dual fuel concept

[mobile_bob]

i think we can all theorize how this works, based on our own separate experiences and what we individually have been taught
one thing for sure is i was taught not to ever use gasoline in any quantity in a diesel engine, so when i find reference to folks doing
so i am automatically suspect.

so color me heavily skeptical, but

i was also very skeptical about a clawpole alternator being able to run at 80% efficiency, and figured to just accept the 50% efficiency operation
as a fact of life, until i came across the MIT paper. having read that i was still skeptical and decided to start doing my own research, and guess what?

they were right! and i too could replicate what it is they were seeing, and because of that many more of us can benefit from how it is done.

now along comes the university of wisconsin report and the SAE accepted paper, so... i am inclined to give it enough benefit of the doubt to not
summarily dismiss their work, but rather see if i can duplicate the process and get "any" improvement in efficiency.

if it shows any promise, then i will delve into it more deeply because of the emission being more compatible with a cat converter. if for no other reason if it helps in PM filter efficacy it would be useful for what my goals are.

i know my s195 idi changfa is darn close to 32% thermal efficiency (btu's to crankshaft hp), and i can measure whether this increases, decrease or stays the same to withing a gram or two per kwatt/hr produced. so it will be very easy to determine whether there is any benefit to this process
as i understand it and as i can replicate it.

i am kind of anxious to get this thing in operation

bob g

[veggie]

jimmason,

Thanks for that clear explanation of detonation vs. fumigation saturation point.
Any thoughts (or experience) with Natural Gas.?
A few members have experimented with NG fumigation and noted very good reductions in diesel fuel consumption.
If the NG enables more complete combustion AND a reduction in diesel fuel consumption, it too may be a worthwhile option for "combined fuel" systems.
Any thoughts?

cheers,
veggie

[jimmason]

i've never done it with natural gas.  but my understanding is it performs similarly to woodgas.  ch4, co and h2 have quite similar autoignition temperatures thus simiiar detonation characteristics.  all will run at higher compressions that propane, which will run at higher compression than gasoline.  a natural gas or wood gas engine is set up about the same cr wise as a methanol race engine.

dual fueling a diesel with natural gas will give you an extremely clean burn.  the only fuel that will give you a cleaner burn is co and h2, but the difference is minimal.  very simple atom fuels like ch4, co and h2 eliminate all the interim combustion steps where the fuel is pyrolysing and generally breaking into progressively smaller molecules before taking the o2 to the end states of co2 and h2o.  yes, there are many radicals in this progression, but in general, we can summarize that the bigger and more complicated the fuel molecule you start with, the more transformations needed before you get to the end of combustion.  the longer and more complicated htis process, the more of it that will not make it.  thus the basic challenge of diesel fuel.  diesel is in the range of c12h24.  it is a big molecule.

the main issue with dual fueling small engines is the control difficulties.  i've dual fueled both a 6/1 lister and a changfa 195, but in both cases the control is touchy.  you are already using such a small amount of diesel on these rigs, that to drop it down to 10% or so, then put the control and governor on the gas portion, is difficult and unstable.  i often ended up not being able to maintain proper speed at low load.  as in i couldn't keep the diesel low enough and still metering accurately.  it was easy to produce an overspeed situation.  this is particularly unfun on a flywheel engine. 

at this point of complication, it was easier to convert to spark ignition.  this is easy on the lister, as you see in the work on the other thread.  we recently tore down a changfa 195 to see if we could do the same.  turns out no.  the injector we know is very narrow and we thought we could just machine out its hole.  unfortunately the valves are very big in the changfa, and the injector is directly in the middle.  you can't make the hole bigger without violating the valve seats.  one either needs to make a custom small spark plug, or machine a whole new hole in somewhere else in the head.  neither of which seem very fun.

if anyone is interested in these conversions, there is going to be another lister spark conversion this coming weekend by the flatlander wood gas gang in michigan, led by mike anthony.  the announcement about their workshop is here: http://gekgasifier.com/forums/showthread.php?t=378

a few weeks later we're having our next quarterly gasification workshop at the libertarian treefort within the midst of the people's republic of berkeley (aka: all power labs).  we might take on the changfa spark conversion for this, but more likely doing data logged endurance runs of our gasifier genset rig.  info on the workshop is here: http://gekgasifier.com/forums/showthread.php?t=348

i've found there is nothing that better unfolds the scrolls of combustion science and its related heat engines, than diving head first into the gasification hole.  one realizes very quickly that gasification is the operating system of fire.  understand it and engines become somewhat of a subset application of a more general description of fuels and their transformations.

here's my attempt to explain the basics of gasification, and why it is so interesting: http://www.gekgasifier.com/gasification-basics/  click on the "how it works" after the intro for the basic science.  beware of the black goo that might soon suck you in. . .

