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.     

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.     

simulation and improvement of an all terrain vehicle muffler

Aiming at a muffler of a 400 all terrain vehicle(ATV), a vibration model and an acoustics model of the muffler were built by finite element method(FEM). The vibration and acoustics characteristic analysis of the muffler are carried out according these models, it shows the 3D model is exact and it is possible to generate regeneration noise. Acoustics model can help to know further about the characteristic of each chamber and intention of the designer. According the demand of factory, some projects of improvement are offered. The final result of road test proves that he improved muffler is feasible.     

Numerical simulation of dynamic response and radiation noise of gearbox

Considering the internal dynamic excitation produced by stiffness excitation, error excitation and mesh impact excitation, a dynamic finite element model of transmission system and structure system of gearbox is established. The normal mode and the dynamic responses of gearbox under the internal dynamic excitation are calculated by using the numerical simulation software ANSYS. Based on the result of dynamic responses, the boundary excitation condition is determined, and then the acoustic boundary element model is built. With the software of SYSNOISE, the surface acoustic pressure of gearbox and the radiation noise of field points are solved by the direct boundary element method. The test of airborne noise is carried out. The computational results obtained are in a good agreement with the data of experimental test.     

Heat dissipation optimization of DC-DC and IPU for hybrid electric vehicle

Due to the bad heat dissipation of the existing heat dissipation structure of DC-DC and IPU for hybrid electric vehicle(HEV), the temperature of DC-DC and IPU will rise during the running process, which in turn decreases the stability and reliability of the hybrid electric system. Aiming at this problem, a three-dimensional, transient heat dissipation model is built for DC-DC and IPU heat dissipation structure based on the mass, momentum and energy conservation equations. By using computational fluid dynamics (CFD) software, flow field and temperature field of DC-DC and IPU heat dissipation structure are numerically simulated. Based on the simulation, and combined with heat transfer theory, an improvement scheme of heat dissipation structure is proposed. The simulation results and experiment results of thermal performance and temperature rise show that the improvement scheme can improve the thermal performance, and decrease the temperature rise of DC-DC and IPU effectively, thus satisfy the application requirements in HEV.     

A control system for vehicle applications of high-blend methanol gasoline

The ordinary gasoline engines could not be fueled by high-blend methanol directly. A MCU-based high-blend methanol gasoline control system is designed to extend the injection pulse width. PROTEUS simulation and test bench are validated. Flyer M-TCE engines burning M85 go smoothly. The results indicate that the high-blend methanol gasoline control system caneffectively control the engine injection mass without changing the original Electronic Control Unit , and make it feasible to apply high-blend methanol gasoline to the ordinary gasoline engines.     

The cooling structure of Ni MH batteries in hybrid electric vehicles

Focusing on Ni MH batteries used in hybrid electric vehicles (HEV), a simulation analysis of the flow and temperature fields of the cooling structure in existing batteries is carried out using computational fluid dynamics software. The results show that the temperature uniformity is poor. The uniformity of the flow and the temperature fields is improved by adjusting the baffle and battery positions, changing the tilt angle and the distance between the batteries, inserting wind plates and a coating insulation layer. The coating insulation layer achieves the best effect. Further simulation shows that the coating insulation layer method has the best effects. The results provide the design basis for thermal management program of Ni MH batteries in HEV.     

密集烤房内温度与气流分布数值模拟研究

提高烤房内温度及气流组织分布的均匀性,不仅可有效提高烟叶烘烤质量,而且可在一定程度上缩短烘烤时间,从而降低烘烤能耗。以密集型标准烤房为模拟研究对象,建立了装烟室内空气流动的k-ε两方程三维紊流模型。利用大型计算流体力学软件Fluent,对密集烤房内温度场及速度场进行了系统地数值模拟。分析了装烟室内温度及气流分布的均匀性,并获得了密集烤房合理的送风量。相关的数值模拟结果可为密集烤房结构、气流组织分布优化及循环风机选型提供参考。     

Model and Numerical Analysis of Radiation Field Created by Lightning Overvoltage Wave on Transmission Lines

