Abstract
Modern low-pressure turbine engines are equipped with casings impingement cooling systems. Those systems (called Active Clearance Control) are composed of an array of air nozzles, which are directed to strike turbine casing to absorb generated heat. As a result, the casing starts to shrink, reducing the radial gap between the sealing and rotating tip of the blade. Cooling air is delivered to the nozzles through distribution channels and collector boxes, which are connected to the main air supply duct. The application of low-pressure turbine cooling systems increases its efficiency and reduces engine fuel consumption.
Highlights
Researches focused on flow behavior and the heat transfer process of the impingement cooling systems are divided into two categories: numerical modeling [24,25,26] and experimental researches [27,28]
Impingement cooling systems play a significant role in many technical applications, especially in the aero industry (Active Clearance Control systems)
Due to the adjusted amount of cooling air directed onto the turbine casing surface, they are able to control clearance between the blade tip and casing with sealing
Summary
Gas path sealing is a challenging problem of aircraft gas turbine engine design. It is caused because the clearance between the blade tip (rotating structure) and casing with sealing (static structure) tends to vary during engine operation due to various mechanical and thermal loads. The main role of the impingement cooling system (to provide efficient gap control) is gap reduction between the tip of the blades and sealing during engine operation in the cruise phase. The benefits of active clearance control are, among others, increased engine efficiency, reduced specific fuel consumption (SFC), and reduced NOx and CO emissions. Up to 1000 extra cycles of engine encompass on-wing time may be high-t achieved byand operating it at lower temperatures, control.
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