This standard specifies the measurement and evaluation method of torsional vibration of crankshafts driven by reciprocating piston-connecting rod mechanisms. This standard is applicable to crankshafts of internal combustion engines with three or more cylinders per row, and can also be used as a reference for crankshafts of internal combustion engines with less than three cylinders and piston compressors. GB/T 15371-1994 Measurement and evaluation method of torsional vibration of crankshafts GB/T15371-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Torsional vibration of crankshaft systems-Measurement and evaluation method 1 Subject content and scope of application
GB/T 15371-94
This standard specifies the measurement and evaluation method for torsional vibration of crankshaft systems driven by reciprocating piston-connecting rod mechanisms. This standard is applicable to crankshaft systems of internal combustion engines with three cylinders or more in each row. It can also be used as a reference for crankshaft systems of internal combustion engines with less than three cylinders and piston compressors.
2 Reference standards
GB6299 Measurement method for torsional vibration of marine diesel engine shaft system GB/T13436 Technical requirements for torsional vibration measuring instruments GB3325 Classification of torsional vibration of marine diesel engine shaft system ZBJ91005 Limits and measurement methods for torsional vibration of internal combustion generator shaft system 3 Terminology
3.1 Crankshaft system Crankshaft system refers to the assembly of crankshaft connecting rod mechanism, transmission connecting parts and powered components related to torsional vibration calculation. 3.2 Simple harmonic order The number of waves of a sine wave per revolution of a rotating shaft. 3.3 Relative amplitude The ratio of the amplitude of a point in the shaft system to the amplitude of a reference point. 4
Method for measuring torsional vibration
4.1 Measurement parameters
Taking the rotation center of the shaft system as a reference, the angular displacement amplitude of the measured point is taken as the measurement parameter, and the measurement unit is expressed in degrees (°) or radians (rad). 4.2 Measuring instruments
4.2.1 The measuring instruments shall comply with the provisions of GB/T13436. 4.2.2 The instrument measurement frequency range shall be selected in the flat part of the instrument amplitude-frequency characteristic curve. The allowable error in this frequency range shall be within ±10% of the indicated value. If the low-frequency response of the instrument is insufficient, the torsional vibration measurement value shall be corrected according to the actual frequency response characteristics of the instrument. 4.3 Measurement point location
4.3.1 The measurement point shall be arranged at the position where the torsional vibration amplitude of the crankshaft system is large, generally selected at the free end of the crankshaft of the internal combustion engine or compressor. 4.3.2 The crankshaft system that needs to be measured at multiple points shall be set at the position with large torsional vibration amplitude and other positions that need to be measured based on the results of pre-calculation.
4.3.3 For internal combustion generator sets and motor compressor sets, additional measurement points may be added near the motor shaft extension end if necessary. 4.3.4 For the internal combustion engine bench test shaft system, additional measurement points may be added at the dynamometer end if necessary. Approved by the State Administration of Technical Supervision on 7994-12-27 and implemented on 1995-07-01bzxZ.net
4.4 Measurement conditions
GB/T15371---94
4.4.1 For units working with variable speed and load, the measurement shall be carried out in the range from the lowest stable speed to the highest speed; if necessary, the torsional vibration measurement can be carried out under the continuous change of speed increase and decrease. 4.4.2 The speed measurement interval is generally 5% of the rated speed, which can be increased to 2% of the rated speed in the resonance area. 4.4.3 The shaft system of the internal combustion engine bench test is generally carried out according to the external characteristics or propeller propulsion characteristics (for marine main engines) or traction characteristics (for locomotive diesel engines).
4.4.4 The shaft system of the internal combustion generator set shall be measured for torsional vibration at the rated speed, rated voltage and rated load. 4.4.5 If the torsional vibration measurement is required under special conditions, it shall be stated in the technical documents. 4.5 Measurement Procedure
4.5.1 Install the sensor at the selected measuring point according to the requirements of G13/T13436 and correctly connect the instrument test system. 4.5.2 For belt-driven mechanical torsional vibration meters, the belt should be properly tensioned. For electronic torsional vibration meters, the wire should be well fixed. The influence of environmental factors such as temperature and magnetic field on the measurement accuracy should be eliminated as much as possible to ensure the normal measurement. 4.5.3 Under the selected measurement conditions, the unit speed should be stabilized before measurement. Sufficient measurement recording time should be ensured for each gear measurement. 4.5.4 It is allowed to use filters when measuring piles, but they must be selected correctly and explained in the report. 4.6 Analysis of Measurement Results
4.6.1 Through the analysis of the crankshaft shaft system torsional vibration measurement waveform, the actual speed, shaft system natural frequency, critical speed, simple harmonic number and measuring point amplitude value can be directly obtained.
4.6.2 According to the measurement recording method, torsional vibration signal characteristics and analysis equipment conditions, the torsional vibration wave analysis method should be reasonably selected. 4.6.2.1 When using the manual analysis method, more than three typical periodic waveforms should be selected and the arithmetic mean of their amplitudes should be taken. 4.6.2.2 When using the analog analysis method, the analysis instrument system should meet the requirements of the recording signal frequency range, select a filter with a suitable bandwidth, and ensure the analysis accuracy.
4.6.2.3 When using the digital analysis method, the resolution, sample length, etc. must be comprehensively considered to ensure the analysis accuracy. 4.6.3 The above measurement and analysis results are plotted into a curve or table showing the amplitude A of each main subharmonic at the measurement point and the change with the speed m. 5 Torsional vibration evaluation method
5.1 Evaluation parameters
5.1.1 The evaluation parameters of the crankshaft torsional vibration are torsional stress, vibration torque and torsional amplitude, which are generally evaluated according to torsional stress or vibration torque.
