Homemade Hydrogen Generator
Homemade hydrogen gas
generators can be as simple as tying stainless steel plates together
and electrifying them and as advanaced as a multi-cell stainless
steel hydroxy generator that can produce a liter or two of gas per
minute. There are many options available on the
internet. The biggest question that needs to be answered is
what will you be using the hydrogen generator for and how much gas
is needed? One of the best documents Umpua Energy, Inc. has
seen on the internet is the Tero cell - and we have actually built
one. It is a fun project and the cell produces nearly two
liters per minute of hydroxy gas. Note: To avoid a run away
reaction, it is recommended that you control the amperage to the
hydrogen generator by using a PWM circuit that you can buy from
several sources within Ebay.
Electrolyzer
The electrolyzer shown
in Figure 1 is based on the common-duct series-cell
electrolyzer concept originally developed and patented by William
Rhodes, Ernest Spirig, Yull Brown and later refined by Bob Boyce,
George Wiseman, etc? It uses an alkaline (NaOH, KOH) electrolyte to
split distilled water into hydrogen and oxygen components very
efficiently.
The produced hydrogen and
oxygen gasses are not separated to separate containers, but kept
mixed. The produced oxyhydrogen gas is a stoichiometric mixture of
hydrogen (2 parts vol.) and oxygen (1 part vol.) and can be
combusted in vacuum.
The combination of
series-cell topology is very efficient, because it allows the cells
to operate as close to their optimal cell voltage (1.47V) as
possible. The electrolyzer runs fairly cool, at about 30-50 C
depending on the current and electrolyte.
The electrolyzer shown in
this report has about 80-90% total efficiency when all things are
considered (ambient temperature, ambient pressure, accurate
measurement of gas volume and current) when powered by straight DC.
Pulsing (PWM) or modulation of the input voltage waveform could
increase the performance further, as it is known that in the
beginning of each pulse larger current flows than in the steady
state condition, thus lowering the cell voltage needed to push thru
a certain amount of current and increasing the efficiency slightly.
There are also claims of various resonance phenomena (Boyce, Meyer,
etc.) that supposedly dramatically increase the gas production rate
vs. input current when the electrolyzer is driven with a certain
type of PWM rich in harmonics. However, this author has not been
able to replicate any resonance modes in any sort of electrolyzer.
The electrolyzer has 7 cells
with a target input voltage of about 12.9-14.1Vdc depending on
temperature. This makes the cell voltage about 1.85-2.0V.
Electrolyte in each
compartment is practically isolated from other compartments, but
there are 3mm diameter electrolyte level equalization holes drilled
in the bottom corner of each plate (staggered)
Soft transparent PVC spacers
rings
Protect and repair your engine from
hydrogen
embrittlement by using a ceramic treatment.
Figure 1. Series cell
electrolyzer cross-section
Electrolyzer construction
The eight electrolyzer
plates (Figure 2) are about 0.8mm thick 160mm x 200 mm
stainless steel (304 grade). A 10mm gas vent hole is drilled in each
plate. The electrolyte level is always about 25mm below the gas vent
hole. There are 3mm diameter liquid level equalization holes drilled
in the bottom corner of each plate (not shown) in such a way that
adjacent plates have holes in opposite corners. Staggering and using
small holes minimizes any efficiency loss due to current leakage
between cells, but makes electrolyte refilling and level
equalization significantly easier. The two end plates have a small
SS piece welded for electrical contact. After taking the picture the
plates were sanded with an orbital sander to expose clear metal and
then cross- hatch pattern was ?engraved? on the plates with a rough
file attached to a wooden block. This is to increase the active
surface area of the plates and seems necessary for ultra high
efficiency. Other methods to increase plate area exist as well.
Protect and repair your engine from
hydrogen
embrittlement by using a ceramic treatment.
Figure 2. Stainless steel
electrolyzer plates (8 total)
Nine spacers
(Figure 3) were cut out of 3mm thick soft and transparent PVC sheet
with a knife. The wall thickness is 12mm. The PVC sheet is
originally designed for door material for large room-size
refrigerators. The small square PVC blocks were meant to keep proper
distance between SS plate centers, but they turned out to be
unnecessary and were not used.
