Can anybody help on my final year design project? Our group is designing a Diesel fuel purity device on vehicles. The engine is diesel and when it is fueled by an unleaded gasoline the device doesn't accept it and it will go out to another valve. When water is mixed with diesel and fueled to the tank it will also go out to the other valve. Only pure diesel fuel can enter the tank.

Can somebody help us on our design. On what sensor or detector to use to detect only pure diesel fuel and rejecting other kinds of fuel or impurities of diesel. Hope that you comply with my problem. Thanks in advance.

God Bless.

 

This is related to your earlier thread - http://forum.allaboutcircuits.com/showthread.php?t=52271

Have you done any research since then on sensing the diesel fuel, or sensing water in it, or in distinguishing gasoline from diesel? If this is your project, you should have made some progress with this in some areas.

 

'Diesel', as a fuel definition, is a very broad term. You would need to define your parameters that equate to 'pure'. Specific density is going to one of your guiding parameters, and sensing it, I would think, would go a long way in sensing your fuel quality.

You should probably expand on your intended end use to garner comments appropriate to your needs.

Filtration is your first defence. Water isn't a particularly bad thing, if finely suspended. Improving filtration, typically via mechanical methods (screening, centrifuge, etc), may be more practical then redirection.

 

Yes, density is a good one. Many ways of measuring that. Viscosity might also be useful. As for measuring the water content this might be difficult as water generally does not mix. Will either be finely suspended droplets or will settle out at the bottom.

First you have to design the physical sensor then find a way of getting an electronic output from that.

More research is required, I think!

 

Start the old fashioned way. Do what Thomas Edison might have done if he were to try this. ---EXPERIMENT---

Get some GOOD diesel, and some bad diesel, and some diesel with water in it, and some gasoline. Then get an Ohm meter and check them to see if there is a specific discernable difference between any of them. Shine different kinds of light through them and see what happens to the light. Shine laser light through them and see what happens to that. Get a sensitive scale and put each kind of liquid in a container of a SPECIFIC capacity and see if the weights are the same or different.

Get the idea? TRY SOME THINGS and see what you find out.

 

Have a look and see if the difference in refractive index would be useful.

 

Or maybe change in dielectric constant.

 

what sensor should i use to detect the refractive index?

 

Diesel, unleaded and water are going to differ in density, one way you could do the measurement is have a known volume (say 1 L) with a load cell underneath. You measure the weight using the load cell and it'll tell you if you have 100% unleaded, 100% water, 100% diesel or if you have a diesel water mix.

Refractive index is another method you could use, but you'll have to do some research if it'll let you separate diesel and unleaded. It'll certainly work for diesel/water.

Viscosity is probably not so useful in this case as this measurement is typically best done in a lab, using specialised equipment.

Another suggestion is to measure the resistance/impedance of the solution. This'll certainly tell you the difference between diesel/unleaded and water, but I'm not sure if it'll let you discriminate between diesel and unleaded. If you look up the conductivity and permittivity of the two you'll find out.

And FWIW you can't filter diesel out of water - the two are largely immiscible so you can separate via density (settling or centrifuge) but a filter ain't gunna help here.

 

And FWIW you can't filter diesel out of water - the two are largely immiscible so you can separate via density (settling or centrifuge) but a filter ain't gunna help here.

Gee, some one should tell the filter companies about this! They have been making filters to take the water from car and truck diesel fuel for decades.

 

Finally, a question I can answer...

1. Have you ever been stored in a tank not meant for diesel?
2. Do you collect tanks meant for other hydrocarbons?
3. Have you ever shared a tank with another volatile hydrocarbon?
4. Have you ever dreamed about a single chain alkane with low molecular weight?
5. Have you ever forced another hydrocarbon to attempt miscibility?
6. Do you know any impure diesel?
7. Have you ever lain atop some water with vaporous ideas?
8. Have you ever lain underneath another fluid with vaporous ideas?
9. Have you ever used alcohol to improve another liquid's miscibility?

I'll leave the remainder of the questions as exercises for the students.

 

Gee, some one should tell the filter companies about this! They have been making filters to take the water from car and truck diesel fuel for decades.

Yeah, it's called a filter, but it doesn't use the operation of filtration. There'll be a sump at the bottom of the filter where you drain the water from - this is separation by density. Filtration is a mechanical operation that separates things via size - something that won't work for diesel and water.

And back to the original topic you should pull the specs for diesel fuel (if they haven't been given as part of the project) and work out what the acceptable levels of water and unleaded are. That'll let you know how sensitive your choice of methods need to be.