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Re: pressure jet burner
Posted by: Mike Clark (
Date: March 18, 2006 06:28PM


You’re converted then - or reconverted!

A pressure burner is probably the best type for a water tube or monotube steam generator but I doubt whether the Stanley boiler can absorb heat as effectively from such a burner. The vaporising burner at least has the advantage of a fairly uniform distribution of heat across the bottom tube plate of the Stanley boiler.

As to fuels, I’m not sure what the definitions are for paraffin, kerosene or heating oil. They all seem similar and no doubt any of them can be made to work in a vaporising burner provided the vaporiser length and jet sizes are optimised. The problem with them is that the specification needed for the intended use of these brews is not at all critical so any old rubbish can be, and often is, supplied. Although the vaporising burner is pretty tolerant it works best when fed with the fuel it is adjusted for. If the vaporiser length is wrong or the jets of the wrong size the fuel coming from the jets can be too cold which can make the burner flood, or too hot which will carbon up the vaporiser and block the jets. Variations in the fuel may lead to these problems which is why many of us use a petrol/diesel mix in our cars which has the further advantage that you can buy it mid-trip.

Petrol and diesel have to be made to a close specification as they are meant for use in a critical environment and within reason we can be sure that we are getting the same fuel wherever we buy it. Adjustment of the vaporiser and jet is relatively easy as the fuel proportions of the mix can be varied to get the best result. Some use 60/40 diesel to petrol but I have found that with a 6 foot vaporiser in my 23 inch burner a mixture of 50/50 works best.

A single fuel system would be nice - the original Stanleys up to 1914 used only petrol and if you insist on a single fuel system I would do the same. It is very hard to make a pilot light to work with kerosene, it’s bad enough using petrol instead of hexane, simply because the stuff is so hard to vaporise although the Cruban Empire pilot was claimed to work with kerosene. I spent a long time developing a reliable pilot to work on petrol and did finally achieve that (see the current issue of “The Steamcar”). This has been totally reliable and has gone out only once - significantly this was when I got distracted by talking to a passer-by when firing it up and accidentally fed the pilot with a dose of 50/50 petrol/diesel. I imagine it would be possible to make a pilot to work with kerosene (after all the old plumber’s blowlamps did) but it would then be suitable only for kerosene and would be susceptible to the variable quality of fuel.

It is said that diesel has more energy in it than petrol and so gives more power. Actually the energy per kilo of hydrocarbon fuel is much the same per kilo of fuel, it is just that diesel is denser than petrol and so has more kilos per litre. The significance of the “extra power “ in a burner is, I suspect, mainly the economic consequence of buying fuel by the litre not by the kilo. I would definitely stick to petrol for a single fuel car as diesel alone would be a nightmare to burn and the lighter kerosene is not there to be bought by the roadside. In a boat the situation is quite different because the burner is not constantly closing down and relighting. No doubt a kerosene vaporising burner for a boat could be made to turn up or down as needed.

Your final question about burner howling has not been conclusively answered in the last 90 years. Stanleys found that changing from petrol to kerosene made their burners (which until then had slots not holes) howl very badly. They reduced the problem by changing to the drilled burner plate. There is no conclusive explanation of burner howling though many theories have been put forward. It is an acoustic effect in the burner fire tubes like blowing across the top of a bottle. I get a similar effect in the chimney of a wood burning stove at a much lower pitch. It does seem to depend on atmospheric conditions, on how hot the boiler is (more howling while firing up with a cold boiler than when up to temperature), on air flow into the venturis (howls more with any kind of deflector in front of the intakes) and with the level of vaporisation of the fuel. My burner mostly runs with a very clear gas stream ( fully vaporised) and rarely howls unless going up a steep enough hill to get the fuel automatic wide open or if the burner has been shut down at a stop or going down hill when we get a short chirrup of a howl for a few seconds. In both circumstances I suspect the fuel is not as well vaporised as it should be. I can also stop the howling by giving a bit more drsft with the stack blower so airflow through the whole thing is significant. You can’t avoid some howling but I do think constant howling is an indication of poor vaporisation.


