ABSTRACTCHARACTERISTICS OF ALTERNATIVE FUELS AND ALTERNATIVECOOLING OF THERMAL POWER PLANTSByChristopher David BolinIn regions of the world where the infrastructure for electrical power generation and distribution is unreliable or outdated moving to a distributed power generation is a viable strategy for the future. Gas turbine engines at all scales can be used to meet local power demands efficiently. Remote sites will require small engines relying on a variety of fuel sources including alternative fuels (i.e., fuels derived from non-fossil sources) as well as cleaner, from an emissions standpoint, methods of using fossil sources. Near larger industrial and domestic loads larger co-generation plants will be necessary. These co-generation plants will require cooling for a steam condenser to maximize the efficiency of the vapor cycle. In arid locations surface and sub-surface water sources may be insufficient to meet cooling demands for both environmental and regulatory reasons. At such locations an alternative cooling strategy will be required. This work is divided into two parts that investigate fundamental questions regarding alternative fuel issues for small scale gas turbine engines and cooling issues for larger co-generation plants.In the first part of this work the application of biogas to small scale generation systems isexplored. Biogas is a term used for the collection of gases produced by the anaerobic digestion of organic waste materials such as garbage and animal manure. The resulting gas consists of CH4 diluted with varying amounts of CO2, H2O, N2, and other trace species. The content of biogas is feedstock dependent and thus variable. This poses a challenge to combustor designers. Many modern gas turbine combustors use a fuel-lean, premixed strategy to meet strict emissions standards. Operating under such conditions, often near the lean-extinction limit, can be difficult with fuel variability. Empirical relations, determined with simplified experimental devices, can be used by the designer to provide a first-order approximation of the operating envelope of a new system. Such relations are available for a range of traditional fuels but are lacking for newer alternative fuels. Stability limits for a range of biogas fuel contents are investigated here using stirred-reactor theory. Correlations to predict lean-extinction limits based on content are developed. Finally, a facility for expanding this research with a laboratory well-stirred reactor (WSR) for the investigation of biogas extinction limits and combustion emissions will be described.The second part of this work explores the use of vapor-compression refrigeration systems for steam condenser cooling. Larger loads invite the use of combined cycle power systems. These systems use large industrial or aero-derivative gas turbine topping cycles with conventional steam power bottoming cycles to increase fuel efficiency. An alternative cooling system using vapor compression refrigeration is an alternative method of cooling that can reduce or eliminate the need for cooling water. A novel facility for small scale experiments to explore the operating envelope of the proposed system is described here. The results of preliminary investigations into the use of R-410a as a steam condenser coolant are also presented.
Read
