RU2627167C1 - Method for estimating noise radiated by gas exhaust system, vehicle in motion - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: noise measurement set of vehicle moving along the measured section in the acceleration mode is carried out, with registration of the obtained values by memory device, including the engine crankshaft speed value and noise levels, and as a result, value dependencies of the total noise levels and engine crankshaft speed on the position at the measured section are obtained. A measurement set of the gas dynamic exhaust noise and structural noise of mufflers is carried out on the bench with chassis dynamometers in the engine crankshaft speed range from the value corresponding to the idle speed to the value corresponding to the nominal rotation speed, and allowances for correcting the structural noise of the mufflers are determined. Levels of structural noise are plotted on the diagram with the values of the external noise levels of the vehicle by correlating the engine crankshaft speed during bench and road tests, taking into account the correction for the distance, determining the value dependence of the measured noise level on the distance between the noise source and the recording microphone. The noise level diagrams are obtained, which contain both general noise levels and 1/3 octave spectra.

EFFECT: improved measurement accuracy.

5 dwg

Description

The invention relates to the field of acoustics of motor vehicles (hereinafter ATS), in particular, to methods for measuring external noise of ATS, and can be used to identify noise produced by the exhaust system (hereinafter referred to as ATS) and to determine its contribution to the total noise level of ATS .

Due to the ever-growing number of telephone exchanges, the harmful effects of traffic noise are recognized as one of the most widespread environmental problems of our time.

Currently, the world's leading manufacturers of automatic telephone exchanges are actively working to reduce noise emitted into the environment. In connection with the introduction of a new method for measuring external noise R-51-03, the noise from the ATS becomes the most significant source of external noise (along with bus noise) - both the gas-dynamic and structural components, as well as its measurement and regulation, are becoming increasingly important.

In this regard, the urgent task is to develop an economical, technologically advanced and reliable method for measuring noise, aimed at identifying and effectively assessing that part of the total noise of the vehicle exchanged in motion that is emitted by the AECS.

There are various methods and technical solutions for their implementation aimed at solving the above problem, for example, "Method for measuring the external noise of a Bazhenov motor vehicle" described in RF patent No. 2392603, 6MPK G01M 17/007, G01M 15/00, publ. 06/20/2010, consisting of:

- in performing a preliminary series of passages of the ATS in acceleration mode in various gears relative to a fixed microphone with the simultaneous measurement of the noise emitted during the passage of the ATS and the subsequent selection of the maximum value;

- in performing, on the same measured section, the first additional pass of the ATS in acceleration mode on a transmission corresponding to the maximum noise level recorded in the preliminary series of passages, and recording the spectrogram of the external noise of the ATS on a storage device;

- in calculating the characteristic frequencies of the vehicle units and applying them to the spectrogram recorded during the first additional drive;

- in the implementation of the second additional passage of the PBX with the recording of a noise spectrogram, moreover, before performing the second additional passage, the measuring microphone is installed on the PBX;

- in applying to the spectrogram of noise recorded as a result of the second additional driveway, the calculated values of the characteristic frequencies of the vehicle units;

- in the identification of noise sources according to the results of the second additional passage and their ranking according to the results of the first additional passage of the ATS.

The disadvantage of this method is the low accuracy of identification of noise sources, because the values of the characteristic frequencies, which are determining in the general noise levels of the sources, will be a multiple of the engine speed and the same for the engine and gas exchange systems.

Also known as "The method of measuring the external noise of the car" described in the patent of the Russian Federation No. 2262085, 7MPK G01M 17/00, G01M 17/007, publ. 10.10.2005, which consists in conducting a preliminary series of measurements of external noise, automatic telephone exchange, equipped with the studied AECS, in conducting an additional series of measurements of external noise of automatic telephone systems, equipped with an additional silencer, in addition to the initial AECS, and in determining the difference in the results of the contribution of AECS to external sound PBX field.

