Environmental Engineering Reference
In-Depth Information
Source: Birch, 2000
Figure 10.4 Thermal efficiency variations
Source: Birch, 2000
Figure 10.5 Trade-off between noise and fuel efficiency
high by-pass ratio engines, continued increases in by-pass ratio can lead away from
the optimum engine design. Figure 10.5 shows the trade-offs that exist between increas-
ing by-pass ratio and fuel consumption.
Additional noise reducing techniques can be employed, such as reducing fan tip
speed and careful shaping of fan blades to reduce fan noise. Noise from turbo machin-
ery can be minimized by optimizing the number of rotating parts and careful rotor/
stator spacing. The addition of acoustic liners to the inlet and exhaust sections of the
nacelle can also reduce noise, but this can add weight to the aircraft, thus creating a
trade-off with fuel consumption. Figure 10.6 shows areas of research in this field.
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