HP fuel line heat-block

[dubbleUJay]

Hi guys,

I've been running my CS for a couple of hours the other day and I noticed that my high pressure side of the fuel line to the injector is cool to the touch. I'm planning on running WVO in the future and know that I'll have to heat this up. (I'm not using the coiled copper tube at the left at the moment as I'm using diesel fuel currently, I tried it, but it got so hot, I'm scared the diesel might ignite or something else might happen!)
Recently I moved my fuel filter to the bottom position next to the pump as I fitted an engine mounted diesel tank.
The area on the head were the filter was removed from was very hot so that got me thinking:


Will a big copper block with small ID ports drilled into it as to make a zig-zag like tube through it, not significantly or partly heat the WVO fuel up to an exceptable level?
I will be heating it up with a loop around the exhaust pipe before the pump as well, I'm just trying to get away from using electrical means of heating it before the injector or to use minimal elec. heat to get it up to temp. just before the injector.
I'm just worried that the block might work in reverse, rather cooling the WVO to head temperature than heating it up more!

I have no idea what the temp of the WVO will be just after the pump, maybe someone has experience with this before I start making stuff?
At the moment I'm running on diesel fuel, would it not benefit fuel consumption from being heated before going int the injector?

A lot of questions guys, thanks in advance.

[compig]

Why not make a small heat exchanger to install into a coolant hose ?  Coolant temperature should be adequate for heating WVO.

[AdeV73]

I'm not using the coiled copper tube at the left at the moment as I'm using diesel fuel currently, I tried it, but it got so hot, I'm scared the diesel might ignite or something else might happen!)

Diesel will auto-ignite at around 210 degrees C (410F approx), if Wikipedia is to be believed (see: Examples of flash points section). However, that's an open air/fuel mixture, rather than a closed fuel line.

WRT the copper block - it's certainly  true that, until the head got up to temperature, you'd be cooling the VO going through the pipe, if it was previously heated. It might be useful to consider having two heat sources on your HP pipe: The copper block first, and an electric heater second (and separate); so you can run from cold on VO by using the electric heater to preheat the fuel; this switches off when the head reaches sufficient temperature for the copper block to do the work.

The one thing I'm not sure of (and any veg oil burners will know this) - do you need to pre-heat the fuel before the delivery pump, or is that able to work with viscous fuel?

[compig]

WVO does preferably need to be heated before the injector pump and delivery pump if relevant.

[AdeV73]

WVO does preferably need to be heated before the injector pump and delivery pump if relevant.

My bad, by "delivery pump" I meant "injector pump"; only now occurs to me that "delivery pump" is more likely to be a lift pump....

My setup will be gravity fed, but I was hoping to start & stop on veg oil, without any of this flushing the lines with diesel. So I'll need to preheat the fuel from cold, right up by the injector ideally. I was hoping I wouldn't need to preheat down by the injector pump as well, but I don't suppose there's any harm in doing so.

[Combustor]

          Hi there AdeV,
                              Pleased to hear you are considering using WVO. It can be a whole new ballgame, but there is a lot of good info out there from those who
          have perfected the art (It's certainly not a science yet). Just too many variables, source and quality of oil, cleanliness, amounts of suspended water,etc.
          A successful system is usually a 2 tank setup with diesel or Bio for starting and attaining working heat. It hardly matters how much preheat is applied to oil
          if you send it to a cool injector in a cool head as the oil is only injected in tiny amounts and soon loses heat to the far greater engine mass. Many oils need
          to attain round 60c to equal the viscosity of cold (say 5c) diesel which the pump can handle, and the head and injector need round 80c to atomise oil for
          reasonably clean burning.
                   There is some info on this site under "Alternative Fuels", or do a Google search on veg oil fuels etc. Biodiesel Infopop and Burnveg.com are among
          many good sites. Look at the blended fuel topics on these sites also. It can be a good alternative depending on what is available to you. Best of luck,
                                                                                                                                                                                   Regards,  Combustor.

[compig]

WVO does preferably need to be heated before the injector pump and delivery pump if relevant.

My bad, by "delivery pump" I meant "injector pump"; only now occurs to me that "delivery pump" is more likely to be a lift pump....