The radiation field created by the transmission line stroked by lightning far from the lightning channel has been analyzed by the FDTD method.The authors we establish the calculation model and FDTD calculation method of transmission line,and discusses the import of lightning excitation source.The simulation of lightning stroked on a single transmission line in free space or stroked on three-phase high voltage transmission lines in actual environments has been done,and gives the distribution of transient radiation field around the transmission lines when lightning overvoltage wave transmits along the transmission line.The simulation result shows that: the effect of the transient radiation field caused by lightning over voltage wave done with environment is obvious,and the high frequency component of transient radiation field may disturb or do harm to the electronic facility or communication facility around the transmission lines.     

Hybrid field network simulation of temperature in a building fire

A connecting platform between the field model and network model has been constructed, based on a multi functional building model. The field model is used to simulate the fire smoke in certain special compartments (the fire room and specific large space rooms), while the network model is used to simulate the uniform compartments. When combining the simulation results of the field model and network model as the interface boundary conditions for the each other, a hybrid field and network model is presented. The hybrid field network model can provide more detailed physical information of the fire smoke properties under a specific fire scenario for the specially confined compartments. In addition, the hybrid model can predict the fire smoke flow properties in the building accurately.     

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.     

海南海花岛软基处理工程中真空预压法的改进与机理分析

疏浚淤泥这种超软土地基目前主要采用排水固结法进行加固,然而,工程实践发现,淤堵是一个重要的问题,新型防淤堵材料和施工工艺是研究的热点。依托恒大海南海花岛真空预压处理工程,引入一种应用于超软土地基处理的新型防淤堵真空预压法。该方法是直排式真空预压方法的进一步改进,将防淤堵排水板取代传统排水板,在连接方式上,将无孔钢丝软管取代了水平波纹管,也将传统的包扎捆绑改进成了三通密封接头,枪钉固定。结合施工动态监测和加固后检测,表明了该方法的加固效果和实用性。在此基础上,结合已有的室内模型试验研究,阐述其抽真空过程中在排水板附近防淤堵的原理和改善机制。     

Numerical simulation of gas solid characteristics in double inlet square cyclone separator

This paper uses RSM turbulence model to conduct the numerical simulation on the gas flow field in double inlet square separator and calculate the velocity field and pressure distribution in the seperator. At the same time, it simulates the solid particle trajectories in the separators using Lagrangian model. The results show that the velocity field and pressure distribution in double inlet square separator have good symmetry, but the flow swirl intensity is insufficient and easy to decay; different sizes and different injection locations bring significant differences for the particle trajectories; injecting small particles can be easy to form flow short-circuit phenomenon inside the separator, injecting particles near the top of separator can be easy to form top ash ring phenomenon inside the separator; these phenomena have adverse factors to the separation efficiency. When the separation cylinder corners of square separator are changed into cutting-shaped chamfers, the flow field in the separator can be improved, and the separation efficiency of separator can be effectively improved.     

A panel model of isotope concentration-flow coupled field in groundwater systems

Several previous general lumped parameter model of radioisotope concentration field in groundwater systems, such as EM, PM and EPM model, are introduced, and the ambiguous physical meaning of response functions within these models are pointed out.And then, based on the radioactive decay principles and mass conservation principle, assuming that 1)the fluid system is in steady state, 2)infiltration rate is constant, and 3)the horizontal transport of water flow rate is constant, a general lumped parameter model of radioisotope concentration-fluid coupled field in groundwater systems is deduced under these conditions, that is, Panel model.Compared with the above mentioned models, this new model is built on a clear physical basis with a definite physical meaning of each parameter, so that it could make accurate interpretations on radioisotope data of the relevant water flow system, and provide more precise mathematical foundation on quantitative analysis and simulation of radioisotope concentration.     

Neighbour field method for population initialization of TSP

It is sensitive to the initial population while the genetic algorithm (GA) is used to solve the traveling salesman problem (TSP). To overcome this problem, the neighbour field method is presented to create initial population. In this method the next city is not the nearest as yet unvisited location but randomly selected from the unvisited cities in neighbour field. Neighbour filed method can extract the local optimal information of adjacent cities, and the constructed population has the diversity character. Comparing to the random initial method, the mean value obtained by the neighbour field method in four standard test instances of TSPLIB improved by 46.3%. The simulation results show the effectiveness of the neighbour field method for creating the initial population.     

