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Run an Engine with the GEK

How to do wood gas conversions for gasoline, diesel, and propane/natural gas engines with the GEK Gasifier. 

 

        

 

Have you welded and painted and properly assembled the GEK Gasifier? Have you fired up the flare and adjusted the results until you get a clean gas? If so, you've graduated to the next level: run an engine with the GEK to start making power. Below are the instructions and suggestions you will need to get started.

 

 

 

How to size your engine

     We are currently selling the GEK in two sizes:

• The smaller size is a 3'' reduction bell capable of producer gas flows up to 40m3/hr with the ability to support ~13HP for an engine or 10kW generators. 
• The larger 4'' reduction bell provides for up to 80m3/hr flows supporting ~27HP for an engine or 20kw generators. 

 

The main rule of thumb (equivalencies) to remember: 1 kg of biomass ≅ 2 lbs biomass ≅ 2 m3 woodgas ≅ 1 HP-hour ≅ 0.75 kWh electrical

 

When considering an engine for a vehicle conversion it is useful to refer to some of the conversion relations here.

• Relating Gasoline/Diesel to Woodgas to HP to KWe in your vehicle or genset 

1 gal of gasoline or diesel will make about 15HP of shaft power for one hour.  If driving a genset, this will produce about 10 kWh of electricity.

1 gal of gasoline or diesel is equivalent to about 20lbs of biomass through a gasifier.

1 ton of biomass to power through a gasifier-engine system is equal to about 100 gal of liquid fuel in a genset, or 1 MWh of electricity.

 

• How much HP is your vehicle using at cruise?

60MPG = 1gal/hr or 15HP for one hour

30MPG = 2gal/hr or 30HP for one hour

15MPG = 4gal/hr or 60HP for one hour

 

• How much woodgas do I need to make x amount of HP?

1HP = 2 cubic meters of woodgas per hour

5HP = 10 m3/h

10HP = 20 m3/h

50HP = 100 m3/h

100HP = 200 m3/h

 

>>If you are looking to do an engine conversion, we recommend using the 4'' reduction bell (GEK 20kW) with something like a 22-R or 22-RE Toyota engine. The 4 cylinder engines will work well, the 6 cylinder engines will work too. However, 8 cylinders are generally too much for our gasifiers. Consider the larger the engine, the higher the consumption and that much more in square yards of wood chips you will need!

 

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I. Convert your engine to run off of wood gas

 

Running an engine on wood gas requires some relatively minor tweaks to the engine air intake system.  With either a gasoline or a diesel engine, you are going to be introducing the wood gas into the stock air intake system.  You do not need to create a complicated new carburator like a propane or natural engine.  Rather, you just mix the wood gas in with the air on the way in the normal air intake.  As the correct wood gas to air mixture ratio is about 1:1 and is very tolerant of error, it is quite easy to get a reasonable mixture with very rough solutions. 

 

The easiest way to make a wood gas mixer is with a plumbing tee and a ball valve (sized appropriately for the enging intake).  A tee is put in the air intake pre filter, with one leg of the tee going to the gasifier, and the other going to free air.  You install the ball valve on the air side.  Mixture is then controlled by opening or shutting this ball valve.  To the degree you shut the ball valve, more gas is pulled from the gasifier.  To the degree you open the ball valve, more air is pulled from atmosphere.

 

Here's some pictures of a simple "tee and ball valve" carburetor like the above.  Alternately, you can look at any one of thousand pictures of the same sort of arrangement around the wood gas world.

 

People usually mount their new wood gas carburetor on the intake to the existing air filter.  This will be your last filter before the engine.  Some people like to add bigger ones here.  But most do fine using what comes stock with the engine.

 

Here's a few things to consider when attaching your wood gas mixer to your air filter:

• Keep it air tight: Air filter canisters are often far from air tight! (On the Honda Accord, we did not notice an extra unpopulated bolt pattern underneath the canister this was delivering leaner mixtures than our controls indicated which caused problems).
• The extra T fitting and valve will add extra weight to the canister. They are typically not designed to support weight, make sure your design holds up.
• Minimize the amount of mixed fuel/air you have in the system.  Place the T for the air mixture connection as close to the air filter canister as possible.
• The air to fuel ratio for wood gas is 1:1. However, the air mixture valve pipe diameter will be smaller than the wood gas line. For the GEK, use the existing 1.5'' wood gas line with a 1'' or 3/4" air mixture ball valve. The vacuum from the engine will more easily pull air in through the air line than wood gas from the gasifier.
• Consider putting the air mixture valve at the end of a longer tube.  This is to prevent puffs of CO coming out the air side of your mixer.  This is especially important with one cylinder engines.  The puffing nature of the intake can send CO out the air side of the mixer
• Put your air into the tee on the perpendicular leg.  This helps reduce puffing out the other end.  Try to not put the air into the tee so that it has a direct line shot out the open leg.  The gasifier and the engine should be on the straight through shot legs.  The air on the side leg.

