Research Interests:

Semi-closed cycle gas turbines are being explored due to their potential gains in the combination of high efficiency, high part-load efficiency, compactness, and extremely low emissions, using hydrogen or other fuels. We are exploring this concept on the system level, as well as modeling, fundamental component-level analysis, and experimentation. Two complete engines of this type are operational, a demonstration unit and an experimental test bed. Combustion and refrigeration combined-cycle experiments are currently under way. Spacecraft require active cooling of some components, including cryogenic storage of propellants. The resulting heat must be radiated to space. Research in this area centers on a novel thermally-actuated heat pump systems suitable for space applications. The goal is to use active thermal management to raise the radiator temperature significantly, thereby reducing its mass. System models, a system demonstration rig, and detailed experiments of ejectors with high-speed two-phase flow support the development of this thermal management strategy for NASA. Fuel cell research centers on water balance and distribution issues in PEM systems, as well as system-level interactions between reformation and hydrogen-rich gas utilization in phosphoric acid fuel cells. A fully-operational, instrumented, fuel cell powered bus is being operated as a test bed to obtain real-world data pertaining to efficiency and emissions of fuel cell vehicles. The results show the limits imposed on fuel cell systems when operating over a wide range of conditions and the consequent degradation in efficiency and emissions. In addition, a state-of-the-art 110 kW phosphoric acid fuel cell power plant is being installed for model validation and as a laboratory testbed.