1、AEROSPACEINFORMATION REPORTAIR5026 REV. BIssued 1996-11Revised 2014-10Superseding AIR5026ATest Cell InstrumentationRATIONALEAIR5026 is being revised ahead of the five-year reaffirmation in order to include recommendations on steady-state data acquisition (3.2). This revision provides guidelines on d
2、ata acquisition minimum sample rate, sample averaging time and the calculation of additional parameters based on steady-state data.TABLE OF CONTENTS1. SCOPE 41.1 General . 41.2 Engine Performance . 41.3 Beneficiaries 42. REFERENCES 42.1 Applicable Documents 42.1.1 SAE Publications. 52.1.2 Other Publ
3、ications. 52.2 Definitions . 53. INSTRUMENT CHARACTERISTICS . 73.1 Analog versus Digital Instruments 73.2 Steady State Measurements. 83.3 Transient Measurements 84. THRUST MEASUREMENT 84.1 General . 84.2 Uncertainty in Thrust Measurement 84.3 Thrust Calibration 95. TORQUE MEASUREMENT 95.1 General .
4、95.2 Shaft Rotary Torque Measurement. 105.3 Reaction Torque Measurement 105.4 Torque Calibration. 106. FUEL FLOW MEASUREMENT 106.1 General . 106.2 Turbine Flowmeters 116.3 Viscosity Effects 116.4 Temperature Effects 11_SAE Technical Standards Board Rules provide that: “This report is published by SA
5、E 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 technical report at
6、least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions.Copyright 2014 SAE InternationalAll rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form
7、 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: +1 724-776-4970 (outside USA)Fax: 724-776-0790Email: CustomerServicesae.orgSAE WEB ADDRESS: http:/www.
8、sae.orgSAE values your input. To provide feedbackon this Technical Report, please visithttp:/www.sae.org/technical/standards/AIR5026B SAE INTERNATIONAL AIR5026B Page 2 of 246.5 Flowmeter Verification. 12 6.6 Fuel Density Measurement . 12 6.7 Vortex Flowmeters 12 6.8 Mass Flowmeters 12 6.8.1 Mass Flo
9、wmeter Installation Effects . 12 6.9 Positive-Displacement Flowmeters. 127. TEMPERATURE MEASUREMENT 127.1 General . 12 7.2 Thermocouples . 13 7.2.1 Thermocouple Extension Wire 13 7.2.2 Reference or Cold Junctions. 13 7.2.3 Paralleling Thermocouple Instruments . 13 7.2.4 Thermocouple Troubleshooting
10、14 7.3 Resistance Temperature Detectors 14 7.3.1 Calibration of Resistance Temperature Detectors 14 7.4 Thermistors . 14 7.4.1 Calibration of Thermistors. 15 7.5 Digital Temperature Scanners 158. ROTOR SPEED MEASUREMENT. 158.1 General . 15 8.2 Frequency-to-Voltage Converters. 15 8.3 Variable Time-Ba
11、se Counters. 15 8.4 Reciprocal Counters 16 8.5 Digital Frequency Counters 16 8.6 Calibrating Rotor Speed Instruments 169. GAS PRESSURE MEASUREMENT. 169.1 General . 16 9.2 Pressure Scanners 16 9.3 Leaks. 17 9.4 Dynamic Pressure Measurements 17 9.5 Obstructions in Pressure Signal Lines 17 9.6 Calibrat
12、ing Gas Pressure Measurements. 1710. LIQUID PRESSURE MEASUREMENT 1810.1 General . 18 10.2 Elevation Effects . 1811. VIBRATION MEASUREMENT 1811.1 General . 18 11.2 Accelerometers . 18 11.3 Velocity Transducers. 18 11.4 Mounting Locations and Brackets. 19 11.5 Vibration Filters . 19 11.6 Vibration Cal
13、ibration and Concerns 1912. AIRFLOW MEASUREMENT. 1912.1 Test Cell Airflow Uniformity. 19 12.2 Engine Airflow . 20 12.3 Bleed Airflow . 20 12.4 Additional Airflow Measuring Systems 20 12.5 Calibration of Airflow Measurements 2013. HUMIDITY MEASUREMENTS . 2013.1 General . 20 13.2 Wet-bulb Dry-bulb Met
14、hods 21 13.3 Relative Humidity and Absolute Humidity Sensors. 21 13.4 Dew Point Sensors 21 13.5 Humidity Instrument Calibration 21SAE INTERNATIONAL AIR5026B Page 3 of 2414. MISCELLANEOUS MEASUREMENTS2115. COMPUTERIZED INSTRUMENTATION SYSTEMS . 2115.1 General . 21 15.2 Data Corrections . 2116. ENGINE
15、S WITH ELECTRONIC FUEL CONTROLS 2216.1 General . 22 16.2 Full Authority Controls. 22 16.3 Partial Authority Controls 2217. TEST FACILITY CONTROL INSTRUMENTATION 2317.1 Programmable Logic Controller 23 17.2 Cell Engine Control Systems 2318. FUTURE TRENDS IN INSTRUMENTATION . 23 18.1 General . 23 18.2
16、 Number of Parameters 23 18.3 Accuracy . 23 18.4 Computer Systems 2419. NOTES 24SAE INTERNATIONAL AIR5026B Page 4 of 241. SCOPE1.1 GeneralThis document discusses, in broad general terms, typical present instrumentation practice for post-overhaul gas turbine engine testing. Production engine testing
17、and engine development work are outside the scope of this document as they will typically use many more channels of instrumentation, and in most cases will have requirements for measurements that are never made in post-overhaul testing, such as fan airflow measurements, or strain measurements on com
