Validation and calibration of diesel engine model using DME

121
Validation and calibration of diesel engine model using DME
(Assoc. Prof. Luong Cong Nho, Dr. Nguyen Lan Huong)1, (Assoc. Prof. Pham Huu Tuyen)2
1. Vietnam Maritime University, Email: nlhuongkdt@gmail.com, 484 Lach Tray street, Ngo Quyen
district, Hai Phong, Vietnam
2. Hanoi University of Science and Technology
Abstract Diesel engines are utilized in most of heavy duty vehicles due to their high efficiency and
performance. However, fossil fuel is being depleted currently, and emissions from diesel engine contains
many toxic substances such as CO, HC, NOx, PMwhich effect adversely on environment and human
health. Therefore, research and application of renewable alternative fuels are under consideration in
many countries and Vietnam as well. Recently, Dimethyl ether (DME) has been considered as a potential
alternative fuel for diesel engine. DME can be produced from a variety of raw materials such as biomass,
coal and natural gas. It is also easy to liquefy and suitable to use in diesel engines. DME is not a nature
product but a synthetic product is produced either through the dehydration of methanol or a direct
synthesis from syngas. Using DME for diesel engine may reduce not only dependence on fossil fuel but
also environmental pollution. Certain amounts of DME have been commercially produced as a
propellant for spray cans because of its non-toxicity and suitable solubility and vapor pressure at room
temperature. Some experimental investigations were conducted on diesel engine to clarify how DME
injection characteristics affect the engine performance and exhaust emissions. Most of the results
showed that emissions when fueled DME reduced significantly, especially CO and soot.
This paper presents a validation and calibration of diesel engine model fueled by DME. The engine was
modeled by AVL Boost software and validated by experience. The parameters related to combustion
process, for example ignition delay, combustion parameters, were calibrated and the effects of these
parameterson performance of diesel engine fueled by DME were studied. Results show that in case of
the same engine power the ignition delay calibration factor with DME can be chosen value of 1.37 while
it is 1 with diesel.
Keywords: Dimethyl ether, engine simulation, combustion parameter, ignition delay calibration factor.
1. Introduction
Nowadays, research and utilization of renewable fuels in order to ensure energy security and reduce
pollution emissions are of interest in many countries. Among these fuels, Dimethyl Ether (DME) is a
friendly - environment fuel, easy to liquefy and suitable for use in diesel engines.
DME, chemical formula is CH3-O-CH3, is a colorless organic compound. DME is in gaseous form at
ambient pressure and temperature. To increase the energy density, DME is usually stored in liquid form
under compressed pressure of 7 to 10bar. DME can be produced from a variety of raw materials such as
biomass, coal and natural gas and it is considered as a clean alternative fuel in near future. Using DME
for diesel engine may reduce not only dependence on fossil fuel but also environmental pollution. DME
is not a nature product but a synthetic product is produced either through the dehydration of methanol
or a direct synthesis from syngas. Most of the results showed that emissions when fueled DME reduced
significantly, especially CO and soot.
This paper presents a validation and calibration of diesel engine model fueled by DME. Diesel engine
Kubota RT140 is modeled by using AVL Boost software and validated by experience.
2. Modeling theory
2.1 Combustion model
122 
1 2. ( , ). ( , )
MCC
Comb F MCC
dQ
C f m Q f k V
d 
2 3
( , ) .Rate
k
f k V C
V
 ,
.
1
Diff
turb kin
F I stoich
C E
k
m m
The combustion in diesel engine can be considered by two processes: premixed combustion and mixing 
controled combustion processes 
total MCC PMCdQ dQ dQ
d d d 
Qtotal: total heat release over the combustion process [kJ]. 
