Electro-Mechanical Valving

[the3car]

Team,

As a student of classical IC engine theory, the CAM has always been of interest to me. Has there been any threads considering the use of Electro-Mechanical Valving?

The last I knew, there were a few R&D efforts underway in this area. If you can get by the amount of energy it takes to "push" the valve, can you effectively "rewrite" your intake and exhaust events? Since modern cam design has been limited by force exerted on the lobe, due to physical contact rules, is there a place for a valve timing that is not limited by this phyical contact concern?

Would this technically re-write "our" ideal of a CAM profile for max power...etc...?

Thanks

Andrew

 

[willeng]

the3car:

Pneumatic valve actuation without springs, has been in some of the top racing classes throughout the world for many years. Electronic valve management has been & is being touched on at present. The reliability factor of the electronic valve actuating mechanisms is & has been the big question.
Hope this helps

 

[pbloore]

I think Lotus have a system giving total control of the valvetrain if hat's any help to you.

 

[dwedel]

I think this is an interesting question also. Unfortuneately I have not seen a solution put into practice. Lacking EE expertiece, I don't think I could help your discusion any.

I have been thinking about the pnuematic option. In the race cars, do they get rid of springs entirely? Are the engine valves actuated by air or a cam?

The picture in my head, when people talked about springless engine vavles, was a bladder replacing the springs with cams moving the valves.

 

[the3car]

Well, I guess I'm not worried about the electrical side of things. This is how I picture it. There's an electrical actuator atop the head, that can instantly open/close the valve, with tremendous force.

The forcing function, would have to be tailored to allow a "soft" closing, therefore not damaging the valve seat area. But, just after leaving the seat, the valve could be forced open/close in a drastically faster time than the cam lobe could do.

This is why I think it would "rewrite" our knowlege of the intake and exhaust event. Having a larger port area open, for both intake and exhaust, certainly would have profound effects on combustion. Think of the amout of exhaust you could get out? Would this effectively give you a 10-20% better intake charge?

Andrew

 

[aspearin1]

What you're suggesting sounds like an overactive solenoid. From my experience, solenoid valves tend to have shorter lives and are already somewhat prone to failure from wear and tear. I would think that constant shock of ON-OFF-ON would increase this risk and could be the weak link in your engine. I'm not an ME yet, but if I had a piece that I knew was a likely candidate for wear, I'd keep it out of my critical engine operations where a small failure would cause catestrophic failure for the rest of the machine. This is especially true if I were a racecar driver and I was already putting amazing stresses on my vehicle, and prize money is at stake. Correct me if I'm wrong. I'm interested to know if what I've said makes sense from an ME's or EE's point of view.

aspearin1

 

[the3car]

aspearin1,

Thanks for the response. Your right, I have no idea of the wear conditions of this type of solenoid. Not being an EE, I don't know if this type of solenoid is even possible. My guess is that it would have to be electromagnetic in nature...

But theoretically speaking, the solenoid shouldn't have any moving parts, other than the plunger (valve stem). This should mean that it not be prone to mechanical failure, electrical failure I'm not sure about.

My question is really meant for the combustion event. Can changing the valve timing, opening and closing, really produce more power, better fuel comsumption, etc...?

 

[dwedel]

When I have chanced on these discussions, several items come up.

If you could change the valve timing events, you would only help out an engine that has drastic load, no load extremes, such as automotive, transportation, and off-highway aplications. It is only the load and no-load situations which brings about a benifit to variable valve timing. This could be tied some what to engine RPM, but I am not sure.

When air as a power transfer medium is brought up in these enviroments, the follow problems are also mentioned.
1. Low efficiencies compared to mechanical accuation.
2. Means of charging air systems after extended idle periods.
3. Air compression and storage systems large weight.

These problems lead me to believe that you should have the combustion chamber valves directly accuated by an electric solenoid or servo, without the air as a middle man.

There are constant load engines that are exceding 45% thermal efficiancies. It is the variable load problems that are making the IC transportation engine less desireable.

To further comment on this. It seems to me that the Otto cycle with its need to spark ignite, is limited because of the A/F ration that is needed to igninte. Unless fuel is directly injected into the cylinder, and then extra cylinders are not used, you have a minimum fuel usage that is needed to keep the engine running, even if the power is not used. Variable valve timing could help here, so cylinders that are not used, don't compress the air charge.

A diesel is able to ignite very lean mixtures and still run, because of its compression ignition. Most diesels run in a limited RPM range, so the valve timing doesn't seem to be as much of an issue. However, each revolution of the engine requires compression of the air whether it is used or not. However, again, if variable valve timing is used, a cylinder could be disabled and then it would not have a compression stroke.

I'm not sure if this all makes sense, but it is some ideas that I have been thinking about.

 

[EdDanzer]

The Engine & fuel engineering forum has several threads about this subject.

 

[DEngler]

MAN B&W is building a ship engine using computer control and hydraulic pressure for exhaust valve actuation and fuel injection. This allows complete control of valve and injection timing, resulting in pre-programmed optimization scenarios, useful for running for best economy or best emissions also at all engine load levels. The system is apparently robust enough to be approved by the ship engine classification societys. See

http://www.manbw.com

and look for "ME" engines.

 

[O320]

I have seen experimental model engines on the net using solenoids to actuate the valves. I certainly seems to be a possible solution given due development. Sorry but I can't remember the web address.

 

[jmw]

The first part of the equation is to do away with the springs. Desmodromic valve systems have been around for a considerable period as any web search will reveal:

http://speedwaybikes.fortunecity.net/desmo.htm

To do away with the cam is the next objective. In the meanwhile, as DEngler suggests, many large diesels (operating at 1000RPM or less) such as MAN B&W have eliminated many of the mechanical components in the valve train and introduced common rail injection, computer controlled.

Companies such as Wartsila (the largest supplier) have an objective to introduce "parameter based" engine management which is to say that they will use the engine management computer to modify the timing etc in response to changing load, fuel quality, ignition index etc.

JMW

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[j2bprometheus]

Hi-
Lotus (the exotic car company) has an electromagnetic valve actuation system that they claim is "ready for production". I don't know how much power it consumes.

AURA (a company that makes speakers) worked for years on making an electromagnetic valve actuation system. I don't think that their system ever made it to production.

Folks before mentioned the pneumatic systems used on race cars. Hydraulic actuation of valves is also possible


From j2bprometheus@aol.com

 

[Colonel]

I am developing an new IC engine, Being a Two Stroke combustion cycle, the inlet and exhaust valving is set. The fuel can be controled in that it is intended to direct a combustion fuel/air mixture using an electronic valve to time and meter to the combustion chamber. This concept is not entirly new but the concept is a little different. I have been almost 5 years in development and am now close to a working prototype. You have a good concept there so keep at your vision. Use a good solid modeling CAD program say SolidWorks 2004, you will be supprised how much can be realised before drilling a hole etc. Listen to and take all the advise that is positive good luck.
Colonel