Micro CoGen.

Quote from: mobile_bob on December 31, 2010, 10:41:21 PM

quite frankly i don't know why the gasifier boys haven't worked more with the small diesel in dual fuel mode, aside from the need for a pilot fuel
(diesel) the pros more than offset the cons in my opinion.

here's at least what happened with me.  

in principle, i agree is sounds great.  in practice, i found the dual fuel control on these small engines to be extremely touchy.  it takes such a small amount of liquid to get to no load full rpm, that a minor error in your set liquid amount can lead to an overspeed.   larger engines with larger rpm seem to have more running resistance you need to overcome to get to speed, thus less sensitivity in the liquid set amount.

also, it only really works for the lister, as you can get to the governor linkage and detach it from the injection pump so you can use the gov for your gaseous valve, and pin the injector pump where you want it to hold steady.  on the changfa, it is all internal and you can't easily repurpose the mech gov to control your gaseous fuel, nor easily hold the injection pump in a single place.   doing it the other way (pinning the gaseous portion and varying the diesel) gets into even more problems.

before actual experience, i too thought dual fuel would be the way to go.  that's why i started with the lister and china diesels to make integrated gasifier gensets.  you can see the early lister and china diesel ones here:  http://www.gekgasifier.com/wpgallery/gek-gasifier-genset-older-versions/  it didn't really work that well.  the result was not something a non-expert should ever touch.  also, i just got tired of fighting the variable quality, old engineering and weight issues of the lister-changfa options.  i wasn't finding a total value.  it was not "cheap" in the end.  so then i started on the v-twin route spark, which you can also see above.  then the kubota.  

if one has a good and constant load, all should be fine.  but as soon as you have detached the injection pump and pinned it in some place, you no longer have the certain safety in overspeed that the governor usually provides.   if doing dual fuel with the liquid set for pilot, i would encourage only doing this with a solenoid shutoff that is run in parallel with spark.  don't pin the liquid rack physically to the run point.  put it on a solenoid to the run point, thus when you shut off the ignition, the rack still goes to absolutely shut.  the pilot dual fuel can be sneaky and easily get out of control.  

remember, diesels can run away on crank case bypass oil.  this is why some have intake dampners.  true, not usually needed.  in a dual fuel pilot injection scenario, if a hack injection rack set screw can easily come loose and bad things will follow quickly.

then adding the new butterfly to the above, i was quickly getting into as many or more control issues in dual fuel than with a spark engine.


more reasons.

wood gas tar converions falls apart at low pull rates, as temps fall.  minimizing wood gas use has not been the problem.  at this point i can run down to about 1kwe without external gas dumps and still keep things hot enough, but that was far from the case in the beginning.  dual fueling only made the low end fuel consumption lower, which was the wrong direction to be going.

also, after one has suffered through the pain of getting a wood gas system to work, it is a let down to use any liquid fuel at all.  it is much more pleasurable to run 100% wood gas.  that is the magic.  junk in - -  power out.  it is better undiluted.

all this led to an assessment that there was no "simplicity" and little pleasure to be found in the dual fuel small engine scenario at least for wood gas.

this calculus may change if working with nat gas.  and mileage always varies given your specific context.  i just clearly wasn't working out in mine.

jim

Quote from: TimSR2 on December 31, 2010, 11:15:19 AM

 So putting a lister CS or a changfa on NG or propane is a reasonably straightforward proposition. And they have the mechanical governors we need for electrical production built right in.

Then just get rid of or disconnect the pump(s), Connect the governor to the carburetor throttle lever somehow, stick a sparkplug in the injector hole somehow, pick one that doesn't hit the piston crown.  

interesting coincidence in the universe that otherwise tends to not cooperate:

1. the injector hole size in a standard lister cs head is a perfect fit for a standard automotive long reach spark plug.  you can even repurpose the injector bolt down assembly with a hollow tube to hold down the spark plug.  for those who didn't see the earlier threads, here's our doc on doing so.  http://www.gekgasifier.com/forums/showthread.php?t=312.   (we later did it through the compression adjust plug, so as to retain both the diesel and spark ability at the same time.  you can see that here: http://wiki.gekgasifier.com/w/page/30448258/Spark-conversion-for-Lister-slow-speed-diesel-engines)

