Comprehensive Assessment of Internal Deposition on an Impingement Cooling Circuit at Engine Relevant Temperatures

A new deposition cooling facility was designed and constructed to examine the time-evolution of dust deposition and its effect on the cooling effectiveness of internal cooling circuits typical of gas turbine hot sections. The facility utilizes representative gas turbine engine cooling geometries and operates at relevant coolant and hot gas flow temperatures (650K and 1300K respectively). A combustion chamber is used to create a high speed (180m/s) 2cm diameter jet that impinges at a 26° angle (from the horizontal) onto a pre-oxidized flat plate made from a nickel-based alloy. The backside of this plate is cooled by an array of 0.5mm diameter impingement cooling jets with a 1.03 pressure ratio relative to the hot jet discharge pressure. An infrared camera is used to record the surface temperature of the flat plate as airborne dust is delivered through the cooling circuit. The dust delivered to the test article is 0-5micron Arizona Road Dust. Deposit evolution and cooling effectiveness trends were observed by performing successive tests with varying dust delivery period while maintaining constant dust loading (concentration). Observable patterns in the deposit behavior corroborate quantitative measurements of changes in local cooling effectiveness as measured by the IR camera. A limited test series at lower coolant and jet temperatures highlights the role of temperature in the deposition process.