Numerical Study on the Characteristics of Lean Direct Injection Combustor With Elevated Fuel Temperatures

Abstract With the development of high performance gas turbine engines, the temperature before turbine is rising and it presents a serious challenge to existing thermal management. It is very attractive to use fuel as the cooling medium for gas turbine engines. For this purpose, the effects of fuel temperature on combustion characteristics are urgently needed to be understood. In this work, the characteristics of lean direct injection (LDI) combustor is simulated by changing the physical properties of fuel with different temperatures. The predictions of gas phase and droplet velocity, droplet diameter are compared well with the experiment data. The numerical results show that as fuel temperature rises, the droplet evaporation rate and mixing efficiency of fuel and air in non-reacting case is improved significantly, the spray angle, concentration and distribution profile of fuel in reacting case are enlarged as well. When fuel temperature is raised from 350K to 550K, the peak value of droplet evaporation rate at the vicinity of nozzle is increased by 26.7 times, the uniformity index downstream of the primary recirculation zone (PRZ) is increased by 2.57%, the axial length and maximum negative axial velocity of PRZ are reduced by 13% and 21%. The average temperature and NO emission at combustor outlet are increased by 1.99% and 48.15%, the mass fraction of CO is decreased by 5.45%. Besides, the number, diameter, and distribution space of droplets are decreased sharply. The formation of premixed flame and propagation of high-temperature region are promoted, the flame front is changed from a conical shape to a recessed shape. The combustion efficiency can be improved by increasing fuel temperature. The present study is expected to provide insightful information for understanding characteristics of LDI combustor with elevated fuel temperatures.