125 replies to this topic

[chaos_theory]

Originally posted by Greg Locock
what barks, eats fish, and can sometimes be seen balancing a ball on its nose, eh?

I'm not quite sure what your point is?

[malbear]

chaos_theory.,
How on earth do you seal such a complex internal mechanism?
cheers Malbeare

[McGuire]

Originally posted by PJGD
On to HCCI: this is much more than just controlling residuals (which you need to be able to do on a cycle-by-cycle basis). Having a long dwell at TDC is, I think the last thing that you want. Controlled Auto-Ignition is essentially a detonation event that may only last 10 crank degrees. Burning all of the fuel in that short time results in very high cylinder pressures, so if you want to stay within reasonable limits (say 220 bar), you had better arrange for your piston to be moving away very soon after TDC. Once you have found a way to controllably make HCCI work with commercially acceptable NVH, the engine speed ceiling moves well out of the way; Lund University for instance report running HCCI combustion up to 21,000 rev/min.

If/when it is made to work, I believe HCCI could be the future.

[GSX-R]

Originally posted by PJGD
Lund University for instance report running HCCI combustion up to 21,000 rev/min.
PJGD

Any link about that ?

From another 2005 thread :

Originally posted by J. Edlund
when the fuel is injected, droplets form, fuel vaporises and then after a short delay the vaporised fuel start to burn as it comes into contact with the oxygen.

It would be interesting to know more about this "short delay" and vaporization time in absolute and in comparison to the total burning time. And also marginally to know how long the burning time can usually continue after the cut-off.

Regarding the knock sound of the diesel engine, we can consider the total ignition time of all the present fuel in the chamber quite short and thus not a limiting factor for revving.

[chaos_theory]

Originally posted by malbear
chaos_theory.,
How on earth do you seal such a complex internal mechanism?
cheers Malbeare

To be honest I don't know how they seal it, that's why I posted the link. As I've already said my knowledge of engines is very limited and I was hoping somebody on this forum would be able to provide some insight into the capabilities of the quasiturbine. As far as I know they have already built the quasiturbine and they have a film of it being used on some sort of go-kart.

[chaos_theory]

Also malbear here is another link to a page for all sorts of videos and reports on the quasiturbine that you might find interesting. The page is written in french but the links are easy to navigate, they show the quasiturbine in action.
http://www.promci.qc...invention/apuq/

[Greg Locock]

Well, the reason we raise the question of seals/lubrication is that any kid with a solid modelling program can create a cool looking mechanism, but any old cynic can look at a collection of hinged bars running around at very high speed on friction plates and wonder exactly how they have solved the seal problem.

The way that standard engineering solves the problem of friction is to make sure that the bearings operate at very small velocities compared with the rest of the process (eg wheel bearings, mains), and lubrication by making sure that the minimum amount of oil comes into contact with the combustion process. the quasiturbine fails dismally on both those fronts. The high load bearings run at full velocity, and the oil/seal has to pass right through the combustion chamber.

So far as lubrication goes, they have no solution. you tear the engine down after a few hours and replace many parts.

If they actually produce efficiency graphs for a running engine, or even power curves, and can pass a full power test for 100 hours then they may have a non-niche product. Until then all the animated pictures in the world won't convince me that they have solved the hard bits.

[blkirk]

Also, as best as I could tell, all of those working demos were done with compressed air. Let's see it actually run on a combusting hydrocarbon.

[Kevin Johnson]

"Can a Diesel rev efficiently at 6000 rpm?"

Didn't have time to read everything but didn't see a direct response to this.

The dead-stock turbo diesel in my MB 300 SDL has a redline of 5150 +/- 150 -- I typically cruise at ~3100 or 85-90 mph that is not so far off of a conventional motor. It shifts at 4100. And that motor was most assuredly tuned to be lazy and last long. A bit of tuning should easily get it to 6000 rpm. Efficiently? Not sure what that means.

[Greg Locock]

The problem is that the flame speed in a weak mixture is slower than in a rich mixture. So the flame runs out of time to get through all the mixture in a diesel at high speed. Whether that is the major limitation, I don't know.

[J. Edlund]

Originally posted by Greg Locock
The problem is that the flame speed in a weak mixture is slower than in a rich mixture. So the flame runs out of time to get through all the mixture in a diesel at high speed. Whether that is the major limitation, I don't know.

