A New Lease On Internal Combustion 431
Somnus suggests we check out the latest issue of MIT's Technology Review, where researchers describe how they can dramatically boost engine output and efficiency by preventing pre-ignition, or "knock." How they do it: "Both turbocharging and direct injection are preexisting technologies, and neither looks particularly impressive... by combining them, and augmenting them with a novel way to use a small amount of ethanol, Cohn and his colleagues have created a design that they believe could triple the power of a test engine."
Rudolph Diesel (Score:5, Insightful)
Not the final solution (Score:4, Insightful)
I suppose my first question is, when the owner inevitably lets the ethanol run out, what happens? Can the engine computer dial down the boost enough to prevent detonation? Or does the engine just have to shut down?
That aside, it's always great to improve internal-combustion efficiency, but the real solutions will have a more dramatic effect than this. My own view is that the solution should be a plug-in series hybrid with about 60 miles of electric-only range and the ability to run maybe 400 more with the engine providing generator power. This would not seriously compromise the essential attributes of modern cars, while *dramatically* (think 80% or more) improving their fuel economy in many real-world usage patterns.
Then we should have nuclear power behind all those 220v outlets... and 90% of cars should be much smaller, with people able to obtain bigger trucks for big jobs on demand from time-share or rental companies... a guy can dream, can't he...
Re:Old (Score:3, Insightful)
Whoever wrote the article doesnt understand why SUVs and trucks have big engines. Its not because they are powerful, its because they need lots of torque. You can pull a trailor up a hill in an S2000 just like you can a road tractor, but the tractor will use much less fuel and less wearing of the engine doing it.B enignes arent going anywhere in SUVs any time soon, despite this seemingly "revolutionary" new technology.
I predict this will end up as a failure just like the last time an engine manufacturer tried this: http://en.wikipedia.org/wiki/Oldsmobile_V8_engine
No matter how novel the technology, when the product's life depends solely on the customer, your product wont usually stay on the shelves for very long.
Re:Old (Score:5, Insightful)
But the story is different because the system will know what to do when it runs out of ethanol, which is to say retard timing and reduce mileage and power output until you add more ethanol. Water injection is aftermarket and usually not compensated for automatically.
The mileage improvement is pretty compelling and I think we'll see it implemented if fuel prices rise much more.
Re:Since when is this news (Score:3, Insightful)
Getting a lot of power from a small engine isn't very difficult, the Brabus tuned version of my Smart Roadster (review here [carpages.co.uk]) gets over 100bhp from a sub 0.7 l engine, and my less tuned 80bhp version give me about 60 mpg (and thats using our smaller british gallons!). The downside is you don't get lots of torque, which is why you'll only find this engine in a light sporty car, not an SUV.
Re:Check out the 07 MINI - it has this stuff alrea (Score:5, Insightful)
Next time, please try reading the article instead of seeing "ethanol" and "turbocharger" in the summary and shooting your mouth off.
-GameMaster
Buy a direct injection turbo charged car today! (Score:4, Insightful)
People have also long known that turbo charging an engine is a great way to extract more power out of a small engine.
People have also known that direct injection allows you to reduce the tendency to knock since it lets you inject fuel into the hot engine at the very last second - reducing the amount of time the air/fuel mixture has to heat up.
And guess what? Mazda produces cars today that has both direct injection and is turbo charged. For example, the MazdaSpeed 3 [mazdausa.com].
It's 2.3 liter engine produces 263hp and 280lb/ft of torque and has an EPA fuel economy rating of 20/28mpg. So yes, while it does provide good power and decent gas mileage, it's nothing earth shattering compared to turbocharged cars without direct injection.
The engine has a very high compression ratio for a turbo charged gasoline engine (9.5:1), especially one that pushes over 15psi of boost into the cylinders. That is direct injection working for you.
