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Flow and the Type of Flow...
Runner Length, Size, Configuration of the Runner restricts at various speeds.
Some work better than others.
Airflow behaves differently in a Carburation system than a Direct Fuel Injection system.
Carburated you have both Fuel and Air mixing, moving, twirling and tumbling which behaves different than just air alone.
Same issue when charging except that you can have the Manifold Backfire because the heat ignites the pressurized fuel.Hi Dan,
Yes, I understand this and how it applies to N/A engines. Thank you.
......But I'm still trying to find out about an application like the Allison and Merlin V12's.
I want to know why when the intakes have been pressurized with boost from the supercharger why would runner length, diameter, and to a certain extent shape for good flow matter.
Because it is a dynamic not a static system, the fuel air mixture is being pumped in continuously and leaving continuously with a pressure measured at a point in the manifold. Various twists and turns in the system could result in cylinders having different mixtures.Hi Dan,
Yes, I understand this and how it applies to N/A engines. Thank you.
......But I'm still trying to find out about an application like the Allison and Merlin V12's.
I want to know why when the intakes have been pressurised with boost from the supercharger why would runner length, diameter, and to a certain extent shape for good flow matter.
Thanks,
Any links or source information? .....I need to understand this better.
.
I posted a complete mathematical solution about one mouse-wheel-scroll above your post.... ?
Why do I post this stuff when nobody even reads it - its not like it was 25 pages back..... its all about
resonance which in pipes is explained below.
When the valve is closed its a pipe with one end closed....see if you can figure it out.... *HINT* when the wave motion is zero... pressure is high.....
Organ Pipe Resonance
A nice video... when the flames are higher its because the pressure in the tube is high, when engine speed matches the resonance..... one
can make the pressure behind the valve higher. Note that in this case its a "closed-closed" tube so the resonance nodes are not in the
same location as they would be in an engine, but the principle is clear.
NB - Its possible to confuse this with what is always talked about as a variety of badly named effects like "ram tuning", "inertia tuning"
and so on - which often include discussion about the pressure wave moving up and down the pipe.
However both things are happening at once, it is the little zones of high pressure moving up and down the pipe at resonance which
creates the "standing waves" (waves which dont change) in the first place. The standing waves are the measurable manifestation
of the pressure pulses moving up and down the tube - so its simply two different ways of looking at exactly the same thing.
Source for below:
Tubes
View attachment 555851
Can you explain weather? Why doesn't the air pressure equalise? What is this "sucking" how does it work? Does a normally aspirated engine at 20.000 ft become a supercharged one at sea level?And why would a convoluted manifold matter when every part of it contains air charge under pressure?
Can you explain weather? Why doesn't the air pressure equalise? What is this "sucking" how does it work? Does a normally aspirated engine at 20.000 ft become a supercharged one at sea level?
I was asking a simple question because you seem to be working under a misconception. An engine doesn't "suck" gas into the cylinders just as humans don't suck air into their lungs, it just seems that way. The system in a supercharged or turbocharged engine may be pressurised but it isn't static. On a 36litre engine one bank of a V12 operating at 3,000 rpm is drawing 9 litres of air every revolution, it is revolving at 50 revs per second so 450 litres/sec. If there is a sharp turn in the system the gas on the inside covers less distance than the outside of the bend causing turbulence and drag. The rail supplying the engine has 450L/s at the first valve and progressively less until the last cylinder has only the flow for one valve. If you take all the inlet valves out of a Merlin and replace them with a single valve from a car you will still have the same manifold pressure but much less power because the gas just cant get past the valve quickly enough.Can we keep it amiable?
All I have done is ask a question to which I am hopefully waiting for someone to explain (nicely) how this works.
I finished with the military twenty years ago and since than, maybe naively expect people to have some patience and understanding.
Is that asking too much?
You are talking about naturally aspirated engines,
You are talking about naturally aspirated engines, where the ''tuned length'' and resonance helps draw or suck in the next charge of air.
(You are not obliged to read my previous posts).
How does this apply to an intake manifold on an engine such as the Merlin/Allison specifically, where the whole intake after the supercharger is pressurised and as I understand it does not need this?
And why would a convoluted manifold matter when every part of it contains air charge under pressure?
Modern turbocompound F1 engines are running about 4bar manifold pressure, and all have resonance tuned inlet systems,
being hidden under carbon fibre inlets you wont find that out unless you work for a company who designs them - so this
fact is not know to all casual observers.
I would respectfully suggest you dont tell me what I`m trying to tell you, it will make it much easier for us to both communicate.
I did read all your previous posts, and am perfectly aware that you are interested in boosted engines.
(very) Briefly:
1) Most people with boosted engines dont bother with resonance effects because they are lazy, and would rather turn the boost up
than have a good intake system. It is certainly much more critical to get it right on an n.aspirated engine - but if you are after performance -
nearly all very high end highly boosted engines will have resonace tuning on the inlets. Packaging frequently prevents it however.
2) It is very rarely used on aero engines because at low engine speeds (3000rpm) to get a decent resonance you will need an intake
runner of over 1meter in length, which is usually prohibative for packaging, although the V-1710 makes an attempt at it.
3) Pressure does indeed NOT care about pipe bends and convolution, but MOVING air under pressure does. Every bend removes
energy from a moving fluid or gas, and reduces its pressure. To rectify a terrible intake system means running higher boost
pressures which has all sorts of very important knock-on consiquences which engine designers wish to avoid.
Modern turbocompound F1 engines are running about 4bar manifold pressure, and all have resonance tuned inlet systems,
being hidden under carbon fibre inlets you wont find that out unless you work for a company who designs them - so this
fact is not know to all casual observers.
I hope that helps explain.
Yep. All the major countries had good engines with the Germans and Americans having good rotaries and the British having a good inline. For me I voted for Britain because of the Merlin among others with the US and Germany very close behind.
Can someone change the England in the poll to Britain (or UK)...
Agree with this post.
Some of the U.K's best engineers and inventors came from Scotland.
I'm sure the Irish and Welsh won't be too quick offering you a beer either!
Stanley Hooker came to the states after the war and I believe everyone old enough knows Hooker Headers were the go to choice for performance back in the 50's-70's.
Hooker was a mathematician who specialised in the science of fluid mechanics/ dynamics which is what I alluded to earlier.Is that a fact? !
Yes, I remember these, but I didn't realise the connection.
Hi Dan,
Yes, I understand this and how it applies to N/A engines. Thank you.
......But I'm still trying to find out about an application like the Allison and Merlin V12's.
I want to know why when the intakes have been pressurised with boost from the supercharger why would runner length, diameter, and to a certain extent shape for good flow matter.
Is that a fact? !
Yes, I remember these, but I didn't realise the connection.[\quote]
Opps confused articles that I've read. I posted crap. So Sorry; although it was a Hooker, but it was Gary.