Plantoil/diesel conversion basics
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danalinscott

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Reply with quote  #1 


Accurate chart of the

These are the links to the referrence material used to produce the chart which clearly shows how hot svo/wvo must be warmed to before it is equal to the viscosity of diesel fuel.
Please feel free to check its' accuracy.

http://www.biomatnet.org/secure/Fair/F484.htm

http://www.canola-council.org/...6/chemical1-6_1.html

http://www.schroederindustries...iscosity%20chart.pdf

http://www.engineeringtoolbox....viscosity-d_397.html

http://www.nrel.gov/docs/fy03osti/31460.pdf


http://www.brevardbiodiesel.org/viscosity.html


http://www.biomatnet.org/secure/Fair/S484.htm

http://www.microhydraulics.com...0654b3a?OpenDocument


Inaccurate chart showing the


Chart showing the minimum  temperature that SVO must be to have a viscosity equal to diesel fuel when it enters the fuel injectors:



Frybrid chart superimposed on the accurrate chart







 



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danalinscott

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Reply with quote  #2 
A collection of the questions posed in the the discussion on this subject on the GreaseCar forum so far...and possible answers.

Quote:
Does target temp mean optimal temp?


More precisely it means the minimum temperature to provide the viscosity at which VO combusts as optimally as diesel fuel does.

Quote:
are you getting this information yourself, or are you basing the differences in vegetable oil between multiple sources and multiple testing setups? 
 


The information used to create this temp/viscosity chart is available to anyone via the internet and is linked to in the OP of this discussion. The data is from reputable sources and in most cases has been "double checked" using more than one independent source. The VO temp viscosity values are for fresh VO (Rapeseed/Canola and Soybean). Used fryer oil is likely slightly more viscous as is WVO with high animal fat content. This is why the target temp is considered a minimum temp for optimal WVO combustion.

Quote:
are you showing proof of engine degradation, or poorer running conditions at anything below this?


No..though evidence that plant oil based fuels which have a higher viscosity than diesel fuel cause more rapid engine degradation does exist.
quote:
Kinematic viscosity of an oil is its resistance to flow at a specific temperature. The viscosity of a fuel decreases with increasing temperature. The viscosity of the fuel at the injectors has to be within the limits prescribed by the engine manufacturers. Incorrect viscosity at the injectors may lead to poor combustion, deposit formation and energy loss.

http://www.fammllc.com/famm/fuel_guide_to_quality.asp


quote:
Why are vegetable oils transesterified to produce biodiesel? This question will mainly be dealt
with in other parts of the course(s), but briefly, vegetable oil methyl esters have lower viscosities
(resistance to flow of a liquid) than the parent vegetable oils (think of honey or syrup, which
have high viscosities and flow with difficulty, vs. water or milk, which have low viscosities and
flow easily). Compared to the viscosities of the parent vegetable oils, the viscosities of vegetable
oil methyl esters are much closer to that of petrodiesel. High viscosity causes operational
problems in a diesel engine such as poor quality fuel injection and the formation of deposits.

http://www.biodiesel.org/resou.../20040701-gen369.pdf

So even B25 (25% biodiesel) is deemed to be too viscous (by engine manufacturers) for optimum combustion when injected at the same temp as petrodiesel.
http://www.enginemanufacturers...brary/upload/924.pdf

quote:
Kinematic viscosity affects injector lubrication and fuel atomization.
Biodiesel fuel blends generally have improved lubricity; however, their higher viscosity levels
tend to form larger droplets on injection which, can cause poor combustion


Certainly VO is not exempt from the viscosity problems linked to   higher than diesel fuel viscosity.

Quote:
Any info on how engine components will react to 250 degree fuel temps?


IPs are cooled by the fuel passing through them and as a rule are not engineered to operate at temps higher than 150°F. Injectors are engineered to operate at temps in excess of 250°F.