Figure 3. Soft PVC spacers
rings
The end plates
(Figure 4) were cut out of 12mm thick PVC plate. The size of the
plates was 200mm x 240mm. Eight 8mm holes were drilled for M8 size
stainless steel through-bolts. A ?? pipe thread was tapped in a
11.8mm gas vent hole. A valve and gas hose connector was epoxy glued
to the ?? tapped hole in both plates. Other thread sealants may not
be compatible with the electrolyte so it?s best to use epoxy or
teflon tape. The valve was lined up with gas vent hole in SS plates.
NOTE: When the electrolyzer stack is tightened up the PVC end plates
tend to bend and bulge. Some form of metallic bracing should be used
to prevent bending or the end plates made out of thick stainless
steel plate.
Protect and repair your engine from
hydrogen
embrittlement by using a ceramic treatment.
Figure 4. PVC end plates with
gas valves attached
The first stainless steel
plate and one PVC spacer ring are shown in Figure 5.
There is a PVC spacer ring also between the PVC end plate and first
SS plate. A 35mm piece of 8mm ID 12mm OD rubber hose is slid over
the bolts to isolate the bolts from the plates and hold the plates
in place. Note that it would have made more sense to drill the gas
vent hole to the upper left corner of the plates, so that draining
the all of the electrolyte out of the electrolyzer would have been
easier.
Figure 5. First SS plate in
place with the PVC spacer shown
A side view of the cell stack
with several SS plates and PVC spacer rings in place is shown
in Figure 6. Note the soft PVC sheet material in the
background with the cut outline drawn with a permanent overhead
transparent marker pen.
Protect and repair your engine from
hydrogen
embrittlement by using a ceramic treatment.
Figure 6. Partly assembled
cell stack
The finished electrolyzer is
shown in Figure 7. The two PVC end plates are clamped
together with 70mm long M8 stainless steel bolts with Nyloc nuts.
After initial tightening the electrolyzer was submerged in hot tap
water (about 60 C) with the gas vent valves closed. This softened
the PVC gaskets and allowed the stack to be tightened up even
further to provide an excellent seal. Note that the 12mm PVC plates
are quite soft and some bulging is visible. Two additional bolts
would have been useful to equalize the bolt forces more evenly
around the plates.
Figure 7. Assembled stack
The finished electrolyzer
equipped with a bubbler is shown in Figure 8. The
bubbler is absolutely essential to prevent backfires from blowing up
the electrolyzer. The electrolyzer may be filled with slightly
acidic water (use vinegar) to neutralize any residual NaOH vapors in
the output gas. It would be wise to use a non-return valve between
the electrolyzer and bubbler to prevent bubbler water being pushed
back into the electrolyzer in case of backfire.
Figure 8. Finished
electrolyzer with bubbler
Figure 9 shows the electrode
plates after the electrolyzer had been used for some time. The
chemical reactions occurring in the electrolyzer have slightly
darkened the electrolyte. The use of 316 SS electrodes would
probably have prevented this. Note how the other side of the plate
is relatively clean, while the other side has a darker deposit. Note
also the sanded and crosshatched electrode surface.
Protect and repair your engine from
hydrogen
embrittlement by using a ceramic treatment.
Figure 9. Electrode
discoloration due to chemical reactions (NaOH & 304 SS)
Electrolyzer tips
1)
Gas production is directly proportional to the current draw only. At
STP conditions (0 deg C, 1 atm) you
need approximately 1.594 Amps for each LPH per one cell, while you
need less if you measure the gas volume at room temperature.
2) The
ideal cell voltage would be about 1.48V, and anything above it is
wasted efficiency. The lowest practical cell voltage seems to be
around 1.8V-2.0V. The voltage is only needed to push the current
thru the cell, it has no relation on the amount of gas produced. The
cell overvoltage (above 1.48V) is determined by electrode materials,
current density, electrode spacing and conductivity of electrolyte.
3) Power or
total efficiency is defined as the amount of watts needed to produce
one LPH. Series-cell designs seem to have the best efficiency in the
range of 2.5-3 Watts per LPH. The most efficient electrolyzer would
have a large number (100) of cells in series with narrow cell
spacing (3mm) at a low current (10A).
4)
Many people build simple single-cell car hydro-booster type
electrolyzers and control the amperage by using weak electrolyte.
The cell voltage is often around 13V, and they put just enough
electrolyte to pass 5A or so. 5A creates only 3.5 LPH of gas, so the
efficiency is very bad at 18.5 Watts per LPH. Properly designed
7-cell series electrolyzer would produce 7 times that amount or 24.5 LPH gas at the same
input power.