This method has several disadvantages. Firstly, an additionally connected silencer can adversely affect the dynamics of the car - therefore, it is impossible to assess what caused the decrease in external noise - a change in the dynamics of the ATS or a decrease in the exhaust noise. Secondly, the method under consideration makes it possible to indirectly estimate the gas-dynamic component of the noise of the AECS, while the structural noise of the silencers, which is also a significant source of external noise, is not evaluated.

As a prototype, as the closest in the set of distinctive features, the “Method for determining the noise emitted by silencers of the exhaust system of automobile engines” is described, described in RF patent No. 2292537, IPC G01M 15/00, G01M 17/007, G01M 19/00, publ . 01/27/2007, which consists in determining in laboratory conditions the spectrum of noise reduction by a muffler by applying acoustic noise to the input of a silencer, measuring noise inside the ATS exhaust system in the area of its junction with a silencer when the vehicle moves along a measured area in a mode corresponding to the maximum level of external ATS noise, in determining the noise spectrum inside the exhaust system and calculating the difference between the noise spectrum inside the exhaust system and the noise reduction spectrum of a silencer obtained in laboratory conditions, and also subsequently Calculation, according to the obtained difference, of the integral noise level minus the correction value corresponding to the noise attenuation at the distance of interest.

The method under consideration also has several disadvantages. Firstly, the sounding of the CBOG in laboratory conditions occurs at a temperature of about 20 ° C, while the operating temperature range of the CBOG mufflers is 300 ... 600 ° C. Secondly, this method also does not take into account the structural component of the noise of the CBOG.

The problem to which the application of the invention is directed is to obtain a technologically advanced, reliable and economical method for identifying the noise produced by the AECS in the total external noise of a vehicle in motion. The proposed calculation and experimental method, based on the aggregate data obtained during bench tests of the automatic telephone exchange, allows you to obtain the values of noise levels of both the gas-dynamic and structural components of each element of the ATS, in any position (position on the measured section) of the automatic telephone exchange in the normalized acceleration mode.

This problem is solved with technical equipment that meets the well-known requirements set forth in current regulatory documents, including GOST 31333-2006 (ISO 362-1: 2007), UNECE Rules 51, and EU Directive 540-2014.

The proposed method provides the following steps.

1. Measurement of external noise of the vehicle in road conditions:

- preparation of measuring equipment and test site with measuring area;

- measurement of noise levels of ATS moving along a measured section in acceleration mode, in accordance with the methods of the UNECE 51 Rules;

- recording by the storage device of the obtained values, including the values of the automatic telephone exchange speed, engine rotation frequency and noise levels with a given step of the automatic telephone exchange position in the measured section;

- obtaining the dependences of the values of the total noise levels and engine speed from the position on the measured section;

2. Measurement of noise in the laboratory on a bench with running drums:

- preparation of measuring equipment and installation of soundproof screens;

- measurements of the gas-dynamic noise of the exhaust and the structural noise of the mufflers when the engine is at full load in the engine crankshaft speed range, covering the engine crankshaft speed ranges corresponding to the acceleration of the vehicle in the gears under study during road tests;

- experimental determination of corrections for adjusting the structural noise of silencers;

- obtaining the dependences of the values of the general levels of structural and gas-dynamic noise, as a function of the engine speed.

3 Settlement part:

- drawing the noise levels of sources (structural noise of silencers and gas-dynamic noise of the exhaust) on the diagram with the external noise levels of the vehicle, by correlating the engine speed during bench and road tests, taking into account the distance correction, which determines the dependence of the noise level on the distance between the noise source and recording microphone.

- obtaining a diagram of the values of the noise levels emitted by each of the sources of the CBSS in each position of the measuring section given by the marks.

Features and advantages of the proposed method are illustrated by the following detailed description and illustrations, in which:

in FIG. 1 shows a diagram of the installation of microphones and soundproof shields when measuring noise in the near field, in bench conditions on running drums, side view and bottom view;

in FIG. 2 is a diagram — an example of the determination of corrective corrections in determining the structural noise of CBOG silencers;

in FIG. 3 shows a graph of the correction for the distance Δ - the dependence of the change in the noise level on the distance between the studied noise source of the telephone exchange and the microphone;

in FIG. 4 shows a diagram of a test site with a measuring section and measuring equipment for testing vehicles in motion;

in FIG. Figure 5 shows an example of the final diagram with external noise of the telephone exchange and the corrected noise of the sources of the ATS in each position of the telephone exchange.