2. the injector hole in our local changfa r175 is about perfect to insert a 10mm motorcycle/chainsaw plug.  there are now 10mm and i think 8mm very small spark plugs that make installations in these smaller holes possible.  some engines you can likely even get them in the glow plug holes.  

so in both the lister and changfa case, you can convert to spark without machining or compromising the original motor.  and as tim said, adding gaskets is easier than milling heads and considering new piston clearance issues, on the road to reasonable compression.  

there are many ways to spark the result.  one electronic option using an arduino is explained here: http://wiki.gekgasifier.com/w/page/30448258/Spark-conversion-for-Lister-slow-speed-diesel-engines.  this is ken boak's work.


jim

Quote from: Lloyd on December 29, 2010, 11:12:00 PM
FORD VALENCIA (VSG) engines are currently available in only one model, a 1.3L engine rated at 32.8hp at 2800 rpm. (A limited supply of service replacements for the earlier 1.1L size with a continuous rating of 27.5hp continuous at 2800rpm are still available).  These four cylinder engines are very smooth and exceptionally quiet when compared to most air cooled engines. Either model can be CARB (California Air Resources Board) certified when in equipment requiring less than 25 horsepower and can operate on gasoline, LPG or natural gas.
http://www.powertechengines.com/20_30.html\

wonderful thread here guys.  a very interesting read.  and where did tim come from?  he seems to know everything about engines.  thank you for all the knowleged explored here. 

here below is what i've learning investigating the same.  i too think the fuel hacker future is increasingly in spark vs diesel. 


-----------------------------------------

inline 4s and 3s

sadly, the ford vsg engine is gone.  i wanted to use it for our rig but couldn't make it a regular sourcer.  its still a great engine for a one off, and already set to go with gaseous fuels usually.

the nissan A14 and A15 are similar go to solutions, but they too are no longer available new in the US new.  i tried that too.  lots there used, and they are well proven and loved.  for one offs, a great choice.

the kubota 3cyl 962cc is my current favorite.  they are 3k new, but nearly no used.  the oil field guys report 15k hours and still going on the first prototypes that were put in somewhere in montana.  kubota is making noises about coming out with a bigger one.  so far unseen.

the current gm small industrial spark engines are here:
http://www.gm.com/vehicles/innovation/powertrain-technology/engines/specialized/industrial/industrial_engines.jsp

people seem to frown on the 1.6 and 2.4 4cyl vortecs as having too much plastic and not terribly robust.  (no personal experience.  anyone here have one).
the 3.0l 4cyl is another story.  it is a full cast iron motor with a long history.  i think (maybe) a descendent of the iron duke, but not sure.  the 3.0l gets lots of marine use too.  the gm suppliers in the oil fields steered me away from anything below this.  the v-6 and v-8 vortecs in the industrial lines are highly regarded from reports so are

the current line of ford engines seem the choice in the 4cyl sizes.  i tend to see current gen builders using the fords in 4cyl, then chevy in v-6 and v-8.  can anyone assess this summary?  my confidence in it is middling.

ford has a 1.6 and a 2.3 inline 4 currently.  i do not know the gen or pedigree of these engines.
http://www.edi-dist.com/ford_TSG_416.asp
http://www.edi-dist.com/ford_DSG_423.asp

is this the ford engine you all were reviewing positively a few pages back?  not sure if that was a previous generation or not.

the toyota r22 seems a wonderful choice with lots of parts.  it seems one wants to stay with the double timing chain versions to minimize their known propensity to break and take out the rest of the show. 

the wisconsin v-4 engines seem about gone.  not much work on them these days to keep up with emissions issues.  a side valve engine gets difficult.
http://www.mgbryan.com/products/engines/wisconsin

diahatsu has a 950cc 3 cyl that gets used in small ute trucks all over the world, but not too much in the us.
http://www.daihatsu.com/catalogue/engine/showroom/

-------------------------------------------------------------

v-twin options.

in the v-twin world, there are growing water cooled options.  i went through the large air cooled options and found them a bit loud, and the lack of water to do things is less than ideal.  i decided that water was not negotiable.  otherwise, kohler goes up to 980cc and it is a great engine. 

kohler has a 750cc water cooled job for about $1900
http://www.kohlerengines.com/onlinecatalog/productDetail.htm?productNumber=Aegis%20LH755

kawasaki also has 750cc and 850cc water cooled units.