5) The cell
voltage is also dependent on the current density (current /
electrode area). Smaller cell area is less efficient because it
requires higher voltage to pass the same amount of amps. Good
practical current density is around 0.5A/Sq.inch or 0.1A/cm^2. The
electrolyzer shown in this report had an effective plate area of
about 170cm^2, with a target current of about 20A.
6) The
higher the current thru the cell (higher current density) the higher
the cell voltage. Power efficiency decreases as the current
increases if the plate area is kept the same. To keep the power
efficiency the same increase the plate area in proportion with the
current (keep current density the same).
7) The
smaller the electrode spacing the lower the cell voltage. In
practice 3mm electrode spacing is good up to about 10A. At higher
currents the electrolyte starts foaming and crawling up the plates
(reduces efficiency) and the electrolyzer starts spitting
electrolyte foam out. For 10-40A use 5mm-8mm spacing.
8) Best
electrolyte is NaOH (1 part NaOH 4 parts water by weight) or KOH
(28% by wt). These give the lowest practical cell voltage.
9) The best
electrode material would be nickel, but nickel plates are very
expensive. Nickel plated steel plates would also work. The most
practical electrode material is stainless steel. The electrode
surface conditioning is very important at minimizing the cell
voltage. Best to sand (crosshatch pattern) the electrode plates to
create lots of fine sharp points.
10) Bubbler is absolutely
essential to prevent backfires from blowing up the electrolyzer.
Bubbling the gas thru a water bath is the only safe way to prevent
backfires, provided that the bubbler is strong enough to contain any
backfires and that the water level in the bubbler is high enough.
Alternatively the bubbler can have a pop-off lid or a rupture disk.
11) The electrolyzer as shown
will not be able to take any pressure without leaking. For
pressurized operation use a pressure-proof shell (metallic). If you
need to store oxyhydrogen gas for a short period of time, put a
large balloon on the bubbler lid. The balloon will store the gas at
atmospheric pressure and will not be very dangerous if it explodes
due to a backfire. Remember to wear hearing and eye protection.
It is impossible for an
electrolyzer to be anything else than 100% Faraday efficient, unless
there are significant leakage currents between cells. Passing one
Amp thru a single cell will always produce gas at a rate of 0.627LPH
when reduced to STP conditions, no matter how the one electrolyzer
cell is constructed.
This however applies only at
STP (0 deg C and 1 atm ambient pressure). At room temperature (25
deg C) the same amount of gas has higher apparent volume.
Substituting T= 25 deg C gives the efficiency as 0.684 LPH/A. Stated
the other way the Faraday efficiency would appear to be about 109.5%
if the gas volume was measured at room temperature, unless the
correct efficiency value for room temperature (0.684LPH/Amp per
cell) was used.
The thermoneutral cell
voltage is ~1.48 V, which means the voltage at which all input
energy for the electrolysis process comes from the electrical input
energy. At 1.23 V (reversible cell potential) part of the energy
comes from ambient heat and electrolyzer is about 120% voltage
efficient. Note that 100% efficient hydrogen oxygen fuel cell would
produce 1.23V. The thermoneutral voltage of ~1.48V is considered to
be the 100% voltage and power efficient electrolysis. Combusting the
produced gas will release exactly the same amount of energy that was
used in making the gas.
The 100% power or wattage
efficient electrolyzer would consume 1.48 V * 1.594 Ah/l = 2.36
W/LPH when gas volume is measured at STP. At room temperature the
100% efficiency is 2.16W/LPH.
In the literature the
electrolyzer efficiency is usually defined as the ratio of the
thermoneutral voltage (1.48V) to the cell voltage. At 2.0V cell
voltage it would imply a total efficiency of 74%. This also shows
the inefficiency of single-cell hydro-booster type electrolyzers
operating at automotive voltages (~12-14V), leading to a total
efficiency of about 10%.
Series-cell electrolyzer
voltage and current measurements
The current thru the
series-cell electrolyzer is extremely sensitive to the voltage
across it. This is because the electrolyzer acts as a very
non-linear resistance, with pn-junction like characteristics. It
takes a certain cell voltage until the current starts flowing (?knee
voltage?) and increasing the cell voltage above this voltage will
increase the current exponentially. Figure 10 shows
measured and modelled electrolyzer current vs. voltage graph for the
7-cell series electrolyzer. Note how increasing the electrolyzer
voltage from 13.2V to 13.9V (5%) will cause a five-fold (500%)
increase in current (from 2A to 10A).