The implementation of the proposed method is as follows.

As an example, let’s consider a CBOG with two silencers, an additional silencer (hereinafter referred to as exhaust gas) and a main silencer (hereinafter referred to as exhaust gas), as sources of structural noise and one exhaust pipe, as a source of gas-dynamic noise.

The studied ATS 1 is fixedly mounted on a dynamometer with running drums 2. The ATS operates in full load mode in the engine crankshaft speed range from a value corresponding to idle speed to a value corresponding to the nominal speed. At the PBX, soundproof screens 5 and microphones 6 and 7 are installed (Fig. 1).

During bench tests, the gas-dynamic component of the exhaust noise is measured at 0.25 m from the free cut of the exhaust pipe 3. The exhaust noise measurement zone is additionally isolated using a soundproofing screen 5.

When measuring the structural component of the noise of mufflers 3 and 4, microphones 6 are installed opposite the middle of each muffler, 0.25 m from its body, perpendicular to its surface, at a height of at least 0.2 m from the surface of the chamber floor. On the floor surface under the silencers and microphones to reduce the reflection of sound from the floor, sheets of sound-absorbing material (not shown) are laid. The zones for measuring structural noise are additionally isolated from the noise of the engine and the rotating front wheels with the help of sound-absorbing screens 5, fixed under the ATS bottom. Mufflers are also separated by soundproofing screens 5.

To take into account the contribution to the structural noise of “background” silencers from a running engine (power unit) and tire noise, measurements are made in the lower part of the motor compartment using a “reference” microphone 7.

Corrections for converting the sound levels of other ATS noise sources to the measurement points of structural noise of silencers 3 and 4 are determined experimentally, since the sound field under the bottom of the car cannot be considered a free sound field, and sound sources are point sources. To do this, noise measurements are taken at all points of installation of microphones 6, as when measuring structural noise of mufflers 3 and 4, when the engine is idle and the gearbox of the ATC 1 is neutral. The front wheels of the ATC 1 are driven by the running drums 2 controlled by the stand in uniform mode a set of revolutions of the drums 2, corresponding to the investigated range of revolutions of the engine crankshaft. In this case, the noise generated by the contact of the rotating wheels and the surface of the running drums is used as a source of broadband noise.

An example of corrective corrections (sound attenuation when moving away from the source) is presented in the diagram of FIG. 2, from which it can be seen that the noise levels measured at the points of assessment of the structural noise of the engine decrease when the point of measuring body noise DG 4 is reached by an average of 16 dB, and when the point of exhaust gas 3 is reached by another 7 dB. These values are taken to calculate the corresponding corrective amendments. Thus, the adjusted, taking into account the background, noise for exhaust gas 3 is determined by the formula:

and for DG 4 according to the formula:

where L _{k_og} - the corrected level of body noise of the main muffler;

L _{s_og} - the measured level of body noise of the main muffler;

L _{k_dg} - the corrected level of body noise of an additional silencer;

L _{s_dg} - the measured level of body noise of an additional silencer;

L _{z_dv} - the measured level of the noise of the engine body.

As a result of bench tests of the CBOG, we obtain the levels of gas-dynamic exhaust noise and structural noise of silencers as a function of engine speed.

For road tests, a test site is being prepared with a measured section, which is a horizontal rectilinear surface with a hard and even coating, the acoustic characteristics of which allow, under conditions of free sound field, the occurrence of noise interference between the sound source and the microphone in excess of 1 dB.

The measured area is indicated on the test site with lines (Fig. 4):

AA '- line fixing the position of the front part 8 of the moving ATS 1;

BB '- line fixing the position of the rear part 9 of the moving ATS 1;

SS '- the axial line coinciding with the longitudinal axis of the moving ATS 1;

PP '- the line on which the microphones 10 are located, installed on both sides of the CC' line at a distance of 7.5 m and directed at each other at a height of 1.2 m above a horizontal surface.

