1、 SAE ARP*405b 8357340 0054335 4 SAE ARP4056 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Exhaus.t gases should be directed to the atmosphere clear of the cockpit and cabin, fuel tanks, fuel and oil drains, secondary air intakes, any flammable parts of the aircraft, and any rotor induced airstream that subseq
2、uently enters the air intakes. No adverse temperature or exhaust impingement conditions should exist on the aircraft, on the ground, or on personnel in proximity to the rotorcraft. Turboshaft engines installed in rotorcraft are designed to have low exhaust velocity and propulsive thrust. pressure re
3、gion considering different aircraft flight modes. The discharge should be into a low static The exhaust system should be designed to minimize reingestion of exhaust gases into the engine inlets. In addition to the exhaust system design, the spatial relationship of the exhaust to the inlet and to the
4、 rotor should be considered. Wheel wells and fuselage structure should be sealed to prevent the entrance of exhaust gases. The exhaust tailpipe should provide for the drainage of fuel, oil, or rainwater in the tailpipe. aircraft structure to prevent reentry into the aircraft, and to prevent impingem
5、ent on any part of the aircraft or on an external load. These fluids should be conducted outside the The exhaust tailpipe should be capable of withstanding nonsymmetrical air loads characteristic of the system. The exhaust system should be heat and corrosion resistant. fabricated of materials that a
6、re capable of withstanding an operating temperature 50C above the maximum temperature of the hottest portion of the engine exhaust gas at the entrance of the tailpipe (including circumferential deviation from the average) when the engine is operated at the ambient temperature 1 imi t and the maximum
7、 (1 imi t) gas temperature. It should be Thermal fa part i cul ar experience exceed the 3.10 It may be iirovide n igue should be considered in the exhaust system design, y in the design of those.members of the exhaust system that the full impact of the starting and transient temperatures that design
8、 operating temperature of 3.8. desired to use an exhaust ejector to induce secondary airflow, to celle ventilation, component cooling, or inlet particle separation (reference AIR1191). source must be carefully integrated into the ejector, with special attention given to operation in adverse wind con
9、ditions (i.e., rear-quartering winds and tailwinds), off-design ejector performance which should not permit engine exhaust backflow into areas that require cooling/ventilation airflow. Use of the engine exhaust as a motive A further consideration is -2- SAE ARPW05b 87 rn 8357340 005431b b rn SAE ARP
10、4056 3.11 Exhaust system outlets should be provided with plugs and/or covers for protection when the aircraft is not being used. Civil certification regulations (FAR PART 27 and FAR PART 29) require additional fire protection/safety features which may not be required in a military aircraft. They req
11、uire that hot surfaces be located or shielded to prevent impingement of leaking flammable fluids or vapors that might cause a fire. rotorcraft outside the engine compartment by a firewall. FAR 27.1121 and 29.1121 must be considered in the design of exhaust systems for civil ai rcraf t. Also, the exh
12、aust system must be separated from the The use of common exhaust systems in multiengine rotorcraft would require special consideration of engine failure modes and potential exhaust backf low prob1 ems. Some military mission requirements necessitate protection from heat-sensing missiles. suppression
13、device, which minimizes the infrared signature of hot metal parts and the engine exhaust plume. The required exhaust system may be an infrared signature 4. PHYSICAL INTERFACES: The mounting type, location, dimensions, and limit loads of the exhaust tailpipe connection, and of the exhaust center body
14、 connection if required, should be identified in the engine specification or the installation manual (reference 3.2.15 of AS1507). 4.1 The induced loads and moments on the engine, including vibratory loads (see 4.21, should not exceed the specification/installation manual limits. 4.2 Connectors and
15、necessary supports should allow thermal expansion up to the maximum engine operating temperature and should allow tailpipe deflection due to aircraft operation within the flight envelope. The connectors and supports should not transfer vibratory loads or restrict thermal expansion which might cause
16、damage or failure to the engine, airframe, or exhaust system. In the event of a tailpipe being rigidly attached o the engine, the design must avoid damaging resonances that induce vibratory loads in excess of engine limits. 4.3 Exhaust system parts should be interchangeable with respect to installat
17、ion and performance. 4.4 Fasteners for attaching the tailpipe to the engine and for alt clamps, brackets, flanges, and other attachment fittings necessary for proper installation, should have positive locking features. 4.5 Failure of the tai engine or to the a pipe retention means should not result
