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Scientists Claim Major Leap in Engine Design
An anonymous reader writes "Purdue researchers say they have made a major advance in the design of the internal combustion engine, one that could seriously boost fuel efficiency and cut emissions. A key portion involves building intake and exhaust valves that are no longer driven by mechanisms connected to the pistons, a departure from the way car engines have worked since they were commercialized more than a century ago. 'The concept, known as variable valve actuation, would enable significant improvements in conventional gasoline and diesel engines used in cars and trucks and for applications such as generators, he said. The technique also enables the introduction of an advanced method called homogeneous charge compression ignition, or HCCI, which would allow the United States to drastically reduce its dependence on foreign oil and the production of harmful exhaust emissions. The homogeneous charge compression ignition technique would make it possible to improve the efficiency of gasoline engines by 15 percent to 20 percent, making them as efficient as diesel engines while nearly eliminating smog-generating nitrogen oxides, Shaver said.'"
Slashdot had a related story a while back on increases to engine efficiency. Not sure if it's related.
Nothing spectacular about changing the timing on the valves depending on how the engine's being driven:
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http://en.wikipedia.org/wiki/Variable_valve_timin
According to Wikipedia, VVT has existed since the 1960's. The only improvement I can see (and that's from reading between the lines) is that they've developed a means of controlling it more precisely.
Why does this warrant such a sensational article? Racing engines have been actuating valves pneumatically for years and exhaust gas recirculation has been around forever too. Hell, Honda's old CVCC used a similar exhaust technique back in the 70's.
It's not just Purdue working on this, nor is it cutting edge. The idea of variable valve actuation has been around for a while as well as HCCI, which has some problems that are yet to be overcome. One of the notable ones that I recall is simple power. As the Wikipedia article notes, in a gasoline engine, you increase the fule/air charge to increase power. In a diesel engine, you just inject more fuel. In an HCCI engine, it's tough because "many of the viable control strategies for HCCI require thermal preheating of the charge which reduces the density and hence the mass of the air/fuel charge in the combustion chamber, reducing power. These factors makes increasing the power in HCCI inherently challenging."
For more info, the Wikipedia page has some great references:
- Research, publications at Lund University
- Research at Chalmers University of Technology
- Research at Stanford University
- Research, publications at University of Wisconsin, Madison
- Research at University of California, Berkeley
So, it's got a lot of benefits but a few trade offs that need to be addressed first. Honestly, why would Ford/GM buy this out and kill it when they could just develop the technology themselves and integrate it into their vehicles like Hitachi's research? I mean, just because technology changes doesn't mean they should kill it instead of changing with it, right?My work here is dung.
Why keep a cam if you're electronically controlling the valves? Just like ignition systems have gone to fully solid state, with very few cars having distributors any more, why not move to fully digital timing?
The cam/valves are really the last mechanical part of the loop. The fuel/air mixtures are now fully controlled by the ECU, and can change on the fly to adjust for altitude, temperature, manifold pressure (turbo and supercharged systems), and the octane of the fuel. As I mentioned above, the spark systems are now fully controlled by a computer, and advance or retard the cylinder ignition, sometimes in conjunction with the fuel curve, to best burn the fuel/air mixture. Being able to dynamically change the valve timing, opening, closing, overlap, duration opens up even more possibilities for tuning and timing an engine.
In Formula One racing, motors have featured compressed air to open and close the poppet valves. This is related to that development, at least 20 years old. It makes valve timing independent of crankshaft angle, so maximum efficiency can be reached at any or all engine speeds. Parasitic losses are less, and so is weight, the cam, cam drive and other associated rotating parts can be replaced with air or oil operated solenoids.
The other "development" you mention is that adding water to the combustion process allows a higher compression ratio to be used without the risk of preignition or knock. This results in more (and more even) combustion pressure, meaning more torque everywhere from the same amount of gas. This method is very popular among drag racers, and is sometimes used with air/water injection into a turbo- or supercharger's plenum to keep the pressurized air from becoming uselessly hot before compression in the motor.
