olddragger

iTrader: (3)

i am listening and i am reading but i do not see where you are coming from Jeff.


" First of all, it doesn't - it moves forward and back based on ignition timing and load."

Load itself moves the point of combustion? Uhhhhhhh--you have lost me again. Load is recognized by the tune so the tune changes the timing and isnt that what changes the location area of the combustion? Load is a primary influence, but in itself it cannot change where the combustion occurs.

You still dont understand that we are speaking of 2 different things. I am speaking of the physical location of the combustion chamber---the area that is available by design for a combustion event to occur. I believe you are speaking of the combustion event itself.
And again a recip engine is the same--it has a dedicated space for an combustion event. All engine do. The rotary is no different.

MazdaManiac

iTrader: (3)

No you are not. Watch the video.


You don't realize that the combustion event moves to different points around crank rotation? What do you think detonation is? Do you know what flame front speed is?


IS MOVING. The "pocket" between the rotor face and the housing IS THE COMBUSTION CHAMBER.

This is retarded. Unless you can find more people other than you that don't get this to join in, I am not going to waste my time on just you.

olddragger

iTrader: (3)

i knew we where talking about different things.
I am talking about where the combustion occurs--thats the combustion chamber. NOT THE ENTIRE 4 STROKE CYCLE.
Again where the combustion occurs--the red shaded area in your diagram. That is where combustion chamber is located basically speaking. It is not a combustion chamber during the intake and exhaust phase of the cycle--at least we hope not. It does not move position.
The face of the rotor has multiple duties just like that diagram of yours shows.
The rotary face's duty is identical to the piston in a recip. It is part of the mechanics that lets in the charge, helps to compress the charge, helps harness the energy for combustion and helps to evacuate the spent combustion gases. Just like a recips piston it sees all 4 cycles..
Now what we do have is a moving cylinder head.

MazdaManiac

iTrader: (3)

No, it is not.

No, it is not.

Yes, it is.

Yes, it does.

Is the "combustion chamber" not the "combustion chamber" during the intake portion of the combustion phase on a piston motor? No? Then what is it? The "intake chamber"?!?

So, apparently, you don't understand what "combustion" is.

The combustion event occurs over a wide range of crank rotation; between 44° before top dead center to 130° after top dead center or even later.
It doesn't even really have an exactly correlated event window tied to the spark timing, which also moves between 44° before top dead center to 15° after top dead center or even later.
In this drawing, this is during the "yellow" portion until the end of the "orange".

In case you didn't realize it, the rotor is moving during that time.

If the start of the combustion event waits until a spark plug fires (which would be a good thing), it will then progress across the rotor face, rolling as it does as a result of its own inertia confronting the advancing rotor face, moving it along in a separate vector than that of the advancing flame front (which advances at a rate proscribed by it density and composition).

The idea is to time the total advance of these two actions to coincide so that their maximum resultant pressure occurs when the rotor face is at 15° or so after top dead center. (Which is about the "red" portion of the drawing above. The point where the combustion chamber suddenly becomes "the combustion chamber" according to your completely absurd and misinformed reasoning.)

On my particular car, when Ve is very low, I fire the trailing plug even earlier (up to 60° before top dead center) to begin the combustion event even earlier in the vicinity of that plug, which is an indication (well, it should be, but I doubt you are still even reading this) that the conflagration part of the combustion cycle is not a single event.

ganseg

iTrader: (5)

I'm learning something - just don't know enough to contribute... Thanks!

Flashwing

This is the part that makes me giggle inside...I know it's weird.

The complexity of the rotary is revealed through this aspect because a piston motor shows that a combustion event happens in the same spot every time. In the case of the rotary, combustion is happening while the rotor is shoving it along towards the exhaust ports to kick it out of the motor.

I say its complex because the amount of variables present are, I feel, much larger than a piston motor would demonstrate and thus you have a larger variations of how the charge burns.

Until reading this I never considered the combustion chamber as a moving object but the true definition of a "combustion chamber" is where ever the charge happens to be at that particular moment.

It's kind of like saying my home is always in Indiana even though I live in Arizona while the truth is my "home" is a variable dependent on where I am at any given moment. Hopefully that is a proper analogy.

Let me backup here.

Jeff can you clarify one thing: You speak of the combustion event as being separate from the flame front...can you explain the difference between the two? I've previously seen them as the same thing.

Second, does the combustion charge actually slosh around the rotor face much like a liquid does when the container is rocked back and fourth? Reason I ask is as the rotor advances it does reach a stopping point when the next combustion cycle beings. Does the charge or flame front actually crash into the opposite side of the rotor face near the exhaust port and then get swept out?

MazdaManiac

iTrader: (3)

Well, that definitely makes me feel better. Tutoring just OD on what should be absolutely the most basic and fundamental concept of the rotary engine would be a monumental waste of time.

