The Bourke Engine 4

[SBBlue]

Okay, kids, here's your assigment: To learn all about the Bourke Engine.

Go visit this website and watch the animation;

http://bourke-engine.com/ani.htm

Supposedly this engine has superior fuel economy and emissions characteristics. As far as I can tell, it is a two stroke engine. Instead of using crankcase scavenging, it uses the lower portion of the cylinder to pump the air necessary for charging the combustion chamber.

It is also claimed that the "Balanced Precision Reverse Cam Effect Roller Crankshaft" did good things too, although from the animation it looks to me that it just results in the piston spending more time at TDC and BDC, and I'm not sure the advantage of that. It apparently is also known as a "Scotch Yoke." The engine is also supposedly "self supercharging."

It is also claimed that the exhaust gas temperature is 190 to 240 deg F, the compression ratio varies from 8:1 to 20:1, and that the air/fuel ratio is 30:1 to 50:1.

I have spent some time looking at the animation, and while I would believe the engine would run, I just don't see how it is "self supercharging", I don't see the advantage of the "Scotch Yoke", and I don't quite understand how it would operate with a 30:1 to 50:1 fuel/air ratio.

If you could get ignition at an air/fuel ratio of 50:1 I could understand why the exhaust gas temperature would be quite low. In addition, the combustion temperature at an A/F ratio of 50:1 would be quite low, which would explain low nitric oxide production, and the PM's might be low by virtue of the excess oxygen present in such a lean condition. But it looks to me that the power density of such an engine would be absymal.

More information on the engine can be found at:

http://www.constant-pressure.com/Home.htm

I must also confess that I don't quite see how this would be a "constant pressure" engine, since it looks to me closer to a "constant volume" engine.

An interesting and somewhat different view of the history of the Bourke Engine can be found at:

http://www.niquette.com/books/sophmag/bourke.htm

Does anybody have any insight about this that I am missing?

 

[ivymike]

Unless I have missed something?
heheheeh... probably the same thing I'm missing. At first I thought "oh, this is just a simple terminology thing. Greg is talking about balancing as it relates to mass distribution within the engine, and B30 is talking about... um... well... something else."

 

[patprimmer]

##@!!&&*

I just spent about an hour on a post, and got a page expired message.

I will see if I can find another hour to invest into this at a later date

Regards
pat pprimmer@acay.com.au
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[patprimmer]

Here is an abridged version that took considerably less time, and is probably more concise, precise and less provocative, so maybe the timeout was a good thing after all

For my previous post, I was missing a lot about this engine, as I must confess I never read all the posts, and as the links seemed to go to sites with technically poor content, I did not spend much time on them.

I have since attempted to rectify this, but after to much research when the quality of the source information is taken into account, I must admit I am still missing a lot, including nearly half a day of my time.

On all the links I visited, I could not make an animation or video work, so I still have not seen the cycle and I am trying to imagine it from the very few drawings an photos of parts

There are minor differences in piston acceleration rates, and this engine has a small advantage in the piston having pure harmonic motion, and certainly no side loading is an advantage, however the pistons on each side travelling the same direction, as Greg points out will be a balancing disaster.

My comments in my previous post are based on petrol and spark ignition as the fuel.

I see no difference between the way fuel would burn in this engine compared to any other 2 or 4 stroke piston engine.

I see no supercharging as the air below the piston is squeezed into the same volume above the piston.

Lean mixture will result in detonation and destroy the piston, unless it is built to diesel standards that withstand detonation.

The only valving I see in the sketches and drawings are piston port type like any modern 2 stroke. As there is no apparent scavenging or supercharging, I don't see how it runs at all, if the cylinder with residual exhaust gas is over atmospheric pressure.

In my previous post I was taking power density rather than thermodynamic efficiency into account, and my views would soften considerably if only TE was being considered, however I expect that all engines must be a compromise between inertia losses from reciprocating weight, thermal efficiency via expansion ratio.

To answer SBBlue's comments directly:-

To have peak pressure by TDC, you must ignite the fuel considerably before TDC unless you have instantaneous combustion. This time to burn generates some pressure well before TDC, and considerable pressure a little before TDC, all of which resists rotation of the engine.

Even if you have detonation, you still need some time for the pressure to build up before TDC so it will be maximised by TDC.

