Effect of Aircraft-Engine Turbine Design on the Size of Blade Tip Clearance,
Abstract
The optimal selection of turbine blade tip clearances is one of the most complex and critical problems in the design and operation of aircraft turbine engines. In addition to the ambient temperature, the tip clearance of rotor blades in the cold state is affected by the temperature variation under various operating conditions. Some stresses on turbine components depend on the angular velocity; the deformation will vary for different rpm, which must be considered in determining the necessary tip clearance. In general, the accepted tip clearance is 2 percent of the mean blade length in a given turbine stage. It has been found that in turboprop engines, the casing and rotor stresses increase as the rotor velocity increases. In turbojet engines, the stresses are relatively high at low rpm, followed by a decrease and then increase again reaching the maximum magnitude at high rpm. These stress variations are caused by gas temperature changes. The minimum tip clearance depends mainly on the turbine design, and, in some cases, it is possible to achieve a practically constant tip clearance. Heat resistant turbine casing linings do not seem to be necessary in all cases. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 29, 1969
- Accession Number
- AD0864984
Entities
People
- S. Szczecinski
Organizations
- National Air and Space Intelligence Center