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Effects of hydrogenation of fossil fuels with
hydrogen and hydroxy gas on performance and
emissions of internal combustion engines
Kadir Aydin
a,b,*
, Raif Kenano
glu
a,b
a
C¸ ukurova University, Faculty of Engineering, Department of Automotive Engineering, Turkey
b
_
Iskenderun Technical University, Faculty of Engineering, Department of Mechanical Engineering, Turkey
article info
Article history:
Received 30 November 2017
Received in revised form
28 March 2018
Accepted 4 April 2018
Available online xxx
Keywords:
Hydroxy
HHO-CNG
Performance and emissions
Pilot injection
Internal combustiosn engine
abstract
Energy security is an important consideration for development of future transport fuels.
Among the all gaseous fuels hydrogen or hydroxy (HHO) gas is considered to be one of the
clean alternative fuels. Hydrogen is very flammable gas and storing and transporting of
hydrogen gas safely is very difficult. Today, vehicles using pure hydrogen as fuel require
stations with compressed or liquefied hydrogen stocks at high pressures from hydrogen
production centres established with large investments.
Different electrode design and different electrolytes have been tested to find the best
electrode design and electrolyte for higher amount of HHO production using same electric
energy. HHO is used as an additional fuel without storage tanks in the four strokes, 4-
cylinder compression ignition engine and two-stroke, one-cylinder spark ignition engine
without any structural changes. Later, previously developed commercially available dry
cell HHO reactor used as a fuel additive to neat diesel fuel and biodiesel fuel mixtures. HHO
gas is used to hydrogenate the compressed natural gas (CNG) and different amounts of
HHO-CNG fuel mixtures are used in a pilot injection CI engine. Pure diesel fuel and diesel
fuel þbiodiesel mixtures with different volumetric flow rates are also used as pilot in-
jection fuel in the test engine. The effects of HHO enrichment on engine performance and
emissions in compression-ignition and spark-ignition engines have been examined in
detail. It is found from the experiments that plate type reactor with NaOH produced more
HHO gas with the same amount of catalyst and electric energy. All experimental results
from Gasoline and Diesel Engines show that performance and exhaust emission values
have improved with hydroxy gas addition to the fossil fuels except NO
x
exhaust emissions.
The maximum average improvements in terms of performance and emissions of the
gasoline and the diesel engine are both graphically and numerically expressed in results
and discussions. The maximum average improvements obtained for brake power, brake
torque and BSFC values of the gasoline engine were 27%, 32.4% and 16.3%, respectively.
Furthermore, maximum improvements in performance data obtained with the use of HHO
enriched biodiesel fuel mixture in diesel engine were 8.31% for brake power, 7.1% for brake
torque and 10% for BSFC.
©2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
*Corresponding author.C¸ ukurova University, Faculty of Engineering, Department of Automotive Engineering, Turkey.
E-mail address: kdraydin@cu.edu.tr (K. Aydin).
Available online at www.sciencedirect.com
ScienceDirect
journal homepage: www.elsevier.com/locate/he
international journal of hydrogen energy xxx (2018) 1e12
https://doi.org/10.1016/j.ijhydene.2018.04.026
0360-3199/©2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Aydin K, Kenano
glu R, Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on
performance and emissions of internal combustion engines, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/
j.ijhydene.2018.04.026
Introduction
In recent years, the threat of environmental security and
global warming has been taken into account by the vast ma-
jority of scientists and numerous studies have been under-
taken to slow down or stop the adverse effects of these factors
[1e10]. Due to the depletion of fossil fuel sources and harmful
environmental effects of their utilization, sustainable energy
sources and energy carriers have become an important sub-
ject and hydrogen will have a crucial role to reduce de-
pendency of fossil fuels [11e14]. When emissions are
considered, it is known that hydrogen or hydroxy (HHO) gas is
the cleanest source of energy among all alternative fuels.
Hydroxy Gas (HHO) is formed by separating the atoms in the
water molecule by electrolysis (theoretically 67% H and 33% O)
as understood from the abbreviation [15]. Its calorific value is
extremely high with respect to diesel and gasoline. For
instance, the calorific value of 1 kg of HHO is 3 times and 3.2
times greater than gasoline and diesel fuel, respectively [16].
