BUBBLES

The nozzle used on most pumps has a cutoff feature when the level reaches the nozzle. It has a detector which is loose in the small section of the nozzle dia.
When fuel passes over/past it it can draw a small amount of air into that section and that areates the fuel to some degree.
Fuel hitting corners and baffle plates or restrictions also areates the fuel as does dropping into the tank. As you fill the tank the return/exiting air comes out of the large breather into the neck where the fuel is pumped in. That air, if it combines with the intake fuel flow, to some degree, but does so far more if the fuel is actually allowed to hit the air exit port into the neck. That will definitely aerate the fuel as it fires directly into the fuel stream

So if the fuel is turbulated, and hits the exit air port + the amount the nozzle creates you will end up with a large amount of froth. Not allowing time for the fuel froth to subside means it becomes a problem for those in a hurry with little patience.

In a highflow truck tank the area in the tank is larger so more opportunity for the froth to dissipate before it gets to the neck. They also have far less intake turbulation happening.

If filled quickly our vehicles require a slowdown of rate near the end to allow the froth to dissipate. Very slow after the first shutoff and there is no problem. Don't wear dark glasses when filling if you want to see the increasing level in the tank, other wise you see it on your pants when full.

I'm wondering if we pay for the space the bubbles take up when each litre passes through the pump? 0.9 litres of diesel, 0.1 litres of bubble (or worse) for each litre.

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G'Day Muz,

The bubbles you are observing are probably from the action of the cut-off valve within the filler nozzle.

There is a venturi within the nozzle arranged so that the flow of fuel creates a partial vacuum that draws air in via a small tube whose open end is positioned at the nozzle discharge opening. When the end of this tube is occluded by the rising fuel the pressure within the tube decreases and operates the cut-off valve.

The bubbles you see are the result of the air induced by the venturi being mixed into the fuel. It has no effect on the measured volume as the air is introduced after the metering.

Muzbry,,, Stop topping it up with lemonade!!....LOL



Cheers Axle.

Here you go Muzbury, this should do your head in.

Bubbles link

Good morning
Thanks fellas, thats exactly what i was thinking. It just doesn't matter.

Muz,

There is a direct correlation between foaming of diesel and the following:

The number of other vehicles waiting to use the one & only diesel pump;

The Impatience Factor of drivers of said vehicles;

The state of your clothes ie: are you going to a wedding/christening, or just slipping up to the yard to do a service on a D9?

Are there any disposable gloves left at said bowser;

Where are you planning to travel? If it's the Simpson/CSR, then you'll want the diesel lapping the flange at the filler spout, which might be difficult if you refer to points 1 & 2.

No doubt there's many other difficulties when the diesel is foaming?

Bob

I can remember fuelling up our caterpillar D2 tractor tank when I was only 14yrs old with a hand drum pump and the diesel had air bubbles in it in those days nothing has changed still the same today doesn't matter whether you pour it or pump it always has air bubbles

The diesel pump was invented by the same bloke who invented the beer tap.

Watch this......

https://www.youtube.com/watch?v=x4LCbGsujdU&t=203s

This is the type of pump and filtration system I use on my Silverado.

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I think that there may be some confusion here between "bubbles" and "froth". And Muzbry did ask about bubbles.