Experiment Analysis on Noise of the Minibus Exhaust Muffler

On the basis of analysis and research on an automobile exhaust noise, the theory and test combination method was adopted to improve the muffler, and then the acoustics performance of muffler was validated by doing some experiments with the engine. On different speeds of the engine, the inserting loss and spectrum characteristic under several muffler methods were studied. Finally the best muffler method was confirmed, and the purpose of reserving was achieved.     

Numerical simulation of the flow and temperature fields in an automotive exhaust muffler

By building a model of a typical exhaust muffler structure, a grid mesh was formed based on the calculation characteristic of the flow field. The software ANSYS CFX then was used to numerically simulate the flow and temperature fields in a muffler. The effects of the gas velocity and temperature variation on sound elimination performance, including the acoustics and aerodynamics performance, were analyzed. The result suggests that high velocity turbulence and high speed flow should be eliminated from muffler structures when designed. At the same time, to provide satisfactory noise elimination, pressure loss should be reduced as far as possible. The pressure loss can be decreased when reducing the perforation structure.     

Acoustics simulation and structure optimization of a motorcar exhaust muffler

Aiming at the exhaust muffler of a 244S motorcar, the acoustics field model and the flow field model are established by adopting Finite Element Method. The 3-D acoustic simulation is carried out by using software SYSNOISE, and an improvement scheme with optimized inner structure of the muffler is proposed based on the simulation. The acoustic simulation result and the bench test result of the improved muffler show that the muffling ability in middle and high-frequency of the improved structure is obviously stronger than the original structure, and the simulation result coincides well with the bench test result. Meanwhile, the flow field simulation result shows the power loss of the engine has little change, which means that the structure improvement of the original muffler is effective.     

Accelerated Vehicle Exterior Noise Control of Minicar SC6360B

This paper studyies the method of controlling SC6360B's accelerated vehicle Exterior noise. First, the main noise is found, which is from engine compartment and from exhaust noise by the identification of vehicle noise resource. Second, this paper carris out the farther noise identification experiment on engine and the insert-loss experiment on the exhaust gas muffler. In the end, the authors make sure that the noise is mainly infected by direct leaked noise from engine compartment, radiation-noise caused by the vibration of engine accessories and loud exhaust noise because the muffler has dficient elimination . The corresponding methods has been adopted according to the analysis. Through the test, the noise is lowered 2.5 dBA than it was and reach the new requirement.     

Numerical Analysis of Flow and Acoustic Field Inside the Automobile Exhaust Muffler

The acoustic field,flow field and temperature field inside a muffler are studied by the numerical analyze method.And an improved design is made aiming at the existent problem.The comparison of the computationally predicted and the experimentally measured transmission loss shows a good agreement.It is indicated that the numerical analysis method can simulate the exhaust muffler's characteristic accurately.So it is an effective method to predict exhaust muffler's performance and have an improved design.     

Dynamic characteristic analysis of an all terrain vehicle body

The body is a key part of all terrain vehicles (ATV). Its dynamic characteristics greatly effect the vibration of the ATV assembly. Simulation and experimental methods are combined to analyze ATV body vibration characteristics. A computer aided design(CAD) model is built using UG4.0. A finite element method(FEM) model of an ATV body and a body with an engine are created using Hypermesh. The FEM model is imported to Msc.Nastran to calculate the free mode. The simulation model is verified by the experimental modal result. The results indicate that after the frame with engine, the first bending mode increases due to the engine increasing the body stiffness, while the first torsion mode decreases due to the engine mass. The effects on the dynamic response of the road and engine excitation are analyzed respectively. Vibration characteristic improvement methods and suggestions regarding the body are provided.     

