Effect of Particle Size and Trench Configuration on Deposition From Fine Coal Flyash near Film Cooling Holes

Abstract

Particulate deposition experiments were performed in a turbine accelerated deposition facility to examine the effects of flyash particle size and trench configuration on deposits near film cooling holes. Deposition on two bare metal Inconel coupons was studied, with hole spacings (s/d) of 3.4 and 4.5. Two sizes of sub-bituminous coal ash particles were used, with mass mean diameter of 4 and 13 μm, respectively. The effect of a cooling trench at the exit of the cooling holes was also examined in this deposition facility. Experiments were performed at different angles of impaction. Particles were accelerated to a combustor exit flow Mach number of 0.25 and heated to 1183 °C before impinging on a target coupon. The particle loading in the 1-h tests was 160 ppmw. Blowing ratios were varied in these experiments from 0 to 4.0. Particle surface temperature maps were measured using twocolor pyrometry based on RGB signals from a camera. Deposits generated from finer particles were observed to stick to the surface more tenaciously than larger particles. The capture efficiency measured for the small particles was lower than for the larger particles, especially at low blowing ratios. However, the finer particles exhibited a greater variation in deposition pattern as a function of hole spacing than seen with larger particles. The effect of trench configuration on deposition was examined by performing deposition tests with and without the trench for the same hole spacing and blowing ratio. The effects of trench configuration on capture efficiency, deposition pattern, and surface topography are reported. Deposition experiments at impingement angles from 45°to 15°s howed changes in both deposit thickness and temperature. The trench increased cooling effectiveness, but did not change the particulate collection efficiency because the trench acted as a particulate collector.

Experimental Investigation of Particulate Deposition on a Simulated Film-Cooled Turbine Vane Pressure Surface in a High Pressure Combustion Facility

“…affect the evolution of deposits. As discussed earlier, the TADF, developed at BYU, has been employed to perform numerous studies of the factors affecting deposition ([6], [10], [14], [15], [16], [17], [18], and [19]). Bons et al [6] performed a study examining the deposition from four different materials: straw, sawdust, coal and petroleum coke (petcoke).…”

Simulations of Multiphase Particle Deposition on Endwall Film-Cooling Holes in Transverse Trenches

“…The method developed by Jensen et al [7] was later used by Ai et al [13] who used the TADF to observe deposition and its effects on trenched film-cooling holes at various impingement angles. Without deposition, the trench improved cooling at shallow impingement angles; however, during deposition simulation, particles accumulated inside the downstream lip of the trench leading to hole blockage and reduced cooling.…”

Experimental Study of Sand Particle Deposition on a Film-Cooled Turbine Blade at Different Gas Temperatures and Angles of Attack

“…It was found that the deposition rate increased with increasing gas temperature and particle size. Ai et al [12] explored the effects of particle size on deposition by using a flat plate with film-cooling holes angled at 45 • . Bonilla et al [13] further explored the particle size effect on the CFM56-5B nozzle guide vane.…”