Electrolyzer
current vs voltage
7-cell series-cell
electrolyzer
Electrode area = ~170 cm^2, gap = ~3mm
Protect and repair your engine from
hydrogen
embrittlement by using a ceramic treatment.
Figure 10. 7-cell series
electrolyzer current vs. voltage
Note that even the insertion of a
current meter in series with the electrolyzer may cause high enough
voltage drop that significantly reduces the electrolyzer current.
Thus it is absolutely essential that the current meter is in place
when the electrolyzer gas output rate is measured.
This extremely non-linear resistance of
the electrolyzer also causes the current thru the electrolyzer to be
modulated very strongly with any small changes in the electrolyzer
voltage. This is especially true if the electrolyzer is powered by
rectified AC, for example from a transformer based battery charger
or power supply.
The oscilloscope pictures of the 7 -cell
electrolyzer voltage and current waveforms are shown in
Figure 11. The power supply was a mains transformer followed by a
bridge rectifier and a large filtering capacitor. Note how the
electrolyzer voltage (trace 2) has a small ripple on top of it,
which causes the electrolyzer current to be modulated between zero
and peak current (trace 1), with appearance similar to half-wave
rectified AC. The current draw waveform may be easily measured with
oscilloscope by connecting the oscilloscope probe across the
multimeter terminals wired in series with the electrolyzer in the
current measuring mode. Thus the oscilloscope shows the voltage drop
across the multimeter current shunt resistor.
Figure 11. Series-cell electrolyzer
voltage and current waveforms
The pulsed current waveform causes
significant measurement inaccuracies if normal digital multimeters
or analog current meters are used. Normal current meters respond to
either straight DC or perfectly sinusoidal AC waveshapes correctly,
but show significantly lower current values for pulsed DC type
waveforms. True-RMS multimeter is required to measure pulsed
waveforms correctly (the RMS value represents the equivalent
?heating value? of any current or voltage waveform).
Figure 12 shows comparison between current readings of an analog
current meter and a Fluke True-RMS multimeter, while measuring
current draw of the 7-cell electrolyzer powered by a transformer
-based power supply (actual current waveform as shown in
Figure 11). The analog current meter shows approximately 7A while
the correct RMS value is 10A, which would cause the electrolyzer to
appear 143% efficient based on the analog current meter reading
which is not true!
Figure 12. Comparison between current
meter readings for pulsed electrolyzer current
For the most accurate measurements
straight DC should be used, preferably from a battery which is not
connected to a battery charger. If any other power supply is used,
True-RMS measurement equipment is needed for accurate
results.
Protect and repair your engine from
hydrogen
embrittlement by using a ceramic treatment.
Series-cell electrolyzer current
limiting
As the series-cell electrolyzer has very
non- linear voltage vs current characteristic, it is important that
some form of current limiting is used to prevent current runaway.
While the electrolyzer is operating it will get hot and heat will
decrease the required cell voltage to pass a certain number of Amps,
thus increasing the electrolyzer current draw if the electrolyzer
voltage remains the same. This is likely to increase the current
draw very significantly, which may cause electrolyte boiling and
other problems.
PWM current limiting
The best way to limit the current is to
use PWM or pulsed DC and to adjust the duty cycle to maintain the
average current. A fairly straight forward way is to use a Hall
effect current transducer (such as LEM LTS25-NP), which outputs a
voltage proportional to the current and use this as a feedback to a
PWM controller chip (TL494) to adjust the PWM duty cycle. For the
switch FET IRFZ44 (N-channel 17.5m? 49A, placed between electrolyzer
negative and ground, switched on with positive voltage) or IRF9Z34
(P-channel 140m? 18A, placed between electrolyzer positive and
battery positive, switched on with negative voltage) may be
used.
For the PWM controller
a ready made DC motor speed control unit
will do fine. It usually has a potentiometer to adjust the duty
cycle, which can be replaced by circuitry to automatically adjust
the duty cycle based on measured current draw. If automatic set-and
-forget operation is not required, the PWM controller may be used to
control the electrolyzer current draw manually.
For most accurate current limiting the
RMS current value may be calculated with for example MX536A or
AD536A True RMS-to-DC converter chips.
For minimum parts count a microcontroller
(e.g. Atmel AVR series) may be used with the Hall effect transducer
output routed to the AD converter input and the duty cycle
adjustment and RMS current calculation performed in software. The
switch FET may be directly driven with the microcontroller.
