Η νέα αεροακουστική αεροδυναμική σήραγγα της Mercedes-Benz στο τεχνολογικό κέντρο ανάπτυξης της στη πόλη Sindelfingen, στην Νότιο Γερμανία, πλέον τέθηκε 100% σε λειτουργία. Η σήραγγα χρειάστηκε 5 χρόνια για να κατασκευαστεί πλήρως με την εταιρία να επενδύει σε αυτή 230 εκατ. ευρώ.
Στα εγκαίνια της σήραγγας, η οποία μπορεί να παράγει ταχύτητες έως 265 χλμ/ώρα και έχει συνδεθεί και με την κλιματική αεροσύραγγα, παραβρέθηκε ο πρόεδρος του διοικητικού συμβουλίου της Daimler, Dr. Dieter Zetsche. Πρόκειται για τη πιο προηγμένη και αθόρυβη αεροακουστική αεροδυναμική σήραγγα του κόσμου, αφού ακόμη και με 140 χλμ/ώρα, ο αέρας ρέει μέσα από το τμήμα μετρήσεων, χωρίς να παράγεται ήχος.
Η Mercedes-Benz με την CLA κατέχει πλέον το ρεκόρ του πιο αεροδυναμικού αυτοκίνητου παραγωγής (0,22 Cd). H νέα S300 HYBRID BlueTEC έχει αεροδυναμικό συντελεστή 0,23 Cd, την ώρα που η “απλή S-Class έχει 0,24 Cd. Οι επόμενες γενιές των αυτοκινήτων της Mercedes-Benz, θα επωφεληθούν από τα δεδομένα της νέας αεροδυναμικής σήραγγας, κάνοντάς περισσότερο αεροδυναμικά, που θα έχει ως αποτέλεσμα να είναι και πιο αποδοτικά.
Παράλληλα η Mercedes-Benz ανακοίνωσε πως τον Αύγουστο πούλησε 108.417 αυτοκίνητα (+18,7%), ενώ από την αρχή του έτους 919,644 αυτοκίνητα (+9,3%). Τα 25.562 αυτοκίνητα που πουλήθηκαν τον Αύγουστο ήταν A-, B- και CLA, με τις πωλήσεις της E-Class, να αυξάνονται κατά 29,9%.
Περισσότερες λεπτομέρειες τόσο για την αεροδυναμική σήραγγα, όσο και για τις πωλήσεις, μπορείς να βρεις στο δελτίο τύπου που ακολουθεί.
New aeroacoustic wind tunnel officially opened
Sow the wind and reap efficiency – training centre for world champions
Sindelfingen. With a new aeroacoustic wind tunnel at its development centre in Sindelfingen, the company now once again leads the way in aerodynamic testing. Measurements in the new wind tunnel can be made at wind speeds of up to 265 km/h. All in all, over a period of five years, the sum of more than € 230 million has been invested in extending the facilities of the Mercedes-Benz Technology Centre including the climate tunnel, the driving simulator centre and from now on the aeroacoustic wind tunnel.
“The inauguration of the new aeroacoustic wind tunnel demonstrates once again that the heart of the automotive industry beats in Sindelfingen”, commented Dr Dieter Zetsche, Chairman of the Board of Management of Daimler AG and Head of Mercedes-Benz Cars, who opened the aeroacoustic wind tunnel at an official ceremony together with Günther Oettinger, European Commissioner for Energy. “The future investments made here by Mercedes-Benz will ensure that this remains the case by reinforcing Baden-Württemberg’s status as a high-tech location and safeguarding the company’s technology and innovative leadership in the premium segment.”
The new aeroacoustic wind tunnel is just one element in a comprehensive programme of investment in vehicle development being undertaken at the Sindelfingen site. Joining the climate tunnel taken into operation two years ago, and the driving simulator centre, it rounds off the new test facilities at the Mercedes-Benz Technology Centre. Immediately alongside it, a new technology centre for vehicle safety is also currently under construction.
“Our models are currently the world champions in virtually all vehicle classes as far as aerodynamic and aeroacoustic performance is concerned,” says Professor Dr Thomas Weber, responsible for Group Research and Mercedes-Benz Cars Development. “And world champions need the best training facilities in the world. Exceptional ride comfort thanks to low wind noise, excellent roadholding thanks to low friction and, of course, outstanding efficiency as a result of low wind resistance: our customers enjoy the benefit of all these factors. We realize this innovative high-tech aeroacoustic wind tunnel ensuring that we maintain this leadership position.”
New aeroacoustic wind tunnel is the most advanced facility in the world
Its excellent flow quality, very low background noise levels, sophisticated roadway simulation and high efficiency make the new aeroacoustic wind tunnel at the development centre in Sindelfingen one of the most advanced facilities in the world. It follows the so-called “Göttingen design”, whereby the air is redirected to the blower after the measuring section and then re-accelerated to 265 km/h. With a nozzle system of 28 sq. m this maximum wind speed cannot be reached by any other wind tunnel for cars. Extensive noise insulation measures are integrated to allow use as an acoustic tunnel where interior and exterior wind noise can be measured for the relevant test vehicle. Even at 140 km/h the air flows through the measuring section almost without a sound. These features make it the quietest aeroacustic wind tunnel in the world.
The centrepiece of the almost 20-metre long measuring section of the wind tunnel is the roughly 90-tonne 5-belt-system used to simulate various road conditions perfectly. The integrated turntable with a diameter of twelve metres enables the test vehicles to be subjected to a flow of air from a defined angle in order to simulate crosswinds realistically.
