1、SAE AIR*4204 91 7943725 0008079 b m The Engineetfng Society LIAL =For Advancing Mobility Land Sea Air and Space, INTERNATIONA Lw 400 Commonwealth Drive, Warrendale, PA 15096 -0OOl AEROSPACE INFORMATION REPORT Submitted for recognition as an American National Standard Issued 1991-01-29 COMMERCIAL AIR
2、CRAFT AUXILIARY POWER UNIT INSTALLATIONS FOREWORD This document has been prepared as a SAE AE-6 Committee project. Recognition is given to the Garrett Corporation for permission to extract from the Garrett Installation Handbook - Airborne Auxiliary Power Units (Reference 2.1). Many of the figures we
3、re taken directly from it and some of the text is essentially a condensation of the text from that document. _ SAE Technical Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its ap
4、plicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments a
5、nd suggestions. Copyright 1991 Society of Automotive Engineers, Inc. All rights reserved. Printed in U.S.A. _- _I SAE AIRu4204 91 E 7943725 O000080 2 = SA AIR4204 1 . 1.1 2, 3 . 3.1 3.2 4. 4.1 4.2 4.3 5 . 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 TABLE OF CONTENTS SCOPE Purpose REFERENCES .
6、 GENERAL BACKGROUND . Uses . Description INSTALLATION CONSIDERA APU Location . output . . . IONS . . Mai ntai nabi 1 i ty INSTALLATION REQUIREMENTS Safety . Air Inlet Exhaust System . Mounting . Fuel Supply Lubrication System . Starting System Control and Electrical System Electronic Controls Access
7、ory Drives . Bleed Air System . Noise Attenuation PAGE 3 3 3 4 4 5 6 11 13 15 20 20 29 38 46 50 54 63 71 82 87 90 96 -2- SAE AIR4204 1. SCOPE: This Aerospace Information Report (AIR) reviews the factors to be considered in determining the location and arrangement for auxiliary power unit (APU) insta
8、llations for airborne applications and reviews requirements for flight sui tabi 1 i ty. As treated in this discussion, the APU normally includes a power section (or engine), a starting system, an electronic control unit (ECU), a gearbox with accessory mounting pads, and an oil cooling system. The ac
9、cessories that are driven by the APU, such as CSDs (constant speed drives), alternating current (AC) generators, hydraulic pumps, or air compressors, are not covered here except insofar as they make demands on the APU. The various installation components and systems that are covered here are outline
10、d by the table of contents. Turbine-type APUs are by far the most highly developed and universally used airborne units, so their installation will dominate the discussion in this document. applications, many military transports are adaptations of commercial carrier aircraft. The bulk of the discussi
11、on will, therefore, be oriented toward APU installation requirements as developed by the civilian sector. of the internal design aspects of the APU itself are not within the scope of this document. And, though there have been some APUs developed for military Discussions 1.1 Purpose: The purpose of t
12、his document is to aid APU installation designers by assuring that no important design aspect of the installation will be overlooked. References 2.1 and 2.2 are also documents published by APU manufacturers for this purpose. Reference 2.3 is a useful design handbook published by the U.S. Air Force.
13、2. REFERENCES: 2.1 2.2 2.3 2.4 2.5 2.6 Installation Handbook - Airborne Auxiliary Power Units. Engine Company. Second edition - 1983. Installation Manual - Turbine Driven Auxiliary Power Units. Turbomach July 1980. AFSC Design Handbook 2-3 Propul sion and Power, ASD/ENESS, Wright Patterson AFB, Ohio
14、 45433: Phone (513)255-6281 Garrett Turbine TSO-C77a, 7120181 (Technical Standard Order) Subject: Gas Turbine Auxiliary Power Units. Department of Transportation, FAA. FAA ORDER 8430.6 C: Suspectors Handbook: Section 6. Master Minimum Equipment List (MMEL). 2 July 1984. MIL-P-85573 (AS): Power Unit,
15、 Aircraft Auxiliary, Gas Turbine, General Specification for: 15 Nov. 1983. -3- SAE AIR*4284 91 W 7943725 O000082 b W SA AIR4204 2.7 ASD Technical Report 61-381, “Guide to Design of Mechanical Equipment for Maintainability.“ Armed Services Technical Information Agency, Arlington Hall Station, Arlingt
16、on, Virginia. .2.8 FAR 25: Federal Avaiation Regulations, Part 25 - Airworthiness Standards: Transport Category Airplanes, June, 1974. 2.9 “Design Manual on Aircraft Fire Protection for Reciprocating and Gas Turbine Engines.“ Aerospace Industries Association. Obtainable from National Standards Assoc
17、iation, Inc., 5161 River Road, Bethesda, Maryland 20816, Phone: (800)638-8094. 2.10 SAE AIR1191, Performance of Low Pressure Ratio Ejectors for Engine Nacelle Cooling, November 1971. 2.11 SAE AIR1174, Index of Starting System Specifications and Standards, Revised April 1987. 2.12 Paper No. 841571, “
