What do you guys think of this engine?

[John Milmont]

DRE | Engine Overview

I think it has too much rotational mass and suffers from an oddly shaped combustion chamber which will lend itself to inefficient fuel burns. They say otherwise, but I have doubts. Furthermore, ported engines have trouble with variable intake and exhaust timing which is done so easily these days on engines with cam shafts. On ported engines, they try to get around this with complicated variable length intake runners to try to tune the engine for a wider power band. But those systems add so much more complexity. I understand this engine uses pistons to force the air into the combustion chamber, but those intake pistons must have some sort of manifold. They also say that the ports for the engine open almost instantly, that usually translates to very loud exhausts like in a wankel engine.

This engine also uses wankel apex, corner and side seals!! :lipsrsealed:

 

[Jac Mac]

I like it, your comment about Mazda apex seal etc are somewhat out of context with regard to the way they are utilized in the doyle application..on the Mazda they are travelling in a non constant surface speed & a greater distance per revolution, in the doyle they are static in the stationary crankshaft & mounted at a radius distance that will never see the surface speed of the outer rotor/piston housing reach those of the mazda application.

Rotational mass... that should be a plus over the piston or wankel rotary concept as the effective mass will stay fairly close to constant, a conventional 4 stroke piston engine has that mass changing and moving back and forth along the crankshaft length all the time, that same movement in the doyle is limited to about a 1/3 rd of that length & reduced considerably by virtue of the design.

My major concern would be cooling & metalurgical component life in that single central combustion area, with only the one ignition source reqd the plug or ignition source is going to be critical.

 

[DaveM]

Isn't this kind of like an air cooled aircraft engine with the pistons/rods reversed?

 

[Al Jones]

Jack is correct in that the seals should have prolonged life as opposed to the Wankel type engine. The problem is that the seals on the combustion/exhaust side are continually exposed to a high temperature environment whereas, in the Wankel, the seals rotate through a cycle of incoming charge, cooling them in that period. If the burned gases can be cooled somewhat by an intercooler device, it would help, problem being that this extra heat would inevitably be routed to the vehicle's cooling system and there is precious little room for this device.
Another problem is carbon build-up. The combustion/exhaust gas enters and exits at slightly cooler temps and stays in the chamber and passages for a longer time, inviting carbon deposits. Adding to the probem is oil injection into the seals and oil spray under the pistons for cooling with no system for recovery (like falling back into an oil pan).
Also, it will be a masterpiece of salesmanship to convince a major manufacturer to invest in this technology, notwithstanding Mazda's foray into different design. There are other designs that offer seemingly improved operation that haven't found favor as well - take the Migrating Chamber Engine - quiet running, [almost] ambient temperature exhaust, low emissions, good low end torque, etc, and what about Ford's extreme mileage two stroke? Plus, don't forget Chryler's attempt at turbine power. Where are these gems?
I have only dabbled in engine design (as probably only Jack knows) so please don't beat me up on these observations, but at this point it looks like time, testing and an incredible salesman will tell the story.

 

[Jac Mac]

Thinking out loud here without reaching any conclusions..it is friday night & I have had a couple of rums...
I wonder when you go to extremely high comp ratio as quoted in this type of engine & achieve fairly efficient lean burn whether the combustion temp really does get to a critical level... baseing this thought on how the exh gas temp drops away very quickly once you go past lean best power in a conventional 4 stroke piston engine...that point just before everything starts to melt & head south..

 

[zollis]

Hi Jac , by now the couple of rums are converted into -- fertilizer - , the sun is shining and spring is in the air . Do you still stand by post # 5 ???



Z.C.

 

[Jac Mac]

Hi Jac , by now the couple of rums are converted into -- fertilizer - , the sun is shining and spring is in the air . Do you still stand by post # 5 ???



Z.C.

Depending on which point in the fermentation process it is at yes beside it but to a slightly lesser degree

I hope you have watched his video/dvd presentation so we are at least on the same wavelength... some facts quoted from his presentation.

