过程装备与控制工程毕业设计外文翻译英文

广东石油化工学院本科毕业设计：处理量 40 万 Nm3/d 静止式气波制冷机的结构设计及振荡特性分析42外文翻译翻译 1:Proceedings of the ASME 2013 International Mechanical Engineering Congress and ExpositionNovember 15-21, 2013, San Diego, California, USAIMECE2013-63449INFLUENCE OF SKEWING OF CONTACT FACE ON PERFORMANCE OF WAVE ROTOR REFRIGERATORS AND SUPERCHARGERS接触面的倾斜对波转子制冷机和机械增压器性能的影响Dai YuqiangSchool of Chemical Machinery,Dalian University of TechnologyDalian, Liaoning, ChinaLiu FengxiaSchool of Chemical Machinery,Dalian University of TechnologyDalian, Liaoning, ChinaWu JintaoSchool of Chemical Machinery,Dalian University of TechnologyDalian, Liaoning, ChinaWei WeiSchool of Chemical Machinery,Dalian University of TechnologyDalian, Liaoning, ChinaHu Dapeng*School of Chemical Machinery,Dalian University of TechnologyDalian, Liaoning, ChinaLIU XuewuSchool of Chemical Machinery,Dalian University of TechnologyDalian, Liaoning, China英文翻译43ABSTRACTAs a novel generation of rotational gas wave machines, wave rotor machines such as wave rotor refrigerators (WRR) and wave rotor superchargers (WRS) are unsteady flow devices. In their passages two gas streams (with different pressure or even different phases) comes into direct contact can exchange energy due to the movement of shock waves and expansion waves. A detailed study shows that, when rotor channels open to the high pressure port gradually, the contact face in rotor channels inevitably skews, which is always accompanied with reflection of shockwaves. This causes very large energy dissipation and influences adversely on the refrigeration performance of WRR or the supercharging performance of WRS. In this work, factors such as centrifugal forces, Coriolis forces, gradual channel opening and gradual channel closing, etc, which influence the wave transportation and skewing of shock waves and contact faces are studied by means of computational fluid dynamics and experiments. The skewing of contact faces causes uneven distribution of velocity and large local loss. With rotation Mach number smaller than 0.3, the skewing of contact face can be alleviated. To reduce the adverse influence of rotation Mach number, a smaller rotor channel width or higher rotational speed is necessary.The rotation effect plays an important role for the skewing of gas discontinuities. Both the centrifugal and Coriolis forces of wave rotor cannot be ignored with the Rossby number of1.33.5. To reduce the skewing loss of contact face, a lower rotational speed seems necessary. The rotation speed of wave rotors has dialectical influences on the skewing of shock waves and contact faces. The jetting width of high pressure port is the key factor of the gradual opening of rotor channels. A feasible way to reduce skewing losses of gas waves is to optimize the ratio between high pressure port width and channel width. The validation experiments have got at least 35% rise of isentropic efficiency for WRRs.INTRODUCTIONWave rotor technology used for refrigeration and supercharging 1-2 is a new technology based on unsteady flow theory that gas streams with different pressure or 广东石油化工学院本科毕业设计：处理量 40 万 Nm3/d 静止式气波制冷机的结构设计及振荡特性分析44even different phases can exchange energy due to the movement of shock waves and expansion waves 3-8. There are two typical wave rotor machines used for different purposes: wave rotor refrigerators (WRRs), as shown in FIG.1, and wave rotor superchargers (WRS). The WRRs are often used for expansion refrigeration of pressured natural gas, and the WRSs used for R718 vapor compression refrigeration system can efficiently reduce the pressure ratio of R718 compressors. Both of these two wave rotor devices are developed in the lab of Dalian University of Technology 9. While numerical analyses of unsteady flow in pulse tubes of WRR have been performed extensively 10-12, less detailed analysis on the impact of contact face skewing in rotor channels of WRR has been documented, especially for condensation wave rotor accompanied with complex non-equilibrium thermodynamic phenomena occasionally. This research presents a study on the causes and impacts of skewing of contact faces in channels by means of computational fluid dynamics analysis and experiments. Fig.1 The original wave rotor refrigerator and the experimental arrangementCAUSES OF SKEWING OF CONTACT FACE IN ROTOR