Finally, a (working) see-through carburettor.

[Garfly]

So that's what happens!

 

 

[Hank1959]

Great find!

Seemed a little casual about what would happen if it backfired.

[APenNameAndThatA]

So, the throttle is the throttle and the mixture is the choke. Obvious to me NOW... Thank you so much for posting. 

[skippydiesel]

3 hours ago, APenNameAndThatA said:

So, the throttle is the throttle and the mixture is the choke. Obvious to me NOW... Thank you so much for posting. 

This is a very primitive carburettor -

 

On a well designed/calibrated system the chokes, is an aid to starting (in a petrol) engine. Its function is to create a rich fuel to air mixture. Once the engine has started and importantly running (many engines will require partial choke to keep running until warm enough to maintain the cycle) the choke is opened fully and has no further role in the fuel/air delivery system.

 

The throttle is  used to meter the delivery of the fuel/air mixture, thereby controlling the speed of the engine. Without the throttle, the engine speed (rpm) will continue to rise, until the limit of the carburettor to deliver fuel/air is reached or the engine self destructs (This is called a "runaway engine").

Edited July 1, 2021 by skippydiesel

[Thruster88]

With a transparent rotax 912 induction manifold and high speed camera it would be interesting to see if fuel droplets are failing to take the bend into the rear cylinder at cruise and max power, we know from looking at the plugs that the front is richer after some ground running.  

[skippydiesel]

26 minutes ago, Thruster88 said:

With a transparent rotax 912 induction manifold and high speed camera it would be interesting to see if fuel droplets are failing to take the bend into the rear cylinder at cruise and max power, we know from looking at the plugs that the front is richer after some ground running.  

Hmm! - there are "droplets" in the above video, however the much more sophisticated Rotax system, the fuel should pretty well be vaporised (mixed with the air), from the point of entry to the "barrel" of the carburettor. I would speculate that the darker plugs on the front, would have more to do with cylinder head temperature, than significant variation in fuel/air mixture between from & rear cylinders.

[kasper]

8 hours ago, APenNameAndThatA said:

So, the throttle is the throttle and the mixture is the choke. Obvious to me NOW... Thank you so much for posting. 

Ish

 

the throttle butterfly is the throttle because it is downstream of the Venturi and is restricting the amount of mixture admitted to the cylinders but not changing the mixture itself. 
 

A choke is a form of mixture control because it it upstream of the Venturi and regardless of throttle position it changes the air/fuel mix. 

in an aircraft engine the mixture control is actually adjusting the opening in the Venturi that is admitting the fuel. 
 

to put it against a common two stroke carbi - the Bing 54 from your rotax 503 and 582

1. The throttle is not a butterfly valve but the sliding barrel.  And the throttle barrel has a tapered needle moving within the main jet off the bottom of the slide.  Has the advantage of giving a more even mix change and volume change with throttle movement …. Two strokes are more sensitive to mix changes and have the ability to eat pistons with ease.

 

2. there is no choke butterfly and instead there is a secondary fuel transfer route that has a simple on/off stopper lifted by the choke cable.

 

nice video and great photography 

[Old Koreelah]

A Constant Velocity carb is even more interesting because (as I understand it) the slide is pushed up by the pressure of incoming air and falls down again under its own weight, or is pushed down by a spring; the slide pulls the tapered needle up and down in the main jet, automatically adjusting the mixture to the varying velocity of incoming air (hence the name).

The slide would therefore pulse up and down at half the speed as the piston (assuming one carb per cylinder). It’s amazing that CV carbs with a rubber diaphragm don’t need a new one every week.

[pluessy]

3 hours ago, Old Koreelah said:

A Constant Velocity carb is even more interesting because (as I understand it) the slide is pushed up by the pressure of incoming air and falls down again under its own weight, or is pushed down by a spring; the slide pulls the tapered needle up and down in the main jet, automatically adjusting the mixture to the varying velocity of incoming air (hence the name).

The slide would therefore pulse up and down at half the speed as the piston (assuming one carb per cylinder). It’s amazing that CV carbs with a rubber diaphragm don’t need a new one every week.

The piston & diaphragm don't move unless the throttle has moved or the engine rpm changed. The piston has a very close fit with the guide tube and that captured volume acts as a damper. The passage of the vacuum port to lift the piston is also very small to reduce or just about eliminate the pressure fluctuations and piston movements.

SU and Stromberg CV carbys have an oil-filled guide tube acting as a damper, mainly to reduce the movement when opening the throttle (lack of oil is noticeable by a flat spot when quickly opeing the throttle).

[kgwilson]

The Bing type 94/40 as used in Jab engines is a constant depression pressure compensating carb so considerably more complex than a simple venturi. The choke is also totally different as it has a separate fuel delivery system with it's own jet delivering  more fuel and relies on the throttle butterfly valve being closed to work properly as it does not have one itself. This is why you must keep the throttle closed when starting a cold Jab engine.

[walrus]

Gadfly, thank you for posting the carburettor video. The high speed photography is fantastic and it is really educational. 

 

‘While carbs can be more sophisticated, as people pointed out, the basic principles remain the same and illustrate the limits of the efficiency of carbureted engines.

[spacesailor]

SO

Fuel injection does Not require the venturi, as the fuel is delivered to the engine by pressure !??

Super  ( turbo  ) charging does away with the vacumme altogether. ( suction stroke  )

Both make the engine more efficient.