5.1.2 If the error between the measured natural frequency value of the shaft system and the theoretical calculated value is within the range of ±5%, the measured amplitude of the measuring point can be used to infer the amplitude, stress and vibration torsion of each part of the shaft system within the speed range of the resonance zone according to the corresponding natural vibration mode calculated by the free vibration theory. Otherwise, the theoretical calculation should be corrected before inferring. 5.1.3 The vibration torque of the shaft section in the shaft system is calculated according to formula (1): M,++ A(a: - ai+t)Ksi+1
Where: M,+1 The vibration torque of the shaft section between the i-th and i+1 masses, N·m; A,---The maximum subharmonic amplitude value of the measuring point (generally the first mass), Iad; a:--The relative amplitude of the corresponding natural vibration mode of the i+1 mass; ai-The relative amplitude of the corresponding natural vibration mode of the i+1 mass; K.i+}The torsional stiffness of the shaft section between the ii+1 masses, N·m/rad. 5.1.4 The torsional stress of the shaft section in the shaft system is calculated according to formula (2): Miiti
Wherein: t-the torsional stress of the shaft section between the i-th and +1 masses. PaW.11——the torsional section modulus of the shaft section between the i-th and i-1 masses, for the crankshaft, the crankpin diameter shall prevail, for the transmission shaft, the minimum true diameter of the shaft shall prevail, mm.
GB/T 15371--94
5.1.5 Compare the vibration torque and torsional stress of the shaft section obtained according to 5.1.3 and 5.1.4 with the corresponding allowable load to evaluate the stability of the shaft system.
5.2 Allowable values
5.2.1 Allowable torsional vibration stress
5.2.1.1 For crankshaft systems with variable speed operation, the torsional vibration stress of the shaft section shall not exceed the allowable torsional vibration stress value: continuous operation
momentary operation
overspeed operation
1 - Y s 1. 15
Ero)
5.2.1.2 For crankshaft systems with constant speed operation, such as internal combustion generator sets, the torsional vibration stress of the shaft section shall not exceed the torsional vibration stress value: continuous operation
momentary operation
武(3)(4)申:
Ratio of resonant speed to rated speed:
tContinuous operation shaft section torsional vibration stress, Pa;
.t.! Allowable torsional vibration stress for continuous operation, Pa; t…Instantaneous operation shaft section torsional vibration stress, Pa; [t-Instantaneous operation shaft section torsional vibration stress, Pa; Overspeed operation shaft section torsional vibration stress, Pa;
Overspeed operation torsional vibration allowable stress, Pa.
0. 95 7 1. 1
0 ≤ Y ≤ 0. 95
..46...
5.2.1.3 The allowable torsional vibration stress depends on the purpose of the unit (such as cabin, automobile, tractor, etc.), the type of the shaft in the shaft system (such as shaft, transmission shaft, etc.) and the selected material.
5.2.2 Allowable vibration torque
5.2.2.1 If a gear transmission device is installed in the shaft system, the vibration torque at the gear meshing point shall not exceed the transmission torque between the gear pairs. The maximum torque transmitted by the gear transmission device shall not exceed its allowable torque. 5.2.2.2 If an elastic coupling is installed in the shaft system, the vibration torque transmitted by its elastic element during continuous operation shall not exceed the allowable alternating torque value for continuous operation specified by the elastic coupling manufacturer; during instantaneous operation, it shall not exceed the allowable alternating torque value for instantaneous operation. 5.2.3 Allowable amplitude of torsional vibration
5.2.3.1 When insufficient data is available to obtain the torsional vibration stress and vibration moment of the shaft section, the torsional vibration amplitude value may be used for evaluation. 5.2.3.2 For the crankshaft system of internal combustion engine and compressor, the maximum subharmonic amplitude measured at the free end of the crankshaft shall be the evaluation value. For the shaft system that cannot be measured at the free end of the crankshaft, the maximum subharmonic amplitude measured at the position with relatively large amplitude shall be the evaluation value. 5.2.3.3 The allowable amplitude of torsional vibration shall depend on the purpose of the machine and the material selected for the shaft system. 5.2.3.4 The torsional vibration amplitude (including pulsation amplitude) of the alternator of the internal combustion generator set shall not exceed 2.5\/P, where 1》 is the number of magnetic pole pairs of the generator.
6 Torsional vibration speed restricted zone
6.1 If the torsional vibration stress or vibration torque or torsional vibration amplitude of the crankshaft system exceeds the allowable value for continuous operation specified in the corresponding standard, a "speed restricted zone" shall be set near the resonant speed n. In this restricted zone, the unit shall not operate continuously. 6.2 The speed range to be avoided is as follows:
(18 — )me
6.3 The speed forbidden zone can also be taken as the speed range beyond the allowable value for continuous operation, which is determined by measurement and takes into account the speed measurement error of ± 2%.
GB/T15371—94
Additional Notes:
This standard is proposed by the Ministry of Machinery Industry of the People's Republic of China and is under the jurisdiction of the National Technical Committee for Standardization of Internal Combustion Engines. This standard was drafted by the Shanghai Internal Combustion Engine Research Institute of the Ministry of Machinery Industry. The main drafters of this standard are Wu Yanting, Wu Qi and Zhou Yuekang. 514
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