The traversing system enables the engineers to position a variety of aerodynamic sensors and microphones around the test object with a high degree of precision. This is a requirement for very precise aerodynamic measurements and aerodynamic optimization of the vehicles.
World champions for aerodynamics in virtually all vehicle classes
For almost three decades, the aerodynamic specialists at Mercedes-Benz have been breaking one record after another. The current world record is held by the new CLA-Class, in its BlueEFFICIENCY Edition guise, with a Cd value of 0.22 and a wind resistance area of 0.49 sq. m. The drag coefficient of the new S-Class improves on that of its predecessor by a further two hundredths – with a Cd value of 0.24 it not only sets a new benchmark in its segment, but is the best saloon overall in this respect. The S 300 BlueTEC HYBRID is even more aerodynamic. The diesel hybrid model achieves a Cd value of 0.23 and, not least as a result of this extremely low wind resistance, delivers impressive fuel consumption figures of just 4.4 l/100 km, or 115 g/km CO2/km.
The forthcoming generations of vehicles, along with all-new electric and hybrid vehicles from Mercedes-Benz, will continue this trend by being aerodynamically honed in the new wind tunnel. In the case of electric and hybrid vehicles, low wind resistance takes on even more significance, as it has a direct impact on the achievable range per battery charge – while during recuperation too, more energy can be fed back into the battery.
Models from Mercedes-Benz also take the lead in almost all segments when it comes to aeroacoustics. The new S-Class not only offers the lowest level of wind noise in its segment, but is also quieter than that world champion of wind noise, the Maybach, so making it the quietest car overall. As well as the optimised design of the vehicle, significant improvements made to the body shell and to the door seal concept in this model series have been further factors contributing to the reduction in wind noise.
Much ado about wind – a long tradition at Mercedes-Benz
Mercedes-Benz was the first automobile manufacturer to have its own wind tunnel: the “large wind tunnel” in Stuttgart-Untertürkheim. On 5 February 1943 the first documented measurement was carried out there. The wind tunnel in Untertürkheim, which has been in the company’s ownership since the 1970s and was technically updated several times over the years, is still indispensable for the Mercedes-Benz developers, particularly for soiling analyses or windscreen wiper testing. And the “large wind tunnel” more than lives up to its name: for it is here that Mercedes-Benz commercial vehicles are also honed to perfection.
Emotion meets efficiency
Stuttgart. In terms of wind resistance, noise level, open-top motoring comfort and anti-soiling measures, in other words in all aspects of aerodynamics, Mercedes-Benz models have held the top position in practically every vehicle segment for years now. Which just shows that exciting, sensual design and high aerodynamic efficiency are not contradictory concepts. With the new aeroacoustic wind tunnel at the development centre in Sindelfingen, which will be officially inaugurated on 5 September 2013, the company has once again placed itself at the forefront of aerodynamic testing. The new aeroacoustic wind tunnel is just one element in a comprehensive programme of investment in vehicle development being undertaken at the Sindelfingen site. It joins the driving simulator centre brought into operation three years ago as well as the climate tunnel before that. The new technology centre for vehicle safety is currently under construction.
For almost three decades, the aerodynamic specialists at Mercedes-Benz have been breaking one record after another. “Currently, models bearing the three-pointed star take the lead in almost all vehicle classes as far as aerodynamic performance is concerned”, says Professor Dr Thomas Weber, responsible for Group Research and Mercedes-Benz Cars Development. The new S-Class, likewise, heads its segment in terms of aerodynamics and aeroacoustics.
At 0.24, the drag coefficient of the S-Class improves on that of its predecessor by a further two hundredths, so not only setting a new benchmark in the luxury segment, but making the S-Class the most aerodynamically efficient saloon overall. The new S 300 BlueTEC HYBRID has a Cd figure that is another hundredth better, at 0.23. Not least as the result of its extremely low wind resistance, it also achieves an extremely impressive consumption figure of just 4.4 l/100 km or 115 g CO2/km.
Furthermore, when it comes to compact models such as the new A-Class (2012, Cd=0.26), coupés such as the E-Class Coupé (2010, Cd=0.24), saloons such as the E-Class (2009, Cd=0.25), sports cars such as the SL (2012, Cd=0.27) and SUVs such as the M-Class (2011, Cd=0.32), vehicles in these segments have never before achieved such low Cd figures. In its BlueEFFICIENCY Edition guise, the new CLA’s Cd figure of 0.22 and wind resistance area of 0.49 sq m even set a new world record.
“This good performance can be attributed to some highly sophisticated improvements to the vehicle as a whole, as well as to careful work on the details”, explains Dr Teddy Woll, Head of Aerodynamics/Wind Tunnels. Emotion meets efficiency: the more aerodynamic a car is, the lower its consumption will be. Woll: “In the New European Driving Cycle (NEDC), improving the Cd figure by 0.01 already lowers CO2 emissions per km by one gram, by two grams as a function of mean on-the-road consumption, and at 150 km/h by a full five grams of CO2 per kilometre.” Eliminating irritating wind turbulence, however, also brings benefits in terms of safety, comfort and the environment. Reduced lift improves road holding, while low wind noise spares the nerves of both passengers and passers-by. Models from Mercedes‑Benz also take the lead in almost all segments when it comes to aeroacoustics. The new S-Class, too, not only offers the lowest level of wind noise in its segment, but is also quieter than the previous world champion of wind noise, the Maybach, so making it the quietest car overall.
