how does fuel temperature effect performance/economy?

[NintendoKD]

good stuff, question how much oxygen we talkin?  by that I mean temperature wise, ex. @ 60 deg f, oxygen content is X% whereas @ 100 deg f oxygen content is X% how much more compressed is the air, I know that it does.  AKA high pressure system=coldfront, ususally accompanies claimant weather, low pressure system=warmfront when the two collide tornadoes and other natural vortices form.  which brings me to my next point, at what temperature is to warm for fuel, because for a natural "swirl" to occur, inevitably mixing the air and fuel, you need some clash of air and fuel at differing temperatures.  can someone please expound, not only with quantitative but qualitative, in other words, a real world example as well as an engineering/arithmetical explanation.  I work better with visuals, and understand things better this way.  Essentially I want to get the most bang for the buck here, what should we be attempting to achieve pre and post IP?  pre temp optimal, and post temp optimal for the best fuel economy/efficiency the performance comes later.

thanks

[gldgti]

Your weather analogy is ok on a macro scale, but I dont think it really applies in the precombustion chamber.

regarding oxygen - the oxygen content of the air remains the same. The mass of the air changes, and the oxygen is part of the air, so relatively it is the same. (Basically, hot air has the same concentration of oxygen as cold air).

I don't think you will have much luck getting any real results by heating the fuel pre-injection, unless the fuel is for some reason so cold that the injector system components arent working properly.

The best thing you can do is to have all the injectors working at their best (good atomisation). The design of the prechamber itself is already very well thought out. It is a wonder of engineering in of itself... took decades of development to get the design right.

There well may be an optimal temperature for fuel atomisation as it is sprayed from the injectors, but I dont know what that would be. To find it, you would need to do an experiment. But, since modern TDI's regulate their fuel temperature, then aiming for that temperature is probably not a bad way to cheat, if you are keen.

[wolf_walker]

I want a neighbor like you.   

[theman53]

To add to gldgti I would think that heating the fuel would change its flow properties. So everytime you change the temp the timing, break pressure, and fuel quantity would need adjustment. Also, at what point do the seals fail? In basic terms you are doing the same thing the VO, WVO, WMO, etc. are doing. In these engines what are you hoping to gain? 10% is 5hp. It is almost like a lesbian on birth control or separating fly poop from pepper...too much over redundantcy reoccuring again.
The compression part of the ignition of these diesel engines does just what you are wanting, just a bit later than you are wanting.

[745 turbogreasel]

The modern stuff mostly runs fuel coolers to protect expensive pump modules IMO.

[ORCoaster]

In basic terms you are doing the same thing the VO, WVO, WMO, etc. are doing.

That is what I was thinking all along theman53,  We greasers note that the fuel has to be hot to flow like diesel and we note that even when hot it doesn't perform quite the same.  I know I run a few pounds different on hot WVO compared to even warm diesel.  So I do note the timing change and that might be the reason it runs different.  I think it has more to do with the fuel character actually. 

I am not sure we can figure out the extra amount of O 2 in the cylinder compared to native intake.  If boost equals 15 psi how much extra air is that?  15? 

Where is that engineer when you need em. 

They do make wires that you can wrap the delivery lines with that can be heated so if you really wanted to have hotter fuel after the pump and not disturb the other normal settings then there is a possibility for that.  But knowing the fuel sits on those hot injectors long enough to get to engine temp seems like it would do the trick.  How much hotter do you really need to get?  Combustion temps?  Talk about vaporization.  The injectors are designed to deliver a fluid not a vapor.  So best not get it too hot.