I agree, using prolonged combustion to maintain peak pressure for a longer portion of the power stroke will give higher power density, but very poor conversion of the heat to mechanical pressure, all other things being equal.

Re NOx emissions. I have been taught that lean mixture, high compression and to much advance all lead to NOx emissions. The high compression and/or excessive advance generates more peak pressure, and therefore more heat. In the presence of free oxygen (from lean mixture) and nitrogen, NOx is then formed. I have never seen evidence to the contrary on this point.


Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
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[btrueblood]

I guess I'm confused too. I don't see how this engine cycle is any different than a standard Otto or Diesel engine, except and unless there is an external blower/supercharger on the engine (its presence in photos/drawings on the various websites escapes me).

I'm also a bit disappointed by claims of higher thermodynamic efficiency, without any substantiation: can someone please post a link to measurements of BSFC, or any other measurement of efficiency, or even power output, or fuel consumption, or practical application of the motor?

BT

 

[crysta1c1ear]

Pat said:
Re NOx emissions. I have been taught that lean mixture, high compression and to much advance all lead to NOx emissions. The high compression and/or excessive advance generates more peak pressure, and therefore more heat. In the presence of free oxygen (from lean mixture) and nitrogen, NOx is then formed. I have never seen evidence to the contrary on this point.

Crystal Clear:
I believe the main cause of NOx is caused thermal Nox coming from these reactions
N² + O => NO + N
N + O² => NO + O
the rate of reaction increasing with the square root of the pressure, and increasing exponentially with temperature, hence the name thermal NOx.

At lower temperatures, (and high pressure) another pair of reactions is involved
N² + O => N²O
N²O + O => NO + NO

In rich mixtures this can happen
CH + N² => NH + CN
NH + O => NO + H
CN + OH => NO + CH

Also, there can be nitrogen in the fuel causing NOx as well as nitrogen in the air causing it.

Reportedly stoichiometric mixtures give the most NOx, but that defies common sense if you look at it like this. In a stoichiometric mixture, oxygen should be largly used up and less should be available for the thermal NOx reactions. (Maybe this is the logic behind Pat's statement. Its not for me to say.)

However if you look at it differently, stoichiometric mixtures should give higher temperatures, and if thermal NOx production is exponentially linked with temperature, then there are reasons for stoichiometric mixtures giving higher thermal NOx than lean mixtures.

With 'fuel in for coolin' it should be clear that rich mixtures reduce thermal NOx, but I don't think that can be extrapolated to conclude that lean mixtures generate more Nox, unless you are in some sort of supercharged race environment where lean might just mean 'a bit rich but less rich than normal'.

Back to the Bourke engine for my next post hopefully.

I like the point about the Bourke engine volumes above and below the piston being the same and therefor there is no supercharging effect. I think I disagree, but I'd have to see the pictures again to check and see if I could argue a case for my opinion.

 

[SBBlue]

I essentially agree with all of PatPrimmer's latest post. I concur that fuel ignition has to start before top dead center to allow for maximum pressure at TDC. That's why I said that the optimal situation would be fore instaneous combustion at TDC. Combustion starting before TDC will add extra load to the engine, and combustion persisting after TDC will decrease efficiency.

As far as nitrous oxide being a function of temperature and pressure. . . . .I think what confuses most people is that compression, and therefore increased pressure is accompanied by increased temperature. The higher the compression ratio, the higher the temperature of the compressed gas. The higher the temperature of the compressed gas, the higher the peak temperature at combustion and the higher the NOx production.

However. . . .it is possible, if you split up the compression process and use inter-compressor cooling, to have a pressure that is just as high but a temperature that is much lower. That will result in a lower combustion temperature and hence less NOx output. This is the approach used by Caterpiller in their ACERTs engines (plus some other stuff).

 

[GraviMan]

I would imagine that water injection would also help with NOx. By turning to steam, the compression and combustion temperatures are lowered. It looks to me like the Bouke engine is really just trying to use the cooling circuit to accomplish the same thing.

On it's own water injection cannot be justified thermodynamically. When you take into account cooling heat rejection and emissions, maybe it starts to look better. Exhaust temp will still be ~100'C.

Must admit though I still don't really see why it should offer better sfc...

Mart

 

[WGJ]

Could someone help the terminally confused, please?

