Commercial Aircraft Propulsion and Energy Systems Research Reducing Global Carbon Emissions (2016) / Chapter Skim
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2 AircraftPropulsion Integration
2 AircraftPropulsion Integration
Pages 22-34
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From page 22... ...
Overall, the fuel burn per seat mile of gas turbine–powered commercial aircraft has been reduced by 70 percent since service started in the 1950s, at an average rate of about 1 The power and energy needs of aircraft are driven by their size, speed, and range. Compared to an automobile, a large commercial aircraft has a much greater passenger capacity (100-400 passengers)
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From page 23... ...
BASIC CONSIDERATIONS For the purposes of this study, it is useful to consider aircraft propulsion as consisting of three interdependent elements: an energy storage system, a motor to produce shaft power from that stored energy, and a propulsor to convert shaft power to propulsive power. Each is discussed briefly below.
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From page 24... ...
100 90 80 Engine fuel 70 consumption % of base (Comet 4) 60 50 40 Aircraft fuel burn per seat 30 20 Fuel Burn Trend –2%/yr Since 1970 10 0 1950 1960 1970 1980 1990 2000 2010 Year of model introduction FIGURE 2.3 History of commercial aircraft fuel burn per seat-mile.
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From page 25... ...
FIGURE 2.4 Benefit of fuel burn weight decrease on net propulsive energy needed to fly a particular range in a single-aisle aircraft. SOURCE: Marty K
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From page 26... ...
The motor efficiency of large commercial aircraft gas turbines in service (defined as shaft power produced divided by fuel energy flow in) is now about 55 percent.
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From page 27... ...
Fan Pressure Ratio Tradional Nacelle Installed Performance Advanced Nacelle Installed Performance Fuel Burn Direct Benefit from Nacelle Technology Additional Benefit with UHB Engines Better Uninstalled Performance FIGURE 2.6 Influence of fan pressure ratio (and there fore fan area at constant thrust) and installation on air craft fuel burn for a sample ultrahigh bypass ratio engine Current Engines UHB Engines with a compact advanced nacelle.
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From page 28... ...
, and it also projects that the cost of jet fuel will track the cost of crude oil.4,5 The economic viability of technologies that significantly increase the cost of propulsion systems and aircraft but reduce energy cost is very strongly dependent on the value placed on carbon emissions relative to other aircraft properties such as economy, speed, noise, and so on. 4 Energy Information Agency, 2016, Petroleum and Other Liquids: Spot Prices, Washington, D.C.
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From page 29... ...
One major challenge is that these installations required relatively long ducts to move air to and from the engines. Such duct lengths, with relatively large viscous losses due to large surface area, are not compatible with the low fan pressure ratios used to improve propulsive efficiency on modern commercial airliners.
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From page 30... ...
uses a turboelectric configuration in which two gas turbines drive electric generators that in turn power 13 electric motor–driven fans.11 Not shown is the Boeing SUGAR Freeze, which has an aft fuselage BLI configuration for an aircraft powered by cryogenic fuel (liquefied natural gas) .12 BLI configurations also can benefit from using the larger number of fans with low fan pressure ratio to produce a higher propulsive efficiency (same trend as in Figure 2.5)
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From page 31... ...
Considerable research will be required to establish the net energy reduction benefit of practical BLI configurations and to identify any impacts on other aircraft requirements such as noise, safety, and reliability. All things considered, boundary layer ingestion configurations may be a productive research path for reducing aircraft fuel burn.
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From page 32... ...
aircraft platforms, distributed propulsion concepts, and boundary layer ingestion configurations. CHALLENGES Technical Challenges Propulsive Efficiency Low fan pressure ratios are needed to reduce exhaust velocities and thereby improve propulsive efficiency, regardless of whether the fan is driven by a gas turbine or an electrical motor.
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From page 33... ...
Currently, the price of jet fuel is well within the range of historic norms, so aircraft depreciation is a larger cost than fuel. Thus technical approaches to reducing fuel burn that significantly increase the purchase price of an airplane are not favored commercially.
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From page 34... ...
This research project is closely related to the gas turbine research project on low pressure ratio fan propulsors, and work on the two should be closely coordinated. Boundary Layer Ingestion Pursue technologies that can enable boundary layer ingestion to reduce the velocity defect in the aircraft wake (also known as wake cancellation)
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