Effects of Turbine Blade Tip Clearance on Turbocharger Performance: An Experimental Investigation

Rising fuel costs and increasingly stringent emission standards push engineers to develop more efficient turbo-machinery. Reducing turbocharger turbine tip clearance is one method of improving turbine performance, thereby improving overall engine operation. By using tip seals or abradable seals, reduction of this clearance is possible. Metco 314 NS material was applied to an Elliot-H type turbocharger turbine shroud to reduce the cold clearance from 0.762 mm (0.030 inch) to 0.457mm (0.018 inch). Two separate yet virtually identical performance tests were conducted at speeds of 13,000 rpm, 15,000 rpm, and 17,000 rpm on the turbocharger. The first test established the efficiency condition of the turbocharger with the tip seal installed. The second was to quantify a decrease in efficiency, if present, after the tip seal was removed. Both tests were conducted as identically as possible. The average amount of available energy not utilized with the tip seal removed was 30.26 kW at 13,000 rpm, 51.42 kW at 15,000 rpm and 45.71 kW at 17,000 rpm.