On the

http://bourkeengine.net/home.htm

website, the multi-fuel capability of the engine/cycle is cited as "any low grade fuel (diesel, jet fuel/kerosene, home heating oil, brown distillate, ect.)".
I finally got the SolidWorks model to download and run and it depicts an engine which appears to be compression-ignition, as does the animation on

http://www.niquette.com/books/sophmag/bourke.htm#specifc

a compression ignition/diesel cycle then aligns the fuels quoted and the models/animations.

I also managed to finally get the video from

http://bourkeengine.net/videoclips.htm

to download and run and this clearly shows what appear to be two spark plugs in the finned cylinder head. If these are spark plugs and not glow plugs for preheating, what part do they play in the function of the engine when running on classical low-quality diesel fuels?

 

[Bourke30]

Wow! Looks like old Russ Bourke is still stirring the I/C pot.
There are no hidden weights. Bourke's dynamic balance works exactly as he describes it. I ripped more than one lord mount trying to get the cylinders in sync. All forces are equal and out of phase by exactly 180 degrees. We have a 5000'/sec. explosion divided by 180 gegrees. I know it is counterintuitive, but it works. 100% dynamic balance is achieved. The faster it revs, the smoother it gets. Regular engines can only achieve a compromise.
Bourke claimed top RPM as high as 20K. It cannot "fly apart", because the rod assembly is always being compressed. My design intent was 4000 RPM to power the generator, although I have taken it to 8000, unladen, otherwise my armature would have disintigrated.
There are two plug holes to the combustion chamber. Ignition is used, initially, to bring the engine to proper temperatures before introducing the heavier fuels. My video clearly shows the ignition being cycled on and off with no variation in performance. I was very surprised the first time I saw this happen. The second hole is used for varying the compression, or the introduction of test devices.
Charges are ignited before TDC, where the slow burning carbon element of the fuel is used as a "fuse" to trigger the explosive combination of the hydrogen content and oxygen, (association) just past TDC. All energy is released earliest in the cycle, which is an requirement of the four-cycle formula. At what temp does association occur? It is well below the NOx threshhold. Rapid expansion of the spent charge cools the cylinder. Cylinder walls are not bathed in flame for the period of the stroke.
Please do not confuse my sites with others. We are not in agreement with some of the info on other pages. Mr. Niquette trounces the Bourke Cycle and condems it on the basis of one engine reviewed. With his sophistication, he should know that a valid statistical result requires a population of more than one sampling. He is invited to review my video frame by frame.
Please don't discount this work because you were not patient or computer savvy enough to get our downloads. Yes, they are a little long, but will go a long way in convincing the skeptics that the Bourke Cycle is superior to Diesel. Diesels suffer from "pressure drop", because of the geometry generated by tyhe crank. Bourke is cam based and has a longer dwell at TDC. Longer fixed volume reducing pressure drop. Maximum pressure is developed earliest in the cycle and is coupled with maximum mechanical advantage. Kinetic energy imparted to the rod-yoke assembly is transferred to the cam, as well as compressing and charging the opposite cylinder . Actually, it is doing intake, compression, power, and exhaust with one movement of the rod-yoke assembly.

The graphics are sufficient to give a clear view of the mechanism. The Solid Works animation is the best you will find on the web. If this does not do it for you, get a copy of the "Bourke Engine Documentary", and follow every function. Beware though, you will have to shed most or your established notions of internal combustion theory. Bourke reduces this theory to physical fact. His research is tough to beat. Too heavy for many readers, but still factual.
So, a timed detonation is not impossible to attain, give GOOD mechanics. And, yes, the EGT is lower than anything currently available. The difference between maximum heat produced and EGT is a true indicator of efficiency.
<

http://bourke-engine-project.com>

<

http://bourkeengine.net>

There are no tricks. Russ Bourke designed a mechanism better suited to take full advantage of the forces mother nature designed into our fuels.

 

[ivymike]

There are no hidden weights. Bourke's dynamic balance works exactly as he describes it. I ripped more than one lord mount trying to get the cylinders in sync. All forces are equal and out of phase by exactly 180 degrees.

What exactly do you adjust when you're getting the cylinders in sync? The reciprocating assembly shown in your solidworks-generated .avi video is clearly unbalanced, assuming that the reciprocating components have mass. If they're massless, then you're right, it's probably perfectly dynamically balanced. Fyi, gas forces (due to combustion, compression, etc) do not play a role in balancing.

