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 RECOMMENDED PRACTICESubmitted for recognition as an American National St
4、andardARP949 RE V. BIssued 1969-05Reaffirmed 1988-10Revised 1999-03Turbine Engine Starting System Design RequirementsFOREWORDChanges in this revision are format/editorial only.1. SCOPE:This SAE Aerospace Recommended Practice (ARP) defines and establishes a standard presentation of data for gas turbi
5、ne propulsion engine starter characteristics in graphs and curves. The data presentation applies to both pneumatic and hydraulic energy source starting systems.1.1 Purpose:This recommended practice is intended to define and establish, where applicable, a standard presentation of the engine character
6、istics required for the determination of a satisfactory starting system for aircraft gas turbine engines.2. REFERENCES:2.1 Related Publications:The following publications are provided for information purposes only and are not a required part of this SAE Aerospace Technical Report.AIR781 Guide for De
7、termining Engine Starter Drive Torque RequirementsAS972B Spline Details, Accessory Drives and FlangesAIR713A Guide for Determining, Presenting, and Substantiating Turbine Engine Starting and Motoring CharacteristicsARP906 Glossary, Aircraft Engine Starting and Secondary Power SystemsAIR1087 Aircraft
8、 Accessory Drag Torque During Engine StartsAIR1639 Safety Criteria for Pneumatic Starting SystemsAIR1467 Gas Energy Limited Starting SystemsAIR1174 Index of Starting System Specifications and StandardsAIR1466 Hydraulic Energy Limited Starting SystemsSAE ARP949 Revision B- 2 -3. DISCUSSION:A satisfac
9、tory starting system is defined as that system which will assure acceleration from zerorpm(+_ rpm -_ rpm to account for a decelerating engine or an engine windmilling in the reverse direction of rotation) for ground starts, or windmill speed for inflight starts, to idle speeds within established lim
10、its for the engine or other starting system components for all required conditions.4. REQUIREMENTS:To insure a satisfactory starting system design, the engine characteristics, as well as anticipated operating limitations, must be defined in detail. If at the end of the design process, other operatio
11、nal restrictions are determined, these restrictions should be included in the engine characteristics. Wherever applicable, the basis for performance estimates should be indicated as being determined empirically or theoretically. These characteristics and limitations include the following:4.1 Engine
12、Supplied Torque:Engine supplied torque shall be defined as unfired and fired torque in sufficient detail as to clearly describe the effects of ambient temperature, altitude, ram pressure ratio (flight speed), engine acceleration rate, customer compressor bleed, and customer power extraction as appli
13、cable to the particular application. The effects of engine required compressor bleed and power extraction shall be included in the basic engine torque. Figure 1 shows the unfired and fired torque characteristics versus starter drive speed at sea level static, with zero customer mechanical or pneumat
14、ic power extraction, for cold, standard, and hot ambient temperatures.The engine torque characteristics as modified for the altitude effect shall be presented in the format of Figure 1 or 2 with the altitude and temperature noted. The torque characteristics may be defined at as many altitudes as req
15、uired for the particular application.Figure 3 presents the pneumatic power extraction torque correction to be applied algebraically to the engine torques of Figure 1 to determine the net engine torque. If required, additional corrections may be supplied to define these characteristics as a function
16、of altitude.Customer accessory power extraction (torque) applied to the engine for accessories or functions not included in the engine-supplied torque curve should be added algebraically to the engine-supplied torque curve.Figure 4 shows the engine torque versus speed as a function of ram pressure r
17、atio or flight speed at a particular altitude. This figure can be repeated at selected altitudes to describe the engine inflight starting torques throughout the inflight starting envelope.The engine inflight starting envelope should be shown as in Figure 5.SAE ARP949 Revision B- 3 -4.2 Light-Off Cha
