1、AEROSPACE RECOMMENDEDPRACTICEARP741REV.BIssued 1961-08Reaffirmed 2008-11Revised 2002-11Superseding ARP741ATurbofan and Turbojet Gas Turbine Engine Test Cell CorrelationTABLE OF CONTENTS1. SCOPE .41.1 General .41.2 Beneficiaries .41.3 Limitations.42. APPLICABLE DOCUMENTS52.1 Definitions .63. FACTORS
2、AFFECTING CORRELATION.74. PERFORMANCE MEASUREMENTS 74.1 General .74.2 Performance Parameters84.3 Instrumentation Calibration .84.3.1 Hierarchy/Secondary Standards .84.3.2 Traceability94.4 Thrust Calibration94.5 Factors Affecting Performance Measurement.94.5.1 Humidity 94.5.2 Engine Inlet Temperature
3、 and Pressure .104.5.3 Fuel Properties 114.5.4 Ram Pressure Ratio124.5.5 Cell Bypass Airflow Interactions124.5.6 Dress Kit Hardware.134.5.7 Data Acquisition 134.6 Software Verification .15SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of techn
4、ical 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 technical report at least every five years at whic
5、h time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2008 SAE International All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical
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7、de feedbackon this Technical Report, please visit http:/www.sae.org/technical/standards/ARP741BCopyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP741 Revision B- 2 -TABLE OF CONTENTS (Continued)5
8、. DESIGNATION OF BASELINE AND REFERENCE FACILITIES .155.1 General .155.2 Identification of a Suitable Reference Facility .155.2.1 Alternative Reference Facilities 165.3 Uncertainty Stack-up.165.3.1 Reducing Uncertainty165.4 Engine Test Hardware Configuration For Reference Testing166. REFERENCE TEST1
9、76.1 General .176.2 Preparation and Engine Running176.2.1 Establishing Appropriate Dialogue176.2.2 Ensuring Test Cell Suitability.176.2.3 Identifying An Acceptable Correlation Engine and Dress Kit Configuration176.2.4 Ensuring Validity of Calibration of Test Cell Instruments.176.2.5 Reference Facili
10、ty Engine Performance Test186.2.6 Shutdown Period.186.2.7 Repeating the Reference Test 196.2.8 Correcting and Analyzing the Correlation Data.196.3 Shipping the Engine to the Customer Facility .197. TEST CELL CORRELATION (CUSTOMER FACILITY)197.1 General .197.2 Preparation and Engine Running207.2.1 Es
11、tablishing Appropriate Dialogue207.2.2 Ensuring Test Cell Suitability.207.2.3 Calibrating the Instrumentation .207.2.4 Precorrelation Procedure 207.2.5 Performing the Correlation Procedure 207.2.6 Shutdown Period.217.2.7 Repeating the Correlation Test .217.2.8 Postcorrelation Procedure 217.3 Correct
12、ing and Analyzing the Correlation Data.227.3.1 Data Validation227.3.2 Performance Shift Determination237.3.3 Correlation Factor Determination238. CORRELATION REPORT 238.1 General .23Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitte
13、d without license from IHS-,-,-SAE ARP741 Revision B- 3 -TABLE OF CONTENTS (Continued)9. MAINTENANCE OF TEST CELL CORRELATION.249.1 General .249.2 Engine and Test Cell Configuration Control 259.3 Correlation Monitoring and Maintenance 259.3.1 Trending259.3.2 Periodic Checks 259.3.3 Recorrelation.269
14、.3.4 Initial Correlatioin Requirements.269.4 Instrumentation Calibration .269.5 Controlling Changes .269.5.1 Record Keeping 269.5.2 Back-to-Back Testing 269.5.3 Total Cell Airflow Monitoring279.6 Test Cell Equipment and Facility Maintenance 2710. NOTES28Copyright SAE International Provided by IHS un
15、der license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP741 Revision B- 4 -1. SCOPE:1.1 General:This paper describes a recommended practice and procedure for the correlation of test cells that are used for the performance testing of turbofan and
16、turbojet engines. Test cell correlation is performed to determine the effect of any given test cell enclosure and equipment on the performance of an engine relative to the baseline performance of that engine. When baseline testing is performed in an indoor test cell, the baseline performance data ar
17、e adjusted to open air conditions. 1.2 Beneficiaries:This recommended practice will benefit the original equipment manufacturer (OEM), commercial users, repair stations and military depots as well as intermediate level maintenance activities. Specific cases in which the information contained herein
18、will be beneficial are: a. As an aid for providing correlation of test cell data between engine and airframe companies supporting commercial and military requirements.b. As an aid for providing military maintenance facilities and commercial repair stations a method by which to correlate test cells.c
