The Integrated Gas/Steam Nozzle With Steam Cooling: Part II — Design Considerations

Abstract

The integration of multiple steam nozzles with the first-stage annular-gas nozzle to form a binary-flow system in a reheat-gas turbine is presented whereby steam is first used as an internal vane coolant before being expanded and accelerated for work extraction. Steam nozzles are located in “fat-body” type vanes. Trailing-edge impingement followed by reverse-serpentine-flow cooling takes place. Internal trailing-edge-steam nozzles produce either diffusion or shock-wave boundary-layer disturbance inside the trailing edge to enhance heat transfer. Externally, steam blanketing reduces nozzle-profile loss and improves film cooling effectiveness by reducing the surface viscosity and secondly by controlling suction-side aft-shock-wave development. A new vane shape coupled with a gas-turning-combustor system is suggested to improve vane-film cooling effectiveness further.

Discussion: “Effect of New Blade Cooling System With Minimized Gas Temperature Dilution on Gas Turbine Performance” (Kawaike, K., Kobayashi, N., and Ikeguchi, T., 1984, ASME J. Eng. Gas Turbines Power, 106, pp. 756–764)

“…Previous work reported by this discusser [4] gives credit to Bruce Buckland for his efforts to use steam cooling in a closed cycle. Also this discusser's previous ASME papers [5][6][7][8][9], present analyses of using steam for convection cooling followed by film blanket cooling. Reference is also made to the fact that General Electric listed steam cooling as its second choice for blade cooling for its completed DOE/EPRI water blade-cooling research program [10].…”

“…1 and 2, of [5] and [6]. These graphs were produced by using a method of stream separation and by following steam as a working fluid and coolant through both the simple and reheat (gas and steam) cycles and heat recovery boiler.…”