For example, the slightly bigger turbo charged 2.5 liter Subaru WRX engine has a compression ratio of 8.4:1 and maximum boost of 11.6psi is rated at 230hp/235lb/ft of torque (though it is admittedly underrated) with similar fuel economy as the Mazdaspeed 3 considering that it is all-wheel-drive (20/26mpg EPA). The more powerful WRX STi has the same 2.5l displacement, 8.2:1 compression ratio and a bigger turbo pushing 14.5 psi is rated at 293hp/290lb/ft of torque but less fuel economy, 18/24mpg.
Unless there is a lot of potential still to be found by combining these 2 technologies, I see it as more of an evolution rather than a revolution. Perhaps a 1.0 liter engine would be able to muster 120+ hp/torque but I find it hard to believe that it could achieve mileage ratings significantly higher than a hybrid. And you still can't turn the engine off when idling or coasting down hill.
So how about a direct-injection, turbo-charged, atkinson cycle hybrid and combine the best of all technologies?
This is not news, or a discovery. (Score:3, Insightful)
That aside, the problem with this is that a turbocharged engine at full output is very inefficient. A larger naturally aspirated engine will always be more efficient than the small turbocharged engine of the same maximum output. That's because a lot of energy is wasted compressing the intake charge, more than can be made up for with the displacement decrease, even with the newest fanciest garrett turbos. The only merit efficiency-wise of turbo engines is engine efficiency at low loads (when the engine is not under boost) relative to the maximum output. There is obviously a balance to be struck here, and that's why 18 wheelers have big v8's with turbo chargers, rather than even bigger engines or smaller engines running under high pressure. Designing a motor vehicle is always a balancing act, and in most cases a turbo is not helpful because of the cost, reliability and other shortcomings versus the benefits.
Recently, car makers have started using direct injection to combat preignition that can damage an engine. It allows them to run leaner fuel mixtures, higher compression and more aggressive spark timing, improving the power/efficiency of engines. Direct injection has the exact same benefit with turbocharging. There are no compounded benefits from mixing the two technologies.
Re:Rudolph Diesel (Score:3, Insightful)
Equivalent (but inferior) to WATER injection. (Score:3, Insightful)
(My commuting vehicle is a 4-cylinder turbo - and 15 years old. It has 100k miles on it and I'm rebuilding the vehicle around it at a cost of about 8 grand - suspension, tranny, major engine service - because I can't get an equivalently performing vehicle on the current new market at any reasonable price. That's apparently because adding a turbo to a small passenger car has enough downsides that the public isn't interested. (Or perhaps because the auto companies' marketing departments are totally clueless.))
Direct WATER injection of a high-compression ALSO gets this 3-to-1 or better boost. It has the same advantages as the alcohol injection at less cost: Higher power, reduced preignition, etc. But you can go even farther, since water won't, itself, combust.
You also get more efficient transfer of heat to mechanical advantage by using the vaporization of the water powered by the heat of the regular fuel.
And water is easier to find and cheaper than ethanol when it comes time to refil the second tank.
This has been well known for a long time.
The reason it hasn't been built into production engines so far: It requires two tanks of consumables. Run out of one and the engine has to stop, or run in a degraded mode. Auto makers haven't wanted to add that sort of operational complexity due to liability and consumer satisfaction issues.
This "new" idea has the same drawback, only moreso, since the second consumable liquid is less generally available and already highly regulated.
= = = =
On the other hand, we've now got much more flexible computerized control of the engine. With the compression boost provided by a turbo (which can be disabled by software control if the alcohol or water runs out), a car with an empty second-fuel tank can still run while meeting emission requirements and without self-damage. You'd lose 2/3 of your peak power and your MPG would drop. But the car would remain legal, street-legal, and unharmed.
So perhaps it's time to revisit direct cooling-fluid injection, dual-consumable, internal combustion engines.
But if so, unless research shows that ethanol has some BIG advantage over water, using water would have the advantage that you don't need to modify the support infrastructure.
