A Numerical Analysis of the Forced Convection Condensation of Saturated Vapor Flowing Axially Outside a Horizontal Tube

ＡＮｕｍｅｒｉｃａｌＡｎａｌｙｓｉｓｏｆｔｈｅＦｏｒｃｅｄＣｏｎｖｅｃｔｉｏｎＣｏｎｄｅｎｓａｔｉｏｎｏｆＳａｔｕｒａｔｅｄＶａｐｏｒＦｌｏｗｉｎｇＡｘｉａｌｌｙＯｕｔｓｉｄｅａＨｏｒｉｚｏｎｔａｌＴｕｂｅ￥ＷｅｉｚｈｏｎｇＬｉ，ＷｅｉｃｈｅｎｇＷａ...     

Ignition and Extinction of Monopropellant Droplet with Lewis Number Different from Unity

ＩｇｎｉｔｉｏｎａｎｄＥｘｔｉｎｃｔｉｏｎｏｆＭｏｎｏｐｒｏｐｅｌｌａｎｔＤｒｏｐｌｅｔｗｉｔｈＬｅｗｉｓＮｕｍｂｅｒＤｉｆｆｅｒｅｎｔｆｒｏｍＵｎｉｔｙ￥ＦｅｒｎａｎｄｏＦ．Ｆａｃｈｉｎｉ（ＩｎｓｔｉｔｕｔｏＮａｃｉｏｎａｌｄｅＰｅｓｑｕｉｓａｓＥ...     

The Study of the Damage Laws of Pool Fires

ＴｈｅＳｔｕｄｙｏｆｔｈｅＤａｍａｇｅＬａｗｓｏｆＰｏｏｌＦｉｒｅｓ￥ＹｕＤｅｍｉｎｇ；ＦｅｎｇＣｈａｎｇｇｅｎ；ＺｅｎｇＱｉｎｇｘｕａｎ；ＧｕｏＸｉｎｙａ（Ｍｅｃｈａｎｉｃｓ＆ＥｎｇｉｎｅｅｒｉｎｇＤｅｐａｒｔｍｅｎｔ，ＢｅｉｊｉｎｇＩｎｓｔｉｔｕ...     

Comparison of a Reaction Front Model and a Finite Difference Model for the Simulation of Solid Absorption Process

ＣｏｍｐａｒｉｓｏｎｏｆａＲｅａｃｔｉｏｎＦｒｏｎｔＭｏｄｅｌａｎｄａＦｉｎｉｔｅＤｉｆｆｅｒｅｎｃｅＭｏｄｅｌｆｏｒｔｈｅＳｉｍｕｌａｔｉｏｎｏｆＳｏｌｉｄＡｂｓｏｒｐｔｉｏｎＰｒｏｃｅｓｓ￥ＺｉｋａｎｇＷｕ；ＡｒｎｅＪａｋｏｂｓｅｎ；Ｘｉｕｇａｎ...     

Numerical Solution of Flow Field Diagnosis Problem in Multistage Axial Compressors

Ｎｕｍｅｒｉｃａｌ　Ｓｏｌｕｔｉｏｎ　ｏｆ　Ｆｌｏｗ　Ｆｉｅｌｄ　Ｄｉａｇｎｏｓｉｓ　Ｐｒｏｂｌｅｍ　ｉｎ　Ｍｕｌｔｉｓｔａｇｅ　Ａｘｉａｌ　ＣｏｍｐｒｅｓｓｏｒｓＮｕｍｅｒｉｃａｌＳｏｌｕｔｉｏｎｏｆＦｌｏｗＦｉｅｌｄＤｉａｇｎｏｓｉｓＰｒｏｂｌｅ...     

Experimental Study on Heat Transfer and Pressure Drop Characteristics of Four Types of Plate Fin－and－TUbe Heat Exchanger Surfaces

ＥｘｐｅｒｉｍｅｎｔａｌＳｔｕｄｙｏｎＨｅａｔＴｒａｎｓｆｅｒａｎｄＰｒｅｓｓｕｒｅＤｒｏｐＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＦｏｕｒＴｙｐｅｓｏｆＰｌａｔｅＦｉｎ－ａｎｄ－ＴＵｂｅＨｅａｔＥｘｃｈａｎｇｅｒＳｕｒｆａｃｅｓ￥Ｈ．Ｊ．Ｋａｎｇ；Ｗ．Ｌ...     

Controlling Mechanism and Resulting Spray Characteristics of Injection of Fuel Containing Dissolved Gas

ＣｏｎｔｒｏｌｌｉｎｇＭｅｃｈａｎｉｓｍaｎｄＲｅｓｕｌｔｉｎｇＳｐｒａｙＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＩｎｊｅｃｔｉｏｎｏｆＦｕｅｌＣｏｎｔａｉｎｉｎｇ　ＤｉｓｓｏｌｖｅｄＧａｓＨｕａｎｇＺｈｅｎ（ＤｅｐａｒｔｍｅｎｔｏｆＰｏｗｅｒＭａｃｈｉｎ?..     

