How CMCs can boost gas turbine efficiency

In his previous article, the author talked about CMC technology that is in the offing, and its use in jet engines. Here, he discusses the potential of reheat engines and explains how CMCs could be re-designed for a shorter length for both the first combustor and the re-heat combustor.

The future looks bright for the use of CMCs for jet engines, fan engines and now, industrial gas turbines. Think what this could mean for direct drive power turbines of fan engines that have a number of stages, are costly to make, and weigh a lot. This technology could challenge the new P&W geared fan engines as the way to go. As for the industrial gas turbines, both aero and heavy duty, the CMCs could be a shot in the arm for future units and could make combined cycle efficiencies to rise to 65 percent.

Savior for GT24 and GT26

The fate of the GT 24 and 26 industrial gas turbines is yet to be announced by GE after its recent takeover of Alstom but presently being challenged by Siemens and MHI. Will GE drop these units or will it elect to re-design them as another product to sell? These reheat engines have great potential for simple cycle units and for combined cycle operation, and when considering the rapid development of the CMCs and factories in place to make such parts there is hope for the these re-heat gas turbines.

CMCs could be used for both the first combustor and the re-heat combustor, re-designed for a shorter length using advance technology. The shrouds and other hot stationary parts could be made of CMCs. Finally, the fixed nozzle vanes and rotating blades could be made out of CMC material. What a difference this could make in these machines in terms of output and efficiency. The two TITs could be raised and the output could be increased considerably by also reducing cooling air requirements.

I would like to ask GE Chairman and CEO, Jeffery R. Immelt, who is bullish for all gas turbines, to personally take a very close look at the Alstom GT 24 and 26 industrial gas turbines and re-design them into advanced machines. I ask him to put pressure on the GE/Alstom evaluation team to recommend such positive action be taken in view of recent development of CMCs and the growing market for both aero and industrial gas turbines and combined cycles. 

(Ivan G. Rice was past chairman of the South Texas Section of ASME (1974 - 75), past chairman of the ASME Gas Turbine Division (now IGTI) (1975 - 76). A Life Fellow Member of ASME and Life Member of NSPE/TSPE, he has authored many articles and ASME papers on gas turbines, inter-cooling, reheat, HRSGs, steam cooling and steam injection.)