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DaimlerChrysler Showcases 70 MPG “Bionic” Diesel Concept

7 June 2005

DaimlerChrysler has unveiled a new “bionic” concept car that achieves outstanding results for fuel consumption and emissions with a combination of diesel engine technology, innovative emission control methods and aerodynamic design inspired by a natural example.

The Mercedes-Benz bionic car seats four, delivers better than 70 mpg in the US test cycle and exceeds Euro 4 emissions standards. It is premiering at the DaimlerChrysler Innovation Symposium in Washington.

Bionics is an inter-disciplinary subject which combines engineering science, architecture and mathematics. The basic principle is to understand nature’s ideas and problem solutions, which have stood the test of time over millions of years of evolution, and to adopt them for human use.

The design engineers looked for a specific design example in nature that could map to an aerodynamic, safe, comfortable and environmentally compatible car not just in terms of details, but as a formal and structural whole. The model they chose was the boxfish.

Dcxbionic0 Dcxbionic1_1
The boxfish. The DCX Bionic Car.

Despite its boxy, cube-shaped body, this tropical fish is in fact outstandingly streamlined. With an accurately constructed model of the boxfish, the engineers in Stuttgart were able to achieve a wind drag coefficient of just 0.06 in the wind tunnel.

Specialists at DaimlerChrysler first created a 1:4 car model whose shape was substantially based on the boxfish. During tests in the wind tunnel, a drag coefficient of 0.095—a previously unprecedented value in automotive engineering—was measured for this clay model.

DaimlerChrysler utilized the findings from this research in designing it concept car, which offers a Cd value of just 0.19—among the most aerodynamically efficient in this size category.

The car uses a 4-cylinder, 2-liter common rail diesel that delivers 103 kW (140 hp) of power and 300 Nm torque.  In the EU driving cycle the concept car has a fuel consumption of 4.3 liters per 100 kilometers (55 mpg US)—20% less than a comparable series-production car.

Measured using US testing procedure, the car offers approximately 70 mpg (3.4 liters/100km), about 30% better than for a standard-production car.

At a constant speed of 90 km/h (56 mph) the direct-injection diesel unit consumes only 2.8 liters per 100 kilometers, corresponding to 84 miles per gallon US.

The car uses DaimlerChrysler’s Selective Catalytic Reduction (SCR) technology—more widely used in the commercial vehicle sector—to reduce NOx emissions. This aftertreatment sprays an aqueous urea solution into the exhaust system in precisely metered quantities, depending on the engine operating status. The reaction converts the nitrogen oxides into nitrogen and water.

The process requires a separate reservoir for this service fluid, which, in the concept car, is located in the spare wheel recess, and offers enough capacity to last a typical service interval for a Mercedes diesel.

(As an aside, Ford also used an SCR system in its Meta One diesel-hybrid concept car. Earlier post.)

DaimlerChrysler will initially offer passenger car SCR technology in the US when its trials have been completed.

Mercedes-Benz Bionic Diesel Concept
Length / Width / Height (mm) 4,243 / 1,815 / 1,594
Wheelbase (mm) 2,568
Displacement 1,991 cc
Engine Power 103 kW (140 hp)
Torque 300 Nm (221 lb-ft)
Fuel cons. (Euro) 4.31 l/100km (55 mpg US)
Fuel cons. (US) 3.4 l/100km (70 mpg US)
Acceleration 0–100km/h 8.2 sec
Maximum speed 190 km/h (118 mph)
Cd 0.19

June 7, 2005 in Diesel, Emissions, Fuel Efficiency | Permalink | Comments (35) | TrackBack (2)

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Comments


Can I get one with the Black spots on it?

The real test will be if the marketing dept. can convince people that this vehicle is so dorky looking it's actually cool.

All snarky comments aside, this really is a very impressive piece of engineering. I think it shows beyond doubt what current technology can do when the design begins with a strong dedication to fuel efficiency.

Get this thing on the road running biodiesel! MB - stop teasing us with one-offs and prototypes. Give the Prius some competition in the USA!

-mt

That is one UGLY piece of crap. For once im GLAD that a concept car wont make it to market!

Now this very bright fellow I know tells me that the drag coefficient, while useful for airplanes, is a fairly useless measurement for ground vehicles:

"Aha - the deceptive drag coefficient."

"Actually it's a useless number for cars - and fortunately discarded as a meaningful measure many years ago by most car manufacturers."

"The problem is that it is the ratio of two numbers - a "bad" number divided by a "good" number. Now for aircraft the "good" number is wing area - and the more of that the better - but for cars its the cross sectional area - and there is no particular reason why having more of that is better. Last time drag coefficient was used as a marketing tool it spawned a clutch of ugly bulbous cars with artificially boosted (pointless) cross sections which reduced the drag coefficient whilst increasing the actual drag!!!"

Ugly bulbous car, huh?

