Production of syngas from agricultural residue as a renewable fuel and its sustainable use in dual fuel compression ignition engine to investigate performance, emission, and noise characteristics(2019)

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Energy Sources, Part A: Recovery, Utilization, and
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Production of syngas from agricultural residue as
a renewable fuel and its sustainable use in dual-
fuel compression ignition engine to investigate
performance, emission, and noise characteristics
Jatinderpal Singh, Sandeep Singh & Saroj Kumar Mohapatra
To cite this article: Jatinderpal Singh, Sandeep Singh & Saroj Kumar Mohapatra (2019):
Production of syngas from agricultural residue as a renewable fuel and its sustainable use in dual-
fuel compression ignition engine to investigate performance, emission, and noise characteristics,
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects
To link to this article: https://doi.org/10.1080/15567036.2019.1587053
Published online: 05 Mar 2019.
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Production of syngas from agricultural residue as a renewable fuel
and its sustainable use in dual-fuel compression ignition engine to
investigate performance, emission, and noise characteristics
Jatinderpal Singh a
, Sandeep Singha
, and Saroj Kumar Mohapatra b
a
Department of Mechanical Engineering, Punjabi University, Patiala, Punjab, India; b
Department of Mechanical
Engineering, Thapar University, Patiala, Punjab, India
ABSTRACT
In the present era, the world is in a difficult position as the prime problems, like
continuous depletion of nonrenewable energy resources at a brisk rate and
environment pollution due to emission of greenhouse gases which are
released on burning fossil fuels, are worsening day by day. Due to this, the
interest of the researchers is shifting toward the idea of alternative fuels
derived from biomasses, which are renewable in nature and eco-friendly in
contrast to the conventional fossil fuels, to reduce the dependence on exhaust-
ing nonrenewable energy sources. In the present study, agricultural residues
like cotton stalks and wheat straws are processed in a downdraft gasifier to
produce syngas through biomass gasification. The produced syngas is further
inducted in a gasifier-coupled dual-fuel compression ignition (DFCI) engine to
investigate the performance, emission, and noise characteristics of the dual
fuel engine to compare the standard diesel operation and syngas-diesel dual
fuel operation. The results during the investigation concluded that Dual Fuel
Compression Ignition (DFCI) engine works satisfactorily in dual fuel mode of
syngas-diesel. Moreover, a maximum 44.44% of reduction in diesel consump-
tion is observed with a slight decrease in indicated power by 3.49% at the
maximum loading condition. In addition to the reduction in diesel consump-
tion, the emission of nitrogen oxide was reduced by maximum of 76.74% in
dual fuel mode as compared to standard diesel operation.
ARTICLE HISTORY
Received 30 May 2018
Revised 26 November 2018
Accepted 26 December 2018
KEYWORDS
Biomass; gasification;
syngas; DFCI; GHG
Introduction
The world is approaching toward an energy crisis as the conventional resources of fuel and
energy are continuously depleting at a zippy rate. The resources like fossil fuels are diminishing
as these are overused by humans due to increase in population and industrialization (Khalil,
Mubarak, and Kaseb 2010). So the developing countries like India are suffering due to escalation
of crude oil prices on the international market. The gap between energy demand and supply is
widening day by day in such countries which is further worsening the situation for them. Thus
pressing thought is prevailing for the introduction of alternative fuels which are renewable so the
dependence on the nonrenewable fossil fuels could be reduced significantly. In addition to the
energy crisis, the environment pollution has started to become a cause of serious discussion all
over the world. The fossil fuels meet our energy demand but they pollute our environments as
well. The toxic gases and greenhouse gases (GHG) which produced by the burning of these fuels
add to the environment which changes natural composition of the environment (Murphy,
Devlin, and Mcdonnell 2014). The major potential sources of renewable and clean energy are
wind, solar, hydro, and bioenergy.
CONTACT JatinderPal Singh jatindergill@live.in House no. 278 Street no. 10 AMAN NAGAR, Patiala, Punjab. PINCODE 147003
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/ueso.
© 2019 Taylor & Francis Group, LLC
ENERGY SOURCES, PART A: RECOVERY, UTILIZATION, AND ENVIRONMENTAL EFFECTS
https://doi.org/10.1080/15567036.2019.1587053