Capacitive current limiting
Capacitive current limiting
(Figure 13) may be used for electrolyzers powered by rectified AC.
It is based on putting a capacitor in series between the AC source
and the bridge rectifier. The reactance of the capacitor will limit
the current to a certain value, but will not dissipate any power
like a current limiting resistor.
The capacitor must be suitable for AC use
(not an electrolytic capacitor). For mains-powered operation power
-factor correction capacitors are the best. This is best suited for
welders operating on mains power (no heavy transformer needed) or
hydroboosters running on modified alternators (diodes removed). You
can use any number of cells (even one), but you need to figure about
2.0V per cell minimum. For 230VAC 50Hz you need about 14uF for each
Amp.
Figure 13. Capacitive current
limiting
Output measurements:
Run #7: (3rd Aug 2005)
Electrolyte drain-cleaner grade 93% pure
Potassium Hydroxide or KOH pellets in medical grade purified water.
Concentration 28% KOH and 72% water by weight. 500 grams of
electrolyte (about 450ml volume) was mixed and poured into the
electrolyzer. The electrolyzer was allowed to run without collecting
gasses for a few hours. During this time the electrolyte temperature
stabilized at 45C while the ambient temperature was 17C.
The gas production rate was measured by
collecting the gas in a 0.5L coke bottle filled with water. The
weight of the bottle with water was measured. The bottle filled with
water was turned upside down while partly submerged in a cold water
bath. The gas was allowed to bubble through the water bath to the
bottle and the time was measured. After removing the gas hose and
stopping the timer the cap of the bottle was screwed on while still
under water and the weight of the bottle filled partly with water
and partly with gas was measured. The weight difference between
start and end weights was recorded, as the weight difference in
grams corresponds to the volume of produced gas in milliliters. The
production rate was found to be 475ml in 30 seconds, which
corresponds to 57 LPH (liters per hour).
The cell was powered by a current limited
(11A limit) battery charger. The voltage and current across the
electrolyzer were measured to be 12.9 V and 11 A during the gas
collection. Thus the input power was 141.9 W.
At room temperature the Faraday
efficiency would be 0.684 LPH/A per cell. This electrolyzer should
produce about 0.684LPH/A*11A*7 = 52.6 LPH, but it produces about
57LPH. This difference is most likely explained by the gas volume or
current measurement inaccuracy.
The power efficiency was determined by
dividing the total power consumption by the amount of gas produced.
This is 141.9W / 57 LPH = ~2.49 W/LPH. The 100% efficient
electrolyzer (gas volume measured at room temperature) would be
about 1.48V/0.684LPH/A = 2.16W/LPH. Thus this electrolyzer has about
86.7% efficiency.
However, the cell voltage was 12.9V/7 =
1.84V. Thus the actual total efficiency is 1.48V/1.84V = ~80%.
Running internal combustion engines on
oxyhydrogen
The amount of oxyhydrogen needed to run
an internal combustion engine is spectacular. Idling a small engine
(e.g. 5hp) would require 500 -1000 LPH (liters per hour), while
idling a car engine would probably consume about 3000LPH of
oxyhydrogen. Driving down the highway would probably consume
20000-30000 LPH of oxyhydrogen. The electrolyzer shown in this
report produced approximately 57LPH at 11A, which is not enough to
idle even the smallest 4-stroke engine (at least 300-400LPH would be
required to idle a small 1hp brush cutter 4-stroke).
One liter of gasoline contains
approximately 30MJ of energy, while oxyhydrogen gas would contain
approximately 7- 8kJ per liter. This means that you would need
approximately 4000 liters oxyhydrogen for each liter of gasoline
your engine currently uses, assuming the engine efficiencies are
approximately the same on oxyhydrogen than on gasoline.
Thus if your car uses 6 liters of
gasoline per hour while driving down the highway, prepare for 24000
LPH oxyhydrogen consumption. Assuming a super-efficient series cell
electrolyzer (2.5 W per LPH) you would need 60kW of electrical
energy to run the electrolyzer. This corresponds to about 80hp,
which is significantly more than the amount of engine power used at
highway speeds (~20hp) . Figuring in the alternator efficiency
(~50%) you would actually need 160hp on the engine shaft to produce
24000LPH of oxyhydrogen gas.
How about a 100cc scooter powered by a
60-cell series electrolyzer running of an 120V inverter and bridge
rectifier powered by the 12V battery? Estimated gasoline consumption
while riding at 70km/h would be about 1LPH gasoline, which would
convert to about 4000LPH of oxyhydrogen consumption. Idling the same
scooter would probably take 500-1000LPH. The 60 -cell electrolyzer
would produce about 40 LPH per Amp measured at room temperature.
