NSK has introduced a groundbreaking gas turbine generator bearing specifically designed for electric vertical take-off and landing (eVTOL) aircraft, including large drones. This new bearing technology offers key advancements, such as higher speed revolution performance and a new lubrication mechanism that reduces the required lubricant supply by an impressive 80%, significantly extending eVTOL flight range.
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Pioneering eVTOL Innovation
With the rapid development of eVTOL technology, these aircraft are poised to play a major role in the future of transportation, with the market projected to reach €124 billion ($138 billion) by 2035. Traditionally, eVTOLs have relied on fully motorized propulsion systems. However, as the demand for longer flight ranges and enhanced transportation capabilities grows, hybrid motors are becoming increasingly popular due to their high output, compact size, and lightweight construction.
Gas Turbine Generators and Sustainability
Among the various hybrid motor designs, gas turbine generators have emerged as a leading contender. These systems can run on sustainable fuel sources, such as biofuels and hydrogen, offering a solution aligned with carbon neutrality goals. This makes them an attractive option for eVTOL propulsion systems, as they combine efficiency with environmental responsibility.
Meeting the Demand for High-Speed Revolution Performance
Extending the flight range of eVTOL aircraft depends on several factors, one of the most critical being the high-speed revolution performance of gas turbine generator bearings. Recognizing this need, NSK developed a bearing capable of achieving over 2.5 million dmn (the product of bearing pitch diameter and rotational speed). This innovation not only delivers the required high-speed performance but also optimizes lubrication requirements, a vital factor in improving eVTOL efficiency.
The Challenge of Jet Lubrication
Traditionally, jet lubrication has been the most common method used for high-speed bearings, but it comes with drawbacks. It requires a large amount of lubricating oil and results in high power loss, both of which reduce the overall efficiency of the propulsion system. While under-race lubrication offers a more efficient alternative, it lacks versatility and is costly, limiting its widespread application.
NSK’s New Lubrication Mechanism
To address these challenges, NSK designed a novel lubrication mechanism featuring an improved spacer shape. This new mechanism stores oil in the spacer and uses centrifugal force to supply the optimal amount of lubricant to the bearing. As a result, the bearing requires only 25% of the lubricating oil needed by conventional jet lubrication systems, while also reducing power loss by 33%.
This innovative design not only provides a cost-effective and versatile lubrication solution but also enables OEMs to reduce the weight of the oil supply scavenge pumps and lubricant tank. These reductions contribute directly to extending the flight range of eVTOL aircraft, a critical factor for their commercial success.
NSK’s advanced bearing technology marks a significant leap forward for the eVTOL industry. With its ability to enhance speed revolution performance and dramatically reduce lubrication requirements, this innovation is set to play a key role in improving the efficiency and sustainability of eVTOL aircraft. As the industry continues to grow, hybrid motors powered by gas turbine generators will likely become the preferred propulsion system, driving the future of urban air mobility.