发动机用平板型空滤器流动阻力特性分析和改进

为减小平板型空滤器流动阻力以增大进气量,对平板型空滤器流动阻力特性开展了实验研究,获得了空滤器流动阻力随流量变化的规律和阻力构成成分。阻力随流量的增大而加速增大,滤芯阻力约占整个空滤器阻力的一半,入口流量为120 m 3/h时,总阻力为915.3 Pa,滤芯阻力为426.4 Pa。在实验获得滤芯阻力参数的基础上,提出采用多孔介质跃升模型对平板型空滤器内部流场开展三维数值仿真分析,结果表明,仿真结果与实验结果比较吻合,最大误差为5.67%。滤芯阻力同样约占整个阻力的一半,另一半阻力主要为出口处阻力,其余壁面阻力约占15%。最后,在实验和仿真分析的基础上,提出了改进模型并进行了仿真分析。结果表明,改进模型阻力有较大程度的下降,入口流量为120 m 3/h时,总阻力为588.2 Pa,较原始模型下降了32.2%;增大空滤器流通横截面积是减小阻力以增大进气量的有效手段,改进空滤器壁面的平滑性是补充措施。     

组合斜叶桨作用下多相流数值分析

运用Fluent流体分析软件,以菜籽油、辣椒颗粒和花生粒构成的多相流属性为研究对象,结合Eulerian多相流模型,研究了单斜叶桨和组合斜叶桨搅拌作用下的速度场、密度场和各单相体积分数的分布状况。结果表明:当旋转速度为5 rad/s时,在组合斜叶桨作用下,多相流的紊流特性强度增加,整体流动速度提高;近壁区的高密度聚集现象得到明显改善,混合密度均匀化程度提高;各单相的体积分数分布值与初始设定值较为接近,可以实现多相流物料的均匀性混合。计算结果对相应的多相流混合特性机理分析具有一定的理论意义和参考价值。     

Research on the Real -time Simulation of Temperature Field for RCC Gravity Dam

The simulation analysis of temperature field under ideal condition can reflects the rule of true temperature field, but accidental factor during construction process will result in difference of the result. This paper studied the Baise RCC Dam with the distributed optical fiber technology and FEM technology, the numerical results were modified with the testing data and the contrastive curves can be obtained for the testing data,ideal simulation data and real -time simulation data. The results indicate that the modified real - time simulation can reflect the true temperature field ; it may serve as a guide for the temperature control.     

结构消(耗)能元件芯材SN490B本构关系数值模拟

采用消(耗)能元件的结构在遭受地震作用时,元件芯材首先屈服进入塑性阶段,利用其滞回变形消耗地震输入能量,保护主体结构,元件芯材本构关系的数值模拟是对采用消(耗)能元件结构进行抗震分析与设计的基础。为更真实地模拟结构消(耗)能元件芯材在单调和循环荷载下的本构响应,更准确地对采用消(耗)能元件结构进行结构弹塑性地震响应分析,对常用作消(耗)能元件芯材的日本高延性钢材SN490B的单调、循环加载本构及循环骨架曲线进行了数值模拟,包括：采用Esmaeily-Xiao二次流塑性模型模拟材料在单调荷载作用下弹性段、屈服段、强化段和二次流塑段4个阶段;采用混合强化模型模拟材料循环荷载作用下的本构响应,运用大型通用有限元软件ABAQUS结合数值模拟参数对16种不同循环加载制度下的循环加载试验进行模拟,并与试验结果进行对比;采用Ramberg-Osgood模型、无量纲化的Ramberg-Osgood模型及两段式模型模拟循环骨架曲线。研究结果表明：所采用数学模型可以较好地模拟SN490B钢材单调、循环加载本构响应及循环骨架曲线,数值模拟与试验结果拟合较好。     

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.