Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

[brianthesnail96]

Sorry folks, me again...

For the experimental part of my experiment, I really need to know how much gas I'm using over a fixed amount of time; getting the loco to run consistently over e.g. a gas tank full for say 30- odd runs might be a bit of a challenge! So ideally I need a regulator that I can fit directly to a butane bottle, with some form of flow meter so I can set the gas to a fixed consistent rate for each run, and then time it so I know how much I've used.

Does anyone have any ideas as to where I may procure such a device, or failing that how I'd go about making one?

Thanks again folks.

The plan is to raise a known amount of water to a certain pressure in the boiler; I can work out how much energy that takes from steam tables. If I know how much gas it uses to do that I can work out how much energy there was in that gas, and get an efficiency; obviously it won't be the true burner efficiency due to all the heat transfer losses, but I can get a relative efficiency which is what I actually need, as the losses will be constant.

As the burners will be most efficient at different gas flow rates I'll use a variety of flow rates for each burner- I'll probably do 5 runs at 5 different flow rates for each burner.

 

[3Valve]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

God I'm a plonker. Just spent the last fives minutes trying to work out what a gas regulator with a "flower" meter is

 

[brianthesnail96]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

Close but no cigar Gareth!

I've just had a thought- the regulator on Edrig is separate to the tank- so all I really need is some sort of flow(er) meter, I can use the standard gas regulator.

Might make life a bit easier.

 

[Doug]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

Could you go on the weight of gas used over a fixed period of time. Would need to keep its temp constant though!

 

[johnsaintjim]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

Matt there are loads of gas flow meters for sale on ebay. I can't see one for butane but there are air, argon and CO2 meters. Maybe you only need a relative flow rather than absolute numbers so you could use a meter and maybe even calibrate it yourself.

Something at the back of my thick skull is telling me the number on the gas jet is the flow rate in cubic feet per something (minute? - but that seems a lot - 6 cfm through that tiny hole??). Gas jets will be calibrated at very low pressures - only millibar.

This place in the US seems to specialise in flow meters: http://stores.shop.ebay.co.uk/FLOWMETERS-FOR-SALE__W0QQ_armrsZ1 .

Hope this helps and I am fascinated to see how this topic unfolds.

 

[Chris Bird]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

Hi Matt
My first thought is that for a given setting on the valve, the flow rate will vary with the temperature of the tank. The tank therefore needs to be insulated from or separate from the loco. I have no idea about a flow meter for gas - but it seems to me that a separate gas tank and valve could be weighed before and after on a precision balance to get the amount of gas used. You would really need the balance for the water too as ensuring a dry boiler then adding a given amount would not be as easy as weighing.

A friend at the local ME club tested his boiler design by using temperature sensors at the end of the flue - this gives an indication of the wasted heat (which will be more if the burner is set too high). He tested cross tubes and a copper spiral - and both had a significant effect if I remember correctly. A CO analyser in the exhaust would also be interesting to determine whether you have optimum combustion.

One more thought would be a test rig with a flue tube and temp sensors at say 50mm intervals. Running the burners in this and recording the time temp graphs would show the rate and distribution of heat transfer...........

Apologies if this is stating the obvious

Good luck!
Chris

 

[brianthesnail96]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

I was planning on using an external tank- possibly even a gas bottle- at sufficient distance from the loco as to not be affected by temperature change. As such, weighing it would be a far more straightforwards method of working it out, and something I hadn't even considered!

Not stating the obvious at all Chris. This is very much new territory for me- i.e. I haven't really got the foggiest what I'm doing- so it's all very useful stuff.

Temperature sensors is a nice idea indeed, although having them in the flue may affect the gas flow a bit. I suppose if they are above the burner they won't though- something else to look at, and something that will give me lots of pretty graphs- excellent!

I was worried that just a "it used this much gas to do this much heating" was as bit GCSE, so expanding it to include that is an excellent idea

 

[johnsaintjim]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

But the gas will cool due to the latent heat of vapourisation and therefore you won't have a constant pressure if you just release the gas from an isolated tank. As long as the tank is big enough then at your flow rates that may be negligible but you would need a decent size bottle.

I would say you are on track by specifying a regulator rather than a simple valve. Flow meters are simple bits of kit in principle with a cone shape which fits into a tube with gradations on it.

 

[brianthesnail96]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

I've not actually asked the uni yet, they may have something suitable.

I wouldn't have thought that using enough gas to bring cold water up to say 40psi from a large gas canister would have a massive effect on the pressure of said canister. Something to consider though, and a flow meter sounds more professional!

 

[Chris Bird]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

Hi again Matt
I was thinking of temperature sensors on the outside of a test rig tube - they will heat up quickly though in the absence of water - but you would be able to plot the effect of different burners. Alternatively if you use a thermal imaging camera - you will be able to see the effect at given settings. Perhaps the key factor for comparison would be to have a pressure gauge (it would need to be accurate at low range) in the line between the gas regulator and the jet - that way the thermal image of different burners would be related to different pressures.

When heating water though, the requirment would be different. Here you will be able to find out the calorific value of the gas mix (it must be available somewhere) and thus from a given weight of gas you will know the potential calories. The time taken to heat the boiler (weight and specific heat known) and water (volume and starting temperature known) could thus be converted into an efficiency......

Now my brain hurts as it is 40 years since I did anything like this!!!!!!!
Cheers
Chris

 

[Doug]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

Surely the temperature of the gases leaving the flue would be a good indicator of the efficiency of the burner/flue, the lower the temperature the more energy transferred to the water in the boiler. Though this may not help with just the burner design as the amount of air/gas going in will be different.

 

[brianthesnail96]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

That was what I was hoping to do Chris- work out the potential energy in the gas, which I'm sure I can do and even have equations for somewhere, and the energy required to heat x amount of water to x psi (I need a better pressure gauge for the loco too- any ideas anyone? Ideally a big, accurate one that I can stick onto the standard pipework) I can obtain easily enough. That's not massively complicated though, so using temperature sensors as well in a secondary experiment is a very interesting idea to pad things out a bit!

Still lots to think about. Thanks all- again!- for your help

I owe you all one, or several...

 

[Chris Bird]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

Hi again Matt
All (well almost all) you need to know about the heating ability of gasses is here: http://en.wikipedia.org/wiki/Heat_o...rner/boiler combination. Cheers Chris

 

[brianthesnail96]

Re:Gas regulator with a flow meter- doesn't have to fit on the engine!- more dissertation!

You aren't Nick- I wasn't even aware such a device existed!