750cc water cooled
http://www.kawpowr.com/engines/detail.aspx?id=6&cat_id=1

850cc water cooled, efi
http://www.kawpowr.com/engines/detail.aspx?id=54&cat_id=1

at least on the kohlers, the mech governors don't like to perform well below about 2200rpm.  they get particularly fussy below 1800rpm.  the weights are calibrated for elsewhere. 

subaru-robin doesn't have any water cooled

yanmar is diesel only

perkins no spark at small scale


but course there is the harley.  many generations and many parts there to make your slow speed shake the house down thumper . . .

j

we have one of the capstone 30kw microturbines in our shop in berkeley.  we picked it up used after the dotcom crash, from a facility using it for back up power.

the capstone is a very impressive piece of engineering.  however, the prices on them are well above comparable piston based solutions, with only minor efficiency gains.  the air bearing is claimed to have very long life. 

like all power equipment, the total value has to work out.  it does not with the capstone.  nonetheless, it is very fun to play with.  if you are in the area, you are welcome to come by and see it spin up.

jim

i'm impressed with bob's seriousness with trying to find a route to affirm experimental and repurposed old design import engines for new interesting work.  this is a hard problem, and one i usually want to run away from given war scars from previous battles with govt regulatory entities.  it is a deadening, thankless and usually sum negative task.  so thank you bob for trying to make some progress on the near impossible.

unfortunately (or fortunately) i've found myself trying to use engines in a related non-conforming manner for woodgas based gensets.  woodgas is well outside current regulatory standards, but we're now trying to distribute engines and gasifiers that run on it.  what do we do, after just doing it diy?

with some trepidation, i've wandered into the actual regulatory text on these matters.  for spark ignition engines, there seems to be some relief for low volume or transitory engine designs.  i'm not sure if it understand the particulars yet, but the text engaging it is here:
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr;sid=368553d7c4d90b62423a24a74e2b5086;rgn=div5;view=text;node=40%3A32.0.1.1.9;idno=40;cc=ecfr#40:32.0.1.1.9.7.1.7

the general section on all issues for small stationary spark fired engines is here:
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr;sid=368553d7c4d90b62423a24a74e2b5086;rgn=div5;view=text;node=40%3A32.0.1.1.9;idno=40;cc=ecfr#PartTop

there seems some possibilites here, but then again the emissions issues on otto engines are always less than late fuel/air mixing compression fire engines.  it might be that spark engines have some latitude and exceptions not similarly allowed in compression fired engines.

looking around the site a bit more, here's the related info on compression fired engines.

the general section on all issues for small stationary compression fired engines is here:
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=41ce2d3e804c63067eee0e52fe4f7d37&tpl=/ecfrbrowse/Title40/40cfr1039_main_02.tpl

some interesting potential exemptions:

exemptions for engines using non-commerical fuels
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=41ce2d3e804c63067eee0e52fe4f7d37&rgn=div8&view=text&node=40:32.0.1.1.3.7.1.4&idno=40

importer eq manufacturing flexibility
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=41ce2d3e804c63067eee0e52fe4f7d37&rgn=div8&view=text&node=40:32.0.1.1.3.7.1.7&idno=40

reading the importer eq manufacturing flexibility, there seems to be a provision to import non-conforming engines with a bond posted per engine.  150 dollars per engine under 19kw.  that seems a small gate fee to continue to be able to play with our engine bases of interest.  has this route been explored previously?


for the full regulatory monty, see here for the top level link for all categories of stationary engines and related non-vehicle engine uses:
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?sid=41ce2d3e804c63067eee0e52fe4f7d37&c=ecfr&tpl=/ecfrbrowse/Title40/40cfrv32_02.tpl

has anyone explored these texts in detail?  maybe this has passed here before and i'm not aware of the details.  i know we always reference the coming and going of epa problems, but i've yet to see a good parsing of the regulatory particulars. 

