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Automotive engineering

PSA Peugeot Citroën reduces environmental impact of its diesel
engines with standardized LMS Virtual.Lab Engine Acoustics process

Over the past 15-20 years, PSA Peugeot Citroën has put its name on the diesel technology map. Recognized worldwide, the company's high-pressure direct injection diesel engines using common rail technology can be found on more than 15 million vehicles. This is superb news for the planet since this engine technology consumes 20% less than other diesel engines with corresponding reduced CO2 emissions and features excellent drivability with noise, vibration and handling levels equal to gas engines.

Image 1: Without proper engineering and countermeasures, engine noise will increase with the new Euro 6 emissions regulations.

Continuous improvement is clearly the mindset at PSA Peugeot Citroën where better driving performances and less pollution have been high on the agenda for more than a decade. The HDi engine featured an efficient diesel particulate filter pollution control system, which destroyed all diesel particles and reduced emissions to barely measurable levels (0.004 g/km). With this solid first success already under its belt, PSA Peugeot Citroën began standardizing this formula for success throughout the development process as a whole, guaranteeing greener and cleaner product continuity for years to come.

Standardizing acoustic engineering
Creating a crowd-pleaser in the modern-day automotive sector is twofold. One, a car must be clean and green, and two, it still must be fun to drive. This fun-to-drive factor is directly linked to not only how the car handles, but also how it sounds. Does it "growl" during acceleration and hum while it cruises? Being able to control this factor in the engine design is where the study of engine acoustics becomes an important way to not only make better performing cars but also more appealing ones.

Back in 2004, PSA Peugeot Citroën was already busy thinking about how to get this valuable brand aspect into the total development process. Controlling the sound wasn't only a 'nice-to-have' for the passengers; minimized pass-by noise was becoming a necessary statistic to sell. So certainly, this was an area that needed to be addressed early in the design process - and hopefully as efficiently as possible.

"Our Methods Department at PSA Peugeot Citroën realized that engine acoustics needed to be seriously implemented into the car development process. No only to control passenger comfort factors, but also to make sure that all the new engines in development would meet the pass-by and other noise regulations," stated Mr. Olivier Dumas, NVH Simulation Project Manager for Powertrain. "We evaluated LMS Virtual.Lab Acoustics from Siemens PLM Software
 and found it fit well into our engine simulation process."

Reaching maximized design flexibility
Soon after the successful evaluation, the team, located in PSA Peugeot Citroën's research and development center in La Garenne-Colombes near Paris, began to use LMS Virtual.Lab Acoustics successfully for projects. The next step was to improve the process even further by automating it to save time and avoid errors. The new standardized LMS Virtual.Lab Acoustics process was subsequently completely integrated into PSA Peugeot Citroën's entire vehicle development system.

"Acoustics is an important element in every step of the process, but doing a separate acoustics iteration after each major step from functional CAD and meshing to assembly, modal analysis, transfer path analysis and dynamic and acoustic response, well, that was just non-compatible with the time constraints," said Mr. Dumas.

What Mr. Dumas and his research team knew was that they would have to design a method to automate the acoustics performance in the engine during the different development phases. To reach maximum design flexibility, the overall process would need to be adapted.

Image 2: The engines of the Peugeot 508 and the Citroën C4 were partly designed with the LMS Virtual.Lab engine acoustics simulation process.

Image 3: Engine noise constitutes a major contribution to the overall noise level of the vehicle.

Image 4: Today, a number of different models emitting less than 130 g/km CO2 are commercialized by Peugeot and Citroën.

New process equals more time to design
"In our old process, we couldn't change much by the time we were in CATIA V5. Now, with our new process, we use a simplified parametric and less detailed model where dimensions and concepts can still be changed. This way, we can still take NVH information into account in the engine design. It is not all set in stone," added Mr. Thomas Dericquebourg, NVH Simulation Engineer for Powertrain.

This not only allows more flexibility in the CAD design; the team also can rely on a whole list of validated components to choose from to assemble the mesh and developing the best possible input and output sections as well.

"Our LMS Virtual.Lab Engine Acoustics solution has certainly sped up our process, but more importantly, it lets us test acoustic concepts much earlier in the development project. We can check out more design possibilities, do more parallel calculations and optimize the acoustic design much earlier," stated Mr. Laurent Beaune, Head of NVH, Strength, Crash and Optimization Numerical Simulation for Powertrain and Chassis. "It is really easy to use and completely automated so that users can be trained and up to speed in no time."

Now with the HDi engine in production, the team can easily validate the simulation by checking the test results using LMS Test.Lab.

"This process improvement encourages us to implement it for the exhaust system and gear box as well," concluded Mr. Beaune.

For further information, view website:  Refer to page 312

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