CHANNELS1 Gradual Opening Process of Rotor ChannelsRegardless of the rotation factors, the gradual opening and closing processes of rotor channels play important roles in the skewing of contact faces. A 2-dimensional CFD model has been built by using Euler equations and Roe-FDS discretization scheme with min-mod limiter to accurately capture the strong discontinuities such as 英文翻译45contact faces and shocks in rotor channels. With dynamic coordination located on wave rotor channels, the convected translational velocity is R with no centrifugal or Coriolis accelerations. When a rotor channel gradually opens to the high pressure(HP) inlet port, one portion of the channels is exposed in gas streams while the others are closed by walls, which can cause boundary layer separations. In our work, two aspects of static analysis (with zero convected velocity) and dynamic analysis with constant nonzero convected velocity are performed. (1)Zero convected velocityTable 1 shows the evolution of temperature (a) and pressure (b) fields in a rotor channel with no convected velocity at an expansion ratio of pr=303kPa/101kPa, and the time interval of each frame is 0.04 ms. All the contact discontinuity ,oblique incident shock waves, and their reflections as well as refractions have been captured precisely.Though there is a small distortion of the contact face when intersected with reflected shock waves, the intersection of reflection shock wave or compressional wave with the contact area is a typical irreversible thermodynamic process, which can 广东石油化工学院本科毕业设计：处理量 40 万 Nm3/d 静止式气波制冷机的结构设计及振荡特性分析46affect gas wave running performances notably . The analysis also indicates that the separated vortex pair formed near the trailing and leading edge of the rotor channel distorts the contact face. The uneven distribution of velocity will cause a significant momentum transfer, by which a large local loss is caused. The increased heat-exchange area between the driving and driven gas streams adversely affects the performance of thermo separations 13.(2)Constant convected velocityThere is an accumulative effect of the skewing of contact faces when rotor channels open gradually. The connected area between HP port and rotor channel determines the flow path as well as the reflection behavior of shock waves and at the same time affects the contact face distortion. The changing rate of the connected area depends on the relative sliding velocity, or the convected velocity Ve . The longer the channel is open, the larger the accumulation effect is achieved. Table 2 shows the temperature contours in a rotor channel with different convected velocities at an expansion ratio of pr=303kPa/101kPa. The skewing of the contact face can be found evidently from the temperature contour, because there is a 英文翻译47large temperature difference across the contact face. The numerical results show that the contact faces skew slightly with small ratio of channel width e and convected velocities e V . A rotational Mach number o M defines the dimension less time of gradual opening of the channels：0= 120(+0) (1)where a is the stagnation sound speed. At the specific structural parameters and boudary conditions, the skewing of contact face depends on the rotational Mach number: For cases with rotational Mach number lower than 0.3, the interaction of contact face and reflective shockwave becomes weak, and at the same time, the skewing of contact face is alleviated14.(3) Centrifugal forces or Coriolis forcesAs shown in Fig.2, with rotational channels under a moving coordinate system, a non-inertial system of coordinates is established. The relative velocity and acceleration are both in x direction.When rotating in a constant angular velocity , the convected acceleration is in n direction. = =1222=2The Coriolis acceleration c a is non-zero. So a velocity circulation transport equation for thermal perfect gases can be established by：广东石油化工学院本科毕业设计：处理量 40 万 Nm3/d 静止式气波制冷机的结构设计及振荡特性分析48=2() (2)According to Helmhotz theorem, there is a corresponding relation of velocity circulation and vortex strength. There are two main reasons cause the gerneration of vortices in rotor channels:Except for isentropic, adiabatic, isovolumetric, or polytropic processes, the compressible gas is not a barotropic fluid. The gradient of specific volume