anyone see any new ideas or possibilities in these links?

jim

the wiki article that started this thread is a bit optimistic on the ease of the induction generator grid tie scenario.  yes, it is easy to do, but it is not without some potential failure modes that will create islanding.  these are more rare than with a regular synchronous alternator, but they still need to be attended too.

there is a very good article on the full monty of issues here:

Induction Generators: What can go wrong?
http://findarticles.com/p/articles/mi_qa3726/is_200010/ai_n8909370/

jim

Quote from: mobile_bob on May 08, 2010, 10:42:51 PM
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

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

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

i should clarify in this that the reason the number belts like the 3vx are higher power density than the letter A or B belts is due to a deeper groove and thus more gripping surface.  the letter belts were designed at a time of much lower tensile strength materials, so there needed to be more belt to gripping surface to keep the belt together.  the number belts are "cross section to gripping surface" ratioed under the assumption of better tensile strength materials, and thus are much smaller for the grip area used.  the flat ridged belts and toothed belted move even moreso in this direction, given their being later standards.  the tooth belts, for instance, are all engineered on the assumption of carbon fiber strands for their tensile strength.  they are surprisingly thin for the amount of power they will transmit.

you cannot, or at least should not, try to run a number belt in a letter sheave.  the 5 and A belts/sheaves can be mistakently mixed i believe.  nothing will really mix with the 3 line, as they are 3/8" wide and smaller than anything in the letter line. 

note also that there are derates for service factor and engine drive type.  a one cylinder engine will require a bit more pulley than a two cylinder, given the rougher pull.  the charts have all these factors laid out, thus you might find yourself putting together a 20hp drive for a 15hp engine, after you calc out all the service factor issues.

j

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

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

bob,

it seems the efficiency increases here are mostly from more complete burning of the diesel fuel.  this is the same effect one gets with propane fumigation of a diesel, or dare i say it, HHO (more accurately called hydrogen and oxygen derived through electrolysis).  diesels generally have such poor combustion completion characteristics that even making your fuel with an inefficient electrical based process can be net positive given the gains using more/all of your primary fuel.  you can get a similar effect in an otto engine by cooling the charge with water injection and then running it lean.  the usual rich mixture to keep things from overheating only leaves fuel for the cat to burn to usually not useful heat.

cooling the charge via a second fuel vaporization event will help your total power potential given the greater charge density, but should not effect efficiency, at least in a diesel.  the top and bottom temps should still have the same delta.  in an otto that is throttling the intake, heating the intake during partial load will actually increase efficiency, as you need less throttle thus less throttle losses pulling vacuum against the butterfly.  you can't get this bump in a diesel, as it doesn't have the original problem.  this lack of throttle losses is why a diesel is so much more efficient than an otto at partial load.

if you want to explore these relationships, it might be easier to do it with propane than gasoline.  you will also get more cooling with propane than with gasoline, assuming you feed the liquid and let it vaporize after injection. 

but whether propane or gasoline, i think you are going to find there are fumigation limits based on the detonation character of the fumigation fuel used.  for instance, in the wood gas world, when dual fueling an engine, the substitition ratio limits vary with the compression ratio of the engine.  if the cr is too high, the wood gas will move into detonation at high substitution. to prevent detonation you need to reduce the amount of wood gas substitution.  the total temps achieved on compression are not likely changed much, but the detonation point does, apparently even within the ignitable flammability limits.  outside the flammability limits, as one will have on a very lean mixture, detonation should be impossible.

wood gas seems to have an absolute cr limit of somewhere around 17:1. +/- 3 or so depending on which one of us is waving our hands about it.  either way, it is well known to be well above gasoline, and well known help clean up poorly atomizing diesels, but it too can still detonate if the substitution gets too high.  this gets worse with a turbo or and idi engine.  the changfa at least avoids these problems.

