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A performance prediction model is developed for axial-type turbines that operate at partial admission. Losses generated within the turbine are classified into windage loss, expansion loss and mixing loss. This developed loss model is compared with an experimental result when a turbine operates with a rectangular-type nozzle at a partial admission rate from 22% to 37%. The present predicted results show better agreement with the experimental results than with those predicted by other models, as the expansion loss in this model is developed more closely to the real flow situation. If a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. In this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model is found to be in good agreement with the experimental results. Thus, the developed model could be applied to predict the performance of axial-type turbines that operate at various partial admission rates or with different nozzle shapes.

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An axial-type fan that operates at a relative total pressure of 671 Pa and a static pressure of 560 Pa with a flowrate of 416.6 m 3 /min is developed using an optimization technique based on the gradient method. Prior to the optimization of the fan blade, a threedimensional axial-type fan blade is designed based on the free-vortex method along the radial direction. Twelve design variables are applied to the optimization of the rotor blade, and one design variable is selected for optimizing a stator which is located behind the rotor to support a fandriving motor. The total and static pressure are applied to the restriction condition with the operating flowrate on the design point, and the efficiency is chosen as the response variable to be maximized. Through these procedures, an initial axial-fan blade designed by the free vortex method is modified to increase the efficiency with a satisfactory operating condition. The optimized fan is tested and compared with the performance obtained with the same class fan to figure out the optimization effect. The test results show that the optimized fan not only satisfies the restriction conditions but also operates at the same efficiency even though the tip clearance of the optimized fan is greater than 30%. The experimental and numerical tests show that this optimization method can improve the efficiency and operating pressures on axial-type fans.

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