19、. As an aid in establishing correlation practices for new test cells, for updating, and maintaining existing test cells.d. As an aid to an engine manufacturers facility in correlation of test cells used for engine development and acceptance in accordance with the applicable engine model specificatio
20、n. 1.3 Limitations:Known methods of determining test cell correlation factors include, but are not limited to, the following:a. Momentum balance (analytical)b. Back-to-backc. Cross-celld. Airflow correlatione. Correlation engine The “correlation engine“ procedure is the recommended and most common m
21、ethod for the correlation of an engine test cell. This paper is limited to the discussion of this one method. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP741 Revision B- 5 -2. APPLICABLE D
22、OCUMENTS:The following is a list of documents used in the preparation of this document: Advisory Group for Aerospace Research and Development (AGARD) 1984. Operation and Performance Measurement on Engines in Sea Level Test Facilities. AGARD-LS-132. Annual Book of ASTM (American Society for Testing M
23、aterials) Standards. 1992. Section 5, Petroleum Products, Lubricants, and Fossil Fuels. Volumes 05.01, 05.02, 05.03. Detroit Diesel Allison (DDA). 1978. Test Stand Correlation. Detroit Diesel Allison Assurance Work Instruction No. 17-217. General Electric. 1982. Airline Planning Guide for Large Turb
24、ofan Test Facilities. General Electric. 1988. Commercial Engine Test Cell Correlation Procedure. General Electric Report No. 8635a. Krengel, J.H. 1981. Air-Breathing Engine Test Facilities Register. AGARD-AG-122. Measurement Uncertainty Handbook (AEDC TR-73-5) Mitchell, J.G. 1988. Comparability Test
25、s in the International Turbine Engine Test Facilities. AIAA-88-3020. (American Institute of Aeronautics and Astronautics) Pratt electrical measurements may be disturbed by noise, or by wiring flaws; liquid flowmeters are affected by turbulence in the liquid. Many such conditions can be detected duri
26、ng calibration, and should be corrected before the final calibration curves are established. 4.3.1 Hierarchy/Secondary Standards: In the United States of America the National Institute of Standards and Technology (NIST) has the primary responsibility for maintaining the standard units of length, mas
27、s, time, temperature, and electrical quantities. Other nations have comparable standards bodies. Instruments used as transfer standards should have calibrations traceable to a national standard. Common practice requires a secondary or transfer standard be at least four times more accurate than the i
28、nstrument being calibrated. With the development of electronic equipment, it is increasingly difficult to achieve this hierarchy of secondary standards. In any case the transfer standard should be substantially more accurate than the working instrument. Copyright SAE International Provided by IHS un
29、der license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP741 Revision B- 9 -4.3.2 Traceability: Traceability establishes the calibration hierarchy for a particular measurement. It identifies all possible error contributions between the test facili
30、ty measurement system and the national standard. Traceability does not reduce the uncertainty of a measurement, it simply documents the process of its determination. Documentation of the instrument and test cell calibrations and hierarchy should be established and maintained. 4.4 Thrust Calibration:
31、The thrust of the engine is usually produced at the engine centerline and transmitted through the mounts to the thrust stand. The thrust stand then pushes against or pulls on a load cell, which measures the reaction force. The force measured by the load cell will rarely equal the engine thrust becau
32、se of: a. The moment caused by the difference in height of the engine thrustline and the load cell locationb. The stiffness of the thrust stand suspension system and engine service connectionsc. The bending of the thrust stand and/or frame A common procedure for measuring these effects is to apply a
33、 known centerline force using a centerline pull rig. The purpose is to generate a calibration curve of the offset between the true centerline force and the measured load cell reaction. Other methods are also used to calibrate the load cell in situ such as an internal calibration device built into th