That kinda works!

The flame front is the edge of the charge that is actually burning at any given moment. It starts where the plug(s) fire and, in the best of worlds, progresses uniformly out like burning grass.
The conflagration portion of the combustion event is everything from when the charge is at maximum compression (TDC) all the way until the exhaust port is entirely open.


Yes. Exactly.

No "stopping point". It is a continuous motion with some of the exhaust gas being carried into the next intake phase (though not as much as back in the days when the intake and exhaust ports had overlap).


Yes. It is "crashing" the whole time, starting with how it gets piled up in the trailing part of the pocket

olddragger

iTrader: (3)

Mazda quote:" In the rotary engine, the intake chamber is separated from the combustion chamber. This minimizes the risk of abnormal combustion, and makes the rotary engine very suitable for burning hydrogen fuel. In addition, by implementing Mazda's direct injection technology, the hydrogen rotary engine achieves even better combustion."

Another: A rotary engine can be thought of–in some respects–as a large-bore, short stroke-piston engine. While the rotor does not reciprocate in a traditional sense, the relative motions of the rotor and housing effectively expand and contract the working chamber volume as if it were a piston in a cylinder. This is best illustrated by nulling out the rotor rotation and observing one working chamber as the housing rotates around it.

The definition of combustion is:

combustion
American Heritage Dictionary:
com·bus·tion

(kəm-bŭs'chən)
n.
The process of burning.
A chemical change, especially oxidation, accompanied by the production of heat and light.

Combustion does not hopefully occur when the face of the rotary in in the exhaust cycle, intake cycle and during most of the compression cycle.
It cannot by definition be a combustion chamber without combustion occurring with in it.

The chamber is composed of not only the rotary face but also the part of the housing that face is approaching and distancing itself from. That combination is the known as the "chamber". Thus the otto cycle:
intake chamber
compression chamber
combustion chamber
exhaust chamber.
They are all different.
The combustion chamber does not move its location within the engine. The combustion event can occur in whatever point of this combustion chamber that suites it the best. That can move.

I will repeat that we do have a moving cylinder head.

You are tutoring me? Well dang--i dont think I am getting my money's worth?
JK with you --nothing personnel here at all.

MazdaManiac

iTrader: (3)

So, now you are agreeing with me?

Ok. So now you are just making **** up.

Have fun. You are on your own.

Flashwing

Ok, yes you're correct that the motion is continuous though I guess I'm thinking in terms of very small time increments. The actual shape of the rotor's rotation, in essence, briefly stops rotating at TDC and then begins moving again. Granted the process is only a few milliseconds.

The way I visualized the charge behaving is being swept by the rotor and then as the rotation of the rotor slows due to the shape the charge continues in motion much like a person without a seat belt flies through a windshield when the car suddenly stops. I don't know what the velocity of the charge would be at that interval but I figured it would be enough to keep moving toward the exhaust port for a brief moment.

The argument here really is rather trivial. The fact of the matter is whether you consider the combustion chamber moving or the "cylinder head" moving the situation remains the same. You might as well argue that while sitting on a merry-go-round that you are not spinning but rather the rest of the world is spinning.

So where did we jump the tracks with this discussion? I thought we were talking about Octane.

MazdaManiac

iTrader: (3)

No, it never stops moving or changing shape. It isn't like a piston motor where the piston changes direction.
As the rotor crosses TDC, the tips are still moving - the leading away from the trochoid and the trailing toward the trochoid.
There is NEVER a moment where the combustion chamber isn't moving and changing volume.

olddragger

iTrader: (3)

we will just have to agree to disagree.

My definition of a chamber within an engine is the space between the piston/rotary face and it's relationship to whatever is around it--be it a cylinder head/ cylinder wall in the recip or flat plates and housings on the rotary. Each chamber/stage of the otto cycle is different-- recips and rotary. The chamber changes in these stages due to valves that need to open(recip), ports that open, shape of the rotary housing etc etc. The rotary face never changes shape, the piston head never changes shape, its the relationships that change.
It is important to realize that flow from and within a chamber is relative to the shape, size, and ports that are open or shut. Heat also influences that flow as well as the charge itself. There are other things also that influence flow but I dont want to go there now.
The rotary engine does not flow the same on intake as it does on exhaust, it does not flow the same on compression as it does combustion. Any one reading all this--ask yourself "why".
Some of it it very obvious. The intake versus the exhaust for example.
The combustion chamber flows too. It has a flame front that flows--hopefully in the correct manner-- from where the ignition oridginates. The flame front in the combustion chamber never flows exactly the same way twice. Its very close to exact, but it is not exactly the same.
The shape of the combustion chamber changes as the charge is combusing. It moves and this changes the relationships between the piston/rotary face and its surroundings.
The combustion stops and very shortly afterward the engine starts another cycle, the chamber changes--valves or ports open and then the engine completes that cycle. So on and so forth.
It is important to note that the combustion chamber design is what usually dictates the octane that is needed for proper running at the engines peak.
The renesis engine has a compression ratio of 10:1. Thats pretty high for a rotary. Now as the engine ages with miles etc and carbon is built up on the rotary face ( or in recips the piston top and cylinder head) the compression changes ever so slightly if the chamber is still well sealed. I would guess to estimate that the rotary could go up to 10.25/1 or even slightly higher as a result? This would have its most profound affect in the combustion chamber.
The 13-Bmsp combustion chamber design is well suited for the highest octane you can get.
It is actually better for E85 or hydrogen.

