1、_ SAE Technical Standards 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 applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions.Copyright 2013 SAE International All rights reserved. No part of this pu
3、blication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970
4、 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR4994AAEROSPACEINFORMATION REPORT AIR4994 REV. AIssued 1996-01 Reaffirmed 2007-11
5、 Stabilized 2013-11 Superseding AIR4994 High Pressure Pneumatic Compressors Users Guide For Aerospace Applications RATIONALEThis document has been determined to contain basic and stable technology which is not dynamic in nature. STABILIZED NOTICE This document has been declared “Stabilized“ by the S
6、AE A-6C6 Power Sources Committee and will no longer be subjected to periodic reviews for currency. Users are responsible for verifying references and continued suitability of technical requirements. Newer technology may exist. Copyright SAE International Provided by IHS under license with SAENot for
7、 ResaleNo reproduction or networking permitted without license from IHS-,-,-1. SCOPE:Gas compressors (air and other compressible fluids) have been used sporadically since the 1940s for various utility functions in aerospace applications. They have been used to provide power to gun purge and drive sy
8、stems, engine or APU starters (recharge accumulators), reservoir pressurization, cockpit pressurization, braking systems, canopy seals, engine control devices, landing gear activation, and boosted flight controls (see Table 1). In current state-of-the-art aircraft, most pneumatic system power is ext
9、racted from a stage of compression in the turbo-jet engine. As more and more demands are put on new generation engines for fuel economy and performance there is an increasing need for a new source of pneumatic power. This document is intended to describe current state-of-the-art technology in compre
10、ssors, define the limitations, discuss enhancements needed and attempt to predict the needs of the future.1.1 Purpose:The information contained herein was compiled to describe what technology level currently exists, typical applications, user experience and limitations and recommendations for develo
11、pment of new technology necessary to meet projected demands of the future. Those who should benefit from this document would be:a. System integrators responsible for utilizing gas compressors in new aircraft systems.b. Designers not familiar with the capabilities and limitations of airborne compress
12、ors.c. Advance systems development designers needing trade-off information for new systems concepts.d. Compressor design engineers with responsibility for up-grading existing designs.1.2 Field of Application:This SAE Aerospace Information Report (AIR) establishes the characteristics of high pressure
13、 piston type pneumatic compressors. The focus is to document data and recommendations for use in aerospace applications.SAE INTERNATIONAL AIR4994A Page 1 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from
14、 IHS-,-,-TABLE 1 - High Pressure CompressorsAirborne Applications1.2.1 Classification: High pressure reciprocating piston compressors are positive displacement devices with two or more stages with output pressures of 1000 psi (6890 kPa) and above. Typical compressors are two to four stages with outp
15、ut pressures up to 3000 psi (20 700 kPa). SeeFigure 1.1.2.2 Types: This document will focus on piston-type, positive-displacement compressors rather than rotary-screw or roots-type which are typically used in much higher flow applications.1.3 Lubrication:1.3.1 Wet Sump: Lubrication and cooling provi
16、ded by a wet sump which lubricates the pistons, connecting rods, and bearings.1.3.2 Oil-free: Includes piston-type activating mechanisms with no lubrication on the pistons or valves. Bellows type seals and wipers are used to isolate the pistons from the sump oil.SAE INTERNATIONAL AIR4994A Page 2 of
17、12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-FIGURE 1 - Typical 3000 psi Aerospace Compressor (4 Stage)SAE INTERNATIONAL AIR4994A Page 3 of 12_Copyright SAE International Provided by IHS under
18、license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1.3.3 Oilless: A compressor that uses no oil. All bearings are pre-packed and sealed.1.4 Capacity:Compressor output performance is typically specified in standard cubic feet per minute or SCFM at an ap
19、propriate discharge pressure in pounds per square inch (psi) or kilo pascals (kPa). Small capacity units are usually specified by mass flow (lb/min), (Kg/min), and an appropriate discharge pressure. Typical applications range in capacity up to 17 SCFM and 4800 psi (32 600 kPa).1.5 Compressor Driver:
20、Typical drive mechanisms include:a. Transmission (see MIL-C-6388)b. Engine (see MIL-C-6388)c. Hydraulic motor (see MIL-C-6388)d. Pneumatic (turbine) (see MIL-P-5518)e. AC/DC electric motor (see MIL-C-6591)2. APPLICABLE DOCUMENTS:The following publications form a part of this document to the extent s
21、pecified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes preced
22、ence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.2.1 U.S. Government Publications:Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.MIL-P-5518 Pneumatic Syst
23、ems, Aircraft; Design, Installation, and Data Requirements forMIL-C-6388 Compressor, Air, Aircraft, Shaft Power Driven, General Specification forMIL-C-6591 Compressor Unit, Aircraft, Electric Motor Driven, General Specification forMIL-P-8564 Pneumatic System Components, Aeronautical, General Specifi
24、cation forMIL-STD-810 Environmental Test MethodsSAE INTERNATIONAL AIR4994A Page 4 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3. SYSTEM INTEGRATION CONSIDERATIONS:When incorporating a compr
25、essor into an airborne application, there are numerous installation and environmental compatibility issues that need to be considered. MIL-P-8564 should be utilized as a guide for interfacing with other pneumatic system components.3.1 Installation:a. Mounting: Typical 2 to 4 stage compressors induce
