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CHEMICAL ENGINEERING TRANSACTIONS
VOL. 65, 2018
A publication of
The Italian Association
of Chemical Engineering
Online at www.aidic.it/cet
Guest Editors: Eliseo Ranzi, Mario Costa
Copyright © 2018, AIDIC Servizi S.r.l.
ISBN 978-88-95608- 62-4; ISSN 2283-9216
Characterization of Auto-Ignition Phenomena in Spark Ignition
Internal Combustion Engine using Gaseous Fuels Obtained
from Biomass
Jorge Duarte Forero*a, Guillermo Valencia Ochoab, Yulineth Cárdenas Escorciac
a Universidad del Atlántico, Robotic and Mechanical Systems Desing for Industrial Production Research Group, DIMER,
College of Engineering, Barranquilla, Colombia
b Universidad del Atlántico, Efficient Energy Management Research Group, KAÍ, College of Engineering, Barranquilla,
Colombia
c Universidad de la Costa, Research Group in Energy Optimization, GIOPEN, Department of Energy, Barranquilla,
Colombia.
jorgeduarte@mail.uniatlantico.edu.co
Studies have been carried out on the phenomenon of auto-ignition in liquid fuels and natural gas, but research
on the application of gaseous fuels obtained from biomass is limited. Existing investigations about auto-
ignition mainly focused on the combustion kinetics to determine the delay time, but not on the prediction of the
set of parameters that encourage the presence of the phenomenon. In the present research, a thermodynamic
model is developed for the prediction of the auto-ignition in Spark Ignition Internal Combustion Engine
operated with gaseous fuels, which are obtained from the process of gasification of biomass. The formulated
model can handle variable compositions of gaseous fuels and to optimize the main operational parameters of
the engine, to verify its influence on the phenomenon under study. Results show the application of this type of
alternative fuels in commercial engines that operated with natural gas, varying engine operational parameters
while maximizing the power output of the engine.
1. Introduction
In the global context, due to the shortage of natural gas and its high cost, some countries have been forced to
look for new forms of gaseous fuels. These new fuels must be not only economically attractive but also
friendly to the environment and easy to implement in internal combustion engines, where the fuel they are
currently using is natural gas (Amran, Ahmad, & Othman, 2017). Similarly, in recent years, important research
has been carried out on the impact of the use of alternative gaseous fuels in the performance of internal
combustion engines. The use of gaseous fuels in combustion internal combustion engines has been
developed a lot, but there is a limitation of the increase in efficiency as a function of the increase in the
compression ratio (CR). The above is because the CR increases the autoignition phenomenon, which occurs
when combustion starts before ignition of the spark, which leads to the high-pressure peaks and a shock wave
is generated inside the combustion chamber (Gersen, Darmeveil, & Levinsky, 2012).
The current studies on the phenomenon of autoignition in internal combustion engines operated with gaseous
fuels produced by gasification (producer gas or syngas) are limited and are focused on the engines of natural
aspiration and low power (< 25 kW) (Bika, Franklin, & Kittelson, 2012; P Boivin, Sánchez, & Williams, 2017;
Mittal, Sung, & Yetter, 2006). Several of these studies (Pierre Boivin, Jiménez, Sánchez, & Williams, 2011;
Yu, Vanhove, Griffiths, De Ferrières, & Pauwels, 2013) concluded that the phenomenon of autoignition is not
accentuated in naturally aspirated engines, and that it is very much harmful to supercharged engines of high
CR (Duarte et al., 2014).
Azimov et al. (2011) concerned with engine experiments and spectroscopic analysis of premixed mixture
ignition in the end-gas region combustion in a pilot fuel ignited the natural gas dual-fuel engine. The results
reveal the characteristics and operating parameters that induce and affect this combustion mode. In
combustion, the heat release gradually transforms from the slower first-stage flame rate to the faster second-
193
DOI: 10.3303/CET1865033
Please cite this article as: Duarte J., Valencia Ochoa G., Cardenas Y., 2018, Characterization of auto-ignition phenomena in spark ignition
internal combustion engine using gaseous fuels obtained from biomass, Chemical Engineering Transactions, 65, 193-198
DOI: 10.3303/CET1865033
stage rate. For the characterized H2 / CO combustion and reaction chemistry under high-pressure and
moderate-temperature operating conditions, Ihme (2012) analyzes several chemical-kinetics, and
hydrodynamic processes have been identified as being responsible for the discrepancies between
experimental measurements and kinetic predictions of syngas ignition delay times. The above allows
characterizing the auto-ignition in motors operated with syngas.
