Inlet is generally a large smooth aluminum or

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inlet is generally a large, smooth aluminum or magnesium duct which must be designed to conduct the air into the compressor with minimum turbulence and restriction.  The air inlet section may have a variety of   names   according   to   the   desire   of   the   manufacturer.     It   may   be called the front frame and accessory section, the air inlet assembly, the   front   bearing   support   and   shroud   assembly,   or   any   other   term descriptive of its function.   Usually, the outer shell of the front frame is joined to the center portion by braces that are often called struts.  The anti-icing system directs compressor discharge air into these struts.  The temperature of this air prevents the formation of ice that might prove damaging to the engine.  Anti-icing systems are discussed   further   in   the   chapter   covering   the   engines   they   may   be installed   on.     Figure   1.11   illustrates   the   variety   of   inlet   duct designs of Army aircraft. 25
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Figure 1.11 .  Inlet Duct Variations . 26
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1.19. COMPRESSOR SECTION The compressor is the section of the engine that produces an increase in air pressure.   It is made up of rotating and stationary vane assemblies.  The first stage compressor rotor blades accelerate the air rearward into the first stage vane assemblies.   The first stage vane assemblies slow the air down and direct it into the second stage   compressor   rotor   blades.     The   second   stage   compressor   rotor blades   accelerate   the   air   rearward   into   the   second   stage   vane assemblies, and so on through the compressor rotor blades and vanes until   air   enters   the   diffuser   section.     The   highest   total   air velocity is at the inlet of the diffuser.  As the air passes rearward through   the   diffuser,   the   velocity   of   the   air   decreases   and   the static   pressure   increases.     The   highest   static   pressure   is   at   the diffuser outlet. The compressor rotor may be thought of as an air pump.   The volume   of   air   pumped   by   the   compressor   rotor   is   basically proportional to the rotor rpm.  However, air density, the weight of a given volume of air, also varies this proportional relationship.  The weight per unit volume of air is affected by temperature, compressor air inlet pressure, humidity, and ram air pressure*.   If compressor air   inlet   temperature   is   increased,   air   density   is   reduced.     If compressor air inlet pressure is increased, air density is increased. If   humidity   increases,   air   density   is   decreased.     Humidity,   by comparison with temperature, and pressure changes, has a very small effect on density.   With increased forward speed, ram air pressure increases and air temperature and pressure increase. The   following   is   an   example   of   how   air   density   affects compressor efficiency of the T62 gas turbine.  At 100 percent N 1   rpm, the compressor rotor pumps approximately 40.9 cubic feet of air per second.   At standard day static sea level conditions, 59
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  • Fall '19
  • Internal combustion engine, Gas turbine, Gas compressor

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