Dr L. Ma

BSc, MSc, PhD  

Senior Research Fellow: Fuel Cells and Renewable Energy

Room 3.28
Centre for Computational Fluid Dynamics
School of Process, Environmental and Materials Engineering
Faculty of Engineering
University of Leeds
Leeds
LS2 9JT
UK

Telephone: +44 (0)113 343 2481
Fax: +44(0)113 246 7310

Email: L.Ma@leeds.ac.uk

 

Research Interests

Wind Turbines

  • Aerodynamics of wind turbines
  • CFD analysis of the performance of wind turbines
  • Wind turbine design and aerodynamic optimisation techniques
  • Computational Aeroacoustics low noise wind turbine technology

Fuel cells

  • Developing novel CFD modelling tools for fuel cells (SOFC, PEMFC)
  • Experimental investigations on SOFC and PEMFC fuel cell system
  • Development of micro-fuel cell technology for electronic device

Coal and biomass combustion

  • Combustion of pulverised biomass fuels
  • Ash depositions prediction for pf fuel combustion

CFD modelling for fluid flow and heat and mass transfer

  • Aerodynamics over aircrafts
  • Modelling of trace species within gas turbine engines.
  • Heat transfer problems in industrial applications
  • Particle/pollutant-laden fluid flows

 

Aerodynamics of Wind Turbines

Wind turbine is a main technology that converts wind energy into electricity. It has been explored with great interest recently for both scientific research and prospected commercial impacts. We have been in closed collaboration with industry working on developing advanced modelling as well as designing tools for small to medium sized wind turbine design and optimisation. The focus of recent work is in the area of aerodynamic design and simulation of medium sized Vertical Axis Wind turbines using advanced CFD technology. One of the key areas that are being investigated is the characteristics of the aerodynamic stalls and aerodynamic load of the turbine blades, because it has a significant impact on both efficiency, level of noise, and the durability of the wind turbine. With vigorous validations the research is expected to contribute significantly to the theory of the wind turbine aerodynamics and to directly find its application in proving guidelines for new generation VAWT design and optimisation.

Wind field across a vertical axis wind turbine.   

Predicted torque of a vertical axis wind turbine.

CFD modelling of fuel cells

Fuel cell technology presents huge economical and environmental potential for the next generation power systems since it can offer great advantages over the conventional power generating systems in terms of both the energy efficiency and the emission reduction. However, at present, there exist numerous technical barriers that need to be overcome in order to make fuel cell technology become commercially competitive. As in many other industries, real-life tests of fuel cells are often expensive, time consuming and constrained by the availability of adequate measurement techniques but CFD has been recognised as one of the most important potential tools to assist the development of new and advanced fuel cell technology where cell design, test and optimization are the key stages in the process. We are working on the development of fuel cell predictive capabilities for SOFC and PEMFC using innovative CFD technology and through experimental validations with our fuel cell test rig.

fuel Cell geometry and mesh

Fuel cell geometry and mesh, and Mass fractions of the reactants               

100% biomass and Cofiring of coal and biomass for power generation

The use of biomass as a fuel stock in existing coal fired power systems has been considered as an important step in reducing power plant emissions.  At the moment, co-firing coal with a limited amount of biomass, typically 2-20%, has been implemented in large-scale plants.  Industrial tests on firing pure biomass have been carried out in order to predict any problems that may rise when this is happening in large-scale plants. However, CFD modeling techniques for biomass combustion still face significant challenges due to the lack of knowledge of the key combustion characteristics of biomass fuels. The presence of potassium in the biomass has become a significant issue and it is implicated in slagging, fouling and corrosion to the combustion system.  The paths of the NOx formation for biomass fuels are also different from that of coal. Based on the theoretical as well as experimental investigations, CFD models for 100% biomass and biomass-coal combustion have been developed which simulate all key stages of the combustion including potassium release and NOx formation. An advanced ash deposition model has also been developed.

 

     Track of Particles and particle deposition

Concorde accident investigations

A fatal accident in July 2000 involving an Air France Concorde near the Charles DeGaulle Airport in Paris led to the temporary grounding of the entire fleet of these supersonic passenger planes. As part of the investigation to explain the accident, we were asked to look into the reason why the fire stabilized on the wing once it started. A CFD model has been developed to understand the flow characteristics of the leaking fuel that gave rise to the observed flame formation. Several simulations were performed using an estimated takeoff speed and a range of attack angles that matched amateur photos of the incident. The CFD study, plus other recent studies on how to improve fuel tanks for the Concorde fleet, has led to modifications that should prevent a similar incident from happening in the future. The modified Concorde airliners were reintroduced to commercial service in October 2001.


Other fluid flow and heat transfer problems

We have an excellent knowledge of a number of commercial CFD software as well as developing user-friendly in-house software codes. Work on fluid flow and heat and mass transfer has implications in many areas of industries including aerodynamics, multiphase flow and conjugate heat transfer.