New aeroacoustics wind tunnel: measurements up to 265 km/h
With its “large wind tunnel” in Stuttgart-Untertürkheim – the first measurement was recorded precisely 70 years ago, on 5 February 1943 – Mercedes-Benz was the first automotive manufacturer to have its own wind tunnel. The new aeroacoustic wind tunnel at the development centre in Sindelfingen once again puts the company at the forefront of aerodynamic testing. The new wind tunnel, which will be officially inaugurated on 5 September 2013, follows the Göttingen design, whereby the air is redirected to the blower after the measuring section and then re-accelerated to 265 km/h. Before the air accelerated by the blower reaches the measuring section, via a nozzle system that encompasses 28 sq m, it must be straightened and smoothed to eliminate unwanted turbulence and eddies. This is done using rectifiers and sieves. Extensive noise insulation measures are integrated to allow use as an acoustic tunnel where interior and exterior wind noise can be measured for the relevant test vehicle. Even at 140 km/h the air flowing through the measuring section is therefore as quiet as a whisper.
The centrepiece of the 19-metre long measuring section in the wind tunnel is the roughly 90-tonne conveyor belt/balance system with turntable. The new wind tunnel has a 5-belt system to simulate the road. The conveyor belt/balance system is integrated into a turntable with a diameter of twelve metres, which means that the test vehicles can also be subjected to an angled flow of air in order to simulate cross-winds. The traversing system enables the engineers to position a variety of aerodynamic sensors and microphones around the test object with a high degree of precision.
Taking the drag out of aerodynamics
Aerodynamics world champion in almost all vehicle classes
For almost three decades, the aerodynamic specialists at Mercedes-Benz have been breaking one record after another. At present the brand’s models occupy the top position for aerodynamics in practically every vehicle segment. Models from Mercedes-Benz also take the lead in almost all vehicle categories when it comes to aeroacoustics.
A whole series of refinements go into achieving these record figures each time. The following aerodynamic improvements, for example, are among those to feature on the new S-Class:
- Aerodynamically optimised front and rear apron with perfectly matched rear spoiler
- All-new aerodynamically and aeroacoustically optimised exterior mirrors
- Complete sealing of the front end with sealing of the headlamp section, improved sealing of the radiator section and air-flow guidance to make efficient use of the available cooling air
- Use of a cooling air metering system (adjustable louvre)
- Streamlined water drainage channels
- Lowering the vehicle by up to 20 mm over 120 km/h
- Spoiler lip in the rear lights
- Aerodynamically optimised underbody with extensive engine compartment and underbody panelling up to a point below the tank, also further minimising the penetration of road noise
- Aerodynamically shaped multifunction recess cover
- Special wheel spoilers at the front wheels
- Aerodynamically optimised wheels and tyres
- Large area of cladding on the rear axle
Furthermore, when it comes to compact models such as the new A-Class (2012, Cd=0.26), coupés such as the E-Class Coupé (2010, Cd=0.24), saloons such as the E-Class (2009, Cd=0.25), sports cars such as the SL (2012, Cd=0.27) and SUVs such as the M-Class (2011, Cd=0.32), vehicles in these segments have never before achieved such low Cd figures.
An overview of the key aerodynamic figures for the entire Mercedes-Benz passenger car range:
|Model series||Cd figure||Frontal area (A) sq m||Wind resistance (Cd x A) sq m|
|A-Class||0.27BEE: 0.26||2.20BEE: 2.20||0.59BEE: 0.57|
|CLA-Class||0.23BEE: 0.22||2.21BEE: 2.21||0.51BEE: 0.49|
|S-Class||0.24S 300 BTH: 0.23||2.46||0.59/0.56|
BEE = BlueEFFICIENCY Edition Model, 1 Saloon/Coupé/Estate, 2 Saloon/Coupé/Estate/Cabriolet, 3 Coupé/Shooting Brake, 4 Coupé/Roadster
More driving comfort thanks to less wind noise: aeroacoustics
Models from Mercedes-Benz also take the lead in almost all segments when it comes to aeroacoustics. The new S-Class, for example, offers the lowest level of wind noise of any vehicle on the market.
To reduce high-frequency wind noise, the sealing system for the windows and door handles has been considerably improved. In addition, the new exterior mirrors and correspondingly designed A-pillars with a minimised upstand for the carefully directed drainage of dirty water prevent the air flow from separating at these points, and therefore noises that might penetrate into the interior via the windscreen and side windows. The roof structure and the sliding sunroof module have been aeroacoustically improved to benefit noise comfort in these areas too. In the case of the panoramic sliding sunroof, multiple wind-deflection measures (wind deflector, covers and seals with the appropriate geometry) ensure the same high level of noise comfort as in the preceding model, despite the larger aperture. The sum of these measures enables the new S-Class to meet its aim of being the quietest car around.
A subdued, scarcely perceptible level of noise in the interior of the S-Class was the objective when configuring and coordinating the sound insulation measures. Particular attention was paid to transmitted engine noise and road roar. During the acoustic optimisation work, the focus was both on lowering the sound pressure level and on achieving the well-balanced and comfortable overall sound perception that is a hallmark of the S-Class.
To ensure that engine noise is perceived as refined and unobtrusive in the interior, the firewall insulation was extended into the side areas of the A-pillars. Additional sealing layers were also added in the form of high-quality injection-moulded components.
A major contribution to the reduction in transmitted engine noise was made by improved insulation in the transmission tunnel area, as well as a modular engine partition made of plastic. The different noise characteristics of the engines are taken into account by the use of different weights per unit area.