Re:Old (Score:3, Insightful)
Re:I don't get it (Score:1, Insightful)
It's called Brake-Specific-Fuel-Consumption (BSFC) http://en.wikipedia.org/wiki/Brake_specific_fuel_
Which is the power output of an engine divided by it's fuel consumption rate.
It's a good measurement when you're talking strictly engine efficiency, rather than trying to picture it as MPG (which depends just as much on the vehicle's weight, aerodynamic drag, and rolling friction as it does on engine efficiency)
Re:brief review of article (Score:3, Insightful)
If you had bothered to read the article you would have come across this paragraph.
The researchers devised a system in which gasoline would be injected into the combustion chamber by conventional means. Ethanol would be stored in its own tank or compartment and would be introduced by a separate direct-injection system. The ethanol would have to be replenished only once every few months, roughly as often as the oil is changed. A vehicle that used this approach would operate around 25 percent more efficiently than a vehicle with a conventional engine.
So this could be something that is refilled when getting routine maintainence instead of a weekly fillup.
Re:Since when is this news (Score:3, Insightful)
Re:New Technology (Score:3, Insightful)
Within the right rpm range, they are perfectly suitable for many installations.
OHC engines are nice for high rpm use, and a dandy martketing feature, but pushrod engines can do the job from industrial equipment to Top Fuel drag racing.
Re:Rudolph Diesel (Score:2, Insightful)
Re:brief review of article (Score:5, Insightful)
Once again, this just shows that what Americans don't know about car technology could just about be crammed into the Grand Canyon.
Volkswagen already have quite a few turbocharged FSI petrol and Diesel engines - take a look at how efficient they are before swallowing this MIT bullshit.
Re:brief review of article (Score:3, Insightful)
In addtion, you could concievably blend 87 octane and Ethanol on-site to provide E85 to existing flex-fuel vehicles that can use it today. There's no installed base of hydrogen vehicles like that to transition on.
Re:Rudolph Diesel (Score:3, Insightful)
The thing gets about 68mpg normally and according to the official stats could get 75mpg if I drove a bit better.
So although diesel costs more per gallon (due to the huge tax difference in this country - it's taxed more.. used to be taxed less then everyone bought one so the gov. upped the tax to rake in some more cash) you still get a much lower cost per mile running cost.
Re:Old (Score:5, Insightful)
Harsh. Apparently someone hasn't been keeping up on Diesel Technology lately. You know it was an Audi Diesel that one the last LeMans right?
I dirve a little VW Golf TDI. 115hp is nothing special, but 175 lbs/ft of torque is enough to get the car moving in a hurry. The car is almost as quick stock as my '88 Fiero with a 3.4l V6 (about 180 hp and 175lbs/ft).
When you have an engine that can (lightly/medium modded) put out 250 lbs/ft or torque from 1800rpm to 3500rpm, the concern is less about RPM and more about Gearing and shifting. Have you seen the new VW/Audi dual clutch manual automatic trannys? Their 6 speed DSG auto transmissions can upshift in 8ms. With that wide of gear range, and that fast of shifting, having a somewhat* limited rpm band is not an issue.
*I say somewhat because the vast, vast majority of drivers will never spin their engine over 3500 rpm. Hondas, Subarus, what have you, they are all designed (stock) as commuter vehicles. And if you have to turn 7k rpms to get your car off the line, it's not going to hold up to daily driving.
-Rick
Power vs Efficiency (Score:3, Insightful)
Triple the power doesn't mean triple the efficiency, if "antiknock" means more fuel is burned. 25% more efficient is more like it. Fuelcells are typically 50% fuel efficient, compared with 40% maximum (to date) internal combustion. That's about a 25% efficiency increase, it's already here, and it's just getting started. Plus the drastically reduced pollution (especially Greenhouse pollution) means huge energy efficiency at the end of the cycle, when climate disasters are avoided. Meanwhile fuelcell efficiency is just getting started, racing towards 80% (over triple typical internal combustion efficiency) and beyond.