Influence of Heating Rate on the Onset of Oscillation in Liquid Bridge of Half Floating Zone

ＩｎｆｌｕｅｎｃｅｏｆＨｅａｔｉｎｇＲａｔｅｏｎｔｈｅＯｎｓｅｔｏｆＯｓｃｉｌｌａｔｉｏｎｉｎＬｉｑｕｉｄＢｒｉｄｇｅｏｆＨａｌｆＦｌｏａｔｉｎｇＺｏｎｅ￥Ｊｉｎｇ－ＣｈｅｎｇＸｉｅ；Ｗｅｎ－ＲｕｉＨｕ（ＩｎｓｔｉｔｕｔｅｏｆＭｅｃｈａｎｉｃｓ，Ｃｈ...     

Numerical Simulation of Multistory Building Fire with Zone-Modeling Method

ＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＭｕｌｔｉｓｔｏｒｙＢｕｉｌｄｉｎｇＦｉｒｅｗｉｔｈＺｏｎｅ－ＭｏｄｅｌｉｎｇＭｅｔｈｏｄＦｕＺｈｕｍａｎ；ＦａｎＷｅｉｃｈｅｎｇ（ＳｔａｔｅＫｅｙＬａｂｏｆＦｉｒｅＳｃｉｅｎｃｅ，ＵｎｉｖｅｒｓｉｔｙｏｆＳ...     

Numerical Simulation of 3—D Temperature Distribution of the Flame Tube of the Combustion Chamber with Air Film COoling

ＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆ３－ＤＴｅｍｐｅｒａｔｕｒｅＤｉｓｔｒｉｂｕｔｉｏｎｏｆｔｈｅＦｌａｍｅＴｕｂｅｏｆｔｈｅＣｏｍｂｕｓｔｉｏｎＣｈａｍｂｅｒｗｉｔｈＡｉｒＦｉｌｍＣｏｏｌｉｎｇＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆ３－Ｄ...     

Effect of inlet guide vanes on the performance of small axial flow fan

Effects of the inlet guide vanes on the static characteristics, aerodynamic noise and internal flow characteristics of a small axial flow fan are studied in this work. The inlet guide vanes with different outlet angle are designed,which are mounted on the casing and located at the upstream of the impeller of the prototype fan. Both steady and unsteady flow simulations are performed. The steady flow is simulated by the calculations of Navier-Stokes equations coupled with RNG k-epsilon turbulence model, while the unsteady flow is computed with large eddy simulation. According to the theoretical analysis, the inlet guide vanes with outlet angle of 60° are regarded as the optimal inlet guide vanes. The static characteristic experiment is carried out in a standard test rig and the aerodynamic noise is tested in a semi-anechoic room. Then, performances of the fan with optimal inlet guide vanes are compared with those of the prototype fan. The results show that there is reasonable agreement between the simulation results and the experimental data. It is found that the static characteristics of small axial flow fan is improved obviously after installing the optimal inlet guide vanes. Meanwhile, the optimal inlet guide vanes have effect on reducing noise at the near field, but have little effect on the noise at the far field.     

Study of unsteady flow simulation of backward impeller with non-uniform casing

The flow characteristics of the centrifugal fans with different blade outlet angles are basically discussed on steady and unsteady simulations for a rectangular casing fan. The blade outlet angles of the impellers are 35° and 25° respectively. The unsteady flow behavior in the passage of the impeller 35° is quite different from that in the steady flow behavior. The large flow separation occurs in the steady flow field and unsteady flow field of the impeller 35°, the flow distribution in the circumferential direction varies remarkably and the flow separation on the blade occurs only at the back region of the fan; but the steady flow behavior in the impeller 25° is almost consistent with the unsteady flow behavior, the flow distribution of the circumferential direction doesn't vary much and the flow separation on the blade hardly occurs. When the circumferential variation of the flow in the impeller is large, the steady flow simulation is not coincident to the unsteady flow simulation.     

Effect of inlet box on performance of axial flow fans

Numerical investigations on 3D flow fields in an axial flow fan with and without an inlet box have been extensively conducted, focusing on the variation of fan performance caused by the internal flow fields and the velocity evenness at the exit of the inlet box. It is interesting to find that although the inlet box is well designed in accordance with basic design principles, there is a flow separation region in it. Furthermore, this flow separation and the resulting uneven velocity distribution at the exit lead to some decrease in the efficiency and an increase in the total pressure rise of the fan. This research shows that the inlet box needs further improvement and such a check on the flow fields is of value for the design of inlet boxes.     