The electrically adjustable rear seats, available as an optional extra, are free-standing. High-frequency tyre noise has been reduced by means of a large area of insulation extending from the seat surface to the rear panel and parcel shelf. Breakthroughs have also been kept to a minimum. An intelligent air ducting system inside the parcel shelf allows the necessary ventilation, while also reducing the intrusion of noise via the parcel shelf. The textile underbody and wheel arch cladding have an insulating and absorptive effect which reduces high-frequency tyre noise in the interior.
Contribution to active safety: anti-soiling measures
Anti-soiling measures are another aerodynamic discipline – and another area in which the aerodynamic specialists at Mercedes-Benz have led the field for many years. Soiling can arise from rain, vehicles travelling ahead or from spray thrown up by the vehicle’s own wheels. Keeping windows and exterior mirror lenses as clean as possible, and therefore having the best possible visibility under all conditions, makes a contribution to active safety.
In the wind tunnel the aerodynamic specialists optimise components with the help of a fluorescent liquid which makes the soiling clearly visible. The aim is to direct water away so that the side windows and exterior mirror lenses remain clean. This is influenced by the geometry of the A-pillar with its integral components and the geometry of the exterior mirrors and window frames, or trim strips in the case of frameless doors.
Take the example of the side windows: a series of minor geometric modifications to the mirror housing, detailed refinements involving seals, plus a special water runnel, all help to reduce the build up of dirt significantly. The standard set by Mercedes-Benz defines that within the so-called core visibility area, no spray, no trickles but only isolated drops of water should appear on the mirror lens.
The basis for efficiency and comfort
The more aerodynamically efficient a vehicle is, the lower its fuel consumption. Moreover, safety, comfort and the environment also benefit from the elimination of air turbulence, since low levels of lift ensure good roadholding, while low wind noise is welcome to both passengers and pedestrians. And open-top driving in comfort is a particular speciality of the aerodynamicists at Mercedes-Benz.
In 1984, the E-Class (W124 model series) achieved an aerodynamic landmark, posting a Cd figure of 0.29. It became, and remains, the benchmark against which all saloons must measure themselves – and one that very few manage to match. Design elements such as smooth surfaces, an inwards-drawn rear end and a clear spoiler lip on the boot lid remain at the heart of good aerodynamic design to this day.
Since then the aim has been to shave down the second number after the decimal point of the Cd figure. In the New European Driving Cycle (NEDC), improving the Cd figure by 0.01 already lowers CO2 emissions per km by one gram, by two grams as a function of mean on-the-road consumption, and at 150 km/h by no less than five grams of CO2 per kilometre. Or, as Dr Teddy Woll, Head of Aerodynamics at Mercedes-Benz, puts it: “If we succeed in lowering the Cd figure by ten thousandths, the fuel consumption drops by one tenth of a litre across the customer average, and by up to 0.4 litres per 100 kilometres at very high motorway speeds. To achieve the same savings effect with lightweight-construction measures, the weight of our cars would have to be reduced by at least 35 kilograms.”
The focus is therefore on the dimensionless drag coefficient – the Cd figure: this is the measure of the aerodynamic efficiency of a solid body, and therefore of an automobile. The Mercedes-Benz CLA has the lowest of all Cd figures, at 0.23 – both within the Mercedes-Benz model portfolio and amongst all series production cars. The CLA 180 BlueEFFICIENCY Edition improves upon this benchmark even further, with a Cd figure of 0.22.
The Cd figure alone is not what decides the wind resistance. The second determining factor is the vehicle’s frontal area, the cross-sectional area facing the air flow. In the past, the frontal area was calculated by projecting the shadow of the body onto a transparent screen using a lamp positioned some considerable distance away. The outline was then traced, and the overall area calculated on the basis of the individual segments. Nowadays the frontal area is scanned using laser light barriers.
But since cars are becoming increasingly wider and higher, e.g. for reasons of comfort, the hands of the aerodynamic specialists are more or less tied in this respect. The wind resistance as a measure of the efficiency with which a vehicle passes through the air is calculated as the product of the drag coefficient and the vehicle’s frontal area. As the coefficient is dimensionless, the wind resistance is indicated in square metres.
In the case of the aerodynamics world champion, the CLA, this means that the drag area Cd x A is also the benchmark at 0.51 sq m, well below that of many subcompact cars. In its CLA 180 BlueEFFICIENCY Edition version it even betters this figure: at just 0.49 sq m the wind resistance of the four-door coupé breaks through a magic barrier.
No rising to the occasion: reducing aerodynamic lift
As all motor racing fans know, aerodynamics also have a major influence on driving characteristics, especially at higher speeds. This is because the air flowing around the vehicle body can have the undesirable tendency to generate lift. What makes aircraft able to rise into the air is understandably unwanted for automobiles. Aerodynamic optimisation therefore not only means reducing the wind resistance, but also generating as little lift as possible. The deciding factor is not only the absolute figures for the front and rear axles, but the achievement of the best possible harmonisation between these front and rear values. The driving characteristics at high speeds are not changed by addressing one factor alone.
Peace and quiet: acoustic optimisation right from the start
Wind noise is another discipline of aerodynamics. Key requirements for a low wind noise level in the interior include draughtproof door and window seals. This requirement applies especially to cars with frameless side windows.
But the seals are in fact only the second step. Increasing priority is given during the development phase to the search to identify and eliminate the sources of wind noise, for example around the exterior mirrors or at the transitional points where the bonnet meets the windscreen and the windscreen the roof.