j

[jimmason]

bob,

it sounds like your main motivation here is to clean up diesel exhaust so you don't foul a heat exchanger.  if so, you might try some light steam fumigation of the diesel air intake. 

steam is a highly effective cracking agent of hydrocarbons when at high temp.  it also helps complete co conversion to co2, via the water gas shift, which gives you more h2, which burns quickly thereafter.  it also lowers combustion temp so nox is reduced.  steam into a diesel is a very good way to reduce soot and increase the full conversion of the diesel.  there are many papers on all this which you can find on a search.

the other thing you might consider is trying dolomite bed as a cat cracker.  dolomite is the poor man's diy cat in the wood gas world for tar cracking.  many of the cat pathways are relevant for dirty diesel exhaust too.  dolomite is near free so if replacement is needed from fouling, there is little crying about it.

you will likely need to have it in the 600C and above range to do much, so it would need to be right at the exhaust manifold.  you can support it in a canister or in a fluidization section.  you want to use little 1/8" or so pebbles of it. 

j

[mobile_bob]

i already have a prototype exhaust heat exchanger that requires no cleaning, so that is not my concern

my concern relates to epa compliance, like it or not we have to start being forward thinking rather than simply staying with
the status quo

there are a finite number of suitable existing preban engine's, and with each passing year there will continue to be an increasing demand
or a diminishing supply of those engines.  that leaves two choices

get with the friggin program and ahead of the curve, or

pay 4 or 5 grand for a 12hp engine that is compliant

we can continue to play around with veggie oils, waster motor oils, wood gas and thats ok by me, but in reality it is not responsible operation
in the long run.

we have to lead by example, that is the the foundation on which this forum was born, and i will continue to do my part to build on that.

i don't expect there to be a broad following, that is probably why i am not in politics! 

bob g

[jimmason]

well i agree bob it is responsible and needed to also figure out how to do this legally.  that is why i don't really work with the lister and changfa base anymore except for fun and giggles. 

for replicable work, i'm doing all my woodgas gensets over current legal and supported kohler v-twins and 4cyl nat gas/propane engines.  but again i no longer want the diesel platform.  these are lower end spark industrial solutions that with belting can get to high enough hours for most micro chp projects.  no, it is not a cummins or a cat, but few of us need to optimize here for 24/7/365 decade utility type service.  most of us want daily use of intermittent hour operation.  we like to tell ourselves that the listers and changfas are extreme longevity, but given the variability of china and india diy engine quality, what all of us can really get to longevity wise with these engines is debatable and variable.  none of us really have good info on what happens at 5,000, 10,000, 20,000 hours.  at least with the known lesser burly solutions we can start with consistent bearing quality and critical metal parts of known quality.

the cheapest real longevity diesel engine available in the us is likely an old detroit diesel 2.71.  there are various resellers of them.  if you have money, go the oil pumping world and an old ajax.  there are interesting newer similar engines coming out of argentina, as well as the commercial chp engines like the marathon in the ecopower unit or the kubota in some unit i forget the specifics on.  and of course a new yanmar or kubota is always going to be a great engine.  watch surplus center as they often have recent model new engines for small costs.

if i had time to fight out the sourcing and variability issue, i would personally be trying to source the redstone type engine but with a spark ignition.  or really imported with zero ignition, intake or exhaust.  just the short block and then finish it on this end.  would this pass as a "parts" import that i and/or others could finish on this end to a wood gas engine?  its 15.5:1 cr is about perfect for our needs.  i have not followed the epa import drama that closely in awhile so do not know the specifics at the moment.

given the many variables in the above, i've found a way to happily work with the current legal lower cost engines.  so far i like the kohler's the best.  they go up to 1000cc in air cooled, and 750cc in water cooled.  they are a little above or below 2000 dollars from online sellers.  they have epa, carb and ce ratings, so all is ok with the burgeoning regulatory infrastructure.  kawasaki has a similar impressive line of water cooled v-twins.  i hear harley and buell make some too . . . ;-)

jim

[mobile_bob]

jim:

i commend you on your passion for your gek project, however

this thread is based on "dual fuel concept" where gasoline is injected as the secondary fuel
this is the topic and that is the direction i am sticking with at this time, call it research if you like.

there is nothing about the detroit 71 series you are going to educate me about, the detroit 53, 71, 92 and 149 series and i go
back several decades so i am very familiar with them, they also are not epa compliant and cannot be made to be so.

as for variable quality of a listeroid, ok.. fair point but i would direct you to John F, Jack Belk and a few others that have well over
10k hrs, some upwards of 20k hrs and at least John F at over 26k hours that i know of.  and i am no fan of a listeroid 

you speak of using an epa compliant gas engine for you gasifier work, however you don't address the issue that now once fueled
with wood gas it is no longer epa compliant!  it is only compliant burning unleaded pump gasoline or possibly propane and is only certified
using those fuels.

