1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and enginee ring sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefr
2、om, 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 invit es your written comments and suggestions.Copyright 1999 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.
3、S.A.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8510 FAX: (724) 776-0243TO PLACE A DOCUMENT ORDER: (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS: http:/www.sae.org400 Commonwealth Drive, Warrendale, PA 15096-0001AEROS PACE INFORM ATION REPORTSubmitted for recognition as an American National Sta
4、ndardAIR1639 RE V. AIssued 1981-10Reaffirmed 1988-04Revised 1999-03Safety Criteria for Pneumatic Starting SystemsFOREWORDChanges in this revision are format/editorial only.1. SCOPE:This SAE Aerospace Information Report (AIR) presents safety criteria for pneumatic type engine starting system design a
5、nd component hardware. Included are safety criteria in design of both starter control valves and starters as well as in design of airframe control systems. Safety topics concern starter valve operation and material application, airframe controls and instrumentation installations and starter rotor in
6、tegrity and containment.2. REFERENCES:2.1 Applicable Documents:The following publications form a part of this document to the extent specified 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
7、 order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.2.1.1 SAE Publications: Available fr
8、om SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.AIR1467 Gas Engine Limited Starting SystemsSAE AIR1639 Revision A- 2 -2.2 Definitions:ROTOR: The entire rotating assembly with the exception of accessory drive shafts and gears.HUB: The inner portion of the rotor.BLADE: Elements of the turbin
9、e rotor which convert gas energy to mechanical energy.MAXIMUM NORMAL OPERATING SPEED: The maximum defined cutout speed including all tolerances and overshoot.MAXIMUM FREE RUN SPEED: Maximum free run is the operation of the starter with no-load on the output shaft in combination with any single failu
10、re of the intended pneumatic power source or starter control system which produces the highest free run speed including the effects of altitude. Any speed limiting device which is uncheckable shall be considered as having already failed when determining the maximum possible free run speed. The no-lo
11、ad condition can occur due to failure of the starter control valve to close because of a valve or system malfunction, a sheared output shaft, or by opening the starter control valve while the engine is operating with the clutch disengaged.LOW CYCLE FATIGUE: Low cycle fatigue results from high stress
12、 which can be below or above the proportional limit of the material but higher than its endurance strength.HIGH ENERGY FRAGMENTS: A high energy fragment is considered as any fragment which has sufficient energy to pass through a shield of soft aluminum with a thickness of 0.040 inch (1.016mm) maximu
13、m during the test demonstration.OVERSPEED: The speed at which a rotor exceeds its yield limit.3. GENERAL:Several methods of starting and motoring turbine engines are available. Some of the more common methods include hydraulic, electric, and pneumatic starting. This report presents the safety guidel
14、ines for design of a pneumatic system. A pneumatic system basically consists of an air turbine mounted on the engine accessory gearbox which is supplied compressed air from either an onboard or external compressed air source. A pneumatic shutoff valve is normally installed in the airframe to control
15、 operation of the starter.The most effective method to improve starting system design safety is to minimize or eliminate those system or component failures which have been shown to be the major contributors to unsafe failures of the starter turbine. Most unsafe failures of the starter are caused by
16、unwanted and undetected rotation of the air turbine and/or the inability to isolate the air turbine if unwanted rotation occurs. Uncontrolled rotation of the turbine can be a result of failure of the pneumatic valve in the open position, failure of the starter over-running clutch (if equipped) which
17、 causes the starter to be driven by the engine, or failure of the cutout switch (if equipped) to terminate the start cycle. Undetected turbine rotation can be a result of insufficient or unreliable instrumentation to provide a warning of a system or component failure.SAE AIR1639 Revision A- 3 -4. ST
18、ARTER VALVE DESIGN CONSIDERATIONS:The starter valve should be designed to the maximum extent possible to assure that it closes in the event of a failure. Precautions which should be considered include (1) use of anti-corrosive material for moving parts, (2) dynamic studies of valve operation, (3) ar
19、rangements which do not expose the solenoid and its poppet to system pressure and contamination and (4) a design which minimizes contamination effects upon the valve actuator components.Methods which are effective in assuring that the valve will be closed in the event of failure include designs wher
20、e (1) the valve is spring loaded closed, (2) inlet pressure aids in closing the valve with the solenoid de-energized, (3) use of mechanical advantage techniques for multiplication of forces between actuator and valve element, and (4) if the valve is a butterfly type, the butterfly is aerodynamically
21、 loaded to the closed position. The valve should include a valve position indicator switch which accurately provides a signal when the valve is in the “not closed” position. Actuation of the switch should be mechanical and detect valve position rather than a signal which only senses that the valve i
22、s told to go close.5. AIRFRAME DESIGN CONSIDERATION:5.1 Controls and Instrumentation:The airframe controls should be reviewed for failure which would permit the starter to remain energized when not selected. Separation of electrical leads (to prevent shorting) and methods employed in soldering and i
23、nsulating are also important design review details. Instrumentation should be provided to indicate when the pneumatic shutoff valve is “not closed”. Also, if the start system is such that the failure of any single component may activate the starter, a warning device should be provided to alert the c
24、rew to failure of a component or starter activation.5.2 Installation:Combustible fluid lines should be located as far as practical from the starter to minimize the possibility of combustible fluid contact with the starter in the event of failure. Precautions should be taken to minimize starter exhau
25、st impingement in the vicinity of combustible fluids or vapor. The exhaust gases should be ducted outside the engine compartment if they are corrosive or exceed 700F (371 C).SAE AIR1639 Revision A- 4 -6. STARTER DESIGN CONSIDERATIONS:In addition to the measures taken to minimize starting system fail
