[Just thinking (OP)]

Quote from: Just thinking on Yesterday at 23:02:03

    In a normally aspirated engine is the air sucked in or pushed into the carburetor.

Anywhere except a physics classroom, the fuel an air are sucked through the carburettor.
In a physics classroom, the external air pressure pushes fuel and air into the carburettor.

I always considered it both as we cant have high pressure without low pressure so one works with the other to move air.

[alancalverd]

The essential component of a draught carburettor is its venturi - a narrowing of the throat. Air flowing through the throat speeds up in the restriction, so the local static pressure is lower than ambient and fuel is sucked into the flow.

We use the word "sucked" to distinguish it from a single-point injection carb, where a pump forces fuel into an unrestricted throat.

We also tend to use "suck" to distinguish ambient carbs from supercharged units where an auxiliary compressor (sometimes called a blower) raises the input air pressure above ambient.

[Just thinking (OP)]

The essential component of a draught carburettor is its venturi - a narrowing of the throat. Air flowing through the throat speeds up in the restriction, so the local static pressure is lower than ambient and fuel is sucked into the flow.

The purpose of the venturi is to increase the velocity of the air and fuel mix to the combustion chamber for better response.

[Bored chemist]

The essential component of a draught carburettor is its venturi - a narrowing of the throat. Air flowing through the throat speeds up in the restriction, so the local static pressure is lower than ambient and fuel is sucked into the flow.

We use the word "sucked" to distinguish it from a single-point injection carb, where a pump forces fuel into an unrestricted throat.

We also tend to use "suck" to distinguish ambient carbs from supercharged units where an auxiliary compressor (sometimes called a blower) raises the input air pressure above ambient.

And in all three uses, if you used the word in a physics class, you would be berated for it.

The purpose of the venturi is to increase the velocity of the air and fuel mix to the combustion chamber for better response.

No, it's so the Bernoulli effect drops the pressure. so that the external pressure can push fuel into the mixture.

[Just thinking (OP)]

No, it's so the Bernoulli effect drops the pressure. so that the external pressure can push fuel into the mixture.

Not really as the carburetors throttle butterfly is at the upper side of the venturi and the fuel jet and the butterfly is more restrictive than the venturi so the venturi only comes into effect during full throttle to assist with the high demand of high RPM.

[Petrochemicals]

something to do with vacuum creation.

But that would create lift from the upper surface, which you and BC do not believe in.
Fortunately, modern cars don't use carburettors, which rely on the same (Bernouilli) principle as the upper surface of a wing. Just as well because you tell me that the laws of physics have changed and Bernouilli no longer applies. I must get rid of the carb on  the old Cessna - it's hard enough to fly with only half the wing generating lift, and if the carb doesn't suck petrol, we are doomed.

I think you are confusing me with someone else. How much upward lift do you think a wing creates, given that all around it is air? Secondly why does air need to travel faster over a wing anyway, it is because they are quantum entangled? If you take the low road and I take the high road, you may be in Scotland before me, only if you left at the same time or later, there are people who took the high road and are already by lock lomond before you even left. The high road has more people on it because it is longer, but traffic pressure is the same on both roads. However as the high road has a steep decent the traffic pressure on it is less as the gradient causes the traffic to  rush. In fact the gradient is very steep and if you fall you may tumble and bump other traffic, then the low road traffic may have to come up to the high road descent to ensure that all is OK, but this creates terrible congestion on the low road descent.

[alancalverd]

It is always interesting to listen to experts who know more about something than the people who design, teach and do it. Maybe they would like to explain why a bumble bee can't fly.

And in all three uses, if you used the word in a physics class, you would be berated for it.

Have you ever drunk anything through a straw? Or maybe sat in the cockpit of an aeroplane and wondered what that instrument labelled "suction" actually measures? How does your diaphragm work?
Nobody gets berated for telling the obvious truth in my classes.