1. The motor does not use a throttle blade to control speed etc at this point- this is being done by control of fuel supply..
2. The quoted 95/1 comp ratio is a bit misleading in context of how the engine operates...
3. The combustion process is initiated in the central combustion area, but once underway it is 'shifted] to the piston/cyl[ 2nd row]

Perhaps the best way to describe the combustion cycle in this is to liken it to that of a jet engine, but with pistons doing the 'work' of the sections... the AIR is brought in thru the center crank assy to a piston/cyl in the front row, it is then compressed in that cyl [ this is where the 95/1 comp is effectively computed] which then pushs it into the central combustion/transfer cavity to the second row... at this point fuel is injected & ignited while still contained in that chamber...continued rotation now opens that chamber to a piston/cyl in the second row for what is the power stroke and then on to align that cyl with exhaust port...... So the heat buildup in the enter combustion area might not be as critical as I first suggested...yes with the multiple cyl version as depicted the combustion will be ongoing, but the majority of the heat exposure from each power stroke will be in the individual cyls of the second row, therefore the 'time & area' available for heat dispersal is greater.... I still have some questions about it that I have not worked out the answers to yet myself...one of which was behind my comment last night...with no control over the amount of AIR admitted, how do you accurately control the amount of fuel reqd...yes I know thats the diesel method, but these guys claim to be using pump gas....

Hope I have not confused you further than you might already be...a talent I have that some people have already made me aware of..

 

[zollis]

Jac, all good. Not many people whom have clear analytical thought processing capabilities while/after a " couple " of rums.

As for the engine; I will not risk venture capital into this idea.


Z.C.

 

[Jac Mac]

Jac, all good. Not many people whom have clear analytical thought processing capabilities while/after a " couple " of rums.
It has 'hic' taken decades of pratice to reach this lebal...

As for the engine; I will not risk venture capital into this idea.


Z.C.

Seriously... I see Mr Doyle has an aviation background, given the 150 HP zone this engine is in I wonder if his 'real' target is light aviation... if it can make that 150 Hp @ around or just under 3000 RPM without any vibration problems & get thru 2500 hours TBO it would shake up the aviation scene, but that piece of paper from the FAA to certify it as suitable has become very expensive to attain...

 

[Al Jones]

Jac Mac - I understand what you're saying about the distributed heat under time/volume concerning seal life. My concern would be just what you said about throttling using fuel volume without a corresponding air volume change. For one, the compression ratio in the combustion stage will not be the effective compressed cylinder pressure when transferred to the single combustion chamber; expansion, pressure decrease and a certain amount of charge cooling will take place, reducing effective efficiency. This combined with what appears to be excessive or inadequate fuel charge, depending on low or high rpm, could produce an overly lean condition at one end of the range, especially using gasoline for fuel. Propane would be better but impractical for certain apps. As is, this would be fine for a constant speed engine. I think you're right about this being aimed at the aircraft market, if the rpm range is such. The other problem is emissions, for a mass market. This engine might have high nitrous oxide and CO discharge, given the operating temperatures and compression, and render it unsuitable. This might be better off using higher rpm and a gearbox ( increasing cost). The forced induction,long stroke design of the engine I showed you might be a better match for aircraft use with a fixed pitch prop. These are all just guesses, of course, but it is an interesting design. You could approximate seal life by looking at long term seal life in supercharged Mazda racing Wankels. A.J.

 

[Ian Anderson]

Al

How about ir running a generator which charges batteries and powers the car electrically similar to a Prius but with a constant engine speed

Ian

 

[Jac Mac]

Perhaps its just me, but I have never quite got to grips with the principle of hauling batteries around to fill in the gaps where the fuel engine is not sufficient....

The 'effective stroke' due to the outer mounting points of the 'con rods' of the Doyle engine is huge, but I have not got time to work out what it really is when you factor in rod angle and duration of actual power stroke on a per piston basis, but i think the torque should be quite high..

 

[Jim Cowden]

It is no oil painting to look at.

Al they claim lower Nox due to lower combustion temps.

I would say that they are using some direct injection tech.
Some of these are running 22:1 comp.
They control combustion with 3 injection patterns into the chamber and utalizing the shapes on the top of the piston at specific piston position and conditions.
A lot of this goes on after TDC and as jack stated the piston is running away very quickly by this point, this lowers combustion temps and NOX , but it does increase EX temps.
They are opening the throttle at engine speeds with no change in rpm because they control it via fuel delivery.
I would also bet the injector pressures are very high and they are controling and varying the pattern to suit conditions.

I think you have to get away from the comp ration because it has no fuel in the chamber ,they are just a pump.
I think it has a combo of jet engine combustion chamber and deisel pre combustion chamber to drive the second set of piston.
The high comp is probably required to fill the chamber due to its area and the consumption from the second set of pistons.
The comp will also give a homoginous mix of the fuel,also I
guarantee they do not inject the fuel in one hit.
If you think about it once the fire is going they keep feeding it with air and a bit of fuel.
If the pressure in the cylinder is greater than the combustion chamber maybe the fire never goes out.