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1、AEROSPACE INFORMATION REPORT AIR5306 Issued2000-07 Inlet Airflow Ramps for Gas Turbine Engine Test Cells TABLE OF CONTENTS 1.SCOPE .2 1.1Purpose .2 2.REFERENCES .2 2.1Applicable Documents.2 2.2Symbols and Abbreviations .3 2.2.1 Parameters3 2.2.2 Abbreviations.3 2.2.3 Subscripts3 3.TECHNICAL BACKGROU
2、ND.4 3.1Cell Bypass Ratio 5 4.INLET RAMPS7 4.1Description.7 4.2Application.8 4.3Engine Room Requirements8 4.4Ejector Tube Requirements.9 4.5Model Test Results10 5.CONCLUSIONS .12 6.NOTES .12 6.1Patent Information .12 6.2Key Words .12 SAE Technical Standards Board Rules provide that: “This report is
3、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 therefrom, is the sole responsibility of the user.” SAE reviews each tech
4、nical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2007 SAE International All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in an
5、y 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: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: ht
6、tp:/www.sae.org Reaffirmed 2007-11 Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:52:03 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR5306 - 2 - 1.SCOPE: This SAE Aerospace Info
7、rmation Report (AIR) has been written for individuals associated with the ground-level testing of gas turbine engines and particularly for those who might be interested in upgrading their existing engine test facility to meet the airflow requirements for higher thrust engine models. The intellectual
8、 property rights on the material contained in this document are protected by US Patent Number 5,293,775 dated March 15, 1994 assigned to United Technologies Corporation, Hartford, Connecticut, USA. Any individual, or organization, attempting to use the system described in this document should get a
9、clearance from United Technologies Corporation, to avoid any potential liability arising from patent infringement. 1.1Purpose: To provide guidelines for inlet airflow ramps for gas turbine engine test cells. 2.REFERENCES: 2.1Applicable Documents: The following is a list of some applicable references
10、 and documents used in the preparation of this report: 2.1.1Freuler, R.J., Dickman, R.A., Current Techniques for Jet Engine Test Cell Modeling. AIAA-82- 1272, Presented at the 18th Joint Propulsion Conference, June 21-23, 1982, Cleveland, Ohio. 2.1.2De Siervi, F., Viguier, H.C., Greitzer, E.M., Tan,
11、 C.S., Mechanisms of Inlet-Vortex Formation, Journal of Fluid Mechanics, 1982, volume 124, pp. 173-207. 2.1.3Glenny, D.E., Pyestock, N.G.T.E., Ingestion of Debris into Intakes by Vortex Action, Ministry of Technology, 1970, Aeronautical Research Council, C.P. no. 1114. 2.1.4Clark, T., Peszko, M., Ro
12、berts, J., Muller, G., Nikkanen, J., United States Patent, Patent Number 5,293,775, March 15, 1994, Assignee: United Technologies Corporation, Hartford, Conn. 2.1.5“Design Considerations for Enclosed Turbofan/Turbojet Engine Test Cell“, SAE Aerospace Information Report AIR4869, Society of Automotive
13、 Engineers, Warrendale, Pennsylvania, Issued October 1995. 2.1.6“Modeling Techniques for Jet Engine Test Cell Aerodynamics“, SAE Aerospace Information Report AIR4827, Society of Automotive Engineers, Warrendale, Pennsylvania, Issued May 1993. 2.1.7“Test Cell Instrumentation“, SAE Aerospace Informati
14、on Report AIR5026, Society of Automotive Engineers, Warrendale, Pennsylvania, Issued November 1996. Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:52:03 MSTNo reproduction or networking permitted without license
15、from IHS -,-,- SAE AIR5306 - 3 - 2.1.8“Turbofan and Turbojet Gas Turbine Engine Test Cell Correlation“, SAE Aerospace Recommended Practice ARP741 Rev. A, Society of Automotive Engineers, Warrendale, Pennsylvania, Revised September 1, 1993. 2.2Symbols and Abbreviations: The following parameters, abbr
16、eviations, and subscript notations are used in this report: 2.2.1Parameters: LOSSpressure loss at vortex center Pttotal pressure Qdynamic pressure (1/2 V2) Vvelocity Wairflow rate Ptpressure difference between inlet Pt and vortex core Pt cell bypass ratio air density 2.2.2Abbreviations: Dinlet diame
17、ter FCfront cell ftfeet ft/sfeet per second Hengine centerline height kg/skilograms per second kNkiloNewtons lbm/spounds-mass per second mmeters SAESociety of Automotive Engineers 2.2.3Subscripts: BYPASScell bypass flow ENGengine ENGINEengine FCfront cell VORTEXinlet vortex Copyright SAE Internation
