An experimental study of partial admission losses with various blade tip clearances using a linear cascade

Turbo-expanders have been used for energy conversion in many fields. They are sometimes operated in partial admission mode, depending on the stability of the energy source, such as solar energy or waste thermal energy, which can fluctuate depending on environmental or process condition. The ability to operate in partial admission can be advantageous because it allows continuous operation without interchanging components. However, this method also leads to lower turbo-expander efficiency. This experimental study was conducted to investigate losses at various partial admission rates. In addition, the effect of tip clearance was studied since it is another important parameter affecting turbo-expander performance. A linear cascade was fabricated with a nozzle that was set to 65° based on the axial direction. A blade row was designed to be movable along the pitchwise direction in order to investigate flow characteristics as a function of blade movement. Flow structures and pressure losses were measured for various partial admission rates and tip clearances. The experiment was conducted at a Reynolds number of 3 × 105 based on the chord. The experimental results showed that losses in the passages depended not only on partial admission rate but also location relative to the nozzle.