GB/T 20787-2023Reciprocating internal combustion engines—Measurement method for structure-borne noise (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents" Drafting.

This document replaces GB/T 20787-2006 "Reciprocating Internal Combustion Engine Medium and High Speed Reciprocating Internal Combustion Engine Foot Structure Noise Test Regulations" Standard", compared with GB/T 20787-2006, in addition to structural adjustments and editorial changes, the main technical changes are as follows.

a) Changed the "scope" (see Chapter 1, Chapter 1 of the 2006 edition);

b) Changed "Terms and Definitions" (see Chapter 3, Chapter 3 of the 2006 edition);

c) "Symbol" is deleted (see Chapter 4 of the 2006 edition);

d) Added "measurement environment" requirements (see Chapter 4);

e) Added provisions for "measuring instruments" (see Chapter 5);

f) The provisions of "Installation and Working Conditions" have been changed (see Chapter 6, Chapter 6 of the 2006 edition);

g) Changes to the provisions of "acceleration measurement" (see Chapter 7, Chapter 8 ~ Chapter 11 of the 2006 edition);

h) Added provisions for "calculation" (see Chapter 8);

i) Added provisions for "record content" (see Chapter 9);

j) Added "reporting" requirements (see Chapter 10);

k) Added "other connections between the engine and the test environment" (see Appendix A);

l) Added "sensor contact plane height correction" (see Appendix B);

m) The determination of the upper limit frequency in "Determination of Test Frequency Range" has been changed (see Appendix C, Chapter 7 of the 2006 edition).

Introduction

Noise from buildings, structures, ships, aircraft and land vehicles is often caused by the reciprocating internal combustion engines used and can be a major source of noise.

Sound sources, even if they are not the main noise source, can produce background noise. These noises propagate in at least the following two ways.

---Directly entering the surrounding air, that is, air noise. GB/T 1859 specifies the measurement method for airborne noise radiated by internal combustion engines.

---Through excitation or vibration on supporting structures, pipes and shafts, that is, structure-borne noise. These vibrations form structural vibrations as they pass through the structure.

Movement, which in turn excites the surface of the structure, producing so-called secondary sound waves or radiation of structural noise.

The ability of the vibration source (engine) to generate vibration in the supporting structure depends on the amount of movement of the engine at its support, the engine support system and characteristics of load-bearing structures. The vibration of the engine foot may occur in the vertical direction, which is most easily noticeable, or in the longitudinal or transverse direction of the crankshaft;

Vibration sources may also produce rotational inputs to the structure that are resolved along three orthogonal axes.

Once any vibration is generated in a structure, it is difficult to control its propagation in the structure, especially in the low frequency region. Structural vibrations may occur at very Multiple vibration modes (such as compression, torsion or bending) propagate. Only by cutting off the continuity of the structure can the propagation of vibration be completely and effectively controlled.

It is usually difficult to achieve. Structural damping may be effective for certain propagation modes, especially in the high frequency/shortwave region, but not specifically in the low frequency region. Don't be effective.

Although it is difficult to control the propagation of vibration in a structure, it is still necessary to understand the vibration characteristics of the engine as a vibration source.

It is helpful to select a competitive support, or to design the support according to the vibration characteristics of the selected engine.

1 Scope

This document describes methods for measuring structure-borne noise in reciprocating internal combustion engines.

This document applies to reciprocating internal combustion engines defined in GB/T 21404 (hereinafter referred to as "engine" unless otherwise specified).

2 Normative reference documents

The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, the dated quotations For undated referenced documents, only the version corresponding to that date applies to this document; for undated referenced documents, the latest version (including all amendments) applies to this document.

GB/T 1859.1 Determination of sound power level of reciprocating internal combustion engines by sound pressure method - Part 1: Engineering method

GB/T 1859.3 Determination of sound power level of reciprocating internal combustion engines by sound pressure method - Part 3: Semi-anechoic chamber precision method

GB/T 6072.1 Reciprocating internal combustion engine performance Part 1: Calibration and test methods for power, fuel consumption and oil consumption Additional requirements for general purpose engines

GB/T 6072.3 Reciprocating internal combustion engine performance Part 3: Test measurements

GB/T 13824 Requirements for vibration intensity measuring instruments due to mechanical vibration of rotating and reciprocating machines

GB/T 14777 Geometric orientation and direction of motion

3 Terms and definitions

The following terms and definitions as defined in GB/T 6072.1, GB/T 13824 and GB/T 14777 apply to this document.