Brad:

Another select morsel from Wikipedia with the mad hope that you will get it and the insane hope that you will simply admit that you get it.

Note that they discuss the two meanings for resonance.  Have a good brain fry over that.

https://en.wikipedia.org/wiki/RLC_circuit

Natural frequency

The resonance frequency is defined in terms of the impedance presented to a driving source. It is still possible for the circuit to carry on oscillating (for a time) after the driving source has been removed or it is subjected to a step in voltage (including a step down to zero). This is similar to the way that a tuning fork will carry on ringing after it has been struck, and the effect is often called ringing. This effect is the peak natural resonance frequency of the circuit and in general is not exactly the same as the driven resonance frequency, although the two will usually be quite close to each other. Various terms are used by different authors to distinguish the two, but resonance frequency unqualified usually means the driven resonance frequency. The driven frequency may be called the undamped resonance frequency or undamped natural frequency and the peak frequency may be called the damped resonance frequency or the damped natural frequency. The reason for this terminology is that the driven resonance frequency in a series or parallel resonant circuit has the value[1]

        ω  = 1 / Sqrt(L*C)

This is exactly the same as the resonance frequency of an LC circuit, that is, one with no resistor present. The resonant frequency for an RLC circuit is the same as a circuit in which there is no damping, hence undamped resonance frequency. The peak resonance frequency, on the other hand, depends on the value of the resistor and is described as the damped resonant frequency. A highly damped circuit will fail to resonate at all when not driven. A circuit with a value of resistor that causes it to be just on the edge of ringing is called critically damped. Either side of critically damped are described as underdamped (ringing happens) and overdamped (ringing is suppressed).

No spaghetti here.

What's more interesting than the philosophical issue whether a resonance can exist without an unbalance of energy in the resonating/resonant system, is why the Mythbusters could not break the wine glass with a single tone, but could do it with two tones?

Brad:

Another select morsel from Wikipedia with the mad hope that you will get it and the insane hope that you will simply admit that you get it.

Note that they discuss the two meanings for resonance.  Have a good brain fry over that.

https://en.wikipedia.org/wiki/RLC_circuit

Natural frequency

The resonance frequency is defined in terms of the impedance presented to a driving source. It is still possible for the circuit to carry on oscillating (for a time) after the driving source has been removed or it is subjected to a step in voltage (including a step down to zero). This is similar to the way that a tuning fork will carry on ringing after it has been struck, and the effect is often called ringing. This effect is the peak natural resonance frequency of the circuit and in general is not exactly the same as the driven resonance frequency, although the two will usually be quite close to each other. Various terms are used by different authors to distinguish the two, but resonance frequency unqualified usually means the driven resonance frequency. The driven frequency may be called the undamped resonance frequency or undamped natural frequency and the peak frequency may be called the damped resonance frequency or the damped natural frequency. The reason for this terminology is that the driven resonance frequency in a series or parallel resonant circuit has the value[1]

        ω  = 1 / Sqrt(L*C)

This is exactly the same as the resonance frequency of an LC circuit, that is, one with no resistor present. The resonant frequency for an RLC circuit is the same as a circuit in which there is no damping, hence undamped resonance frequency. The peak resonance frequency, on the other hand, depends on the value of the resistor and is described as the damped resonant frequency. A highly damped circuit will fail to resonate at all when not driven. A circuit with a value of resistor that causes it to be just on the edge of ringing is called critically damped. Either side of critically damped are described as underdamped (ringing happens) and overdamped (ringing is suppressed).

No spaghetti here.

Well thats fantastic MH,you posted a post on damped and undamped resonant/Natural frequencies.
Please point out where it says anything about when such systems are resonating,or when they are just oscillating at there resonant frequency.

I see this-->The resonance frequency is defined in terms of the impedance presented to a driving source.
Other than that,your post means didly squat about resonating.
nice try,but not good enough,as you are going over ground that we already know.

Yes--there is still spaghetti MH,and lots of it.