THE RESEARCH OF MONITORING AND DIAGNOSING BALL BEARING FATIQUE ON LINE

This paper describes the research work of analyzing vibration signal to monitor and diagnose on line the ball bearing fatique. Carrying out a large mumber of life test on ball bearing test machine, it is discovered that in the so called "second effect" vibration signal as the bearing fatique occurs, apart from the two widely used spetrum charactersof "fraverse frequency" and "high frequency shock pulse" , there is another important but rarely known opcctrum characteristic of high frequency peaks existing in the middle-to-high frequency band.The generating mechanism, effect factors and test method of those high frequency peaks are researched tentativ tentatively. Two binds of device for monitoring abnd diagnos sing ball learing fatique on line are developed based ion this new type spectrum characteristic. One consists of a bandpass filter, the other is based on the spetrum characters which corns from the DDS ( Dynamic Data System ) modeling     

Calculation on Natural Frequency and Main Vibration Mode of Double-lined Type Mounting System

The vibration characteristic of engine mounting system is analyzed, the vibration model of engine mounting system is established, and calculation method of natural frequency and main vibration mode of mounting system is put forward. Then an engine mounting system with double - lined type isolator is presented. Isolation performance of engine mounting system is improved greatly by selecting elastic coefficient of isolator reasonably.     

Dynaical Mathematical Model of String

In the process of oil drilling, drilling string and rock bit are main drilling tools. The fact of their failure would cause serious accidents. To solve this problem, the vibration law of string should be found. The longitudinal vibration model, torsional model and lateral vibration model are founded simultaneity. Many methods are used to build up this model, including finite element technique, numerical technique and computer simulation. The dynamic model reveals the dynamic action of string, it is instructive to design new rock bit and study drilling mechanics.     

Vibration Analysis and System Simulation for a Stalled Wind Turbine

The aerodynamic characteristic of wind turbine is calculated by applying the Blade Element Momentum(BEM) theory.Also finite element mode analysis is done for the tower and the rotor.Then the multi-dynamic model of the wind turbine is built in Adams.Also the drive chain is calculated by applying state space method and programmed in Matlab/ Simulink.With that the combined simulation of vibration characteristics is carried out on the base of MATLAB/Simulink and ADAMS,in which the transmission effects and aero-elasticity coupling is fully considered.The results show that the method is able to simulate the vibration characteristic almost the same as software Bladed,which is well-known for analyzing performance and loads for the design and certification of wind turbines.     

Dynamic Analysis of a New Nano-CMM Structure

Dynamic analysis of a new Nano-CMM(Coordinate Measuring Machine with nanometer resolution) structure is introduced,including vibration characteristic analysis and vibration response analysis.The aim is to assess and analyze dynamic accuracy of structure.Modal and harmonic analysis were made by ANSYS software based on establishing equation of vibration,so as to achieve natural frequency and fundamental vibration mode of structure,and also the displacement and stress of structure under nanomotion motor driving.Moreover,the analysis and comparison of rectangular-bridge and arch-bridge are made in order to prove the superiority of dynamic accuracy of the symmetrical-bridge structure.     

DYNAMIC ANALYSIS OF ASYMMETRIC FRAME-SHEAR WALL SYSTEM BY STAGE CONTINUITY METHOD

The lateral structures of frame-shear wall system are simplified into bending beams and shear beams which stiffness can vary in different stages along the building height. The three-dimension stiffness matrix and mass matrix are deduced, and the characteristic equation is established to calculate the tortuous free vibration of the asymmetric system. The method is simple and has satisfactory precision, and it is easily fulfilled in micro-computers.     

厅堂侧向能量因子的仿真与实测

侧向能量因子是衡量厅堂空间感的重要客观指标之一。厅堂侧向能量因子通常采用计算机仿真的方法得到。首先采用MKH800电容型传声器在实际厅堂中开展侧向能量因子测试工作。然后,通过ODEON6.5建立厅堂三维仿真模型,计算相同位置处侧向能量因子的模拟值,并将实测值与模拟值进行对比分析。研究结果表明,各点位的仿真值均大于实测值,座席区前部偏差较小,正对舞台中后部区域偏差较大。造成偏差的主要原因是由于ODEON软件中扩散系数的设置与所在面特性无关,同时,软件无法分别定义各频段的扩散系数。因此,在实际工程项目中,为了准确地预测室内音质效果,建议普遍采用缩尺模型实验测量侧向能量因子。     

A Study on Vibration Isolation for the Machine on Flexible Foundations

The problem of vibration isolation for the multi supporting machine installed on flexible foundations was studied by power flow and four end parameters methods.The general model of machine,isolator and flexible foundations was founded,and the transmission characteristic of the vibration system is analyzed.The expressions of power flow of the system with wave propagation effect being concerned was also presented.Finally,the effect of foundation flexibility and wave propagation on isolation was analyzed in detail.     

