Terraclean - snake oil or not?

Apologies for going to work, anyway

if you're bothered. If you add water to the charge & add the same amount of heat you'll reduce the peak temperature by more than you'll reduce the exhaust temperature, you'll need to cross refernece the gross enthalpy after combustion on the steam chart to see by how much.

Diesel doesn't - its atomised into tiny droplets, not evaporated. Thats the reason its such a filthy fuel - you can't get a complete burn.

-- Spud

On 01/05/2014 20:35, snipped-for-privacy@potato.field wrote:> On Mon, 28 Apr 2014 09:21:36 +0100 > Peter Hill wrote: >> Liquid has to evaporate before it can burn and that cools the charge. > > Diesel doesn't - its atomised into tiny droplets, not evaporated. Thats the > reason its such a filthy fuel - you can't get a complete burn.

Liquid diesel doesn't burn, it puts lit matches out.

I refer you to chapter 1, paragraph 1 of 1968 5th edition "The High-Speed Internal Combustion Engine" by Sir Harry Ricardo.http://estore.ricardo.com/shop/the-high-speed-internal-combustion-engine/

I could teach Honda "A" thing. Just the one thing mind you. I'd be teaching them what Lanchester knew about 90 years ago.

Yes it does, it just has a high ignition temp. Point a blowtorch at some diesel and it'll catch fire and continue burning quite happily.

Obviously he kept what he knew to himself then otherwise we'd have had 5K rpm,

60mpg, 150hp diesel engines that could fit under a car bonnet back then wouldn't we.

-- Spud

Science and engineering don't necessarily march in step.

If liquid diesel burns then why didn't the fire spread right across the pond the instant it was lit? Why did it spread so slowly? Why did the guy with the torch have to come round the front at 1min into the video to start a 2nd flame front?

It's not the liquid Diesel burning. It's vapour above the pond. They had to heat the Diesel so it would give off enough vapour to burn. Then they had to keep on heating until the burning vapour gave off enough heat to create enough vapour for it to become self sustaining. Even then the liquid diesel didn't burn and the flame front spread slowly.

Even liquid petrol doesn't burn. But it gives off a lot more vapour at normal atmospheric temperatures, enough vapour to get a mixture within combustible limits, so it can produce an explosive vapour cloud. If you made a pond of petrol and lit the vapour above that the flame front would progress very rapidly. But a tank of petrol with limited outlet pipe flow and vents is fairly safe unless heated to quite high temperature (hotter than Diesel). Petrol vapour in a petrol tank has too rich a mixture to burn. A petrol tank is at it's most dangerous when it has been drained, then the mixture in the tank can be below the rich limit. With liquid petrol in the tank and the limited admission of air though the filler/vents the vapour concentration in the tank will quickly exceed the rich limit.

Depending on flow, a gas leak that is vented to atmosphere is safe. 50 years ago we had a hollow tube gate post. There was a smell of gas from it (town gas back then), mum called out a man from the gas board. The guy came round and said it was a leak but not dangerous, it was too weak a mixture to burn and as it was vented it couldn't build up to a dangerous concentration. It was put on the get around tuit list but if it got worse she was to call again. It was still leaking when we left there a few years later. I now live in the house next door and it's not leaking now. I think it was fixed when they switched to North Sea Gas in '67 as that's combustible at weaker mixtures (all the gas appliances had to be fitted with smaller gas jets).

Q: Does the liquid itself burn? A: No.

Flash point. How hot the vapour has to be to lit. Auto ignition temp, how hot the vapour has to be to ignite without a ignition source. And a 2nd confirmation that liquid doesn't burn But vapour won't burn unless the mixture is between the Lower Flammable Limit (LFL) and Upper Flammable Limit (UFL).

Thank you for writing that, it was irritating me too.

My favourite gas with the widest mixture range is of course acetylene. I accidentally exploded about a pint that had built up in the fluid reservoir around a pillar drill table. The torch I had put down on there had the tiniest leak of gas either because I had not turned it off fully, or knocked it as I put it down, when I relit the torch there was the most almighty bang, despite no real containment of the gas. Very frightening but luckily no harm done.

Excuse me? You might as well ask why doesn't coal burn instantly. It takes time for it to get hot enough.

Oh right, and I suppose for coal to burn we need carbon "vapour" first do we?

Yes, there will be vapour, but liquid can burn directly and it doesn't change the fact that when diesel is injected into an engine it is NOT in a vapour form unlike petrol, so stop posting irrelevant dissertations to try and wriggle out of the fact that you didn't know this.

Yeah well its wrong - its an engineers view of chemistry. The molecules in the compound don't give a toss which phase they're in - if there's enough energy they'll react with oxygen. The fact that the energy required may be hot enough to move them from the liquid to the vapour or gas phase so speeding up the reaction is neither here nor there. Burning is just an oxidation reaction and if all chemical reactions with liquids required the vapour phase before they occured chemistry would barely exist.

-- Spud

In article , spud-u-dont- snipped-for-privacy@potato.field scribeth thus

In fact if you look at a burning coal fire the coal is giving off a gas that burns.

Remember what happens in a Gas retort in an old town gasworks when coal is heated?..?...

Now you are just being obtuse.

Yes in the wrong mix a factory full of flour dust can explode.

The Diesel fuel is injected into air compressed to a high temperature so the surface of the fuel droplets vaporises on injection and before combustion.

But liquid petrol or Diesel doesn't burn.

As a chemist you must know that to burn the fuel needs oxygen. There isn't enough oxygen in liquid petrol or Diesel, if there was it would be an explosive like Semtex. Due to the fuel vaporising there isn't enough oxygen at the liquid surface, it's blanketed by vapour. So combustion is at the air/vapour interface at the point where the mixture is below the UFL.

Not really , just leading you on to a logical conclusion.

That is no partially what happens, but:

A) You weren't aware of this last week B) Not all of the fuel vapourises, hence the carbon soot

If a droplet is moving that vapour will be blown away so there will be O2 in direct contact with the liquid.

Not always.

Some coal contains volatiles, some doesn't. If there are volatiles in it then they will vapourise when the coal is burned and add to the fire.

So are you trying to say that pure carbon can't burn? If so you might want to tell the coke and charcoal industry because clearly they're wasting their time.

In article , spud-u-dont- snipped-for-privacy@potato.field scribeth thus

Well be a bit more specific then;)....

In message , Peter Hill writes

So does liquid petrol - but don't try it at home!

Not quite right. I defy anyone to plunge a lit match into petrol without lighting it. You can however stub out a cigarette in it. I've tried it at home. ;-)

Tim

Are you sure you don't mean a cigarette? They burn at a lower temperature than petrol ignites at. But not the match you light it with. ;-)