Particle/blade Impact Study of Near-Transonic Compressor in Engine Test

Compressor blade/particle interactions and erosion are studied using a Rolls-Royce M250-C20B turboshaft engine in an instrumented engine test cell. A novel experimental dataset was produced, yielding a qualitative visualization of particle impact regions on blades and vanes of an on-engine full six-stage axial compressor at near-transonic tip speeds for three different particle compositions and two different corrected characteristic particle Stokes numbers. This data was collected using a novel modification of existing surface coating visualization methods, and contributes the first experimental dataset of its kind for a rotational frame at nominal blade tip Mach numbers of 0.85. As part of a multidisciplinary research program involving Virginia Tech, Rolls-Royce, Pratt & Whitney, and the US Office of Naval Research, a novel advancement has been made to existing methods used to study particle/surface impacts inside the compressor of a full gas turbine engine. The simple method provides useful insights into the mechanics of cold-section degradation without incurring the cost of measurable engine degradation. Dust ingestion at the desired engine operating point results in preferential removal of an impact visualization coating at locations where particle impacts occur, providing a spatially resolved visualization of particle impact regions across stages and on both rotating and non-rotating components. In separate tests, particles of varying size and material were ingested at high engine power under nearly equal conditions, yielding evidence that for 100 μm particles, the majority of particles impact the first-stage rotor and particle centrifuging is primarily limited to the first two stages. Particle impacts on the first-stage rotor seem to have a first-order dependence on the corrected Stokes number. These observations provide insights into the underlying dominant mechanisms and expose opportunities for future fundamental modeling research. In addition, this study serves as a unique case study highlighting how qualitative indicators of particle/engine interactions in a real engine can provide valuable insights without requiring costly degradation to engine performance or lengthy engine test campaigns. This test methodology enabled nine separate particle ingestion engine tests to be completed within the span of one year, each of which provided useful information for the program. The results can guide the broader engine test research community toward reduced-cost engine testing, which maximizes learning for the complex problem of gas turbine engine particle ingestion and opens new opportunities for thorough full-scale engine research. The findings of this research effort will also aid advancements in the accuracy of particle ingestion models by serving as a first-order experimental validation dataset, ultimately supporting improvements to the safety, durability, and flight readiness of aircraft gas turbines.