Academic Staff

WEN Chih-Yung (Prof.)
Associate Head and Professor
BEng (National Taiwan University); MSc (Caltech, U.S.A.); PhD (Caltech, U.S.A.); AFAIAA; FHKIE
FG609
27666644
23654703
Area of Specialization

Aerodynamics of hypersonic vehicles; Supersonic combustion; Active flow control; Magnetic fluid flows; Fuel cell technologies

Short Description

Professor Wen received his Bachelor of Science degree from the Department of Mechanical Engineering at the National Taiwan University in 1986 and Master of Science and PhD from the Department of Aeronautics at the California Institute of Technology (Caltech), U.S.A. in 1989 and 1994 respectively. He worked at Caltech as a Research Fellow from February 1994 to July 1994 and then continued his teaching and research works at the Department of Mechanical Engineering at the Da-Yeh University, Taiwan. He was promoted to full professorship in February 2002. He had been the Chairman of the Department of Mechanical and Vehicle Engineering from August 1997 to July 2000, and the Provost from August 2004 to July 2006 in the Da-Yeh University, Taiwan. In August 2006, Professor Wen joined the Department of Aeronautics and Astronautics of the National Cheng Kung University (NCKU), Taiwan, before joining the Department of Mechanical Engineering, The Hong Kong Polytechnic University in 2012 as professor. Professor Wen has authored and co-authored many scientific papers, conference papers and book chapters. He was also awarded 11 patents. His current research interests are in the areas of (1) Aerodynamic applications of plasma actuators in delta-winged UAVs and MAVs; (2) Hypersonic aerodynamics and scramjet engine design; (3) Fuel cell applications in the electric power system of a micro spacecraft; and (4) Flow instabilities of magnetic fluids and their applications in micro-mixers. Professor Wen, currently an AIAA Associate Fellow, serves as a member of, various key professional boards and bodies related to the Aerospace Engineering.

溫志湧教授於1986年在國立台灣大學機械工程學系取得工程學士學位,並於1989年及1994年在美國加州理工學院航空工程學系分別取得理學碩士及哲學博士學位。他於1994年2月至7月在美國加州理工學院擔任研究員,其後在台灣大葉大學機械工程學系繼續從事教學及研究工作,並於2002年2月獲取教授席。在大葉大學服務期間,他於1997年8月至2000年7月及2004年8月至2006年7月分別擔任機械與自動化工程學系系主任及教務長。溫教授於2006年8月加入台灣國立成功大學航空太空工程學系,之後,於2012年8月加入香港理工大學機械工程學系。溫教授是多篇科學論文、國際學術會議論文集及書籍章節的作者或合著者。他亦成功取得十一項專利。他現時的研究領域主要集中於(1)電漿致動器於三角翼UAV及MAV的空氣動力應用;(2)高超音速空氣動力學及超燃衝壓引擎設計;(3)微型燃料電池於微型航天器電力系統的應用以及(4) 磁性流體流動的不穩定性和於微型混合器的應用。溫教授現為美國航空太空學會的副院士,他亦擔任多個與航空航太工程有關的專業學會及組織的成員。

Selected Research Project / Teaching & Learning Project:

1. Applications of Plasma Actuators on an Unmanned Aerial Vehicle

Plasma actuators that discharge at one atmosphere have attracted considerable attention in the aerospace industry, especially in the applications of UAV and MAV, due to their features of simple mechanism, easy maintenance, low cost and fast response (1 ns, theoretically). Note that the unmanned aerial vehicle (UAV) and the micro aerial vehicle (MAV) have the characteristics of low speed, small size, and flying at a low Reynolds number. The plasma actuator is to apply a high positive voltage and a low negative voltage on the surface of an aerial vehicle by two electrodes, which then ionize the adjacent gas molecules and form the plasma. The electric field induces the motion of the plasma and results in the ionic wind consequently. At a low Reynolds number, the ionic wind alters the velocity profile inside the boundary layer through the particle collisions and may change the aerodynamic characteristics of the vehicle. The objective of this project is to experimentally investigate the effects of Dielectric Barrier Discharge (DBD) plasma actuators on the aerodynamics of Boeing 1303 UCAV delta-winged UAV in three years. A small-scale1303 delta wing model will be constructed. The fundamental aerodynamics of the 1303 delta wing model at various low Reynolds numbers and angles of attack will be investigated. The experiments will be conducted in a low speed wind tunnel. Particle image velocimetry (PIV) will be adopted to visualize the flow field and obtain the velocity distribution. A force balance will be used to measure the aerodynamic characteristics of the delta wing. The DBD actuators will be implemented in different positions and their effects on the aerodynamics of the 1303 delta wing model will be examined. In order to reduce power consumption, the plasma actuators will be applied with a pulsed mode high voltage. The pulse frequency and duty cycle will be varied to identify the most appropriate parameters. PIV and smoke wire visualization of the flow over the delta wing model, with actuator functioning, will be conducted to observe the change of the leading edge vortex structures. Real flight experiments will be also conducted. The DBD plasma actuators will be implemented on the full-scale 1303 delta wing UAV and will be operated under the optimum parameters found.

