VEIL COOLING OF RADIAL-FLOW TURBINES.
GARRETT CORP LOS ANGELES CALIF AIRESEARCH MFG DIV
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Effective reduction of turbine rotor temperatures in gas and turbocharger turbines has been a subject of research for decades. Air-cooled hollowed blades and disks are now in production for aircraft axial gas turbine wheels, allowing higher gas temperatures with given materials. However, relatively little research has been done on radial turbine wheel cooling, even though this turbine type is now produced in larger numbers. Cooling passages in radial turbine wheels are quite conceivable, but veil cooling, the subject of this study, appears by far the simplest solution, considering the design requirements. The introduction of coolant air used in this project represents one of many approaches, and was selected to make accurate study possible. The application to back-to-back rotor configurations with limited air flow to the turbine wheel side and simplified circumferential seals appears quite attractive for gas turbines as well as turbochargers. The main objective of the present study phase was to obtain accurate material temperatures on the blades and disk of a semi-shrouded radial inflow turbine wheel at reasonably high gas temperatures, tip speeds, and expansion ratios, and thereby assess the true merits of veil cooling in its simplest form. Author