Issue: Jan 2016


Aerodynamics for comfort  and lower emissions



by Nick Palmen

Active speedlips, active grille shutters and new underbody paneling systems designed to improve aerodynamics from the badge on the bonnet to the tailpipe are helping OEMs to lower fuel consumption and reduce emissions thanks to less drag.

Drag’s contribution to the driving experience, as well as overall consumption is increasing as vehicles become lighter and the efficiency of powertrains improves. One of the leading innovators in the field of automotive aerodynamics is Mannheim, Germany – based Röchling.

Design follows function

Automotive manufacturers use a clear design language for their vehicles in order to increase their brand value with a “familiar face”. A “vertical active grille shutter” (AGS) helps solve the challenge of ensuring that design does not interfere with air flow function. Röchling’s solution is vertically arranged blades, which allow a high degree of integration into the vehicle design while maintaining all functions.

The concept allows the air flap system to be placed immediately behind the radiator grille, even in demanding packaging geometries. A separate approach is followed with the integration of the active grille shutter into the decorative grille. For this purpose, the supplier has developed horizontal as well as vertical solutions under the “Evolution Style” concept. Continuously adjustable active grille shutters manage the flow of air to the engine compartment to match requirements. In fast driving the system optimizes the drag coefficient by closing the blades. One or more active grille shutters integrated as part of a body-mounted encapsulation system also actively manages thermal management. The time required for the power train to heat up is shortened and the cooling down of the engine compartment is delayed considerably.

Active Speedlips

The increasing market penetration of the SUV segment is one of the main factors causing effective aerodynamic management to become more and more important. Röchling Automotive has introduced Active Speedlips (ASL) which optimize the air flow in the vicinity of the tires, where the optimization potential increases in step with the size of the front surface of the tire. The speedlips, which were used as passive components up to now, can now be controlled electronically by means of compact actuators developed by Röchling.

To avoid damage caused by obstacles during slow driving, the speedlips are only extended upwards of a speed of 70 kilometers an hour.

Passive wind deflectors cause uncontrolled air turbulences. In contrast, the dynamic, active system causes the head wind – depending on the wind load – to flow closely past the wheel in a controlled way. As a result, the optimized air flow leads to improved fuel consumption and a lower cW value.

Active air dams with self-developed actuators

Wind tunnel tests conducted by Röchling were used to determine the efficiency of a skirt extending across the entire front of the vehicle. Behind a rigid element, a mobile element is extended variably at relatively high speeds via actuator control. This deflects the air flow underneath the vehicle outwards and downwards. Drag, fuel consumption and emissions drop significantly as a result. At the same time, the longitudinal dynamics improve, and this contributes to the fun-to-drive experience. The active air dam also provides further opportunities for the optimization of the driving experience at high speeds.

Many reasons for more functionality

New underbody materials developed by Röchling include self-extinguishing lightweight SyntraliteTM and the lightweight construction material Seralite, which does not burn even when contaminated with highly flammable fluids. Both materials offer low weight and a significant acoustic efficiency.

In the case of Seralite, a hybrid structure made of light metal and LWRT (low weight reinforced thermoplastics) is used. When Röchling Automotive pursued this idea further, it developed Stratura and ultimately of Rabotec. These sandwich structures make the large-series production of light weight, thermoacoustically insulating structural applications possible and affordable, according to Röchling.

The supplier also developed Peralite, an aerodynamically effective underbody for the low-cost-segment ready for production. It provides the basic functions of underbody paneling, and indirectly supports the trend towards increasing the closure of the underbody in the small car segment.

Software filters out the best design

Röchling Automotive has developed software for filter design, which can predict service intervals and performance. Predictions made by the software have a close correlation with the results of field tests.

The simulation software takes regional differences such as local dust levels into account, thus allowing cross-market product development. The program identifies the filter characteristics by accessing manufacturer information such as vehicle data, targets with regard to service life or dust capacity of the filter, as well as information on the medium and specific packaging data such as pleat height and distance between pleats.

The software takes parameters such as filter medium and geometry, dust class and quantity, density, nominal air flow and environmental influences into account in order to determine service life and performance under different conditions. In addition, the software user can define the principal field of application of the filter.

Noise reduction for a smoother sound

Air intake systems for the air in the car interior offer great potential for acoustic optimization, Röchling has developed a new central air distribution manifold for the air conditioning in a middle-class limousine of a large German automobile manufacturer. The lightweight solution has a sandwich structure and allows the air noise at maximum air flow to be improved by 6dB(A) and by up to 10dB(A) in certain frequency ranges. For the upper part of the air conditioning duct, the engineers used the noise-reducing material Seeberlite, which is made of LWRT. The latter is also suitable for use with complex component geometries, and the porosity of 80% in the open core layer allows excellent acoustic characteristics thanks to improved sound absorption, while significantly reducing weight. Other advantages include low pressure losses in the air duct system.

Air intake ducts for the engine also benefit from the Röchling approach. When LWRT is used, an improvement of several decibels is possible with regard to outlet noise, as unpleasant hiss is filtered out by the absorptive material. This means that there is now an interesting lightweight alternative for the high-frequency resonators in the air intake systems which combat annoying turbo noise.

New structure for more comfort

Aluminum profile elements have been included in the multi-layer car body floor made from Stratura. In production, Röchling uses its SoftloftingTM technology to combine two functions. The combination of acoustically and thermally insulating layers in a LWRT sandwich structure together with integrated stabilizing aluminum elements optimizes NVH behavior.

With a field of action which rapidly takes effect upwards of a frequency of 500 Hz, the LWRT material reduces ambient noise significantly. In addition, the low weight multilayer car body floor offers protection against stone chipping and corrosion while also providing very good crash characteristics. This solution’s excellent acoustic properties increase passenger comfort by reducing road noise, according to the company.

Acceleration without sloshing

Röchling Automotive has been presented with an award from the “Society of Plastic Engineers” for its SCR tank design. At the 16th Automotive Award Parts & Components 2015, the company was recognised in the “Power Train” category for its filling system.

Röchling’s design reduces the sloshing noise generated under high acceleration by the urea tanks used in some catalytic reduction systems. Urea is used to transform nitrous oxides in the exhaust gas into nitrogen and water without forming undesired by-products.



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