From the site:
emissions: Russell Bourke, the inventor, stated the exhaust components were carbon dioxide and water vapor.
Exhaust Temperature: Russell Bourke, the inventor, stated that matches could be held in the exhaust without igniting.


Do matches burn particularly well in an atmosphere of carbon dioxide and water vapor?

 

[GregLocock]

Grins. Um, if the mixture is lean then surely there will be oxygen in the exhaust?

Bourke30, what we'd really like is test results. Fuel consumption, emissions including NOx, power output, airflow, you know, that sort of thing. Disparaging people's computer skills is not going to work, and pretty animations prove very little. Incidentally anyone who can make a 14 Mb file out of a 10 second animation can scarcely boast about computer skills.




Cheers

Greg Locock

 

[SBBlue]

I ran some brief thermodynamic calculations on the Bourke Engine using the air standard tables, and I am somewhat perplexed.

Assumptions: 18:1 Compression ratio. Exhaust Temperature: 200 deg F.

The 18:1 compression ratio is given on one of the web sites. I'm guessing on the temperature, since supposedly the exhaust gas isn't hot enough to burn your hands. This would mean that the temperature is somewhere around 120 deg F, since higher temperatures will certainly burn human skin. For calculation purposes I will assume the exhaust gas temperature is 200 deg F, which is high enough to burn you quite well but considerably below the typical diesel or gas exhaust temperature. Note that this comparatively high temperature assumption works in favor of the Bourke engine.

Ambient (80 deg F) air that undergoes a 18:1 compression will have a temperature of 1157 deg F. Gas in a piston that undergoes a 18:1 expansion, winding up with an exhaust temperature of 200 deg F will have a temperature of 1456 deg F at full compression. The difference in temperature between gas at full compression prior to combustion and after combustion allows us to calculate the amount of energy added from the fuel; this turns out to be 60.8 BTUs per pound of air.

Now if we assume a completely adiabatic engine with no friction losses, the efficiency of this engine will be about 68%. But those engines are hard to come by. An engine thermal loss and much more realistic compression and expansion efficiencies of 91% will only have an efficiency of about zero percent. And the 91% efficiencies are considerably better than typical engine efficiencies.

Let's assume, though, that we have some magic engine elixir that takes away all friction and prevents any heat losses, and does have efficiencies of 100%. The energy density will be about 40 BTU/lb air. In comparison, a normal gas engine would be expected to have energy densities of at least 300 and maybe 400 BTUs/lb air.

To put this in perspective, a 350 cubic inch engine might be expected to have a maximal power output of 30 hp instead of 300 hp.

The air/fuel ratio for the engine? 329:1, a tad higher than the stoichometric ratio of 14.55:1 and the typical diesel engine ratio of 30:1.

Color me a little bit skeptical about the engine.

 

[ivymike]

does crayola make that?

 

[Bourke30]

Since the design is clearly "unbalanced", how does it run so smoothly in the video? Rethink the dynamics. I was skeptical, but it can and does run very smoothly, and maintains its' character for all RPM's. One ignition piick-up is moved ever so slowly , while running, so as to achieve the "null" between the two alternating explosions. This can also be done electronically. At no time have I stated that the exhaust will not burn the skin. It is relatively cool compared to conventional engines. Paper matches will not light in the exhaust stream. Since they would be in the atmosphere outside the engine, there would be sufficient oxygen for them to ignite. As far as computer skills, we are all on a learning curve. The content is the issue. Don't shoot the messenger.
I am not a college educated thermodynamicist. I am a hobbiest, and I know what I see. These engines run smooth and have a very low EGT, period. Fuel consumption and power output appear to be what Bourke predicted, following the curves he published. A two-stroke that doesn't pump-out clouds of blue smoke? Why would anyone do research on that?

 

[GregLocock]

We are talking about balance. This is solely about masses and inertia. We know, because some of us have done this for real engines, and others because they paid attention in class, that you cannot have a truly balanced reciprocating system with a crank, in all planes, unless there is another system around to counterbalance it.

This is not some fancy pants theory, this is fundamental physics.

So cut the attitude and give us some test results.

Reasons why it appears to run smoothly in the video.

1) The reciprocating masses may be very small compared with the engine mass.

2) 1 mm of displacement on the block is an engine destroying 40g at 6000 rpm. Do you think you could see 1mm (40 thou) of vibration on that video?