The total length of the measured section is 20 meters plus the overall length of the ATS 1 behind the line BB '. The lines AA 'and BB' are respectively located 10 m in front and behind the line PP '. Measuring instruments (microphones 10, a tachometer for monitoring engine revolutions (not shown), GPS-GLONAS 11 for monitoring the speed of the automatic telephone exchange and its position in the measured section) are connected via high-speed connection to storage device 12, and then to computer 13.

A series of measurements of the noise levels of the ATS 1 is carried out, in acceleration mode, in which the ATS 1 moves in a straight line, towards the measuring section, so that the plane of the longitudinal section of the ATS 1 is as close as possible to the CC 'line. At the moment when the front part 8 of the ATS 1 crosses the line AA ', the fuel pedal (not shown) is pressed fully and as quickly as possible and is held in this position until the rear part 9 of the ATS 1 crosses the line BB' .

At the same time, on the storage device 12, the obtained values are recorded, including the values of the engine crankshaft revolutions of the ATS 1 engine and noise levels with a given step of the position of the ATS 1 in the measured section.

Then, the values of the levels of each of the sources of noise in the CBOG (structural and gas-dynamic) obtained during bench tests are recalculated to the point of measurement of the external noise of the ATC 1 during road tests (according to method R51) and correlated with the values of the crankshaft speed of the ATC 1 engine, recorded when driving in overclocking. The obtained result is adjusted taking into account the correction Δ (see Fig. 3), which determines the dependence of the change in the noise level on the distance between the noise source and microphones 10 and calculated by the formula:

where S is the distance between the noise sources (silencers and the radiating section of the exhaust pipe) and the microphone line PP ', m;

7.5 - distance from the longitudinal line CC '(ATS axis) to the measuring microphones, m

Thus, the values of the noise levels of each source of the CBOG with a given step of the ATS position on the measured section at the same engine crankshaft rotations as when entering the measured section are obtained, both general noise levels and ⅓ octave spectra.

The advantage of the proposed method is that its use allows you to obtain reliable indicators of the noise level of the AECS in the normalized driving modes in each position of the ATS in the measured section and, accordingly, determine and rank the share of the noise contribution of each of the noise sources of the AECS in the total external noise level of the ATS.

This method has been successfully tested in the study and refinement of cars in PJSC AvtoVAZ.

Claims (3)

The method of evaluating the noise emitted through the exhaust system as one of the sources of external noise of a vehicle in motion, which consists in a series of road and bench tests and the subsequent calculation of the proportion of external noise generated and emitted through the exhaust system, characterized in that they measure the levels of external noise of a vehicle moving along a measured section in acceleration mode, with registration by a storage device received beginnings, including the values of the engine crankshaft revolutions and noise levels with a predetermined step in the position of the vehicle in the measured area, then the bench measurements of the noise of the exhaust system in the near field are carried out when the vehicle is installed on the running drums of the same vehicle when the engine is in full load in the range engine crankshaft speed from a value corresponding to idling to a value corresponding to a nominal speed, while, to eliminate background noise, res Measurement lats are adjusted taking into account experimentally determined corrections, then recalculated taking into account the correction for signal attenuation as you move away from the source and the distance corrections depending on the position of the vehicle (and therefore its individual units - noise sources) in the measured area and determined by the formula

where S is the distance between the noise sources (silencers or the emitting cut of the exhaust pipe) and the microphone line, then the obtained values of the noise levels of the exhaust system, structural and gas-dynamic, are correlated with the values of the engine crankshaft RPM recorded when the vehicle is moving in acceleration mode, and get the values of the noise levels of each source of the exhaust system (exhaust gas system) with a given step position of the vehicle (ATS) in the measured area at the same engine crankshaft revolutions, as when driving in a measured section, both general noise levels and

octave spectra in each position of the ATS in the measured area.

Images