18、racteristics:Light-off characteristics are defined to establish the engine speed range in which (1) turbine temperature transients are within acceptable limits, and (2) the required fuel/air ratios for reliable light-offs are present. The light-off characteristics may vary with altitude, ambient tem
19、perature, acceleration rate, starting procedure, etc., and if so, must be defined as a function of the particular variables. These expressions are too varied to delineate in detail and only three representative examples are indicated:(1) Light-off speed greater than _ percent speed. This expression
20、is valid to protect the turbine from light-off transients and in those cases where no upper limit is required.(2) Light-off speed greater than _ percent and less than _ percent speed. This expression illustrates the case in which the lower speed is utilized to protect the turbine from light-off tran
21、sients as in (1), but imposes an upper limit to insure a proper fuel/air ratio for ignition.(3) Light off occurs _ seconds after fuel on at _ percent speed. This expression is used when a particular start procedure is specified and describes the fuel and ignition characteristics when using the proce
22、dure.(4) Altitude effects can be expressed by varying the minimum and maximum idle speeds, the speed at which fuel and ignition are applied, plus the time required for ignition delay, if applicable.(5) Automatic relight functions can be established to provide re-start initiation when, for a given po
23、wer lever angle (1) engine speed drops below a specified level, or (2) the measured exhaust gas temperature (EGT) drops below the scheduled EGT by a predetermined rate.4.3 Hot Section Parts Exposure to Starting Temperatures:The time duration of the exposure of the hot section parts to starting tempe
24、ratures is a function of the acceleration rate from light-off to idle speed. If required for engine protection and/or life, the minimum acceleration (torque) must be defined over the applicable speed range and climatic conditions, such as ambient temperature, altitude, and/or wind conditions. These
25、torques represent net torques which provide a minimum acceleration rate that is the algebraic sum of engine, accessories, and starter torques. These may be a constant value or may vary with engine speed over a specified speed range.SAE ARP949 Revision B- 4 -4.4 Crosswind and Tailwind Limitations:Lim
26、itations imposed by wind direction and/or velocity may have an adverse effect upon the starting characteristics, particularly engine torque, turbine temperatures, and light-off characteristics. Limitations evolving from the wind effects and corrective measures, when required, must be defined for the
27、 particular application.The limitations may be expressed as simple statement, such as: “Normal starts may be accomplished for crosswind and tailwinds up to _ knots. For wind velocities greater than _knots, special start procedures must be used.”The limitations may be expressed in graphical form, as
28、shown on Figure 6, when the effect upon starting performance varies with the direction and velocity of the wind.4.5 Windmill Power Extraction:The mechanical power extraction capability shall be defined at the specified flight conditions as required by the particular application. These data are requi
29、red to define emergency power generation, either electrical or hydraulic, and to provide the basis for accessory load effects on windmill starting.Figure 7 illustrates the presentation of these data as a function of flight speed or Mach number over the applicable engine inlet pressure range. Additio
30、nal data may be required for cases where the corrected torque varies significantly with altitude or ambient temperatures. These data may be presented at the several altitudes and/or ambient temperatures which will define the engine capability over the inflight starting envelope.4.6 Engine Idle Speed
31、s:Engine idle speeds are to be defined (1) to specify the termination point or points of the start, (2)to insure no interference with the operational use of aircraft accessories, and (3) to provide a limit for defining starter cutout speed. Idle speed may be defined as simple statements of either ph
32、ysical or temperature corrected speed, or if idle speed is continuously variable with ambient temperature or altitude, a graphical presentation as shown in Figure 8 may be used.4.7 Starter Cutout Speed:Starter cutout speed is established at a speed less than idle speed and above the speed where engi