18、pressor blades.The specifications for each parameter to be measured, in terms of measurement range and measurement accuracy, are established by the engine manufacturers. Each test cell instrument system should meet or exceed those requirements. Furthermore, each instrument system should be recalibra
19、ted regularly, to ensure that it is still performing correctly.1.2 Engine PerformanceThe basic output of a turbofan or turbojet engine is the thrust produced by the engine. Some industrial gas turbine engines are tested without their power turbines installed, and in consequence are also characterize
20、d by thrust. Other engines use engine pressure ratio, EPR, instead of thrust to determine performance. EPR performance testing requires the use of a standardized air-intake bellmouth and standardized exhaust tailpipe so that the relationship between thrust and EPR is reproducible.Gas turbine engines
21、 which primarily drive output shafts: turboshaft, turboprop, industrial, and marine engines, are characterized by output shaft speed and torque, and therefore output power.A few relatively small turbofan engines deliver enough power to various accessories, such as electrical generators and hydraulic
22、 pumps, so that known loads must be applied to their accessory shafts when the engine thrust is being measured. For most engines, however, the effect of accessory loads is negligibly small, and the accessory shafts need not be loaded. Back-to back correlations between engine manufacturers test facil
23、ities and other test facilities are typically done without any engine accessory pad loading.Many aircraft-type gas turbine engines can furnish substantial amounts of compressed air, called bleed air, taken from one or more stages of the intake air compressor. This compressed air is used to start oth
24、er engines, to drive cabin air conditioning, etc. In ordinary post-overhaul testing the engine performance is measured with no bleed air flowing. Many engines have valves which bleed off controlled amounts of compressed air under certain conditions; that air is simply wasted. Those functions are all
25、owed to proceed normally during post-overhaul testing.Auxiliary power units, APUs, and ground power units, GPUs, deliver most of their output energy in the form of compressed air, and a smaller amount of energy as a shaft drive for an electrical generator. Both the compressed air flow and the genera
26、tor shaft output power must be controlled and measured when testing these engines.1.3 BeneficiariesThe information contained in this document will benefit anyone who is preparing to build and equip a test facility for any type of gas turbine engine, or to contract with a specialist to do such work.2
27、. REFERENCES2.1 Applicable DocumentsThe 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 order. In theevent of conf
28、lict 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.SAE INTERNATIONAL AIR5026B Page 5 of 242.1.1 SAE PublicationsAva
29、ilable from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.(a) ARP741 Turbofan and Turbojet Gas Turbine Engine Test Cell Correlation(b) ARP4755 Turboshaft/Turboprop Gas Turbine Engine Test Cel
30、l Correlation(c) AIR4827 Modeling Techniques for Jet Engine Test Cell Aerodynamics(d) AIR4869 Design Considerations for Enclosed Turbofan/Turbojet Engine Test Cells(e) AIR4951 Test Cell Thrust Measurement(f) AIR4989 Design Considerations for Enclosed Turboshaft Engine Test Cells(g) ARP4990 Turbine F
31、lowmeter Fuel Flow Calculations(h) AIR5295 Design Considerations for Enclosed Turboprop Engine Test Cells(i) ARP5435 APU Gas Turbine Engine Test Cell Correlation(j) ARP5758 Trend Analysis for Maintaining Correlation of Gas Turbine Engine Test Cells(k) ARP6068 Gas Turbine Engine Test Facility Vibrati
32、on Measurement2.1.2 Other Publicationsa. “Measurement Uncertainty: Methods and Applications“, 4th Edition, Dieck, Ronald H.; ISA The International Society of Automation, 2007, ISBN-13: 978-55617-915-0.b. “Report 530, Properties of Aircraft Fuels“, Coordinating Research Council, Atlanta, Georgia, 198
33、3. 2.2 DefinitionsThe following list defines certain terms and phrases used in this document:ACCURACY: This is properly defined as the closeness or agreement between a measured value and the true value, so that a 99% accurate reading has a 1% error. However, almost all vendors of instrumentation hav
34、e adopted the practice of identifying the instrument accuracy by stating its probably inaccuracy, in some form such as r0.5% of full scale value, or r2% of reading over the range from 10 to 50 psig. This paper also follows that practice. Note that it is improper to specify an inaccuracy of a fixed p
