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《制冷与空调(北京)》2019,(3)
螺杆制冷压缩机的振动噪声问题是目前的研究热点,本文介绍了螺杆制冷压缩机振动噪声产生的机理,从机械振动噪声和气流脉动两方面总结了若干主流减振降噪方法和技术。螺杆制冷压缩机振动噪声的进一步改善,主要应在转子材料、转子型线、气流脉动抑制、主动振动控制和有源降噪等方面深入研究。 相似文献
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某型号冰箱压缩机运转时存在噪声值偏大问题。为降低噪声,采用对比测试分析法对五种不同工况下的样机进行了噪声频谱测试与声源识别,明确了气动噪声为主要声源,机械噪声为次要声源,而电磁噪声对整机影响较小。气动噪声为排气管内高速高压气体产生周期性气流脉动和气流喷注噪声,呈宽频分布特征,峰值频率为2000Hz,对应噪声值为49.3dB(A)。此外,压缩机激振频率引发排气管低频振动。提出了设置排气管消声器与安装弯管减振弹簧等改进措施,与改进前测试结果比较,改进后整机噪声下降了1.83dB(A)。 相似文献
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压缩机运行转速越高,其产生的噪声越大,改善制冷压缩机气流脉动诱发的排气噪声衰减变得越来越重要,其中,变频双螺杆制冷压缩机的需求尤其明显。为有效改善变频双螺杆制冷压缩机排气气流脉动诱发的气动噪声,本文研究了一种基于赫姆霍兹共振器的宽频带穿孔板气流脉动衰减器。建立了气流脉动衰减器的声学设计方法,根据测量的两相流声速,实现了共振频率的计算,通过实验测量结果对计算结果进行了验证,并进一步分析了压缩机运行转速对其衰减性能的影响。研究结果表明:油气两相流声速随着运行转速上升而增加,运行转速从3 000 rpm上升到5 100 rpm,油气两相流声速从142.8 m/s上升到144.6 m/s,增加1%。对比理论计算和实验测量结果,宽频带穿孔板气流脉动衰减器的衰减频率基本吻合,衰减效果趋势一致,在运行转速3 000~4 500 rpm区间,气流脉动基频排气噪声值下降3.0 d B(A)以上;在排气噪声较大的高转速运行区间4 500~5 100 rpm,排气噪声值下降5.0 d B(A)到7.5 d B(A)。应用宽频带穿孔板气流脉动衰减器后,变频双螺杆压缩机高转速下气流脉动基频的噪声值分别为85.8 d B(A)(4 800 rpm)和84.2 d B(A)(5 100 rpm),比相同制冷量低转速下定频压缩机3 000 rpm时噪声减小2.0 d B(A)以上,有效解决变频双螺杆压缩机气流脉动诱发的排气噪声问题。 相似文献
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采用在压缩机吸气端设置消声器的方法降低冰箱在运行过程中制冷压缩机所产生的噪声。采用Creo 3.0对压缩机吸气消声器进行三维建模,使用CATIA划分网格,运用LMS.Virtual.Lab对内腔无导流管的消声器进行声学传递损失计算。针对无导流管的消声器在压缩机主要噪声频段消声效果不稳定的特征,设计内腔方形导流管、内腔圆形导流管两种消声器,与无导流管消声器进行对比,发现导流管可以提高消声器的消声性能,而导流管的形状也影响消声器的消声性能,圆形导流管比方形导流管有更好的降噪效果。最后通过压缩机整体噪声测试实验,验证上述不同结构消声器在压缩机稳定工况时降噪的对比效果,得出圆形导流管消声器对于整机辐射噪声消声效果好的结论。 相似文献
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旋转式压缩机广泛应用于家用空调器,是制冷系统的动力源,也是空调系统中主要噪声源。本文针对双缸压缩机吸气噪声,建立CFD模型,通过数值计算得到单、双吸气方式的质量流率。在此基础上,建立不同单、双吸气方式分液器声学FEM模型,分析不同分液器的单极子吸气噪声,并与测试结果进行对比。结果表明,单吸气方式在降低双缸压缩机单极子吸气噪声方面较双吸气方式具有一定优势,在本例中,分液器吸气噪声降低2 dB(A)以上。 相似文献
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滚动转子式压缩机吸气压力脉动对其制冷剂吸入量有着重要的影响。本文以某种型号的滚动转子式压缩机为研究对象,借助流体仿真软件Star-CD,模拟压缩机旋转压缩过程,得到汽缸吸气口的压力脉动规律,并同NI试验测试的压力脉动进行对比,发现两者结果较为吻合;并通过仿真对比吸气管路对压缩机吸气压力和吸气量的影响。 相似文献
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一、往复式压缩机噪声分析 压缩机噪声由多个声源通过机器外壁幅射出来。整机噪声由下述各部分噪声组成。 1.进气噪声 压缩机在进气口间歇地吸气产生压力脉动,形成进气噪声。它与负荷,进气阀门的尺寸、气门通路和调速的结构等因素有关,其噪声的基频由转速决定,一般往复式压缩机的转速n=400~800转/分, 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
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. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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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. 相似文献
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Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di... 相似文献
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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.…… 相似文献
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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. 相似文献
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Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
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. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
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 ... 相似文献