Bioenergy or biomass-derived energy production is picking up very much attention these days. As
biomass can be found in abundance and its utilization will not only reduce the reliance on
conventional fuels like coal, etc. but also comfort the environment by reducing GHG emission to
some extent. Moreover, India being an agrarian country has large amount of biomass to utilize from
the crop residue after harvesting. According to an estimate, 40–60% of the agricultural waste is either
lost or put to inefficient use (Ghosal and Das 2010). So the agricultural fields and its waste can be
a major source of biomass and it is often termed as ligno-cellulose. Ligno-cellulose is not part of food
chain of humans, so its use in other applications will not post any threat to food supply. Examples of
such biomasses are woody plants, straws of rice and wheat, husk, and stalks of woody plants like
cotton, corn cobs (Singh 2017). These biomasses can be converted to useful energy forms by several
techniques like esterification to produce biodiesel, fermentation to produce bio-ethanol, gasification
to produce synthetic gas, etc. (McKendry 2002).
Biomass gasification and syngas has proven to possess great potential of clean sustainable energy
in the recent studies which can be a potential way out from the problem of excessive use of fossil
fuels like coal. Basically, in this process solid biomass is converted into a gaseous fuel, which is
a combustible gas called synthetic gas or syngas. Syngas is the mixture of gases like carbon monoxide
(CO), hydrogen, methane, carbon dioxide and as a whole is combustible in nature having a low
calorific value (CV) in range 4–6 MJ/Nm3
. Unlike combustion of biomass in which complete
oxidation of biomass occurs, in gasification partial oxidation of biomass is done at a temperature
about 700–900°C and produces a gas combustible in nature with some amount of tar as by-products
(Hagos, Aziz and Sulaiman 2014).
Recent advancements in area of gasification enabled the conversion of syngas into biofuels for
power generation and chemical synthesis. According to a study, the largest proportion of the syngas
produced is used for ammonia synthesis and bio-methanol generation. Moreover, recent research,
for synthesizing Fischer and Tropsch (FT) fuels that are diesel, gasoline, and heavy oils produced
from syngas processing, shown the potential of gasification in area of renewable energy sources. FT
fuels are produced by polymerization of syngas molecules in the presence of catalysts like Co and Fe
at temperature of about 200–300°C and under pressure 10–60 bar (Sikarwara et al. 2017).
The idea of power generation by dual fueling the syngas with a pilot fuel in Internal combustion
(IC) engines has been prevailing in recent times. In a study, Ghosal and Das conducted experiments
on a 5.25-kW capacity diesel engine running at constant speed by dual fueling it with syngas derived
from some underutilized biomasses and pilot fuel diesel and an average 64% of diesel substitution
was reported in the study (Ghosal and Das 2010). In another investigation, Hassan S. et al. used
supercharged syngas and diesel mixture in a 4.9-kW capacity diesel engine running at constant
3,600 rpm and reported an average 48.3% diesel substitution (Hassan et al. 2011). Nayak S.K. et al.
reported significant 80% diesel substitution in the dual fuel mode when the flow rate of the syngas
was kept 37.5 Nm3
/h; coconut shell was processed to produce syngas (Nayak, Mishra, and Behera
2017). With the improvement in fuel consumption in syngas-diesel in dual fuel engines, the better
emission characteristics have also been reported. Banapurmath and Tewari, in a study on syngas-
driven dual fuel engine, have reported significant reduction in emission of nitrogen oxide (NOX) at
all loading conditions as compared to standard diesel operation (Banapurmath and Tewari 2009).
Shrivastava V. et al. and Sahoo B.B. et al. have also reported the reduction in toxic gas emission as
the amount of air reduces in the combustion chamber which reduces the amount of nitrogen to form
oxides (Sahoo, Sahoo, and Saha 2009; Shrivastava et al. 2013). With the reduction in NOX, it has
been observed that amount of CO and hydrocarbon (HC) gets increased in syngas-diesel mode; this
is due to the fact syngas is composed of CO and CH4 which produced from the oxidation of
carbonaceous biomass. Vidian F. et al. used sawdust as a feedstock for gasification to use produced
syngas in a dual fuel diesel engine and reported an overall 50% of reduction in diesel consumption
(Vidian, Basri, and Surjosatyo 2017). Lal and Mohapatra investigated the performance and emission
characteristics at varying compression ratios and reported a maximum reduction in diesel consump-
tion of 64.3% with a significant decrease in NOX and SOX emission (Lal and Mohapatra 2017). Apart
2 J. SINGH ET AL.