Potential PhD areas

  • Advanced Wind Turbine Technology
  • Advanced OxyCoal Combustion Carbon Capture Sequestration Technology
  • Micro PEM Fuel Cell Technology for Electronic Devices
  • Optimization of Coal-Biomass Co-firing Processes for Power Generation
  • Fluid flows and heat and mass transfer in industrial heat exchangers. (This project will focus on the numerical analysis of various fluid flow and heat transfer problems within industrial heat exchangers and explores potentially new techniques to improve the efficiency of the heat exchanger).
  • Thermal balance problems in fuel cell systems. (This project will focus on the modelling of the heat generation and transfer within fuel cell units or stacks).
  • Fluid flow and heat transfer problems in micro-reactors. (This project will develop CFD model for micro-reactors with focus on the heat generation and heat transfer in the reactor).
  • Modelling of biomass ash deposition in combustion systems and boilers. (This project will investigate the mechanisms of the biomass ash deposition in biomass combustion systems and develop CFD tools to predict the biomass ash deposition in the system).
  • Modelling of the biomass combustion and co-combustion in industrial furnaces. (This project will focus on the development of CFD model for biomass combustion processes and/or biomass-coal co-combustion processes).
  • Modelling of contaminant dispersion in industrial and environmental situations. (This project will focus on the advanced modelling of fluid flow and contaminant/pollutant transport in industrial and/or environmental problems such as channels and rivers).
  • Modelling of fluid flow and particulate transport in industrial channels and natural rivers. (This project will focus on the development of an advanced deposit transport model for bed-loaded and suspended deposit in channels and/or natural rivers).
  • CFD modelling and experimental investigations into the optimization of fuel cell systems. (This project will adopt a computational and experimental modelling approach to develop fuel cell system analysis and optimization technology).
  • CFD modelling and experimental investigations into fuel internal reform and fuel contaminations in solid oxide fuel cells. (This project investigates on the fuel internal reforming and the effect of fuel contaminations on the performance of the solid oxide fuel cells).

Selected Publications

  1. Y.B. Yang, V.N. Sharifi and J. Swithenbank, L. Ma, L.I. Darvell, J.M. Jones, M. Pourkashanian and A. Williams, Combustion of a Single Particle of Biomass, Energy Fuels, 22 (1), 306–316, 2008.
  2. L. Ma, M. Pourkashanian and D. B. Ingham, Chapter 4: Advances in Fuel Cell/Turbine Hybrid Systems, Applied Physics in the 21st Century, ED: Xin Chen, Research Signpost, Kerala, India, 2008.
  3. L. Ma, J.M. Jones, M. Pourkashanian, A. Williams, Modelling the combustion of pulverized biomass in an industrial combustion test furnace, Fuel, 86 (2007) 1959–1965, 2007.
  4. E. Carcadea, H. Ene, D. B. Ingham, R. Lazar, L. Ma, M. Pourkashanian and I. Stefanescu, A computational fluid dynamics analysis of a PEM fuel cell system for power generation, International Journal of Numerical Methods for Heat & Fluid Flow, 17(3): 302-312, 2007.
  5. R.I. Backreedy, L.M. Fletcher, L. Ma, M. Pourkashanian and A. Williams, Modelling Pulverised Coal Combustion Using a Detailed Coal Combustion Model, Combust. Sci. and Tech., 178: 763–787, 2006.
  6. A Bosoaga,  N. Panoiu, L.  Mihaescu, R. I. Backreedy,  L. Ma,  M. Pourkashanian  and A. Williams, The combustion of pulverised low grade lignite, Fuel, 85, 1591-1598, 2006R.I. Backreedy, L.M. Fletcher, J.M. Jones, L. Ma, M. Pourkashanian, A. Williams, K. Johnson, D.J. Waldron, P. Stephenson, Carbon burnout of pulverised coal in power station furnaces. Clear Air, International Journal on Energy for a Clean Environment, 7, 1–15, 2006
  7. R. I. Backreedy, J. M. Jones, L. Ma, M. Pourkashanian and A.Williams, A. Arenillas, B. Arias, J. J. Pis and F. Rubiera, Prediction of Unburned Carbon and NOx in a Tangentially Fired Power Station using Single Coals and Blends.  Fuel, 84, 2196-2203, 2005
  8. Ma, L., Ingham, D.B. and Pourkashanian, M., Chapter 16, Application of Fluid Flows through Porous Media in Fuel Cells, in Transport Phenomena in Porous Media III, Ed: Ingham, D.B., and Pop, I., Elsevier, John, Wiley & Sons Ltd, England, 2005.
  9. L. Ma, D.B. Ingham, M.C. Pourkashanian and E. Carcadea, Review of the Computational Fluid Dynamics Modeling of Fuel Cells. Journal of Fuel Cell Science and Technology, 2(4) 246-257, 2005.
  10. E. Carcadea, H. Ene, D. B. Ingham, R. Lazar, L. Ma, M. Pourkashanian and I. Stefanescu, Numerical simulation of mass and charge transfer for a PEM fuel cell. International Communications in Heat and Mass Transfer, 32(10): 1273-1280, 2005
  11. D. B. Ingham and L. Ma, Chapter 2: Fundamental equations for CFD in river flow simulations, in Computational Fluid Dynamics: Applications in Environmental Hydraulics, Edited by P Bates, S Lane and R Ferguson. John Wiley & Sons, Ltd. London, 2005.
  12. R.I. Backreedy, L.M. Fletcher, J.M. Jones, L. Ma, M. Pourkashanian and A. Williams, Co-firing pulverised coal and biomass: A modelling approach.  Proceedings of The Combustion Institute, 30, 2955-2964, 2005.
  13. S. Hancu, T Ghinda, L. Ma, D. Lesnic and D.B Ingham, Numerical modelling and experimental investigation of the fluid flow and contaminant dispersion in a channel, International Journal of Heat and Mass Transfer, 45, 2707-2718, 2002.
  14. D.B. Ingham and L. Ma, Predicting the performance of air cyclones, International Journal of Energy Research, 26, 633-652, 2002.
  15. L. Ma, P.J. Ashworth, J.L..Best, D.B. Ingham, L. Elliott and L. Whitcombe, Computational fluid dynamics and physical modelling of an upland urban river, Geomorphology, 44, 375-391, 2002.
  16. L. Ma, D.B. Ingham and X. Wen, Numerical modelling of the fluid and particle penetration through small sampling cyclones. J. Aerosol Sci, 31, 1097-1119, 2000.