33、ne start acceleration torque exceeds drag and the engine becomes self-sustaining. Minimum starter cutout speed may be defined as a function of engine speed, such as _ rpm greater than self-sustaining speed, or as that speed which provided _ lb-ft net accelerating torque from the engine.SAE ARP949 Re
34、vision B- 5 -4.8 Starter Re-engagement Speeds:Re-engagements by the starter may be required to provide engine assist for motoring (to cool a hot engine, or purge an engine of unlit gases), or re-starting an engine while it is spooling down or windmilling (during flight). The windmilling speed, and m
35、aximum re-engagement speed shall be defined. Refer to Figure 5 for a definition of engine relight envelope where starter assist is required. The windmilling speed shall be estimated; or measured where flight data is available.4.9 Starter Impact Torque:Re-engagements by the starter cause impact torqu
36、es to be imposed on the engine drive train, and therefore, needs to be considered for design purposes. The maximum instantaneous impact torque limitation shall be established for this purpose. The engine data required to calculate the impact torque are listed in Paragraph 4.11 below. The method of c
37、alculating impact torque may be found in AIR781, Guide for Determining Engine Starter Drive Torque Requirements. The possibility of a starter “crash engagement” shall be considered in determining the starter drive torque limitation. It may be desirable to incorporate a shear section in the engine dr
38、ive pad or specify one for the starter to prevent damage to the engine drive train. The maximum rotor speed for re-initiation of cranking (re-engagement) shall be established to avoid engine or starter damage.(A “crash engagement” can occur due to system malfunction where after a start is made, and
39、the starter centrifugal clutch has disengaged, the air to the starter is left on allowing the starter to operate at no load free run speed; then when the engine is shut down, the clutch portion of the starter being driven by the engine will attempt to re-engage at its reset speed, but with the start
40、er input portion of the clutch operating at a very high speed, a “crash engagement” takes place, causing a very high impact torque which usually damages the starter.)4.10 Maximum Starter Pad Speed:The maximum starter pad speed at 100 percent engine speed shall be defined to allow the starter manufac
41、turer to design the starter overrunning mechanism to ensure starter integrity, and to analyze failure modes in the event of a component malfunction such as failure of the cutout switch to actuate, or failure of the engaging mechanism to disengage.SAE ARP949 Revision B- 6 -4.11 Engine Structural and
42、Rotating Component Characteristics:These characteristics shall include:(1) Mass polar moment of inertia of engine rotating parts at the starter drive, _ slug-ft 2 .(2) Gear ratio, starter drive speed/engine rotor speed, _.(3) Maximum torsional stiffness of the rotating engine parts, _ lb-ft/radian a
43、t the starter drive.(4) Maximum backlash of the rotating engine parts, _ radians at the starter drive.(5) Maximum instantaneous torsional limit of starter drive _ lb-ft.(6) Maximum continuous starter torque limit _ lb-ft.(7) Maximum starter drive speed for re-engagement _ rpm.(8) Starter drive pad c
44、onfiguration and direction of rotation.(9) Engine lubricant designation.(10) Engine fuel designation and limits, imposed, if any.(11) Engine 100 percent rotor speed referred to the starter drive pad.4.12 Shutdown Procedures:Requirements to use the starting system during engine shutdown, cooling, or
45、purging should be specified as to minimum or maximum speed, time duration, or whatever other limits are to be observed.PREPARED BY SAE COMMITTEE AE-6, STARTING SYSTEMS & AUXILIARY POWERSAE ARP949 Revision B- 7 -FIGURE 1 - Fired and Unfired Engine Torque Characteristicsand Effect of Ambient Temperatu
46、reSAE ARP949 Revision B- 8 -FIGURE 2 - Effect of Altitude on the Engine Torque CharacteristicsSAE ARP949 Revision B- 9 -FIGURE 3 - Effect of Customer Pneumatic Power Extractionon Engine Torque CharacteristicsSAE ARP949 Revision B- 10 -FIGURE 4 - Effect of Flight Speed on Engine Torque Characteristic
47、sSAE ARP949 Revision B- 11 -FIGURE 5 - Engine Relight EnvelopeSAE ARP949 Revision B- 12 -FIGURE 6 - Relative Wind Condition EnvelopeStandard Starting ProcedureSAE ARP949 Revision B- 13 -FIGURE 7 - Effect of Customer Power Extraction While WindmillingSAE ARP949 Revision B- 14 -FIGURE 8 - Effect of Ambient Temperature and Altitudeon Engine Idle Speed
