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Originally Posted by redneck
Lately, there has been a few new threads coming out pushing the boundaries of accepted knowledge.
I welcome this...
There’s more than one way to skin a cat...
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True, and I appoligize for having done this.
It can happen that something out there that we know-it-alls think has been done and tried and beaten to death with a dead horse on a stick to the point it's not worth looking at that in reality is the key to something perfectly practical and beneficial.
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Originally Posted by racprops
A change of state, from a liquid takes a fair amount of energy, and to condense a vapor takes the removal of a fair amount of energy, in other words to get vapor you need to really heat if up and to turn it back into a liquid you need to do a lot of cooling.
Stuff has a tenancy to stay in the state it is in. My understanding gasoline once vaporized will stay as a vapor for some time unless acted apron by a drastic temperature drop.
And again, once in a vapor state there will be NO liquid droplets to cool the mix, and they do that because of their absorbing heat as they are changing state into vapor and it will all BE VAPOR.
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Dew point.
Stuff does not really have a "tendency to stay in the state it is in." There are many variables here, such as the temperature of the air and how saturated it already is (e.g. humid vs. dry air). But just feeding a hot gas into a cooler one does not mean the hot gas will have a tendency to stay a gas.
If you look at a tea kettle with boiling water you see white "smoke" coming out of the top. Steam is completely transparent just like air. What you see are water droplets formed from the steam cooling in air.
The same will apply to gasoline, especially since some of gasoline's contents need to reach about 200° C in order to boil, which is 100° C more than water. The question is what is the dew point of gasoine in air. Surely it varies, but I don't see air holding nearly 7% of it's mass in liquids that boil up to 200° C at ambient temperatures.
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Originally Posted by racprops
Timing will indeed need to cut back, to zero most likely as unlike gasoline droplets which need time to be vaporized BY the early start of combustion, vapor will flash burn producing more pure power to drive the piston and in correctly metered be completely consumed at the end of the combustion cycle and there will be no farther burn, thus much less engine heat. Also as there is no early start of combustion they will not be expanding gassed for the piston to fight as it tries to compress them. This could also add to the power output.
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That all sounds good and all but I feel is overly optomistic. We already have engines that run on completely vaporized fuels such as hydrogen, propane and natural gas, and none of those work at zero timing advance since they run better with advanced timing. There is no reason vaporized gasoline would work any differently. I would think gasoline would be even worse because it has a lower octane which, long story short, means you end up with a slower burn or it will detonate, and detonation means ˇadiós motor!
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Originally Posted by racprops
And here you thinking of the other vapor fuels which contain less BTUs that gasoline, all the power gasoline make is from its vapor state, liquid does not burn.
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"liquid does not burn." Well duh! I fully understand that. But that's not what I'm talking about.
When you boil a liquid it can expand well over a thousand times it's original volume, and many times even far more. A voluminous gaseous fuel displaces a lot more of air that can get into the engine than a liquid fuel does. You can't just make gasoline 1,600 times or more it's original volume and expect to get the same amount of air into the engine without adding super or turbocharging. Simply put, gaseous fuel means less air and fuel will get into the engine.
This also doesn't take into account that feeding 200° C boiled gasoline vapors into the air is going to increase the air's own temperature causing it to expand before getting into the cylinder, which means even less air will enter the engine.
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Originally Posted by racprops
You’re talking the current state of thinking….finer and finer atomization. ALL to TRY to help those droplets vaporized more…none the less there is still left over fuel otherwise they would remove the cats as they would no longer be needed to clean up the unburned fuel.
Rich
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There will always be left over fuel in the exhaust even if you vaporized all the gasoline. The same happens with other gaseous fuel engines.
Why? Because of quench.
The flame stops burning when it gets to a certain distance near the combustion chamber, the valves, the piston and the cylinder walls. At this point the flame is too close to the metal which, even at temperatures of up to 200° C or more is too cold to let it burn. It ends up sucking the heat out of the flame where the flame gets close enough and leaves a thin layer of unburned air and fuel vapor along the edges of all the metal parts.
The reason small droplets can burn is that the flame that propagates throughout the combustion chamber is around 1,500° C, plenty hot to vaporize any liquid fuel droplets that are small enough. Not that there isn't some potential benefit of reducing them to the point they are completely vaporize, but modern gasoline engines already burn up to 90% of the fuel (or more) in the combustion process. And most of that 10% (or less) of fuel that isn't burned up in the combustion chamber is from quench which is still a problem in gaseous fuel engines.
It would seem that reducing or eliminating quench would be more important if you want to burn up 100% of the fuel in the combustion chamber. One way is using a stratified engine.
But anyhow, you could still be onto something. I wonder what combining a gaseous fueled engine with a stratified charge or some other idea would lead to in terms of thermodynamic efficiency.