[alancalverd]

the carburetors throttle butterfly is at the upper side of the venturi

Before the next lecture, I recommend you study the diagram of a carburetor and pay attention to the direction of the airflow arrows. Remember most flat-four aircraft engines use an updraft carb. that To avoid meeting the Grim Reaper (or worse, failing Airframes and Engines Part 1), be careful not to confuse the choke valve with the throttle butterfly.

[alancalverd]

How much upward lift do you think a wing creates, given that all around it is air?

Cessna 172, just over a tonne in level flight. Blanik, about half that (either way up). AN225, 640 tonnes. There being nothing else around but moving air, and since neither aircraft stays aloft if it's not moving, one must assume that it's something to do with the motion of air.
Admittedly Aristotle thought otherwise, but as his log book does not record any actual flights I do not consider him an authority on aerodynamics. 

[Just thinking (OP)]

Before the next lecture, I recommend you study the diagram of a carburetor and pay attention to the direction of the airflow arrows. Remember most flat-four aircraft engines use an updraft carb. that To avoid meeting the Grim Reaper, be careful not to confuse the choke valve with the throttle butterfly.

Simple steps for carburetor operation Step 1. at idle the manifold pressure is very low as the throttle butterfly is closed to idle at this point the idle fuel jet is in operation below the throttle butterfly step 2. Don't forget the choke if it is cold it will open the throttle a little to raise the idle speed and chock the carburetor chamber raising the pressure pulling in moor fuel. Step 3. Don't forget to turn the choke off after a short time or you will be low on power waste fuel and foul the plugs. Step 4. give it full throttle the manifold pressure will drop but the venture in the carburetor will maintain the pressure to drag/suck the fuel in via the main jet. See it wasn't so hard. OK we will have our morning tea brack now after the brack we will discuss shut down procedures. Don't forget Tuesday parachute instructions you may need them I will remind you again at the end of today's lessons.

[Bored chemist]

It is always interesting to listen to experts who know more about something than the people who design, teach and do it. Maybe they would like to explain why a bumble bee can't fly.

And in all three uses, if you used the word in a physics class, you would be berated for it.

Have you ever drunk anything through a straw? Or maybe sat in the cockpit of an aeroplane and wondered what that instrument labelled "suction" actually measures? How does your diaphragm work?
Nobody gets berated for telling the obvious truth in my classes.

And the point made by physics teachers remains valid.
A vacuum isn't anything, so it can't do anything.
In particular, it can't suck.

The atmospheric pressure pushed the drink up the straw.

In addition to the other problems you would face, you couldn't suck a drink through a straw if you were in a vacuum.

[alancalverd]

In addition to the other problems you would face, you couldn't suck a drink through a straw if you were in a vacuum.

There's a subtle clue in the word "airplane".

[Bored chemist]

In addition to the other problems you would face, you couldn't suck a drink through a straw if you were in a vacuum.

There's a subtle clue in the word "airplane".

Do you plan to explicitly list all the things I just abbreviated to

In addition to the other problems you would face,

or should we just take them as read?

[alancalverd]

Consider the induction stroke of a piston engine. What is the piston doing to the air-fuel mixture?

[Just thinking (OP)]

Did you know that if the atmospheric pressure was to raise an additional 35 PSI the tyers on your Reliant Robin will be flat.

[Bored chemist]

What is the piston doing to the air-fuel mixture?

Getting out of the way.

[Just thinking (OP)]

One could compare a gun firing the bullet is pushed out by high pressure not so much sucked out by low pressure.

[Bored chemist]

One could compare a gun firing the bullet is pushed out by high pressure not so much sucked out by low pressure.

Do you know what "the induction stroke" means?

[Just thinking (OP)]

Do you know what "the induction stroke" means?

Yes, it is the intake stroke just before the compression stroke then the firing stroke, and last the exhaust stroke. providing that we are referring to a four stroke engine.

[Petrochemicals]

Does an aeroplane engine push or pull, if it pushes it would need to compress the air, yet if it pulls the outflow is inconcequential. A propellor, relies on pushing. The gaseous nature  of air means it is far more likely to fill the void in a non directional manner than being ejected in a non directional manner, especially if the power unit is travelling forward.