This paper describes an experimental investigation of tip clearance flow in a radial inflow turbine. Flow visualisation and static pressure measurements were performed. These were combined with hot-wire traverses into the tip gap. The experimental data indicates that the tip clearance flow in a radial turbine can be divided into three regions. The first region is located at the rotor inlet, where the influence of relative casing motion dominates the flow over the tip. The second region is located towards midchord, where the effect of relative casing motion is weakened. Finally a third region exists in the exducer, where the effect of relative casing motion becomes small and the leakage flow resembles the tip flow behaviour in an axial turbine.

This paper describes an investigation of the tip leakage flow in a radial inflow turbine with two different uniform clearances of 0.6% and 1.2% of span. The clearances are typical of radial turbines for industrial applications. Measurements were also performed for increased axial Subscripts 3 rotor inlet n blade normal p passage tf pressure driven tip leakage flow sf scraping flow

This paper describes an experimental investigation of tip clearance flow in a radial inflow turbine. Flow visualization and static pressure measurements were performed. These were combined with hot-wire traverses into the tip gap. The experimental data indicate that the tip clearance flow in a radial turbine can be divided into three regions. The first region is located at the rotor inlet, where the influence of relative casing motion dominates the flow over the tip. The second region is located toward midchord, where the effect of relative casing motion is weakened. Finally, a third region exists in the exducer, where the effect of relative casing motion becomes small and the leakage flow resembles the tip flow behavior in an axial turbine. Integration of the velocity profiles showed that there is little tip leakage in the first part of the rotor because of the effect of scraping. It was found that the bulk of tip leakage flow in a radial turbine passes through the exducer. The mass flow rate, measured at four chordwise positions, was compared with a standard axial turbine tip leakage model. The result revealed the need for a model suited to radial turbines. The hot-wire measurements also indicated a higher tip gap loss in the exducer of the radial turbine. This explains why the stage efficiency of a radial inflow turbine is more affected by increasing the radial clearance than by increasing the axial clearance.

The use of multi-sensor fast-response pressure probes is now relatively common place. Unfortunately, these probes are often larger than ideal. It is for this reason that single sensor probes are sometimes used in investigations of unsteady flow. In use, the single sensor probe must be placed at a number of different orientations to the flow, often achieved by simply rotating the stem of the probe mount. The run time of a given experiment increases in proportion to the number of orientations employed. Furthermore, the number of orientations is usually more than is strictly required due to poor conditioning of the experiment. This results in a significant amount of redundant information being available and run-time costs being increased. This paper describes a data reduction technique that reduces the run time cost of using single sensor fast response probes to the minimum. This is achieved by using all of the data obtained in the experiment so that there is no redundancy no matter how many orientations are employed. The method relies on comparing the measured data with the calibration data in order to obtain a best fit between the two datasets.