The Effect of Particle Loading, Size, and Temperature on Deposition in a Vane Leading Edge Impingement Cooling Geometry

Abstract

Experiments have been performed to assess the effects of particle loading, size, and temperature on flow blockage development in a geometry representative of a gas turbine nozzle guide vane leading edge. Tests with Arizona Road Dust in 0–5, 0–10, and 0–20 micron nominal size distributions showed that particle loading rates had no substantial impact on flow blockage development over the 700–866 K temperature range. Tests with the 0–10 micron dust at various flow temperatures indicated a first order effect of temperature on blockage development, particularly for temperatures above 700 K. Testing with 5–10 and 10–20 micron size distributions revealed a clear distinction between the effects of different particle sizes. Evaluation of the experimental data and particle size distributions indicated that particles smaller than 3.25 microns were primarily responsible for blockage development, a result which was further corroborated using a physics-based deposition model. Particles larger than 5 microns were shown to produce a removal mechanism, both for deposits that are in the process of growing and for those which are already established. Overall, the experiments indicate that comparisons between laboratory scale deposition studies and data from field serviced engine hardware can be reliably made in spite of large variations in the rate of particle loading. However, parameters such as flow temperature and particle size should be closely matched when performing experiments, as these have a first order effect on blockage development.