So while this advance might be good for the market that's not ready for fuelcells, the fuelcells still look better. But at least we've got scientists and engineers working on fuel efficiency, and not just ways to squander the remaining fuel for combustion engines. That's a big change in efficiency in itself.
Re:Old (Score:1, Insightful)
Re:brief review of article (Score:2, Insightful)
Not changing your oil at the manufacturers recommended interval is foolish and stupid, and imho you deserve engine trouble if you dont! An ethanol topup is the least of your worries if you don't follow the cars basic maintenance requirements.
Re:What About Failures? (Score:2, Insightful)
Re:Not the final solution (Score:3, Insightful)
Do most Americans want to own their house or rent?
Do most Americans want to own their furniture or rent?
Do most Americans want to own their TV or rent?
Do most Americans want to own their computer or rent?
On and on. People want to own "their stuff". Whether you consider it image or not, it's a basic fact. Ownership makes people feel comfortable. It's also convenient, and America is nothing if not a convenience society.
"What, walk a block to where the neighborhood cars are parked, just to drive to a store that's five minutes away?"
"What, have to put all of my baby's stuff in the car after hauling it there, then take out out and haul it back, every trip?"
"What, have to replace this mirror that I knocked off when I could superglue it back on just fine, because the guy over on 2110 East Maple will throw a fit if I don't?"
"What, I have to reprogram the radio every time I drive?"
(and on, and on, and on)
This is a culture for which driving to pick up pizza is too much work, a culture of TV dinners, a culture in which food companies have started to make peanut butter and jelly in the same jar so that you don't have to open up two jars. And you expect people to put up with *that*? Heh, Good Luck.
Re:Not the final solution (Score:3, Insightful)
Americans would and eventually will accept smaller cars, at least as soon as gas prices rise high enough. This could happen through any number of methods, including declining oil production, wars in oil states, or Pigouvian taxes [blogspot.com]. The latter makes a lot of sense because it would help prevent the first two in a feasible time horizon and with few negative externalities save creating a tax that would probably never die (hence bloating government) and potentially increasing the mass difference between very large and very small cars, leading to additional fatalities when they collide.
Still, the benefits for both geopolitics and the environment would be enormous. It would also be much simpler to implement than the grandiose and probably error-prone systems like the one you propose.
We saw a natural example of what happens to auto sales when prices increase two summers ago: SUV sales dropped precipitously and Honda sold even more Civics than it usually does. Prices have a way of making the unthinkable reality, whether Americans will "accept" them or not.
Cobasys passed up lots of sales (Score:3, Insightful)
Not that I'd expect you to admit this, because you're a troll.
Re:brief review of article (Score:2, Insightful)
As an honest-to-goodness engineer with several semesters of propulsion classes, it never ceases to amaze me
that the group of internet fora readers has a massive intersection with diesel fanbois who just can't seem to
get it through their thick-as-a-diesel-engine-block skulls that engineering is about compromise and there
is no such thing as the one best way.
Re:Equivalent (but inferior) to WATER injection. (Score:3, Insightful)
The vaporization increases the volume of gas enormously - in an enclosed space. That increases the pressure drastically. So the heat of vaporization did a bunch of work without necessarily changing the temperature of the water. Meanwhile, lowering the combustion front propagation rate lets the combustion run at a higher temperature - adding more of the heat at high temperature and improving the carnot cycle efficiency. (The water is under considerable pressure and the drops are microscopic. So they get very hot BEFORE they boil. Further, things are happening so fast they can superheat far above even the raised boiling point from the local pressure.)
Think of the liquid water as working fluid you didn't have to compress before ignition.
I haven't done any thermogoshdarnic calculations to check this. Perhaps somebody with more knowledge can fill us all in.
Meanwhile, steam engines that end up with the steam superheated are noted for efficiency, despite having the same heat-of-vaporization issues - even those that don't get to scavenge low-temperature heat for the vaporization step. Unlike ordinary steam engines, internal-combustion droplet-flash-boiling can add most of the heat of vaporization at a temperature far above the softening point of the metals containing the process.