Measuring tools such as dummy human heads and directional microphones enable even the slightest weak spots to be pinpointed. These can then be eliminated by implementing the best possible technical solutions. At a very early stage in the development of the new E-Class Coupé, for example, a three-metre concave acoustic mirror was used to optimise the exterior shape of the A-pillars and the shape of the exterior mirrors in the wind tunnel.
Maximum visibility even in the rain: aerodynamics keep the field of vision clear
The battle for clear visibility is another area of activity for the wind tunnel specialists. The aim is to direct the air flow in such a way that a clear view through the side windows and of the exterior mirrors is ensured even in murky weather conditions. During the relevant tests, fluorescent water droplets are made visible under UV lighting, making it possible to ascertain the path taken by the soiling at different speeds. To avoid inflicting soiling tests on the highly sensitive measuring equipment and moving belts in the new acoustic wind tunnel in Sindelfingen, these will continue to be conducted in the large wind tunnel at the plant in Stuttgart-Untertürkheim.
Special case: open-top driving in comfort
No manufacturer has such a long and unbroken tradition of vehicles with no fixed roof as Mercedes-Benz. Convertibles and roadsters have been part of the company’s model range for very many years, and offer driving pleasure in its most emotionally appealing form. Nowadays however, customers want a choice of whether to feel the wind full in their faces or enjoy the fresh air with as little draught as possible. For this particular form of refined sportiness, Mercedes-Benz customers currently have a choice between four product lines: the SLK, SL, SLS AMG and E-Class Cabriolet.
With the introduction of the draught-stop as a world first in the SL model of 1989, Mercedes-Benz for the first time provided an aerodynamic remedy to the blast of air into the cockpit. The next step was the 2004 debut of AIRSCARF in the SLK. With this patented neck-level heating system, warmed air circulates around the head and neck areas of the occupants from the head restraints.
The most extensive package of comfort-enhancing aerodynamic measures has been available since 2010 with the E-Class Cabriolet, which is available with the automatic draught-stop AIRCAP. This can be activated at the push of a button in order to reduce significantly interior turbulence in the open-top four-seater. AIRCAP consists of two components: a wind deflector with a net, set into the roof frame, which can be extended by six centimetres, plus a similarly extendable draught-stop between the rear seats.
The new aeroacoustic wind tunnel
New tool in the battle against wind resistance and wind noise
With its now more than 70-year-old wind tunnel in Stuttgart-Untertürkheim, Mercedes-Benz was the first automobile manufacturer to possess a wind tunnel. The new aeroacoustic wind tunnel at the development centre in Sindelfingen once again puts the company at the forefront of aerodynamic testing.
As a measure of the company’s confidence in the future, the go-ahead for the construction of the new Mercedes-Benz aeroacoustic wind tunnel was given in 2008 – in the middle of the most severe economic crisis for decades. This means that from September 2013, Mercedes-Benz developers will for the first time have the necessary facilities on hand at the passenger car development centre in Sindelfingen. Joining the climate tunnel taken into operation two years ago and the new driving simulator centre, this rounds off the new test facilities at the Mercedes-Benz Technology Centre and strengthens the development potential of Mercedes-Benz in Germany. Immediately alongside it, a new technology centre for vehicle safety is also currently under construction.
Blower: wind speed of 265 km/h, 5 MW output
The new wind tunnel follows the Göttingen design, whereby the air is redirected to the blower after the measuring section and then re-accelerated, so saving a great deal of energy. The blower has a diameter of nine metres and has 18 vanes which set the air into motion. At 202,150 Nm, the maximum torque of the electric drive motor is approx. 1000 times that of a powerful vehicle. At a wind speed of 250 km/h the power consumption is five megawatts. At this point the blower is rotating at 238 rpm, while the volume of air passing through it is 2000 cubic metres, or around three family houses, per second. The maximum wind speed is 265 km/h.
The air temperature in the wind tunnel is kept at a constant 23 to 24°C. To ensure that measurements are precise even in wintry outside temperatures, the concrete shell of the tunnel is surrounded by an outside wall and therefore insulated. During operation, the drive motor of the blower heats up the air circulating within the wind tunnel. In warm outside temperatures it is therefore cooled by a heat exchanger located downstream of the blower.
Before the air accelerated by the blower reaches the measuring section, via a nozzle system that encompasses 28 sq m, it must be straightened and smoothed to eliminate unwanted turbulence and eddies. This is done using rectifiers and sieves.
Extensive noise insulation measures are integrated to allow use as an acoustic tunnel where interior and exterior wind noise can be measured for the relevant test vehicle. Even at 140 km/h the air flowing through the measuring stretch is therefore as quiet as a whisper
Measuring stretch: five conveyor belts up to 265 km/h
The centrepiece of the 19-metre long measuring section in the wind tunnel is the roughly 90-tonne conveyor belt/balance system with a turntable. The new wind tunnel has a 5-belt system to simulate the road: a small conveyor belt runs under each wheel, and a central belt with a length of nine metres and a width of over one metre runs between the wheels. All five belts are synchronised with the wind, so that up to 265 km/h they exactly simulate the road conditions. The 24-tonne balance on which the vehicles are fixed in place is extremely sensitive, with a weighing precision of a few grams. Even the measuring cables must be routed so that they do not introduce extraneous forces into the system. The values obtained with the help of the aerodynamic balance are used as the basis for calculating the coefficients of wind resistance, lateral forces and lift at each axle, as well as the pitching, rolling and yawing moment.
