Preliminary Experimental Investigation of Initial Onset of Sand Deposition in the Turbine Section of Gas Turbines

Abstract

Particle ingestion into modern gas turbine engines is known to reduce performance and may damage many primary gas path components through erosion or deposition mechanisms. Many studies have been conducted that evaluate the effects of particulate ingestion in primary and secondary gas path components. However, modern gas turbines have gas path temperatures that are above most previous studies. As a result, this study performed particle deposition experiments at the Virginia Tech Aerothermal Rig facility at engine representative temperatures. Arizona Test Dust of 20 to 40 μm was chosen to represent the particle ingested into rotorcraft turbine engines in desert and sandy environments. The experimental setup impinged air and sand particles on a flat Hastelloy X coupon. The gas and sand mixture impacted the coupon at varying angles measured between the gas flow direction and coupon face, hereby referred to as coupon angle. For this study, gas and sand particles maintained a constant flow velocity of about 70 m/s and a temperature of about 1100°C. The coupon angle was varied between 30° to 90° for all experiments. The experimental results indicate sand deposition increased linearly from about 975 °C to 1075 °C for all coupon angles. A multiple linear regression model is used to estimate the amount of deposition that will occur on the test coupon as a function of gas path temperature and coupon angle. The model is adequate in explaining about 67% of the deposition that occurs for the tests. The remaining percentage could be explained with other factors such as particle injection rates and exact surface temperature where the deposits occur.

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

“…(6) At the end of an experiment, the wax spray system, air heater for the wind tunnel and axial fan need to be turned off successively. (7) The test model was moved away from the wind tunnel to be photographed. The wax depositions from the entire leading edge, windward side, and lee side were collected to measure the wax deposition mass, respectively.…”

“…In addition, a growing number of impurities are found in the urban environment, indicating more particles flow into the combustion along the turbine cascade passage once ingested into the engine. This could shorten part life and increase the risk of operation failure [6,7]. 2 of 18 To date, the deposition of sand and coal ash on gas turbine engines has been studied by multiple researchers.…”

A Simple Model to Assess the Role of Dust Composition and Size on Deposition in Rotorcraft Engines

“…The substrate temperature also plays a large role, as does the level of turbulence, the degree of cooling and the water content of the combustion products. Once the accumulation process has started, there is evidence to suggest that the deposition rate is non-linear [13]. The physical processes responsible for this are not yet fully understood.…”

Experimental investigation of the onset of sand deposits on Hastelloy-X between 1,000°C and 1,100°C

“…The test equipment was repurposed for high-temperature particle tracking studies by quantifying the coefficient of restitution (14,15) . The most recent study was for ARD deposit accumulation for very high sand loading and concentrations (16) . Figure 1 is a rendering of VTAR's current configuration for sand deposition testing.…”

“…In addition, the particles typically entering the hot section of a turbine engine have a mean diameter less than 10 μm (19) . However, the ARD sizing used for this study improves the detection of deposited particles for post-test image processing and analysis as well as allowing a comparison to previous and potentially future deposition studies at Virginia Tech (14)(15)(16) .…”