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Research Papers

Preparing for the Future: Reducing Gas Turbine Environmental Impact—IGTI Scholar Lecture

[+] Author and Article Information
Nicholas A. Cumpsty

Imperial College, London, UK SW7 2AZ

The U.S. Government Energy Information Administration released data in 2008. Assuming 2006 consumption, it can be calculated that accessible coal can meet consumption for about 200 years, while natural gas can meet consumption for about 60 years. If, however, natural gas replaced coal the proven reserves of natural gas would be exhausted in about 30 years.

A380-800, A340-500, A340-600, B777-200ER, B787-base, B787-stretch, B777–300, and B747-400.

From the Boeing website, it may be seen that the B787-8, B787-9, and B787-3 are designed for ranges of 7500–8200 nm, 8000–8500 nm, and 2500–3050 nm, respectively. From the Airbus website, the ranges for the A350-800, A350-900, and A350-1000 are 8300 nm, 8100 nm, and 8000 nm, respectively

Note added to Journal paper in proof. Bohr's observation, quoted at the opening of the paper, is born out here. It now looks as if unconventional sources of natural gas (shale gas, tight gas, coal-bed methane) are abundant and more accessible than had been widely realized. Reports suggest that these unconventional sources of natural gas may be more abundant than the conventional sources used hitherto, and as a result the use of coal for electricity generation may be much reduced.

J. Turbomach 132(4), 041017 (May 11, 2010) (17 pages) doi:10.1115/1.4001221 History: Received July 26, 2009; Revised July 27, 2009; Published May 11, 2010; Online May 11, 2010

Abstract

In the long term, the price of fuel will rise and it is now urgent to reduce carbon dioxide emissions to avoid catastrophic climate change. This lecture looks at power plant for electricity generation and aircraft propulsion, considering likely limits and possibilities for improvement. There are lessons from land-based gas turbines, which can be applied to aircraft, notably the small increases in efficiency from further increase in pressure ratio and turbine inlet temperature. Land-based gas turbines also point to the benefit of combining the properties of water with those of air to raise efficiency. Whereas the incentive to raise efficiency and reduce $CO2$ will force an increase in complexity of land-based power plant, the opportunities for this with aircraft are more limited. One of the opportunities with aircraft propulsion is to consider the whole aircraft operation and specification. Currently the specifications for new aircraft of take-off and climb thrust are not fully consistent with designing the engine for minimum fuel consumption and this will be addressed in some depth in the lecture. Preparing for the future entails alerting engineers to important possibilities and limitations associated with gas turbines which will mitigate climate change due to carbon dioxide emissions.

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Figures

Figure 1

Temperature-entropy chart for steam power plant (1)

Figure 2

Thermal efficiencies of simple gas turbines from Wilcock (2). Overall pressure ratios of 60 for broken line, 45 for solid line, and 30 for dotted line. (a) black is ηs=100%, no cooling; (b) blue ηs=90%, no cooling; (c) red ηs=90%, “advanced” cooling.

Figure 3

Alstom GT24/26 combined-cycle gas turbine, with reheat of gas in a second combustor after HP turbine (1)

Figure 4

Temperature-entropy diagram of Alstom GT24/26 with reheat of gas after HP turbine (1)

Figure 5

Rolls-Royce WR21 engine for marine propulsion. VAN refers to variable area nozzle, a means to vary power output and speed (4)

Figure 6

The Rolls-Royce WR21 marine gas turbine (4)

Figure 7

A simplified scheme using a gas turbine for power generation with CO2 separation with oxy-fuel combustion (9)

Figure 8

A simplified scheme for power generation based on gasification of coal and separation of CO2 from the fuel (8)

Figure 9

The link of sfc and overall efficiency with thermal efficiency and propulsive efficiency (10)

Figure 10

Specific fuel consumption versus bypass ratio at cruise for different fan pressure ratios. Core conditions held constant, opr=40, TET=1475 K.

Figure 11

Core conditions for maximum take-off at ISA+15 K for data core with different fan pressure ratios at cruise. The solid line is take-off thrust of 0.3MTOW, and the broken line is 0.275MTOW.

Figure 12

Fan pressure ratio at MTO and TOC (data core)

Figure 13

Corrected mass flow for max. take-off and top of climb divided by corrected mass flow at cruise (data core), FnTO=0.3MTOW

Figure 14

Fan operating characteristic with design fpr=1.8 at cruise, data core. MTO is for FnTO=0.3MTOW, and MCL is TOC at 500 ft/min.

Figure 15

Fan operating characteristic with fpr=1.5 at cruise, data core. MTO is for FnTO=0.3MTOW, and MCL is TOC at 500 ft/min.

Figure 16

The proposed CLEAN engine, part of EU EEFAE program (15)

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