Edited 2 times. Last edit at 03/19/06 09:10AM by Mike Clark.

Re: pressure jet burner
Posted by: Jeff Theobald (Moderator)
Date: March 19, 2006 06:35AM

Hi Mike,
I am surprised at the length of your vaporiser, is it very low (close to the burner plate) what type of burner plate are you using? fuel pressure? jet size? and venturis diameter?

thanks. Jeff.

Re: pressure jet burner
Posted by: Mike Clark (
Date: March 19, 2006 09:09AM

Jeff - brain fade - must be the effects of all the salt on the winter roads - of course it's 6 feet. John Goold drilled burner with about 7000 holes. Jets 60. pressure 120psi and venturis 1.625 inch. Vaporiser is level with the connection to the branch forks. Have corrected my original post. Thanks for noticing that!

I've just had the engine cover off to check it over - no problems and the whole engine was absolutely spotless after running 1500 miles last season which shows that the drip feed oiling system is effective - all the muck is on the road! If you look to the top right of the engine you can see the drip feed oil reservoir and the pipes feeding oil to the little ends, also pipes running along the top of the engine through which I can inject oil to the main bearings and eccentrics. Below the engine is catch tray into which the crankshaft gear dips to pick up oil and throw it over the link mechanism. This is the answer to the oilong problems of the "dry" Stanley engine.

Going out now for a first steam up - can't go on the roads yet becasue of the salt - you Southerners are lucky to not have this problem.


Click the picture for large version....

Edited 5 times. Last edit at 03/19/06 05:11PM by Mike Clark.

Re: pressure jet burner
Posted by: (
Date: March 19, 2006 04:11PM

Thanks for your comments. I haven't totally given up on the pressure jet yet, still resisting Jeffs predictions!! One advantage I have found is that no howling occurs, at least it doesn't at 2 gall/hr
If I am to reconvert to vapouriser I need to know that I can use a paraffin pilot. Your comments on fuels confirm what I have found with kerosene----it is variable, but paraffin seems to have good consistency, the one I get is blue-ish in colour. It is a bit dearer than kero but a lot cheaper than diesel or petrol from the filling station. I just don't like having petrol on board---reminds me too much of driving an internal combustion car. As you say the old plumbers blowlamps worked fine, usually I think on paraffin. I know it seems that most people consider paraffin and kerosene as virtually the same product but I think that when vapourising to the max.and for long periods as is necessary for us then the difference is seen in reliability.
Does the fact that petrol and diesel have different densities not cause problems with uneven mixing when the car has been standing ?

As you suggested, the howling is obviously the result of blowing lots of air across lots of holes in the burner plate (flute) and then up the firetubes (organ). It is a shame since it detracts from the otherwise inherent silence of a steam car. My burner/boiler howls like a Banshee most of the time it is working but I am sure vapourisation is good since the gas from the nozzles is completely invisible. The only way I can reduce/eliminate it is to reduce fuel pressure, then I don't make enough steam !


Re: pressure jet burner
Posted by: Mike Clark (
Date: March 19, 2006 05:28PM


It should be possible to make a paraffin pilot but I suspect you will find that paraffin itself varies a lot. I wonder if it might be more prone to coking up jets than petrol? The old paraffin blowlamps certainly were a damn nuisance! Also from the point of view of driving any distance you will have a problem buying paraffin at the roadside.

I don't think there is any problem of separation of petrol and diesel in the tank during storage - after all they are both mixtures of different length hydrocarbon chain molecules, petrol with chains of 4 to 12 carbons and diesel of 8 to 15 or thereabouts. the combined mixture just has a wider range of molecules in it. Don't however make the mistake of thinking that such a mixture is "safer" from the point of view of inflammability, the vapour above a tank of mix has all the very inflammable bits there just like petrol and it is probably just as inflammable.


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