(a) (b)

Fig. Smoke wire visualization of the flow over the delta wing model with A1 actuator (A) off and (B) on, at a = 20o and Rec = 7.5 × 104. The blue uniform plasma is clearly seen in (B).

2. Numerical Study of Rarefaction Effects and Thermochemical Nonequilibrium Problems on Hypersonic Flow around Space Vehicles

This three-year joint project is aimed at solving an urgent problem of high-altitude aerothermodynamics: development and application of an effective numerical approach for studying hypersonic flow around space vehicles with allowance for rarefaction effects and thermochemical nonequilibrium of the flow. The two main tasks of the project are: (1) development and improvement of models and methods, as well as software tools for numerical investigations of chemically reacting hypersonic flows with the use of kinetic and continuum descriptions; (2) study of aerothermodynamics of high-altitude flight of promising space vehicles, including those with leading edges of small-radius bluntness, with allowance for nonequilibrium physical and chemical processes and analysis of their influence on distributed (pressure, friction, and heat flux) and integral (drag force, lift force, heat transfer, pitching moment, etc.) aerothermodynamic characteristics along the hypersonic segment of the flight trajectory. In this joint research project, the kinetic approach using DSMC method will be mainly conducted by the Russian research group, while the continuum approach using Navier-Stokes equations by the our group. The cross-validation between both approaches in the transition range will also be conducted. It is expected that the detailed information on aerothermodynamics of a promising space vehicle on the hypersonic segment of the descent trajectory will be obtained for flow regimes ranging from free-molecular to continuum.

Fig. Simulated  Mach number, pressure and temperature distributions around the EXPERT capsule at 90km,with no roll angle and an AoA of −5.5o

3. Research on Supersonic Combustion

Supersonic Combustion Ramjet (SCRamjet) engine is the next generation propulsion system and its design encompasses the key technologies of the efficient supersonic combustion and the integrated hypersonic airframe. The aims of the project are to build up the fundamental tools and capacities for supersonic combustion research. In the project, the ground test facilities for generating hypersonic flow fields and supersonic combustion, optical diagnostic technologies, and CFD tools with real gas effects and turbulence modelling of supersonic combustion flows will be developed. Hydrogen will be used as the fuel initially. The project will then be extended to the hydrocarbon-fueled technologies, based on the tools developed with Hydrogen fuel. The project will (1) design and build up a He-driven reflected shock tunnel (Ma=2~6) and a hydrogen fuel injection system (Ma=1), conduct the flow visualization and pressure and heat flux measurements of the supersonic combustion flow fields, and compare with CFD simulations; (2) complete the two-dimensional OH-LIPF experiments to depict the temperature and OH concentration distributions in the supersonic combustion flow fields, with the adaption of the tunable KrF excimer laser and temperature calibration; (3) conduct the numerical parametric study.

 (a)
 
 (b)

 Fig. Pre-heated H2 Transverse Sonic Jet in a Supersonic Crossflow at Ma=2 (a) Schileren image (b) OH-chemiluminescence 

4. Design of Direct Sodium Borohydride-Hydrogen Peroxide Fuel Cell

In the last two decades, the development of micro satellites (100-500 kg in weight) becomes more and more important because of the trend in satellite miniaturization and the mature of MEMS technologies. Considering the development of scientific payloads in the micro satellites, their volume, weight, and required electric power are significantly reduced consequently. Therefore, this research project is motivated to develop an integrated all–liquid micro Direct Borohydride/Hydrogen Peroxide Fuel Cell (DBFC) stack system to provide an independent electric power source for the operation of scientific payloads in a micro satellite and to meet the satellite weight and space requirements. In the earlier study, we have developed a 5x5 cm2 DBFC single fuel cell with power of 16 W. Extending the earlier results, this proposed three-year research project is motivated to develop an integrated all–liquid DBFC stack system with Balance of Plant (BOP). The optimal efficiency of the modular 10-cell DBFC stack system will be found through a series of experiments. The results of this research can be easily adapted for the 3C applications.

