What research has been done on optimizing combustion in automobile engines?

[Curl]

I want to find papers of studies done on combustion in automobile engines. I know there was a lot of work doine on this, unfortunatelly I cannot find ANYTHING. If I type "combustion in engines" in the search field of any journal/search engine, I get completely unrelated junk.

I'm looking for experiments for things such as piston shape, head shape, combustion timing etc. People have tried to maximize the work done on the piston from the combustion reaction the entire time, and I want to know more about it (what was tried, what works, what doesn't, etc).

I was thinking of studying this type of thing myself for graduate studies, but I need to know what has been done first, so I don't try to repeat experiments that were already done.

Thanks in advance.

 

[SteamKing]

I would recommend you try the various professional societies dealing with auto design, like the SAE in the US or the IMechE in the UK. Also, try to limit the scope of your searches, so you are trying to find info on spark ignition engines or compression ignition engines. If you use a specific term in the search box, like "valve timing in SI engines", you probably will get more relevant hits than the more general "combustion in engines".

Given the number of engineers, mechanics, and back-yard tinkerers working on IC engines over the past century, I would be surprised that you DIDN'T duplicate something someone else has already tried.

 

[xxChrisxx]

Buy John B. Heywood - Internal Combustion Engine Fundamentals.

It goes quite deep, you'll never find a paper on combustion in engines because it's too broad a topic.

Also you'll find that pretty much everything has been tried already. There really isn't anything new to discover about the IC engine. When you read about some new revolutionary piece of engine design, and then realize the idea was thought up 20 years (nominal figure) after the engine was first invented. Almost all development now comes from materials science or control systems, which allows engineers to implement the old ideas.

EDIT: Basically, what Steamking said.

 

[mender]

Sounds like you already have a few questions, maybe we can answer them and save you some search time.

 

[Curl]

Yeah so I just thought up some ideas I could research but I just want to see things that were already done, that way I can avoid repeating (wouldn't be "research" if it was done already).
This way I can move on and think of something else. But I need to apply for grants/fellowships etc. so I got to figure this out pretty soon, that's why I was asking if there is some resource that documents such things.

SAE has a bunch of papers on ceramics and BS like that; I'm more interested in the dynamics of the combustion with application of maximizing force on the piston (could be a rotary piston, not necessarily the cliche cylinder).

xxChrisxx I took a look at the table of contents of that book and the last few chapters look really good. Thanks a lot. Any resources are welcome and appreciated.

 

[mender]

SAE has a bunch of papers on ceramics and BS like that; I'm more interested in the dynamics of the combustion with application of maximizing force on the piston (could be a rotary piston, not necessarily the cliche cylinder).

The force acting on the piston (or rotor) is psi times the effective surface area. For a given bore size, that leaves only the pressure in the chamber; maximizing the force means maximizing the pressure.

Sounds simple but isn't (obviously); what things are you wanting to research? Maybe we can point to more specific reference material.

 

[Curl]

rofl, the simple "pressure X area = force" formula is true for EQUILLIBRIUM situations only. During the 1ms combustion reaction, the gas is obviously not in equilibrium.

That's what I want to study.

 

[cmb]

It sounds like what you really need to read up on is fluid flow in pistons - swirl, stratified flow, variable stoichiometry, piston crown shape, valve timing. It's not surprising that you cannot find a really 'general' paper on IC engines. As mentioned, refine your question, be more specific, and there might be a better lead to offer you.

 

[DoggerDan]

I want to find papers of studies done on combustion in automobile engines.

Check the references for each of the articles linked under the Gas only cycles section: http://en.wikipedia.org/wiki/Heat_Engine#Gas_only_cycles

 

[mender]

Actually the "pressure X area" describes the force that is acting on the piston at any given instant; no equilibrium required. It is the cumulative net force that determines the output of the engine. Getting the highest average net force (BMEP) acting on the piston during a complete combustion cycle is the name of the game.

Maybe this will be along the line of what you're looking for:
http://www.circletrack.com/enginetech/ctrp_1004_engine_development_cylinder_pressure/index.html

Or:
http://www.epi-eng.com/piston_engine_technology/bmep_performance_yardstick.htm
If not, there are addition articles in the sidebars of each article.