Quote:
My question is what best prepares WVO for optimal use as a replacement for #2 diesel? In other words if it is true that WVO needs to be 250 deg. F to get the viscosity of #2 diesel does that really tell us anything about how it will burn and drive the engine? Again, is matching the viscosity of #2 diesel the holy grail of making WVO a safe and optimal replacement for #2?


It appears that 230°F is the minimum pre-injection temp for VO. WVO has a slightly higher minimum optimal injectioon temp due to its' slightly higher viscosity.
Please refer to the links provided earlier in this discussion for verifying data/research reports.

Quote:
It also makes you ask, "At what point do you want your WVO @ 250F? At the IP? At the injectors?


At the injectors. 250°F is hotter than IPs are designed to operated at.

Quote:
If the engines are running well on VO at lower temps with no drop in performance and no ill effects to the engine then obviously 250F is not "optimal".


There does not appear to be any research that indicates diesel engines using VO at lower temps operate at the same performance as they do on petrodiesel and experience no ill effects. But there appears to be quite a bit of research that indicates the reverse.  Unsubstantiated claims of conversion kit vendors to the contrary does not constitute valid research..and certainly cannot be considered "proof" that might contradict formal research.

Quote:
What we really need is an advanced research facility, some MB, VW, Chevy, cummins, Ford, etc diesel engines and a few years to operate them on WVO at various temps measuring exhaust btu's, spray patterns (atomization) and its effect on the engine hardware itself, including pumps and injectors, cylinders and any other piece of hardware that comes into contact with WVO, pre and post combustion.


Much of that type of advanced research has been done by engine manufacturers. Understandably the data was expensive to collect and so is not in the public domain. Engine manufacturers HAVE individually collected enough data on this to collectivly agree that fuels or fuel blends with a viscosity higher than that of the fuel which the engines/IPs. and injectors were designed for (petrodiesel)

quote:

Kinematic viscosity affects injector lubrication and fuel atomization.
Biodiesel fuel blends generally have improved lubricity; however, their higher viscosity levels
tend to form larger droplets on injection which, can cause poor combustion
 
quote:
Research shows that vegetable oil
or greases used in CI engines at levels as low as 10% to 20%, can cause long-term engine
deposits, ring sticking, lube oil gelling, and other maintenance problems and can reduce
engine life. These problems are caused mostly by the greater viscosity, or thickness, of
the raw oils (around 40 mm2/s) compared to that of the diesel fuel for which the engines
and injectors were designed (between 1.3 and 4.1 mm2/s). To avoid viscosity-related
problems, vegetable oils and other feedstocks are converted into biodiesel. Through the
process of converting vegetable oil or greases to biodiesel, we reduce viscosity of the fuel
to values similar to conventional diesel fuel ( viscosity isalues are typically between 4 and
5 mm2/s). The maximum viscosity is limited by the design of engine fuel injection systems. Higher viscosity fuels can cause poor fuel combustion that leads to deposit formation as well as higher incylinder penetration of the fuel spray which can result in elevated engine oil dilution with fuel.
 
Quote:
The way I read that chart... At 170 F, WVO is the same viscosity as diesel at 15 F. Since my car will run fine on 15 degree diesel, it should also run fine on 170 degree WVO.
 
While your cars engine may "run fine" it will not run optimally on either diesel fuel at 15°F or WVO at 170°F.  This means that it will produce less power, use more fuel, create more pollution, and have a shorter useful life.
 
Quote:
More heat means more possibility of poly. So maybe the fuel atomizes a bit better, but if you throw a clot into an injector..
 
Polymerization is a relativly slow process at these temperatures and it is unlikely that a clot of "poly" will form where it can foul an injector. Purging the IP, injectors, and injector lines of VO when shutting down nearly eliminates the possibility that oil will polymerize in those areas.  This is only true for two tank conversions. Polymerization in injectors is not uncommon in single tank conversions..but there is no evidence that higher pre IP fuel temps would effect this in any way.
 