as for changfa or redstone, i am familiar with both and quite frankly like the 195 series a lot, your point on variable quality is valid, however
most of the issues relate to assembly problems and not poor design or parts quality for the most part.

i digress  (yes i am good at it)

my point is this, the topic is for dual fueling a diesel using gasoline as outlined in the university of wisc SAE paper, and my attempt to replicate their
findings at least to some extent, for obvious reasons of higher efficiency, lower emissions and a cleaner burn. lessons learned could have broad application with other engines we work with here.

i realize that it might not be something that works well with a gasifier fueled engine, but i don't know for sure.

bob g

[rcavictim]

i already have a prototype exhaust heat exchanger that requires no cleaning, so that is not my concern

Yeah yeah yeah .... rub it in why don't you

Steam into the intake port Jens.  You have your answer!

[jimmason]

bob, i thought we were discussing hybrid fuel scenarios as they relate to diesel engines.  this then related to issues of combustion science, and why various fuels will do x or y in a dual fuel scenario.  which led to considerations of the engines available to do as such, and the pros and cons of each, in relation to your concern for figuring out how to do all this legally.  i thought i was adding to this discussion.

either way, i fear these dual fueling scenarios are unlikely to get us/you/me closer to an epa compliance.  such compliance is not an issue of engineering or use scenario.  it is an issue of paperwork applied to a consumer turnkey application.  might as well just redesign the injection system for a changfa and pay to create a new certification.  the hurdle in either is the certification process, not the engineering.

unfortunately we can't take an non-conforming engine then run it in an exotic manner on hack equipment to compliant performance, then claim it compliant.  we could however, remanufacture the engine as an OEM, with a new integrated and non defeatable dual fuel solution, then prove it compliant through money and effort, get the paperwork in order, then resell the result.

buying a current compliant diesel will likely be much cheaper, or at least the same.  a good part of what you are paying for is the paperwork.  add that to a china diesel and we all will be back about where we were.

of course it will be much more interesting than current options.  so either legal or illegal, you should continue.  i for one am very excited to hear what you find with the gasoline fumigation.

j

[veggie]

jimmason,

I think you are correct on the EPA issue.
Even if a person were to get an engine to comply, there are VERY expensive lab tests which must be performed and documented. Once passed, there is an annual maintenance fee for each engine size.
Initial acceptance testing and first year fees can fall in the $20K range per model.
This is a task for a manufacturer, not an individual or small group. The money would never be recouped.

veggie

[mobile_bob]

Jim:

my apologies if i came off too abrupt

perhaps i should state my position, or make my intentions more clear

lacking a better term to describe what i do or rather what i am into, i think the term "experimentalist" fits

some folks climb mountains, because they are there
some folks then jump off mountains, because the want to fly
some folks walk around them, because they don't like heights
and some of us are content just to sit back and admire their beauty...

most of what drives me is the insatiable quest for knowledge and then  "application" of that knowledge.

i have no delusions of creating a tier 4 compliant engine from a changfa, although it is possible to do so, but
that is no reason to accept the engine as is and just use it as is, in my opinion. Especially if there are things we
can do about it, such as operate it under tightly controlled conditions,  fit it with a cat, a PM filter and perhaps
operate it in dual fuel mode.

i have the test equipment available to me to test for all aspects of emissions, 5 gas and opacity so i plan to use it.

you see here is the thing, after 35 years as a diesel mechanic and several more years prior as a gas engine builder
i have had to work within the confines of what the oem's built, i am at a point in my life now where i am no longer
constrained by anything other than the laws of physics, my imagination and of course "realistic" amounts of cash.

to me, finally after all these years to have the ability to do some serious testing, research and development, is about the
most interesting thing i have ever been involved in. the ability to produce a single unit that i know is epa compliant even if not
certified as being so by the epa would be an accomplishment i would take great pride in, personally.

the ability to build a genset based on the 195 that canl compete with major manufactures diesel gensets of the same class
has been an accomplishment that just a few years ago i would not have thought possible, now moving on to microcogeneration
and finding that my unit is very close to being a heads up competitor in efficiency with what the majors are producing has a certain
attraction.

yes i could just sit back and enjoy the view, life would certainly be simpler, but for me it would be unbearably boring.

its the mountain that i just have to climb

not sure if this helps you to understand the drive, and quite frankly some days i am not sure i understand the drive either.

bob g

[rl71459]

Hi All

From following this thread it sounds like my genset (C201 isuzu diesel/ST12) might benefit from the addition of Nat Gas Fumigation in the area of keeping the combustion chambers cleaner.

I remember a thread (Think it was on LEF) that demonstrated a simple system which energized a Nat Gas
valve when the genhead was producing power (a 6-1 roid if I remember correctly). The intake was drilled
& tapped for a fitting that was connected to some appliance flex pipe.

