EXPERIMENTAL INVESTIGATION OF LOW ASPECT RATIO AND TIP CLEARANCE ON TURBINE PERFORMANCE AND AERODYNAMIC DESIGN
Abstract
The aerodynamics of any cooled turbine are compromised by mechanical design, fabrication techniques, heat transfer, and cooling restrictions. Additional requirements of high outputs out of small turbomachinery packages result in limitations on the turbine that are unique to low-airflow, high- pressure-ratio, small-category machines. These practical considerations limit the tip clearance, axial chord lengths, tolerances, and geometry. The resultant blading is usually of low-aspect-ratio type, and characteristically high secondary losses predominate. The report presents the aerothermodynamic design considerations of three turbine flowpaths, which were cold-flow tested to evaluate the performance effects of span aspect ratio and tip clearance on turbine efficiency. Complete maps were generated for the three configurations, and tip clearance effects were evaluated at design speed over a range of pressure ratios. Rotor blade aspect ratios were tested from 0.41 to 1.26, and blade heights varied from 0.36 inch to 1.09 inches. Rotor tip clearance was varied from 1.5 to 5.0 percent of the blade span. Results of the investigation suggest that predominance of high secondary losses should allow a design with high-aspect-ratio blading and low wheel speeds to produce the same performance as low-aspect-ratio blading with high rim speeds.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1968
- Accession Number
- AD0674201
Entities
People
- Casimir Rogo
- Roy Marshall