18、Pressurized Air Start System (PASS) for Small Gas Turbine Engines“, Jon P. Rominek: Beach, Calif. 1984. Presented at the 1984 Aerotech in Long 2.13 ICA0 Document of Internal Standards and Recommended Practices “Environmental Protection“ - Annex 16, Volume I - “Aircraft Noise“ First edition 1981. (At
19、tachment D to Annex 16.) 3. GENERAL BACKGROUND: 3.1 Uses: The uses that an APU might be put to on a commercial aircraft are as follows: a. b. Drive an AC generator for lights and power on the ground either during passenger occupation or during routine cabin cleaning and servicing. Provide bleed air
20、for air-conditioning on the ground. c. d. Supply bleed air or electric power for engine starting. Provide a backup in-flight system (such as electrical) in case one of the engine-driven systems becomes inoperative. Most utility power requirements on transport aircraft are supplied in flight by engin
21、e-mounted accessories such as electric generators or hydraulic pumps. compressors. With the introduction of the first generation of turbine-engined commercial aircraft such as the DC-8 and B-707, the air1 ines acquired ground power equipment to supply the pneumatic and electrical power required at a
22、ll airline terminals in order to maintain passenger comfort and convenience levels and to start the engines. Air for anti-icing and air-conditioning is bled from the engine -4- SAE AIR84204 91 m 7943725 0000083 B m SAE AIR4204 3.1 3.2 ( Con t i nued ) : By the time the second generation of jet aircr
23、aft were on the drawing boards, there was a desire to avoid dependence on ground power equipment for many reasons, including ramp congestion, operational performance, and availability/convenience limitations on flight planning. Fuel cost was a minor item in that period (approximately 10 cents per ga
24、llon), and small-turbine-engined APU equipment was available for these new aircraft. Thus, the second generation and subsequent wide-bodied commercial transports (the DC-9 and DC-10, the 8-727, 737, and 747, the A-300, the L-1011, the BAC 1-11 and Trident) all had integral onboard APU systems. The F
25、AA (Federal Aviation Administration) makes a distinction between Category I llEssential and Category II INonessential“ APUs. definitions, appearing in Reference 2.4, are as follows: a. 4.8 Essential APU: An APU which produces bleed air or power, or both, to drive accessories necessary for the dispat
26、ch of the aircraft to maintain safe aircraft operation. Their b. 4.15 Nonessential APU: An APU which may be used on the aircraft as a .matter of convenience, either on the ground or in flight, and may be shut down without jeopardizing safe aircraft operations. The dispatchability of a particular com
27、mercial airplane is constrained by the MEL (Minimum Equipment List) which defines the alternate equipment or systems that must be operable before the airplane can take off with passengers on board (Reference 2.5). aircraft, if one engine-driven electric generator is inoperative and an APU-driven gen
28、erator is on board, then normally the aircraft can be dispatched if the APU is qualified as “essential“ but not if it is “nonessential“. As an example, on a two-engine In order for an APU to qualify as essential, it must meet certain additional requirements such as ice protection, resistance to fore
29、ign object damage, and the survival of a rigorous endurance test. defined in Reference 2.4. Those requirements are Military transports dont necessarily meet the FAA requirements or vice versa, although military conversions of commercial aircraft may utilize the same equipment. Airborne APUs develope
30、d directly for military application may have to meet the requirements of Reference 2.6. Descri p t i on : Modern APUs are powered by internal combustion turbines with either a centrifugal or axial flow compressor or both. There may be an integral “load compressor“ driven by the same shaft as the eng
31、ine compressor. a load compressor is not supplied with the power unit, air is obtained for starting the main engines and for cabin conditioning by bleeding the APU compressor. Where An APU usually comes equipped with a gearbox as a means to drive accessories such as an electric generator and hydraul
32、ic pumps if required. -5- SAE AIR*4204 91 7943725 0000084 T SAE AIR4204 3.2 (Continued): Other than the APU itself, the bulkiest items related to the APU installation are the air inlet (induction) system and the turbine exhaust system. absorbent liner to keep APU noise to acceptable levels. Cooling
33、air must be supplied to the generator, the oil cooler, the compartment in general and, in some cases, to a shroud enclosing the exhaust duct. Lines are required to carry high-pressure air from the APU compressor to the engine starters and the air-conditioning system. used, the compressor is matched
34、to the turbine assuming a normal quantity of bleed. However, some operating conditions may not require enough bleed to keep the compressor operating within the surge limits. valve“ with an overboard line is provided to bleed additional air to keep the APU operating within the stable envelope. Both t