Dincer, I. [17], expressed that the most effective method
known for producing almost pure hydrogen is water elec-
trolysis. The electrolysis phenomena were discovered by Sir
Anthony Carlisle and William Nicholson in early 1800s. They
used a pair of conducting wires to connect electrodes of the
Volta battery and the other ends immersed separately in the
saline solution. As a result, hydrogen and oxygen have begun
to accumulate at the tip of the electrode due to the water
acting as a conductor [18]. There are three main different
types of electrolysis, such as alkaline water, solid oxide and
PEM (polymer electrolyte membrane) water electrolysis [19].
Three major issues, low partial load range, limited current
density and low operating pressure, are related with alkaline
electrolyzers. In this study, alkaline water electrolysis method
was used. SOECs (solid oxide electrolyzer cells) gain impor-
tance because while they are producing hydrogen with high
efficiency, they can convert electrical energy into chemical
energy. PEMs discovered by Grubb, and they used solid sul-
fonated polystyrene membrane as an electrolyte [20,21].Itis
known as water electrolysis by proton exchange membrane or
polymer electrolyte membrane. Besides, they called solid
polymer electrolyte (SPE) water electrolysis rarely [19].
PEMs also used as a fuel cell. Fuel cells operate with pure
hydrogen gas, natural gas and biogas fuels. The ability of fuel
cells to be used in vehicles varies according to their power
generation capacity [22]. In the USA, Fuel cells have been
studied for use with hydrocarbon fuels depending on the
operating temperature of 500e800 C[23e25]. Granovskii et al.
[26] fuel cells stacks and ion conductive membranes applica-
tions on gas turbine cycles allow increasing electricity gener-
ation efficiency and decreasing air pollution emissions.
In recent years, exhaust emissions, which play a significant
role in the hole of the ozone layer and in global warming, have
been restricted by various agreements. Because of these sit-
uations, many researchers have tended to alternative fuels in
internal combustion engines. Although many alternative fuels
have been tried by these researchers, it appears that alterna-
tive fuel with the best performance is hydrogen. Hydrogen has
many advantages over fossil fuels. The absence of carbon and
other harmful substances in the first place and the abundance
of compounds in nature are some of these. All exhaust
emissions, except nitrogen, can be regulated by using
hydrogen as a fuel. The fuel properties of hydrogen are given
in Table 1 [27].
Pure hydrogen could be used as a fuel in S.I. engine solely
with higher efficiency and higher power outputs [28]. But there
are some severe disadvantages of using hydrogen as a fuel in
S.I. engine e.g. engine knock, pre-ignition and NO
x
emission
[29]. The using of hydrogen as an alternative in C.I. engines is
defined as a new concept. Due to the high ignition tempera-
ture (858K) hydrogen cannot be ignited without any spark or
additives. The methods of hydrogen usage in CI engines are air
enrichment with hydrogen, directly injection into the intake
system and in-cylinder injection [30].
Other researchers have examined the use of hydrogen,
natural gas and their mixtures in internal combustion engines
in terms of second law analysis [31]. Rakopoulos et al. were
investigated the exergy efficiency of hydrogen and natural gas
fuel blends for direct injection CI engine. The results showed
that as the engine load increased, the irreversibility genera-
tion of the engine decreased [32].
Many studies have performed on dual fuel engines to
investigate performance and emission characteristics of
different alternative energy sources with diesel as a pilot
source of ignition. Saravanan et al. used hydrogen as a source
of energy and diesel as a source of ignition in their work. Their
results indicated that CO, CO
2
and HC values were reduced at
negligible concentrations, although engine efficiency was
increased [27]. Shitole at al. used HHO gas for the air enrich-
ment in C.I. engine by 1 lpm. Their results were indicated that
thermal efficiency, power and specific fuel consumption
values were improved however, NO
x
formation was increased
due to high flammability of hydrogen [33]. Verde and Frame
performed a research about dual fuel mode. They obtained
some improvements of performance parameters.
Kumar et al. investigated the combustion process effects of
hydrogen enrichment on single-cylinder diesel-engine using
biodiesel from vegetable oil in their study. The experimental
results showed that the brake thermal efficiency was
improved by 2% when used 7% of hydrogen by mass at
Table 1 eThe properties of hydrogen.
