Slashdot Mirror
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.'"
All the benefits will be squandered on making bigger, heavier vehicles. At least, that's what's been happening with improvements in efficiency since the 80s. Sigh...
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.
The also haven't built anything - just modeled it on a computer.
They may not have solved any of the actual implementation issues, nothing in the article said they had.
I don't wish to belittle their design ideas - but it is usually very difficult to go from a revolutionary engine design to an operational engine. A good example is the Stirling Engine, great design - difficult to realize.
I wish them luck - but not going to hold my breath for this one.
None. Why would GM or Ford kill anything that would give them an advantage over Honda or Toyota?
Your Tinfoil hat is on too tight again.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
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.'"
You selected the wrong entry from the Standard List of Villains. The correct comment would have been:
"What's the chance the EVIL OIL COMPANIES will buy this out and kill it?"
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
Yeah, mechanical valve actuation has its problems. It makes for either non-optimal valve placement (standard wedge heads) or overly complicated mechanical actuation trains (see Chrysler original Hemi engine design). So a better method to actuate valves than driving it from a fixed, or fixed-variable, design could make for better engine performance overall. That's hardly new. As best I've seen, this has been merely an engineering problem to determine a better way to actuate valves that meets the requirements of cost, durability, cost, performance, and cost -- when it comes to consumer engines. While such an actuator method is certainly significant news in and of itself, it's not like someone has redone the whole engine.
"It's the height of ridiculousness to say for those 9 lines you get hundreds of millions."
Socialism: a lie told by totalitarians and believed by fools.
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.