   

 

Gasoline Engine Conversion

 

Carburated Engine

Carburetor gasoline engines are fairly simple to convert.   One build a wood gas carburetor like above.  The air filter housing is modified so the mixer can attac to it.  And the timing is usually advanced 10-15  degrees.  Wood gas has a slow flame front, thus you need to advance the timing to maintain reasonable power.

 

The throttle in the carburetor continues to be used for the speed control.  Like with regular gasoline, the mixture is done separately of the butterfly in the carburetor.  The butterfly is to control the amount of mixed fuel/air that goes into the engine.  We will continue to use it for such, just with the gasoline shut off, and the mixture now done externally with the wood gas mixer.

 

The mixture will be controlled manually with the ball valve on the air intake side.  Usually one tries to start with the valve near closed (or very rich mixture), and slowly open it while cranking.  At some point in this slow opening you will cross the correct mixture point and the engine will fire.  Then you adjust the valve back and forth until you hone in on the exact mixture.

 

This valve setting for correct mixture will change with engine speed and load, as well as gas quality out of the gasifier.  This is why a fully automated mixture system is desired for regular hands off running.  The manual solution is fine if you are sitting there driving a vehicle with wood gas.  It is more of a problem with a genset where you are not standing there operating the machine full time.

 

Here's what our automated system looks like on our Power Pallet gasifier-genset skid.  For a manual system, you would have a regular ball valve where the servo controlled valve is in the pictures.

 

 

 

Picture of Kholer engine in 10Kw skid (Power Pallet) with automatic air mixture valve

http://www.gekgasifier.com/forums/showthread.php?t=332

 

 

Fuel Injection Engine

 

Fuel injected gasoline engines are also good candidates for wood gas conversion.  You will still enter the wood gas into the engine via the air intake.  Shutting off the gasoline fuel with injectors is faster and more precise than a carburetor.  Some ECU systems with fuel injected motors will still correct mixture for you with a small amount of gasoline.  Thus  you can leave the injectors on and slowly add in wood gas.  However, this is somewhat unsatisfying after you've gone to all the work to get your gasifier to work.  You usually just want to cut the gasoline altogether.

 

To cut off the fuel injectors you need to locate the wire delivering power to the fuel injectors (reference the wiring diagram in the manuel for the enigne).   Once found, put a switch in the line, ideally mounted somewhere near where you are going to operate the machine.  Then you can easily go back and forth between gasoline and syngas at the flip of a switch. 

 

Important: Do NOT just put a valve in the gasoline line.  You can ruin your fuel injectors if you run them dry for extended periods.  You must cut the power to the injector, NOT the fuel the injectors. 

 

Some contempory ECU units will auto advance the timing for you, via the stock detonation sensor.  Some will not.  Here you need to get into the wires and diagrams of your own system.  Sometimes you need to a hybrid with some amount of manual advance so the the auto advance has enough potential travel.  This is what we had to do in our 1990 Honda Accord conversion.  Some pictures from that conversion are below (note: the injector fuel switch is in the mouth of the dinosaur on the dash).

 

 

Picture of Honda Accord conversion with Dino Fuel Injector Cut-off Switch

http://gekgasifier.pbworks.com/How-to-Make-a-Woodgas-Carburetor

 

 

Diesel Engine Conversion

Duel Fuel Mode

 

     The easiest way to run a diesel on wood gas is in dual fuel mode.  You can also take out the injectors and replace them with spark plugs, while also setting up the ignition and timing to run them.  This is often seen as too much effort, so the engine is run in dual fuel mode.

 

In dual duel mode, wood is wood gas is still introduced through the air intake, but ignition is provided by a small amount of diesel.  The wood gas / air mixture will not auto ignite on compression, or if does, it will be timing uncontrolled.  There still needs to a small amount of diesel injected to provide the ignition event at the correct timing.  The wood gas substitution ratio can go up to about 90% usually.

 

The diesel engine still remains an unthrottled intake when running in dual fuel.  Like a regular diesel engine, there is no throttle plate that is used to adjust the amout of fuel/air introduced to the engine.  However now, instead of adjusting the amount of diesel coming in via the injectors, we now vary the amount of woodgas coming in the air intake.  In essence, what was the "mixture valve" in the gasoline engine is now the speed control valve for the diesel set up.  