Hard to know what you're really asking for and where you're presently at with your understanding of IC engines, so a little feedback would help.

 

[xxChrisxx]

rofl, the simple "pressure X area = force" formula is true for EQUILLIBRIUM situations only. During the 1ms combustion reaction, the gas is obviously not in equilibrium.

That's what I want to study.

Say, what now? And what happens at a single point in the combustion process matters... how?
See above, Mender is right, you are wrong.

 

[Ranger Mike]

Mender, great article by Jim Mcfarland,,I have read him for over 48 years..he is up there with Smokey Yunick , Duntov, imo

 

[mender]

Yes, I've also watched for his writing, always informative and clearly presented. Also like David Vizard for his clarity and thought processes.

 

[Curl]

Actually the "pressure X area" describes the force that is acting on the piston at any given instant; no equilibrium required. It is the cumulative net force that determines the output of the engine. Getting the highest average net force (BMEP) acting on the piston during a complete combustion cycle is the name of the game.

The only pressure that matters is the one on the boundary of the piston. What goes on elsewhere in the combustion chamber is irrelevant. So I guess that is my question, does the pressure vary with spatial coordinates in the combustion chamber, and if so, how (is it significant, at any point in time?).

It sounds like what you really need to read up on is fluid flow in pistons - swirl, stratified flow, variable stoichiometry, piston crown shape, valve timing. It's not surprising that you cannot find a really 'general' paper on IC engines. As mentioned, refine your question, be more specific, and there might be a better lead to offer you.

Piston crown shape, yes. That is what I was looking for too. I didn't know the name, that's why I have trouble searching for papers. I was never looking for a "general paper", on the contrary, I want HIGHLY specific papers.

I'll see what I can find now that I got better keywords to type in the search. Thanks everyone.

Update: Nope, haven't found anything. My googling skills must be really bad, all I found was this:
http://www.metacafe.com/watch/1755655/engine_piston/
but it has no information on the theory. What is the reason for making bowl shaped piston crowns?

 

[Ranger Mike]

Curl

The only pressure that matters is the one on the boundary of the piston. What goes on elsewhere in the combustion chamber is irrelevant. So I guess that is my question, does the pressure vary with spatial coordinates in the combustion chamber, and if so, how (is it significant, at any point in time?).

?

Your initial post stated that you were interested in the the piston shape, head shape, combustion timing etc. Then you totally disregard what goes on in the combustion chamber. What the hey hey? This goes contrary to basic problem solving and brain storming.

You also stated you were trying to seek government grants/ fellowships etc.. to explore this area. OK..

Is this an inquiry for the purpose of securing a grant or is it an endeavor to understand the combustion process?I think a bit of reflection and thought toward the goal would help. Specific, time bound, obtainable and measurable statement of your objective would help us help you.

 

[xxChrisxx]

Looking at a an indirect injection spark ignition engine is flogging a dead horse anyway, there's just nothing else to be learned. It's all a boring optimisation excersise.

The advancements now are high pressure direct injection, stratified charge and lean burn. Making petrol engines run more like a diesel.

 

[mender]

What is the reason for making bowl shaped piston crowns?

Some factors in deciding the shape of the piston crown are the valve angle and placement, which determine the shape of the combustion chamber in the head, and the desired compression ratio.

The majority of gas engines use a flat-top piston and shallow included angles on the valves (wedge heads and modern 4 valve heads), and the compression ratio is adjusted by varying the depth (and thereby the volume) of the combustion chamber. This basic configuration, along with a mostly central spark plug location, gives a relatively efficient burn by allowing the flame front to smoothly progress through the fuel/air mixture. A fast consistent burn that reaches all the outer edges of the chamber at the same time is the goal.

By having flat surfaces on the piston that match flat surfaces on the head and having the piston almost touch the head at TDC, turbulence can be generated to stir up the burning mixture and give faster more complete combustion. This is called squish or quench, and helps ensure that no pockets of the mixture lag behind the main burn. These pockets can either end up unburned or can cause the engine to be sensitive to detonation, both conditions lowering efficiency and raising emissions and the later possibly causing engine damage.