18、al Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:52:03 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR5306 - 4 - 3.TECHNICAL BACKGROUND: Due to the introduction of a new generation of high thrust turbofans
19、, stability and stall problems can be encountered when larger and more powerful engines are operated in an engine test facility. This is generally due to the momentary or steady formation of an inlet vortex. Inlet vortices form near the engine inlet bellmouth where local deceleration in airflow caus
20、es an adverse pressure gradient resulting in flow separation along the adjacent surfaces of ceiling, floor, or walls. An inlet vortex is formed when a stagnation point, due to velocity shear, exists in the vicinity of the engine inlet. Severe velocity and pressure distortion at the engine inlet plan
21、e will result where conditions are present that permit inlet vortex formation. Vortex ingestion by the fan can cause noise and small performance shifts while a vortex that enters the engine core is likely to cause compressor surge or stall. Severe engine damage can result from a compressor surge or
22、stall and, therefore, it is unacceptable to operate an engine for testing under conditions that permit this event to occur. Experiments conducted by Freuler and Dickman for jet engine test cell modeling concluded that inlet vortices can be suppressed by test cell operation at a bypass ratio (see 3.1
23、) of 0.8 or greater (2.1.1). Vortex formation from the cell floor has also been generally characterized to be a function of engine centerline height to inlet diameter (H/D) as described in references 2.1.2 and 2.1.3. The potential for vortex formation as a function of distance to engine room surface
24、s and inlet diameter applies to the adjacent walls and ceiling as well. Decreasing this ratio with the engine inlet bellmouth closer to the adjacent ceiling, floor or wall surfaces increases the potential for a vortex to form. Traditional test cell design practices recommend that an engine test cell
25、 should operate at a bypass ratio of 0.8 or greater to ensure that inlet vortex formation is adequately suppressed. As airlines and maintenance shops expand their services to include engine testing for higher thrust turbofans, a minimum bypass ratio of 0.8 may not be achieved within the existing fac
26、ility. Based on traditional design practices the solution to this problem is to construct a new and larger facility or to make significant modifications to the existing facility that will increase cell bypass ratio to the recommended 0.8 level. In either case, the major concern to the facility opera
27、tor with both of these options is cost. Significant capital expenditures are required for construction of a new test facility and the cost of modifications to increase cell airflow is dependent upon the work scope involved. Cell modifications to increase airflow can vary greatly from relatively mino
28、r adjustments to the existing equipment such as increasing the open area or perforations in the exhaust basket, to extensive facility reconfigurations where replacements are required for major structural components such as the inlet plenum, ejector tube, or exhaust stack. In order to meet the requir
29、ements for the new generation of high thrust turbofans, Pratt & Whitney has developed an inlet ramp system. This patented system (2.1.4) minimizes the occurrence of airflow stagnation which can cause an inlet vortex to form at the adjacent wall, floor or ceiling surfaces of the test cell. With the i
30、nlet ramp system in place an engine can be operated in a test cell with a bypass ratio as low as 0.4. This is significantly lower than the 0.8 level which is generally considered acceptable for vortex free engine operation and provides an alternative solution that requires no modifications to increa
31、se cell airflow. Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:52:03 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR5306 - 5 - 3.1Cell Bypass Ratio: Cell bypass ratio is defined
32、 as the ratio of airflow that passes around the engine to the airflow that enters the engine bellmouth. Cell bypass ratio is an important cell performance parameter for describing test cell aerodynamic characteristics. Cell bypass ratio can be expressed in terms of front cell airflow and engine airf
33、low and it is calculated as shown in Equation 1: (Eq. 1) where: WFC = Front cell airflow WENG = Engine airflow Cell bypass ratio is a facility airflow characteristic that may be easily confused with a similar term “bypass ratio“ which is used for describing a turbofan engine design characteristic. B
