CN109426686B - Acoustic one-dimensional analysis method for exhaust system - Google Patents

Abstract

The invention relates to the field of automobile exhaust, in particular to an acoustic one-dimensional analysis method for an exhaust system, which comprises the following steps: the first step is as follows: according to the pipeline trend of the exhaust system and the structure of the silencer, a GEM3D module in GT software is used for establishing a three-dimensional solid model of the exhaust system; the second step is that: after a 3D model is established, carrying out detailed technical definition on relevant parameters of the model; the third step: taking an engine as a noise source, and checking a one-dimensional engine model; the fourth step: dispersing the established 3D model of the exhaust system into a one-dimensional model, combining the one-dimensional model with the engine model and the intake system model into a complete 'intake system-engine-exhaust system' analysis model, and then performing noise analysis at the exhaust tail pipe opening; the fifth step: and extracting the Overall total value and second-order, fourth-order and sixth-order noises of the exhaust system, and carrying out real vehicle verification. The method ensures the precision of the model, improves the acoustic development efficiency of the exhaust system, and saves the development period and cost of exhaust.

Description

Acoustic one-dimensional analysis method for exhaust system

Technical Field

The invention relates to the field of automobile exhaust, in particular to an acoustic one-dimensional analysis method for an exhaust system.

Background

With the development of society and the progress of technology, people have higher and higher requirements on modern automobiles. In particular, noise and vibration problems in automobiles have attracted more attention. Exhaust noise is one of the major noise sources in automobiles, and can be propagated into the automobile through air to directly affect the feeling and comfort of passengers. Among exhaust noises, exhaust noises having low frequency have the greatest influence on people. Therefore, the silencer needs to be designed to reduce exhaust noise, so that the exhaust noise meets the NVH design target, and the NVH level of the whole vehicle is guaranteed.

In early development design of exhaust systems, many host plants and exhaust suppliers use GT for acoustic simulation, but lack high-precision control flow and calculation methods.

Disclosure of Invention

The invention aims to solve the problems and provides an acoustic one-dimensional analysis method for an exhaust system.

In order to realize the purpose of the invention, the invention adopts the technical scheme that:

an acoustic one-dimensional analysis method for an exhaust system comprises the following steps:

the first step is as follows: according to the pipeline trend and the silencer structure of the exhaust system, a GEM3D module in GT software is used for establishing a three-dimensional solid model of the exhaust system; a. 3D modeling of the muffler: establishing the external contour of a silencer, establishing a partition plate of the silencer, establishing the number of perforations of the partition plate, establishing pipelines, small holes and sleeves in the silencer, establishing the sleeves by using a sleeve command for the structure with the sleeves in the silencer, and establishing sound-absorbing cotton by using wood for the structure with the sound-absorbing cotton in the silencer; b. establishing an outer pipeline model: for a single-row exhaust system, a pipeline is established by utilizing a pipeline establishing command according to the contour and relative coordinates of the pipeline, the established pipeline must be ensured to be consistent with the actual trend and position, and the pipeline is cut into a plurality of small sections of regular small pipes; for the Bent Pipe, Pipe in 3D with Bends or Bent Pipe is used for conversion according to the shape of the Bent Pipe; for Straight tubes, conversion is performed with Straight Pipe or Round Pipe; for the Y-shaped pipeline in the double-row exhaust system, flowscope is used for conversion; c. Establishing an exhaust system model: combining the three-dimensional model of the silencer and the three-dimensional model of the pipeline by using a Connection command to form a complete exhaust system model;

the second step is that: after the 3D model is built, the detailed technical definition of the relevant parameters of the model is as follows: initial tube wall temperature: defining the temperature as the measured temperature of the initial wall surface of the exhaust system; wall temperature solution settings: defining the temperature and thermal convection coefficient of the heat exchange; external environment: defined as the ambient temperature and pressure outside the exhaust system; fluid medium: the fluid medium is an air medium, and the initial temperature of the air medium is consistent with the initial temperature of the pipe wall; surface roughness: defined as the exhaust system surface roughness; acoustic wool parameter definition: the sound absorption material is defined according to the density, specific heat capacity, diameter, flow resistance coefficient and working temperature of the sound absorption cotton material;

