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Study for the Gas Flow through a Critical Nozzle

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Journal of Thermal Science 2003年第3期12卷 250-254,259页

作者： Jae-Hyung k.m heuy-dong k.m Shigeru matsuo Toshiaki Setoguchi School of mechanical Engineering Andong National UniversityAndong 760-749 KoreaSchool of Mechanical Engineering Andong National UniversityAndong 760-749 KoreaDepartment of Mechanical Engineering Saga University1 Honjo Saga 840-8502 JapanDepartment of Mechanical Engineering Saga University1 Honjo Saga 840-8502 Japan

In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through a critical nozzle. The Reynolds number effects are investigated with several nozzles with different throat diameter. Diffuser angle is varied to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that diffuser angle affects the critical pressure ratio.

关键词： compressible flow choke boundary layer critical pressure ratio discharge coefficient

A Study of the Impulse Wave Discharged from the Exits of Two Parallel Tubes

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Journal of Thermal Science 2003年第4期12卷 332-336,356页

作者： Yong-Hun kweon heuy-dong k.m Toshiaki Setoguchi Toshiyuki Aoki School of mechanical Engineering Andong National University Andong 760-749 KoreaSchool of Mechanical Engineering Andong National University Andong 760-749 KoreaDepartment of Mechanical Engineering Saga University Honjo Saga 840-8502 JapanDepartment of Energy Science and Engineering Kyushu University Kasuga Fukuoka 816-8580 Japan

The twin impulse wave leads to very complicated flow fields, such as mach stem, spherical waves, and vortex ring. The twin impulse wave discharged from the exits of the two tubes placed in parallel is investigated to understand the detailed flow physics associated with the twin impulse wave, compared with those in a single impulse wave. In the current study, the merging phenomena and propagation characteristics of the impulse waves are investigated using a shock tube experiment and by numerical computations. The Harten-Yee''s total variation diminishing (TVD) scheme is used to solve the unsteady two-dimensional compressible Euler equations. The mach number ms of incident shock wave is changed below 1.5 and the distance between two-parallel tubes, L/d, is changed from 1.2 to 4.0. In the shock tube experiment, the twin impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. The results obtained show that on the symmetric axis between two-parallel tubes, the peak pressure produced by the twin impulse waves and its location strongly depend upon the distance between two-parallel tubes, L/d and the incident shock.mach number, ms. The predicted Schlieren images represent the measured twin-impulse wave with a good accuracy.

关键词： compressible flow unsteady flow impulse wave shock wave shock tube.

A study on characteristics of shock train inside a shock tube

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Theoretical & Applied mechanics Letters 2017年第6期7卷 366-371页

作者： dong Wook k.m Tae Ho k.m heuy dong k.m Department of mechanical Engineering Andong National UniversityAndongKorea

Shock tubes are devices which are used in the investigation of high speed and high temperature flow of compressible gas. lnside a shock tube, the interaction between the reflected shock wave and boundary layer leads to a complex flow phenomenon. Initially a normal shock wave is formed in the shock tube which migrates toward the closed end of the tube and that in turn leads to the reflection of shock. Due to the boundary layer interaction with the reflected shock, the bifurcation of shock wave takes place. The bifurcated shock wave then approaches the contact surface and shock train is generated. Till date only a few studies have been conducted to investigate this shock train phenomenon inside the shock tube. For the present study a computational fluid dynamics （CFD） analysis has been performed on a two dimensional axi-symmetric model of a shock tube using unsteady, compressible Navier-Stokes equations. In order to investigate the detailed characteristics of shock train, parametric studies have been performed by varying different parameters such as the shock tube length, diameter, pressure ratio used inside the shock tube.

关键词： Shock tube Reflected shock wave Boundary layer separation Contact surface Shock train

Influence of Tip End-plate on Noise of Small Axial Fan

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Journal of Thermal Science 2017年第1期26卷 30-37页

作者： mAO Hongya WANG Yanping LIN Peifeng JIN Yingzi Toshiaki Setoguchi heuy dong k.m key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech University Department of mechanical Engineering Saga University School of mechanical Engineering Andong National University

In this work, tip end-plate is used to improve the noise performance of small axial fans. Both numerical simulations and experimental methods were adopted to study the fluid flow and noise level of axial fans. Four modified models and the prototype are simulated. Influences of tip end-plate on static characteristics, internal flow field and noise of small axial fans are analyzed. The results show that on basis of the prototype, the model with the tip end-plate of 2 mm width and changed length achieved best noise performance. The overall sound pressure level of the model with the tip end-plate of 2 mm width and changed length is 2.4 dB less than that of the prototype at the monitoring point in specified far field. It is found that the mechanism of noise reduction is due to the decrease of vorticity variation on the surface of blades caused by the tip end-plate. Compared with the prototype, the static pressure of the model with the tip end-plate of 2 mm width and changed length at design flow rate decreases by 2 Pa and the efficiency decreases by 0.8%. It is concluded that the method of adding tip end-plate to impeller blades has a positive influence on reducing noise, but it may diminish the static characteristics of small axial fan to some extent. © 2017, Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag Berlin Heidelberg.

