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360 degrees of a jet engine

Speed read
  • Simulations of aircraft engines are key to improving efficiency and reducing pollution
  • Previous simulations were limited to single components due to demands on computing power
  • New methodology couples components and represents a full 360-degree simulation

Airplane engines work, no question about it. But their complex machinery could still be optimized for greater efficiency. After all, more efficient engines require less fuel, which reduces cost and atmospheric pollution.

That’s why engineers and scientists are continuously working to improve aircraft engine designs. Computer simulations play an essential role in this process, expanding and enhancing experimental results by adding information that is difficult to gain from experimental setups.

<strong>The full-engine simulation</strong> reveals interactions between different engine components. The incoming pressure wave from the compressor is detectable in the combustion chamber, visible here as red and green on the sides of the chamber. Courtesy CERFACS/AKIRA/Project FULLEST. However, engine simulations that make use of supercomputers have also been limited due to the vast computing power required to perform detailed and accurate simulations. That’s why, so far, simulations have mostly consisted of only one engine component, such as the high-pressure compressor or the combustion chamber.

But now, Dr. Carlos Pérez Arroyo and project leader Dr. Jérôme Dombard, together with their co-workers at CERFACS, a private laboratory in Toulouse, France, have successfully performed one of the first ever full-engine simulations.

Executed on PRACE supercomputers, the simulation included three engine components: the fan, the high-pressure compressor, and the combustion chamber. The project was done in close collaboration with two aviation companies: Safran SA, a large producer of helicopter and airplane engines, and Akira technology, a pioneering aircraft engine company that constructed the engine model DGEN380 that was simulated in this project, a so-called turbofan designed for business jets.

Although the analysis is still in progress, the first results already demonstrate that such a multi-component simulation is feasible—a fact that was not evident before—and that it delivers significant benefits.

The benefit of coupling components

“When you couple different engine components, simulations become a lot more extensive and complex,” Dombard says. To carry out the simulation, Dombard’s team member and postdoctoral researcher Carlos Pérez Arroyo used the AVBP code developed at CERFACS.

<strong>The simulation included three adjacent components       </strong>  of the DGEN380 engine: the fan, the high-pressure compressor, and the combustion chamber. A coupled representation is required in order for the physical interactions between the components to be investigated. Courtesy CERFACS/AKIRA/Project FULLEST. Pérez Arroyo’s first challenge was to perform each of the single component simulations, which exhibit a variety of different physical processes. Then he developed a methodology to couple the components and achieve the fully integrated simulation. Within the new setup, the so-called unsteady coupling between the different components is mathematically solved and corresponds to the most realistic and high-fidelity representation of the underlying physical processes.

Finally, in order to represent a full engine, it was necessary to build a 360-degrees simulation. In contrast, conventional simulations representing only one single component can benefit from the presence of repetitive elements such as the fan blades or the injectors of the combustion chamber.

“In fact, many simulations of single components compute just one of these repetitive sections,” says Dombard.

But when simulating several coupled components that each possess different architectures, this is impossible. Instead, the simulation has to cover the entire 360 degrees of the object. This drastically increases the size and complexity of the simulation. In the end, the full 360-degree large-eddy simulation highly resolved the timeline of the combustion process, as well as the spatial resolution of the engine components represented by two billion cells.

Insights for the community

The simulation has been well worth the effort, because now, for the first time, scientists can investigate the interactions between the different components and how they influence processes within the engine.

For example, the preliminary results revealed that there is a strong interaction between the high-pressure compressor and the combustion chamber. Specifically, the compressor generates a pressure wave with a very high amplitude that enters into the combustion chamber. This pulse alters the environment in the chamber and influences the whole mass flow, meaning the air and fuel flows taking part in the combustion process.

“So far, no engine simulation took this effect into account,” says Pérez Arroyo. “Now, we have shown that coupling the components indeed makes a difference.”

Moreover, preliminary results indicate that the pressure wave generated from the compressor also affects the upstream component, the fan.

The team will continue to analyze these interactions between components—not only between adjacent components such as the fan and compressor, but also between non-neighboring components like the fan and the combustion chamber.

The next extension of the simulation will incorporate the final missing engine component, the turbine. Ultimately, the scientists aim to provide a complete high-fidelity database of unsteady coupled engine components to help other teams develop new simulations and validate existing ones.

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Read the original article on PRACE's website.

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