the third step: taking an engine as a noise source, performing one-dimensional engine model checking, wherein the checking parameters are required to be as follows: a. checking the air flow, the engine power, the engine oil consumption and the pressure drop of an intercooler before and after the air compressor; b. checking the temperature and the pressure of the air compressor inlet of the air compressor; c. checking the pressure of the exhaust port of the compressor for the exhaust port of the compressor;

the fourth step: dispersing the established 3D model of the exhaust system into a one-dimensional model, combining the one-dimensional model with the engine model and the intake system model into a complete 'intake system-engine-exhaust system' analysis model, and then performing noise analysis at the exhaust tail pipe opening;

the fifth step: and extracting the total value of the overhall and the second, fourth and sixth-order noises of the exhaust system, wherein the fluid noise value contained in the overhall curve is an empirical evaluation value, comparing the target curves of the second, fourth and sixth-order noises and the Overall value of the overhall, and if the total value of the overhall and the second, fourth and sixth-order noises reach the standard, carrying out real vehicle verification, and if the total value of the overhall and the second, fourth and sixth-order noises do not reach the standard, carrying out next round of optimization on the noise of the exhaust system.

The invention has the beneficial effects that: the exhaust noise is predicted and optimized by adopting a one-dimensional analysis control method, so that the acoustic development efficiency of an exhaust system can be greatly improved, and the exhaust development cost is saved. By applying the acoustic one-dimensional analysis method of the exhaust system, the exhaust order noise within 300Hz can be accurately predicted, the influence of the noise of the exhaust tail pipe opening on the NVH of the whole vehicle can be effectively predicted, and meanwhile, the optimization of the exhaust system can be guided.

Drawings

Figure 1 is a flow chart of an acoustic one-dimensional analysis of an exhaust system of the present invention,

FIG. 2 is a schematic three-dimensional modeling of a muffler of an exhaust system.

Detailed Description

The invention is further illustrated with reference to the following figures and examples:

example (b): see fig. 1 and 2.

An acoustic one-dimensional analysis method for an exhaust system comprises the following steps:

the first step is as follows: according to the pipeline trend and the silencer structure of the exhaust system, a GEM3D module in GT software is used for establishing a three-dimensional solid model of the exhaust system; a. 3D modeling of the muffler: establishing the external contour of a silencer, establishing a partition plate of the silencer, establishing the number of perforations of the partition plate, establishing pipelines, small holes and sleeves in the silencer, establishing the sleeves by using a sleeve command for the structure with the sleeves in the silencer, and establishing sound-absorbing cotton by using wood for the structure with the sound-absorbing cotton in the silencer; b. establishing an outer pipeline model: for a single-row exhaust system, a pipeline is established by utilizing a pipeline establishing command according to the contour and relative coordinates of the pipeline, the established pipeline must be ensured to be consistent with the actual trend and position, and the pipeline is cut into a plurality of small sections of regular small pipes; for the Bent Pipe, Pipe in 3D with Bends or Bent Pipe is used for conversion according to the shape of the Bent Pipe; for Straight tubes, conversion is performed with Straight Pipe or Round Pipe; for the Y-shaped pipeline in the double-row exhaust system, utilizing flowPLit to carry out conversion; c. Establishing an exhaust system model: combining the three-dimensional model of the silencer and the three-dimensional model of the pipeline by using a Connection command to form a complete exhaust system model;

the second step is that: after the 3D model is built, the detailed technical definition of the relevant parameters of the model is as follows: initial tube wall temperature: defining the temperature as the measured temperature of the initial wall surface of the exhaust system; wall temperature solution settings: defining the temperature and thermal convection coefficient of the heat exchange; external environment: defined as the ambient temperature and pressure outside the exhaust system; fluid medium: the fluid medium is an air medium, and the initial temperature of the air medium is consistent with the initial temperature of the pipe wall; surface roughness: defined as the exhaust system surface roughness; acoustic wool parameter definition: the sound absorption cotton material is defined according to the density, specific heat capacity, diameter, flow resistance coefficient and working temperature of the sound absorption cotton material;

the third step: taking an engine as a noise source, performing one-dimensional engine model checking, wherein the checking parameters are required to be as follows: a. checking the air flow, the engine dynamic rate, the engine oil consumption and the pressure drop of an intercooler before and after a gas compressor after a throttle valve; b. checking the temperature and the pressure of the air compressor inlet of the air compressor; c. checking the pressure of the exhaust port of the compressor for the exhaust port of the compressor;