基于内部流场分析的离心风机改型设计

本文以某型离心风机为基础,依靠数值模拟的方法,基于对风机内部流场的分析,对其进行优化改型设计。主要分为三个方面：其一,将叶轮的直叶片改型为前掠正弯叶片,控制端区低能流体堆积,抑止叶栅流道分离流动的发生;其二,根据弯掠优化得到的叶轮设计改型风机机壳,以适应弯掠叶轮的出口气动条件;并根据弯掠叶轮与改型机壳内部流动的分析,对叶轮采取根切的优化方法,保持风机全压和流量在合理的大小。得到的优化设计风机,在保持全压和流量基本与原型相等的条件下,效率提高5%以上。     

Effect of inlet box on performance of axial flow fans

Numerical investigations on 3D flow fields in an axial flow fan with and without an inlet box have been extensively conducted, focusing on the variation of fan performance caused by the internal flow fields and the velocity evenness at the exit of the inlet box. It is interesting to find that although the inlet box is well designed in accordance with basic design principles, there is a flow separation region in it. Furthermore, this flow separation and the resulting uneven velocity distribution at the exit lead to some decrease in the efficiency and an increase in the total pressure rise of the fan. This research shows that the inlet box needs further improvement and such a check on the flow fields is of value for the design of inlet boxes. __________ Translated from Journal of Engineering Thermophysics, 2007, 28 (Suppl.1): 161–164 [译自: 工程热物理学报]     

Numerical simulation of flow in centrifugal pump with complex impeller

Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model, three dimensional turbulent flow fields in centrifugal pump with long-mid-short blade complex impeller are calculated and analyzed numerically. The relative velocity and pressure distributions in the flowpart are obtained. It is found that the flow in the passage of the complex impeller is unsymmetrical due to the joint action between volute and impeller. The back-flow region is at inlet of long-blade suction side, near middle part of long-blade pressure side and outlet of short-blade suction side. The flow near volute throat is affected greatly by volute. The relative velocity is large and it is easy to bring back flow at outlet of the complex impeller near volute throat. The static and total pressure rise uniformly from inlet to outlet in the impeller. At impeller outlet, the pressure periodically decreases from pressure side to suction side, and then the static pressure sharply rise near the throat. The experimental results show that the back flow in the impeller has an important influence on the performance of pump.     

Computational Studies of Flow through Cross Flow Fans-Effect of Blade Geometry

Introduction Cross Flow Fan (CFF) is a turbomachine, which operates fundamentally in a different way compared to axial or centrifugal type of machines. Flow enters the full width of impeller through one sector and leaves through another sector. The flow structure inside the impeller can be divided into two regions: (a) eccentric vortex or recirculation region having closed streamlines (b) through flow region consisting of inflow and outflow of the fluid. The main components of CFF are imp…     

向心透平内部流动的研究

对向心透平内部的流动进行了实验与数值的研究。蜗壳内采用单斜丝热线在同一位置旋转．在三个不同的方位测量后拟合计算得到气流的三维速度。在某些特征位置与数值结果的对比，说明了数值结果的可靠性与局限性。对导叶内的流动模拟，确定了入口角度对导叶内二次流动的影响。对叶轮内流动模拟，说明了叶顶泄漏流对主流的作用，以及叶轮内部壁角涡的形成与发展。这些工作对向心透平内部流动的认识提供了参考。     

Investigation on inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet

The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method, mainly focused on three issues including the amounts and differences of the inlet recirculation in different working conditions, the circumferential non-uniform distributions of the inlet recirculation, the recirculation velocity distributions of the upstream slot of the rear impeller. The results show that there are some differences between the recirculation of the front impeller and that of the rear impeller in whole working conditions. In design speed, the recirculation flow rate of the rear impeller is larger than that of the front impeller in the large flow range, but in the small flow range, the recirculation flow rate of the rear impeller is smaller than that of the front impeller. In different working conditions, the recirculation velocity distributions of the front and rear impeller are non-uniform along the circumferential direction and their non-uniform extents are quite different. The circumferential non-uniform extent of the recirculation velocity varies with the working conditions change. The circumferential non-uniform extent of the recirculation velocity of front impeller and its distribution are determined by the static pressure distribution of the front impeller, but that of the rear impeller is decided by the coupling effects of the inlet flow distortion of the rear impeller, the circumferential unsymmetrical distribution of the upstream slot and the asymmetric structure of the volute. In the design flow and small flow conditions, the recirculation velocities at different circumferential positions of the mean line of the upstream slot cross-section of the rear impeller are quite different, and the recirculation velocities distribution forms at both sides of the mean line are different. The recirculation velocity distributions in the cross-section of the upstream slot depend on the static pressure distributions in the intake duct.     

Unsteady behavior of leading-edge vortex and diffuser stall in a centrifugal compressor with vaned diffuser

The characteristics of a rotating stall of an impeller and diffuser and the evolution of a vortex generated at the diffuser leading-edge (i.e., the leading-edge vortex (LEV)) in a centrifugal compressor were investigated by experiments and numerical analysis. The results of the experiments revealed that both the impeller and diffuser rotating stalls occurred at 55 and 25 Hz during off-design flow operation. For both, stall cells existed only on the shroud side of the flow passages, which is very close to the source location of the LEV. According to the CFD results, the LEV is made up of multiple vortices. The LEV is a combination of a separated vortex near the leading- edge and a longitudinal vortex generated by the extended tip-leakage flow from the impeller. Therefore, the LEV is generated by the accumulation of vorticity caused by the velocity gradient of the impeller discharge flow. In partial-flow operation, the spanwise extent and the position of the LEV origin are temporarily transmuted. The LEV develops with a drop in the velocity in the diffuser passage and forms a significant blockage within the diffuser passage. Therefore, the LEV may be regarded as being one of the causes of a diffuser stall in a centrifugal compressor.