Properties Diesel Unleaded
gasoline
Hydrogen
Autoignition temperature (K) 530 533e733 858
Minimum ignition energy (mJ) e0.24 0.02
Flammability limits
(volume % in air)
0.7e5 1.4e7.6 4e75
Stoichiometric airefuel
ratio on mass basis
14.5 14.6 34.3
Limits of flammability
(equivalence ratio)
e0.7e3.8 0.1e7.1
Density at 16 C and
1.01 bar (kg/m
3
)
833e881 721e785 0.0838
Net heating value (MJ/kg) 42.5 43.9 119.93
Flame velocity (cm/s) 30 37e43 265e325
Quenching gap in NTP air (cm) e0.2 0.064
Diffusivity in air (cm
2
/s) e0.08 0.63
Research octane number 30 92e98 130
Motor octane number e80e90 e
international journal of hydrogen energy xxx (2018) 1e122
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glu R, Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on
performance and emissions of internal combustion engines, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/
j.ijhydene.2018.04.026
maximum power output. Smoke was reduced by 0.7 Bosch
smoke unit (BSU). Although HC and CO emissions were
reduced 130 to 100 ppm, respectively, NOx formations
increased by 19.2% [34].
Samuel and McCormick, performed their study with the
addition of hydrogen-oxygen mixture obtained by the water
electrolysis. The concentration of NO
x
in emission was
reduced to 17.9% by using 1.5 lpm of the hydrogen-oxygen
mixture. However, when the mixture supply was increased
to 2.8 lpm, NO
x
emission increases [35]. Saravanan and
Nagarajan [36] made an investigation on the hydrogen-
enriched air induction in a diesel engine. The results indi-
cated that in experiments with 30% hydrogen enrichment,
motor efficiency increased by 27.9% over the entire load range
without knocking. Also, they expressed that specific fuel
consumption values were decreased by increasing the
amount of hydrogen for all operation range.
When gas fuels are used in the mixture, the gases forming
the mixture show their properties in the mixture to the extent
they are involved [37]. Also, hydrogen can also be used as a fuel
mixture with another gaseous fuel. Naglingam et al. [38] the
hydrogen-natural gas fuel mixture has a higher burning ve-
locity compared to natural gas use alone and therefore it has
been proved that higher torque can be obtained with lower
spark advance. This burning rate can improve engine effi-
ciency nevertheless; it caused that increasing of NOx emis-
sions because of higher temperatures obtained during
combustion [39e42]. Arat et al. [43] performed their experi-
ment with a conventional compression ignition engine with
HHO-CNG fuel mixture enrichment without any structural
changing on the test engine. They obtained significant outputs
about performance and emission values. All performance data
in their study, power, torque and BSFC, were improved by
using HHOCNG enriched diesel fuel with the rate of 4.7%, 6.75%
and 17.2%, respectively. Also, related studies in the literature
are matching with these improvements values [35,43e49].
Hydroxy gas is used with biodiesel, which is another
alternative energy source, for enrichment [50e52]. Baltacioglu
at al [37]. conducted their experiments with HHO enriched
sunflower biodiesel. The main purpose of the experiments is
to compare performance and emission characteristics of pure
hydrogen and HHO enriched biodiesel fuels in a pilot injection
diesel engine. The amount of hydrogen fuel given to the test
engine during the experiments was set at 10 L/min. The re-
sults will be discussed in the results and discussion section.
Fig. 1 ePlate type (a), Cylindrical type (b) and Wire type (c) electrodes used in this study.
Fig. 2 eCommercial HHO reactor system.
Table 2 eTest engine specifications.
Brand Mitsubishi
Model 4D32 - In line 4
Displacement 3567 cc
Bore Stroke 104 mm 105 mm
Max. Power 89 kW (at 3200 rpm)
Max. Torque 295 Nm (at 1800 rpm)
Fig. 3 eMixing chamber of gaseous fuels.
international journal of hydrogen energy xxx (2018) 1e12 3
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glu R, Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on
performance and emissions of internal combustion engines, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/
j.ijhydene.2018.04.026
Fig. 4 eGeneral view of second part of experimental setup.