Quote:
maybe 230 degree grease is better then 170. but who cares. if you keep a car/truck for 5 years and drive it 200,000 veggie miles it is time to get another one.
 
Unfortunately the verifiable reports of 200,000 miles on veggie before the development of major engine problems are few. This information  may only be significant to those that are interested in lowering emissions, improving fuel mileage, and (especially) obtaining maximum engine life. The diesel engines I work with are often overhauled at 800,000+ miles. This is not a possibility if major problems appear at 200K.
 
 
 


 
 
 








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Dana danalinscott@yahoo.com
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Reply with quote  #3 
A collection of the questions posed in the the discussion on this subject on the Infopop forum so far...and possible answers.

Quote:
Thanks for doing this work and posting the info, Dana. Some recently posted research also points out the importance of injection pressure (and injection timing) as an equally important part of getting the most complete combustion possible from VO in a diesel.


Changing the injection timing, injection pressure, and modifiying the injectors themselves have all been resesarched as a way of overcoming the obvious problem of trying to obtain optimum combustion of VO fuel in engines designed to use petrodiesel.  The two main advantage of accomplishing this via warming VO to the point where it matches the viscosity of petrodiesel is that eating elements are extremely simple technology that allow the two fuels both combust optimumly in the same engine. The technology to change the injection timing of an engine to optimally use diesel fuel OR VO  is extremely complex and expensive. In the case of using modified injectors to optimally atomize VO it is not possible to switch back and forth. Some research is currently being done on adapting the programming of computer controlled multi pulse (peizo) injectors so they can be switch from one fuel to the other..but this technology is still in its' early stages and will not likely be adaptable to exising diesel engines. If it is the cost will be prohibitive.

Quote:
I'd always wondered whether VO viscosity could ever match diesel. I had my suspicions given how Frybrid published a version of that chart with the bottom redacted.


Quote:
I'd always wondered whether VO viscosity could ever match diesel. I had my suspicions given how Frybrid published a version of that chart with the bottom redacted.


Clearly the viscosity of VO CAN match that of diesel fuel at the injectors though the "Frybrid chart" implies that it cannot.

The chart/graph I created was based on the Frybrid chart FORMAT but is not based on the (incorrect) information provided by that chart. I expanded it to allow the complete curves to be shown out to the temps and viscosity I found data for.  AFAIK Frybrid did not "redact" anything from an existing chart. I believe that they created that chart but unfortunately used very faulty data to do so.

Quote:
How does one get the VO that hot without affecting the normal diesel fuel functions?


It is possible to raise the temp of VO as high as practical prior to the IP using an FPHE (usually around 150F-160F) and then using high efficiency Injector Line Heaters and high temp insulation on the injector lines raise it as close to 250F as possible. 

Quote:
what other issues might be created by heating the oil to this level on a longer term basis?

Will it cause problems for injection pumps, seals, computers that make fuel injection calculations with fuel temp. as one parameter, etc.?


Injection pump components will not be effected unless the attempt is made to raise VO temps to temps higher than 150°F prior to passing through the IP. This is not reccomended.  Computerized injection systems are not programmed for VO at any temperature and may be confused if sensors indicate that fuel temps are higher than "normal" for diesel fuel.  Many are discovering that computerized injection systems will not work well with VO at temps as low as 160°F and that some even depend on the fuel to provide adequate cooling for long term useful life.  For VO to be used in diesels with computerized injection systems the systems must be modified and alternate computer programming provided. There is currently very little publicly available informationon this. Currently all of the conversion kits offerred for diesel engines with computerized injection appear to be extremely experimental and as a result engine failures of these conversions are being reported .   

Quote:
coolant heating alone is not sufficient - many coolant-only SVO systems operate, sub-optimally, in the 50-60C range. I think that is not good for emissions or for the longer term health of the engine. Coolant+electric works best to ensure adequate preheating of the fuel.


