ANSI ASME PTC 19.7-1980 Part 7 Measurement of Shaft Power Instruments and Apparatus.pdf
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1、 PART 7 Measurement of Shaft Power . - - d ,. “r: . ,.- L ASME PTC*197 80 II 0759670 0052723 T II PART 7 MeasureMent of Shaft Power ANSI I ASME PTC 19.7-1980 INSTRUMENTS AND APPARATUS THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS United Engineering Center 345 East 47th Street Ne“ York, N.Y. 10017 ASM
2、E PTC*19-7 80 0759670 0052724 1 No part of this document may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher Date of Issuance: August 31, 1980 Copyright 1980 THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reser
3、ved Printed in U.S.A. ASME PTC*19.7 80 II 0759670 0052725 3 II FOREWORD The Performance Test Codes Supervisory Committee in December 1974 activated a Committee to revise PTC 19.7 (1961) on Measurement of Shaft Powe. This Instruments and Apparatus Technical Committee has prepared an Instruments and A
4、pparatus Supplement which incorporates the latest technology on the Measurement of Shaft Power. The Scope of the work of PTC 19.7 on Measurement of Shaft Power is limited to descriptive material which will enable the user to select an appropriate system or procedure for his applica tion. It includes
5、 criteria for the operating conditions of the equipment whose power is being measured. The Object of this Supplement is to describe the function, characteristics, advan tages, disadvantages and accuracy of equipment and techniques currently available for the measurement of shaft power in rotating ma
6、chines. Only the methods of measurement and instruments, including instructions for their use, specified in the individual test codes are mandatory. Other methods of measurement and instru ments, that may be treated in the Supplements on Instruments and Apparatus, shall not be used . unless agreeabl
7、e to all the parties to the test . This Supplement was approved by the Performance Test Codes Supervisory Committee on july 2, 1979. It was approved and adopted by the American National Standards Institute as meeting the criteria for an American National Standard on April 28, 1980 . iii 0 ASME PTC*1
8、9.7 80 II 0759670 0052726 5 II PERSONNEL OF ASME PERFORMANCE TEST CODES COMMITTEE NO. 19.7 ON INSTRUMENTS AND APPARATUS MEASUREMENTOFSHAFTPOWER Hunt Davis, Chairman and Secretary Robert R. Piepho, Vice Chairman Arthur L. Beaman, Jr., Fellow Design Engineer, Medium Motor and Gearing Division, Westing
9、 house Electric Corp., P.O. Box: 225, Buffalo, New York 14240 Robert Clelland, Senior Principal Engineer, Rotating Equipment Section, Pullman Kellogg Divi sion, Pullman, Inc., Three Greenway Plaza East, Houston, Texas 77046 Hunt Davis, Senior Staff Engineer, Pullman Kellogg Division, Pullman, Inc.,
10、Three Greenway Plaza East, Houston, Texas 77046 Ralph jaeschke, Chief Engineer, Eaton Corp., Industrial Drives Division, 3122 14th Avenue, Kenosha, Wisconsin 53141 -Donald R. Jenkins, Associate Professor, Mechanical Engineering Department, Lafayette College, Easton, Pennsylvania 18042 Irving I. Kahn
11、, President, Kahn Industries Inc., 885 Wells Road, Wethersfield, Connecticut 06109 Douglas C. Falkner, Senior Test Engineer, Cameron TestDepartment, Ingersoll Rand Co., Phil lipsburg, New Jersey 08865 Richard A. Mayer, Senior Consultant, Applied Physics Division, Southwest Research Institute, 6220 C
12、ulebra Road, San Antonio, Texas 78284 Daniel Nobles, Research Engineer,Worthington Pump International, Harrison, New Jersey 07029 Robert R. Piepho, Product Manager, Fuel Preparation Systems, Fossil Power Generation Divi sion, Babcock that is, there are no transients in either torque or angular veloc
13、ity within the time interval required tomake the measurement. 2.02 The measurement of shaft power of rotating rna“ chines in the absence of transients, is accomplished by either direct or indirect methods, The direct methods, utilizing a dynamometer or a torque meter, involve deter mination of the v
14、ariables in the following equation: Physical equation P=wT where P = power w =angular velocity T= torque Power expressed in Sf units P=wT where P =power, watts (W) w =angular velocity, rad/s T torque, newton meters (Nm) Power expressed in English units P = 21rnT 550 where P =power, horsepower (hp n
15、=rotational speed, revolutions/sec (r/s) T= torque (lbfft 2.03 There are cases in which transients in angular velocity and torque occur. Some of the apparatus described herein may, under certain circumstances, be capable of making measurements of instantaneous power, when angular velocity and torque
16、 vary with time; or measurements of 3 average power when angular velocity and torque vary cyclically. 2.04 For these cases of non-steady angular velocity and torque the instantaneous value of power is, in physical terms, P=w T Torque meter systems with appropriate data recording systems may be used
17、to determine the value of Tat any instant. A similar recording of angular velocities, w, then provides a basis for determination of the instantaneous value of P. If the values of T and w vary cyclically the average power may be determined as follows. Let the period of one cycle of torque and speed b
18、e the time b., and the ro tational travel for one cycle be the angle (), in radians. Also let !f be defined as !f = fo E 1-L-,-RANDOM ERROR DISTRIBUTION TEMPERATURE, T FIG. 1 SYSTEMATIC AND RANDOM ERRORS ILLUSTRATED FOR CASE OF A THERMOCOUPLE CALIBRATION (Ref. 1) confidence interval statement is giv
19、en by power= 386 6 kW; (95%) where 386 kW is the estimated value, based on averaging a number of measurements, 6 kW is the confidence interval; and the probability of the true value ofpower being in the range 38.5 to 392 kW is 95%. For a given set of observa: tions, as the confidence interval is mad
20、e larger, the prob ability becomes greater. 2.09 Measurements of shaft power involve determination of multiple physical quantities. The complexity of the ap plication of the foregoing statistical concepts, and the pro cedures of References 1 and 2, Appendix D, varies greatly depending on the method
21、and apparatus to be used. 2.10 The contribution of systematic errors is minimized by careful calibration of individual components. The con tribution of random errors is minimized by increasing the number of readings of output for fixed values of the con trolled operating parameters. 2.11 The term pr
22、obable error refers to the confidence inter val around the estimated value for which the probability is 500;0. 2.12 In the succeeding parts of this Supplement, numerical values are assigned to the “errors“ or “overall errors“ of the various systems. Each of these is to be considered as the probable
23、error of a single determination, having a 50% probability that the given range includes the real value. These overall errors are usually dominated by random sources because the procedures require calibrations be ASME PTC*19.7 80 II 0759670 0052734 4 II ANSI/ASME PTC 19.7-1980 SECTION 2 _, X x x POOR
24、 PRECISION -POOR ACCURACY POOR PRECISION GOOD ACCURACY x x BIAS GOOD PRECISION POOR ACCURACY GOOD PRECISION -GOOD ACCURACY FIG. 2. ACCURACY AND PRECISION (Ref. 1) performed where appropriate. The nature of the systems which are subject to calibration is such that the confidence interval (500) of the
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