single cylinder diesel dual fuel operation

[bob g]

although a bit crude we had to know if the thing would run in dual fuel mode.

first i might add my friend ran the engine on straight 50 weight last night, this morning we had a little problem getting it to fire on this heavy of oil. i don't know why he did it but none the less it did start and smoke a bit, not horrible but smoke none the less. after about 2 minutes the thing came up to temp and cleared the exhaust considerably. i think if the fuel/oil was preheated it would have no starting problems or smoke.

he says 90 weight is next, i told him, "u mark this engine as yours" mine is going to stay in the crate

i don't think he is serious, but you never can tell.

now dual fuel:

a diesel engine has no butterfly in the intake and as such no manifold vacuum, the way the rpm is regulated is by means of fuel delivery, more fuel more rpm, more load/less rpm and the govenor opens the fuel rack and delivers more fuel. so air fuel ratio's are not a factor, low ratio equals lower rpm or lower power. higher fuel air ration, more rpm and more power.

so i considered that if the engine was brought up to maximum governed rpm the fuel rack is advanced to deliver the amount of fuel needed to maintain the 2000 rpm max rating. any addition of fuel to the engine thru the intake, ie. propane which richens the air fuel mix, in this case would do one of two things.

1. the engine would gain rpm in proportion to the additional fuel delivered (propane) if the govenor did not taper back the diesel fuel, or
   
2. the engine rpm would remain stable, indicating that the fuel rack had been backed off thus delivering less diesel to maintain the load and rpm set point.
   
   

what we found was indeed the fuel rack must be tapering back the amount of diesel injected as the rpm remained stable, no change.

the only change we noted was a slight softening of the normal diesel knock.

now i havent set up the necessary graduated pippets (sp) to determine the offset of diesel in dual fuel mode, but

we have determined that the engine will run in dual fuel mode, without any secondary detonation or secondary knock, which reportedly happens at low loading of larger engines.

this looks very promising at this point,

i will need to get the graduated cylinders to montitor and calculate the fuel offset, and do more testing, likely after we have everything bolted down and a load attached.

i may try alcohol as a dual fuel suppliment in a crude experiment this weekend and get back with the results

the next stage is the design and implimentation of these engines into a cogeneration package, that i am very excited about.

bob g

[wdyasq]

In dual fuel diesel engines, running a gaseous fuel, a carburator is installed in the intake.  The diesel 'rack' is taken to the idle setting and the fuel/air mixture controlls the speed of the engine. The diesel pump and injector are only an iginition source for the otehr fuel.  Gasoline and low octane fuels cannot be used because the compression heat will predetonate the mixture.

Some of the Indian manufacturers have bio-fuel adapters and can burn woodgas or methane from digesting sewer.  Engines running alternative gaseous fuels must be de-rated according to ruel, mixutre and altitude they are running.

Normal procedure for running heavy oil in a light diesel is to switch back to diesel before shutting down and burning out the heavy oil so the machine starts on the lighter diesel fuel.

Ron

[bob g]

"In dual fuel diesel engines, running a gaseous fuel, a carburator is installed in the intake.  The diesel 'rack' is taken to the idle setting and the fuel/air mixture controlls the speed of the engine."

yes the carburation method is one of many, but the fuel rack is not brought back to idle , because depending on the alternate fuel used there are differing amounts of pilot fuel to ignite the mix.

also i would state that most dual fuel applications are heavily engineered to get max performance, highest efficiency and best cost.  a delicate balance to say the least.

my approach has a much different criteria.

1. i am not concerned with max efficiency, but rather alternative fuels that can be used.
   
2. max performance is of small concern, i am prepared to lose some power in production.
   
3. low cost is an important consideration, in that the cost of implimentation needs to be small.
   
4. the ability to use as many differing alternative fuels to keep the engine online, is of paramount importance.
   
   

"Gasoline and low octane fuels cannot be used because the compression heat will predetonate the mixture."

i am not anticipating using any low octane fuels, dont even want to experiment with that. engine damage will result.

"Some of the Indian manufacturers have bio-fuel adapters and can burn woodgas or methane from digesting sewer.  Engines running alternative gaseous fuels must be de-rated according to ruel, mixutre and altitude they are running."

wood gas is planned as a alternate fuel, and yes i am prepared to derate the engine,  although derating is in direct proportion to the ratio of offset of diesel with alternate fuel (woodgas)

"Normal procedure for running heavy oil in a light diesel is to switch back to diesel before shutting down and burning out the heavy oil so the machine starts on the lighter diesel fuel."

good point, we already have the fittings planned to add the second tank, so as to start on diesel and switch to heavy fuel on run, then reverse procedure at shutdown.

thanks for the insights, all are appreciated

such fun stuff

bob g

[wdyasq]

Bob,

I have considered the grease diesel starting procedure and if I do one I will probably have heavy oil and light oil filters before the injection pump. To change fuel for killing you would switch the light fuel on and put light pressure on that side of the system, forcing some of the new, light fuel back into the heavy oil filters.

