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Airborne Achievement

Why is it important to run a jet engine at highest possible temperatures? The answer to this and other key questions of engine design lies in an almost invisible technology.

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Whenever a new airliner is unveiled, the press and the public are inevitably wowed by the new plane’s size, speed or nonstop range. Novel seat configurations and high-tech passenger amenities also make the news when the latest model is launched. This is the moment, usually after decades of difficult development work, when the airframe designers can take a bow.

When it comes to getting a ticket, however, most passengers are looking for a good buy that includes a smooth, quiet ride and a safe landing. Indeed, lower fares per passenger mile drive current and projected increases in airline sales, while lower emissions per passenger mile and quieter engines make the increased number of total miles flown environmentally sustainable.

The rarely recognized heroes of both these developments are the men and women who design and constantly update the engines. Their work on making the plane’s propulsion system more energy efficient—without sacrificing performance—is decisive for the cost of the passenger’s ticket and the environmental impact of the aircraft.

Some of these engineers work for the aircraft makers, some of them for the jet engine manufacturers. All of them are to some degree dependent on esoteric advances being made by the likes of Oerlikon’s Surface Solutions Segment. Oerlikon Metco, an important part of this business, commands unique technology expertise in material properties and surface solutions, and has thereby become the partner to cultivate whenever an aviation engineer wants to improve the performance of a jet engine.

The overriding research and development objectives for jet propulsion are quite simple. New engines need to be lighter, quieter, more durable, more reliable and more powerful than their predecessors, while consuming less fuel and burning the fuel they do consume more cleanly. Simple objectives, unfortunately, are not always easy to achieve, yet Oerlikon Metco has mastered a wide variety of techniques to help the company’s partners do just that.

Planning ahead

Whenever a company develops new materials or processes for aerospace customers, the work has to be based on anticipating their future needs. According to Dieter Sporer, the head of aerospace engineering at Oerlikon Metco, the innovations being built into jet propulsion systems today have sometimes been in development for as much as three decades.

“Substantial investments of both time and money are required to validate new technologies before they can be introduced into new engine designs,” says Sporer. “This is partly driven by aviation authority regulations, but to an ever greater extent, it is also being driven by the engine manufacturers themselves, who run extremely thorough test programs to make sure of the production feasibility, technical performance and operational reliability of anything they incorporate into a new engine.”

Ceramic matrix composites (CMCs) provide a good example. These were first suggested for use in jet engines in the mid-1980s, yet have only recently proven themselves for practical application in commercial engines. Without the environmental barrier coatings supplied by Oerlikon, optimal performance—including environmental stability in the high-speed combustion gases—could not be assured for this lightweight, extremely strong high temperature material.

When I ask Sporer why jet engineers want to run new engine designs at the highest possible temperatures in the first place, he tells me that increasing turbine entry temperature improves the thermal efficiency of a jet engine, which has a substantial impact on performance.

“The improved thermal efficiency,” he says “can be used to push power on take-off, providing increased maximum take-off weight or reduced fuel consumption. This reduces direct operating costs and allows for more payload to be carried by the aircraft, while reducing its CO2 emissions at the same time.”

In order to run a jet turbine at extremely high temperatures, high performance coatings provide a thermal barrier between the gas and the components through which it moves.

“The coatings we deliver play an important role in making high operating temperatures possible in practice,” says Sporer. “There is a constant need for innovative new coatings that can operate at ever-increasing temperatures, and we at Oerlikon Metco are extremely well-positioned to provide the materials, coating equipment, and ultimately the coating specifications to manufacturers searching for new solutions.”

The coatings on jet turbines protect them against environmental influences and corrosion and, thereby, help to save fuel, reduce emissions as well as costs for passengers.

Onwards and upwards

Compressor pressure ratios have also been increasing with each new generation of jet engine, and Oerlikon abradable coating solutions significantly improve both their efficiency and operational safety. The company’s products log millions of flight hours every year on turbofan and turboprop engines.

Dieter Sporer says that Oerlikon Metco develops abradable materials and coatings not only for their compositional integrity but also for their sprayability via the proprietary Oerlikon technologies to apply the ideal coating in a most economical way. Their performance is subsequently evaluated on large-scale test rigs that have been built by Oerlikon.

“One of these rigs,” says Sporer, “is the only ‘Component Validation’ rig of its type in the world and saves manufacturers significant costs by closely simulating engine operating conditions that could otherwise only be analyzed in real engines.”

This is just one example of how Oerlikon provides full solution packages for aerospace engineers, ranging from material design, via advanced technology application processes, to surface technology testing. The surface solutions segment also provides coatings that protect jet engines from physical and functional deterioration—coatings that are applied throughout the engine to prevent damage from erosive or corrosive wear; and the company is working at the cutting edge of physical vapor deposition technology for thin film coatings, which are just starting to gain widespread use in engines to fight particle erosion and corrosion phenomena.

When asked to speculate about the future, Dieter Sporer confidently replies, “The use of new materials, such as CMCs and aluminides—a class of materials that lie between metal and ceramics—may very well transform jet engine design in the near future, but not without the innovative surface solutions, including both materials and application processes, that Oerlikon Metco can provide.”

This is good news for the jet engine designer, but for the passenger, surface solutions will always have low visibility. Be that as it may, such surface solutions will continue to have a great impact on the airliner’s performance, economy and environmental sustainability—and not least of all, on the price of the passenger’s ticket.

By Frederic Love

1 comments

  1. keyur maniya

    ” Best Innovation is the one which gives the balance of Industrial Development and co2 footprint reductions”, this article is the best example of the above quote; as it provides a solution not only for the Industrial development and also for environmental protection and also provides a solution for the betterment of social life by reduced airfare.
    As a research intern, I am working on smart coatings for Wear diagnosis and Temperature measurement. After 5 months of working in the field of TBC, this article gives me the motivation to work in the company like Oerlikon to give my innovative contribution to the research.

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