Is their any reason to not attempt this on my rig? will I risk damaging the engine? or will it not have any
favorable results with this engine?

Rob

[jimmason]

Jim:



you see here is the thing, after 35 years as a diesel mechanic and several more years prior as a gas engine builder
i have had to work within the confines of what the oem's built, i am at a point in my life now where i am no longer
constrained by anything other than the laws of physics, my imagination and of course "realistic" amounts of cash.

to me, finally after all these years to have the ability to do some serious testing, research and development, is about the
most interesting thing i have ever been involved in. the ability to produce a single unit that i know is epa compliant even if not
certified as being so by the epa would be an accomplishment i would take great pride in, personally.

the ability to build a genset based on the 195 that canl compete with major manufactures diesel gensets of the same class
has been an accomplishment that just a few years ago i would not have thought possible, now moving on to microcogeneration
and finding that my unit is very close to being a heads up competitor in efficiency with what the majors are producing has a certain
attraction.

bob g

bob,

this is a fabulous goal.  i take great pleasure in doing about the same over in the gasifier world.  "expert engineering of everyday crap" is what i like to call it.  showing that you can built diy equipment that can do what the majors can't (as there aren't really any majors in gasification at the small scale) is, umm, fun.  i enjoy it.  the results exist in a similar netherland of regulatory compliance, thus it is labelled experimental equipment.

i commend your regular use of test results here.  a 5 gas exhaust emissions tester is a great toy to have.  at some point we'll get some daily use gas sensing equipment.  for now most of our inputs relate to temp and pressure.  we developed a board to do this so we can datalog all aspects of the gasifier.  see here for the board: http://gekgasifier.pbworks.com/Gasifier-Control-Unit  this is really relevant for any type of industrial thermal eq process control and datalogging.  it could help you to understand the effect of intake and exhaust temps, air cleaner and exhaust system back pressures, or just controlling a dual fuel scenario.  the beginnings of this can be done very simply with a regular off the shelf arduino board for 50 dollars or so.

the major issue in a regular dual fuel scenario i find to be control.  yes, sending nat gas into the intake is easy and it very much cleans up the exhaust.  but controlling the amounts in relation to some input can get complicated.  again, i had trouble doing this all manually on the lister and changfa.  but maybe the isuzu mentioned is large enough to do it more reasonably. 

if you want to make the nat gas your main fuel, the method is to pin the diesel inject at idle, and disconnect the governor input.  the governor rod is then connected to the nat gas valve in the air intake.  whether this is easy or hard depends on how the governor and injector is set up.  if all this eq is internal, it can be difficult to make work.

either way, it is has always been, and will always be, experimenters that have made the interesting things in the world, which ultimately became the mainstream tech, then often sadly locked down from further play via regulation.  but you can also usually find a way to still play even under the most rigorous regulatory regimes.  for instance, we had the pleasure of running an industrial facility off grid for 6 years in the middle of the city of berkeley california.  the city shut off our power as they didn't like our building code interpretations for shops we built out of recycled shipping containers.  we didn't like their interpretations either, so we fought them politically, legally and in the media, and made our own power to continue operations.  here's the 33kw of inverters and 17,000lbs telcom battery array we built into a shipping container to run the show: http://www.flickr.com/photos/nesdon/sets/72057594062314269/

that's how i ended up in all this.  a youth wasted racing motorcycles, atvs and sand rails helped in the basic tech arena.  but berkeley was the real push.

somehow, all this seemed needed to know a bit about dual fuel . . . ;-)

j

[rcavictim]

bob,
<snip>
...... but you can also usually find a way to still play even under the most rigorous regulatory regimes.  for instance, we had the pleasure of running an industrial facility off grid for 6 years in the middle of the city of berkeley california.  the city shut off our power as they didn't like our building code interpretations for shops we built out of recycled shipping containers.  we didn't like their interpretations either, so we fought them politically, legally and in the media, and made our own power to continue operations.  here's the 33kw of inverters and 17,000lbs telcom battery array we built into a shipping container to run the show: http://www.flickr.com/photos/nesdon/sets/72057594062314269/

that's how i ended up in all this.  a youth wasted racing motorcycles, atvs and sand rails helped in the basic tech arena.  but berkeley was the real push.

somehow, all this seemed needed to know a bit about dual fuel . . . ;-)

j

Jim,

I think you will be a real asset to the group here.  I am very impressed that you and those that you hang with think the same way I tend to do.  That stand you took with the city and the solution you came up with is worth an award of recognition of the highest order.  My hat is off to you!

[veggie]

rl71459 (and others who are interested)

In response to your thoughts about natural gas fumigation and the LEF thread where someone did a conversion....
Rather than divert Mobile_Bob's thread on duel-fuel diesel/gasoline, I started a new thread for NG conversions here...

http://www.microcogen.info/index.php?topic=923.0

veggie