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
2、from, 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 invites your written comments and suggestions. Copyright 2010 SAE International All rights reserved. No part of this publication m
3、ay be reproduced, stored in a retrieval system or transmitted, in any 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: +1 724-776-4970 (outside U
4、SA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedbackon this Technical Report, please visit http:/www.sae.org/technical/standards/J2881_201006SURFACEVEHICLERECOMMENDEDPRACTICEJ2881 JUN2010 Issued 2010-06 Measurement of Aerody
5、namic Performance for Mass-Produced Cars and Light-Duty Trucks RATIONALE It is the intent of the Road Vehicle Aerodynamics Forum Committee to arrive at an aerodynamic certification standard for passenger vehicles that achieves the following objectives: 1. It documents the aerodynamic performance alo
6、ng with the associated vehicle set-up and full-scale wind tunnel conditions employed for the measurement. 2. It defines a process to make appropriate corrections to the wind tunnel results depending on the specific wind tunnel used. 3. It ensures uniformity and transparency by making the test result
7、s publicly available for use by customers, researchers, and media who may have an interest in the vehicles documented aerodynamic performance. The current revision of this recommended practice achieves the first of these objectives, with the intent of achieving the next two in a subsequent revision
8、as soon as practical. SAE J2881 Issued JUN2010 Page 2 of 19TABLE OF CONTENTS 1. SCOPE 32. REFERENCES 33. VEHICLE LOADING, ATTITUDE, AND CONTENT 43.1 Vehicle Loading . 43.2 Vehicle Attitude . 43.3 Vehicle Content . 54. INSTALLATION AND TESTING CONFIGURATION 54.1 Yaw Angle . 54.2 Tire Pressure . 54.3
9、Fluid Levels . 54.4 Fuel Level 54.5 License Plates . 54.6 Cooling Fans . 54.7 HVAC Controls, Cooling Inlets, Windows, and Vents . 54.8 Windshield Wipers 54.9 Antennas . 54.10 Outside Mirrors 64.11 Vehicle-Specific Configurations 64.12 Active Devices . 64.13 Test Speed 64.14 Photographic Requirements
10、 . 65. WIND TUNNEL TESTING AND DATA PROCESSING 65.1 General . 65.2 Wind Tunnel Information . 65.3 Data Processing 85.3.1 Data Corrections . 85.3.2 Other Data Corrections . 86. REPORTING . 97. SUBMITTAL PROCEDURE 98. NOTES 98.1 Marginal Indicia . 9APPENDIX A ACKNOWLEDGEMENTS . 10APPENDIX B VEHICLE IN
11、FORMATION SHEET WITH ATTACHMENTS . 11APPENDIX C WIND TUNNEL INFORMATION SHEET 15APPENDIX D SAMPLE SUBMITTAL 17SAE J2881 Issued JUN2010 Page 3 of 191. SCOPE This recommended practice provides a procedure for measuring and documenting the aerodynamic performance in a full-scale wind tunnel of passenge
12、r vehicles, i.e., mass-produced cars and light-duty trucks intended primarily for individual consumers. Testing or numerical modeling of pre-production and/or reduced-scale models is outside the scope of this document. Aerodynamic development procedures, i.e., methods to improve or optimize aerodyna
13、mic performance, are also excluded. It is well-known that aerodynamic performance results depend significantly on vehicle content and loading, as well as the wind tunnel itself (type, scale, and simulation qualities of the wind tunnel). Publication of non-standard test results causesunnecessary addi
14、tional development work and incorrect perception of a vehicles anticipated aerodynamic performance by government, academia, and the general public. The intent of this document is to promote uniformity and traceability of published aerodynamic performance data acquired in a wind tunnel, thereby enhan
15、cing the public reputation and credibility of the aerodynamics discipline in the total vehicle development process. Measurement of the aerodynamic performance according to this recommended practice requires a full-scale wind tunnel test on a production-ready, full-scale vehicle according to specific
16、ations for vehicle loading, content, and wind tunnel conditions.The measurement and resulting documentation for a particular vehicle shall be reported only by the company that intends to produce the vehicle. Whenever there is an opportunity for interpretation of the document, a good faith effort sha
17、ll be made to obtain the vehicles typical in-service performance and avoid finding the best possible performance under the best possible circumstances. Use of and compliance with this recommended practice is voluntary; however, it is mandatory for those advertising or otherwise publishing aerodynami
18、c performance as “measured according to SAE J2881”. Conversely, any advertised or otherwise published result carrying this or a substantially similar designation must have the necessary documentation accepted by and on file with the SAE in accordance with the procedures defined in this recommended p
