The discharge coefficient of an orifice is a function of both geometric and flow effects, such as inlet corner radius, orifice length, inlet velocity orientation, and Reynolds number. Loss characteristics are available for each of these effects; however, a need exists for a reasonable method of predicting the discharge coefficient with an arbitrary combination of the above effects. Presented is a technique for calculating the discharge coefficient for arbitrary geometry with results compared to test data.

The surface frictional characteristics of a labyrinth seal can result in significant windage power dissipation for high speed seals. Recent advances in seal design have produced high speed, high pressure labyrinth seals which operate at very low leakage rates. The reduced leakage is beneficial to gas turbine efficiency, but seal discharge temperatures can approach material design limits with high windage power dissipation. Also, a high air temperature rise can influence seal leakage flow. Consequently, the general assumption of negligible rotational effect on leakage is not always valid. A method is presented for the prediction of seal power dissipation and leakage flow over a wide range of design parameters. Results are compared to available test data and several approaches examined for the reduction of seal windage.

Typically cooling air must be metered into cavities bordering turbine disks to offset cavity air temperature rise due to windage generated by air drag from rotating and stationary surfaces and the ingestion of hot mainstream gas. Being able to estimate the minimum amount of cooling air required to purge turbine rim cavities accurately is important toward providing optimum turbine cycle performance and hardware durability. Presented is an overview of a method used to model windage rise and ingestion on a macroscopic scale. Comparisons of model results to engine test data are included.

A practical system for flow measurement in rotating seals using the injection and sampling of a tracer gas is presented. Carbon dioxide or helium is injected as a tracer into a labyrinth seal at a controlled rate and gas samples are extracted downstream for concentration measurement. Test results from a rotating labyrinth seal rig were obtained over a range of seal pressure ratios and rotor speeds in order to determine the conditions which assure optimum tracer gas mixing. Seal leakage rates calculated by tracer gas concentration are compared to venturi flow measurements.

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