A study on liquid film and evaporation characteristics of fuel jet impingement on the scorching wall of evaporation tube for gas turbine

Abstract

The phenomenon of liquid jet impingement forming a liquid film on a wall has extensive applications in aerospace engineering. A numerical approach to simulate the impingement of fuel jets on the scorching wall inside the evaporation tube of a gas turbine is employed in this work. The effects of the inlet air Reynolds number, the fuel mass flow rate, and the fuel injection angle on the characteristics of evaporation, flow field structure, and film development within the tube are discussed. The results indicate that an optimal inlet air Reynolds number of 49 000 and an optimal injection angle of 30° maximize the evaporation rate to 90.83% and 83.01%, respectively, and that the evaporation rate decreases as the fuel mass flow rate increases. A semiempirical evaporation model of the evaporation tube Evap=e0.2853×Reair,in0.2935× AFR0.6079×α−0.1662 is proposed. Moreover, a valley-shaped low-speed zone, referred to as the retarding effect, is observed inside the tube; its range and intensity are quantitatively described and related to the phenomenon of film separation. As the inlet air Reynolds number increases, the likelihood of film separation and the film surface velocity both increase, delaying the separation point. The fuel mass flow rate has little effect on the film surface velocity, but a decrease in the fuel mass flow rate results in a thinner film, making it more prone to separation. For fuel side injection, as the fuel injection angle increases, the film thickness becomes more uneven, and the influence of the retarding effect behind the jet increases, promoting film separation.