Air-Intake Design

Fig. D-5 shows an external compression air-intake designed for optimized use at Mach number 2.0. Fig. D-6 shows a set of computed airflows of an external compression air-intake designed for use at Mach number 2.0 (a) critical flow, (b) sub-critical flow, and (c) supercritical flow. The pressures at the bottom wall and the upper wall along the duct flow are also shown. Two oblique shock waves formed at two ramps are seen at the tip of the upper surface of the duct at the critical flow shown in Fig. D-6 (a). The reflected oblique shock wave forms a normal shock wave at the bottom wall of the throat of the internal duct. The pressure becomes 0.65 MPa, which is the designed pressure. In the case of the subcritical flow shown in Fig. D-6 (b), the shock-wave angle is increased and the pressure downstream of the duct becomes 0.54 MPa. However, some of the airflow behind the obhque shock wave is spilled over towards the external airflow. Thus, the total airflow rate becomes 68% of the designed airflow rate. In the case of the supercritical flow shown in Fig. D-6 (c), the shock-wave angle is decreased and the pressure downstream of the duct becomes 0.15 MPa, at which the flow velocity is stiU supersonic.

Figure D-5. External compression air-intake designed for use at Mach 2.0.

Flame arrestor plugs. Insufficient eonfcustior sir Loss of heater equipment shutdown, possible equipment Air intake designed 3 feet above ground Place in operator manual requirements for... 

Air intakes at onshore facilities should be located at a minimum of 7.5 meters above grade when within 15 meters of process units or within 30 meters of process units containing flammable hydrocarbons. Calculation of air intake design should include an analysis of the effect of the intake on surrounding air patterns to ensure that airflow to the intake is above the 7.5 meters minimum level. 

Great care is required regarding the positioning and design of the air intake to avoid drawing in local impurities and rain or snow. 

Absolute moisture content of winter outside air intake at design condition ... 

Design sensible heat of outside air intake kg/s x kJ/kg Less actual on day of test kg/s x kJ/kg... 

The air intake of a compressor should be sited so that, as far as possible, cool, clean, dry air is inspired. When located outdoors the air intake should be protected against the weather. The air intake should be designed and sited so that noise is reduced to the necessary level. 

If the MCC will be located within an electrically classified area, the ventilation system must be designed, operated and maintained to create a positive pressure inside the MCC building and the air intake located outside of the electrically classified area. The MCC should be equipped with smoke detectors and alarmed to a constantly attended location. CO2 fire extinguishers are the suggested protection for MCC rooms. The storage of combustible materials inside an MCC must be prohibited. 

The compressed air introduced from the atmosphere through the air-intake is termed ram air , and the associated pressure is termed ram pressure . Ram pressure is built-up when the airflow velocity is decelerated in flow fields. The air-intake is designed as an aerodynamic tool to obtain maximum ram pressure.lh Air-intakes are designed to decelerate supersonic flow to subsonic flow by the formation of shock waves in front of them. The combustor in which the fuel gas is burned with the ram air is termed a ramburner . 

Referring to Fig. 1.3, the momentum entering the air-intake is given by rhj> and that exiting from the nozzle is given by (m -i- m v. The thmst created by the momentum change is fundamentally represented by Eq. (1.62). When the air-intake and the nozzle attached to the ducted rocket are designed to obtain maximum thrust efficiency, the pressures at the front end of the air-intake and at the aft end of the nozzle become Pa = Pi = Pr> and then Eq. (1.62) is represented by... 

Fig. D-2 shows the shock-wave formation at a supersonic diffuser composed of a divergent nozzle. Three types of shock wave are formed at three different back-pressures downstream of the diffuser. When the back-pressure is higher than the design pressure, a normal shock wave is set up in front of the divergent nozzle and the flow velocity becomes a subsonic flow, as shown in Fig. D-2 (a). Since the streamline bends outwards downstream of the shock wave, some air is spilled over from the air-intake. The cross-sectional area upstream of the duct becomes smaller than the cross-sectional area of the air-intake, and so the efficiency of the diffuser is reduced. The subsonic flow velocity is further reduced and the pressure is increased in the divergent part of the diffuser.

The location and sign of fresh air intakes and discharge air exhausts to the atmosphere from air handling plants should be designed to eliminate the risk of product cross-contamination by short circuiting of air streams. 

The paper discusses suction-intake design, suction-bell submergence, air-entrainment potential, and net positive suction head of cooling towers. Guidelines on possible problems and ways to assure reliable operation of cooling towers are given. 

Building services should be designed so that cooling towers are located well away and downwind from air intakes, opening windows, and occupied areas (ideally greater than 100 feet distance). 

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