"As far as computer skills, we are all on a learning curve. The content is the issue. " . You were the one who started criticising computer skills.











Cheers

Greg Locock

 

[SBBlue]

Bourke30 wrote:

"I am not a college educated thermodynamicist. I am a hobbiest, and I know what I see. These engines run smooth and have a very low EGT, period."

No problem. Most engineers don't understand thermodynamics well enough to do basic calculations.

I made the assumption of 200 degrees for the exhaust temperature because of the picture of someone holding their hand over the exhaust port. I was assuming that this meant they could hold it there for some time without burning themselves.

Just because heat is not transferred does not mean that an object is not hot. Example: Heat your oven to 500 degrees F. Open it, and stick you hand inside, taking care not to touch any parts of the oven. Even though the temperature of the air in the oven may be 500 deg F, your hand won't burn if you only leave it exposed for a short time.

So. . . . .what is the temperature of the exhaust gas? It's really not all that hard to get a temperature probe that goes to 1800 deg F. Your local electronics store will have one; they shouldn't cost more than perhaps $50. That would settle the question of exhaust gas temperature.

And while you are at it. . .what fuel are you running in the Bourke Engine? What type of ignition to you use? What is your air/fuel ratio? What is your specific calculated power output?

I would be interested in hearing more. . . .

 

[patprimmer]

Bourke30 confessed he is a hobbyist.

Hobbyists have no place here, so why do we argue with him.

I believe that it is only because of the considerable volume of sound input into this thread from the professional engineers that it has escaped the red flag thus far.

If we wish to preserve the valuable content, it might be an idea to cease arguing the merit of obviously misconceived or fraudulent claims made by hobbies ts.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[WGJ]

Gentlemen,Shakespeare wrote 'Friends, Romans, Countrymen' - this time let's try 'Professionals, Engineers, Hobbiests'.

I delve into Eng-Tips regularly to see what's going on. I stumbled across these interesting and informative forums about eighteen months ago and I'd like to think I've helped one or two people along the way - I don't contribute or question much unless I am sure of my ground. Otherwise I check in to browse and learn from other people's knowledge and experience.

As a background note, I've been in the automotive industry in the UK for 28 years, virtually all of that time in association with engines, and about 2/3 of that time on fuel delivery systems, gasoline and diesel.
I've found that some 'professionals' sometimes have the strangest notions about the way the internal combustion engine operates and how its support systems need to function in order for the engine to give its best.
I've had the dispiriting experience of working with managers that didn't have the most basic notions of thermal efficiency and heat transfer, and I've worked with other 'professionals' that couldn't read an engineering drawing to save their project.

Before I came to the auto industry I was an apprentice and then a draftsman in the defence industry, where, in retrospect, standards of competance and knowledgability were higher and wages lower (in the UK at least!) - and that statement is in no way critical of any of the contributions made to this thread by the names I recognise as regular contributors to the Engine and Fuel Engineering Forum. I recognise their valuable knowledge base and I think I have personally profited from the other threads they have contributed to.

As many of you will probably know, the engineering education system here in the UK is somewhat different to that in the USA and my academic qualifications are difficult to compare - however, I got my Joint Institutes HNC (Higher National Certificate, awarded by the UK institutes of aeronautical, mechanical and electrical engineers, probably equivalent to a basic US college degree) in Production Engineering at the age of 20 in 1971 and didn't get my University degree in Automotive Engineering until 2000 at the age of 49.
I'm now a Chartered Engineer with the UK Institute of Electrical Engineers - the status recognised as a 'professional' in the UK.

Quote "Please don't discount this work because you were not patient or computer savvy enough to get our downloads".

Whilst I may not be the biggest personal computer whizz about the place, I can usually make them do what I want and I've also put a few together and un-wrecked some as well.
It never ocurred to me to check the file size on the video as I expected a maximum of, say, 4Mb, and a larger file for the SolidWorks animation.
Knowing my home dial-up would take forever anyway, I am guilty of using the Company's facilities. I work for a big company, one of the US giants, and the Internet connection I have is of 'broadband' capability and more, even given the virus scanning that takes place on all downloads - so when the file took almost 15 minutes to download I was surpised. I should have known! Dummy!

If anyone is still reading - here's the point.