The available research would appear to support that position.

Quote:
What is done with return fuel, incidentally, if it is heated to 230F+?


It is either cooled and looped back to mix wth the cooler "fresh from the tank" VO or cooled and returned to the tank.

Quote:
since most VO users are operating just fine near 170F, that much more testing is needed before recommending people raise that to 230F and higher.
 

There is no way to verify the assumption that "most VO users are operating just fine near 170F".  Of course the parameter "just fine" would have to be defeined in order to respond accurately.  Many are satisfied with engine life that allows them to recoup more in fuel savings than the cost of a new engine (or replacement vehicle) and the costs of conversion and fuel processing.  For those individuals the benefits of longer engine life, higher MPG, and lower emmissions of pollutants may not be considered sufficiently desireable to incorporate conversion components which provide them.  There have always been a considerable number of individuals who subscribe to this "good enough" philosophy when conveting diesel engiens to VO. I suspect there always will be. But for those who DO value those benefits I believe this information ..and the easy to comprehend manner a chart presents it..will be useful.

Quote:
I've concluded that blends of diesel, with VO and/or BD can achieve clean burning without elevated fuel temperatures possibly needed with 100% VO. The tailpipe emission tests on my vehicle support that conclusion.

Besides, with my truck's fuel system, the fuel resides in the hot injector body prior to injection and I suspect that it's very close to the 230°F 'optimum' when it's injected into the hot combustion chamber.



Unfortunately all of the available research contradicts those two conclusions and I am unable to find any which supports them.

BTW...there is a private discusson group that has access to a substantial archive of VO fuel  studies.
If anyone wishes to join it (and in doing so get access to it's "lending library" which includes most of the studies done in the past 30 years on VO fuel) just email me. I will be happy to sponsor individuals I believe that the current members will approve. As a member I can sponsor up to 3 individuals per year. I have two sponsorships remaining for 2009.

Quote:

quote:

What about the undesirable side effects of running diesel fuel in an engine on which the timing has been advance 2-4 degrees past what is recommended for diesel fuel injection?



Quote:
Its a trade off, you want to optimize it for the fuel you use most, in my case its VO about 90% of the time, so I optimize for VO. 2-4 is such a small amount that you will probably not notice any side effects on D2. If you go beyond this amount of advance, you will see:
Decrease exhaust temperature
Increase cylinder temperatures/pressures
Increase fuel economy
Increase your output of NOx (a pollutant)
Decrease your output of Hydrocarbons (a pollutant)
Increase the amount of black smoke at peak torque
I wouldn't consider all of these to be bad side effects, some are very good.


It is an unneccesary "trade off".
If you can optimise VO fuel to match diesels vsscosity no timing change is neccesary for the engine to be optimized for BOTH fuels. In this way you can obtain the "good effects" of advancing the injection timing..without the bad ones.

Quote:
Dana has stated that:


“As the ACREVO study CLEARLY shows the slower combustion of VO fuel (compared to diesel fuel) is due to the tendecy of VO to not disperse into droplets as fine as diesel does.”

Interesting conclusion. Here is what the authors of the study actually say:


"The study was reduced to atmospheric pressures, since this is the condition generally used use for this kind of injector (industrial furnaces for example). For Diesel sprays, the exact influence of the complex processes involved in liquid jet break up are not yet sufficiently known. Hence, the exploitation of the results was necessarily more elementary."

(In other words, they had to simplify it, and err on the side of caution, not having, at that time, the large number of converted engines operating successfully long term, not having emissions tests that showed good emissions reductions, etc., available, and needing to make some sort of recommendations. )
Quote:
Here is another famous and oft-cited quote from ACREVO:

"Due to this stability with the temperature it is possible to preheat the oil up to 150°C where it attains the same viscosity as the diesel oil. Atomisation tests showed that at 150°C the performance of the rapeseed oil are comparable with that of the diesel oil."

