Flow Measurement of Diesel Fuel 1

[Mechwill]

Hi all,

Please let me briefly explain the scenario of this experiment

Types of fluids: Air and Diesel
Types of measurement: flow rate and pressure

Air pressure : regulated in 10 to 15 psi

Both of air and diesel fuel are working in 1/4" ID pipe/hose.

A spray nozzle is placed into a manifold so that the fuel can be drawn by the air. This will create atomization and mixture with air and diesel. Air is the driving energy to draw the diesel fuel into the system. In other word, there is only vacuum pressure in the fuel line.

Can anyone advise on best way to accurately measure the volume flow rate of air and fuel from the situation above? All the information and suggestion are much appreciated.

Regards

 

[racookpe1978]

To start: Measure the vol of fuel moved per time from the source liquid fuel tank?

 

[Mechwill]

Yes, it's the volume flow rate that I am looking for. The liquid fuel tank will be placed 2 feet below the spray nozzle.

 

[MikeHalloran]

I don't think you're going to induce a suction lift of 2 ft of Diesel with 10-ish psi of air in a ~.25" lumen.

Read up on ejectors.


Separately, the most accurate inexpensive way to measure the fuel flow is as racookpe1978 suggested; measure the tank level, then measure it again after a measured time has elapsed, and do the math.


Separately from any of that, what are you going to do with Diesel vapor in air?
You can't run an SI engine on it, at least not for long.



Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

Sorry if I misunderstand your post, but if the pressure in the air flow at the mixing nozzle is 10-15 psi higher than that in the diesel circuit, then there will not be flow of diesel into the air circuit. To produce a flow of diesel fuel thru the nozzle orifice, there must be enough dynamic pressure drop in the airflow existing at the nozzle to push liquid diesel up 2ft of 1/4" tube with atmospheric pressure in the diesel fuel tank.

 

[LittleInch]

This really needs a diagram to explain what you're trying to do as it doesn't make sense at the moment. However I agree with the posts above, measuring single phase fluids is much easier than two phase or dense vapour.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Mechwill]

I apologize for not making this topic clear. Allow me to give some background. The purpose of this experiment is to measure and analyze the flow rate an oil burner spray nozzle called Siphon Air Atomizing Nozzles. The setup for this experiment is shown in this figure

The calculation of flow rate can be done. However, there are many losses in the fuel delivery system.

So far, the way we measure the flow rate of diesel fuel is to use stopwatch and graduated cylinder with valve. This step-up gives pretty good indication of the flow rate but not precise enough. See Figure below

 

[LittleInch]

try attaching the figures using the upload to engineering.com. your attachments turn up as a box with a cross in it for me.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[racookpe1978]

I see no links either. Please try again.

 

[Mechwill]

sorry about that please see the picture below:

Current setup:

 

[77JQX]

Generally, when volumetric measurements are too imprecise, laboratory folks use weight instead. But first, I'd try a graduated cylinder with a smaller diameter.

 

[BigInch]

Don't try to calculate that. Too many imprecisely defined parameters, filter pressure drops, control valve Cv's, nozzle losses. Calculations do have their limitations. Conduct experimental measurements, if you don't want to waste your time and lose your mind in the process.

I hate Windowz 8!!!!

 

[Mechwill]

I did try to use bernoulli's energy equation to calculate the siphon part of it, assuming incompressible flow and steady flow, without regulator, control valve, flow meter. However, the 10 psi air inlet kinda throw me off because the fuel is drawn by 10 psi air, not atmosphere pressure. Also, because of the mixture of diesel fuel and air, the density of mixing fluids changes which makes it harder to solve the problem.

I was thinking to replace the graduated cylinder with a glass tube and a Totalizer. In my opinion, it's more accurate than a stop watch and an eye-measurement. I am not sure what you guys think of that.

 

[BigInch]

Bernoulli would give you an idea about the diesel flow, but you have 2 phase, primarily gas flow, with droplets. Gas has very little mass at low pressure so no static head pressures will be developed and at low velocity, no velocity head to speak of either. You must have taken a lot of decimal points out of service for a short while.

I hate Windowz 8!!!!

 

[Mechwill]

Hi BigInch,

Sorry if i misunderstand your comment, you are saying it wouldn't matter if I place the fuel tank 4 feet below the center of the nozzle. Does that mean there can be zero pressure with differential pressure and velocity in the fuel line?

I am trying analyze the configuration of a Two-Fluid nozzle. It basically has a nozzle head, a fuel distributor, and a stem. In between of the nozzle head and the fuel distributor, there is a small space for air and fuel mixing together before the mixture sprays out of the atmosphere. Obviously, there will be a pressure drop when the mixture is released out of the nozzle head similar to orifice application. What about the small space that mixes the air and the fuel? Will there be any pressure drop compared with 10 psi air inlet?

 

[BigInch]

Mostly I'm saying that I doubt you will be able to calculate those flows accurately, even if you use the right methods. I thought you wanted to do that, but in any case I agree with the others that have said experimental flow measurements by measuring volumes lost in the containers over time will be your best bet.

I hate Windowz 8!!!!

 

[Mechwill]

Hi again BigInch

Thanks for the comment again. I think that's what I will do with this experiment. Just a quick question, what's the difference between using graduated cylinder and experimental flow measurements by measuring volume lost in a containers over time?

 

[tbuelna]

Since this is a mixing nozzle feeding an air-diesel mixture to a burner, I'd imagine that measuring the mass flows of air and diesel are of more concern than measuring volume flows. The easiest way to measure mass flow of the liquid diesel is simply to use a scale to measure the change in weight of the fuel tank over a fixed period of operation at constant conditions.

 

[Mechwill]

It sounds like a very simple and accurate set up to me. Once again, thank you very much for all your information guys. One last question, if i want to use some sort of data-logger to do a flow rate versus pressure measurement of the air and fuel, can anyone recommend a supper that has this type of equipment?

 

[Compositepro]

The type of graduated cylinder that you would be looking to use is called a burette.

http://en.wikipedia.org/wiki/Burette

The level change will will cause a flow rate change. The be accurate you need to move the burette up as the level falls, or use the burette to feed the equivalent of a carburetor float bowl.

What you are designing sounds exactly like my kerosene Ready Heater, which looks and sounds like a small jet engine.