59687 - High-Resolution Thermal Profiling of a Combustor in a Non-Dedicated Test Using Thermal History Coatings 

The requirement for reduced emissions and the growing demand on gas turbine efficiency are in part met through increasing firing temperatures. However, continuous cost pressures on development budgets demand reduced time for dedicated thermal testing. Consequently, manufacturers are seeking novel temperature measurement technologies to satisfy their need to validate new engine designs in combination with reduced development costs and reduced development times. This paper will demonstrate how a new temperature mapping technology can be utilized for non-dedicated (multi-cycling) testing while still delivering valuable high resolution temperature data across a combustor can. 

Thermocouples are typically used to monitor the temperature during tests. They only provide point data at the location to which they are attached and are costly and difficult to apply to the location of interest. Traditionally, colour changing thermal paints are used to deliver temperature measurements over component surfaces, but require dedicated testing with short-duration exposure of only a few minutes, complete dismantling and re-assembly of the engine for further testing. These paints can also erode easily in demanding environments and are not always REACH compliant.

Thermal History Coatings (THC) present a new and unique solution to provide high-density temperature information. THCs are applied to the surface of a component and the coating permanently changes consistent with the maximum temperature of exposure during test. A laser-based instrumentation technique is then used to interrogate the coating. The maximum temperature profile of the surface can be determined through a customized calibration giving the engine operator flexibility in its load conditions. This paper demonstrates the capability of the THC in a non-dedicated test on a combustor of an industrial gas turbine.

Given the complex cooling system of the combustor, the high achieved temperatures and the long-time exposure, the robust coating of THC is ideally suited for the testing of the measurement techniques under real engine conditions.

The coated region of the combustor can in question expanded to cover both the internal and external surfaces of the component, covering both the bare metal on the external surface, and the internal Thermal Barrier Coating. Most significant is the number of measurement points, namely in excess of 12,000 points; the high number of measurement points enables advanced analysis beyond what is generally achieved with alternative techniques. This provides unique insight into the impact of local features, such as the region adjacent to a local cooling hole.

The combustor was instrumented with several thermocouples. THC was applied to inside and outside surfaces for validation against the other temperature measurement techniques and to evaluate its capability in the harsh combustor environment. The temperature profile is compared to a Conjugate Heat Transfer (CHT) model and thermocouple measurements for validation purposes.

The results demonstrate the benefits of THC as a temperature profiling technique for use in combustion chambers for non-dedicated testing.