Gas Turbine Technologies

The Combined (Brayton-Rankine) Cycle The 1990s has seen the rebirth of the combined cycle, the combination of gas turbine technologies with the steam turbine. This has been a major shift for the utility industry, which was heavily steam-tnrbine-oriented with the use of the gas turbine for peaking power. In this combined cycle, the hot gases from the turbine exhaust are used in a heat recoveiy steam generator or in some cases in a snpplementaiy fired boiler to produce superheated steam. 

In the area of performance, the steam turbine power plants have an efficiency of about 35%, as compared to combined cycle power plants, which have an efficiency of about 55%. Newer Gas Turbine technology will make combined cycle efficiencies range between 60-65%. As a rule of thumb a 1% increase in efficiency could mean that 3.3% more capital can be invested. However one must be careful that the increase in efficiency does not lead to a decrease in availability. From 1996-2000 we have seen a growth in efficiency of about 10% and a loss in availability of about 10%. This trend must be turned around since many analysis show that a 1% drop in the availability needs about 2-3% increase in efficiency to offset that loss. 

The pressurized hybrid cycle provides the basis for the high electric efficiency power system. Applying conventional gas turbine technology, power system efficiencies in the 55 to 60 percent range can be achieved. When the pressurized hybrid system is based on a more complex turbine cycle— such as one that is intercooled, reheated, and recuperated—electric efficiencies of 70 percent or higher are projected. 

Siemens-Westinghouse Power Corporation, of Pittsburgh, PA, with a subcontract to Allison Engine Company, evaluated a pressurized solid oxide fuel cell coupled with conventional gas turbine technology without a steam plant. The system was operated at a pressure of 7 atm. The fuel cell generated 16 MW of power and the gas turbine generated 4 MW of power. The process showed 67 % efficiency as developed. An efficiency of 70 % is deemed achievable with improvement in component design. The COE is predicted to be comparable to present day alternatives. NOx levels were less than 1 ppm. 

Kaganovich, B. M., Keiko, A. V. and Shamansky, V. A., "Thermodynamic Studies of Fuel Combustion in Connection with the Use of Gas Turbine Technologies in Small-Scale Energy". ISEM SO RAN, Irkutsk (2006). (Preprint At, 6. 37 p. (in Russian)). 

The system has a remarkably high efficiency and is considered to be relatively easily realized based on conventional gas turbine technologies, and therefore the wide installation of the proposed system could be expected for reducing CO2 emission in the near future. 

In gas turbine technology catalytic combustion (Section 3) is an important method to lower NOx emissions. Section 2.2 summarizes briefly aspects of the cat-... 

At the Imperial College of Science in London, Whitelaw and his researchers (Chapter 6) conducted detailed experiments with turbulent premixed opposed-jet flames relevant to modern gas-turbine technologies based on lean premixed combustion. Using photography and chemiluminescence imaging, they examined the effects of equivalence ratio, bulk flow velocity, and flow separation on... 

Hardalupas, Y., Orain, M., Panoutsos, C. S., Taylor, A. M. K. P, Olofsson, J., Seyfried, H., Richter, M., Hult, J., and Alden, M. "Chemiluminescence Sensor for Local Equivalence Ratio of Reacting Mixtures of Liquid Euel Vapour in Air." In Proceedings of the First International Conference on Industrial Gas Turbine Technologies, edited by... 

Natural gas fired power stations with steam cycles achieve efficiencies between 42 and 47 %, fig. 1. But obviously the gas turbine technology offers, in particular for natural gas based systems, a number of advantages, e.g. low capital cost, short construction time, and last not least high potential for efficiency. 

In summary The efficiency potential of the gas turbine technology for the conversion of high temperature heat from the HTR into electricity is - in principle - as high as that based on natural gas. Therefore it is proposed here to take the gas-plus-steam-turbine-cycle, GST, into consideration, in particular with a "3-pressure-steam-turbine-cycle". With further improvements, in particular in the gas turbine cycle, and with the assumption that the gas turbine-inlet temperature is 1 OSO (100 K more than AVR in 1974) the calculated net efficiency is 54.5 %. A particular advantage of the GST versus the gas turbine cycle with recuperation is that the core-inlet temperature is smaller at comparable efficiency conditions. 

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