Rotary valves are a much older development. They have no history of producing more power or reliability (or even efficiency) than traditional valves. Of course, there is no reason they should. Both of the above techniques combined might double the efficiency of the internal combustion engine.
I don't know if you've ever had to compress a valve spring, but they're pretty pissed off devices.
The best thing we could do would be to move to some kind of rotary valve system - any kind, really. Because reciprocating valves have problems. They are what limits RPMs, which is why rotary engines have been known to reach over 10,000 RPM, and why a [very very built] small block tchevy :) with a Coates rotary valve system has reached over 12,000 RPM (can't find cite for that, but their page says "The comparative efficiencies of the spherical rotary valve combustion engine have enabled engine speeds of 14,850 RPMs."
We could make smaller, even more efficient engines by increasing RPM, but we don't do that because it causes valvetrain death. In order to get high RPMs, you need to be able to open and close the valves faster. Cams only open valves; springs shut them. This has two effects; one, there is a hammering process that goes on between the valve and the seat. Two, if the springs are not strong enough, they do not push the valve closed fast enough, and you get a phenomenon called "valve float". Solenoids can provide infinitely variable valve timing and duration, and through a shifting system (where the whole actuation system moves) you can provide variable lift. But as you increase RPMs, you need to increase the spring rate, and therefore you need stronger and stronger solenoids.
A solenoid valvetrain has been used in racing (I forget by who) but no one has managed to make a system suitable for the street yet. That's really too bad, because you could eliminate most of the valvetrain that way. But there are definitely serious implementation issues. Rotary valves are here now. There are competing designs, but none with pictures as pretty.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
This is not news. BMW has been playing with this for years. So has Mercedes -- they call it EVT, for Electronic Valve Train. And next year it will ship in the 2008 C-Class sedan.
FATMOUSE + YOU = FATMOUSE
The trouble with direct valve actuation is making an actuator that's fast enough, powerful enough, small enough, heat-tolerant enough, and reliable enough to do the job. Cheaply. This is not easy. Prototypes have been built, but it's still not something that's easy to do. BMW did quite a bit of work in this direction, but backed off to their "Valvetronic" scheme, which still has a camshaft with other components to give some adjustment potential.
Most of the existing schemes for tweaking valve timing still involve camshafts, but there's an additional mechanical linkage which allows adjustment of phase angle, valve travel, or both. That's an idea which goes back to steam engine design. Most of the gear on the side of a steam locomotive is there to adjust valve timing. Steam engines are controlled by valve duty cycle, not throttling. This was the original pulse-width-modulation system. On steam engines, valve phase can be adjusted far enough to reverse the engine, which is how locomotives back up. Some newer marine diesels have that feature, too. Eliminates the need for a reverse gear.
So this isn't a new idea. It's an old idea that's hard to make work cost-effectively. Somebody may crack this thing; it's a tough mechanical engineering problem, but not an impossible one.
Ah, yes, the mandatory conspiracy theory. Get this, this is just variable valve timing which by now a _lot_ of car manufacturers _already_ use, with various degrees of sophistication. This one may be slightly more efficient, but the important thing is that steps in that exact direction have been made, and there is already a healthy competition in that domain.
If you'll kindly read that Wikipedia page, you'll notice that both Ford and GM, since you name-and-shame them, _already_ offer engines with variable valve timing. GM has worked on theirs since 1975, and built automobiles equipped with, say, their Northstar System since at least the 90's.
So, you know, even as conspiracy theories go, this one... shall we say, fails to be entertaining at least. It is lacking in the suspension-of-disbelief quality. It's akin to asking me to believe that Boeing is trying to kill the jet engine... never mind that they're already using them.
A polar bear is a cartesian bear after a coordinate transform.
Unfortunately, you are wrong. It has everything to do with normal accounting and taxes. The tax code was altered to allow rather hefty deductions for those class of vehicles for a lot of people and professions, so the demand went up considerably, and it killed off the smaller normal family station wagon, which it has replaced.
