Transport of Particulates in an Internal Cooling Ribbed Duct

Abstract

A ribbed square duct (P∕e=10, e∕Dh=0.10) subjected to sand ingestion is studied using large-eddy simulations (LES). Particle sizes of 10μm, 50μm, and 100μm with nondimensional response times (normalized by friction velocity and hydraulic diameter) of 0.06875, 1.71875, and 6.875, respectively are considered. The calculations are performed for a nominal bulk Reynolds number of 20,000 under fully-developed conditions. Distributions of impingement density, impingement velocities and angles, together with fractional energy transfer are presented for each surface. It is found that about 40% of the total number of 10micron particles are concentrated in the vicinity (within 0.05 Dh) of the duct surfaces, compared to 25–30% of the 50 and 100micron particles. The 10micron particles are more sensitive to the primary and secondary flow velocities than the larger particles. While the 10micron particles exhibit high energy transfer to the surface near the rib side-wall junction and immediately upstream of the rib, the larger particles exhibit more uniform distributions. The largest fraction of incoming particulate energy is transferred to the front face of the rib and is between one to two orders of magnitude larger than the other surfaces. As particle size increases, substantial particle energy is also transferred to the back face of the rib by particles bouncing off the front face and carrying enough momentum to impinge on the back face of the preceding rib.