[RabbitJockey]

15psi would be over a little twice the air that an na engine would be getting.  But I agree the only difference heated fuel may make would be in how it flows in the pump and injectors which probably effects timing and such and perhaps would help it mix a bit better when it first enters the swirl chamber since it will be slightly thinner from being hotter so I would image the molecules are a bit more excited.  But to gain some huge mpg or power increase I am doubtful.  It's always possible tho. It's just that diesels don't work like fuel injected or carbed gassers the adiabetic ideas don't really apply when the fuel is I jected at the time of combustion

[R.O.R-2.0]

15psi would be over a little twice the air that an na engine would be getting.  But I agree the only difference heated fuel may make would be in how it flows in the pump and injectors which probably effects timing and such and perhaps would help it mix a bit better when it first enters the swirl chamber since it will be slightly thinner from being hotter so I would image the molecules are a bit more excited.  But to gain some huge mpg or power increase I am doubtful.  It's always possible tho. It's just that diesels don't work like fuel injected or carbed gassers the adiabetic ideas don't really apply when the fuel is Injected at the time of combustion

the fuel being injected CREATES combustion...

[81 vw pu]

I was just reading in my Bently and it states that (At maximum compression pressure, the air tempature is forced up to 900 C/1650 F).
I would bet diesel would cook in the lines/injectors at anywhere near that temp, plus your return lines would melt.

[bajacalal]

Aside from the actual engineering caluclations regarding the energy required to heat the quantity of fuel to combustion temperatures, and the fact that you could realistically probably only heat the diesel to 200 degrees which is still a long way from it's flash point, there is the question of whether it's even beneficial to do this...

From my understanding, in a diesel engine, fine droplets of liquid fuel are injected into the cylinder combustion area. These droplets first vaporize (because you can't ignite a liquid) and then ignite under the heat and pressure. In doing so, the droplets travel towards the piston due to expanding gasses as they ignite, and create a flame path with a specific geometry which pushes the piston down in some specific way, part of the function of the prechamber is to direct the combustion accordingly. I think if you were to heat the diesel up to near it's flash point before injecting it, you would have problems because the diesel would basically be igniting too soon, and the combustion would have the wrong "geometry."

[NintendoKD]

In basic terms you are doing the same thing the VO, WVO, WMO, etc. are doing.

That is what I was thinking all along theman53,  We greasers note that the fuel has to be hot to flow like diesel and we note that even when hot it doesn't perform quite the same.  I know I run a few pounds different on hot WVO compared to even warm diesel.  So I do note the timing change and that might be the reason it runs different.  I think it has more to do with the fuel character actually. 

I am not sure we can figure out the extra amount of O 2 in the cylinder compared to native intake.  If boost equals 15 psi how much extra air is that?  15? 

Where is that engineer when you need em. 

They do make wires that you can wrap the delivery lines with that can be heated so if you really wanted to have hotter fuel after the pump and not disturb the other normal settings then there is a possibility for that.  But knowing the fuel sits on those hot injectors long enough to get to engine temp seems like it would do the trick.  How much hotter do you really need to get?  Combustion temps?  Talk about vaporization.  The injectors are designed to deliver a fluid not a vapor.  So best not get it too hot.

pre combustion, and I mean just before, I want to achieve near vapo temps.  The concept is simple, viscosity pre pump is the same, cool the returning fuel and you have something, but the trick is getting just the right temp, and maintaining it.  As well as having dual settings for fuel and timing, could easily be mechanically controlled when desired heat is reached.

[745 turbogreasel]

They say 6.2 injectors don't last as long because of the heat introduced to them by  their proximity to exhaust port.
bajacalal ha s a point, if you have instant ignition as opposed to gradual burn, peak cyinder pressures go up, and you'll have similar results to running gasoline.

[NintendoKD]

Aside from the actual engineering caluclations regarding the energy required to heat the quantity of fuel to combustion temperatures, and the fact that you could realistically probably only heat the diesel to 200 degrees which is still a long way from it's flash point, there is the question of whether it's even beneficial to do this...

From my understanding, in a diesel engine, fine droplets of liquid fuel are injected into the cylinder combustion area. These droplets first vaporize (because you can't ignite a liquid) and then ignite under the heat and pressure. In doing so, the droplets travel towards the piston due to expanding gasses as they ignite, and create a flame path with a specific geometry which pushes the piston down in some specific way, part of the function of the prechamber is to direct the combustion accordingly. I think if you were to heat the diesel up to near it's flash point before injecting it, you would have problems because the diesel would basically be igniting too soon, and the combustion would have the wrong "geometry."