26、ures, precautions should be taken to insure that in the event of a failure the effects will not be hazardous to personnel or equipment. The precautions taken in starter design often vary depending on the intended source of compressed air as related to maximum operating temperature. For the purpose o
27、f this report, design safety considerations will be shown separately for moderate temperature applications (below 1000 F 538C) and for high temperature application (above 1000 F 538 C). It is often not practical for cost and weight considerations to apply the same criteria for high temperature appli
28、cations that are used in moderate temperature applications. Moderate temperature air sources include most ground carts, onboard APUs and moderate temperature engine bleed air. Sources for high temperature compressed air may include hydrazine gas, solid propellant cartridge gas or high temperature (o
29、ver 1000 F 538 C) engine bleed air.6.1 Moderate Temperature Applications:6.1.1 Parts Containment: The starter should be capable of containing all high energy fragments within its envelope and remain on its mount should a failure of any of its components occur. Other containment criteria are: Any fra
30、gments emitted from the starter exhaust should not constitute a fire hazard nor have sufficient energy to harm equipment, structure, or personnel. If failure of the rotor bearing(s) will allow an axial shift of the rotor such that containment provisions are negated, a means should be provided to pre
31、vent this occurrence. The design should be such that rotation of the outer case of the starter which could shear ducts or other attachments is prevented. Containment devices (rotating or stationary) should not require maintenance for proper operation. A failure of a complete rotor (maximum energy tr
32、i-hub burst) should be contained at any speed up to maximum operating speed.6.1.2 Rotor Integrity:6.1.2.1 Low Cycle Fatigue: The starter rotor should be designed to and constructed to minimize the probability of low cycle fatigue. As a minimum, the rotor hub must be designed to withstand stresses wh
33、ich occur during cycling from rest up to the maximum normal operating speed with maximum inlet temperature for two times the number of start cycles which can occur throughout the operational life of the starter. The rotor hub must also withstand 5 percent of the number of operational life start cycl
34、es when cycled from rest to the maximum free-run.SAE AIR1639 Revision A- 5 -6.1.2.2 High Cycle Fatigue: The starter rotor should be designed such that it is capable of operation to infinite life without fatigue failure when cycled from rest to the maximum normal operating speed and to 5 percent of o
35、perational life start cycles when cycles from rest to maximum free run speed for two minutes for each cycle. It shall be demonstrated that high cycle fatigue stress is below the endurance limit of the material. For demonstration purposes, infinite life may be considered as 10 7 cycles for ferrous ma
36、terial and 10 8 for other than ferrous material.6.1.2.3 Minimum Yield Speed: The minimum yield speed of the turbine rotor shall be greater than the maximum free running speed.6.1.2.4 Proof Speed: The starter rotor proof speed shall be less than the minimum yield speed and greater than the maximum fr
37、ee running speed.6.1.3 Free Run: The starter shall withstand a minimum of 10 cycles (not in succession) at the maximum free run speed without failure for one minute.6.1.4 Engaging Mechanism Failure: Unless it can be shown that the starter engaging mechanism is fail safe, the unit should incorporate
38、one of the provisions defined below to prevent a hazardous condition in the event the starter rotor is driven by the engine due to failure of the engaging mechanism. An automatic emergency starter drive disengagement mechanism should be incorporated to effect emergency disengagement of the starter f
39、rom the engine in the event normal disengagement does not occur.The disengaging mechanism should actuate below maximum free run speed and be so designed that removal of the starter from the engine pad shall be required to effect re-engagement of the starter drive. An attempted start, after an emerge
40、ncy disengagement has been experienced should not cause damage to the starter or engine. Containment of a maximum energy tri-hub burst (3 piece 120 segments) should be provided up to the starter rotor burst speed or to maximum speed at which the engine can drive the starter rotor due to a failed eng
41、aging mechanism. Containment should also be provided for the remaining rotating parts up to the maximum possible driven speed. The starter rotor should incorporate rim and blade fusing such that at a predetermined speed the rim and blades shall separate from the turbine hub. The minimum fuse burst s
42、peed should be greater than the maximum free run speed and the fused parts shall be contained at the fuse burst speed. Containment should also be provided for the remaining rotating parts up to the maximum possible driven speed.SAE AIR1639 Revision A- 6 -6.2 Design Consideration For High Temperature
43、 Air Applications:6.2.1 Compressed Air Supply System: The high temperature (1000 F 538 C or above) compressed air supply system should be limited or controlled to prevent turbine wheel overspeed during free run under the worst conditions of pressure, temperature, and altitude.6.2.2 System Safety Pro
44、visions: If the compressed air supply system can provide energy levels in excess of the design criteria established in 6.2.1 above, additional overspeed protection and/or containment provisions should be provided to establish a safe condition in the event a free run occurs. Additional safety feature
45、s that may be utilized are: Overspeed protective device which senses turbine wheel speed and causes a reduction in the energy being supplied, or spoils the turbine efficiency. Fused rim and/or blades below high temperature free run speed but above maximum normal operating speed with containment at t
46、he fused speed. An overpressure device to limit the energy supplied to the starter. Establish a specific life limit (start cycles) for the turbine wheel based on the operating temperatures and the materials used. Provide tri-hub containment to the high temperature maximum free run speed or burst spe
47、ed, whichever is lower.6.2.3 Installation: In some installations where the high temperature compressed air is generated by decomposition of certain elements, special precautions must be observed in the installation design, operation, handling and storage of the system components. These precautions are outlined in AIR1467, Gas Engine Limited Starting Systems.PREPARED BY SAE COMMITTEE AE-6, STARTING SYSTEMS & AUXILIARY POWER