If only mr Benz  had known. LoL

spacesailor

[skippydiesel]

1 hour ago, spacesailor said:

SO

Fuel injection does Not require the venturi, as the fuel is delivered to the engine by pressure !??

Super  ( turbo  ) charging does away with the vacumme altogether. ( suction stroke  )

Both make the engine more efficient.

If only mr Benz  had known. LoL

spacesailor

Not so fast;

 

Fuel injection completely eliminates carburettor function. As the name suggests fuel  is  "injected" under pressure, either into the inlet manifold or into the combustion chamber. Can be one of three types 1. Single injector replacing carburettor. 2 One injector per cylinder, located very close to inlet valve 3 One injector per cylinder, injecting directly into combustion chamber. The injector nozzle (tip) is designed to deliver an aerosol (fine droplets) into either the inlet air stream or combustion chamber - so you are correct , venturi no longer required.

 

Turbo charging pressure (boosting of incoming air) can be used with a carburettor or with fuel injection. It is not actually part of the fuel delivery system - it is a way of increasing air/oxygen to the combustion process, so that more fuel can be burnt, generating more power for a given cylinder volume.

 

"mr Benz" ? Pleas expand 

 

 

Edited July 1, 2021 by skippydiesel

[spacesailor]

Foremost Automobile maker in Europe !.

DaimlerBenz - MercedesBenz,- now A.M.G.Benz.

Still in production, Since, Karl Benz  ' 1879 ' developed ( patented  ) a two stroke engine !.

Longer than vw.

spacesailor

Edited July 1, 2021 by spacesailor
Missed word

[kasper]

Mr Benz ... Planey is showing his age and interests.

 

For example The WWII Benz engines in the bf109/me109 were fuel injected and that was a functional advantage compared to the merlin carburetted engines in the spitfire and hurricane ... until the orifice was added to the carburetor on the Merlins  ... google merlin and orifice if you dare 😉

 

 Fuel injected engines are generally not impacted by neg G  .... a carbi with a fuel float bowl will be  ... the fuel pick up comes from the bottom of the bowl and in neg g that bottom is full of air so not good for engine running

Edited July 1, 2021 by kasper

[spacesailor]

I just presumed Everyone would know Karl Benz.

I think he should be more famous than Ford.

BUT

Those Americans have better advertising of anything American,!.  Lo

spacesailor

[Garfly]

Everyone knows Benz.

[Old Koreelah]

59 minutes ago, kasper said:

Mr Benz ... Planey is showing his age and interests.

 

For example The WWII Benz engines in the bf109/me109 were fuel injected and that was a functional advantage compared to the merlin carburetted engines in the spitfire and hurricane ... until the orifice was added to the carburetor on the Merlins  ...

A female engineer fixed this problem, helping to win the Battle of Britain.

https://www.kenleyrevival.org/content/history/women-at-war/beatrice-shilling-revolutionising-spitfire

[skippydiesel]

"If only mr Benz  had known. LoL"

 

Benz yes - but still dont know why you mention him in this context

[spacesailor]

He needed a ' good ' carburetor. 

Even many years later aircraft used ignition  to slow their engines for landing.

spacesailor

[skippydiesel]

5 hours ago, spacesailor said:

 

Even many years later aircraft used ignition  to slow their engines for landing.

spacesailor

Intriguing! - more please.

[F10]

Yes, a lady engineer solved Merlin -ve “g” fuel starvation problem, short term. A plate in the float bowl, with a small hole in it held enough fuel near the jet diffuser, with short term negative g, to prevent a cut, but hole was big enough to not impede normal ops fuel delivery, simple but clever! Later carbs were floatless, or had a type of injection system to deliver fuel to the jets I think.

The Bings on my Rotax, have a throttle butterfly, ahead of the moving piston and tapered needle. With choke on, throttle fully closed, the butterfly is fully closed. This exposes very small drilling’s only just past the butterfly plate, which are part of the choke circuit, because downstream of the fully closed butterfly plate, a suction exists (manifold pressure being lower than ambient, especially at idle) over these drilling’s, which suck up fuel, to enrich the mixture for start. If you crack the throttle slightly, the butterfly plate actually covers these holes, or moves past them, putting them in a pre butterfly plate high pressure area, so fuel is not sucked up, engine struggles to start.
Normal running. As I understand it, the throttle butterfly valve causes more air to come into the Venturi throat, this sucks up the piston, withdrawing the tapered needle from the jet orifice, leading to more fuel and air going into the induction manifold. The bottom of the piston forms the Venturi, creating a suction, constantly drawing fuel up past the needle taper, for higher power running. The Bings are cool carries, simple really yet reliable. I like the fact the Rotax config, gets the carb bodies nicely warmed up being so far back on the engine. That is why they rarely suffer carb icing. They are a lot like the old SU carbs on Brit sports cars. Wow, I did ramble on!

[kgwilson]

Same as the Bing 94/40 carb on the Jabiru but it is at the rear under the engine & gets warmed from air passing the exhaust pipes. Carb icing is rare. I've never had it.

[pluessy]

On 02/07/2021 at 9:09 PM, skippydiesel said:

Intriguing! - more please.

It was mainly on the rotary engines (Gnome Monosoupape), they had no variable throttle valve, only minimal control on the valves and cutting the ignition either all or some cylinders. This resulted in the typical engine noise of engine off - engine on when coming in to land (same while starting up/idling/taxiing).

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

 

[spacesailor]

The torque of the spitfire can cause the plane to flip, tearing the winge off, ' so l heard ' .

 spacesailor