34、e thrust stand. During engine testing, the true force produced at the engine centerline may be inferred from the load cell measurement and the calibration curve. 4.5 Factors Affecting Performance Measurement:To compare performance parameters between various facilities or various conditions within th
35、e same test facility, it is necessary to correct the parameters to common reference conditions. These reference conditions fall into three groups: a. Ambient (humidity, temperature, and pressure)b. Fuel properties (density, viscosity and lower heating value)c. Aerodynamic (ram pressure ratio and cel
36、l bypass airflow interaction) 4.5.1 Humidity: It is recognized that high humidity levels will affect the performance of gas turbine engines, although no consensus exists on how to account for the effects. Water vapor contained in the air will have several influences on the engine and its performance
37、. Although the consequences are complex, they fall into two major categories: condensation and changes in gas properties. While the relative humidity controls the extent of inlet condensation, it is the absolute or specific humidity which affects the gas properties of the engine cycle, and hence the
38、 performance elements. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP741 Revision B- 10 -4.5.1 (Continued):Actual condensation in an engine inlet depends on a series of factors, such as rela
39、tive humidity, air temperature and pressure, inlet Mach number, and dwell time. At a given humidity, the probability for condensation is higher in long inlet ducts and lower in bellmouth intakes. High inlet Mach numbers can result in inlet condensation at lower relative humidity. For most performanc
40、e parameters, the humidity corrections have been found to be small. However, when evaluating differences between engine or component configurations, these humidity corrections can be important. To minimize humidity effects during correlation, some test facilities and engine manufacturers choose to i
41、mpose humidity limits when testing an engine model.4.5.2 Engine Inlet Temperature and Pressure: Gas turbine engines are affected by the ambient conditions in which they operate. Engine operation and correlation can be affected by inlet temperature distortion or gradient due to exhaust gas recirculat
42、ion or other sources of heat. This gradient should be minimized by modifications to the test cell and engine test configuration. It is usually not possible to control the engine inlet air temperature and pressure to standard day values, therefore to compare one engine run to another, the measured en
43、gine performance parameters must be adjusted to the values which they would have with standard day inlet air. This process is called making standard day corrections. Since the methods for making standard day corrections vary between engine types and models, the procedures to correct these parameters
44、 are contained in the specification, Technical Order, or Engine (Overhaul) Manual for particular engines. Certain primary operating variables of gas turbines are normalized as functions of total temperature and total pressure at the engine inlet. The basic normalizing parameters are: a. (theta) = (o
45、bserved inlet total absolute temperature)/(absolute temperature of I.S.O. sea level standard day reference atmosphere)b. (delta) = (observed inlet total absolute pressure)/(absolute pressure of I.S.O. sea level standard day reference atmosphere) NOTE: These ratios require the use of consistent units
46、 and absolute values i.e., temperatures in Kelvin or degrees Rankine, pressures in psia, in-HgA, or kPa, respectively. Some gas turbine engines are referenced to conditions other than I.S.O. standard day values. Refer to the applicable model specification, Technical Order, or engine manual for perti
47、nent information. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP741 Revision B- 11 -4.5.2 (Continued):The correction or normalizing of the major engine performance parameters requires the us
48、e of and as follows: a. Rotor speed, N, is normalized when divided by x, i.e., N/x, where x is dependent on the engine type and defined by the manufacturer (commonly 0.5 is used).b. Thrust, F, is normalized when divided by , i.e., F/.c. Airflow rate, Wa, is normalized when multiplied by /, i.e, Wa/.
49、d. Fuel flow rate, Wf, is normalized when divided by y, i.e., Wf/y, where y is dependent on the engine type and defined by the manufacturer (typical values of y range from 0.5 to 0.7).e. Engine cycle total temperatures (e.g., T3, T4, T5, T7) are normalized when divided by z, i.e., T5/z, where z is dependent upon the location within