If a domed piston is used in a large chamber to get the compression ratio desired, the dome can temporarily block off some of the flame front and cause erratic and incomplete combustion, as described in the first article I linked. For example, a head with steep angles between the valves (old Chrysler Hemi) has a large combustion chamber and requires a large dome to get the compression ratio up. The burn on these engines is not very consistent or efficient so is not well suited for low emissions. The popularity of the Hemi at the time was mainly because the ports flowed well and the engines were able to make a fair bit of power for their size.

A current rule of thumb for present engines is that a dome of more than about 0.150" is going to start causing problems and costing horsepower. This is more of a concern with engines that are used for the higher levels of racing where every bit counts but should still be considered when deciding on a particular engine package.

On the other side of things, the Ford 1600 cc Cortina GT engine is an example of a successful racing engine that used a flat "combustion chamber" and a piston with a large dish. It was the mainstay of Formula Ford for several decades, mainly because of its rugged design and reasonable cost. The central dish allowed for a decent consistent burn and had a squish ring around the perimeter of the piston to also help the burn.

The power was good for the day ('60s) but the straight-up valve design required for the flat head limited the port flow and cam timing and thus power. These limitations are why gas engines are not designed to use pistons with large dishes; most modern 1600cc engines produce considerably more than the 110-115 hp that the GT engine made in race trim, and are much cleaner as well.

Large domes or dishes expose more surface area of the piston to the high combustion temperatures generated, requiring more cooling to keep temperatures reasonable and wasting heat that otherwise could power the vehicle. As a result, both extremes are avoided unless a particular shape has a benefit that offsets the heat loss.

Did that help?

 

[Fahlin Racing]

I want to find papers of studies done on combustion in automobile engines. I know there was a lot of work doine on this, unfortunatelly I cannot find ANYTHING. If I type "combustion in engines" in the search field of any journal/search engine, I get completely unrelated junk.

I'm looking for experiments for things such as piston shape, head shape, combustion timing etc. People have tried to maximize the work done on the piston from the combustion reaction the entire time, and I want to know more about it (what was tried, what works, what doesn't, etc).

I was thinking of studying this type of thing myself for graduate studies, but I need to know what has been done first, so I don't try to repeat experiments that were already done.

Thanks in advance.

Here are some names you should look for besides the SAE papers. Look into patents and read them if you come across a related piece.
Charles Fayette Taylor
Sir Harry Ricardo
Larry Widmer - check out his Soft heads article that debuted in the mid 80's
Smokey's Hot Vapor Engine is a good example of fuel conditioning (its a very simple machine)
Jim Mcfarland has some great articles on reading burn patterns and other combustion topics
I haven't looked for what Darin Morgan of Reher Morrison Racing engines has as far as combustion. Air flow, as some call it the working fluid, has a direct hand in how our combustion process occurs and how efficient it ends up.
Michael May from Switzerland I believe. I haven't gotten to read any of his work yet.
The list goes on, but I can't name much off the top of my head right now.

Studying lean and rich burning rates is a long topic in itself. Combustion is pretty wicked!

The list of designs/theories tried is probably so great, your brain might just be in overload trying to think what has not been tried.

 

[Fahlin Racing]

...I'm looking for experiments for things such as piston shape, head shape, combustion timing etc. People have tried to maximize the work done on the piston from the combustion reaction the entire time, and I want to know more about it (what was tried, what works, what doesn't, etc)...

Just look at engines throughout the years as far as chambers and pistons used. There is an immense amount.

The stuff that doesn't or didnt work probably isn't able to be found unless there is some shelf untouched collecting dust or in the recycling I am sure. The past designs are out there for everyone to see you just have to find them.

The only pressure that matters is the one on the boundary of the piston. What goes on elsewhere in the combustion chamber is irrelevant. So I guess that is my question, does the pressure vary with spatial coordinates in the combustion chamber

Pressure is the result of combustion. WHAT HAPPENS IN THE CHAMBER IN ALL AREAS MATTERS.