from syngas, dual fueling of biogas in DFCI engines with diesel has shown promising results as well.
Mahla et al. utilized biogas in the experiments performed on a DFCI engine with biogas introduced
in the engine through inlet manifold and reported 8% reduction in brake thermal efficiency (BTE)
and 60% decrease in NOX emission in dual fuel mode as compared to standard diesel mode (Mahla
et al. 2018). The researchers have indicated the reduction in fuel consumption but other performance
characteristics of the engine on dual fueling it with syngas are vaguely discussed till now. With the
positives in the picture, gasification can provide a possible alternative to the energy problem
(McKendry 2002).
Present work
In the present study, the aim is to utilize the biomass from agricultural residue to generate
sustainable energy through biomass gasification in a downdraft gasifier and its use in dual-fuel
compression ignition (DFCI) engine is also studied. Gasification is carried out by using two different
biomasses that are cotton stalks and wheat straws to produce syngas separately. The produced syngas
is inducted into the DFCI engine working at compression ratio 18:1 to investigate the performance,
emission, and noise characteristics of the DFCI engine and to compare the results with the standard
diesel operation characteristics.
Methodology and experimental investigation
In the present study, biomass gasification is performed by utilizing agricultural residue as source of
biomass to produce syngas in a downdraft gasifier coupled with a DFCI engine. General outline of
the methodology is illustrated in Figure 1.
Preparation and characterization of biomass used
Agricultural residues such as cotton stalks and wheat straws are used as source of biomass for
feedstock of the gasifier in the reported study. The raw cotton stalks and wheat straws were air dried
for a week to reduce the moisture content below 10% and then chopped into small pieces of size
range 20–25 mm for the ease of operation. For characterization of the different biomasses used,
proximate analysis is done and CVs of the biomasses are determined by using bomb calorimeter.
Table 1 illustrates the different characteristics of the biomasses used.
Biomass collection:
agricultural residue
Preparation of feedstock:
drying and chopping
Proximate analysis &
CV analysis
Gasification of the
biomass
Coupling gasifier with CI
engine
Performance analysis
Noise level analysis
Emission analysis
Figure 1. General outline of methodology adopted for experimentation.
ENERGY SOURCES, PART A: RECOVERY, UTILIZATION, AND ENVIRONMENTAL EFFECTS 3

CVs and proximate analysis
CV is the heat energy produced by completely burning unit mass of a fuel and it is expressed in J/kg.
The CV of the biomass used is calculated by using oxygen bomb calorimeter by following standar-
dized procedure according to BS EN 14918:2009.
Proximate analysis is performed to determine the amount of moisture, volatile matter, fixed
carbon, and ash in the fuel being used. The analysis procedure is carried out according to the
standard procedure defined by National Standard Authority of Ireland, for moisture determination
CEN/TS 14774-3:2004, for volatile matter determination CEN/TS 15148:2005, and for ash determi-
nation CEN/TS 14775:2004. The results of proximate value and CV are provided in Table 1.
Gasifier system
In the reported work, a throated downdraft gasifier is used. The gasifier system included
a combustion chamber with a hopper through which feedstock is fed to the gasifier, an ash box
below the combustion chamber to collect the incombustible ash, water operated gas cooling unit to
reduce the temperature of the gas coming out of the combustion chamber, scrubber for cleaning the
gas, flare valve to check the quality of the syngas produced. The specifications of the gasifier system
are mentioned in Table 2 according to the manufacturer catalog.
Figure 2 represents the general outline of the experimental setup which includes the downdraft
gasifier, gas conditioning and cleaning components, and gasifier-coupled DFCI engine. The process
of gasification starts with feeding the biomass into the gasifier unit through the hopper at its top. In
the reported study, two different biomasses are used separately as fuel for gasifier, which are
agricultural residues; cotton stalks and wheat straws, to produce syngas. After feeding the dry
feedstock, gasifier is fired by using a torch at the air opening at the side of the reactor. After the
ignition of the feedstock, generation of syngas starts after approximately 20 min of operation.
Syngas, when leaves the gasification zone, has very high temperature of about 500°C and is
highly contaminated, contains high amount of tars, particulates like char and water soluble gases
like SO2, H2S, NH3, and HCl. Before using the syngas in an IC engine, it must be cleaned and
cooled so that it does not cause any harm to the engine. So after leaving the gasification zone, the
syngas was passed through air cleaning and cooling units. The gas first passed through a scrubber
Table 1. Calorific values and proximate analysis of wheat straws and
cotton stalks.
Properties Wheat straws Cotton stalks
Moisture content (%) 8.38 9.57
Volatile matter (%) 74.02 73.16
Ash (%) 9.49 5.43
Fixed carbon (%) 8.11 11.84
Calorific value (kJ/kg) 17,222.63 17,456.76
Table 2. Specifications of the gasifier system.
Parameters Specifications
Gasifier make Ankur scientific energy technology Pvt. Ltd.
Model WBG-10
Gasifier type Throated downdraft gasifier
Number of air inlets 2
Fuel type and size limit Woody material and agricultural waste with maximum particle size 30 mm
Capacity of the hopper 60 kg
Permissible moisture content Up to 20%
Biomass consumption rate 9–10 kg/h
Maximum gas flow rate 25 Nm3
/h
Gasification efficiency Approx. 75%
4 J. SINGH ET AL.