35、ercentage of reading without some lower limit; if the range is allowed to go to zero, the allowableerror also goes to zero, an unattainable objective. For those cases in which a more detailed analysis of sources of error (bias error, precision error, etc.) is required, see the full treatment in refe
36、rence document 2.1.2 (a).ALIASING: A phenomenon of sampled signals in which the data is distorted due to an insufficient sampling rate. Nyquists theorem states that a waveform must be sampled at a rate of at least two times its highest frequency component in order to prevent aliasing of the original
37、 waveform. ANALOG: A variable quantity or instrument for measuring it, which varies continuously over some defined operating range. Reading an analog instrument requires the user to observe the position of a pointer moving over a calibrated scale, or the height of a fluid on a scale, etc., in making
38、 the measurement.AUXILIARY POWER UNIT (APU): This is a gas turbine engine, mounted in an aircraft, which is designed to produce compressed air for such functions as cabin air conditioning or starting other engines, and to drive an electrical generator. Some APUs are used only when the aircraft is on
39、 the ground and are shut off when the aircrafts main engines have been started. Others may be used in flight as well.SAE INTERNATIONAL AIR5026B Page 6 of 24BYPASS AIR: In a turbofan engine, air which the engine draws in and does not pass through the engine core. It is compressed slightly and dischar
40、ged together with the core engine exhaust.BYPASS RATIO: In a turbofan engine, the mass flowrate of bypass air divided by the engine core flow mass.COMPRESSOR STALL: A condition in which one or more blades in the engine compressor cannot maintain the pressure differential across them. It is related t
41、o the “stall“ of an aircraft wing; the compressor blades are airfoils, and flow separation produces a stall. If a stall propagates through the whole compressor, violently interrupting the proper functioning of the engine, the event is called a surge.CORE AIRFLOW: Air that a gas turbine engine draws
42、in that passes through the engine core or power section as part of the combustion process.DIGITAL: A variable quantity or instrument for measuring it, which is represented by discrete, usually numerical, values. A typical digital instrument will display a measurement in such a form as 123.14.GROUND
43、POWER UNIT (GPU): This is a gas turbine engine, similar in function to an auxiliary power unit, but which is mounted on a cart or truck and is brought to the aircraft which it is to serve on the ground.INDUSTRIAL ENGINE: This is a turboshaft engine which is designed for nonaircraft applications, suc
44、h as electrical generation, driving petroleum pumps, etc. Industrial engines can be much heavier, and therefore more rugged, than comparable aircraft engines. Some industrial engines are designated as marine engines.K-FACTOR: In a turbine or vortex flowmeter, the number of electrical impulses it del
45、ivers per unit volume of the fluid being measured. It is often treated as approximately constant over some useful range of fluid flow rates.MARINE ENGINE: An industrial engine which is designed for marine service, such as driving a ships propeller.REHEAT ENGINES: Also called afterburning engines, th
46、ese are turbojet or turbofan engines in which additional fuel is injected into the airflow, either bypass air or the exhaust air from the main combustion process, and burned there to raise the air temperature, the airflow volumetric flow rate, and therefore the engine thrust.RESISTANCE TEMPERATURE D
47、ETECTOR (RTD): A temperature-sensing device which consists of an electrical resistor that has a known characteristic of resistance versus temperature. RTDs are made of lengths of wire or thin films of metal deposited on an insulating substrate, and typically have resistances in the order of hundreds
48、 or thousands of ohms. See thermistor.RESOLUTION: The smallest observable increment in the variable being measured by the instrument, usually stated as a fraction of full scale.THERMISTOR: This is an RTD made of a semiconducting material. Thermistors are available with very large, either positive or
49、 negative, temperature coefficients of resistance. Their stability and reproducibility are usually not adequate for accurate temperature measurement, but thermistors are often used in control systems.THERMOCOUPLE: A temperature-sensing device which consists of two conductors of dissimilar electrothermal characteristics. The conductors are joined together at