18、in a hazard to the rcraf t. SAE ARP*4056 89 m 8357340 0054337 m SAE ARP4056 I 4.6 Steps and gaps in the flow path between engine tailpipe and airframe exhaust fairing should be designed to prevent rubbing under the worst conditions of transient operation, to prevent exhaust ingestion into secondary
19、airflow systems, and to avoid flow path obstructions. 4.7 Struts between the tailpipe center body and outer wall must avoid damaging resonances in the vibratory range of upstream components. 5. PERFORMANCE INTERFACES: In the engine model specification/installation manual, the engine manufacturer sho
20、uld include a recommended exhaust tailpipe configuration (a referee tailpipe) that is consistent with guarantee performance, and velocity and temperature characteristics of the engine exhaust plume.corresponding to the referee tailpipe (Reference AS1507, Appendix A, 1.9). The aircraft manufacturer m
21、ay elect to use an exhaust system design that differs from the engine manufacturers recommendation. For the range of airspeeds typical of the helicopter, the best performance generally is realized by maximizing the engine shaft horsepower available. A well-designed diffusing tailpipe that provides t
22、he largest exit flow area results in the lowest exhaust velocity minimizing the static pressure at the engine exhaust/tailpipe inlet interface and maximizing the shaft horsepower available. Considerations other than the maximum power available, such as size, weight, ejector efficiency, etc., may inf
23、luence the exhaust system flow areas, If the engine exhaust flow is used as the motive source of an ejector, a small tailpipe exhaust area may be desirable to increase the exit velocity. Power corresponding to the energy of the exhaust stream must be added to th output shaft power to obtain a true m
24、easure of irrstalled engine performance. In English units: wg x v$ SHPTOTAL = SHPACTAL + 550 Where: SHi? = shaft horsepower gas flow, lbm/s velocity, ft/s Wg = exhaust Vg = exhaust go = dimen lbm - ft ional constant = 32.17 lbf - s2 -4- SAE ARP*4056 49 8357340 005431i8 T SA ARP4056 5. (Continued): I
25、n Metric, Units: wg x vg2 KWTOTAL = KMACTUAL + looo Where: KW = Output shaft power, kw Wg = Exhaust gas flow, kg/s Vg = Exhaust velocity, m/s Smaller tailpipe area results in reduced shaft horsepower available, impact of exhaust flow areas on installed performance must be accounted for in power assu
26、rance checks of engine deterioration in service. The Another influence on exhaust system design is the requirement to minimize reingestion of hot exhaust gas into the engine inlet (see 3.4). arrangements, the location of the exhaust in relation to the rotor or in relation to another engine inlet has
27、 been the primary cause of reingestion problems. Also, the velocity of the hot gas at the exhaust can be a secondary influence on reingestion characteristics. In pas design Performance considerations that enter into the design of an exhaust system differing from the referee tailpipe include the foll
28、owing: a. The included angle between the outer walls of a diffusing tailpipe is limited to a value that results in proper deceleration of the flow without separation from the outer wall, and in conjunction with overall length constraints dictate the achieveable exhaust area (see 3.3.3 of ARP1168). b
29、. The center body of the exhaust system introduces an unwanted complexity to the design that should be weighed against the “dump“ loss created by removing the center body. c. Variations in swirl angle of the flow at the engine exhaust flange, which is a function of the engine shaft horsepower and th
30、e output shaft speed, must be tolerated by the exhaust system design. opt.imum performance is needed should be specified to be used as a reference, where the exhaust flow is virtually axial in direction. A design point where d. There may be limits on the static pressure imposed at the engine exhaust
31、 flange which must be observed in the design of the exhaust system. Depending upon the engine design configuration, compressor bleed air for lube system seal pressurization/balance piston may be vented into the exhaust system, and so the static pressure must be compatible with engine requirements. -
32、5- SAE ARPm4056 89 8357340 0054339 1 SAE ARP4056 - 5. (Continued): e. A thermodynamic performance model of the exhaust system, which is compatible with the engine manufacturers engine math model and capable of being integrated into the engine model logic, should be provided (Reference 4.3 of AS681D)
33、. The exhaust system model should satisfy conservation considerations as well as exhaust system boundary conditions. One such performance representation is pictured in Figure 1; it is one of several possibilities. Different engine manufacturers may propose using different representations. The model
34、should be coordinated between the engine and the airframe manufacturer. The model replaces the tailpipe losses for the engine manufacturers referee tailpipe in the engine performance program. PREPARED BY SAE COMMITTEE S-12, HELICOPTER POWERPLANT -6- SAE ARPa405b 89 8357340 0054320 8 SAE ARP4056 Ps 9-Ps7 cp = p7v72 2 Station 9 = exhaust sysem exit Station 7 = engine exhaust flange Ps = static pressure p7 = density at exhaust flange V7 = velocity at exhaust flange a7 = swirl angle at exhaust flange FIGURE 1 - Engine Exhaust System Performance Model