Brad

Brad:



But the saddest thing of all, is that you simply couldn't admit that the way the exhaust system works to optimize the performance of the engine is a timing-based function and not a resonance-based function.  It is absolutely clear to me that this is the case and I am quite certain that the majority of readers would agree.  Instead of just admitting to it like a man, you shrink away from it and try to hide behind fake lol's and smiley faces.  And I have seen countless examples of this before and I think that is sad.

MileHigh

You clearly make no attempt to seriously respond to the technical argument that I made that clearly shows that there is no resonance at all in operation on the exhaust side as shown in the link provided by AC.

Instead, you do a chicken dance and try throwing spaghetti against the wall and hoping some of it will stick.  It's just a lousy performance and I will deal with it in another posting.

MH,as i said--you have no idea as to what resonance is,and this is your downfall.
Im not going to argue with a clown that has limited knowledge on the ICE--as we seen on the JT thread.
I mean,look at the palava comment below

Quote-optimize the performance of the engine is a timing-based function and not a resonance-based function.
This comment just shows how out of touch you are,as all states of resonance are timing based functions. The fact that you dont-or cant put it altogether,is no fault of mine.
Just as an LC circuit will only resonate at the correct frequency,so it is with the expansion chamber and combustion cycle. The frequency(rpm) has to match the frequency of the expansion chamber before maximum amplitude is gained--this is a resonant circuit.

I have tried to explain it to you before,but as you do when you need to be right--you just pay no attention to what is told to you,and you keep on babbling away like you are doing now.
There is a reason they call it a resonator MH--because it resonates at the correct engine RPM(frequency). At this very point,the maximum HP amplitude is reached.
It is no different to an LC circuit,where the gas charge is cycled back and forth between the cylinder and expansion chamber,until at the correct RPM(frequency)a maximum amplitude is reached. The very same happens in an LC circuit,where the power is cycled back and forth between the capacitor and inductor,and at the right frequency,maximum amplitude is reached---the resonant frequency.
Both are driven circuit's,and both are resonant circuits.

Take another look at the animation on the link AC provided,and have a good hard look at the gas flow to that of the pistons position. At resonance(the correct rpm),the piston will be at the correct position in relation to the exhaust port,so as it matches the exact time that the returning pressure wave of gas can enter the exhaust port. Either side of this frequency(RPM),and this timing is out ,where the piston will either be covering most of the exhaust port,or it will not be close enough to it,and so the gas will enter the exhaust port,build cylinder pressure,and then start to flow back out of the exhaust port before the piston can close it off.

As i have said--over and over--if you wish to discuss (or argue as you do most ofter) ICEs with me,then go and learn up a bit first.


Brad

Brad:

I know it looks like a duck and walks like a duck and squawks like a duck.  But in this case it's not a duck.

On the inlet side, it's based around a Helmholtz resonator, and that's definitely an example of resonance in action to make an ICE run more efficiently.

On the exhaust outlet side, it's using an exhaust pipe as a timing device, a delay line, to make the ICE run more efficiently.

I will say to you what you often say to me:  Find some references that state that resonance is used in the exhaust system to make an ICE run more efficiently.  AC's link clearly does not state that there is any resonance at play on the exhaust outlet side.  I would be more than happy to read them and if I am wrong I will state that right away.  (Note that mufflers don't count here because they do not improve the efficiency of the engine in the context of our discussion.)

MileHigh

-------------------------------

On another more serious note.  Sorry to my American friends and I know how it feels.

Even in our sleep, pain which cannot forget
falls drop by drop upon the heart,
until, in our own despair,
against our will,
comes wisdom
through the awful grace of God.

- Aeschylus

Loner
Funny I was thinking about you today [the race track]
good to read you here and your valuable contributions.

I know few here have your experience with an ICE and Racing .
  I have to just drop this in from another racer/engine designer  "Johan 1955" for you to see , a very dependable 2 stroke
 8HP per cubic inch N.A. and climbing ...as they continue to dial it in.

https://www.youtube.com/watch?v=1zDmlOYiaTI

Yes its a screamer [perhaps the NA[normally aspirated] goes out the window ??] ,But they also play with resonance and a huge standing wave in some very tricky ways.