Hum Does anyone watch NASCAR at all , I dont think you want to tell them the builders and designer freaks that drag coefficient on cars doesn't mean anything !!!!!!

How about Bonnieville , anyone catch my drift yet !!!

Then again why wash and wax your cars !!!!

Well, even I know that waxing your car will reduce surface drag, which is different than form drag. You can only reduce form drag by changing the shape of the vehicle.

Cd Does Matter (As does Cd.A)
As a ground vehicle aerodynamicist with 15 years experience covering rail and automotive aerodynamics I can tell anyone who is interested in a well informed comment that drag does matter (along with the other aero forces and moments). All major automotive manufacturers continue to spend many hundreds of wind-tunnel hours optimising this parameter.

For cars the drag coefficient is the drag force divided by both the dynamic head (0.5*(air density)*(air speed over the vehicle)^2)and projected FRONTAL area. The drag coefficient multiplied by this area, Cd.A (the so-called "drag area") is a critical parameter influencing fuel economy, top speed and acceleration in gear. What Cd provides is a measure of the efficiency (drag related) of the shape.

The overall drag for cars is dominated by pressure drag (form drag) which arises from variations in the pressure distribution over the vehicles external surfaces (some drag also results from air taken into the car for cooling). Skin friction drag is very small for cars (but very significant for aircraft and trains). So polishing your car will not reduce drag measureably.

Given that at cruising speeds a car will be burning most of its fuel to overcome aerodynamic drag, only a fool would ignore this parameter in its design. Cd remains a convenient and meaningful measure of this force. Of course, one should always compare vehicles in terms of their Cd.A value also, to account for differences in their size (height and width).

Are the aerodynamicists at DaimlerChrysler laughing or cringing?

How does the Reynolds number or a fish compare with that of a car?

"Cd Does Matter (As does Cd.A)"

yep that's right, but the shape of the box fish and especially the sharp edges along the front and top side are the trick...not the overall shape! Take a look @ some ohter pages pics with the fish and aerodinamical studies..... :it was tested thoroughly, i can tell!

;-)


Drag Coefficient and Reynolds Number
It may not be the most stylish concept car, but beauty is subjective. Objectively, the DC aerodynamicists must feel pretty good about a 0.19 Cd (most cars have Cd's in the range 0.28 to 0.32 , some are better and some worse, and remember that you always need to look at Cd.A to!). The only low-drag concepts I have come across that scored a lower Cd were the Ford Probe IV(c.1983) and GM Aero 2002 with Cd's of 0.15 (A=1.9m^2) and 0.14 (A=1.68m^2) respectively.(1) The DC concept does look a more viable package than either of these.

On the Reynolds number question (Re, the ratio of inertial to viscous (i.e. frictional) forces), that depends how quickly a fish swims and how big it is, compared to a car.

Re(L)=(U*L*rho)/mu, where U=fluid velocity; L is a characteristic length; rho is fluid density and mu is the molecular viscosity. Anyone who is interested can work out Re for a fish!

It's interesting to note that a body will have the same Re in both air and water, provided it travels at approximatley 14 times the speed in air than it did in water. This increase in velocity will then balance out the higher density and viscosity of water compared to air.

Cars have Re values into the low millions, showing that inertial (i.e. pressure drag) forces dominate over the frictional (i.e. skin friction drag). Of course the specific value depends on their size, speed and the ambient temperature/pressure (note: Re values are formed with different characteristic lengths. These include height, Re(H); length, Re(L) and the square root of frontal area, Re(sqrt(A)), depending on what is appropriate for a given analysis)

REFS.
(1) Hucho, W-H(ed) Aeroynamics of Road Vehicles. p57.

Boxfish Cd
Of course the Cd is a function of both the overall shape and the shape of critical local regions (i.e. front and side sharp edges). For instance, the size and shape of the vehicle's wake will have a large impact on the drag.

They should have chosen a puffer rather than a boxfish...one giant airbag!

Thanks for all the responses, but the initial argument was that the Cd can be increased (made to look better) by increasing the Cd.A. IOW, one can get a better looking drag coefficient when there is more cross section to streamline, so the drag coefficient, by itself, can be misleading. From what I read above, that may be true, but looking at the very tiny DCX, I'm not sure it applies in this case.

More on Cd and Cd.A

1. Shorter bodies (bluff bodies) are harder to "streamline" and thus can tend to have poorer Cd's (They are prone to front end flow separations. If you get separated flow it's difficult to get the flow reattached before you run out of body. If there is no "boat tailing" at the rear the base drag from the wake will tend to be large).

2. With the longer bodies (i.e. more cross sectional area), you do get into diminishing returns as the total surface area increases and skin friction drag starts to dominate over pressure (form) drag. However, if we had two vehicles, with the same projected frontal area (A), one being short and bluff, the other long and streamlined the latter would have both a lower Cd and a lower drag force.

