Effect of Blowing Ratio on Early Stage Deposition of Syngas Ash on a Film Cooled Vane Leading Edge Using Large Eddy Simulations

Abstract

A numerical study is performed to investigate the deposition of Syngas ash in the leading edge region of a turbine vane. The leading edge of the vane is modeled as a symmetric semicylinder with a flat afterbody. Three rows of coolant holes located at stagnation and at آ±21.3 deg from stagnation are simulated at blowing ratios of 0.5, 1.0, 1.5, and 2.0. Large eddy simulation (LES) is used to model the flow field of the coolant jetmainstream interaction and Syngas ash particles are modeled using a discrete particle method. The capture efficiency for eight different ash compositions of particle sizes 5 and 10 microns are investigated. Under the conditions of the current simulations, both ash particles have Stokes numbers less than unity and hence are strongly affected by the flow and thermal field generated by the coolant interaction with the mainstream. Because of this, the coolant jets at stagnation are quite successful in pushing the particles away from the surface and minimizing deposition in the stagnation region. Among all of the ash samples, the ND ash sample shows the highest capture efficiency due to its low softening temperature. For the 5 micron particles, when the blowing ratio increases from 1.5 to 2.0, the percentage of the capture efficiency increases as more numbers of particles are transported to the surface by strong mainstream entrainment by the coolant jets. The deposition results are also estimated using the discrete random walk (DRW) model and are compared to that obtained from the LES calculations. For both particle sizes, the DRW model underpredicts the capture efficiency when compared to the LES calculations and the difference increases with the increasing blowing ratio and decreases with increasing particle size.