The conveyor belt/balance system is integrated into a turntable with a diameter of twelve metres, which means that the test vehicles can also to be subjected to an angled flow of air in order to simulate cross-winds. The turntable also allows the vehicles undergoing testing in the measuring section to be exchanged rapidly. The test vehicles are prepared in workshops within the wind tunnel building, immediately adjacent to the measuring section. All in all, great attention was paid to facilitating a rapid exchange of test vehicles, so that the wind tunnel can be used as effectively as possible.
Traversing system: precise measurements even at 265 km/h
The traversing system enables the engineers to position a variety of aerodynamic sensors and microphones around the test object with a high degree of precision, so that pressure, acoustic and speed measurements are exact. The system in the new Sindelfingen wind tunnel has seven axes (three translation [parallel movement] and four rotation axes), enabling it to cover a measuring volume of 19 x 14 x 5 metres. The weight of this system is 26 tonnes, as the measuring sensors must remain exactly in place with no vibrations even at the maximum wind speed.
In addition to advanced computer simulation programmes, Mercedes-Benz now has all the facilities required to further consolidate its leading position in aerodynamic efficiency and further improve the acoustic comfort of its vehicles. Dr Teddy Woll, head of the Aerodynamics/Wind Tunnels department at Daimler AG, explains: “Computers and wind tunnels are outstanding tools that complement each other perfectly: using numerical flow calculations we are able to examine very complex air-flow phenomena and follow even the smallest turbulence back to its source. And in the wind tunnel we are able to test a large number of variants very rapidly – which means that one day in the wind tunnel can often lead to major improvements both outside and inside the vehicle.”
Interview: Dr Teddy Woll, Head of Aerodynamics
“We fight for every third decimal place”
Dr Teddy Woll, 50, has headed the Aerodynamics/Wind Tunnels department at Daimler AG since April 1999. We spoke to this doctor of industrial engineering about efficiency improvements and air flow simulation.
Dr Woll, for years Mercedes-Benz has been establishing new aerodynamic records with practically every new model series. Does further progress become increasingly difficult as Cd figures get smaller?
You are absolutely right. It is quite true that we are gradually approaching an asymptotic limit if we do not dramatically change the appearance of our cars, e.g. by making them much longer and sleeker, and equipping them with slim rear ends and narrow wheels. Fortunately, however, we can still find details where improvements are possible — both in the wind tunnel and, increasingly often, on the computer. Moreover, aerodynamic optimisation of our vehicles is one of the core strategies in the “Real Life Efficiency” philosophy of Mercedes-Benz. The importance attached to our work within the conflicting aims in car development is therefore correspondingly high throughout the company, and our proposals are often incorporated into our vehicles accordingly. Nonetheless, we continue to fight for every third decimal place in our daily work.
You have just mentioned a key term, Real Life Efficiency’. How do Mercedes drivers benefit from this battle for the third decimal place?
It’s a very simple calculation: if we are able to reduce the Cd figure by ten thousandths, fuel consumption across the customer average falls by one tenth of a litre, and at very fast motorway speeds by up to 0.4 litres per 100 kilometres. To achieve the same saving with lightweight-construction measures, we would have to reduce the weight of our cars by at least 35 kilograms.
In what areas of the car have you achieved the greatest progress in recent years?
There are three areas: the air flow through the engine compartment, the air flow around and within the front wheels, and the underbody. In the front wheel arches of the new compact models alone, for example, we have been able to make improvements of eleven thousandths thanks to the combined effect of serrated wheel spoilers, slits in the wheel arches and optimised aero-wheels. But we take a close look at every nook and cranny of the vehicle, from the front apron with all its edges and apertures to the small spoiler lips in the lenses of the tail lights, to perfect the breakaway of the air flow at the rear.
What technological developments help you with your aerodynamic improvements?
In recent years we have made great progress thanks to the digitisation of the development process, as calculations are very much faster and much more refined. Digital vehicle models nowadays have over 50 million cells, and if necessary they can already produce results overnight. Ten years ago, the same simulation would have taken 6 months and would not have been half as precise.
In the mid-term, will numerical air flow simulation replace the classic wind tunnel with its smoke trail?
No, computers and wind tunnels are outstanding tools that complement each other perfectly: using numerical flow calculations we are able to examine very complex air flow phenomena and track even the smallest turbulence (e.g. in the wheel arch as mentioned above) back to its source, and try to eliminate it. In the wind tunnel we are then able to try out a large number of variants, which are measured down to half a thousandth. Which means that one day in the wind tunnel can often lead to major improvements both outside and inside the vehicle.
What exactly is a numerical air flow simulation?
This has meanwhile become almost as precise as a wind tunnel. Where wind resistance is concerned, we have an error rate of less than one percent compared with the results from the wind tunnel, though the error is marginally greater for aerodynamic lift depending on vehicle type. We hope to improve our precision even further by the improved modelling of turbulence.
How far advanced is simulation for aeroacoustics?
Wind noises are a highly complex phenomenon: apart from the air flow, the noise source and noise transmission must be adequately represented, and this is a major challenge in view of the different levels and wavelengths of turbulence and sound. This is compounded by noise transmission to the driver’s ears via a wide variety of materials such as sheet metal, glass, rubber and plastics, which makes it extremely difficult to model the entire frequency range. I expect that it will be years before we are able to simulate wind noises reasonably well by computer. We hope that the new aeroacoustic wind tunnel with its new high-tech equipment will enable us to understand such complex inter-relationships even better.
An aerodynamics engineer must nowadays have a perfect grasp of computer tools. Are there other core qualifications?
