Microscale combustion and power generation

“microcombustion”, micro power generation and micropropulsion

On-line presentations:

• Microcombustion and power generation
• Micro solid oxide fuel cells
• Micropropulsion and gas pumping

Pictures

Papers:

• Ronney, P. D., “Heat-Recirculating Combustors,” Chapter 10 in Microscale Combustion and Power Generation (Y. Ju, C. Cadou and K. Maruta, Eds.), Momentum Press LLC, New York, 2015, pp. 287-320.
• Chen, C.-H., Ronney, P. D., “Scale and geometry effects on heat-recirculating combustors,” Combustion Theory and Modelling, Vol. 17, pp. 888 – 905 (2013).  (DOI: 10.1080/13647830.2013.812807)
• Zeng, P., Wang, K., Ahn, J., Ronney, P. D., “A self-sustaining thermal transpiration gas pump and SOFC power generation system,” Proceedings of the Combustion Institute, Vol. 34, pp. 3327 – 3334 (2013).  (DOI: 10.1016/j.proci.2012.06.168)
• Chen, C.-H., Ronney, P. D., “Three-dimensional Effects in Counterflow Heat-Recirculating Combustors,” Vol. 33, pp. 3285-3291 (2011)  (DOI: 10.1016/j.proci.2010.06.081)
• Ahn, J., Shao, Z., Ronney, P. D., Haile, S., “A Thermally Self-Sustaining Miniature Solid Oxide Fuel Cell,” Journal of Fuel Cell Science and Technology, Nov. 2009. (DOI: 10.1115/1.3081425)
• Cho, J.-H., Lee, J., Lin, J., Sanford, L. N., Richards, C. D., Richards, R. F., Ahn, J., Ronney, P. D., “Demonstration of an external combustion micro-heat engine,” Proceedings of the Combustion Institute, Vol. 32, pp. 3099-3105 (2009).  (DOI: 10.1016/j.proci.2008.07.017)
• Hyland, P., Lee, J. M., Lin, C. S., Ahn, J., Ronney, P. D., “Effect of ammonia treatment on Pt catalyst used for low temperature reaction,” Proceedings of the ASME International Mechanical Engineering Congress and Exposition 2007, Vol. 6: Energy Systems: Analysis, Thermodynamics and Sustainability, pp. 135 – 140 (2008).
• Sanford, L. L., Huang, S. Y., Lin, C. S.., Lee, J., Ahn, J., Ronney, P. D., “Plastic Mesoscale Combustors/Heat Exchangers,” Proceedings of the ASME International Mechanical Engineering Congress and Exposition 2007, Vol. 6: Energy Systems: Analysis, Thermodynamics and Sustainability, pp. 141 – 145 (2008).
• Kuo, C.-H., Ronney, P. D., “Numerical Modeling of Heat Recirculating Combustors,” Proceedings of the Combustion Institute, Vol. 31, pp. 3277-3284 (2007).  (DOI: 10.1016/j.proci.2006.08.082)
• Haile, S., Ronney, P. D., Shao, Z.,  “Power generator and method for forming the same,” U. S. Patent No. 7,247,402, July 24, 2007.
• Shao, Z, Haile, S., Ahn, J., Ronney, P. D., Zhan, Z., Barnett, S. A., “A thermally self-sustained micro Solid-Oxide Fuel Cell with high power density,” Nature, Vol. 435, pp. 795-798 (9 June 2005).  (DOI: 10.1038/nature03673)
• Cohen, A., Ronney, P. D., Frodis, U., Sitzki, L, Meiburg, E., Wussow, S., “Microcombustor and combustion-based thermoelectric microgenerator,” U. S. Patent No. 6,951,456, Oct. 4, 2005 (continuation of patent No. 6,613,972).
• Ronney, P. D., “Analysis of non-adiabatic heat-recirculating combustors,” Combustion and Flame, Vol 135, pp. 421-439 (2003).  (DOI: 10.1016/j.combustflame.2003.07.003)
• Ahn, J., Eastwood, C., Sitzki, L., Ronney, P. D., “Gas-phase and catalytic combustion in heat-recirculating burners,” Proceedings of the Combustion Institute, Vol. 30,  pp. 2463-2472 (2005).  (DOI: 10.1016/j.proci.2004.08.265)
• Posthill, J., Reddy, A., Siivola, E., Krueger, G., Mantini, M., Thomas, P., Venkatasubramanian, R., Ochoa, F., Ronney, P. D., “Portable power sources using combustion of butane and thermoelectrics,” 24th International Conference on Thermoelectrics (ICT), pp. 520 – 523 (2005). (DOI: 10.1109/ICT.2005.1520000)
• Cohen, A., Ronney, P. D., Frodis, U., Sitzki, L, Meiburg, E., Wussow, S., “Microcombustor and combustion-based thermoelectric microgenerator,” U.S. Patent No. 6,613,972, Sept. 2, 2003.
• Maruta, K., Takeda, K., Ahn, J., Borer, K., Sitzki, L, Ronney, P. D., Deutchman, O., “Extinction Limits of Catalytic Combustion in Microchannels,” Proceedings of the Combustion Institute, Vol. 29, pp. 957-963 (2002).  (DOI: 10.1016/S1540-7489(02)80121-3)
• Weinberg, F. J., Rowe, D. M., Min, G., Ronney, P. D., “On thermoelectric power conversion from heat re-circulating combustion systems,” Proceedings of the Combustion Institute, Vol. 29, pp. 941-947 (2002). (DOI: 10.1016/S1540-7489(02)80119-5)