the fourth step: dispersing the established 3D model of the exhaust system into a one-dimensional model, combining the one-dimensional model with the engine model and the intake system model into a complete 'intake system-engine-exhaust system' analysis model, and then performing noise analysis at the exhaust tail pipe opening;

the fifth step: and extracting an Overall total value and second-order, fourth-order and sixth-order noises of the exhaust system, wherein the fluid noise value contained in an Overall curve is an empirical evaluation value, comparing target curves of the second-order, fourth-order, sixth-order and Overall total values, and performing real vehicle verification if the Overall total value and the second-order, fourth-order and sixth-order noises reach the standard, or performing next round of optimization on the exhaust system noises if the Overall total value and the second-order, fourth-order and sixth-order noises do not reach the standard.

The embodiments of the present invention are disclosed as the preferred embodiments, but not limited thereto, and those skilled in the art can easily understand the spirit of the present invention and make various extensions and changes without departing from the spirit of the present invention.

Claims (1)

1. An acoustic one-dimensional analysis method for an exhaust system is characterized by comprising the following steps:

the first step is as follows: according to the pipeline trend and the silencer structure of the exhaust system, a GEM3D module in GT software is used for establishing a three-dimensional solid model of the exhaust system;

a. 3D modeling of the muffler: establishing the external contour of a silencer, establishing a partition plate of the silencer, establishing the number of perforations of the partition plate, establishing pipelines, small holes and sleeves in the silencer, establishing the sleeves by using a sleeve command for the structure with the sleeves in the silencer, and establishing sound-absorbing cotton by using wood for the structure with the sound-absorbing cotton in the silencer;

b. establishing an outer pipeline model: for a single-row exhaust system, a pipeline is established by utilizing a pipeline establishing command according to the contour and relative coordinates of the pipeline, the established pipeline must be ensured to be consistent with the actual trend and position, and the pipeline is cut into a plurality of small sections of regular small pipes; for the Bent Pipe, Pipe in 3D with Bends or Bent Pipe is used for conversion according to the shape of the Bent Pipe; for Straight tubes, conversion is performed with Straight Pipe or Round Pipe; for the Y-shaped pipeline in the double-row exhaust system, utilizing flowPLit to carry out conversion;

c. establishing an exhaust system model: combining the three-dimensional model of the silencer and the three-dimensional model of the pipeline by using a Connection command to form a complete exhaust system model;

the second step is that: after the 3D model is built, the detailed technical definition of the relevant parameters of the model is as follows:

initial tube wall temperature: defining the temperature as the measured temperature of the initial wall surface of the exhaust system; wall temperature solution settings: defining the temperature and thermal convection coefficient of the heat exchange; external environment: defined as the ambient temperature and pressure outside the exhaust system; fluid medium: the fluid medium is an air medium, and the initial temperature of the air medium is consistent with the initial temperature of the pipe wall; surface roughness: defined as the exhaust system surface roughness; acoustic wool parameter definition: the sound absorption material is defined according to the density, specific heat capacity, diameter, flow resistance coefficient and working temperature of the sound absorption cotton material;

the third step: taking an engine as a noise source, performing one-dimensional engine model checking, wherein the checking parameters are required to be as follows:

a. checking the air flow, the engine dynamic rate, the engine oil consumption and the pressure drop of an intercooler before and after a gas compressor after a throttle valve;

b. checking the temperature and the pressure of the air compressor inlet of the air compressor;

c. checking the pressure of the exhaust port of the compressor for the exhaust port of the compressor;

the fourth step: dispersing the established 3D model of the exhaust system into a one-dimensional model, combining the one-dimensional model with the engine model and the intake system model into a complete 'intake system-engine-exhaust system' analysis model, and then performing noise analysis at the exhaust tail pipe opening;

the fifth step: and extracting an Overall total value and second-order, fourth-order and sixth-order noises of the exhaust system, wherein the fluid noise value contained in an Overall curve is an empirical evaluation value, comparing target curves of the second-order, fourth-order, sixth-order and Overall total values, and performing real vehicle verification if the Overall total value and the second-order, fourth-order and sixth-order noises reach the standard, or performing next round of optimization on the exhaust system noises if the Overall total value and the second-order, fourth-order and sixth-order noises do not reach the standard.

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