Investigating endwall-blade fillet radius variation to reduce secondary flow losses.

摘要

In turbomachinery the joint between a turbine blade and the endwall often involves a fillet.udPrevious studies show that this fillet significantly influences the secondary flows despite regularlyudbeing omitted from simulation and testing, specifically that a uniform fillet radius of 16%udaxial chord increased endwall losses by 10%. It was proposed that a variable radius fillet couldudreduce secondary flows and the associated endwall losses. This paper describes a computationaludstudy to determine what variable radius fillet is required for optimal performance in theudcascade. The variable radius fillet ranges from 0.5% to 16% of axial chord and was found usinguda genetic algorithm optimisation. Although this is a computational study the design offersudphysically plausible mechanisms by which the extra losses introduced by fillets may be reduced.udThis paper also suggests a generalised rule of fillet radius variation to minimise endwall losses.udA large radius is required on the leading edge that reduces slowly along the pressure side butudrapidly on the suction side such that the smallest permitted radius is applied to the suction side.udA medium radius is required at the trailing edge.