| Popis: |
Quasi-transpiration cooling schemes such as Double-Wall Effusion Cooling allow the Nozzle Guide Vanes of High Pressure Turbines in modern aeroengines to experience high heat loads whilst maintaining acceptable temperatures. The combination of impingement, pin-fin and effusion cooling in such schemes produces a high convective cooling efficiency, but this is accompanied by large pressure losses that increase vulnerability to coolant migration toward low pressure regions. This can have severely detrimental effects on cooling performance as effusion holes around the Leading Edge can be starved of coolant, producing no local film cooling protection. This paper presents a Low Order Model (LOM) which rapidly produces pressure, temperature, mass and heat flow distributions throughout Double-Wall Effusion Cooling Schemes, developed from a previously presented Mass Flow Network LOM. These can be found for a variety of flow and geometric conditions, allowing fast analysis of cooling designs. Experiments were conducted using a steady-state facility, from which results were used to validate the new LOM to a satisfactory standard. Using specifically derived dimensionless groups for coolant migration, results from the LOM demonstrate the effect of heat transfer on it as well as the effects of coolant migration on the cooling performance, highlighting design guidelines to reduce such effects and to optimise the component life. |
