Effects of combustion chamber geometry upon exit temperature profiles.

摘要

Highly non-uniform temperature distributions at the exit of a gas turbine combustion chamber can cause significant damage to downstream hot section components, resulting in an increase in maintenance costs and operational down-time. To investigate the effects of combustion chamber geometry on exit temperature fields, an ambient pressure and temperature test rig was constructed and instrumented. A thermocouple rake was manufactured to acquire temperature measurements in the combustion chamber exit plane. Rig operating conditions were set to simulate an engine operating condition of 463 km/hr (250 knots) at 7 620 m (25 000 ft) by matching the Mach number, equivalence ratio and Sauter mean diameter. The apparatus included the combustion section of an Allison/Rolls Royce T56-A-15 gas turbine engine, which was internally blocked to a 120° sector.;A three-dimensional laser scanning system was used to acquire the geometric features of a population of twenty combustion chambers, which varied in service conditions. A CAD model of the T56-A-15 Series III combustion chamber was created and used as the reference model. The combustion chamber geometric deviations were then extracted by comparing the scanned data to the reference model within the selected software. The combustion chamber exit temperature profiles and geometric deviations were then compared.;The main conclusion of this research was that small deviations from nominal dimensions in the dilution zone of the combustion chamber correlated to an increase in pattern factor. A decrease in the mixing of the products of combustion and dilution air was observed as damage in the dilution zone increased. This reduction in mixing created a more compact, higher temperature core flow. Secondary findings illustrated consistent patterns of combustion chamber geometric damage occurring from service use. The results obtained from this research were compared to past studies.;Keywords: combustion, pattern factor, combustion chamber, gas turbines, experimentation