Rotary valved engines
Rotary valved engines
Hi all, I am a newb here, but not as a machinist.
I have been researching developing a roatary valved engine lately. I first came up with the idea back in 1993, but found out that the idea was an old one with a new twist. The biggest drawback using a rotary valve is combustion chamber sealing. Coates Engines has produced working cylinder heads with rotary valves even back then and currently are ready to mass produce them even for some north american manufacturers.
The rotary valve requires a "dry seal" in order to operate. Engine oil required for a valve shaped like a rotating cylinder exposed to the combustion chamber needs lubricated and this mean OIL. Well, I knew you needed something like a ceramic and this is exactly what is being done.
My current idea is to modify the Coates design to allow for a mechanical system for adjustable valve timing. I also would like to know if anyone has experience in grinding industrial grade ceramic, especially silicon nitride using diamond wheels, or anything similar.
My hope is to develop a prototype design, then refine and apply it to a one cylinder, four stroke engine.
I have been researching developing a roatary valved engine lately. I first came up with the idea back in 1993, but found out that the idea was an old one with a new twist. The biggest drawback using a rotary valve is combustion chamber sealing. Coates Engines has produced working cylinder heads with rotary valves even back then and currently are ready to mass produce them even for some north american manufacturers.
The rotary valve requires a "dry seal" in order to operate. Engine oil required for a valve shaped like a rotating cylinder exposed to the combustion chamber needs lubricated and this mean OIL. Well, I knew you needed something like a ceramic and this is exactly what is being done.
My current idea is to modify the Coates design to allow for a mechanical system for adjustable valve timing. I also would like to know if anyone has experience in grinding industrial grade ceramic, especially silicon nitride using diamond wheels, or anything similar.
My hope is to develop a prototype design, then refine and apply it to a one cylinder, four stroke engine.
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I diamond grind Ceramic
We do ball valves for extreme locations
Last one has a 1/2" thick ceramic seeve bonded inside a standard 3" ball valve; then 2 ceramic seats were radius ground and lapped to seal; the ball was 316 stainless steel HVOF sprayed with Tungsten Carbide (0.01 coat) this is also ground and lapped; the thick liner was already in place before grinding the ball; so it was also part of the seal off
Grinding ceramic with a diamond cup wheel is not hard; just spray water on it to keep dust and heat down
We do ball valves for extreme locations
Last one has a 1/2" thick ceramic seeve bonded inside a standard 3" ball valve; then 2 ceramic seats were radius ground and lapped to seal; the ball was 316 stainless steel HVOF sprayed with Tungsten Carbide (0.01 coat) this is also ground and lapped; the thick liner was already in place before grinding the ball; so it was also part of the seal off
Grinding ceramic with a diamond cup wheel is not hard; just spray water on it to keep dust and heat down
One the last frontiers of IC engines is to create an efficient valve train. An engine has to produce enough power to run itself, and power left over is net horsepower. The conventional valvetrain uses a lot of energy to run because of the valve design consisting of poppet valves opened by a camshaft and closed by a valve spring. The nature of the valve spring is what makes a conventional valve train inefficient. The valve is under a constant load because of the spring. When the cam opens the valve, it requires more and more pressure as the valve opens to do this. This uses some of the engines power and multiplied by 2 or 4 valves per cyclinder it is easy to see that it wastes a lot of energy.magic9r wrote:Why rotary valved?
The reason to use a rotary valve, mainly is that it uses no spring pressure to hold the combustion chamber seal, but rather a tight fit or seal, much like a piston ring. The valve is a shaft that rotates with a port cut into it. As it opens and closes, it functions in much the same manner as a conventional valve with less power loss.
Because of its design, one could utilize it to produce a super efficient engine or a high powered engine with the same economy as its counterpart regarding displaced volume.
Another aspect is that the rotary valve design can be more easily modified to achieve variable cam timing, which tunes an engines airflow more closely to whatever RPMs the engine is running.
This explains a lot. What I was thinking for a seal would be nothing more than a cylinder shaped seal. One could use a diamond abrasive in a jig grinding machine to do this.Steve Nuttall wrote: Grinding ceramic with a diamond cup wheel is not hard; just spray water on it to keep dust and heat down
Specifically what do you use to lap in the seal?
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With no reciprocating mass, RPM will not be limited by valve float. When RPM gets too high, the valves can't close fast enough.magic9r wrote:Why rotary valved?