Pal et al. (2015) analyses the reaction front speed and front Damköhler number, were employed to
characterize the propagating ignition front. The ignition behaviour shifted from spontaneous propagation
(strong) to deflagrative (weak), as the initial mean temperature of the reactant mixture was lowered. The
conclusion is that sufficiently low temperatures, the strong ignition regime was recovered due to the faster
passive scalar dissipation of the imposed thermal fluctuations relative to the reaction timescale, which was
quantified by the mixing Damköhler number. On the other hand, Przybyla et al. (2016) summarize results of
experimental trials with the SI and HCCI engine fueling with a producer gas substitute. Engines were fueled
with the producer gas substitute that simulated real producer gas composition. The SI engine was charged
with a stoichiometric air/fuel mixture, while the HCCI engine with a lean air/fuel mixture with an equivalent ratio
of 0.5 and the main variable control in the SI engine operation was the spark timing.
Amador et al. (2017) explored the feasibility of using Syngas with low methane number as fuel for commercial
turbocharged internal combustion engines. The effect of methane number (MN), compression ratio (CR), and
intake pressure on auto-ignition tendency in spark ignition internal combustion engines was determined. An
error function, which combines the Livengood–Wu with ignition delay time correlation, to estimate the knock
occurrence crank angle (KOCA) was proposed. The results showed that the KOCA decreases significantly as
the MN increases. Results also showed that Syngas obtained from coal gasification is not a suitable fuel for
engines because auto-ignition takes place near the beginning of the combustion phase, but it could be used in
internal combustion engines with reactivity controlled compression ignition (RCCI) technology.
In the present research, a thermodynamic equilibrium model is proposed, which allows predicting the point
where auto-ignition will occur in the compression stroke as a function of the geometric and operational
parameters of the engine. This model has been validated in turbocharged engines, which allows verifying the
viability of the use of syngas in commercial engines used for the generation of electric power.
2. Methodology
In the present research, the following methodological steps were developed, to achieve significant results on
the study of auto-ignition applied to spark ignition engines operated with gaseous fuels. It began with a review
of state of the art, focusing on the latest studies on auto-ignition in thermal engines and characterization of
biomass product of gasification. Then, a thermodynamic model was implemented to predict the temperature in
the combustion chamber before the ignition point, which applies to turbocharged engines. Validation was
carried out using natural gas as fuel, to extrapolate the model to other types of gaseous fuels. Based on the
state of the art review, the typical auto-ignition temperature of different gaseous fuels obtained by gasification
was identified. The application of the developed model leads to a predicted temperature inside the combustion
chamber at the ignition point, which is compared with the auto-ignition temperature of each fuel analyzed. As
the ignition point is a function of the spark advance, with the proposed methodology, the ignition angle can be
optimized so that ignition does not occur. The iterative process, in turn, allows maximizing the output power,
since according to de Faria (de Faria, Bueno, Ayad, & Belchior, 2017), the ignition point has a direct
relationship with the power developed by the engine. Finally, in the study the influence of the compression
ratio (CR) and intake pressure on auto-ignition is verified, to find the set of operational parameters at which a
certain syngas can operate in a commercial engine.
3. Proposed Model
Because the engine under study is of stationary application (generation of electrical energy), speed engine
does not vary in its nominal operating condition. The above implies that it is possible to assume a quasi-
stationary state and describe it as a polytropic process. The relationship between pressure (P), volume (V)
and polytropic coefficient (n) is described by:
= = ( ) (1)
It will be assumed that the amount of heat released by the burned gases stored in the volume defined by the
top dead center in the combustion chamber, which will be at the temperature of the exhaust gases, is received
by the air/fuel mixture, which occurs at high engine speed (Duarte et al., 2014). For the calculation of
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thermodynamic properties, correlations of gas mixtures as a function of temperature are proposed, so that the
property can be adjusted for each temperature increase (with a step of 1 ° C). Figure 1 shows the scheme of
the system to be analyzed and its intermediate points:
Figure 1: Stages of analysis in the engine under study
As the system to be analyzed is in series from the mixer, the effect of each of the elements involved in the
system must be coupled. Starting at 0 and ending at 4. 0 - 1 is the process in the Turbocharger, 1 – 2
aftercooler, 2 – 3 Heat Transfer Air/Fuel mixture and Exhaust gases and 3 – 4 Compression stroke. The
equation (2) is obtained for the estimation of the temperature at the ignition point through an analysis of
equilibrium thermodynamics applying equation (1) and the volume adjustment model of the combustion
chamber in internal combustion engines developed by Duarte (2016).