BTW your comments here are in no way off topic !
regardless whichever side of the fence your on.



respectfully
Chet K

Rats...

Tinman, I am sorry to have to respond to that, but I'm afraid I must "sorta" agree with MH on that specific point.

I want to ensure you understand what I mean, so I am posting this, even though I stated I would not comment.  This is really a matter of semantics.  Removing electrical resonance for a moment, though the data would apply in another way, the simplest way to describe physical/mechanical resonance would be an oscillation between potential and kinetic energy.  This IS what is happening inside the exhaust, and is what is providing the described pressure wavefront, however the alignment of the piston at the correct point on the exhaust's pressure wave would (In my opinion...) have to be considered "Timing" and not part of the actual exhaust resonance.  Yes, I am picking nits here, but that was the major point I was trying to make previously.

To put it another way.  Pick an RPM.  To make the best power at that RPM, you want to have the exhaust resonate at a specific frequency.  To get this effect, you ONLY have to modify the exhaust, as the action of the piston will not change.  (I'm not explaining this well, so please forgive me.  I'm trying...)  While the amount of power will change, due to increase charge density, the actual frequency (RPM) of the piston does not change.  The piston is acting as the signal injector, at a "Fixed" frequency and when the resonance of the exhaust matches, then...

This is where I always had so much trouble, as increasing the power in other ways could change the charge density enough to alter the exhaust freq. while the engine is still spinning the same RPM.  All of a sudden my tuning to increase power caused a decrease.  I do realize that 2 stroke is MUCH more sensitive to these effects than 4 stroke where the situation is different.  Therefore, while I would agree 100% that the exhaust has a physical resonance going on inside (Both acoustic and pressure...), the true physical resonance is ONLY going on in the exhaust.  The fact that this wavefront is matched to the correct position of the piston is not really part of the exhaust resonance, even though it IS dependent on it.  I'm quite certain you are aware of Q and bandwidth, although you might view it as the width of the power band instead.  Same thing to me.  So, while these are very synchronized, and very timing dependent, in the true sense of the concept the exhaust and engine are not in resonance with each other, they are just correctly timed for the desired effect.  The exhaust IS in resonance by itself and so is the engine.  (I doubt we need to discuss crankcase volume, etc., as that is another whole story.)

All it really comes down to is how nit-picky we all want to be.  There are those in the engine area that will lean more towards your view and discuss intake reed valve tensions as being part of the engine resonance and on and on and on, but I have always maintained that while they are timed and synchronized, the actual resonance applies separately to intake, engine and exhaust.  In real life I can accept that, while at the track, while you won't be doing engine mods, you will be re-jetting and swapping resonance chambers depending on conditions.  This makes it easier to look at the whole thing as a single resonant system, but I look at it as more complex than that and try to keep them separate in my mind.  End result?  While bolting on a different chamber between heats, it's a single resonant system.  While sitting on the couch or at the computer, it is three separate systems.  As to which is correct?  Ask the person sitting on the couch and he IS correct.  Ask the person who just won the race, HE is correct.  For me, both are correct for what they are trying to do.  There will always be differences in perception between the academics and application people in complex systems.

I am definitely too old for this stuff.

You are basically saying what i am.
The expansion chamber is the resonant source,but for that resonant source to have the desired effect,then the pistons position must also align to that resonant frequency of the expansion chamber. If the RPM of the engine is not correct,then the resonant chamber dose not have the desired efffect-->engine frequency must be the same as the resonant frequency of the expansion chamber.
This makes a resonant system as a whole,and for maximum pressure amplitude to be reached inside the cylinder,then this system as a whole must exist.

Hope that helps


Brad

You are basically saying what i am.
The expansion chamber is the resonant source,but for that resonant source to have the desired effect,then the pistons position must also align to that resonant frequency of the expansion chamber. If the RPM of the engine is not correct,then the resonant chamber dose not have the desired efffect-->engine frequency must be the same as the resonant frequency of the expansion chamber.
This makes a resonant system as a whole,and for maximum pressure amplitude to be reached inside the cylinder,then this system as a whole must exist.

Hope that helps

Brad

You are talking crap again to avoid the frying pan.