复杂结构消声器消声特性的数值分析及结构优化

由于复杂结构消声器的内部声场比较复杂，平面波理论无法准确预测其分布，为了计算复杂结构消声器的消声特性，并进一步提高消声器的声学性能，在基本假设的前提下，合理处理进出口及壁面的边界条件。建立消声器内部声场的三维有限元模型，计算消声器的传递损失（TL）。然后，分析了不同的结构参数（隔板位置、内插管位置、进口管位置）对消声器的传递损失的影响，并优化了消声器的结构参数，有效地提高了消声器的消声性能，使得压缩机整机噪声降低了3．2dB，验证了该分析方法的可行性，为复杂结构消声器的设计提供了参考依据。     

冰箱压缩机消声器声学特性的数值分析

分析全封闭往复活塞冰箱压缩机的消声器消声性能。利用软件建立不同结构形状进气消声器的有限元模型,通过导入声学软件进行计算,获得一腔室,两腔室消声器和复杂形状消声器内部声场的声压分布及传递损失。分析结构参数对消声性能的影响。     

内部结构对充水膨胀腔消声器声学性能的影响

结构声耦合效应对充水消声器的声学性能具有重要的影响,利用频域有限元法,结合二维轴对称结构声耦合数值模型分析消声器内部声场,研究消声器内部插入管和环形挡板对膨胀腔水消声器声学特性的影响。数值研究表明：结构声耦合效应会使传递损失的通过频率和峰值频率向低频移动,并压缩消声频段;插入管的结构声耦合效应导致传递损失曲线出现明显峰值,这与插入管的固有模态有关,增加插入管长度时,其一阶固有频率降低,峰值消声频率向低频移动,这有利于低频噪声的衰减;对比双级膨胀腔消声器,挡板会提高低频消声量,挡板厚度会对低频消声量产生明显的影响,但挡板的位置对低频消声量影响不大。     

往复式压缩机吸气消声器的设计与优化

传统内插式吸气消声器腔室之间密封性差，影响消声器消声性能和阻力特性，为解决这一问题，设计一种新结构吸气消声器，通过初步实验对比，证明新吸气消声器腔室密封性好，且具有较好的声学性能和阻力特性，可使压缩机声功率级降低1.87 dB，制冷量提高7.4 W，性能系数提高0.016。为进一步提高新消声器的消声性能，利用声学分析软件LMS Virtual. Lab 进行声学仿真模拟，分析其引流管长度、引流管通流截面宽度、扩张孔位置和出口内插管长度等内部结构参数对传递损失的影响，优化内部结构参数。最终，压缩机声功率级降低2.51 dB，制冷量提高5.63W，性能系数提高0.015。     

汽车消声器声学特性的数值分析与结构改进

利用Sysnoise软件对一汽车消声器进行声场计算,得到消声器的声压分布和传递损失曲线;对消声器结构进行改进,在其内部增设一块隔板和两个穿孔管,并对改进结构进行数值计算。结果表明：低频时声波以平面波的形式向前传播,高频时声波主要以高次谐波的形式向前传播。与原始消声器相比,在600-1 200 Hz的中低频段,以及1 700-1 800 Hz,2 700-2 800 Hz的中高频段,改进消声器的传递损失提高20 dB以上;且在20-3 000 Hz总频段,改进消声器的传递损失平均提高19.8 dB。故改进消声器的消声效果良好。     

往复式压缩机吸气消声器的设计与优化

传统内插式吸气消声器腔室之间密封性差,影响消声器消声性能和阻力特性,为解决这一问题,设计一种新结构吸气消声器,通过初步实验对比,证明新吸气消声器腔室密封性好,且具有较好的声学性能和阻力特性,可使压缩机声功率级降低1.87 dB,制冷量提高7.4 W,性能系数提高0.016。为进一步提高新消声器的消声性能,利用声学分析软件LMS Virtual. Lab 进行声学仿真模拟,分析其引流管长度、引流管通流截面宽度、扩张孔位置和出口内插管长度等内部结构参数对传递损失的影响,优化内部结构参数。最终,压缩机声功率级降低2.51 dB,制冷量提高5.63W,性能系数提高0.015。     

压缩机消声器特性的数值分析与实验研究

建立了压缩机消声器内部声场的三维有限元模型，该模型考虑了压缩机消声器结构和边界条件方面的特殊性，可以计算压缩机消声器的传声损失。同时，将双传声器驻波管测量材料声阻抗的原理，推广到四传声器法测量压缩机消声器的传声损失。通过用单节膨胀消声器的验证，以及在某型压缩机消声器的数值解析和试验分析表明：本文采用的数值计算方法和建立传声损失测试装置是可以应用于压缩机消声器这种复杂对象的。     

同轴抗性消声器声学和阻力特性的数值计算与分析

使用三维数值方法计算同轴膨胀腔消声器和直通穿孔管消声器的声传递损失和流动阻力损失，详细研究了进出口管插入膨胀腔内部长度以及进出口的结构形状对消声器传递损失和阻力损失的影响。采用锥形和指数形进出口管、进出口导流环以及穿孔管均能有效地降低流动阻力损失，而对消声器的低频消声性能影响较小，但对中高频消声性能影响很大。     

挖掘机消声器声学性能的改进

摘 要：首先对某款现有挖掘机排气消声器进行声学分析,采用声学软件LMS Virtual. Lab计算出该消声器各频段的传递损失（TL）。然后分析不同结构参数对消声器消声性能的影响,根据分析结果优化其结构。最后比较分析结果,消声器的消声性能得到进一步的提高,为消声器的优化设计提供参考数据。     

压缩机吸气消声器的声学和阻力特性研究

摘要：吸气消声器主要用于减弱制冷剂吸入压缩部分时产生的进气噪声。针对目前用于往复式压缩机吸气消声器消声频带窄，中高频消声效果不佳的特点，设计出一种多腔室组合的消声器，综合考虑消声器的声学性能和流体特性。在Pro/E中建模完成后，导入ANSYS ICEM CFD中划分网格,在声学仿真软件中分别对最初和新设计后的消声器进行声学仿真。比较两种消声器的传递损失，数值仿真结果显示，新设计的消声器低频消声效果有所降低，中高频消声效果良好，整体消声量提高。最后在 Fluent中仿真消声器的流体性能，以压力损失作为衡量流体性能的标准，得出在设计消声器时，不能为了提高声学性能设计过多的腔室。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.