Thus you would need 100Amps thru the 60-cell to produce 4000LPH.
Because the electrolyzer has 60 cells, you need to power it with
about 120Vdc (assuming 2.0V cell voltage) from the inverter.
Assuming 100% efficient inverter, it would draw 1000 Amps from the
12V battery to produce 120Vdc 100A. If the scooter had a fully
charged 5Ah battery it would last for 18 seconds at 1000A until it
would run out. The scooters ?alternator? would produce probably
about 5A maximum.
A common misconception is to think that
you can dilute oxyhydrogen gas with air and run the engine with very
small amounts of gas. Oxyhydrogen gas is in itself a perfectly
proportioned mixture of hydrogen and oxygen gasses, which combusts
perfectly leaving no hydrogen or oxygen but only water vapor and
heat. Adding any air will make it combust imperfectly and release
less energy for same volume of gas.
An often quoted air:fuel ratio for
hydrogen combustion in air is 34:1, but this is a MASS ratio. This
means that you need 34 grams (=27.76 liters) of air for each gram of
hydrogen (=11.1 liters). Converted to VOLUME ratio this is 2.5:1,
which makes perfect sense because air contains approximately 20% of
oxygen by volume and you need 0.5 liters of oxygen for each liter of
hydrogen. Thus you need 2.5 liters of air for each liter of hydrogen
for perfect combustion (leaving nitrogen and other atmospheric trace
elements).
Assuming the engine has 100% volumetric
efficiency, a 2.0L auto engine running at 2500RPM would have have a
total air intake flow of 150000LPH. Running this engine fully
unthrottled at 2500RPM to produce the maximum power would take about
43000LPH of hydrogen gas and 107000LPH of air for stoichiometric
operation. The 43000LPH of hydrogen contains about
43m^3/h*2.8kWh/m^3 = ~120kW of power. Assuming 25% engine efficiency
you would get about 30kW or 37hp shaft horsepower.
Figure 14 shows the experimental setup
that was used for idling a 6.5hp 200cc 4- stroke Honda copy on
oxyhydrogen gas. The electrolyzer did not produce enough oxyhydrogen
to run the engine continuously, but the oxyhydrogen gas was first
collected in a balloon and then used to run the engine. The 7-cell
unit was used, powered by a current limited welding transformer
running at about 40A producing approximately 200 LPH of gas. The gas
was collected for 1-2 minutes which later ran the engine for some 20
seconds. Approximately 600-800LPH of gas would have been needed to
idle the engine continuously. The engine timing was not changed in
any way. The electrolyzer gas output tube was routed to a propane
adapter bolted at the intake of the carb. The oxyhydrogen was
admitted thru a narrow (1-2mm) orifice to the intake of the
carburetor. The engine ran fully choked, with no outside air used at
all. The engine would not run without the narrow orifice or without
being fully choked.
Figure 14. 6.5hp 200cc 4-stroke running
on electrolytic gas
Implosion
There is a common misconception that when
the engine runs on oxyhydrogen it operates by imploding the
oxyhydrogen gas in the cylinders supposedly creating a vacuum that
pulls the cylinders up, thus requiring altered engine timing.
One mole of water (~18ml) turns into 33.6
liters of oxyhydrogen gas. Thus you get about 1860 liters of
oxyhydrogen for each liter of water, and correspondingly one liter
of oxyhydrogen turns into 1/1860 = 0.53 milliliters of water.
But you only get a vacuum if the produced
water vapor (steam) can condense, and you only get condensation if
the combustion chamber is very cold. Steam will not condense on the
hot cylinder walls of the engine and you won?t get a vacuum in the
cylinders as a result of oxyhydrogen combustion.
One mole of water (~18ml) will turn into
33.6 liters of oxyhydrogen at 0 deg C, but when the oxyhydrogen is
combusted it will turn into 100 deg C steam. Assuming the steam is
at 1 atm pressure, it will occupy a volume of about 30.6 liters (one
mole of 100 deg C steam).
In reality the oxyhydrogen gas combusts
in the engine just as any gas (even though the flame front proceeds
quite fast), creating a rapid pressure/heat increase which then runs
the engine.
Protect and repair your engine from
hydrogen
embrittlement by using a ceramic
treatment.
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