Well, no actually. A rotary such as the current Mazda 1.3 litre simply spins faster than the equivalent piston engine. The volume passed per unit of time is the relevant comparison, not the static displacement.
Since the RX8 competes with similar HP sports cars by guzzling at SUV rates, it indicates Mazda's best effort so far is still inferior in power conversion of the gasoline. (Though the smoothness is great fun.)
As for turbines, same deal really. The aircraft turbine has yet to match piston engines on efficiency for short flights. You have to run long-haul at cruise altitude before the overall fuel consumption is lower.
The idea of a completely spinning engine is very seductive, but the actual results of forty years of careful research has not delivered a spinning engine that's better than the 'tossing potatos'. This is counter intuitive, and it's entire worth your while to dig into the studies to find out why that is.
You forgot #4: reprocessing had a terrible history at that point. Incidentally, Ford started the policy the year before.
"Reprocessing plants around the world have exhibited poor records of occupational safety, pollution control, waste containment, and security. For example, at the Hanford military plutonium reprocessing plant in Washington State, over a million gallons of high-level liquid waste has escaped from steel-and-concrete tanks into the soil. One gallon of this waste is enough to ruin an entire city's water supply. Hanford workers have also shown a significant increase in the incidence of cancer. In Russia, an explosion involving high-level liquid waste contaminated hundreds of square miles and hospitalized thousands of people. In the UK, a small explosion in 1973 occurred at the Windscale reprocessing plant [now known as Sellafield], and radioactive effluents have been substantial. In the US, large quantities of plutonium are missing and "unaccounted for" -- enough to make several hundred atomic bombs." (http://www.ccnr.org/AECL_plute.html)
The UK has been reprocessing recently at their THORP plant, and it suffered a significant leak in 2005, so it's not just ancient history.
Granted, much of the current concern about reprocessing is about making weapons-grade Plutonium, but the concern is generally that a country like Iran might use U.S. reprocessing to justify their own, but tweak their own plant to create Pu-239.
Ooh, a sarcasm detector. Oh, that's a real useful invention.
Don't be so naive. Both American Car companies AND oil companies have a vested interest in keeping things status quo. They are greedy bastards and want to wrench every penny from you. Don't believe me? Go watch this movie Ah, "Who Killed the Electric Car". A balanced an measured analysis, of course, and not a biased propaganda piece, to judge by the title. (snort)
You want to know the deal with the EV-1? California bureaucrats thought they could wave a magic wand (i.e. use laws) to make technology advance. GM whipped up a quick electric car out of off the shelf parts, but at the same time sued to have the mandatory production rules reversed. The problem with fielding a vehicle like the EV-1 is that GM is then required to support that car for ten years after the date of manufacture. The owner of the vehicle has to pay for it, but GM would be required to maintain a full supply of parts and a staff of mechanics capable of servicing those vehicles. This would not be a trivial expense. The more EV-1's sold, the more expense. The arbitrarily short timetable mandated by the CARB made ramping up such a service system doubly expensive. The temporary rental scheme was something of a short term loophole that put them technically in compliance and bought them enough time to litigate the CARB into submission without incurring a long term maintenance liability. The thorough destruction of said vehicles is to ensure that no one will ever be able to hold them to their mandated parts and service obligation should they ever somehow get their hands on one.
If a job's not worth doing, it's not worth doing right.
As a Canadian, who has driven in extreme weather for 17 years - ANY car, with proper snow tires, is adequate for almost any situtation you will encompass. The only weather it won't help you with is sheet ice, or huge drifts, and there, you're finished in anything short of a lumber skidder or perhaps a tank.
I easily outmaneuver SUVs on "all season especially winter" tires in my little FWD car with maybe 5" of clearance tops. Because I have enough sense to put proper snow tires on in the fall.
4WD does nothing to help you stop, either.
..don't panic