A diesel burn with a diffusion flame, so there isn't any flame front as in a SI engine. A problem with this combustion method is that the increased turbulence at higher engine speeds does not decrease burn time as with SI engines. With SI engines burn time decrease at increased speed, so burn duration remains similar even at high speeds.

Originally posted by GSX-R
It would be interesting to know more about this "short delay" and vaporization time in absolute and in comparison to the total burning time. And also marginally to know how long the burning time can usually continue after the cut-off.

Regarding the knock sound of the diesel engine, we can consider the total ignition time of all the present fuel in the chamber quite short and thus not a limiting factor for revving.

For example "Design and simulation of four-stroke engines" contains several graphs over the heat release of CI engines. On those graphs one can se that the heat release begins at about 5-10 crankshaft degrees after fuel injection. After this delay there is a rapid heat release, one occuring much faster than in a SI engine. There are however no graphs over the heat release in CI engines at high speed.

[Kevin Johnson]

Originally posted by J. Edlund


A diesel burn with a diffusion flame, so there isn't any flame front as in a SI engine. A problem with this combustion method is that the increased turbulence at higher engine speeds does not decrease burn time as with SI engines. With SI engines burn time decrease at increased speed, so burn duration remains similar even at high speeds.

I would think that HCCI concepts like controlling fuel (charge) temp have been tried to increase the flame speed, i.e. to allow the delivered fuel temp to vary with rpm in a direct injection diesel?

Using hydrogen is cheating?

Originally posted by J. Edlund


For example "Design and simulation of four-stroke engines" contains several graphs over the heat release of CI engines. On those graphs one can se that the heat release begins at about 5-10 crankshaft degrees after fuel injection. After this delay there is a rapid heat release, one occuring much faster than in a SI engine. There are however no graphs over the heat release in CI engines at high speed.

After reading some more articles, I am guessing that the tech is possible to allow efficient running at 6000 rpm but that the engine structure would have to be many times stronger to survive any reasonable length of time. Probably a dollars and cents decision -- why spend the extra money when 4000 rpms will serve well. Or 3000 to 5000 (5500) in the case of the Audi R10 V12.

[GSX-R]

Originally posted by Kevin Johnson


After reading some more articles, I am guessing that the tech is possible to allow efficient running at 6000 rpm but that the engine structure would have to be many times stronger to survive any reasonable length of time.

The limiting factor seems much more to be the pre-iniating delay that combustion time or mechanical resistance. Contrary to a S.I, you cannot effectively advance too much the injection time or increase the swirl.

To get mores revs, you would have to increase the cetane number or/and to increase initial temp at TDC (so by increasing the compression ratio or even the supercharging). In the last case, some engines parts like the turbine could suffer.

Increasing the revving is, of course, intersting to investigate downsizing.

[Kevin Johnson]

Originally posted by GSX-R


The limiting factor seems much more to be the pre-iniating delay that combustion time or mechanical resistance. Contrary to a S.I, you cannot effectively advance too much the injection time or increase the swirl.

To get mores revs, you would have to increase the cetane number or/and to increase initial temp at TDC (so by increasing the compression ratio or even the supercharging). In the last case, some engines parts like the turbine could suffer.

Increasing the revving is, of course, intersting to investigate downsizing.

http://en.wikipedia....i/Cetane_number

Measuring Cetane Number
To measure cetane number properly is rather difficult, as it requires burning the fuel in a special, hard-to-find, diesel engine called a Cooperative Fuel Research (CFR) engine, under standard test conditions. The operator of the CFR engine uses a hand-wheel to increase the pressure within the cylinder of the engine until the time between fuel injection and ignition is 2.407ms. The resulting cetane number is then calculated by determining which mixture of cetane (hexadecane) and isocetane (2,2,4,4,6,8,8-heptamethylnonane) will result in the same ignition delay.

Varying the injection temperature of the fuel will deviate from the standard test conditions, presumably yielding a variable Cetane rating after correction, hopefully with a positive relationship to injection temperature.


http://www.memagazin.../otto/otto.html

Together with ignition timing concerns, Aceves worries that the power output from an HCCI engine would be lower than an equal size diesel, "because the peak pressure limits how much power you can get from a given engine carcass." Because of the high peak pressure, an HCCI engine would need to reduce its output below a diesel of the same displacement. That would be a bigger consideration for mobile applications than it would for stationary ones, he added.

As manipulation of more variables brings the diesel engine into closer correlation with HCCI concepts the "carcass" will need to be stronger.