=
∙ ∙∙ ∙ ( − 1) + ∙ − ∆1 + ∙∙ ∙ ( − 1)∙ 1 + − 12 ∙ + 1 − − ( − ) + ∙4 ∙ ∙ ( ∙ + ∙ )∙ (2)
The terms of Eq. 4 are specified in Table 1.
Table 1: Definition of terms Ec. (2)
Terms Description
T4 Temperature at the ignition point [K]
CpEG Heat capacity of exhaust gases[kJ/kg K]
CpM Heat capacity of the air/fuel mixture, which is a function of the composition of the gaseous fuel
[kJ/kg K]
ρEG Density of exhaust gases [kg/m
3]
ρM Density of the air/fuel mixture, which is a function of the composition of the gaseous fuel
[kg/m3]
TEG Exhaust gas temperature [K]
TE Environmental temperature [K]
Pi Pressure at point i [Pa]
CR Compression ratio
ni Polytropic coefficient at point i
∆TIC Temperature drop in the intercooler [K]
Vc Clearance Volume [m
3]
R Relation between connecting rod length and crank radius
θ Crankshaft angle [°]
KDEF Coefficient of deformation, adjusted for each engine and taking into account that not all parts
of the mechanism are made of steel
LCR Length of the connecting rod [m]
AP Piston area [m
2]
mi mass Connecting rod, piston and pin [kg]
a Acceleration of connecting rod, piston, and pin [m/s2]
ESTEEL Young's module of steel [Pa]
ACR Cross section area of the connecting rod [m
2]
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Eq. (4) take into account the mechanical deformations due to pressure and inertia in the connecting rod-piston
mechanism. These deformations are manifested through variations in the instantaneous volume, especially in
the vicinity of TDC, which affects the prediction of the actual temperature inside the combustion chamber. P4
is a function of T4, so Eq. 4 is an implicit expression, so an algorithm was designed to find the solution.
4. Results Analysis
For the validation of the proposed model, the intake temperature and the compression ratio were varied. The
characteristics of the engine used for the simulation are the following:
Table 2: Characteristics of the engine used in the study
Characteristic Description
Manufacturer Yamaha
Model EF2400
Displacement [cc] 2400 cc
Test Power [kW] 2.4
Engine speed [rpm] 3600
Compression ratio range 8 - 10
Turbocharger discharge pressure range [bar] 1 – 1.2
Intake Temperature (held fixed for the study) [°C] 35
A/F Ratio (held fixed for the study) 15
Ignition angle (held fixed for the study) [°BTDC] 18
KDEF (adjusted with motored test) 1.2
The adjusted value of the polytropic coefficients of the engine used in the study n01 and n34 were 1.382 and
1.365, respectively. Initially, the performance of the model was verified using natural gas as fuel, then the
behavior of the model with wood gas is validated. According to Malenshek et al. (2009) and Amador et al.
(2017), the characteristics of the fuels and their respective methane numbers (MN) to be modeled are the
following.
Table 3: Characteristics of gaseous fuel used in the study
Components [%] Natural gas (MN = 61.3) Wood gas (MN = 61.3)
CH4 97.3 8.3
H2 0.0 39.8
N2 0.3 2.7
CO 0.0 24.2
CO2 0.0 24.1
C2H6 2.6 0.0
C3H8 0.2 0.0
C4H10 0.1 0.0
The autoignition temperature is a characteristic of the fuel described in Table 2. Figure 2 shows the behavior
of the model using natural gas as a fuel and the comparison with the autoignition temperature defined by
Amador et al. (2014).
Figure 3 shows the behavior of the model using Wood gas as a fuel and the comparison with the auto-ignition
temperature defined by Malenshek et al. (2014).
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Figure 2: Comparative modeled temperature at the ignition point and Auto-ignition temperature of Natural Gas
Figure 3: Comparative modeled temperature at the ignition point and Auto-ignition temperature of Wood Gas
For the results of the model illustrated in Figure 2 and 3, the same engine speed was used, taking into
account that the engine under study is used for the generation of electrical energy, where the engine speed
must remain constant to maintain utility frequency. In both figures it is observed that the temperature at the
ignition point increases proportionally with the increase of the intake pressure. Air/Fuel ratio and intake
temperature were kept constant in the study, so as not to influence the results of the prediction of the
temperature at the ignition point and adjust to the auto-ignition temperature values defined by Malenshek et al.
(2009) and Amador et al. (2017).
5. Conclusions
Figure 2 and 3 show the influence of the intake pressure and the compression ratio on the temperature at the
ignition point. As the intake pressure increases, the temperature at the ignition point increases. The same
behavior is observed with the compression ratio (CR), which is consistent with the results obtained in previous
works (Duarte et al., 2014, Amador et al., 2017). For the engine under study, for the range of CR of 8 to 12
and Intake Pressure of 1 to 1.4 bar, it can be seen in Figure 2 the absence of auto-ignition in the compression
stroke when operating with natural gas, since the auto-ignition temperature is not reached.