Yes. Of course experience also still plays an important role, while “soft skills” such as a talent for communication and teamwork are also significant factors. Because if there is a conflict of interest, as I mentioned before, perhaps with the Design team or one of the other functional areas, the important thing is to talk about these things together and not against one another, in order to reach the ideal solution.
Under the microscope: the development of aerodynamics
From the K-rear to the S-Class
Aerodynamics first became a focus of scientific research almost 100 years ago – but it was only after the second oil crisis some 30 years ago that it was given priority in vehicle development. Nowadays aerodynamics make a major contribution to the energy efficiency of passenger cars.
The first passenger cars were not only derived from the horse-drawn coach, they were also not in the least concerned about wind resistance because of the low speeds that were possible. Even the first “real” cars marketed by Daimler under the Mercedes brand from 1901 presented all manner of resistance to the rush of oncoming wind. The Mercedes Simplex of 1902, for example, not only had a frontal area of around 3 sq m – its Cd figure of 1.05 meant that the wind encountered almost ten times the resistance offered by a modern passenger car.
Shortly after the First World War, specialists inspired by advances in the world of aviation began to examine the aerodynamics of automobiles. In 1921 the aircraft designer Eduard Rumpler (1872 – 1940) presented his “teardrop car”, whose slim bodywork not only addressed the problem of frontal area (2.4 sq m), but whose teardrop shape broke new ground in minimising air turbulence both at the front and especially behind the rear. The result looked unusual, but was a highly significant advance with its Cd figure of 0.28 and the resulting wind resistance of 0.67 sq m.
Paul Jaray (1889 – 1974), the other “father of streamlining”, also came from the world of aviation. In 1921 he registered a patent which still reads like a list of instructions for building a modern passenger car body: “The lower half of the vehicle body takes the form of a streamlined construction covering the chassis with the wheels, engine compartment and passenger compartment. Its underside is smooth and runs parallel with the ground. This main structure carries a considerably slimmer streamlined construction supported by a lattice-like frame likewise mounted on the chassis.” For the first time the wheels were no longer exposed, but were integrated into the bodywork, while the “fastback” rear end minimised turbulence in this area. As conventional drive technology could be incorporated into Jaray’s body form, a number of car manufacturers built vehicles following the same principles – including Mercedes-Benz, which built a corresponding prototype in 1935. In series production Tatra had a measure of success with streamlining, starting with the Model 87 produced from 1936 to 1950. The VW Beetle also had a streamlined appearance, though with no effect: with a Cd figure of 0.49, it crawled rather laboriously into the wind.
The greatest disadvantage of Jaray’s streamlining was the long, tapering rear end – the longer, the more aerodynamically efficient. This “dead” space was an obstacle to practical implementation, which is why Tatra placed the engine there. In the 1930s the solution was found by Wunibald Kamm (1893 – 1966), the first professor of automobile engineering at the Technical University of Stuttgart and founder of the private, non-profit-making research institute for automobile engineering and vehicle engines (FKFS) in Stuttgart in 1930. Kamm abruptly cut off the streamlined rear end to create the “K-car”, developed between 1938 and 1941, as a prototype for an aerodynamically innovative passenger car. The term “Kamm rear” is still in use to denote an air-flow breakaway edge at the rear. The K3 car was based on a Mercedes-Benz 170 V, and excelled with a frontal area of 2.1 square metres and a Cd figure of 0.23.
In the 1950s, increasing affluence and falling fuel prices caused efforts to reduce aerodynamic drag to fade into the background, with performance achieved by large-capacity engines. While the classic, large fintail sedans of this era used a feature familiar from aircraft engineering, this was only for decoration: with Cd figures of around 0.60 and large frontal areas, they were about as streamlined as Elvis Presley’s Graceland mansion.
It was only the second oil crisis in 1980 that drew the industry’s attention back to minimising fuel consumption, and to an effective means of achieving this: lowering the wind resistance. Audi achieved some initial success with the 100 in 1982 (Cd = 0.30), in 1984 Mercedes-Benz took the lead for saloon cars with the W124-series E-Class (Cd = 0.29), and in 1991 Opel’s Calibra showed what is possible for a coupé (Cd = 0.26).
Despite certain contrary factors (e.g. increasing tyre widths and the greater cooling requirement of powerful engines) there has been a downward trend in wind resistance since then. Especially at Mercedes-Benz, which now leads the industry in practically all vehicle segments with respect to wind resistance and the other aerodynamic disciplines (see the chapter “Aerodynamics world champion in almost all vehicle classes”).
A milestone: the “large wind tunnel” in Stuttgart-Untertürkheim
The date of 5 February 1943, exactly 70 years ago, marks the first recorded measurement: Daimler AG’s “large wind tunnel” at its parent plant in Stuttgart-Untertürkheim was the first in the world to be designed specifically for analysing the aerodynamic properties of motor vehicles. Building work began in 1940, with the legendary aerodynamics pioneer Wunibald Kamm the driving force behind the project.
Because of the war, it was not until 1954 that the wind tunnel became the first in the world to be used regularly for measurements on full-size passenger cars. Since then it has played a key role in developing the aerodynamic efficiency of the car – especially models bearing the Mercedes star. But not exclusively: up until the 1970s, the wind tunnel was operated by FKFS, an independent institute, and was therefore available for general research as well as being open to other manufacturers. Daimler, the current owner, was one of the most frequent hirers – much as is the case with the new FKFS wind tunnel on the university campus in Stuttgart-Vaihingen, which went into operation in 1988 and will be thoroughly overhauled in 2014.