(a) (b)
(c) (d)
0
1
2
3
4
5
6
7
00.511.52
Production of HHO (L/min)
MASS FRACTION,%
Plate Reactor
NaOH NaCl KOH
0
1
2
3
4
5
6
7
00.511.52
Production of HHO (L/min)
MASS FRACTION,%
NaOH NaCl KOH
Cylindrical Reactor
0
1
2
3
4
5
6
7
00.511.52
Production of HHO (L/min)
MASS FRACTION,%
NaOH NaCl KOH
Wire Reactor
0
1
2
3
4
5
6
7
0 0.5 1 1.5 2
Production of HHO (L/min)
MASS FRACTION,%
Comparison of Different Reactor with NaOH
Plate Reactor
Cylindrical Reactor
Wire Reactor
Fig. 5 eDifference of HHO flow rates using Plate (a), Cylindrical (b) and Wire (c) type reactors with catalyst mass fraction and
comparison of different reactors HHO production with NaOH catalyst (d).
international journal of hydrogen energy xxx (2018) 1e124
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glu R, Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on
performance and emissions of internal combustion engines, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/
j.ijhydene.2018.04.026
Material and method
This experimental study which is composed of the perfor-
mance and emission characteristics of HHO gas fuel used as
fuel enrichment in internal combustion engines and HHO
production is investigated into two parts.
In the beginning of the first part, HHO is produced by
electrolytes of KOH, NaOH and NaCl with plate, cylindrical
and wire type electrodes in a leak-proof Plexiglas reactor.
Firstly, the HHO, which is used in diesel and gasoline en-
gines, is sent to the intake manifold after passing through a
security tank to prevent backfire after production. The sensors
are placed in the production container to monitor the increase
in temperature and pressure during HHO production. The
pressure increment of the container was regulated and pro-
tected by using the non-turn valve. To observe the probable
hydrogen leakage an electronic hydrogen leak detector is used
(see Fig. 1).
In the second part of experimental study is also explained
by figures in detail. The commercially available dry cells were
used to produce HHO as it is given in Fig. 2. As seen from the
figure, The HHO system consists of a solution tank, a filter, and
a led display showing the current to the plate during elec-
trolysis. These dry cells have 14 plates and they connected in
parallel each other.
Fuel pump plunger of the test engine is modified to run
pilot injection mode to ignite CNG without adding ignition
Fig. 6 eThe schematic diagram of the HECU and The photograph of HECU.
0
2
4
6
8
10
0 1000 2 000 3000 4000 5000 6000
Torque (Nm)
Engine Speed (rpm)
Gasoline Gas+HHO+HECU
Fig. 7 eVariation of brake torque with engine speed.
900
1100
1300
1500
1700
1900
0 1000 2000 3000 4000 5000 6000
SFC (g/kWh)
Engine Speed (rpm)
Gasoline Gas+HHO+HECU Gasoline Gas+HHO+HECU
Fig. 8 eVariation of SFC with engine speed.
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glu R, Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on
performance and emissions of internal combustion engines, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/
j.ijhydene.2018.04.026
system and spark plug into the engine cylinders. The amount
of liquid fuel injected into the cylinders is reduced by 15%e
30% via fuel pump plunger.
In this experimental study, the gaseous fuels used as
substitute fuels were mixed at certain ratios before they were
taken into the cylinder. CNG gas is mixed up with 15%, 25%
and 35% (by volumes) hydrogen and HHO in the mixing
chamber before entering to the intake manifold of the test
engine as shown below in Fig. 3. Performance and emissions
tests were performed with different amount of liquid fuels
(diesel fuel and biodiesel) and hydrogenation ratios of CNG.
A water cooled, 3.6 L, four stroke, direct injection
compression ignition engine, the main component of this
study, was used in all tests. The specifications of this engine
are given in Table 2. A hydraulic dynamometer was used to
apply the required load during the tests. The MRU Delta 1600 V
gas analyzer was used to determine the effect of fuels on
exhaust emissions, to determine the extent of exhaust
6500
7000
7500
8000
8500
9000
0 1000 2000 3000 4000 5000 6000
HC (ppm)
Engine Speed (rpm)
Gasoline Gas+HHO+HECU Gasoline Gas+HHO+HECU
Fig. 9 eHC Emissions vs. engine speed.
0
2
4
6
8
10
0 1000 2000 3000 4000 5000 6000
CO (vol%)
Engine Speed (rpm)
Gasoline Gas+HHO+HECU Gasoline Gas+HHO+HECU
Fig. 10 eVariation of CO Emissions with engine speed.