In the case of Wood Gas, Figure 3 shows that the engine under study can be operated up to an intake
pressure of 1.2 bar and a compression ratio of 12. In the case of Intake Pressure of 1.4 bar, auto-ignition is
presented, except for CR = 8. At the point of operation with CR = 10 and CR = 12 and Intake Pressure of 1.4,
it is evident that the temperature at the ignition point is above the auto-ignition. It is necessary, as a strategy
for mitigating this harmful phenomenon, delay the angle of ignition (increase) or change A/F Ratio so that the
auto-ignition temperature of the Wood Gas increases.
References
Amador, G., Forero, J. D., Rincon, A., Fontalvo, A., Bula, A., Padilla, R. V., & Orozco, W., 2017,
Characteristics of Auto-Ignition in Internal Combustion Engines Operated With Gaseous Fuels of Variable
Methane Number. Journal of Energy Resources Technology. https://doi.org/10.1115/1.4036044
197
Amran U.I., Ahmad A., Othman M.R., 2017, Kinetic based simulation of methane steam reforming and water
gas shift for hydrogen production using aspen plus, Chemical Engineering Transactions, 56, 1681-1686
DOI:10.3303/CET1756281
Azimov, U., Tomita, E., Kawahara, N., & Harada, Y., 2011, Effect of syngas composition on combustion and
exhaust emission characteristics in a pilot-ignited dual-fuel engine operated in PREMIER combustion
mode. International Journal of Hydrogen Energy, 36(18), 11985–11996.
Bika, A. S., Franklin, L., & Kittelson, D. B., 2012, Homogeneous charge compression ignition engine operating
on synthesis gas. International Journal of Hydrogen Energy, 37(11), 9402–9411.
Boivin, P., Jiménez, C., Sánchez, A. L., & Williams, F. A., 2011, A four-step reduced mechanism for syngas
combustion. Combustion and Flame, 158(6), 1059–1063.
Boivin, P., Sánchez, A. L., & Williams, F. A., 2017, Analytical prediction of syngas induction times. Combustion
and Flame, 176, 489–499.
de Faria, M. M. N., Bueno, J. P. V. M., Ayad, S. M. M. E., & Belchior, C. R. P., 2017, Thermodynamic
simulation model for predicting the performance of spark ignition engines using biogas as fuel. Energy
Conversion and Management, 149, 1096–1108.
Duarte, J., Amador, G., Garcia, J., Fontalvo, A., Padilla, R. V., Sanjuan, M., & Quiroga, A. G., 2014, Auto-
ignition control in turbocharged internal combustion engines operating with gaseous fuels. Energy, 71,
137–147.
Duarte, J., 2016, Aportación al estudio y modelado Termodinámico en Motores de Combustión Interna.
Doctoral Thesis. Universidad del Norte, Colombia.
Gersen, S., Darmeveil, H., & Levinsky, H., 2012, The effects of CO addition on the autoignition of H 2, CH 4
and CH 4/H 2 fuels at high pressure in an RCM. Combustion and Flame, 159(12), 3472–3475.
Ihme, M., 2012, On the role of turbulence and compositional fluctuations in rapid compression machines:
Autoignition of syngas mixtures. Combustion and Flame, 159(4), 1592–1604.
Malenshek, M., & Olsen, D. B., 2009, Methane number testing of alternative gaseous fuels. Fuel, 88(4), 650-
656.
Mittal, G., Sung, C.-J., & Yetter, R. A., 2006, Autoignition of H2/CO at elevated pressures in a rapid
compression machine. International Journal of Chemical Kinetics, 38(8), 516–529.
Pal, P., Mansfield, A. B., Arias, P. G., Wooldridge, M. S., & Im, H. G., 2015, A computational study of syngas
auto-ignition characteristics at high-pressure and low-temperature conditions with thermal
inhomogeneities. Combustion Theory and Modelling, 19(5), 587–601.
Przybyla, G., Szlek, A., Haggith, D., & Sobiesiak, A., 2016, Fuelling of spark ignition and homogenous charge
compression ignition engines with low calorific value producer gas. Energy, 116, 1464–1478.
Yu, Y., Vanhove, G., Griffiths, J. F., De Ferrières, S., & Pauwels, J.-F., 2013, Influence of EGR and syngas
components on the autoignition of natural gas in a rapid compression machine: A detailed experimental
study. Energy & Fuels, 27(7), 3988–3996.
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