it will be very interesting to see what fumigation limits you find with gasoline or propane.  i know at least with starting ether, the substitution limit is about 0% . . . ;-)

j

i've just been through this myself too, and learned much at the feet of a drive guru as a local bearing shop.

the main thing he clarified which i did not realize was the great difference in belts / pulleys between the letter and number series.  the classical v belt is the common A or B , etc belts we all know.  they are a very early industrial standard, not much changed since their origin.   there is also the 3, 5, etc lines that i've previously just fudged in with the rest of them.  turns out these are quite different and allow for much higher drive densities and somewhat higher efficiency.  the 3vx belt was originally designed for automobiles.  i think 50s or 60s in origin, maybe via dodge.  it is a 3/8" wide belt.  ganging them in 2,3,4, etc sheaves gets to surprising drive hp ratings that significantly exceed the letter line.  at typical pulley sizes, (4-6"), they are about 7-8hp per belt.  the drive guru i sat at the feet of repowers letter drives with these number drives constantly with attractive results.

as for the microgroove belts, if you go through the charts properly, you will find them to be about .5hp per ridge.  most of the lister belts we use are 10 ridge, so they are really only rated for 5hp.  but we are also running them over larger pulleys and thus bigger grip surface.  either way, i was surprised how difficult it was to get a rated 20hp drive out of the micro ridge belts, which is the size i need for my current app.  it basically required such a large number of ridges, like 40, that it wasn't realistic to find a belt or pulley to do it.  this was in the J line.  if you go to the L it is much more possible, but in my app i have the engine and genhead inline and offset, with relatively close centers.  the L belt would not work with such close centers. 

this is the problem with the larger higher capacity belts.  they start to not like close distances between the drives.  the 3vx was the only belt i could get to work out in relation to the charts.

you can see the set up i have here:  http://www.gekgasifier.com/forums/showthread.php?p=1316#post1316  actually in this photo i have a fancy 8mm tooth belt drive installed.  this is now changed for a triple stand 3vx.  i was all excited about the toothed belts given their extreme efficiency and very high power ratings over a small belt.  however, at least in my apps i couldn't get it to perform satisfactorily at all.  i had a tremendous problem with resonance, almost like a running a chain.  this got particularly bad if things were not extremely tight.  and if extrmeley tight, or really just properly tight, it whined like a blown hot rod.  the point of the rounded tooth timing belts was partially to get rid of the whine typical of the square ones.  but i still had a huge problem with the round ones.  it makes a whine at a frequency that carries like the dickens.

thus it was back to the v belts.  i tried all the more exotic options, with the general bias that v belts are old, boring, and superceeded.  but after going through all of them, and finally learning how to read the charts, and getting a drive guru to walk through all of it with me, and doing the same again myself in all the catalogs, i realized the elegance of the v belt.  but a very specific belt line, the numbered ones, and with the notches.  the #vx line.  the pulleys that come standard with changfas, listers and st genheads are not these v belt types.

i found all this very interesting.  and somewhat "embarassing" to be back arguing the best total value optimization with a v belt solution.

jim

this is a very interesting scheme bob.  i had not ever heard of someone trying this and i too am surprised that it works.

my guess is that the lack of detonation is due to the partial load you are running and the lack of mixture within the flammability limits of the gasoline.  gasoline has surprisingly narrow flammability limits, so at a significant partial power your gasoline mixture is going to be very lean, maybe so lean that it is out of range for detonation.  once the diesel injects and starts the combustion, out of limit mixtures will also ignite.

here's an interesting chart of flammability limits of common fuels.  note the extremely wide flammability ratios for hydrogen and carbon monoxide, which is what makes wood gas as forgiving as it is.

http://gekgasifier.pbworks.com/Combustion-Characteristics-of-Common-Fuels

also it would be interesting to repeat your experiment in an indirect inject diesel, like the common lister.  we often speculate that these will be more sensitive to detonation due to the edges of the precombustion chamber than can run hotter than the general cylinder and piston.  the DI engine has fewer edges to worry about and thus can usually take higher compressions in dual fuel.  or at least this is what we like to tell ourselves with wood gas.  i've let to test them side by side, but such is the common understanding.

jim mason (newbie)