Some conventional turbo machines, such as gas turbine systems, are utilized to generate electrical power. In general, gas turbine systems include a compressor, one or more combustors, and a turbine. Air may be drawn into a compressor, via its inlet, where the air is compressed by passing through multiple stages of rotating blades and stationary nozzles. The compressed air is directed to the one or more combustors, where fuel is introduced, and a fuel/air mixture is ignited and burned to form combustion products. The combustion products function as the operational fluid of the turbine.
The operational fluid then flows through a fluid flow path in a turbine, the flow path being defined between a plurality of rotating blades and a plurality of stationary nozzles disposed between the rotating blades, such that each set of rotating blades and each corresponding set of stationary nozzles defines a turbine stage. As the plurality of rotating blades rotate the rotor of the gas turbine system, a generator, coupled to the rotor, may generate power from the rotation of the rotor. The rotation of the turbine blades also causes rotation of the compressor blades, which are coupled to the rotor.
Gas turbine vanes are static components of the turbine section, which are configured to direct hot gases (at temperatures above 2,200° F.) in a hot gas path to the rotating portions of the turbine to achieve rotational motion of the rotor. Though significant advances in high temperature capabilities have been achieved, superalloy components must often be air-cooled and/or protected with a coating to exhibit a suitable service life in certain sections of the gas turbine engine, such as the airfoils. In order to withstand the high temperatures produced by combustion, the airfoils in the turbine section are cooled. Cooling the airfoils represents a parasitic loss to the power plant, since the air that is used to cool the parts has to be compressed but the amount of useful work that be extracted is comparatively small. As such, it is desirable to cool these parts with as low flow of air as possible to allow for efficient operation of the turbine.
The volume of cooling air required may be reduced by using more advanced materials, which can withstand the high temperature conditions in the hot gas flowpath. These materials, such as ceramic matrix composites (CMCs), can increase gas turbine efficiency because their properties reduce the cooling requirements for the respective parts.
One challenge in developing CMC vanes that efficiently use the available cooling air is sealing between the CMC vane shell and the respective inner and outer side walls that define therebetween the hot gas path. Often, such side walls are made of a metal alloy with different thermal properties than the CMC vane shell, making sealing between the disparate materials difficult. Leakage of the cooling fluids from the vanes can increase the parasitic losses to the turbine (thereby reducing its efficiency) and can increase the temperature of the vanes (thereby leading to increased stress and/or wear).
An effective sealing system is needed to address this problem.