[Kevin Johnson]

Ha! I knew I would eventually find it.

The Finns have pushed the OM603 to well over 400hp with best power in the 5500 to 6000 range.

http://mersuforum.ne...6f185b6e7d0abc9

Originally posted by Kevin Johnson
"Can a Diesel rev efficiently at 6000 rpm?"

Didn't have time to read everything but didn't see a direct response to this.

The dead-stock turbo diesel in my MB 300 SDL has a redline of 5150 +/- 150 -- I typically cruise at ~3100 or 85-90 mph that is not so far off of a conventional motor. It shifts at 4100. And that motor was most assuredly tuned to be lazy and last long. A bit of tuning should easily get it to 6000 rpm. Efficiently? Not sure what that means.

[Stian1979]

I used to think that a diesel can't rev high and be efficiant.

You simply don't have as good timing control as with a spark plug.

I just read something about MTU now running 3 injection per combustion. They have one injection to start the combustion. one main injection and one afterburner injection. MTU is high reving engines so maybe they found a way to increase efficensy at high rpm.

[J. Edlund]

Originally posted by Stian1979
I used to think that a diesel can't rev high and be efficiant.

You simply don't have as good timing control as with a spark plug.

I just read something about MTU now running 3 injection per combustion. They have one injection to start the combustion. one main injection and one afterburner injection. MTU is high reving engines so maybe they found a way to increase efficensy at high rpm.

GM is working on a new diesel V6 for premium cars (2.9 litre/250 hp), it will use up to eight injections per combustion (thanx to piezo electronic injectors). It also has pressure sensors in the cylinders so it can adjust the fuel injection based on real time data about the ongoing combustion. The main benefit of this is decreased emissions.

[Stian1979]

Preshure sensors you say? Don't seam like a reabile sulution to me, but then I would not imagine that real time meshurement off piston ring wear would be eater but sulzer pulled it off.

[revetec]

Here is a link to my Revetec Picasa Album

[Moon Tricky]

Originally posted by chaos_theory


I am new to this board, but I must admit I have thoroughly enjoyed reading this thread on alternative engine designs. I must admit I only understand the basics about engines and I am a complete novice when compared to the people on this forum. I just thought that everybody here may enjoy viewing a site I have found based on the quasiturbine engine, I just wondered what everybodies thoughts are on this engine and its practicalities. I was hoping this engine may be the "...story with a different ending" that McGuire is looking for.Here is the link, enjoy!
http://quasiturbine.promci.qc.ca/

The Quasiturbine makes me laugh. I mean, I've seen a few crazy engine ideas before, the result of deluded or dishonest minds perhaps, but this one just seems like a joke. Everything about it is wrong.

[Moon Tricky]

Has anyone ever built an engine that uses a Cardan crank? It seems like a more durable alternative to the scotch yoke. Although it uses gears so could be heavy and noisy.

[J. Edlund]

Originally posted by Moon Tricky


The Quasiturbine makes me laugh. I mean, I've seen a few crazy engine ideas before, the result of deluded or dishonest minds perhaps, but this one just seems like a joke. Everything about it is wrong.

Well, it's always funny to hear people that have come up with some crazy engine design talk about their big goals and their designs superiority over conventional engines. Especially when you know that the best thing they have done so far is an "air engine" that can driven a few hours between rebuilds.

[phantom II]

http://www.theengine...es turbines.htm

[Moon Tricky]

Originally posted by phantom II
http://www.theengine...es turbines.htm

Well it sounds interesting, and at first nothing "too" weird (we all know turbines work). Whether the engine is a joke or not, the company website certainly looks like a parody, and they're not giving too much away except for what looks like some sort of Celtic jewellery design. They also don't seem to have done anything since 2003... hmm...

[manolis]

Hello from Greece.

The second prototype of the Opposed piston Pulling Rod Engine (OPRE) is now running on Diesel fuel.



Video and photos at pattakon .

Thanks
Manolis Pattakos

[britishtrident]

Napier were going to build a hybrid power plant based on the the Deltic with the power turbine section of a Rolls Royce Nene in the middle of the triangle formed by the Deltic cylinders. The Deltic acted as the gasifier in place of the Nene's original centrifugal compressor and combustion chambers.


The big name in opposed 2 stroke diesels was Doxford but they only rotated at about 80 RPM

Junkers shared technology with Doxford pre WW1 and Napier pre WW2 ---- as later Napier did with Rootes for the TS3 Commer truck engine.