空调用多翼离心风机气动噪声的仿真研究

空调气动噪声是影响室内舒适性的重要因素,本文对空调用多翼离心风机的非定常流场及噪声特性进行了数值分析。利用CFD软件SC/Tetra模拟非稳态流场,并采用Ffowcs-Williams and Hawkings模型计算气动声压。对某空调用多翼离心风机的噪声进行了预测,所测得的离散噪声和宽频噪声均与测量值吻合良好,为空调器空气流场的优化设计和降低空调器风机空气流动噪声的研究提供了有效工具。

The Development of Hi-Speed Punching System Using A Couple of Rotating Bodies

Punched steel sheets (metal sheets or foils) as thi n as 0.1mm are quite useful in the field of filters and various precision instrume nts. Thus, we have to develop more accurate and speedy techniques for punching t hin sheets. The traditional punching method uses an up-down pressing motion of a punch or a die on a strip of metal. The efficiency of this method is determine d by the speed of the motion. In the case of punching a sequence of tiny holes w ith a few millimeters’ interval, the speed of feeding a strip of metal to the p unching machine cannot exceed only a couple of meters per minute. We have de veloped a new technique for punching tiny holes with a pair of rotating bodies i n order to increase the feeding speed up to 100 meters per minute. Our proposed technique is shown in Fig.1 where the female tool has a round blade and the male tool has an M-shape boss. In addition, the setting of two tools i s alternating. The interference between them cannot occur because the clearance between the front and the back edge of the male tool and the female tool in the rotating direction becomes infinite in this configuration. An appropriate cleara nce is given for the thickness of the sheet between the side edge of the male to ol and the female tool. The punching itself is done by shearing. The side edge o f the male tool does contact with the female tool, but they cannot be interferin g. Our technique has another advantage to the traditional up-down pressing mach ine where the stamped out chips are hard to be discharged. It is quite easy in o ur proposed technique. Fig.2, 3 show a sample of punched material [TPP116A,+39mm88mm,Y,PZ#]Fig.1 The configuration of the punching parts using the sequential punching system.[TPP116B,+43mm155mm,X,BP#]Fig.2 A sample of punched material using the continuous punch ing lineFig.3 A exterior picture of a piece of punched steel foil(coi l) using the continuous punching For our developed high speed punching system, it is shown for (1) the configurat ion of punching tool and the punching mechanism, (2) the influence of male shape on punched hole quality, (3) the outline of continuous punching system, (4) the relation between punching speed and accuracy of hole pitch and hole dimensi on, (5) the mechanical property of punched metal sheet and (6) capability of hig her punching.

Hybrid Friction Stir Welding of High-carbon Steel

A high-carbon steel joint,SK5（0.84 wt% C）,was successfully welded by friction stir welding（FSW）,both without and with a gas torch,in order to control the cooling rate during welding.After welding,the weld zone comprised gray and black regions,corresponding to microstructural variation：a martensite structure and a duplex structure of ferrite and cementite,respectively.The volume fraction of the martensite structure and the Vickers hardness in the welds were decreased with the using of the gas torch,which was related with the lower cooling rate.

High Strength Steel Plates for Large Container Ships

Heavy thickness steel plates with a good combination of strength,toughness and weldability have been demanded for building of large container ships.High strength steel plates with heavy gauge of EH36,EH40 and EH47 grades were developed by optimizing chemical compositions and TMCP process parameters.Micro alloying elements of Ti and Nb were added to the three steel grades for enhancing the strength and toughness of base plates.The strength of base plates of the EH47 grade was further enhanced with the help of the increased amount of substitutional solid solutes,such as manganese,copper,nickel,or chromium.EH36 steel plates for high heat input over 550 kJ/cm were manufactured by improving thermal stability of TiN particles for better weld heat-affected zone toughness.Thermally stabilized TiN particles effectively suppress grain growth at weld heat-affected zone,leading to better toughness.These steel plates showed excellent mechanical properties of base plates and welded joints.