Fig. 11 eVariation of Brake Torque with engine speed.
800
1000
1200
1400
1600
1800
1000 1500 2000 2500 3000
SFC (g/kWh)
Engine Speed (rpm)
Diesel+HHO+HECU Diesel Diesel+HHO+HECU Diesel
Fig. 12 eVariation of SFC with engine speed.
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j.ijhydene.2018.04.026
emissions. Data logger was used to collect performance out-
puts of dynamometer, sensors, flowmeters and exhaust gas
outputs of gas analyzer. The whole experimental setup is
presented in Fig. 4 schematically.
Results and discussion
This study was formed as two parts. The first one is about HHO
production by using different electrolyte types and different
3
4
5
6
7
8
9
1000 1500 2000 2500 3000
CO (vol %)
Engine Speed (rpm)
Diesel+HHO+HECU Diesel Diesel+HHO+HECU Diesel
Fig. 14 eCO Emissions vs. Engine speed.
7000
7300
7600
7900
8200
8500
1000 1500 2000 2500 3000
HC (ppm)
Engine Speed (rpm)
Diesel+HHO+HECU Diesel Diesel+HHO+HECU Diesel
Fig. 13 eHC Emissions vs Engine speed.
Fig. 15 ePerformance values, Brake Power (a), Brake Torque (b) and BSFC (c) vs. Engine Speed.
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glu R, Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on
performance and emissions of internal combustion engines, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/
j.ijhydene.2018.04.026
catalytic and its performance and emission analysis in both
spark ignition (SI) and compression ignition (CI) engines.
Other part of this section consists of the performance and
emission analysis by using different hydrogenation ratio of
CNG.
Comparison of different types of reactor and catalyst on
HHO production
In the first part of this experimental study, it is found from
the experiments that plate type reactor with NaOH pro-
duced more HHO gas with the same amount of catalyst and
electric energy. Similarly KOH is another alternative catalyst
because of hydrogen and oxygen contents of NaOH pro-
duces more HHO gas against NaCl. Manufacturing of plate
type reactor is easier and cheaper than other types of re-
actors, therefore plate type dry cell HHO reactor is devel-
oped for commercial manufacturing. The HHO production
characteristics of all types of reactors were obviously given
in Fig. 5 [53].
Additionally in Fig. 5, different reactors used during the
experiments with NaOH catalyst, which provides the best
HHO production among all catalyst types, were compared in
terms of HHO production rate.
Performance and Emission Results of HHO Enrichment with
HECU in Internal Combustion Engines
It was observed from experiments, the flow rate should be
decreased due to adverse effects of hydrogen on volumetric
efficiency [55] when the engine speed reached under the
critical values, which are 2500 rpm and 1750 rpm, for CI and SI
engines, respectively. However, an electronic control unit
connected to the HHO system was designed and coupled to
the system in order to avoid the decrease in volumetric effi-
ciency. This control unit was designed and manufactured to
regulate HHO production by reducing the voltage and current
supplied to the system as seen from Fig. 6 [53].
The experimental results with HHO þHECU (Hydroxy gas
Electronic Control Unit) were investigated in detail in internal
combustion engine. In this experimental study with HECU,
gasoline (SI) and diesel (CI) engines were used for tests. Firstly,
the SI engine results were given by graphs. It is obviously seen
from Fig. 7, engine torque was improved by 32.4% an average by
using HHO þHECU, and the engine power was also increased
27% with respect to pure gasoline operation. The extra oxygen
in the HHO and the HHO - air mixture in the cylinders caused
the fuel to burn better, thus enhancing the engine power.
It is also see that from Fig. 8, an average improvement is
16.3% for Brake Specific Fuel Consumption (SFC) by using HHO
system. The reduction in SFC is due to the fact that the extra
Fig. 16 eEmission values, CO
2
(a), CO (b) and NO
x
(c) vs. Engine Speed.
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j.ijhydene.2018.04.026
oxygen present in the HHO gas enhances the combustion ef-
ficiency and the HHO provided more homogeneous mixture
with air, because of its high diffusivity.
