Experimental Study of Particle Deposition on Surface at Different Mainstream Velocity and Temperature

Fei Zhang,Zhenxia Liu,Yanan Liu,Zhengang Liu

doi:10.3390/en12040747

Abstract

The effect of mainstream velocity and mainstream temperature on the behavior of deposition on a flat plate surface has been investigated experimentally. Molten wax particles were injected to generate particle deposition in a two-phase flow wind tunnel. Tests indicated that deposition occurs mainly at the leading edge and the middle and backward portions of the windward side. The mass of deposition at the leading edge was far more than that on the windward and lee sides. For the windward and lee sides, deposition mass increased as the mainstream velocity was increased for a given particle concentration. Capture efficiency was found to increase initially until the mainstream velocity reaches a certain value, where it begins to drop with mainstream velocity increasing. For the leading edge, capture efficiency followed a similar trend due to deposition spallation and detachment induced by aerodynamic shear at high velocity. Deposition formation was also strongly affected by the mainstream temperature due to its control of particle phase (solid or liquid). Capture efficiency initially increased with increasing mainstream temperature until a certain threshold temperature (near the wax melting point). Subsequently, it began to decrease, for wax detaches from the model surface when subjected to the aerodynamic force at the surface temperature above the wax melting point.

Highlights

Aero-engines would encounter particle laden air flows when operating in environments with a high concentration of airborne particles during extended service
Mainstream velocity through the wind tunnel was set to investigate its effect on the particle deposition mass and efficiency
Nine series of tests were conducted in a two-phase flow wind tunnel to investigate the

Summary

Introduction

Aero-engines would encounter particle laden air flows when operating in environments with a high concentration of airborne particles during extended service. A majority of particles flow through the combustion along the main channel flow, and subsequently attack the hot component surface through deposition. Particles may flow through the engine without any effect, or impact on the surface by means of rebounding, spreading, spattering or adhering [1,2,3], possibly experiencing phase transition and deposition afterwards. Deposition on the turbine blade would dramatically increase the surface roughness and block film cooling holes in certain conditions, which could lead to a loss in aerodynamic and cooling efficiency [4,5]. For land-based gas turbines, trace amounts of foreign matter in fuels and carbon microparticles generated from the burning of raw energy sources can be injected into the turbine along with the main flow and subsequently deposited on the blade surface, which will affect its heat transfer characteristics and aerodynamic performance

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