Tham khảo tài liệu 'kỹ thuật máy bay chiến đấu episode 1 part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 212 AIRCRAFT DESIGN off consider using auxiliary suck-in doors during takeoff. This allows the inlet to be sized to another lesser capture area requirement. To avoid the confusion of differing velocities and densities the airflow is defined by mass flow in pounds mass per second. Mass flow is related to flow conditions by Eq. where g is ft s2. m gpVA Ib s Figure defines the capture area geometry for a supersonic ramp or cone inlet. This inlet is shown at the design case which is known as shock-on-cowl. At this Mach number and ramp angle the initial oblique shock is almost touching the cowl lip. If the auxiliary doors are shut and the shock is on cowl the geometric capture area is providing exactly the right amount of air for the engine bleed and secondary flow. Usually the inlet ramp geometry provides shock-on-cowl at about Mach above the aircraft s maximum speed giving a safety margin for speed overshoot and engine mass-flow fluctuations. If the total mass flow required by the engine bleed and secondary flow is known then Eq. can be solved for the required cross-sectional area upstream of the inlet at infinity using the freestream values for density and velocity. This calculated area is identical to the capture area in the design case shock-on-cowl since all of the air in the capture area is going into the inlet. The required engine mass flow is provided by the engine manufacturer and is a function of the Mach number altitude and throttle setting percent power . Usually the manufacturer s data should be increased by 3 to allow for manufacturing tolerances. The secondary airflow requirements are accurately determined by an evaluation of the aircraft s subsystems such as environmental control. For initial capture-area estimation Table from Ref. 26 provides secondary airflow as a fraction of engine mass flow. Table Secondary airflow typical 26 ms me Engine Nacelle cooling Oil cooling Ejector nozzle air .
