AS9120B, ISO 9001:2015, AND FAA AC 0056B ACCREDITED

What Is a Gas Turbine Engine Cooling System?

Due to the intense heat generated when fuel and air are burned in internal combustion engines, there needs to be some form of cooling mechanism in place. Generally, reciprocating engines are either air-cooled or liquid-cooled. Air-cooled engines are cooled down by passing air over fins attached to the cylinders, whereas liquid-cooled engines are cooled down by passing liquid coolant through jackets surrounding the cylinders. In addition, the cooling issue is further simplified because combustion only occurs during every fourth stroke of a four-stroke-cycle engine.

The burning process in a gas turbine engine is continuous, and a majority of the cooling air must be passed through the engine interior. If only enough air were admitted to the engine to provide an ideal fuel-air ratio of 15:1, the internal temperatures would increase above 4,000 degrees Fahrenheit. Instead, a large quantity of excess air that fits this ratio is admitted to the engine, cooling the hot sections to acceptable temperatures ranging from 1,500 to 2,100 degrees Fahrenheit. Please note that while the gasses have begun to cool, the conductivity of the metal in the casing carries heat to the exterior.

The secondary air making its way through the engine cools the combustion-chamber liners. The liners are made to induce a thin, fast-moving film of air over the inner and outer surfaces of the liner. Can-annular-type burners are often equipped with a center tube that leads cooling air into the center of the burner to promote high combustion efficiency and rapid dilution of the hot gasses while minimizing pressure losses. In all types of gas turbines, large amounts of relatively cool air mixes with the burned gasses aft of the burners, cooling them before they enter the turbines.

Cooling-air inlets are typically featured around the outside of the engine, allowing cool air to enter the turbine case, bearings, and turbine nozzle. Meanwhile, internal air is bled from the engine compressor section and is vented to the bearings and other parts of the engine. When situated on the side of the engine, the case is cooled down by outside air moving around it. The engine exterior and the engine nacelle are cooled by fanning air around them. Keep in mind that the forward section is referred to as the cold section, whereas the aft section (turbine) is referred to as the hot section.

Cooling the Accessory Zones

Turbine powerplants can be divided into primary zones which are isolated from one another by fireproof bulkheads and seals. The zones include the fan case compartment, intermediate compressor case compartment, and the core engine compartment. Each zone receives calibrated airflows to keep temperatures around the engine aft at levels that are acceptable. Such airflow ensures proper ventilation to prevent the buildup of harmful vapors. For instance, zone 1 is around the fan case which contains the accessory case and the electronic engine control (EEC). This area is vented with RAM air through an inlet in the nose cowl and is exhausted via a louvered vent in the right fan cowling.

Zone 2 contains the fuel and oil lines, which are cooled by fan air from the upper part of the fan duct and exhausted at the lower end back into the fan air stream. Additionally, because there are also fuel and oil lines in this area, removing any unwanted vapors is paramount. Zone 3, on the other hand, is the area from the high-pressure compressor to the turbine cases, the fuel and oil lines, as well as other accessories. In this zone, air makes its way from the exhaust of the precooler and is expelled from the aft edge of the thrust reverser inner wall and the turbine exhaust sleeve.

Turbine Engine Insulation Blankets

To bring down the temperatures of the exhaust duct or thrust augmentor (afterburner) and to eliminate the possibility of fuel or oil coming in contact with the hot sections of the engine, it is critical to provide insulation on the exhaust duct of gas turbine engines. As such, insulation blankets containing fiberglass as the low conductance material and aluminum foil as the radiation shield are used.

Conclusion

Automatize Industrials is a leading distributor of top-quality turbine engines and their related accessories. With countless items in our inventory, customers can easily meet rigid time constraints and inflexible budget requirements. Get started today and see how Automatize Industrials can serve as your strategic sourcing partner!


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