in which fine spray of water is used to cool the gas and condense the contaminations like tars,
water soluble gases. Then the gas from the scrubber was passed through the secondary filter which
was containing wood chips and sawdust in it. Syngas had to pass through the sawdust and wood
chips which facilitated the further cleaning of the gas by trapping the particulate matter and
moisture in them. The gas exiting secondary filter has temperature around 50°C, to certain the
proper cleaning of the gas then it was passed through a safety filter. The safety filter was made up
of filter papers inside it. Syngas had to pass through these papers which were capable of absorbing
very fine particulates. Syngas after passing through the safety filter becomes 99% clean and cools to
temperature range of 30–40°C. After cleaning and cooling the syngas, it can be fed to the IC engine
which in this case was a DFCI engine.
DFCI engine
The DFCI engine coupled with gasifier was a 3.5-kW single cylinder four stroke, water cooled diesel engine
capable of operating a variable compression ratios. The cleaned gas with a flow rate of 5 Nm3
/h from the
gasifier inducted in the combustion chamber where its combustion occurred by pilot fuel, diesel, and power
is generated. The general specifications of the DFCI engine are given in Table 3. The DFCI engines can
satisfactorily operate at variable compression ratios in range 15:1–20:1. The optimized condition at which
Figure 2. Schematic layout of experimental setup. 1: Hopper, 2: combustion zone, 3: reduction zone, 4: drain tub for ash, 5: water
supply for scrubber, 6: scrubber for cleaning and cooling of the gas, 7: drain box of scrubber, 8: secondary filter to remove tar,
particulates, and moisture, 9: safety filter for ultraclean gas, 10: bypass valve, 11: flare control valve, 12: flare burner for testing gas
quality, 13: dual fuel engine setup, 14: gas analyser for testing exhaust.
Table 3. Specifications of DFCI engine.
Parameter Specification
Engine make Kirloskar
Engine model AV-1
Engine type Variable compression ratio engine
Cylinders 1
Strokes 4
Start type Electric start
Bore 87.5 mm
Stroke 110 mm
Capacity 553 cc
Maximum power 3.5 kW at 1,500 rpm
Connecting rod length 234 mm
Compression ratio 12:1 to 18:1
Dynamometer Eddy current type
Dynamometer arm length 185 mm
Dynamometer load Mechanical load (0–120 N)
Orifice diameter 20 mm
Fuel Diesel mode and dual fuel mode
Cooling system Water cooling