On Formula 1 cars, the valves are actively opened and closed pneumatically. That's how they get 18,000 RPM out of them.
Also why my RX7 (an almost 30-year-old design) got 8,000 RPM in the late 70's/early 80's. No valves.
Steve
My question was asked because I can think of no mass production vehicle engine which uses rotary valves so I was wondering why go rotary for a model engine?
The answer citing energy makes absolute sense.
It's also interesting to know that exotic actuation of conventional valves and rotary engines with ports and no valves at all are a solution for high revolutions, although a compressor might scupper any energy saving and the Wankel is really an exotic rotary 2-stroke not needing valves!
Desmo systems with machanical lift & close will also obviate the fixed losses associated with sprung systems but complexity is high!
Regards,
Nick
The answer citing energy makes absolute sense.
It's also interesting to know that exotic actuation of conventional valves and rotary engines with ports and no valves at all are a solution for high revolutions, although a compressor might scupper any energy saving and the Wankel is really an exotic rotary 2-stroke not needing valves!
Desmo systems with machanical lift & close will also obviate the fixed losses associated with sprung systems but complexity is high!
Regards,
Nick
magic9r wrote:My question was asked because I can think of no mass production vehicle engine which uses rotary valves so I was wondering why go rotary for a model engine?
Regards,
Nick
Well, hopefully automakers will have enough sense to incorporate these designs into future engines. Coates engines states on their website they have agreements to mass produce them in the near future, but is shady on the details.
Why do this for a model engine? I guess just for the satisfaction and possibly a test bed for a more enhanced version on a full size engine.
Plus, it would be neat to see running at a model engine show!
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[quote="Ben91069"] Well, hopefully automakers will have enough sense to incorporate these designs into future engines."
Ben, I'm really interested as to how this would make sense for auto manufacturers, aren't non-combustion-engined vehicles the future?
What advantages do you see this delivering for a commercial engine producer over current technology that might warrant the investment in design & production?
Given the development money and class of engineers F1 teams have to play with what valve technology are they using?
I have a sneaky feeling that poppet valves are still with us for a lot of sound engineering & financial reasons & will still be with us while ever we have combustion powered cars.
Regards,
Nick
Ben, I'm really interested as to how this would make sense for auto manufacturers, aren't non-combustion-engined vehicles the future?
What advantages do you see this delivering for a commercial engine producer over current technology that might warrant the investment in design & production?
Given the development money and class of engineers F1 teams have to play with what valve technology are they using?
I have a sneaky feeling that poppet valves are still with us for a lot of sound engineering & financial reasons & will still be with us while ever we have combustion powered cars.
Regards,
Nick
It makes sense in that they are and will be federally mandated to produce ever more efficient engines. The only non-combustion engine I know of is electric. The problem with electric cars is energy storage, which is why they are building hybrids. The rotary valved engine can work with a hybrid to produce even more efficiency.
Ben, I'm really interested as to how this would make sense for auto manufacturers, aren't non-combustion-engined vehicles the future?
It will actually save money in design and production over lets say the newest innovation, variable valve timing, which is even more complex than what we already have. The design takes less effort than a newly designed valvetrain and the production costs are lower because of less components.What advantages do you see this delivering for a commercial engine producer over current technology that might warrant the investment in design & production?
You're probably right. No one ever said that the best ideas usually come to fruitiion, and I am sure there are underlying reasons why it isn't being done, although I believe it can.I have a sneaky feeling that poppet valves are still with us for a lot of sound engineering & financial reasons & will still be with us while ever we have combustion powered cars.
Regards,
Nick[/quote]
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Again, what are actual the advantages for production automobile engines?
You'd have to give real world details of work showing efficiency improvements for full sized engines, the fact that no racing team even considers them proves that the gains are negligible or even that losses may result.
Call me a nasty old sceptic but rumours and suggestions don't convince me, if someone can quote good data I'll buy it, if not then it's spam perpetuated by the enthusiastically uninformed.
I'm not saying it's cobblers, I'm strongly implying it
Anyone know what a fuel cell is?
Regards,
Nick
You'd have to give real world details of work showing efficiency improvements for full sized engines, the fact that no racing team even considers them proves that the gains are negligible or even that losses may result.
Call me a nasty old sceptic but rumours and suggestions don't convince me, if someone can quote good data I'll buy it, if not then it's spam perpetuated by the enthusiastically uninformed.
I'm not saying it's cobblers, I'm strongly implying it
Anyone know what a fuel cell is?
Regards,
Nick