I don't see how, just advance/retard the timing accordingly the fuel will still vaporize, and still burn would it not?  how would this effect eh flame front?  you could be correct though, I have been wrong before, this is exactly why I brought this up, and I believe that this is a VERY important subject and nothing like giving birth control to lesbians.  I think that this is exactly the thing that no one has focused/put enough focus into.  I truly believe that unlocking the secrets of the diesel process impinges upon just this, I mean the principle of operation even says so right???

[NintendoKD]

They say 6.2 injectors don't last as long because of the heat introduced to them by  their proximity to exhaust port.
bajacalal ha s a point, if you have instant ignition as opposed to gradual burn, peak cyinder pressures go up, and you'll have similar results to running gasoline.

called heat management, I have some ideas on this exact subject.  In fact, I am building a 6.5 right now.  I get it, no one here can think of a way to do it, but I am asking "IF" you could what would be the result, good? bad? better? why?  I have a plan, and some very unique designs that I want to try, but before I put all of the effort into it, I would like some real world engineering advice.  Win or lose, you guys are the best.  you want it to be hot enough to not burn/vaporize prematurely, not hot enough to screw the return lines "easy solution there, use different lines" have to adjust timing, and fuel rates, cant have hot fuel prior to IP got it, anything else I can't do?  fuel temperature is very important, from everything everyone is telling me, but what temp gives the best performance?  someone said tdi fuel temp is a good place to start.

thanks bunches, hopefully this will be a sticky one day to help the new guys coming into this, I have learned a ton here so far.

[theman53]

In basic terms you are doing the same thing the VO, WVO, WMO, etc. are doing.

That is what I was thinking all along theman53,  We greasers note that the fuel has to be hot to flow like diesel and we note that even when hot it doesn't perform quite the same.  I know I run a few pounds different on hot WVO compared to even warm diesel.  So I do note the timing change and that might be the reason it runs different.  I think it has more to do with the fuel character actually. 

I am not sure we can figure out the extra amount of O 2 in the cylinder compared to native intake.  If boost equals 15 psi how much extra air is that?  15? 

Where is that engineer when you need em. 

They do make wires that you can wrap the delivery lines with that can be heated so if you really wanted to have hotter fuel after the pump and not disturb the other normal settings then there is a possibility for that.  But knowing the fuel sits on those hot injectors long enough to get to engine temp seems like it would do the trick.  How much hotter do you really need to get?  Combustion temps?  Talk about vaporization.  The injectors are designed to deliver a fluid not a vapor.  So best not get it too hot.

pre combustion, and I mean just before, I want to achieve near vapo temps.  The concept is simple, viscosity pre pump is the same, cool the returning fuel and you have something, but the trick is getting just the right temp, and maintaining it.  As well as having dual settings for fuel and timing, could easily be mechanically controlled when desired heat is reached.

If you just try to heat the injector nozzle the heat will radiate into the body, which will heat the fuel in the return lines, tank, filter, pump...hence the comment of "same thing the alternative fuel guys are doing" If you are only heating it to 200F or so then I can see no benefit coming out of this. One could play with the breaking pressure of injectors and the timing of the pump to get better gains. How do you propose to have dual timing settings easily mechanically controlled?
 
While I appriciate your wanting to think outside the box but this is pointless. This will be as your steel head thread or newly designed precups both of which never got off the ground. It is good to offer a what if, but you seem to be defending something you don't even know is possible. Plus you are looking at .1% of the injection time with tunnel vision and there is a ton more that could be looked at. Port Velocity is easier to achieve by porting the head and precups and with a flow bench you could get your optimum atomization without adding a heater that would probably take more energy to run than any gain you will ever see from it. Instead of not building an engine to show us and going for the home run of fusion or something, why not take some baby steps and get into one of these engines. Tackle some port work or your steel head or newly designed precups? It is just a suggestion, but I think you are on step 6,053 in you head, but haven't started the project yet.