Nice. But it seemed this was done, as they state earlier in the document, at atmospheric pressure.


Correct...later research (some of which is linked to in the above posts) determined that this was the case in the conditions present in the combustion chambers of diesel engines. This conclusion of the ACREVO study was in that way verified.

Quote:
I think that it places too much faith in the ACREVO study to use it as a main pillar for the argument that fuel temperatures of higher than 80C or perhaps 90C at most are necessary.


I agree. This is why I have provided links to several other more recent research reports.

Quote:
Does 250*F SVO work significantly better than 80*C SVO? We don't know, it's all speculation at that point.    We have no way to know for sure until a peer-reviewed study gets published and then gets replicated multiple times by other researchers to verify the results.


Actually there is quite a bit of evidence that VO combusts better at higher pre-injection temperatures. At least up to the point where final injection temperatures of VO allow its viscosity to match that of diesel fuel. All of the available research indicates that when VOs viscosity matches that of diesel fuel it is dispersed into droplets nearly identical to diesels and therefor combusts nearly as comletely as diesel fuel does.
When the viscosity is higher than that of diesel fuel the droplet size and dispersion are not sufficine tto allow this. If this research did not exist the conclusions being presented would be "all speculation". However this is not the case. The conclusions are not based on speculation. They are in fact based on research by independent researchers.

Quote:
As a full-time diesel mechanic and long time installer of SVO systems (since 2000), it's clear to me that the viscosity of the fuel is perhaps the most important piece of the SVO puzzle, and ideally this should be as close to that of diesel fuel. What temperature that happens at I don't really know to be honest, but I'm sure it's not a simple single number and instead depends on a bunch of variables such as: oil type, iodine #, etc.
 

The available data supports your conclusion that "the viscosity of the fuel is perhaps the most important piece of the SVO puzzle, and ideally this should be as close to that of diesel fuel."  I am however aware of no data or research I am aware of that indicates oil type, iodine #, etc makes any difference in combustion of VO at temps above 250°F.

Quote:
As far as the efficacy of SVO temps in excess of say 90*C, one thing to note is that although the viscosity may approach that of diesel fuel, and combustion MAY be better, diesel injection pumps do not like to be heated as a rule, and to be heated over 200*F may lead to premature failure of the IP (and by premature I mean maybe failure after 100k miles instead of 300k or something along those lines). Diesel technology engineers have spent untold hours trying to keep internal IP temps low, and now we come along and introduce significant heat into the IP even at the 80*C level.



I agree.
VO should not be heated above 150°F prior to the injection pump if normal IP useful life is expected.










 



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Dana danalinscott@yahoo.com
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Reply with quote  #4 
High Temperature Reactions:
Life in the Combustion Chamber
As we’ve alluded to a number of times, when vegetable oil fuel first enters
the combustion chamber it undergoes a number of chemical changes that
affect how the oil will combust and burn.
Thermal Cracking and Polymerization
Surprising Results. Research on petroleum-derived fuels showed that
increasing the viscosity of the fuel narrowed the angle of the spray cone
and increased the penetration rate, i.e. the speed at which the spraymoved
away from the injector.40a
However, when researchers studied the spray patterns of vegetable oil
they found something very surprising.As they thinned the oil by heating
it up, the spray pattern did the opposite of what they expected.The spray
of hotter, thinner oil was narrower and had a higher penetration rate than
colder, thicker oil. This pattern held until the oil was heated to all the way
up to 293° F, the maximum test temperature (Fig. 2.11).40.b
Also surprising, the researchers found that the spray pattern of vegetable
oil was nearly identical to petrodiesel when the viscosity of the oil was still
nearly double that of the conventional
fuel. Specifically, oil heated to
285° F with a viscosity of 4.1 centistokes
looked the same as the spray
pattern of unheated petrodiesel that
had a viscosity of 2.4 centistokes at
40° C

http://www.newsociety.com/news...r/News44/svo_ch2.pdf

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