Rote8

But Jeff is on a roll, who cares what term Mazda uses for the combustion location(s) of the Mazda engine.



I still call the area where spark occurs "the combustion chamber"; yes the rotor rotates past the spark plugs and passes the exhaust ports, I call that part of the cycle, the exhaust cycle.

zoom44

thats not correct, todd.

The combustion shoves the rotor. the rotor moves towards the exhaust port because of the gearing. the expanded gases spill out the exhaust ports because that path is open.

when the next combustion event happens then the rotor takes over(because the other combustion event is pushing it) sweeping whats left in the chamber(whatever didn't have time to flee out the exhaust port) around for another ride

zoom44

let me see if i can make this clearer or muddy it up a bit.

Jeff, Denny is defining the discreet negative space where each event of the cycle takes place as the "chamber".

so the intake chamber is defined as the space from where the leading rotor edge first crosses/opens the port to the place it is when the trailing crosses and closes the port.

the compression chamber is the space defined from when trailing crosses/closes that intake port until the point in its rotation that the charge is completely compressed to its lowest volume.

The combustion chamber is the space defined from

A. the location of the trailing tip when the leading rotor tip crosses the trailing plug tip exposing the charge to spark from the plugs

to

B the location of the leading tip when the trailing rotor tip has crossed the leading plug so that the charge is no longer exposed to spark from said plugs.(or more precisely the moment when the charge is last exposed to spark, not the moment when it is no longer exposed)

The exhaust chamber is defined as the space from where the leading rotor tip passes and opens the exhaust port until where that leading tip is located when the trailing rotor tip passes/closes the exhaust port.


These spaces never change location. their limits are clearly defined although the compression and combustion areas overlap.

the rotation of the rotor during operation changes the shape and volume of these areas. the charge (except during its combustion phase) is swept through the changing volume and into the next defined space by the rotor movement.


Denny, Jeff is defining the chamber as the space between the leading rotor tip and the trailing rotor tip where the charge resides while it goes through all 4 phases of the cycle. This space is in constant motion and the volume of this strictly defined space constantly fluctuates as it rotates around during operation. The charge stays in this discreet space/chamber from the moment the intake phases begins until the moment the exhaust phase ends

MazdaManiac

iTrader: (3)

Jeff isn't "defining" anything.
The definition is ubiquitous, obvious and undisputed.
The definition is what it always was.
The definition is the standard and there is no one in this world that understands what this stuff is that defines each portion of the Otto cycle into different "chambers". This is just stupidity.

I will ask one more time for clarity:

In a piston motor, is each portion of the Otto cycle occurring in a different "chamber"?

Or, as is completely obvious to anyone that has ever had a discussion, read a book, taken a class or taken apart a motor, is there just a single chamber in which all four phase take place?

Kenichi Yamamoto uses the term "working chamber" interchangeably with combustion chamber in "Rotary Engine". If you prefer this term, go right ahead, understanding that "working chamber" is a theoretical term since all three combustion chambers are "working" all the time. "Working chamber" is just used to isolate one combustion chamber for discussion.
Felix Wankel (remember him?) uses the same terms in "Rotary Piston Machines". He invented it. Are you going to argue with him, too?

zoom44

in the context of the discussion you are side B. Side B is using that definition. that post was simply to clarify the position of each side. I wasn't arguing with anyone.

To the point:

The chamber is where the charge is. the charge is always moving because the chamber is always moving.

When we talk about the operation of the motor we are talking about it in terms of what happens to the charge. Working Chamber is used specifically to avoid this confusion about whether we are talking about WHERE in the housing combustion takes place or the place where the charge is located.

Denny you need to talk in terms of the Working Chamber- the volume between the leading rotor tip and trailing rotor tip where one intake charge resides during the four phases.

MazdaManiac

iTrader: (3)

A reasonable assertion.

In a rotary motor. Important distinction.
In a piston motor, the charge is just sorta "squishing". It isn't "moving".

Excellent.