A valve camshaft load torque calculation and camshaft vibration control analysis

Aiming at the overhead camshaft valve mechanism,the theoretical and numerical solutions of camshaft load torque are calculated respectively by a derived formula and transient finite element analysis. The two solutions show good agreement,thus the correctness of the transient finite element model is verified. By combining with camshaft instantaneous constraint modal analysis and vibration response with consideration of gas pressure,it is found the position of camshaft which easily excites resonance and the main influence factors of camshaft vibration. Then the effect of the width of bearing seat on the camshaft vibration is investigated and the results show that the vibration of camshaft is mainly bending vibration,appropriate width of bearing seat can effectively control the camshaft vibration.     

Analyse of Compressor Sound Quality

By of Stevens steady wide frequency noise loudness and Fastl total sensation noise calculation method, sound quality evaluation of the noise left and back-end face was studied before the compressor improved and after the minipore muffler installed. The research indicates that the compressor noise is reduced, at the same time, the loudness left the compressor and the back - end face is reduced by 10.25 sone and 13.3 sone respectively. The rate reduced is over 40%. The total sensation noise is reduced by 12.5 noy and 15 noy, the rate achieved is over 45%. It is very perfect to improve the compressor sound quality with the use of minipore muffler.     

Acoustical Design of Gymnasium in Harbin Normal University Sports Center

Gymnasium in Harbin Normal University Sports Center is a large-scale gymnasium. This paper analyzes unfavorable factors in its acoustics and illustrates different kinds of intention of the design. At the same time, the questions about the project operation and technique are pondered one by one, it is expected that these thinking can provide some experience to the similar project.     

大攻角及桥面粗糙度对扁平钢箱梁涡振性能的影响

为探究大攻角及桥面粗糙度对扁平钢箱梁涡振性能的影响,对寸滩长江大桥主梁进行了风洞试验。应用Matlab软件模拟桥面粗糙度变化范围,根据模拟结果选取对应的砂纸在试验中模拟桥面粗糙度,分析了攻角及桥面粗糙度对扁平钢箱梁涡振区间及幅值的影响。试验研究表明:在大攻角下扁平钢箱梁的涡振振幅和范围明显增大,对桥址位于山区等容易发生大风攻角的地区的桥梁应进行大攻角试验。扁平钢箱梁的涡振响应随着桥面粗糙度增大而减小。正攻角范围内,桥面粗糙度对涡振响应的影响随着攻角减小而增大。桥面粗糙度发生变化时,扭转涡振响应更加敏感,变化幅度大于竖向涡振响应变化幅度。     

Calculation Method for Equivalent Model of Regular Isolated Structure with Bend shear Deformation

Isolation technique was not only applied for middle or low buildings, but also recently it was applied to high rise buildings. For high rise buildings, multi order vibration should be considered for upper structure isolation and bend deformation should be taken into account in gross deformation because of large height to width ratio. On the basis of previous studies, calculation method of equivalent model for regular isolated structure with bend shear deformation characteristic was proposed according to equivalent criteria after the analysis for some model structures. With the proposed model, handwork calculation of earquake response for isolated structure can be simply completed and design efficiency of isolation structure was improved. Based on the case studies, the equivalency of proposed model was approved.     

Fault diagnosis based on least square support vector machine optimized by genetic algorithm

A new fault diagnosis model is proposed based on Multi-Class Least Square Support Vector Machine optimized hierarchically by Genetic Algorithm(GA). Original vibration signals are decomposed into several stationary IMFs. Then the instantaneous amplitude energy of the IMFs with fault modulation characteristics is computed and regarded as the input characteristic measure of the Poly-kernel Multi-Class LS-SVM for fault classification. EMD decomposition adaptively isolates the fault modulation signals from original signals. The differences among instantaneous amplitude energy vectors reflect the separability of different fault types. Adopting GA to optimize punish parameter and Poly-kernel parameters hierarchically can not only enhance fault prediction accuracy of Multi-Class LS-SVM with Poly-kernel, but also improve adaptive diagnosis capacity of LS-SVM. The GA-based hierarchical optimization is also applicable to Multi-Class LS-SVM with Lin-kernel, RBF-kernel or Sigmoid-kernel. The deep groove ball bearings fault diagnosis experiment shows the effectivity of this new model.