Yet the wind tunnel in Untertürkheim, which has been repeatedly technically updated, is still indispensable for the Mercedes-Benz developers, particularly for soiling analyses or windscreen wiper testing. Furthermore, the “large wind tunnel” more than lives up to its name, for it is here that Mercedes-Benz commercial vehicles are also honed to perfection.
As well as hosting these tests, the facility is also often used for completely unrelated activities: ZDF, Germany’s second TV channel, has shot film sequences for a hurricane report here; bobsleighs are optimised here; and speed skaters perfect their technique here. In short, anyone who has to work with or against the wind is welcome in Untertürkheim. Another major challenge faced here was the aerodynamic testing of the revolutionary roof for Munich’s Olympic Stadium.
Mercedes-Benz posts strongest August performance ever with 18.7% growth
Stuttgart – Last month, Mercedes-Benz sold 108,417 vehicles, which is more than in any other month of August to date. Since the start of the year, the brand grew its unit sales by 9.3%, reaching a new record of 919,644 units. Thus Mercedes-Benz grows faster than any other premium brand.
Strong growth in August was ensured primarily by the new E-Class with a sales plus of 29.9%. The compacts and SUVs from Mercedes-Benz continued to post strong increases.
In nearly all markets of Europe Mercedes-Benz reported double-digit growth rates and gained market shares in August. In August, Mercedes-Benz again saw double-digit growth in the USA and China (incl. Hong Kong). In Germany, the USA and Japan, the Mercedes-Benz continued to be the most registered premium manufacturer since the beginning of the year.
“We again posted double-digit growth with over 18 percent in August and are thus continuing on our growth course for the second half of the year, in which we want to grow more strongly than in the first”, said Dr Joachim Schmidt, Executive Vice President, Sales and Marketing Mercedes-Benz Cars. “The offensive in the compact car and luxury segment continues: We have launched the new S-Class in Europe successfully and will already be starting production of the GLA at the end of the year.”
In Europe, Mercedes-Benz delivered 43,523 vehicles to customers in August, this is12.0% more than in the same month of the previous year. The brand with the star gained market shares in almost all markets and is thus the fastest growing premium manufacturer in Europe. The Stuttgart-based automotive manufacturer posted particularly high sales increases in the UK (+29.3%), Belgium (+20.9%), Russia (+21.5%) and Turkey (+65.7%). Mercedes-Benz also posted a strong increase in the declining domestic market (total market -5.5%): At 21,376 units the brand sold 11.5% more vehicles in August than in the same month of the previous year, reaching a double-digit market share (10.5%). Mercedes-Benz is thus the premium manufacturer with the most registrations in Germany once again.
August sales in the USA increased by 20.5% to a new record high (24,761 units). With this, Mercedes-Benz is once again the premium brand with the highest sales since the beginning of the year (190,359 units). Moreover, Mercedes-Benz also posted new sales records in Canada (+20.6%) and Mexico (+14.6%). Vehicle deliveries in Latin America increased by 32.6%.
In the Asia-Pacific region the Stuttgart-based company sold 28.6% more vehicles in August than in the same month of the previous year. Sales in Japan grew by as much as 37.0% to a new record high. In China (incl. Hong Kong) Mercedes-Benz delivered 18,087 vehicles to customers, an increase of 27.3%.
Mercedes-Benz sales of the A-, B- and CLA-Class in the last month totaled 25,562 units and the company posted an 84.8% jump in its sales of compact vehicles. Moreover, in the months ahead even more drive will come from the USA, where the CLA will be launched in September. It is the first vehicle from the compact class of Mercedes-Benz on the U.S. market. The fourth model of the compact car family, the GLA, will celebrate its world premiere at the Frankfurt International Motor Show next week and will be inspiring new customers for the brand beginning in 2014.
Last month, the C-Class celebrated an anniversary: Since its launch on the market in 1982, Mercedes-Benz has delivered over 10 million vehicles of the C-Class family to customers. Initially known as the Baby-Benz, the C-Class sedan in particular is one of the most sought-after vehicles in the premium segment.
Sales of the new models in the E-Class segment grew strongly in August. Mercedes-Benz sold 29.9% more units of the sedan and estate than in the same month of the previous year (19,525 units). Sales of the new coupe and cabrio even jumped by 39%. Since last weekend, the new Mercedes-Benz E-Class is now also available in China and is thus present in all major markets. The long version of the luxury sedan was developed especially for the Chinese market.
Whether SL, E-Class coupe or CLS – all dream cars from Mercedes-Benz were at the top of the registration lists worldwide in August. “Dream cars” is the general term employed by the brand for its coupes, cabrios and roadsters. In comparison with the German core competitors, the Mercedes models reached a market share of about 50%. Overall, since the beginning of the year, 108,499 dream cars from Mercedes-Benz have been delivered to customers.
Since the start of the year, 65,256 customers (PY 69,736 units) have opted for a smart fortwo, which was especially popular in the USA (+31.9%), Canada (+40.9%) and China in August (+27.7%). China is meanwhile the third largest market for the compact two-seater. In July and August, production at the smart plant in Hambach was halted to enable the required conversion work for the successor generation. At the Frankfurt International Motor Show, smart will give a preview of the new four-seater of the brand with the smart fourjoy, which will be coming onto the market in 2014 as does the two-seater.
Overview of sales by Mercedes-Benz Cars
Change in %
|Per August 2013||
Change in %
|Mercedes-Benz Sales in the Markets||
|– thereof Germany||
|– thereof USA||
|– thereof Japan||
|– thereof China||