Project Number: 068
Category: Aircraft Technology Innovation
A critical issue related to the operation of a gas turbine in today’s world is the ingestion of dirt, sand, and other fine particles that lead to blockages of cooling holes and passages required for effectively cooling the walls of the combustion chamber. Dirt is one of the primary sources of durability issues in the combustor and turbine. The effect that dirt has is to build an additional layer on components that can lead to blockages of cooling passages. As these blockages occur, the metal temperatures rise dramatically. As double-wall cooling designs for combustors continue to evolve, it is important to assess the likelihood of dirt deposition. Because the need to fly in dirty environments is on the rise, the criticality of operations in dirty environments is increasing. Modern gas turbine engines typically employ a double-walled combustor liner with impingement and effusion cooling plates whereby impingement cooling enhances the backside internal cooling and effusion cooling creates a protective film of coolant along the external liner walls. Dirt accumulation on the internal and external surfaces severely diminish the heat transfer capability of these cooling designs. This study would initially investigate practical designs for reduced dirt accumulation at representative temperature conditions, and then explore how the designs are insensitive through detailed flow and heat transfer measurements on a scaled geometry.
The major expected benefit from this study is a cooling design for combustor walls that is insensitive to dirt accumulation, as well as an improved understanding of why it is insensitive. Cooling performance of combustor walls is critical to aircraft engine durability and yet being a strong function of the environment in which turbines operate. The goal of this research is to drive towards a cooling design that is as effective at existing or lower coolant flowrates as state-of-the-art designs, while being insensitive to dirty cooling air that is derived from the operational environments of the turbine. The resulting outcome will ensure that engine designs achieve fuel burn reductions over a longer time period, as well as allowing continued turbine operations while reducing turbine maintenance.