DFCI engine can work is the compression ratio 18:1. At this compression ratio, DFCI engine at all loading
conditions works satisfactorily with a constant speed of 1,500 rpm (Mathur et al. 2012). So in the study,
compression ratio of dual fuel engine was kept 18:1 and syngas flow rate was kept approximately 5 Nm3
/h
and different characteristics of the engine were studied at distinct loading conditions in range 0–3 kW by an
eddy current dynamometer. The experiments were conducted only up to 85% loading conditions of the
engineloadingcapacityfor both standard dieselmode anddualfuelmode toavoidlargemechanicallossesat
higher loads. The engine characteristics were tested for dual fuel mode and standard diesel mode to compare
the results. As two different biomasses are used in the present investigation to produce syngas, the results of
three engine runs are compared for different characteristics.
Uncertainty in the results
Experiments and measurements of various parameters may involve some unwanted errors despite
the care and precautions taken to eliminate all possible sources of error. These errors cannot be
eliminated completely because of geometrical in-accuracy and measuring accuracy of the testing
apparatus. The uncertainty in the emission characteristics measured by Portable Gas Analyser ACE-
8000 is calculated to be ±1.06% and for noise characteristics measured by CESVA sound level meter
SC310 is ±0.55%. The uncertainty associated with experimental engine setup like in speed is ±0.1%
and in temperature is ±1% according the data sheets of the setup. In the experiments conducted,
there have been three trials performed for every parameter at each load. The value corresponding to
each load for every parameter has been taken as average value so as to simplify the graphical
representation as shown in Table 4.
Results and discussion
In the present study, performance, emission, and noise characteristics are analyzed for a DFCI
engine on dual fueling it with pilot fuel diesel and syngas (SG) derived from agricultural residue, i.e.
cotton stalks and wheat straws. The various characteristics of the engine in dual fuel mode are
compared with the standard diesel mode at distinct loads.
Performance characteristics
Indicated power
The variation of indicated power (IP) at different loads is illustrated in Figure 3. It is observed that the IP for
dual fuel mode is lower than the standard diesel mode at all loading conditions. This is due to the low CV of
syngas used in the dual fuel mode (Singh and Mohapatra 2018). The reduction in IP for dual fuel mode is
observed tobe3.49% and 6.60% for SG (cotton stalks) and SG (wheat straws), respectively, at 3kW load with
respect to the diesel mode. At minimum load, reduction of IP is significant than at higher loads which is
17.24% and 21.96% for SG (cotton stalks) and SG (wheat straws) respectively. This is due to improper
combustion of fuel at lower loads but as the load increases and the fuel supply increases which improves the
combustion in the combustion chamber and increases the indicated power which describes the sudden
increase in indicated power at 0.6 kW load.
Table 4. Average result from the trials for indicated power in case of dual fuel run with cotton stalks-derived syngas and
diesel.
Load (kW)
Indicated power trials (kW) 0 0.6 1.2 1.8 2.4 3.0
IP t1 1.17 2.54 3.39 3.75 4.15 4.79
IP t1 1.02 2.75 3.30 3.89 4.28 4.90
IP t1 1.08 2.60 3.42 3.88 4.29 4.72
IP avg 1.09 2.63 3.37 3.84 4.24 4.87
6 J. SINGH ET AL.

Brake thermal efficiency
Figure 4 shows the interpretation of BTE with respect to various load operations. It can be figured from the
results illustrated in the figure that the BTE in dual fuel mode is less than the diesel mode at all loading
conditions. It can be observed that BTE improves with increase in loading; it is due to incomplete
combustion at lower loads but as load increases so does the pilot fuel supply and better combustion occurs.
The maximumBTE for diesel mode is found to be 35.89%, whereasin case of dual fuel modeit isobserved to
be 26.19% and 24.39% for SG (cotton stalks) and for SG (wheat straws), respectively, so minimum reduction
in BTE in dual fuel mode is observed by approximate 27% at maximum load. The reason for reduction in
BTE in dual fuel mode canbe delineated by the fact that induction of syngasin the engine impairs the quality
of combustion and unburnt gaseous fuel exits the combustion chamber, but the BTE depends upon the fuel
burnt (Sahoo, Sahoo, and Saha 2009). It can also be observed that SG (cotton stalks) has yielded more BTE
than SG (wheat straws); this may be due to higher CV of cotton stalks as compared to wheat straws which
increases the specific energy of SG (cotton stalks) than SG (wheat straws).
Diesel consumption
The diesel consumption during the experiments is shown in Figure 5 for dual fuel operation and
standard diesel operation. It is ascertained by the figure that by dual fueling the syngas with pilot
fuel, diesel reduced the diesel consumption with respect to the standard diesel operation. It can be
observed that at all loading conditions, diesel consumption was less in case of dual fuel mode than
diesel operation. The reduction in the consumption at lower loads is found less as compared to that
at higher loads. This is due to the fact of incomplete combustion at lower loads but increase in load
improves the combustion and the fuel mixture produces better specific energy which results in less
pilot fuel requirement (Sahoo, Sahoo, and Saha 2009). The maximum reduction in diesel consump-
tion by dual fueling is observed at 3 kW load that is 44.44% for SG (cotton stalks) and 41.94% SG
(wheat straws).
0.0 0.6 1.2 1.8 2.4 3.0
1
2
3
4
5
)Wk(rewopdetacidnI
Load (kW)
Diesel only
Diesel+SG(Cotton Stalks)
Diesel+SG(Wheat Straws)
CR 18:1
Figure 3. Variations of indicated power at different loads in diesel and dual fuel mode.

