Numerical Study Of Air Cooled Turbine Blade With Crossed-rib Structure

The research on traditional single cooling structure is relativelymature, while the real blade typically combines multiple coolingstructures to strengthen the blade heat transfer. When a variety of coolingstructures are integrated into a blade，the interaction of coolant flow ininternal cooling passage makes it complicated to analysis the air flow andheat transfer. Therefore, it is necessary to do researchs on complex flowand heat transfer characteristics in a complete blade. The work of thispaper is using commercial software CFX to numerically investigate crossrib structure used in a low pressure turbine blade as well as the integratedturbine blade. Conjugate heat transfer method is used to get an accurateblade temperature distribution with unstructured tetrahedral meshes.This paper numerically investigated the influence of width-to-pitchratio (t/p) and rib incline angle β upon heat transfer and total pressure lossof trapezoid grid-ribbed channel. Six different models were used to studythe flow and heat transfer under eight conditions. Reynolds number wasranged from3300to66000. The results showed that：The Nusselt Number and flow resistance coefficient of the channels with slots wereincreased with increasing rib width-to-pitch ratio (t/p) and rib inclineangle β; while the synthetical effect of the heat transfer was decreasedwith increasing rib width-to-pitch ratio (t/p) and rib incline angle β. Thechannels without slots got the highest heat transfer coefficient, but itcaused highest total pressure drop; the channels with slots had moresignificant effects on the whole heat transfer enhancement.This paper described3D numerical simulations of a turbine rotorblade with complex internal cooling structure. The cooling structureconsists of a lattice work cooling channels with rib angle at30°in thefront of blade, cross rib cooling channels with rib angle at45°in the backpart and film holes at the trailing edge. Changing internal coolingstructures, such as a hollow blade, a straight channel, a slotted cross riband a composite cross rib channel blade were studied. Blade temperaturewere decreased with increasing coolant mass flow; the channels with slotshad significant effects on reducing pressure loss；when compared with theblade having straight channel, the blade with structure of cross rib cooling had more uniform mass flow of cooling air flowed out of film coolingholes. The temperature distribution of composite cross rib blade surface isuniform along the circumference. The blade with internal structureseparated by clapboard had better cooling effect on the top of blade thanthe one had lattice work.At last, the effect of different rib size on cooling efficiency of bladewith composite rib were simulated by changing structure size of45°crossrib. The results showed that the blade with composite rib had a significantdecline on blade temperature, but no remarkable drop on the top regine ofblade; the whole cooling performance changed a little when increased ribsize of45°cross rib which had important significance on simplifyingcooling blade structure. Through the comparative study of differentcooling schemes, advantages and disadvantages of cooling structure usedin low pressure turbine blade were analyzed which indicated aoptimization direction on cooling structure.