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Thermodynamics and Propulsion | |
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The balance between propulsive efficiency and specific thrust (
thrust per unit mass flow) is shown in
Figure 11.2.
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For fighter aircraft that need high thrust/weight and fly at high speed, it is typical to employ engines with smaller inlet areas and higher thrust per unit mass flow,
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However, transport aircraft that require higher efficiency and fly at lower speeds usually employ engines with relatively larger inlet areas and lower thrust per unit mass flow,
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At low flight velocities, the highest propulsive efficiency is typically obtained with a propeller or an unducted fan. Figure 11.5 shows a propeller craft, and Figure 11.6 shows a sketch of a jet engine with an unducted fan. Figure 11.7 shows propulsive efficiency as a function of airspeed for different engine bypass ratios.
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UnifiedTP