Mender wrote

By having flat surfaces on the piston that match flat surfaces on the head and having the piston almost touch the head at TDC, turbulence can be generated to stir up the burning mixture and give faster more complete combustion. This is called squish or quench, and helps ensure that no pockets of the mixture lag behind the main burn. These pockets can either end up unburned or can cause the engine to be sensitive to detonation, both conditions lowering efficiency and raising emissions and the later possibly causing engine damage.

Squish is the action done by the piston
Quench is the area its done at which is the cylinder head

If these are too weak or too strong combustion will not be optimum! Another aspect many overlook are the crevice volumes of the combustion space.

EDIT: Research lean and rich A/F mixtures burning rates to begin your pursuit for your goal. Have fun with it.

 

[mender]

Here's a link to another discussion (and a pretty good forum):
http://speedtalk.com/forum/viewtopic.php?f=1&t=3652

There are people on that forum who are actively researching combustion chamber shape.

 

[Curl]

mender you are a beast, thanks a lot.

I can't really dent the more practical side of engine design, it has been overdone. What I got in mind was one of my old questions I had for which I found no answer.

What I am thinking is this:
When a substance is burned, all chemical energy is released as an initial kinetic energy to the product particles. From then, entropy increases until equilibrium.
So my question is this: Can we somehow capture the chemical energy released soon after the reaction (BEFORE we give time for entropy to increase). There is no reason why it shouldn't be possible, since at any time, microscopic interactions are reversible (see http://www.wolframalpha.com/input/?i=Boltzmann's+paradox).
For example, is there a way to somehow focus the particles to move in a biased way (initially), in a highly ordered fashion such that it hits a piston (or whatever) with a higher force than it would after the gas is allowed to reach equillibrium (when entropy is maximum and all particles are moving in all directions).

Here's one idea I thought of trying, which brings the 2nd question. I asked it here: (https://www.physicsforums.com/showthread.php?t=526641)
Can I model a highly explosive charge (like a small gunpowder grain) as a collection of particles. Then, I could design the chamber shape such that they'll move together towards my target and hit it (initially) with a greater force than they would at the equillibrium pressure.

I was thinking that one application for this could be IC engines (since I like that subject) but it doesn't have to be, its more of a theoretical question about particle dynamics. I want to study this during grad school, it beats any of the lame research that is going on at my university. So I'd need to find my own money for tuition, since I don't have $30,000. I don't need anything to fund the reserach because it would not cost that much (I can build anything in the shop, aluminum/steel is cheap) I just want some kind of scholarship to pay for tuition while I'm working on this.

 

[Fahlin Racing]

Using the description 'explosion' with regular combustion in an Otto Cycle engine/ICE is only going to add confusion. It simply doesn't exist until certain conditions are present. Two completely separate rates of oxidation occur as well.

...Can we somehow capture the chemical energy released soon after the reaction...

Are we talking about holding this chemical energy and not allow work to be done, or, are we wanting work to be done on the object?

What are you thinking as far as harnessing?

is there a way to somehow focus the particles to move in a biased way (initially), in a highly ordered fashion such that it hits a piston (or whatever) with a higher force than it would after the gas is allowed to reach equillibrium (when entropy is maximum and all particles are moving in all directions).

Swirl chamber created by Sir Harry Ricardo?

 

[Curl]

Using the description 'explosion' with regular combustion in an Otto Cycle engine/ICE is only going to add confusion. It simply doesn't exist until certain conditions are present. Two completely separate rates of oxidation occur as well.



Are we talking about holding this chemical energy and not allow work to be done, or, are we wanting work to be done on the object?

What are you thinking as far as harnessing?



Swirl chamber created by Sir Harry Ricardo?

swirl chamber is to create turbulence of the incoming gas BEFORE combustion. I'm talking after combustion, so it is irrelevant.

I can not mention combustion engines at any point in the thesis, I don't really care. And I can use gunpowder or such explosives for the test since it would better support my theory.

So did anyone here know if I can do an M.S. degree in M.E. without paying for all of it myself and without joining one of the lame labs at the university?