Ceramic matrix composite (CMC) have higher temperature capability and lower density than nickel based alloys which have been used for hot section components of gas turbine engines. These properties are expected to bring many benefits, such as higher turbine inlet temperature (TIT), reduction of cooling air, and reduction of weight, when it is used as the material for hot section components of gas turbine engine.
The authors have been developing CMC turbine vane for aircraft engines. In this paper, the authors present the summary of design, manufacturing, and testing, which were conducted from 2010 to 2012.
The purpose of this work was to verify that the SiC-SiC CMC which IHI has developed has the applicability to aircraft turbine vanes. The concept was planned for CMC hollow turbine vanes, in which the airfoil and the platform are fabricated in CVI process. As the demonstration of this concept, the first stage turbine vane was designed with CMC for IHI IM270 that is the 2MW-class small industrial gas turbine engine.
Bending rig test was conducted at room temperature in order to check the structural feasibility of the airfoil-platform joint. The outer platform of vane was fixed in the same way with the engine parts, and the load simulating the aerodynamic force was applied at the airfoil portion. The fracture load was higher than the load which the vanes receive in the actual engine.
Burner rig test was conducted in order to check the durability against thermal cycle. A CMC vane was set between dummy metal vanes, and cyclically heated by gas burner. The maximum airfoil surface temperature was set to 1200 degree C, and the maximum temperature difference between airfoil and platform was about 700 degree C. The minimum airfoil temperature at the interval of heating was about 300 degree C. The time of one thermal cycle was 6 minutes that consisted of 3 minute heating and 3 minute natural cooling. The test was conducted for 1,000 cycles. In post-test inspection there was no defect like a crack.
Engine test for CMC vanes was conducted using IHI IM270. The four CMC vanes were mounted into the first stage turbine nozzle assembly in place of the normal metal vanes. The test was conducted for 400 hours. The inlet temperature of CMC vanes were measured by thermocouples installed at the leading edge, and the measured temperature was about 1050 degree C at the steady state.
From this work, the applicability of the design concept for the CMC vane to actual engine was verified in which airfoil-platform are fabricated in CVI process.