Wilson TurboPower (WTPI) is developing a 300-kW microturbine that is designed to achieve50% electrical efficiency. This is unusually high given the history of lower efficienciesdemonstrated by small engines of any type, including diesels. However, WTPI has chosen acycle capable of producing high efficiency as well as specifying components (compressor, heatexchanger, and turbine) that can operate at high efficiencies. The key enabling technology is thecompany's ceramic regenerator, based on MIT technology and licensed by WTPI. It is capable ofhandling high-temperatures (>1000°C) at high-effectiveness (97.5%) with a low pressure drop (e.g., 1 – 2 percent). The high effectiveness results thermodynamically in a requirement of a lowcycle pressure ratio (about 2.5:1) for optimum performance. The component efficiencies ofcompressors and turbines of low pressure ratio are intrinsically high. WTPI also divides this lowpressure ratio among four compressor stages and three turbine stages. Doing so greatly reducesthe kinetic energy that is lost from single stages, and thus substantially improves the componentefficiencies. The blade peripheral speeds are also low, leading to relatively very low stresses inthe ceramic turbine and therefore to great confidence in its integrity. The ceramic regeneratormakes possible higher operating temperatures, further increasing efficiency. By these means ashaft-power efficiency of 55% can be confidently predicted for the 300-kW engine, which whencoupled to a high-efficiency electrical generator would lead to an electrical efficiency of about50%.
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