Data - that's what this is dicussion is all about. Notions are fine when a project is in it's infancy. Notions from experienced minds are where some of the best designs in engineering have come from. Not all inovative steps are the fruit of dry research.
However, in this case, it looks like academia should now be the place to fully define the benefits, or otherwise, of the combination of fuels, ignition mechanisms and mechanical mechanisms that apparently give this power unit its claimed unique properties and capabilities.
Velocity diagrams of the power conversion components could be a valuable 'next step' in clarifying the power unit's properties.

If this power unit is 'the business' in suitable applications, then the proponents should get a university or research outfit with the right academic and practical background to get interested and research:

- theoretical and actual balance and vibration of a power unit

- comprehensive performance curves (power, torque, coolant and lubricant temperatures, intake and exhauste temps, etc

- durability

- actual exhaust chemistry and fuel economies of a power unit that has a practical power to weight ratio

- etc.

I would never disparage the 'hobbiest' or those companies that are 'out there', you only have to look at some of the work of model aero enthusiasts, and radio and electronics enthusiasts to see how much a combination of knowledge and outright enthusiasm can do and how some of it (especially currently in radio, electronics and computing) can creep back into industry.
I remember the first time I had a drive of an Orbital engine powered car, I wanted one there and then.

But -- if the claims for the Bourke cycle are to be upheld as fact rather than claims with various levels of substantiation, then perhaps a friendly university or interested corporation may be able to help provide the vital links between notions, appearances and full substantiation.
Meanwhile - I'll be off to look for the Bourke Cycle papers to educate myself some more about it's properties.

 

[schwee]

I have some questions about NOx emissions, if I can backtrack a bit.

per patprimmer 8/31:
>>>>Re NOx emissions. I have been taught that lean mixture, high compression and too much advance all lead to NOx emissions. The high compression and/or excessive advance generates more peak pressure, and therefore more heat. In the presence of free oxygen (from lean mixture) and nitrogen, NOx is then formed. I have never seen evidence to the contrary on this point.<<<<

I think there might be some explanation of the low NOx claim if we consider the Bourke engine to be a “knock engine,” or “detonation engine.” I’m pretty sure that’s what it is – how else can you run an 18:1 compression ratio at lean mixture, and start things out with a spark plug? So, I’m gonna posit the thing is a knock engine, or what I think most people would call a homogeneous charge compression ignition (HCCI) engine. Hallmarks of such an engine seem to be, to date, really poor power density, inability to handle much of a range in loads and speeds, and real trouble controlling the moment of combustion (if you’re too rich, you knock really hard, and if you’re too lean, you don’t fire at all). They also tend to run unevenly, and wear and durability are problems due to the sudden impact of detonation.

But there does seem to be at least one redeeming quality – HCCI engines are being found by pretty reputable outfits, across the board, to have really, really low NOx emissions (see below).

I THINK the explanation given is that it's not exactly the heat that leads to NOx, but the duration of peak temperatures. HCCI engines have a very fast "burn" rate, as mentioned earlier in this thread, so the temperature and pressure peaks, although actually higher than in diesel or spark engines, end up not being sustained long enough for NOx to develop. That’s what I’ve heard – does that make any sense?

And if it does, how does that compute with what I'm reading in another thread that running lean makes things really hot? One would think if cylinder walls and piston heads got really hot during HCCI combustion, which I think is usually pretty lean, that high temperatures would be sustained and thus NOx would still be a problem???

http://www.windsorworkshop.ca/downloads/TomRyan.PDF

(p. 6 and p. 19)

http://www.gmrc.org/gmrc/pdf/gmc03/23-HighPowerFourStrokeLeanBurn.pdf

(p.14)

http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/26938ss.pdf

(p. 5, bottom; p. 11 - end?, my computer's too slow)

http://www-personal.engin.umich.edu/~mswool/publications/rpf.pdf

(p.2)

 

[patprimmer]

As I understand it, going lean results in higher exhaust gas temperatures to a point, then leaner still goes cold.

I think the higher exhaust temperature when lean, is more an indicator that when rich, there is excess fuel to help cool the charge by latent heat of vaporisation, but when the mixture is optimum for economy, there is no excess fuel to cool the charge, then when leaner still, there is less fuel to burn, thereby generating less heat.

A HCCI engine might meet some of the claims made by the Bourke engine, but there is nothing about the Bourke engine that suggests it is more suitable to HCCI than a convectional crankshaft and connecting rod engine might be.

Regards
pat pprimmer@acay.com.au
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