In the start the next day there might be enough 'light' fuel to both start the engine and warm it enough to run the heavy oil.  If not, I would pump a bit more 'light fuel' during the kill procedure.  The heavy oil filter might be heated by a copper coil and hot engine coolant, as would all the 'heavy fuel' side of the system. This should allow a 'start and forget it' method of running the engine.

Ron

[bob g]

good idea Ron:

i was leaning toward a copper coil around the muffler, but the water heater method might be better and more stable.

i like it

bob g

[wdyasq]

Just a little more on technique and thoughts Bob.  When I serviced small diesels for a living I carried an outboard boat engine 'fuel bulb'.  This would be used to fill the filters and prime the fuel injector pump. It could be left in place on an arrangement like yours and be used to flush the 'grease' out of the system.

If you are going to 'co-generate' heat, a small recirculating pump could be used to pre-heat the engine from the hot-water tank.  Another way to preheat gently would be to make a small tube-in-shell heat exchanger and use propane or some other small heater and heat the combustion area for easier starting. Pre-heating engines also reduce wear as engines need to get to operating temperature for best wear charactistics.  A thermostat should be used in all engines and it should be of the proper temperature range to assure proper operation.

In aircraft, oil is drained at night and heated before cranking the engine in really cold weather. Fires are even built inside the cowlings to heat the cylinders for starting. I'm sure not many have the testocular fortitude to build a fire under a gasoline engine - when it is the only way out of the 'bush'.

Ether can be used to help starting in cold weather.  It can also cause engine damage and/or hard kick-backs in small diesels.  A SMALL amount of gasoline held on a rag in the intake or put on the air-filter will do similar things with less chance of damage.

For noise and vibration reduction I am considering building a 'floating' generator and moor it in a small pond.  A light dose of oil on the surface would keep the oil from evaporating and small dock-lines would keep it centered.  The only connections would be the wiring, waterhoses, fuel lines and oil-lines to a by-pass and conventional oil-filter.  The exhaust would supported and have a flex-coupling to the 'boat' but not the shed. This would isolate the radiator from vibration problems. Vibration eats radiators on thumpers. It would also have all the maintenance pieces off the engine and where it coould be easily serviced.  Ease of service usually means more consistant and better service.

Ron

[bob g]

i hadn't considered floating on a pond but a novel approach to noise isolation

thinking of using small dock bumpers like used on the back of trucks or trailers to sit the frame work down on.

the dock bumpers i have in mind are tapered and would work well set partly into the concrete floor to keep the machine located.

i already have a couple of heat exchangers, hot water heaters, like radiators with fans built in but made for space heating.

i figure on looping the coolant to provide domestic hot water, in a closed loop system so as to not contaminate the water with antifreeze/coolant if there were to be a leak.

i figure the 12 hp to have approx 40,000 btu per hour of harvestable cooling system heat to use for space heating and for domestic hot water, the 6 hp unit somewhere around 15 to 20 k btu/hr.

i also have a heat exchanger to harvest the exhaust heat, it is off a dihatsu car, i picked it up surplus new, it basically is a muffler looking thing with water ports. should be able to harvest an equal amount from the exhaust

bottom line is if i can get a good heat capture from both the exhaust and the water system i should get around 50k btu off the 12 hp at load and maybe 25 k btu off the 6 hp unit

that is a significant amount of heat, and goes a long way toward improving the overall efficiency of using the unit as a cogenerator.

i got to get caught up and work so i can get to building the cogenerator

never enuf time

bob g

[ghurd]

""In aircraft... of the 'bush'.""

I will say I've seen a lot of 'unusual' things.

Many that just no one would ever believe were in the bush.

Three (French-ish) quotes come to mind.

"Must be very carefull when you make the circus <circles>,

make the good circus <circles>

cause no one here to help you again"

"Nooo!  It's not illegal... in the bush"

"What else I gonna do?"

Yea, Now, I'll believe about anything from the bush.

G-

[ford]

   Some of the smaller Ag tractors use propane to clean up the exhaust to meet the EPA  regs , using alcahol or methanol thru the   injector pump will cause massive wear and falure probably within an hour , "hot " fuils will need increased piston cooling , turbocharged diesels spray oil up the bore to cool the piston , If you are looking foe odball fuils take a look at what the tractor pulling brigade are using , they are after pure brute power not economy and use many exotic ways to get it,  like methanol water mixes injected into the intake manifold .they are multi fuil engines , ( and they destroy a lot of them when they get it wrong )

[bob g]

not planning on running anything like alcohol thru the injection pump, just isnt enuf lubrication and the pump will sieze in short order.

if i do the alcohol route, i will likely carburate it into the intake charge.

also am not looking to hotrod the engine, just be able to run other fuels

of course it might be cool to get 100 hp out of a 12 hp changfa, , at least for the second or two that it keeps from the "untogether"  

nah!!!  

bob g