关键词： Axial flow Fans Flow of fluids Noise abatement Numerical methods

A Study of the Gas Flow through Air Jet Loom

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Journal of Thermal Science 2007年第2期16卷 159-163页

作者： heuy-dong k.m Chae-min Lim Ho-Joon Lee Doo-Hwan Chun School of mechanical Engineering Andong National University388Songcheon-dongAndong 760-749KoreaE-mail:kimhd korea Textile machinery Research Institute 300Sampoong-dongKyeongsan 712-210Korea

Air jet loom, as one of the shuttleless looms, transports a yam into warps using viscosity and kinetic energy of an air jet. Performance of this picking system depends on the ability of instantaneous inhalation/exhaust, configuration of nozzle, operation characteristics of a check valve, etc. In the recent past, many studies have been reported on the air jet discharged from a nozzle exit, but studies for understanding the flow field characteristics associated with shear layer and shock wave/boundary layer interaction in the nozzle were not conducted enough. In this paper, a computational study was performed to explain the flow field in the air jet nozzle with an acceleration tube and validated with previous experimental data available. The results obtained from the computational study show that, in the supersonic flow regime, the flow field depends significantly on the length of acceleration tube. As nozzle pressure ratio increases, drag force acting on the string also increases. For a longer acceleration tube, the total pressure loss is large, owing to the frictional loss.

关键词： compressible flow nozzle shear layer shock wave air jet loom shuttleless loom

Effect of Inlet Guide Vanes on the Performance of Small Axial Flow Fan

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Journal of Thermal Science 2017年第6期26卷 504-513页

作者： LIU Yang LIN Zhe LIN Peifeng JIN Yingzi Toshiaki Setoguchi heuy dong k.m key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech University Department of mechanical Engineering Saga University School of mechanical Engineering Andong National University

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 arc performed. The steady flow is simulated by the calculations of Navier-Stokes equa- tions coupled with RNG k-epsilon turbulence model, while the unsteady flow is computed with large eddy simu- lation. According to the theoretical analysis, the inlet guide vanes with outlet angle of 60° are regarded as the op- timal inlet guide vanes. The static characteristic experiment is carried out in a standard test rig and the aerody- namic 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 simu- lation results and the experimental data. It is found that the static characteristics of small axial flow fan is im- proved 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.

关键词： small axial flow fan inlet guide vanes static characteristics aerodynamic noise internal flow characteristics

Control of the Asymmetric Flow in Rocket Nozzles

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Journal of Thermal Science 2013年第2期22卷 97-102页

作者： Shigeru matsuo Shotaro Suetsugu Junji Nagao Tokitada Hashimoto Toshiaki Setoguchi heuy dong k.m Department of Advanced Technology Fusion Saga University Graduate School of Science & Engineering Saga University Institute of Ocean Energy Saga University School of mechanical Engineering Andong National University

In some rocket nozzle flows, the existence of the transition from FSS to RSS and the occurrence of asymmetric flow are known in previous researches. As a result, the transition causes excessive side-loads that may damage the nozzle. Thus, it is important to investigate the method in order to control the asymmetric flow separation. In the present study, the relationship between the asymmetric separation and the rate of change of the pressure ratio with time was investigated from the point of view of the transition from FSS to RSS in the supersonic nozzle experimentally. Further, change of the flow separation by using step and cavity, and the possibility of the control was demonstrated. As a result, it was shown that the method using a cavity was effective for the control of the separation pattern.

关键词： Compressible flow Asymmetric shock wave Rocket nozzle Control Experiment

Effect of Nozzle Geometry on the Flow Characteristics of Spiral Flow Generated through an Annular Slit

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Journal of Thermal Science 2007年第2期16卷 149-154页

作者： Shigeru mATSUO Tae-Hun k.m Toshiaki SETOGUCHI heuy dong k.m Yeon-Won LEE Department of mechanical Engineering Saga University1Honjo-machiSaga-shiSaga 840-8502Japan Graduate school of Science and Technology Saga University1Honjo-machiSaga shiSaga 840-8502Japan School of mechanical Engineering Andong National University388Songchun-dongAndong 760749Korea School of mechanical Engineering College of EngineeringPukyong National UniversitySan 100Young-Dang DongBusanKorea

In comparison with previous researches of swirling flow, spiral flow generated in the spiral nozzle has some different flow characteristics. It does not need a forced tangential momentum to generate its velocity and has some different merits from the swirling flow such as long potential core and low tangential velocity. In this study, the effect of nozzle geometry on the flow characteristics in spiral nozzle was investigated by experiment and computation. As a result, the flow characteristics obtained by experiment has a satisfactory agreement with computational results, quantitatively and qualitatively.

关键词： nozzle flow characteristics momentum numerical simulation

Effect of the Uneven Circumferential Blade Space on the Performance of Small Axial Flow Fan

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Journal of Thermal Science 2016年第6期25卷 492-500页

作者： LIU Yang LIN Zhe LIN Peifeng JIN Yingzi Toshiaki Setoguchi heuy dong k.m key Laboratory of Fluid Transmission Technology of Zhcjiang Province Zhejiang Sci-Tech UniversityHangzhou310018China Department of mechanical Engineering Saga UniversityHonjo-machiSaga840-8502Japan School of mechanical Engineering Andong National UniversitySeongcheon-Dong1375Gyeongdong-RDAndongGyeongsangnuk-DO760-749Korea

Effects of the uneven circumferential blade space on static characteristics and aerodynamic noise of a small axial flow fan are studied in this *** blade angle modulation is adopted to design a series of unequally spaced fans,which have different maximum of modulation angular *** 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 *** to theoretical analysis,a fan with a maximum of modulation angular displacement of 6° is regarded as the optimal unequally spaced *** experiment of static characteristic is carried out in a standard wind tunnel and the aerodynamic noise of both fans is tested in a semi-anechoic ***,performances of the optimal unequally spaced fan are compared with those of the prototype *** results show that there is reasonable agreement between the simulation results and the experimental *** is found that the discrete noise of the optimal unequally spaced fan is lower than that of the prototype fan at the near field monitoring *** can be explained that the total pressure fluctuation of the optimal unequally spaced fan is much more regular than that of the prototype fan.

关键词： prototype blade fluctuation uneven turbulence aerodynamic rotating unsteady mellin slowly