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
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5、 Stabilized 2013-12 Superseding AIR5306 Inlet Airflow Ramps for Gas Turbine Engine Test Cells RATIONALEThis document has been determined to contain stable technology which is not dynamic in nature. STABILIZED NOTICE This document has been declared “Stabilized“ by the SAE EG-1E Gas Turbine Test Facil
6、ities and Equipment 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 ResaleNo rep
7、roduction or networking permitted without license from IHS-,-,-TABLE OF CONTENTS1. SCOPE .21.1 Purpose .22. REFERENCES .22.1 Applicable Documents.22.2 Symbols and Abbreviations .32.2.1 Parameters 32.2.2 Abbreviations.32.2.3 Subscripts33. TECHNICAL BACKGROUND.43.1 Cell Bypass Ratio 54. INLET RAMPS74.
8、1 Description.74.2 Application .84.3 Engine Room Requirements84.4 Ejector Tube Requirements.94.5 Model Test Results105. CONCLUSIONS .126. NOTES .126.1 Patent Information .126.2 Key Words .12SAE INTERNATIONAL AIR5306A Page 1 of 12_Copyright SAE International Provided by IHS under license with SAENot
9、for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. SCOPE:This SAE Aerospace Information 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 e
10、xisting engine test facility to meet the airflow requirements for higher thrust engine models. The intellectual 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, Connectic
11、ut, USA. Any individual, or organization, attempting to use the system described in this document should get a clearance from United Technologies Corporation, to avoid any potential liability arising from patent infringement.1.1 Purpose:To provide guidelines for inlet airflow ramps for gas turbine e
12、ngine test cells.2. REFERENCES:2.1 Applicable Documents:The following is a list of some applicable references and documents used in the preparation of this report:2.1.1 Freuler, R.J., Dickman, R.A., Current Techniques for Jet Engine Test Cell Modeling. AIAA-82-1272, Presented at the 18th Joint Propu
13、lsion Conference, June 21-23, 1982, Cleveland, Ohio.2.1.2 De Siervi, F., Viguier, H.C., Greitzer, E.M., Tan, C.S., Mechanisms of Inlet-Vortex Formation, Journal of Fluid Mechanics, 1982, volume 124, pp. 173-207.2.1.3 Glenny, D.E., Pyestock, N.G.T.E., Ingestion of Debris into Intakes by Vortex Action
14、, Ministry of Technology, 1970, Aeronautical Research Council, C.P. no. 1114.2.1.4 Clark, T., Peszko, M., Roberts, 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 E
15、nclosed Turbofan/Turbojet Engine Test Cell“, SAE Aerospace Information Report AIR4869, Society of Automotive 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 Eng
16、ineers, Warrendale, Pennsylvania, Issued May 1993.2.1.7 “Test Cell Instrumentation“, SAE Aerospace Information Report AIR5026, Society of Automotive Engineers, Warrendale, Pennsylvania, Issued November 1996.SAE INTERNATIONAL AIR5306A Page 2 of 12_Copyright SAE International Provided by IHS under lic
17、ense with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-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, 19
18、93.2.2 Symbols and Abbreviations:The following parameters, abbreviations, and subscript notations are used in this report:2.2.1 Parameters:LOSS pressure loss at vortex centerPt total pressureQ dynamic pressure (1/2 V2)V velocityW airflow ratePt pressure difference between inlet Pt and vortex core Pt
19、 cell bypass ratio air density2.2.2 Abbreviations:D inlet diameterFC front cellft feetft/s feet per secondH engine centerline heightkg/s kilograms per secondkN kiloNewtonslbm/s pounds-mass per secondm metersSAE Society of Automotive Engineers2.2.3 Subscripts:BYPASS cell bypass flowENG engineENGINE e
20、ngineFC front cellVORTEX inlet vortexSAE INTERNATIONAL AIR5306A Page 3 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3. TECHNICAL BACKGROUND:Due to the introduction of a new generation of hig
21、h thrust turbofans, 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 decelerati
22、on in airflow causes 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
23、 engine inlet plane 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 co
24、mpressor surge or 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 bypa
25、ss ratio (see 3.1) 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 eng
26、ine room surfaces 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 e
27、ngine test cell 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 t
28、he existing facility. 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
29、 facility operator 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 r
30、elatively minor 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 me
31、et the requirements 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 cel
32、l. With the inlet 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 modificati
33、ons to increase cell airflow.SAE INTERNATIONAL AIR5306A Page 4 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3.1 Cell Bypass Ratio:Cell bypass ratio is defined as the ratio of airflow that pa
34、sses 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 airflow and it is calculated as show
35、n in Equation 1:(Eq. 1)where:WFC= Front cell airflowWENG= Engine airflowCell 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. Bypass ratio as it applies to turbofan e
36、ngine 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. Figure 1 illustrates two cell bypass ratio
37、 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 flow fields for a small and a large engine
38、 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 smaller engine with the 150% cell bypass rati
39、o 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 circulation necessary to form a vortex,
40、 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 () WFCWENG()WENG=SAE INTERNATIONAL AIR5306A
41、 Page 5 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-FIGURE 1 - Comparison of Bypass Airflow Regions for Two Cell Bypass RatiosSAE INTERNATIONAL AIR5306A Page 6 of 12_Copyright SAE Internati
42、onal Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4. INLET RAMPS:4.1 Description:The inlet ramp system is an engine room installed aerodynamic device that resembles a “picture frame“ as shown in Figure 2. The inlet ramp syst
43、em 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 locations. 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
44、 and engine. Typical construction for this system would include a mechanical tubing frame with the forward surfaces covered with sheet metal.Corrosion resistant materials are recommended for low maintenance and an automated positioning feature can be added if the engine models tested require differe
45、nt inlet ramp positions.FIGURE 2 - Test Cell With Inlet RampsSAE INTERNATIONAL AIR5306A Page 7 of 12_Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4.2 Application:The inlet ramp system can be a cos
46、t effective method to meet higher thrust engine airflow requirements for existing engine test cells. Maintenance shops that 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 determine the suitab