19、ractice. Appendices B and C contain the necessary submittal documents for compliance with this recommended practice. When a submittal is made, the chairman of the Road Vehicle Aerodynamics Committee (or his/her designee) shall review the submittal for proper completion according to the requirements
20、herein, but without consideration of the technical merit of the claimed performance. After the chairmans review, SAE will maintain an electronic database of all submittals.The database shall be available only to members of the Road Vehicle Aerodynamics Committee. Any RVAC member who retrieves inform
21、ation from the database shall do so with the understanding that the information is to be considered confidential within his or her company. 2. REFERENCES 2.1 SAE Standard J1594, “Vehicle Aerodynamics Terminology,” December, 1994. 2.2 SAE Recommended Practice J2263, “Road Load Measurement Using Onboa
22、rd Anemometry and Coastdown Techniques,” October, 1996. 2.3 SAE Recommended Practice J1263, “Road Load Measurement and Dynamometer Simulation Using Coastdown Techniques,” February, 1996. 2.4 Iwase, H., Yamada, S., and Koga, H., “A New Approach to Measuring Road Load by Chassis Dynamometer and Wind T
23、unnel Tests,” SAE Paper 820377. 2.5 Eaker, G.W., “Wind Tunnel-to-Road Aerodynamic Drag Correlation,” SAE Paper 880250. SAE J2881 Issued JUN2010 Page 4 of 192.6 Le Good, G.M., Howell, J.P., Passmore, M.A., and Cogotti, A., “A Comparison of On-Road Aerodynamic Drag Measurements Compared with Wind Tunn
24、el Data from Pininfarina and MIRA,” SAE Paper 980394. 2.7 Walter, J.A., Pruess, D.J., and Romberg, G.F., “Coastdown/Wind Tunnel Drag Correlation and Uncertainty Analysis,” SAE Paper No. 2001-01-0630. 2.8 Cooper, K. (ed.), “Closed-Test-Section Wind Tunnel Corrections for Road Vehicles,” SAE SP 1176,
25、1996. 2.9 SAE Information Report J2084, “Aerodynamic Testing of Road VehiclesTesting Methods and Procedures,” January, 1993. 2.10 Lindener, N. (ed.), “Aerodynamic Testing of Road Vehicles in Open Jet Wind Tunnels, SAE SP 1465, 1999. N.B. contains useful technical information, but specific correction
26、 methods are superseded by the references that follow. 2.11 Mercker, E., and Wiedemann, J., “On the Correction of Interferences Effects in Open Jet Wind Tunnels,” SAE Paper No. 960671. 2.12 Mercker, E., Wickern, G., and Wiedemann, J., “Contemplation of Nozzle Blockage in Open Jet Wind-Tunnels in Vie
27、w of Different Q Determination Techniques,”SAE Paper No. 970136. 2.13 Wickern, G., “On the Application of Classical Wind tunnel Corrections for Automotive Bodies,” SAE Paper No. 2001-01-0633. 2.14 Nijhof, B., and Wickern, G., “Reference Static and Dynamic Pressures in Automotive Wind Tunnels,” SAE P
28、aper No. 2003-01-0428. 2.15 Wiedemann, J., Fischer, O., and Jiabin, P., “Further Investigations on Gradient Effects,” SAE Paper No. 2004-01-0670. 2.16 Wickern, G., and Schwartekopp, B., “Correction of Nozzle Gradient Effects in Open Jet Wind Tunnels,” SAE Paper No. 2004-01-0669. 2.17 Mercker, E., Co
29、oper, K.R., Fischer, O., and Wiedemann, J., “The Influence of a Horizontal Pressure Distribution on Aerodynamic Drag in Open and Closed Wind Tunnels,” SAE Paper No. 2005-01-0867. 2.18 Mercker, E., and Cooper, K.R., “A Two-Measurement Correction for the Effects of a Pressure Gradient on Automotive, O
30、pen-Jet, Wind Tunnel Measurements,” SAE Paper No. 2006-01-0568. 2.19 Wickern, G., “Recent Literature on Wind Tunnel Test Section Interference Related to Ground Vehicle Testing,” SAE Paper No. 2007-01-1050. 3. VEHICLE LOADING, ATTITUDE, AND CONTENT 3.1 Vehicle Loading The vehicle shall be loaded acco
31、rding to the vehicle loading chart provided in Appendix B, Attachment 1. As an alternative to this loading chart, it is acceptable to load only the front two seats, each with 70 kg. 3.2 Vehicle Attitude The vehicles attitude shall be documented by measuring the height from the wind tunnel floor to t
32、he edge of the wheel opening arch above each wheel centerline. The vehicle shall be tested at the manufacturers intended nominal attitude corresponding to the loading requirements specified above, not at a lower attitude resulting from the inclusion of build tolerances, etc. If this information is n
33、ot available, the vehicle may be loaded as above and tested at the resulting attitude,which shall be documented. SAE J2881 Issued JUN2010 Page 5 of 193.3 Vehicle Content The intent of this recommended practice is to promote uniformity and traceability of published aerodynamic performance data. To th
34、at end, the vehicle being tested shall in general represent a nominal variation of the model rather than extremes which will not be produced or which may be produced in small numbers.Special optional content packages (e.g., “Sport Package”) may be submitted, provided that the nature and detail of th