26、 torsional vibrations and need to be mounted on shock/vibration mounts if possible.b. Noise: Piston ripple is a source of excessive noise and can exceed 75 dB. The system designer needs to consider the location and effect on crew members and maintenance personnel in the proximity of the compressor.c
27、. Compressor Drive: Splined shafts are considered to be the best design for extended life. The drive mechanism should have adequate inertia and structural strength to absorb the compressor torque pulsations. Failure to examine both for compatibility could result in premature driver failures. Conside
28、ration should be given to the use of nonmetallic spline adapters (muffs) which can preclude fretting corrosion and fatigue and extend the life of the coupling.d. Moisture Separators (Interstage and Post Compression): Space should be included for the installation and servicing of moisture separators
29、since routine servicing will likely be necessary since cooling and compression results in water coalescing. A precooler upstream of the separator should be utilized to assure efficient performance. Moisture separators of two types may be considered; one way desiccant or a regenerating type. The desi
30、ccant of the regenerating type has the advantage of not requiring periodic service. The one way desiccant type is simpler and when used up, the desiccant is removed and replaced.e. Cooling: Depending on the application, the compressor may be air or liquid cooled. If air cooled, consideration needs t
31、o be given to assure ambient air is able to flow across the compressor across inlet and exhaust passages or ducting. The compressor designer should be capable of providing the minimum air flow requirements for each duty cycle application.3.2 Environmental:a. Temperature: As in other mechanical equip
32、ment, controlling temperature rise is a major factor in predicting performance and life. Present materials used in piston type compressors will support ambient temperature to 165 F (73 C) at maximum duty cycle conditions and-65 F (-54 C ) at minimum temperatures. Exotic materials may be required for
33、 higher temperatures.b. Vibration/Shock: The particular compressor application must reflect expected levels of vibration and shock. The MIL specification or detail specification should define the method, duration, and amplitude of testing. If vibration isolators are utilized, they should be included
34、 as part of the actual test.SAE INTERNATIONAL AIR4994A Page 5 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3.2 (Continued):c. Sand and Dust: The compressor cooling fan acts as a vacuum gener
35、ator and will accelerate sand erosion. Care should be taken when conducting the test to assure the sand is ingested in a uniform dispersal pattern.d. Salt Spray: Typical state-of-the-art compressors use ductile iron for cylinder sleeves. If a particular application requires exposure to sea water env
36、ironment, the designer may want to consider a CRES material to preclude corrosion of the external and internal parts exposed to the environment. When using corrosion resistant steels, consideration must be given to the reduced heat transfer capabilities over a typical iron cylinder sleeve.e. Inlet F
37、iltration: If the particular application may experience any of the aforementioned environments the designer should consider the use of an inlet filtration device.4. DESIGN AND CONSTRUCTION:A high-pressure compressor, whether for air or another gas, may consist of the following additional components:
38、 bleed valve, back-pressure valve, relief valve, check valve, pressure switch, unloader valve, and drive motor as shown in the schematic in Figure 2. In the case of air compression, and some other gases, an inlet filter and a moisture separator/drier system will be required. Also, in some cases, an
39、inlet pressure regulator will be required. On lubricated compressors, an oil separator may be required downstream of the compressor.Since reciprocating compressors of this type run relatively slowly, a speed reducer may be required. As the drive rotates the compressor, the working fluid medium is su
40、ccessively compressed in several stages. It leaves the last stage and enters the moisture separator (some applications require interstage moisture separation), then a chemical drier (if so equipped). It then encounters the back-pressure valve which regulates the pressure of the working fluid medium
41、before entering the rest of the system.The relief valve prevents stage over-pressurization; the bleed valve allows relief of pressure in the system for maintenance. The unloader valve dumps the high-pressure trapped between the compressor and the check valve after the compressor stops running, thus
42、purging the trapped gas from the moisture trap and chemical drier. This action causes the moisture separator to dump and also purges the lines if the separator should be located remote from the compressor. Some electric motor driven systems use a back pressure valve to maintain a minimum back pressu
43、re on the moisture removal components to insure more effective separation, since the efficiency of these items is proportional to the absolute pressure. Hence, the chemical drier life is extended, especially during the initial stage of the charging process. The pressure switch starts and stops opera
44、tion as required to keep the system storage vessel at the desired pressure.SAE INTERNATIONAL AIR4994A Page 6 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-FIGURE 2SAE INTERNATIONAL AIR4994A P
45、age 7 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4. (Continued):In general, lubricated compressors can be used where oil in the discharged working fluid is not a problem in a particular ap
46、plication. As a rule of thumb, such lubricated compressors can be used for air or inert gases where no more than one pressure vessel is in the system. Some danger will still exist from compression ignition of oil in the vessel (from possibly connecting an external high-pressure source and suddenly pressurizing the vessel from low pressure). Such risk must be analyzed for each application. There is also a risk involved when pressuriz