3. The inexperienced and unwary can certainly misinterpret what the drag coefficient (Cd) is telling them. It is a guide to the aerodynamic efficiency of the shape, not what level of retarding (drag) force will be experienced. If one wants to get a relative comparison, between vehicles, of the level of retarding force, or model vehicle performance, Cd.A is the measure to use.

4. Nevertheless, the drag coefficient (Cd) is a good indicator of the relative aerodynamic efficiency of different shaped vehicles.

5. Finally, Cd is an excellent measure then you are trying to develop a particular vehicle and want to know whether you are making it better (lower Cd) or worse (higher Cd).

(Hopefully) Final Cd Comment
As Fagan suggests, one could, of course, reduce Cd by increasing A. This would have to be done without reducing the aerodynamic (drag) efficiency of the shape (As this would put up Cd and defeat the object of this suggested ruse). However, this would be a pointless exercise, since performance is controlled by Cd.A (and anyone who knows how to multiply can check this parameter for themselves)

This line of argument does not diminish the utility of Cd in the hands of the competent. If you think that someone is trying to use this deception, look at the Cd.A.

Check this out:
http://www.deutsches-museum.de/ausstell/meister/tropf.htm

"Bionics" is the same thing that Rocky Mountain Institute and the Biomimicry Guild have been studying for years, but they call it "Biomimicry." www.biomimicry.net They're supposed to launch a biomimicry database sometime this summer. RMI has also been preaching the lightweighting gospel for years, and it's interesting that this boxfish-inspired design led the DaimlerChrysler engineers to a lightweight, reinforced design.

I'm curious what this concept car weighs. Lightweight construction is mentioned in the DC press release at http://wwwsg.daimlerchrysler.com/SD7DEV/GMS/TEMPLATES/GMS_PRESS_KIT/0,2970,0-1-68938-1-1-text-0-68935,00.html?, but no curb weight is stated. From the 103-kW power plant and 8.2-s 0-100 km time, I gather it is probably not ultralight. If it were, it would probably be significantly more efficient yet. See http://www.rmi.org/images/other/Trans/T04-01_HypercarH2AutoTrans.pdf and www.oilendgame.com for examples, and www.fiberforge.com for a process that could produce ultralight carbon vehicles, meeting all requirements (including cost and safety) at midvolume.

I tried winkling the weight of the car out of DCX through official channels, but to no avail. The most they will say is that the enginers did apply the SKO method to parts of the bodyshell work, but they wouldn’t even say which parts.

However, Frank Giovinazzi of Car Buyer’s Notebook was at the Washington event, and reports that the vehicle weighs 1,100 kilograms, or about half the weight of a comparable minivan or crossover vehicle.

1,100 kgs is heavy by todays standards of efficient cars.I run a modern 4 seat car that weighs 720 kgs and is built of steel!

I happened to be at the new aquarium in Hull (UK) last week and co-incidentally was closely observing a Boxfish, although I failed to note its identity at the time. My initial reaction to seeing the above feature was: "Of all the fish in the world, why on earth did they choose the least streamlined?"!

The Boxfish in the aquarium was dawdling along with no perceptible tail movement, but very fast flapping of its dorsal and pectoral fins. My supposition was that this was obviously not an animal for whom speed was a priority, and that other evolutionary concerns must have guided its development.

As an engineer I appreciate the limitations of making comparisons exclusively on coefficients, but can also see that the study of this fish's structure might give useful engineering ideas. However, regardless of the obvious aerodynamic cleaning of the vehicle, the overall shape seems far from ideal, and the added styling ridges can only be detrimental (unless cleverly positioned to provide vortices to the rear, thereby assisting flow attachment).

My conclusion is therefore that, although the designer may not have meant to produce a misleading drag coefficient, the undesirably boxy shape would certainly give a disproportionately large area to divide the drag force by.

I really don't mind if it is not the prettiest design, what everyone should be looking at is the mileage. What is the matter with people. The auto manufactorers need to get fuel efficient cars on the road now. At 70 MPG everyone should be driving one.

Awesome! When can I get one!? I have a Toyota Prius but expected more from the milage. I get 35 mpg on a regular basis. I agree with zane: we really need to be most concerned with the milage. How about those "hybrids" that do not get better milage!?!?!?! What are people thinking?!?!?!? Doesn't everyone want to stop supporting the middle east by not buying their oil and how about saving the environment by not using fossil fuels???? for the first time this kind of progress would impact the richest 1% of the population so we haven't been able to break through for years. Same with alternative energy sources! What happened to the auto commercials that used to list the milage in the advertisement?

They said the Beetle was to ugly to sell. Well it was the most successful automobiles ever made. The Boxfish is even cuter and I would buy one as soon as they were produced, even if only for the economy! Unlike Hydrogen Fuel cells, you can buy Diesel anywhere and the diesel has been around for a long tine!. I believe that if Mercedes took a poll of those that would actually buy this car, they would start making them NOW!! They can put me on the waiting list.

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