 

You still have one side of the tee open to atmosphere, with ball valve to control, and the other side of the tee going to the gasifier.  The more you shut off the air, the more wood gas will get pulled into the engine.  Note this wood gas / air will NOT be mixed to the correct stoichimetric ratio.  A diesel engine does not need this due to the higher compression, and the injection event creating all possible mixture ratios as it propagates into the cyclinder.  At some point during this injection propagation, the mixture will be correct, and things will fire.  And once it fires, the rest of the wood gas will get quickly invovled in the pyro show.

 

Note also that you can over choke the air coming in with the mixture valve so you do not have enough air to complete combustion.  This will result in a rich mixture, and syngas going out the exhaust pipe.  A proper diesel dual fuel set up would include an O2 sensor on the exhaust to control for overmixing of wood gas, same as with a regular diesel rig.

 

There is also a compression ratio limit for running wood gas in a diesel engine.  If you go above this, you will start to get auto-detonation and will have to reduce the woodgas substition amount.  Most turbo diesel engines are not appropriate for wood gas conversion because compression ratio can exceede the compression ratio optimal for wood gas combustion.

 

 

Spark Conversion of Diesel (advanced)

 

By using a spark plug, no additional fuel needs to be used to ignite the mixture.  This is often the way natural gas engines are derived.  They are often burly diesel engine bases, from which the injectors have been removed and spark plugs installed.  The result is a very high compression spark fire engine, with all the robust characteristics of a diesel engine that help to make them long lived (minus the lubrication from the diesel fuel).

 

You can also do the same with your local diesel engine.  Ignition systems are easy and cheap, and spark plugs often near fit into injector holes with minor persuasion.  Here's one we did recently.

 

 At the APL workshop in February 2010, Ken Boak, Darrel Licks and Mike A converted a standard Lister 6/1 diesel engine to run on 100% wood gas engine via spark ignition.  This worked despite this being an indirect injection lister, and the spark plug being hidden way up in the precombustion chamber.  We we're unconvinced it would fire with this type of conversion, but it did just fine and ran great.  The spark was provided by an Arduino microcontroller with timing from a Hall effect sensor on the flywheel shaft, the results firing the spark plug we press fit into the injector hole.

 

 

http://www.gekgasifier.com/forums/showthread.php?t=312

 

 

II. Run the engine off of wood gas from the GEK

This section assumes that you have properly assembled the GEK and tested the wood gas to ensure that your gasifier is producing quality wood gas given the characteristics of the biomass that you are using. If you introduce tarry wood gas into your engine, it will damage your engine by sticking the intake valve(s) and piston rings. To ensure this does not happen, use dry biomass, make sure that you are within the proper temperature and pressure range in the reactor, double check seals on the gasifier, and make sure filters are not spent.

 

The Hand-off:

 

A) Turn off the Flare:

     1. Make sure the flare is steady in the swirl burner. The flare should be down inside the swirl burner with the flame terminating before reaching the top of the burner. 

     2. If you have hooked up propane to the ejector venturi line, make sure that the valve and take are OFF.  The wood gas flare should be sustained with out supplementing other fuels.

     3. At the same time, close the air mix valve (a) and the ejector venturi gas valve (b). This should be done in a way that does not expose the operator to any wood gas from the air mix valve.  If you leave the air valve open at all CO rich gas will come back out the air intake.

 

 

     a)   b)  

 

     4. The open the gas valve to the engine (c), while closing the air compressor valve to the ejector venturi (d).

     5. Start the engine:  Crack the air valve just slightly and start cranking the engine.  You should start with the valve near closed (or very rich mixture), and slowly open it while cranking.  At some point in this slow opening you will cross the correct mixture point and the engine will fire.  Then you adjust the valve back and forth until you hone in on the exact mixture.

 

c)d)

 

     6. Once the engine is running, you should continue to fiddle with the air valve to optimize the mixture.  The correct valve position for the correct mixture will vary with engine speed and load, as well as gas quality coming from the reactor.

 

 

 

 

III. Shut down the GEK

• To properly shut down the GEK, run it in flare mode.
• Turn down the ejector venturi down low so the pressure reading on the manometer is around 1''H2O.
• Wait for about 3-5 minutes or so, then close the gas valve to the ejector venturi, place a cap on the air inlet on the reactor, and close the air compressor valve on the ejector venturi.

Check to make sure any other openings are closed such as the ignition port.

• BE CAREFUL: if any gases are released upon shut down, be sure not to expose yourself or others.

 

IV. More Info:

Inventory of All Online Wood Gas Generator Plans

 

Options for Engines and Electric Gensets

• Summary of Genset Options for Wood Gas
• Genset models and sellers of interest
• More on How to Make a Woodgas Carburetor 
• Build a Pair of Dual-Fuel Carburetors  

 

Papers on Optmizing Engines for Producer Gas

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