Brake-specific fuel consumption
The variation of brake-specific fuel consumption (BSFC) with respect to distinct loads is depicted in
Figure 6. The BSFC depends upon the fuel consumption and CV of the fuel (Lal and Mohapatra
2017). It can be observed from the figure that in dual fuel mode, BSFC is higher than in diesel mode.
0.0 0.6 1.2 1.8 2.4 3.0
0
10
20
30
40
)%(ycneiciffelamrehtekarB
Load (kW)
Diesel only
CR 18:1
Figure 4. Variations of brake thermal efficiency at different loads in diesel and dual fuel mode.
0.0 0.6 1.2 1.8 2.4 3.0
6
7
8
9
10
11
12
13
14
15
16
)nim/lm(noitpmusnocleseiD
Load (kW)
Diesel only
CR 18:1
Figure 5. Diesel consumption at different loads in diesel and dual fuel mode.
8 J. SINGH ET AL.

This happens because of low calorific value of syngas as compared to diesel, so to produce specific
amount of power, larger volume of syngas is used as compared to diesel in single fuel mode. At lower
loads, a large amount of syngas is used which describes the higher BSFC but as load increases,
decreasing trend is observed for the dual fuel operation. At maximum load, for standard diesel
operation BSFC observed is 0.24 kg/kWh, whereas BSFC for dual fuel operation is 1.97 and 2.35 kg/
kWh for SG (cotton stalks) and SG (wheat straws), respectively. The higher value of BSFC in case of
SG (wheat straws) is due to lower CV of wheat straws than the cotton stalks which results in lower
specific energy of SG (wheat straws) than SG (cotton stalks).
Emission characteristics
The emission parameters are analyzed by using Portable Gas Analyser model ACE-8000 which is
based on the principle of infrared (IR) absorption that different gases absorb different wavelengths of
IR radiations incident on the mixture of gases.
HC emission
The emission of HCs in dual fuel mode and diesel mode is depicted in Figure 7 at different loads.
It is found that HC emission in dual fuel mode for both cotton stalk- and wheat straw-derived
syngas is higher than that of diesel mode. The emission of HCs in dual fuel mode got increased by
approximately 300% at maximum loading condition than that of standard diesel operation. It can
be observed from the figure that emission of HC reduces with increase in load. This is due to
incomplete combustion at lower loads but when load increases, more rich fuel mixture is supplied
to the combustion chamber and results in better combustion and reduction in the emission of HCs
(Nayak, Mishra, and Behera 2017). Dual fueling of SG (cotton stalks) yields better results at
maximum load as compared to SG (wheat straws). This is because of the presence of less carbon
content in cotton stalks as compared to wheat straws.
0.0 0.6 1.2 1.8 2.4 3.0
0
2
4
6
8
10
12
)hWk/gk(noitpmusnocleufcificepsekarB
Load (kW)
Diesel only
CR 18:1
Figure 6. Variation of BSFC at different loads in diesel and dual fuel mode.