Selected Publications
  • Chen, H., Wen, C.Y. *, Yang,C.K,“Numerical Simulation of Hypersonic Air-He Shock Tube,” AIAA Journal, vol. 50, no. 9, pp. 1817-1825, 2012.
  • Yang, A.S, Wen, C.Y.*, Tseng, C.S and Chang H.T. “Parametric Study of Helix Configuration in a Ribbed Lip Seal,” Tribology International(SCI), Vol. 53, pp. 98-107, 2012.
  • Wen, C.Y., Liang, K.P., Chen, H., Fu, L.M., “Numerical analysis of a rapid magnetic microfluidic mixer,” Electrophoresis, Vol. 32, pp. 3268–3276, Nov., 2011
  • Wen, C.Y.*, Yang, A.S,Huang, F.J. and Chang H.T. “Novel Helix Design and Parametric Analysis for Ribbed Helix Lip Seal for Improving Sealing Performance,” Tribology International, Vol. 44, pp. 2067-2073, Nov. 2011.
  • Wen, C.Y. *, Lin, Y.S., Lu, C.H., and T. W. Luo, “Thermal Management of a Proton Exchange Membrane Fuel Cell Stack with Combined Pyrolytic Graphite Sheets and Fans,” International Journal of Hydrogen Energy, Vol. 36, pp. 6082-6089, 2011
  • Wen, C.Y., Yang, A.S*, Tsai, W.L and Tseng, L.Y., “Flow Analysis of a Ribbed Helix Lip Sealwith Consideration of Fluid-Structure Interaction,” Computer and Fluids, Vol. 40, pp. 324-332, 2011.
  • Wen, C.Y. * and Hornung, H. G., “Nonequilibrium Recombination after a Curved Shock Wave,” Progress in Aerospace Sciences Vol. 46, pp. 132–139, 2010
  • Wen, C. Y., Tsai, C. H. and Fu, L. M., “Design and Characterization of Magnetic Micro-mixer,” ELECTROPHORESIS, Vol. 30, pp. 4179-4186, 2009
  • Wen, C.Y. *,Lin, Y.S. and Lu, C.H., “Experimental Study of Clamping Effects on the Performances of a Single Proton Exchange Membrane Fuel Cell and a Ten-cell Stack,” J. Power Sources, Vol. 192, pp 475-485, 2009.
  • Wen, C.Y. *, Lin, Y.S. and Lu, C.H., “Performance of a Proton Exchange Membrane Fuel Cell Stack with Thermally Conductive Pyrolytic Graphite Sheets for Thermal Management,” J. Power Sources, Vol. 189 (2), pp 1100-1105, 2009.
  • Yang, A.S, Wen, C.Y.* and Tseng, C.S, “An Analysis of the Flow Field around a Ribbed Helix Lip Seal,” Tribology Internationa,l Vol. 42 (5), pp 649-656, 2009.
  • Wen, C.Y. *, and Huang, G.W., “Application of High Thermal Conductivity Graphite Sheet on Thermal Management of PEM Fuel Cells,” J. Power Sources, Vol. 178, pp 132-140, 2008.
  • Lee, C. Y, Chang, H. T and Wen, C. Y*,A MEMS-based Valveless Impedance Pump Utilizing Electromagnetic Actuation,” Journal of Micromechanics and Microengineering, Vol. 18, 035044(9pp), 2008
  • Wen, C.Y., Chen, C.Y., and Kuan, D.C., “Experimental Studies of Miscible Labyrinthine Instability of Miscible Ferrofluids in a Hele-Shaw Cell,” Physics of Fluids, Vol. 19, pp 084101-1—084101-8, 2007
  • Yu, H.Y., Peng, H.Y., Wang, J.L., Wen, C.Y., and Tseng, W.Y., “Quantification of the Pulse Wave Velocity of the Descending Aorta Using Axial Velocity Profiles from Phase-Contrast Magnetic Resonance Imaging,” Magnetic Resonance in Medicine, Vol. 56, pp 876-883, 2006.
  • Wen, C. Y.