does not coincide with that of pressure, . In the fields without gas waves, the 0baroclinic vortices are inevitably generated. The Coriolis forces generate vortices, for ()0A Rossby number is introduced to describe the influence of Coriolis force:0=| =20=0 (3), where l0 is the length of rotor passage. When Coriolis force is much smaller than inertia force, the rotational effect can be ignored. Table 3 shows some results of Rossby numbers for l0=200mm at different initial pressure ratios. The Coriolis force is comparable to inertia force, so the rotational effect is an important cause of the skewing of contact face. Figure3 shows the 3-dimension contours of pressure and temperature for the pressure ratio of 303kPa/101kPa at 0.6ms. Different from 2D results, there exists a pressure gradient near the contact face, hence the rotational effect cannot be ignored. The pressure change exerts adverse influence on the stability of contact face. When the rotor channel rotates at a constant angular velocity, the pressure balances Coriolis force in the tangential direction. The pressure gradually decreases from the leading edge to the trailing edge of the rotor channel. It follows that the 英文翻译49relative velocity distributes unevenly in the direction of rotation.SOLUTIONSTO THE ADVERSE INFLUENCE OF CONTACT FACE SKEWINGThe skewing of contact face inevitably occurs because of the accumulation effect of gradual opening of channels and the rotational effect. To eliminate the gradual opening effect, a high rotation velocity is preferred, which, however, could cause a large Coriolis force.A feasible technical solution to take into account the small rotational Mach number and large Rossby number is to improve the width ratio of HP port and channel width. The width of HP Port has an important influence on the performances 广东石油化工学院本科毕业设计：处理量 40 万 Nm3/d 静止式气波制冷机的结构设计及振荡特性分析50of the wave rotor devices. Besides influencing the skewing of contact face and shockwaves, the HP port has the highest pressure and is prone to leakage. Figure 4 shows some of the experimental results (Fig.1shows the experimental arrangement, a detailed description can be found in reference 15 ) for different widths of HP port (10,16 and 22mm), at the expansion ratios of 2.0, 3.0 and 4.0,respectively. Both the supercharging efficiency and peak temperature decline with the refrigeration efficiency. Futher more, both super-charging and expansion efficiencies increase with the width of high pressure port. This verifies the requirements of high Rossby number and low rotational Mach number from CFD analysis. By increasing the width of HP port, we have got about 5 percent enhancement of the refrigeration efficiency, and reached about 70% in DUT lab. CONCLUSIONSIn the present study, a detailed discussion on the generation and influences on the skewing of contact faces in wave rotor advices like WRRs and WRSs is presented. The contact face in rotor channels inevitably skews, due to the baroclinic nature of compressible gas streams.For cases with rotation Mach number lower than 0.3 or Rossby number much larger than unit, the skewing of contact faces could be alleviated. Unfortunately, the optimal rotation speed of rotor channels is not found yet to meet the two requirements easily. A feasible way to alleviate the skewing losses of gas waves is to improve the ratio between HP port width and channel width. The validation experiments have got a rise of isentropic efficiency at least 35% for WRRs.ACKNOWLEDGMENTSThis present work was supported by grants from the National Natural Science Foundation of China project(51106017) and from National High Technology Research and Development Program of China (2006AA05Z216). REFERENCES1 Yuqiang Dai, Meixia Ding, Dapeng Hu, et al., 2010, “Wave Rotors Used for Refrigeration Technology,”Journal of Dalian University of Technology, Vol.50, pp.888-895.英文翻译512 Yuqiang Dai, Dapeng Hu, Meixia Ding,2009, “Study onwave rotor refrigerators ,”Chem. Eng. China, Vol.3,pp.83-87.3 Pezhman Akbari, Amir A. Kharazi, Norbert Muller, 2003,“Utilizing wave rotor technology to enhance the turbocom pression in power and refrigeration cycles,”ASME International Mechanical Engineering Congress & Exposition,IMECE2003-44222.4 Gerard E. Welch and Rodrick V. 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