34、ypass ratio as it applies to turbofan engine performance is the ratio of engine airflow from fan discharge to the engine airflow attributed to core engine discharge. Cell bypass ratio describes the induced cell airflow that occurs because the engine and test cell work together as an ejector pump. Fi
35、gure 1 illustrates two cell bypass ratio conditions, with the dark shaded areas representing engine airflow (WENGINE) and the light shaded areas representing the airflow from the front cell that bypasses the engine (WBYPASS). The two bypass airflow conditions illustrated in Figure 1 represent the fl
36、ow fields for a small and a large engine operated at take-off thrust. In both cases the bypass airflow cross-sectional area increases as it passes the engine inlet, and this diffusion of the bypass streamtube results in a static pressure rise which may cause flow separation. In the case of the small
37、er engine with the 150% cell bypass ratio the adverse pressure gradient is small and no flow separation occurs. But for the larger engine with 30% cell bypass ratio the adverse pressure gradient is much more extreme and flow separates at the wall. Velocity shear in this separated region provides the
38、 circulation necessary to form a vortex, which is then accelerated and ingested by the engine. The conservation of angular momentum in the accelerating vortex creates very low pressure at the vortex center, and this pressure distortion may cause engine compressor stall to occur. Cell Bypass Ratio (
39、)WFCWENG() WENG= Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:52:03 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR5306 - 6 - FIGURE 1 - Comparison of Bypass Airflow Regions fo
40、r Two Cell Bypass Ratios Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001 Not for Resale, 12/04/2007 19:52:03 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR5306 - 7 - 4.INLET RAMPS: 4.1Description: The inlet r
41、amp system is an engine room installed aerodynamic device that resembles a “picture frame“ as shown in Figure 2. The inlet ramp system is typically mounted to the engine room ceiling on a pair of rails that allows the system to move forward and aft to accommodate various engine model inlet plane loc
42、ations. The lower section of the system is hinged so that it can swing to one side and allow easy equipment access to the test stand and engine. Typical construction for this system would include a mechanical tubing frame with the forward surfaces covered with sheet metal. Corrosion resistant materi
43、als are recommended for low maintenance and an automated positioning feature can be added if the engine models tested require different inlet ramp positions. FIGURE 2 - Test Cell With Inlet Ramps Copyright SAE International Provided by IHS under license with SAELicensee=Defense Supply Ctr/5913977001
44、 Not for Resale, 12/04/2007 19:52:03 MSTNo reproduction or networking permitted without license from IHS -,-,- SAE AIR5306 - 8 - 4.2Application: The inlet ramp system can be a cost effective method to meet higher thrust engine airflow requirements for existing engine test cells. Maintenance shops th
45、at are precluded from testing higher thrust engine models in an existing facility because of airflow limitations can find that the inlet ramp system provides a suitable solution. As is the case with any aerodynamic upgrade under consideration each facility needs to be evaluated individually to deter
46、mine the suitability of the inlet ramp system for a particular application. 4.3Engine Room Requirements: A primary cell design criteria to achieve vortex free airflow is the size of the engine room or test chamber in which the engine is installed. Figure 3 shows square engine room size versus engine
47、 airflow for two cell bypass ratios. Using a front cell velocity of 15.24 m/s (50 ft/s) and the minimum 0.8 cell bypass ratio, engines with takeoff airflow ratings up to 1020 kg/s (2250 lbm/s) will run successfully in an engine room that is 10 m x 10 m. But an engine rated at 1315 kg/s (2900 lbm/s)
48、will require a larger engine room with dimensions of 11.4 m x 11.4 m (point “A“). For an existing facility where this requirement cannot be met, inlet ramps provide a practical option. As indicated by point “B“, inlet ramps will enable operation at a cell bypass ratio as low as 0.4. This will allow an engine rated at 1315 kg/s (2900 lbm/s) airflow to be tested in the original 10 m facility with no additional cell modifications. Thus, the relatively minor addition of inlet ramps make it possible to run engines with about 30% g