Just an additional point of clarification:
"Combustion" is NOT "ignition".
I think what is additionally confusing OD is the idea that the two are the same.
As I indicated above, the "combustion" cycle in a rotary motor is pretty much everything from ignition until the closing of the exhaust port.

olddragger

iTrader: (3)

No Jeff in the recip engine the combustion chamber is not the same as the exhaust "chamber", the intake chamber etc. The opening of the valves changes the chamber--so it is not the same.
Ignition is what causes the combustion --please re read. Now whether or not the spark plug caused it is beside the point. I know you are aware that there are 4 different flame fronts in the rotary engine type combustion?
Are you saying that the rotary engine doesnt have squishing? You have lost me AGAIN.
The rotary does have this--not as much as some recips, but non the less it does have it

Zoom thanks for posting and the working chambers are different. One intake charge does go through the 4 cycles--absoulutely. But the combustion chamber does not carry this charge all the way through the otto cycle. You cannot exclude the housing from the different chambers. It is part of all the chambers. Without it there would not be any---period. You have to have a top/side and bottom. Each chamber has to have its own characteristics in order to do the job it is called on to do. So "working chambers" is a good way to think of it.
My oridginal post simply stated that the combustion chamber does not move its position within the engine. It has a dedicated spot. Of course there is a range of area it can use during its contraction and expansion. But once the combustion is completed then the chamber is no longer the combustion chamber. It turns into another working chamber.
Havent we posted enough on this?
Jeez.


I

MazdaManiac

iTrader: (3)

I guess so since you just keep talking past everyone without even really reading or comprehending anything.
I mean, WTF is this:
Do you even read what you write?

For me, it is just important for no one else to get confused or misled by your drivel. What you believe is of no real concern since you really aren't actively involved in advancing the arts, anyway.

I think enough information has been put up here to ensure that your "contribution" gets drowned-out and doesn't add to the noise level.

olddragger

iTrader: (3)

Jeff--- i am tired of being insulted by you.
Calling my thinking drival, what I believe is of no real concern, hopefully your way of thinking and posting has drowned out out my "contibution".
You have made it personnel and I cant be bothered by such a little man.
So I guess you have won--enjoy youre victory.

MazdaManiac

iTrader: (3)

Thanks.

Now read those books.

olddragger

iTrader: (3)

I re--read what you posted and thought about it for about 2 minutes--more than it was worth actually ---and Jeff you are right
I have not contributed anything concerning this car, of substance, to this forum Nothing that others didnt already know.
Moment of self discovery. Enough said.
OD out

zoom44

the opening of the valves does not change the position of the chamber, the valves mark the extent space of the chamber. anything before the intake valve(s) and after the exhaust valve(s) is not the chamber

of course he was not saying that. he was saying that the working chamber of the piston engine does not move laterally as it does in the rotary.

Rotary engines "squish" the same amount as piston engines of the same displacement and compression ratio. no less.

combustion chamber equals working chamber. the working chamber is defined as the space holding the charge we are discussing. period.

the working chamber is always the one being discussed. in a rotary we are discussing this "face" of the rotor. no matter how many faces it has. in a piston motor we are talking about THIS piston no matter how many other pistons there are.

in a piston engine thats the cylinder space between the top of the piston and the valves. the pistons movement within that space controls the shape and volume of the working chamber

in a rotary its the space from one rotor tip to the next and from the face of the rotor to the face of the housing. the face of the housing also controls the shape and volume of the working chamber as that working chamber moves around its arc. this working chamber not only changes shape and volume but also is always MOVING LATERALLY around its arc




on a side- a 4 cycle is really a five cycle. since compression is included when talking "4 cycle" expansion should be included as well

MazdaManiac

iTrader: (3)

Oh no, not you too?!?!? lol

There have been quite a few people that have argued that the Otto cycle is really a 5 cycle, or even SIX cycle activity (separating ignition from combustion).

This is folly equivalent to that which has been espoused in this thread for the last few days.

For the sake of the Otto cycle as it is uniformly described:

Expansion = exhaust
Ignition = combustion

Really, there aren't 4 distinct phases of the Otto cycle since each phase actually contains more than one action.
Even the intake phase is part of the EGR action.
Ignition can (and usually does) happen during compression. Therefore, so does combustion.
Combustion continues throughout the exhaust phase.
Etc.

The Miller cycle even has intake extending over the compression cycle.

The only cycle where active combustion isn't taking place is during the intake phase and really it is, just no direct power is being produced by it.

_____________________________________

As a side note, I can honestly tell you that it was quite surprising to see OD tilting at a windmill of this stature. He doesn't usually pick his battles well anyway, but pressing an argument like this one in the face of the facts presented in the actual literature provided by the inventors and engineers that brought us the engine in the first place is just stunning, let alone the absolute preponderance of information and facts presented in every single nook and cranny out there, including the very things he was quoting in attempt to support his ridiculous hypothesis.