35、he inlet and exhaust ducting may require an acoustically Where compressor bleed is Therefore, a “surge If hydraulic power is to be supplied directly by the APU, a pad can be provided on the gearbox. However, most modern transports do not require a direct hydraulic drive on the APU. engine-mounted pu
36、mps under all normal flight conditions, and on the ground by electric-driven pumps. generator and possibly one for a cooling-air fan. requirements during ground operations are normally satisfied by the APU via the electrical generator. Hydraulic power in flight is provided by The APU gearbox typical
37、ly has a pad for the The hydraulic power Though it is possible to provide pneumatic power from a compressor mounted on the gearbox, it is seldom done because of the reduced efficiency and additional weight. Centrifugal compressors can run at the same speed as the APU engine compressor so it is not n
38、ecessary to go through a gear train to reduce the speed. An example of an APU with an integral load compressor is shown by Figure 1. Two configurations using compressor bleed are shown by Figures 2 and 3. Since, in any APU installation, fuel must be present in close proximity to potential sources of
39、 ignition, the APU is considered a fire zone and must be designed as such, separated from other areas of the airplane by firewalls. An example of an APU installation, showing most items that require appreciable space, is shown by Figure 4. 4. INSTALLATION CONSIDERATIONS: A primary consideration in l
40、ocation and design of the APU installation must be safety. failures must be included to preclude failure of: (1) aircraft primary structure, (2) fuel tanks, and (3) operability of aircraft systems. These topics are discussed in 4.2.1 and 5.1. Proper consideration for the possibility of fires and rot
41、or -6- - - - . - - . . - _. SAE AIR*4204 91 7943725 0000085 1 M SAE AIR4204 AIR INLET PLENUM COMPRESSOR IGNITOR FIGURE - Cross Section of APU with a Bleed Load Compressor -7- L SAE AIR*4209 91 7993725 0000086 3 H SAE AIR4204 FIGURE 2 - Cross Section of an Integral Bleed Air APU -8- - -_ SAE AIR*q204
42、 91 m 79q3725 0000087 5 m SAE AIR4204 LOW PRESSURE COMPRESSOR BLEED AIR DUCT HIGH PRESSURE COMPRESSOR HIGH PRESSURE TURBINE LOW PRESSURE TURBINE VARIABLE TURBINE NOZZLE ACCESSORY SECTION OUTPUT SHAFT FIGURE 3 - Operating Principles of a Twin-Spool APU SAE AIR*4204 91 W 7943725 0000088 7 W SA AIR4204
43、 FIGURE 4 - Example APU Installation - 10 - . SAE AIR*4204 91 W 7943725 O000089 9 SAE AIR4204 4.1 Output: The initial determination for an APU installation is the size of the unit to be installed. satisfied. The general load categories are as follows: That means determining the power requirements to
44、 be a. Electrical b. Pneumatic c, Hydraulic Hydraulic operations on the ground are usually powered by electric motors, so with respect to APU sizing they become part of the electrical load. 4.1.1 4.1.2 Electrical: The electrical load which will be required of the APU generator is calculated from the
45、 electrical requirements of the airplane while on the ground and in certain flight conditions, such as short-circuit or fault-clearing loads. A list of typical loads is shown in Table 1. The total of the connected loads is unrealistically high for design purposes because it assumes that all the indi
46、vidual loads peak at the same time. The total of the average loads is not necessarily a good criterion for sizing the generator either. The generator capacity normally must be determined as a matter of judgement and may come out somewhere between connected and average loads. Where possible, the APU
47、generator capacity will be made to match that of the generators on the main engines so that common parts can be stocked. However, before that is done, a careful analysis of the electrical loads should be made and the possibility of electrical growth should be considered to assure that future version
48、s of the airplane will not be restricted by the APU generator. An example of the electrical load requirement for a large commercial transport is shown in Table 1. Pneumatic: Pneumatic power is required for engine starting and air-conditioning on the ground and may be required for air-conditioning in
49、 flight and also anti-icing where bleed air is used for that purpose. The total capacity of the system must be sized to accommodate both electrical and pneumatic loads under the most severe condition. Table 2 shows a typical set of ground pneumatic requirements at three environmental conditions for a large commercial transport. It is assumed that full electrical load is applied at the same time. SAE AIR4204 TABLE 1 - Example Electrical Load Analysis (KVA) Connected Average Av er age System Load Flight Load Ground Load Avionics Electri cal Hydrau