My setup will be gravity fed, but I was hoping to start & stop on veg oil, without any of this flushing the lines with diesel. So I'll need to preheat the fuel from cold, right up by the injector ideally. I was hoping I wouldn't need to preheat down by the injector pump as well, but I don't suppose there's any harm in doing so.

Problem with WVO is the much higher viscosity. This causes more stress on the injector pump and inferior spray pattern on the injector. Thats why an exhaust heat exchanger before the filter is a good idea. The exhaust heats rapidly from start up so heating the WVO as quickly as possible.

[dubbleUJay]

Thanks for the suggestions thus far guys:

compig: I considered a water heat exchanger, but the copper/brass block seems to be easier to make and mount.
(Its also in the path to the injector and mounting a temp. sensor seems easy. That said, it depends if I can get such a piece of brass at a reasonable price!)

AdeV: Thanks for the Wiki info. Something else I was also worried about was a droplet of water in the fuel that might turn to steam and rupture the copper piping, there's no expansion chamber in my setup as I didn't thought of it at the time. I think the back pressure of the fuel to the tank in the pipe might not give way to a sudden pressure increase and my piping's ID is quite thin as well!
I will use the exhaust heat to pre-heat before the filter with a coil as on the pic above, who knows, it might be enough to keep it up to temp. right up to the injector, but I doubt it.
I'm planning on using a secondary heat source just before the injector in conjunction with the heatblock or heat exchanger for that matter, but only to get it up to the right temp. It's just my reckoning that the heat on the side of the head is free and I'll use much less power to just heat a few degrees than a big temperature swing.

Combustor: I'm planning on starting & stopping on diesel as you suggested, I also cannot see any other reliable way (Yet ;-) of just running on WVO alone.

Something else that bothers me (I'm sure the diesel-heads could help me here)  is the size of the holes in the copper block to house the fuel. I presume I should try and mimic the existing delivery pipe, but if the ID of the holes/channel are to big, would it not act as a reservoir and have a "springy" or damping effect on the delivery of the fuel to the injector?
Or can the fuel not be compressed to a level where it will influence the system?
I'm asking this because if not, I can just use a non-expandable hollow block, but I think not, common sense tells me it doesn't seem right!

dubbleUJay

[compig]

Fluids are for all practical considerations incompressible. Not an issue so don't worry about it. However , if you make the bore thru the block much larger than the delivery pipe you may have air-locking issues and problems bleeding the fuel line.

[dubbleUJay]

Fluids are for all practical considerations incompressible. Not an issue so don't worry about it. However , if you make the bore thru the block much larger than the delivery pipe you may have air-locking issues and problems bleeding the fuel line.

compig, thanks for reminding me about airlocks! I'll then drill the holes at an angle so that a high point is created with a bleeding nipple at that point if I do go this way.

On the other hand, considering what you said about fluid, would it then be practical to use a hollow brass block with the one side open and gasket-ted directly to the head? This will put the fuel in direct contact with the head surface for quick heating, but will a homemade gasket/O-ring hold under those pressures?

[compig]

That could be tricky to seal at injection pressure , an O ring would definitely stand a better chance than a gasket. To make it worthwhile there would need to be as large an area of fuel as possible exposed to the head so the o ring would have a large surface exposed to the pressure which increases the load it has to seal.

[AdeV73]

Hm; I think I'd machine my copper/brass block in two halves. I'd use a ball-end cutter to mill out an appropriate path, then I'd bend some HP fuel line to fit the path. This then gets sandwiched between the two halves of the block (a nice tight fit will aid heat transfer from copper block to steel pipe) & bolted to the side of the Lister. That way I don't have to worry about bleeding a copper block, o-rings, connectors, etc. etc.; all I have to do is bend the fuel line tight enough, and I bet that's easily enough done, with some heat.

[compig]

There would be a temperature gradiant from the engine to the copper block and from there to the tube though.

[dubbleUJay]

OK guys, after all your great input, this is what I came up with:



I might change the IN and OUT once I start making it, depending on the thickness of the brass I can get, but the basic idea is there I think ;-)

Does this look like something that might work?
and
can someone tell me if pre-heating diesel fuel by itself has any benifit as well on an engine like this? (I remember reading something about it a long time ago)

Any input is greatly appreciated guys, thanks.

[compig]

Diesel pre-heating is appropriate for good running from cold but otherwise there would be no advantage. Your layout is more or less how I saw it in my minds eye.