CO emission
The variation of CO is illustrated in Figure 8 for standard diesel operation and dual fuel operation at
various load conditions. In dual fuel mode, the emission of CO is much higher than that of diesel
mode at all operating conditions. The CO emission at maximum loading condition is approximately
280% higher in case of syngas-diesel operation than that of standard diesel operation. It is due to
incomplete combustion of the fuel inside the cylinder because of induction of syngas with air which
reduces the amount of oxygen in the combustion chamber and unburnt gaseous originates from the
incomplete combustion which includes carbon monoxide as a major constituent (Nayak, Mishra,
and Behera 2017). It can be observed from the figure that on increasing the load the emission of CO
reduces sharply in dual fuel mode, whereas in diesel mode the reduction in emission is not that
dramatic. This reduction can be explained by the fact that on increasing load, the pilot fuel supply
increases which results in better combustion of gaseous fuel inside the chamber.
NOX emission
The variation of NOX emission is depicted in Figure 9 for standard diesel fuel mode and the dual fuel
mode for both the test fuels. The variations reflect that at all operating conditions, NOX emission is
found higher in the standard diesel run as compared to dual fuel run with either cotton stalk- or
wheat straw-derived syngas. It is observed that with increase in load the NOX emission increases for
all fuels. This is due to the reason that nitrogen is inert at low temperatures but at higher
temperatures, it reacts with oxygen to form NOX and as the load is increased, the temperature
inside the chamber increases and so does the NOX emission (Shrivastava et al., 2013). In dual fuel
mode, dramatic reduction in NOX emission is seen as compared to standard fuel mode. The
maximum reduction of 76.74% as compared to diesel mode at maximum load is observed for the
SG (wheat straws) whereas SG (cotton stalks) reduces the NOX by 74.71% at maximum load.
0.0 0.6 1.2 1.8 2.4 3.0
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
)mpp(CH
Load (kW)
Diesel only
CR 18:1
Figure 7. Effect of load on HC emission in diesel and dual fuel mode.
10 J. SINGH ET AL.

Exhaust gas temperature
The trend of exhaust gas temperature (EGT) with respect to load variations is shown in Figure 10 for
dual fuel mode and diesel mode. It is observed that EGT for dual fuel mode is higher at all loading
conditions than that of diesel mode. The maximum rise in EGT in dual fuel mode is observed to be
0.0 0.6 1.2 1.8 2.4 3.0
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
)mpp(OC
Load (kW)
Diesel only
CR 18:1
Figure 8. Effect of load on CO emission in diesel and dual fuel mode.
0.0 0.6 1.2 1.8 2.4 3.0
0
10
20
30
40
50
60
70
80
90
100
110
)mpp(xON
Load (kW)
Diesel only
CR 18:1
Figure 9. Effect of load on NOX emission in diesel and dual fuel mode.

17.5% higher than the standard diesel mode at maximum loading condition. This is due to the fact
that in dual fuel mode excessive energy is supplied to the engine as syngas carries some heat with
itself after gasification (Hassan et al. 2011). The dual fuel run in case of SG (cotton stalks) yielded
more EGT than SG (wheat straws); this may be due to higher CV of cotton stalks as compared to
wheat straws which increases the specific energy of SG (cotton stalks) than SG (wheat straws).
Noise characteristics
The noise characteristics of the dual fuel engine with respect to various load conditions are depicted
in Figure 11 for standard diesel and dual fuel modes. The results observed clearly indicate that
induction of syngas with the pilot fuel increased the sound level of the engine. The range of sound
level for standard diesel operation observed is 82.7–87.1 dB, whereas the range for the dual fuel
operation observed is 82.9–90.1 dB. The noise level increased in case of wheat straw-derived syngas
is higher than that of cotton stalk-derived syngas. At maximum load, increase in sound level in case
of dual mode of SG (wheat straws) and SG (cotton stalks) with respect to diesel mode is 2.8 and
1.9 dB. The noise of the engine depends upon various physical and chemical characteristics of the
fuel being used which are viscosity and density. With increase in density and viscosity, the noise of
engine reduces but in dual fuel mode the density and viscosity of the fuel in the combustion chamber
decrease hence results in more noise (Singh and Mohapatra 2018).
Combustion characteristics
Cylinder pressure
Combustion behavior can be depicted by cylinder pressure data, as combustion behavior directly
affects the performance and emission characteristics. The variation of cylinder pressure with
respect to crank angle is illustrated in Figure 12. In standard diesel operation, average maximum
pressure is 51.6 bar, whereas in case of dual fuel mode, the maximum cylinder pressure slightly
0.0 0.6 1.2 1.8 2.4 3.0
100
150
200
250
300
)Cº(erutarepmetsagtsuahxE
Load (kW)
Diesel only
CR 18:1
Figure 10. Effect of load on exhaust gas temperature in diesel and dual fuel mode.
12 J. SINGH ET AL.