Narrative description

It is well known that the use of combustion processes for electrical power generation provides enormous advantages over batteries in terms of energy storage per unit mass and in terms of power generation per unit volume, even when the conversion efficiency in the combustion process from thermal energy to electrical energy is taken into account. For example, hydrocarbon fuels provide an energy storage density between 40 and 50 MJ/kg, whereas even modern lithium ion batteries commonly used in laptop computers provide only 0.4 MJ/kg. Thus, even at only 5% conversion efficiency from thermal to electrical energy, hydrocarbon fuels provide about 5 times higher energy storage density than batteries. For this reason automotive and aviation vehicles employ internal combustion engines for prime moving and electrical power generation almost entirely to the exclusion of batteries, even in vehicles whose mass may be less than 1 kg or more than 10⁵ kg. In the past few years, many research groups from around the world have begun to develop devices called Micro Electro-Mechanical Systems, or “MEMS,” typically borrowing technologies originally developed for microelectronic devices. Recently much attention has been focused on the application of MEMS devices to the production of electrical power, so-called “Power MEMS” devices, typically in applications where batteries are currently used.

Many groups involved in Power MEMS are investigating scaled-down versions of well-established macro-scale combustion devices (internal combustion engines, gas turbines, pulsed combustors, etc.) There are numerous difficulties with this approach, for example the fact that flames extinguish due to heat losses if the dimension of the combustion chamber is too small, i.e. “microcombustion” is more difficult than “macrocombustion.” Furthermore, even if flame quenching does not occur, heat and friction losses become increasingly important at smaller scales since the heat release due to combustion and thus power output scales with the volume of the engine whereas the heat and friction losses scale with the surface area.

For these reasons we have developed two Power MEMS system concepts based on the integration of the following four technologies:

•  Microcombustion, heat transfer and thermal management using a two-dimensional or three-dimensional toroidal “Swiss Roll” counterflow heat exchanger and combustor.

•  Power generation using thermoelectric elements or a single-chamber solid oxide fuel cell

•  To pump the gaseous reactants through the combustor and (optionally) generate thrust with no moving parts, a catalytic combustion driven thermal transpiration pump.

These approaches have the following advantages over “traditional” approaches to micropower generation:

•  No moving parts, thus no friction losses

•  Reduction of heat loss effects, thus minimizing flame quenching problems and minimizing efficiency losses.

•  Monolithic construction, requiring at most one simple mechanical assembly step (for the electrochemical fabrication technique.)

•  Ability to use hydrocarbon fuels, unlike some Power MEMS concepts which require hazardous, low-energy-per-unit-storage-volume fuels such as hydrogen, or fuels derived from solid rocket propellants.

The goal of these projects is to produce practical working devices using a combination of experimental examination of scaled-up model microcombustion, power generation and propulsion devices, numerical modeling of macro- and micro-scale devices, and micro-scale fabrication using the aforementioned techniques.