Air Turbine Starters (ATS) are critical devices in modern aviation, used to safely and efficiently start aircraft turbine engines. At the same time, mechanical seals are an essential element of these systems: they must provide high performance under extreme operating conditions, ensuring the sealing of high-pressure compressed air and resistance to very high temperatures.
With this article, we at Meccanotecnica Umbra will give a detailed overview of this system and the crucial role played by mechanical seals.
As mentioned, an ATS (Air Turbine Starter) system, or air turbine starter, is a device designed to start aircraft turbine engines, including jet engines and turboprops. It is a well-established and indispensable technology that allows the main engine to be started by using compressed air instead of electricity or other forms of starting. Because of its ability to generate high torque quickly and safely, the ATS is widely used to ensure reliable starts even in harsh operating conditions.
The operation of an ATS system is based on the use of compressed air that is drawn from an auxiliary power unit (APU), another running engine, or an external ground source. This high-pressure compressed air is directed to the choke's internal turbine. The turbine, thanks to the energy from the air, begins to rotate at very high speeds, transforming pneumatic power into mechanical power.
This mechanical power is then transferred through a gearbox and gear system to a drive shaft, which puts the compressor shaft of the aircraft's main engine into rotation. When the engine reaches the minimum speed required to independently start combustion, the starting system automatically disengages, allowing the engine to continue running independently. This disengagement mechanism is critical to avoid unnecessary wear and overload on the ATS system once the start-up phase is complete.
Mechanical seals in Air Turbine Starter (ATS) systems play a vital role in ensuring proper operation and reliability of the device. First, the seals must of prevent leakage of compressed air: since ATSs work with high-pressure air to generate the torque needed to start the main engine, it is essential that the critical points of the system are perfectly sealed. Any leakage would result in a drop in efficiency, making the starter less performant or even inoperative under extreme conditions. Another equally important function is the isolation of lubricating fluids. Some ATS systems have lubrication circuits to reduce friction and protect moving parts. In these cases, mechanical seals serve to prevent contamination between compressed air and lubricants, maintaining overall efficiency and protecting the system from potential malfunctions caused by unwanted mixing of fluids.
In order to perform these critical tasks, mechanical seals for ATS must possess specific and advanced characteristics. First, they must withstand very high operating temperatures, often exceeding 300-400 °C, without suffering damage or loss of performance. Their sealing ability must also be flawless in the presence of high-pressure compressed air, with values that can exceed 4-6 bar.
Another essential requirement is resistance to wear and mechanical fatigue: air turbine starters operate at extremely high rotational speeds, reaching up to 50,000-120,000 rpm. Seals must therefore be designed to withstand significant mechanical stress and minimize friction to reduce wear over time.
In addition, it is crucial that seals be compatible with the lubricants and aviation fluids used, avoiding chemical reactions that could compromise their effectiveness. Finally, light weight is a must in aeronautics: the use of innovative materials such as advanced ceramics, silicon carbide or reinforced carbon makes it possible to reduce the weight of the system without sacrificing performance, while ensuring high operating life and maximum reliability.
In this complex environment, we at Meccanotecnica Umbra are able to provide our customers with custom mechanical seal solutions for ATS systems. Thanks to our advanced technical know-how, we develop high-performance seals specifically designed for critical environments, using innovative materials that can withstand high temperatures and wear. With our custom design capability, we can tailor each seal to our customers' specific needs, contributing to the success of their most challenging aviation applications. Contact us now and discover all our solutions for the aviation industry!
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TX 78577 - U.S.
Phone: 01 956 782 2400
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Novi, MI 48375
Phone: 248-347-0606 ext. 224
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