dropped to 48.4 bar in case of cotton stalks-derived syngas and diesel operation and to 44.5 bar in
case of wheat straws-derived syngas and diesel operation. The drop of cylinder pressure in dual
fuel mode is due to the ignition delay due to combustion of syngas inside the cylinder. Inferior
0.0 0.6 1.2 1.8 2.4 3.0
81
82
83
84
85
86
87
88
89
90
91
)elbiced(esioN
Load (kW)
Diesel only
CR 18:1
Figure 11. Effect of load on noise level in diesel and dual fuel mode.
180 240 300 360 420 480 540 600
0
10
20
30
40
50
60
)rab(erusserprednilyC
Crank angle (° degree)
Diesel only
CR 18:1
Figure 12. Variation of cylinder pressure with respect to crank angle in diesel and dual fuel mode.

combustion of the syngas is due to less air present in the cylinder as for the complete combustion,
which causes slight shifting of cylinder pressure v/s crank angle curve towards the expansion
stroke which results lower the cylinder pressure (Sahoo 2010).
Effect of fuel properties
Syngas used in the dual fuel operation was derived from raw cotton stalks and wheat straws separately. The
results indicate that dual fuel operation in case of cotton stalks-derived syngas yielded better performance
characteristics than the syngas derived from wheat straws. This may be due to the fact that raw cotton stalks
have more CV thanthatof rawwheatstrawswhichcanbe seenin Table 1. Higher CVleads tohigher specific
energy available for the engine to utilize. Apart from performance characteristics, syngas derived from
cotton stalks has shown better results in emission as well. The emission of HCs and CO was lower at every
loading condition for cotton stalks-derived syngas than that of wheat straws-derived syngas. This may be
due to the less carbon content present in the raw cotton stalks.
Conclusion
Syngas produced by gasification of biomass obtained from agricultural waste has high potential to be
used as renewable fuel. Syngas which is combustible in nature can be used as fuel for boilers and
even it can be used as primary fuel in dual fuel engines to generate power. From the experimental
observations, it can be inferred that the diesel engines are capable of working in dual fuel mode by
using syngas as primary fuel and diesel as the pilot fuel. The various outcomes from the investigation
of the DFCI engine are discussed below:
(1) Dual fueling the CI engine slightly reduced the IP as compared to standard diesel operation. At
maximum load, the reduction in IP w.r.t. diesel mode observed is 3.49% and 6.60% for dual fuel
mode with SG (cotton stalks) and SG (wheat straws), respectively, due to lower CV of syngas.
(2) Along with reduction in IP, reduction in BTE can also be inferred. BTE in case of diesel
mode is observed to be 35.89% which got reduced in dual fuel mode to 26.19% and 24.39%
in case of dual fuel run with SG (cotton stalks) and SG (wheat straws), respectively, due to
inferior combustion in dual fuel mode in contrast to diesel mode.
(3) Slight reduction in IP in dual fuel mode accompanied with significant reduction in diesel
consumption by using syngas as primary fuel. At maximum load, maximum reduction in
diesel consumption is observed to be 44.44% and 41.94% for dual fuel run with SG (cotton
stalks) and SG (wheat straws), respectively.
(4) BSFC got increased in dual fuel mode as compared to diesel mode due to lower CV of syngas which
results in more consumption of fuel mixture to generate specific amount of power.
(5) With reduction in diesel consumption, significant reduction in NOX is also observed. The
maximum reduction in dual mode w.r.t. diesel mode is observed to be 76.74% in case of
wheat straws-derived syngas and 74.71% in case of cotton stalks-derived syngas.
(6) Emission of HCs and CO got increased drastically on inducting syngas in the dual fuel engine. This
may be due to presence of large amount of contents like hydrogen and CO in syngas and
incomplete combustion due to lack of oxygen in the combustion chamber.
(7) EGT in dual fuel modes is observed to be higher than diesel operation at all loading
conditions. This is due to the fact that in dual fuel mode additional energy is supplied to
the engine with syngas.
(8) Dual fueling the engine resulted in slight increase in noise level and vibrations. The noise
level got increased by 2.8 dB at maximum load in case of SG (wheat straws) and by 1.9 dB at
maximum load in case of SG (cotton stalks) due to less density and viscosity of fuel mixture
in dual fuel mode.
14 J. SINGH ET AL.

ORCID
Jatinderpal Singh http://orcid.org/0000-0001-9981-3965
Saroj Kumar Mohapatra http://orcid.org/0000-0003-0672-1514
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