35、e content are specified on the form. Absent such a specific disclosure, however, the vehicle tested shall contain the optional content nominally corresponding to the highest sales volume anticipated for that model. Prior to the test, a good faith effort shall be made to determine optional content co
36、rresponding to the highest sales volume. The vehicle information sheet (Appendix B) contains entries to indicate the presence of some common options that influence aerodynamic performance. In addition to these items, indicate in the space provided all other optional content on the vehicle that may i
37、nfluence aerodynamic performance. 4. INSTALLATION AND TESTING CONFIGURATION This section defines configuration requirements for the vehicle installation and testing in the wind tunnel. 4.1 Yaw Angle The vehicle shall be set at 0 0.1 deg yaw angle with the front wheels centered (zero steer angle) wit
38、h adjustment applied as required to account for empty-tunnel yaw of the oncoming flow. 4.2 Tire Pressure Set tire pressures to manufacturers specification(s) 4.3 Fluid Levels Set fluid levels (engine oil, coolant, transmission fluid, etc.) at nominal fill. 4.4 Fuel Level The fuel tank shall be full
39、as defined by the manufacturers specifications. 4.5 License Plates Note whether the vehicle was equipped with a front number/license plate during the test. 4.6 Cooling Fans Electric fans shall have no power applied so that they are allowed to rotate freely. Lock the clutch on engine-driven fans. 4.7
40、 HVAC Controls, Cooling Inlets, Windows, and Vents Turn HVAC control off and (if possible) to re-circulation mode. Open all cooling inlets and grilles. Fully close all windows and vents. 4.8 Windshield Wipers Set windshield wipers to the parked position. 4.9 Antennas Fully retract the antenna if pos
41、sible. Fixed antennas shall remain installed on the vehicle. SAE J2881 Issued JUN2010 Page 6 of 194.10 Outside Mirrors Set outside mirrors to the nominal viewing position. 4.11 Vehicle-Specific Configurations Convertibles and vehicles with retractable hard tops shall be in the up condition with side
42、 windows closed. Sunroofs shall be in the closed condition. Pickup truck tailgates shall be in the up position. 4.12 Active Devices Active and variable-geometry devices, such as ride height adjustment, automated cooling intakes, or automated spoilers, shall be adjusted to their as-designed operating
43、 condition for the test speed selected. If required for the subsystem in question, the operating conditions shall be set for 20 C, 50% relative humidity, and 95 kPa barometric pressure, regardless of actual ambient conditions during the wind tunnel test. Indicate on the vehicle information sheet how
44、 each such device was set up during the test. 4.13 Test Speed Airspeed setting for the test shall be between 110 km/h and 140 km/h or equivalent dynamic pressure. 4.14 Photographic Requirements A photograph of the specific vehicle whose test results are being reported shall be provided on the vehicl
45、e information sheet. The photograph shall be of the vehicle installed in the wind tunnel. The general direction shall be from the side but oriented downstream, to provide a full perspective view of the vehicle. 5. WIND TUNNEL TESTING AND DATA PROCESSING 5.1 General The wind tunnel used may have a si
46、gnificant influence on the reported aerodynamic performance. As partial mitigation of tunnel-specific influence, measurement and reporting according to this recommended practice requires documentation of the wind tunnel test section geometry used, as well as other salient performance parameters, veh
47、icle installation details, and data processing methods. In the absence of specific tunnel-to-tunnel correlations, detailed information about the wind tunnel allows users of the reported data to assess how the aerodynamic performance might differ in a wind tunnel other than the one used for reporting
48、, due, for example to different ground plane conditions, different nozzle sizes, or different empty-tunnel static pressure gradients. In addition, the wind tunnel information can be used in conjunction with the vehicle information to apply interference corrections (see Section 2.0 for references) if
49、 none was applied to the reported data. 5.2 Wind Tunnel Information 5.2.1 The wind tunnel information specified in this section shall be provided on the wind tunnel information sheet (Appendix C). 5.2.2 Name and Location Specify the name and location of the wind tunnel used to document the vehicles aerodynamic performance according to this recommended practice. SAE J2881 Issued JUN2010 Page 7 of 195.2.3 General LayoutDime
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