Similiar improvements were measured for emission
values. As can be seen in Fig. 9, HC emissions were reduced by
6.7% on average compared to pure gasoline operating condi-
tions. The oxygen in the HHO plays an effective role in
reducing the HC emissions that are evolved by improving the
combustion. At low speeds, however, HHO reduces the volu-
metric efficiency and therefore does not get enough air to burn
the cylinders and causes increased HC emissions.
When compared to pure gasoline oparation, CO emis-
sions were reduced 14.4% by using HHO as shown in Fig. 10.
The major reason of this reduction is the carbon free HHO
addition to the cylinder. It appears that CO emissions were
rising while approaching low speeds. If the HHO flow is not
regulated according to the engine speed, the increasing of
the CO will continue to appear as the engine speed
decreases.
The experimental results with CI engine have shown that
the performance of HHO improves performance and emis-
sions even though it shows different characteristics with
gasoline engine tests. It is seen from Fig. 11, the engine torque
was increased by using HHO system an average of 19.1%
compared to standard diesel operation. The engine power was
also increased 27% with respect to standard diesel operation
because of the extra oxygen concentration of HHO and better
combustion.
Also similar improvements were obtained for specific fuel
consumption. An average improvement of 14% was obtained
by using HHO system. It has also shown as Fig. 12. The
reduction in SFC is thanks to the extra oxygen present in the
HHO gas and because of high diffusivity of the HHO provided
more homogeneous mixture with air, enhanced the combus-
tion efficiency.
It is seen that from Fig. 13, HC emissions were reduced in
average 5% at above the engine speed of 1750 rpm. Because of
both the opening time of the valves was short and the
hydrogen covered high volume, sufficient air can not be taken
into the cylinders at high revs. As a result, combustion effi-
ciency was reduced by inadequate combustion.
The last figure of the first part is given below as Fig. 14.CO
emissions were reduced in average 13.5% at higher engine
speeds than 1750 rpm. The major reason of this reduction is
the carbon free HHO addition to the cylinder.
Performance and Emission Results of hydrogen and HHO
enriched biofuels
The second part of this study was composed of performance
and emission analysis and comparison of HHO and H
2
usage
as a fuel enrichment with different ratios in compression
ignition engine. The performance and emisisons results
were given by graphs. The brake power results was shown in
Fig. 15(a), an average improvement of 10 L/min HHO
Fig. 17 ePerformance values, Brake Torque (a), Brake Power (b) and BSFC (c) vs. Engine Speed for qpd operations.
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j.ijhydene.2018.04.026
enrichment of B10 fuel was 8,31% according to neat diesel
fuel.
It is well known criteria that; hydrogen shows spectacular
combustion characteristics like flame speed and higher
heating value during combustion compared to liquid fuels.
So, brake torque outputs were improved in all cases of this
study by using hydrogen and HHO enriched fuels according
to neat diesel fuel and B10. The torque results were given by
graph 15(b).
Hydrogen is one of the most impressive alternative fuels in
terms of heating value. Although the heating value of the
biodiesel is lower than the standard diesel, the hydrogen-
enriched biodiesel fuel also reduced specific fuel consump-
tion due to its high performance outputs. The decrement of
H
2
þB10 was 2% as well as HHO þB10 fuel provided 10% in
average as seen from Fig. 15(c).
When considering the emission values, CO
2
emission
values were reduced with hydrogen-enriched biodiesel fuel at
low engine speeds (between 1200 and 1800 rpm) compared to
greater than these interval as seen from Fig. 16(a). The im-
provements of emission values 2% and 10% in average for
B10 þH
2
and B10 þHHO, respectively.
The almost similar characteristics were observed for the
use of B10 þH
2
and B10 þHHO in terms of CO emissions.
Although both fuels achieved decreasing of CO however, there
was a different between CO gas emissions outputs of H
2
þB10
fuel and the HHO þB10 fuel. Better reduction of CO emission
was obtained with B10 þH
2
fuel compared to the B10 þHHO
by 5.8% in average. Compared to standard diesel operation,
B10 þH
2
fuel provides maximum improvement with 38%
reduction in 2300 rpm. as shown in Fig. 16(b). NOx formation
was increased with B10 þH
2
and B10 þHHO due to use of
hydrogen as a fuel enrichment during combustion. NO
x
emissions were increased 20% and 16% in average by using
HHO þB10 and H
2
þB10 fuels, respectively. The results were
given in Fig. 16(c).
