-fuel nozzle with oblique holes, on the one hand, can produce preswirl flow in the gas channel to enable a better mixing of the pyrolysis gas and air; on the other hand, can protect the nozzle and the wall of flame tube from fire and keep the exit temperature in a moderate level.At the last part of this paper, through comparing the performances of combustor by using RNG k-εturbulence model and Realizable k-εturbulence model, we know that different turbulence models can make great influence to the numerical simulation.