Fuel Vaporizer

[oil pan 4]

Yeah natural gas engines do some weird stuff.

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

I don't know if this is possible for gasoline vapor, but I read once somewhere on the all-knowing internet that propane (and natural gas) engines can run much leaner than liquid gasoline engines.

I'm not so used to LPG as a motor fuel, since it's actually only allowed in my country for forklifts and other material-handling equipment not really meant to operate on public roads, but the first vehicle with automatic transmission I drove had been upfitted to also run on CNG besides gasoline. It's possible to run leaner on CNG, since its anti-knock properties are better even than ethanol. But with an excessively lean AFR, power goes down considerably.

This also allows for kind of a diesel-like throttling where you can run super lean, keep the throttle valve wide open and adjust throttle by means of introducing more gas (gas as in propane).

It's not so simple to get such a Diesel-like operation, as it remains relying on the spark ignition. It might be also dependent on which generation the CNG conversion kit is based, or if the engine is converted to dedicated-CNG which might enable some different approaches with a stepper motor and a so-called "mixer" instead of a carburettor.

On another note, wouldn't the air also have to be very hot to keep the gasoline completely vaporized and dry?

A hotter air intake would eventually require more gasoline to keep its charge cool enough to prevent knocking.

Otherwise wouldn't some of the gasoline just condense back into small droplets in the intake charge?

With a colder intake, a smaller amount of gasoline evaporates. Considering the modern engines fitted with EFI, they set a lower AFR exactly to keep the engine at its standard operating temperatures. Notice it in a rainy day, the fuel consumption usually goes down due to the colder air with more moisture on it

[aerohead]

Originally Posted by 2016 Versa

I was on You Tube a couple days ago and saw people who claimed to be running their engines strictly on gas vapors from homemade vaporizers. I was just wondering if anyone here has ever tired this and what their outcome was. I can see where it might work but, some of the homemade systems I was seeing didn't look like they would be very safe and some looked like downright fire hazards.

Lindsey published a booklet, with at least a dozen examples, including the 'famous' FISH and POGUE carburetors.
A careful reading leads to the revelation that the carburetors CAN remarkably improve mpg, if you 'push' the car up to 35-mph, start it, then drive 35-mph ( because that's all they it will do ), until you're ready to stop.

[Isaac Zachary]

Originally Posted by cRiPpLe_rOoStEr

A hotter air intake would eventually require more gasoline to keep its charge cool enough to prevent knocking...

With a colder intake, a smaller amount of gasoline evaporates. Considering the modern engines fitted with EFI, they set a lower AFR exactly to keep the engine at its standard operating temperatures. Notice it in a rainy day, the fuel consumption usually goes down due to the colder air with more moisture on it

I think my question is what's the dewpoint for gasoline in air? Let's say you're going for a stoichiometric AFR. What temperature would the air have to be in order to assorb all that gasoline?

You can vaporize as much gasoline as it will boil. But just like a tea kettle that's on the stove, once the steam (vapor) hits the cooler air it forms liquid droplets (the white "steam" that you can see coming out of the whistle). If the air saturates with gasoline the same thing will happen, much of the vapor will transition back into liquid droplets, which you could have gotten the same effect with a good fuel injection nozzle.

The air will have to have a minimum temperature in order to contain purely vaporized gasoline. Any cooler and you get droplets. But how hot would it have to be? Adding more gasoline to cool the intake charge wouldn't help efficiency at this point.

In other words, you boil gasoline in a vaporizer to get gasoline vapor
>but the air is too cool to keep that gasoline as a vapor, so it turns back into droplets, which should defeat the purpose of vaporizing the gasoline in the first place,
>so now you have to heat up the air too so it can hold more vapor without saturating and causing gasoline to condensate back into liquid,
>But now you have a hot dry charge of stoichiometric air and gasoline vapor that causes detonation, knock and maybe even other such problems.
>So the solution is to add more gasoline, which now puts us at a rich AFR, which wouldn't lower the intake charge temperature because no more gasoline can now evaporate because we are at the dew point already, but at least it will evaporate during combustion and hopefully cool the combustion process enough to prevent detonation.

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

You can vaporize as much gasoline as it will boil. But just like a tea kettle that's on the stove, once the steam (vapor) hits the cooler air it forms liquid droplets (the white "steam" that you can see coming out of the whistle). If the air saturates with gasoline the same thing will happen, much of the vapor will transition back into liquid droplets, which you could have gotten the same effect with a good fuel injection nozzle.

The pressure increase during compression stroke, and the direct proportion between pressure and temperature, is more likely to avoid the gasoline vapors to condense back into liquid, as long as the mixture is not excessively rich.

[Isaac Zachary]

Originally Posted by cRiPpLe_rOoStEr

The pressure increase during compression stroke, and the direct proportion between pressure and temperature, is more likely to avoid the gasoline vapors to condense back into liquid, as long as the mixture is not excessively rich.

That gives me an idea! If under experiment we find that the intake temperature has to be higher to keep the fuel vaporized then this could be used in conjunction with a miller cycle engine.

However, then the ability to keep the fuel vaporized could change depending on throttle.

[Stubby79]

The greater the vacuum, the lower the boiling/vaporizing point, in theory...plus there's engine heat...I doubt you'll have to be worried about it condensating. Except maybe if your engine is dead cold and you've used heat to make it vaporize quicker in the first place. A temporary state, at best.

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

If under experiment we find that the intake temperature has to be higher to keep the fuel vaporized then this could be used in conjunction with a miller cycle engine.

There is a Brazilian ethanol-powered Volkswagen-based car which resorted to an intake heater in order to avoid the usage of gasoline for cold starts, and it used only one glowplug mounted on the intake elbow. That glowplug was of the same type fitted to the 1.6L EA827 Diesel.

[mpgmike]

George Wiseman (Eagle Research) had his HyCO bubbler that effectively admitted a little fuel vapor into the intake air stream. He worked out mechanical controls to effectively regulate flow, as well as lean out the carburetor to compensate (this was back in the 1980's and '90s). If this topic interests you, the proven HyCO might give you some ideas.