Evaluation of Ceramic Composite Wedge for High Speed Combustor Applications

Abstract

Ultra high temperature ceramic based Zirconium composite “Wedge” was fabricated with suitable dimensions required for high speed combustor using centrifugal thermit process. The wedges are normally used in the application of the ‘flame holding’ and ‘fuel injection’ of the combustor. The basic requirement of the wedge is that it has to have a very high thermal shock resistance along with near erosion free control surface in un-cooled conditions. Also it has to withstand ultra high temperatures of the order of 2000K under extreme heat flux of 10 MW/m2 and high velocity of gas injection. Wedge shaped strut was machined with special techniques to get the required shape. It was fastened inside the water cooled rectangular duct using tungsten carbide dowel pins. The wedge was tested at the High Speed Combustor Test Facility (HSCTF), with the air flow conditions of 5bar pressure and with an average temperature of 1900K. The flow velocity was at Mach number 2 for the duration of 20seconds. Experiments were repeated many times with the same inlet flow conditions. Thermal shock conditions were created by abruptly bringing down the flow temperature from 1900K to 300K with in short duration of 5seconds. The strut was intact even after several repeated tests except for oxidation coating. The mechanical properties and microstructure characteristics of fuel strut specimens after the combustor test have been investigated and compared with just fabricated material before the test. X-ray radiography also corroborates the flaw less condition of the strut. These results have been discussed in light of the integrity and surface micro structure mechanisms involved in the evaluation process.