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Old 05-04-2021, 06:07 PM   #20 (permalink)
Isaac Zachary
High Altitude Hybrid
 
Join Date: Dec 2020
Location: Gunnison, CO
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Avalon - '13 Toyota Avalon HV
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Quote:
Originally Posted by Piotrsko View Post
How are you going to keep it emulsified AND run it through all those things that remove the water or not clog up the system? Mold is a diesel fuel tank is not fun.
Obviously, like with anything, there are pros and cons. And there's a huge difference between what a regular DIY'er can do, what can be done in labs and what might make it as a potentially commercial product.

One thing would be to remove the return line all together and mix water as needed with fresh fuel near the engine. That way you could keep the fuel tank water free as well as have emulsified water in as few lines as possible. You may need some sort of mini fuel cell up near the engine for a return and add fuel from the main tank as needed. That way cleaning out the fuel system from bacterial build up could be made easier. Also, if you can keep the emulsified fuel and water within a pressurized system, like the fuel rail, then the temperature could be increased without causing boiling. The high temperature could help mitigate or stop bacterial and fungal growth.

There are additives that either help absorb water or expel water. If the water is mixed well enough into the fuel then mechanical water separation becomes basically imposible. You can run the emulsified fuel through a water separator all day and not get a drop of water with the right additives, depending on the amount of water of course.

Also, water can be basically homogenized into the fuel by means of ultrasonic mixing without the need of additives. Of course there'd be a greater chance of separation of water and fuel over time without the additives.

Of course, besides bacterial growth, there's the problem of corrosion. Water can cause things like expensive fuel injectors to rust from the inside. So building parts out of materials like stainless steel might be the only way for it to work.

Another problem would be startup would be difficult unless you had a way to switch between plain fuel and emulsified fuel. One way of acheiving this is having a small loop that uses emulsified fuel and switching over to pure fuel for the last part of the trip in order to use up the emulsified fuel in the loop so that during the next startup it can start on pure fuel.

But one theoretical type of emuslified fuel injection system that would solve a lot of the problems would be an injector that basically injects water and fuel at the same time and somehow mixes them together during the injection event.

But in any case, cold weather and freezing would be a problem that would have to be dealt with, as in the case of any water injection system.

The main question is if the benefits outweigh all of these design challenges.
  • By injecting the water directly into the cylinder during combustion you eliminate any cylinder wear from water droplets affecting lubrication.
  • Also, the emulsified water boils in "microbursts" during combustion which helps with fuel atomization and ultimately burning, which reduces particulate matter.
  • And of course it also reduces combustion temperatures which reduce the formation of NOx.
  • It also puts the water right where it needs to be in a stratisfied charge, like in a diesel engine, that is to say right where combustion is occurring. This allows for the use of less water which can reduce the unwanted side effects of water injection, like overcooling and lowering the specific heat ratio of the combustion charge, while maintaining or even improving the benefits of water injection.

I think that if it can be pulled off it would be a great alternative to EGR. EGR on a diesel seems to only reduce efficiency. This could not only increase efficiency, but also reduce major diesel pollutants such as NOx and particulate matter at the same time, and do so much more effectively than just spraying water into the intake.
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