Another experimental results of this study are about
gaseous fuel enrichments with diesel or biodiesel pilot
injectioninCIengine[54]. All performance datas were
given by graphs. HHOCNG additives improved the torque
values compared the CNG þqpd (quarter pilot diesel in-
jection) and neat diesel operation. It is seen from the
Fig. 17(a), HHO provides better performance output by
improving the combustion efficiency with its extra oxygen
content. The average improvement of brake torque values
were 0.78%, 4.78% and 1.02% for 20, 25 and 30 HHOCNG
respectively.
The brake power values showed similar characteristics
with brake torque values. Average brake power improvements
were 0.88%, 4.4% and 1.3% for 20, 25 and 30 HHOCNG respec-
tively, as seen from Fig. 17(b). The use of HHO provides better
performance output by improving the combustion efficiency
with its extra oxygen content.
As it is evidently seen from Fig. 17(c), CNG and HHOCNG
mixtures were decreased the BSFC with 19.2%, 18.3%, 16.3%,
15.1% for CNG, 20, 25 and 30 HHOCNG respectively. The major
Fig. 18 ePerformance values, Brake Torque (a), Brake Power (b) and BSFC (c) vs. Engine Speed for spd operations.
international journal of hydrogen energy xxx (2018) 1e1210
Please cite this article in press as: Aydin K, Kenano
glu R, Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on
performance and emissions of internal combustion engines, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/
j.ijhydene.2018.04.026
reasons for these reductions are the use of gaseous fuel
instead of diesel fuel and the lower density of the gaseous
fuels than diesel fuels. And also, the hydrogens of HHO cause
to increase combustion temperature and pressure.
It is obviously seen that; HHO provides better performance
output by improving the combustion efficiency with its extra
oxygen content. Fig. 18(a) represents the improvements of
brake torque values were 0.8%, 4.4% and 1.2% for 20, 25 and 30
HHOCNG respectively, for semi pilot diesel injection (spd)
operations.
The brake power values showed similar characteristics
with brake torque values. Brake power graph is given as
Fig. 18(b); average brake power improvements were 1.18%,
3.15% and 1.09% for 20, 25 and 30 HHOCNG respectively.
It is obviously CNG and HHOCNG mixtures were improved
the BSFC with 26.2%, 22.3%, 20.3%, 19.1% for CNG, 20, 25 and 30
HHOCNG respectively. The BSFC results is shown from
Fig. 18(c). As the same manner with qpd operations, the major
reasons for these reductions are the use of gaseous fuel
instead of diesel fuel and the lower density of the gaseous
fuels than diesel fuels. And also, the hydrogens atoms of HHO
cause to increase combustion temperature and pressure.
Conclusion
The conclusions from the first part, HHO usage with HECU, of
this experimental study are summarized as follows:
1) The most efficient combination was determined as The
plate type electrode with NaOH-water solution for the
production of HHO. The increment of the mass fraction of
catalyst in the water directly increases the HHO flow rate.
However, when the NaOH solution in solution exceeds 1%
of the mass, the system rises to an excessive degree.
2) When the HHO system used as enrichment of diesel fuel or
gasoline, engine torque output increases at mid and higher
engine speeds according to diesel and gasoline fuelled
engine operation without HECU. HECU has to be used to
regulate the voltage and current of the HHO production by
using electrolysis at low engine speed.
3) HHO gas gives the better performance and emission char-
acteristics because of its combustion specifications, such
as extra oxygen, high burning velocity, and carbon-free
content.
The conclusions from the second part, HHO enriched bio-
fuels usage, of this experimental study are summarized as
follows:
1) All performance and exhaust emissions values have
improved with hydrogenation of HHO and H
2
except NO
x
exhaust emissions.
2) When considering the application cost and safety, HHO
fuel enrichment system is more preferable in diesel
engines.
3) This study shows the availability of using HHOCNG mix-
tures as an indicator alternative fuel in diesel engines
applications.
4) Both quarter and semi-pilot diesel injections improved the
fuel economy perspective and reduced the specific fuel
consumptions.
5) 25 HHOCNG fuel mixture with semi-pilot injection opera-
tion was obtained the best mix when used as an alternative
and additional fuel for run under this test engine.
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performance and emissions of internal combustion engines, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/
j.ijhydene.2018.04.026
