Kevin Michael Elward

Shock Formation in Overexpanded Tip Leakage Flow

Shock formation due to overexpansion of supersonic flow at the inlet to the tip clearance gap of a turbomachine has been studied. The flow was modelled on a water table using a sharp-edged rectangular channel. The flow exhibited an oblique hydraulic jump starting on the channel sidewall near the channel entrance. This flow was analyzed using hydraulic theory. The results suggest a model for the formation of the jump. The hydraulic analogy between free surface water flows and compressible gas flows is used to predict the location and strength of oblique shocks in analogous tip leakage flows. Features of the flow development are found to be similar to those of compressible flow in sharp-edged orifices. Possible implications of the results for high-temperature gas turbine design are considered.Copyright

Massive Steam Injection on an MS6001B Gas Turbine in Cogeneration Service

A recent field test has completed the qualification of the MS6001B combustion system for operation on gas fuel with steam injection for NOx control to 25 ppmvd. Recently, dry operation on gas fuel at 25 ppmvd has been achieved on the MS6001. To meet the immediate need for running at the 25 ppmvd NOx level, increased steam injection was investigated. Laboratory testing on a single MS6001 combustor indicated the potential for achieving NOx levels as low as 25 ppmvd through the use of steam injection. This paper describes the lab testing and the field test of the MS6001B, and includes data on emissions, steam flow requirements, and dynamic pressure levels. The MS6001B is now available at 25 ppmvd NOx with steam injection on gas wherever this level is required. This system provides an easy retrofit to those gas fired, steam injected units where installation of the dry 25 ppmvd NOx system is not immediately feasible.Copyright