QPMC : total fuel heat input for the premixed combustion [kJ] 
QMCC: cumulative heat release for the mixture controlled combustion [kJ] 
Premixed combustion model: 
A Vibe function is used to describe the actual heat release due to the premixed combustion: 
( 1).. 1 . .
m
PMC
PMC m a y
c
dQ
Q a
m y e
d 
, id
c
y
QPMC : total fuel heat input for the premixed combustion = mfuel,id . CPMC 
mfuel,id : total amount of fuel injected during the ignition delay phase 
CPMC: premixed combustion parameter 
∆αc : premixed combustion duration=  id.CPMC-Dur 
CPMC-Dur : premixed combustion duration factor 
m : shape parameter m=2.0 
a : Vibe parameter a= 6.9 
- Mixing Controlled Combustion process: 
In this regime the heat release is a function of the fuel quantity available (f1) and the 
turbulent kinetic energy density (f2): 
 with 
 𝑓1(𝑚𝐹 , 𝑄) = (𝑚𝐹 −
𝑄𝑀𝐶𝐶
𝐿𝐶𝑉
) . (𝑤𝑂𝑥𝑦𝑔𝑒𝑛,𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑙𝑒)
𝐶𝐸𝐺𝑅
CComb : combustion constant [kJ/kg/deg CA] 
CRate: mixing rate constant [s] 
k : local density of turbulent kinetic energy [m2/s2] 
mF:vaporized fuel mass (actual) [kg] 
LVC: lower heating value[kJ/kg] 
V: cylinder volume [m3] 
α : crank angle [deg CA] 
wOxygen,available: mass fraction of available Oxygen (aspirated and in EGR) at SOI [-] 
CEGR EGR influent constant [-] 
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Ekin : kinetic jet energy [J]
Cturb : turbulent energy production constant [-]
F,I : injection fuel mass (actual) [kg]
Diff : Air Excess Ratio for diffusion burning [-]
mstoich :stoichiometric mass of fresh charge [kg/kg]
2.2 Heat transfer model
The heat transfer to the walls of the combustion chamber, i.e. the cylinder head, the piston, and the
cylinder liner, is calculated from equation [3]
( )Q A T Tcwi i i wi   
Where Qwi - wall heat flow, Ai - surface area, αi - heat transfer coefficient, Tc - gas temperature in the
cylinder, Twi - wall temperature.
Heat transfer coefficient (αi) is usually calculated by WOSCHNI Model, The Woschni model published
in 1978 for the high pressure cycle is summarized as follows [6]:
0,2 0,8 0,53130. . . .
. 0,81
 .[ . . .( )]1 2 ,0
.,1 ,1
D p T
w c c
v TD cC c C p p
m c cp Vc c
Where C1 = 2.28 + 0.308.cu/cm, C2 = 0,00324 for DI engines, D - cylinder bore, cm - mean piston speed,
cu - circumferential velocity, cu = π.D.nd/60, VD - displacement per cylinder, pc,o - cylinder pressure of
the motored engine (bar), Tc,1 - temperature in the cylinder at intake valve closing (IVC) , pc,1 - pressure
in the cylinder at IVC (bar).
2.3 Modeling diesel engine Kubota RT140
Kubota RT140 Engine is a single horizontal cylinder, four-stroke, naturally aspirated, water cooled, DI.
The engine specification is shown in Table 3, and the model is built by AVL Boost software
(Figure 1)
Table 3 Specifications of the engine
Table. 3 Specifications of the engine
Rating output
Maximum torque
Bore / Stroke
Swept volume
Compression ratio
Injection pressure
Nozzle number x orifice
diameter/ mm
Static injection timing
11kW at 2400 rpm
42 Nm at 1500 rpm
97/96 mm
709 cm3
18:1
240 bar
4 x 0.30
25 CA BTDC
m

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Figure 1 Diesel engine Kubota RT140 model
3. Simulation results and discussion
3.1 Validation and calibration of diesel engine model fueled by DME
Boost uses the Mixing Controlled Combustion (MCC) model for the prediction of the combustion
characteristics in direct injection compression ignition engines. There are several factors relating to
ignition delay period as: the ignition delay calibration factor, etc. The ignition delay calibration factor
is a factor to assess the impact of the ignition delay.
Figure 2 Rate of heat release of diesel engine
The ignition delay calibration factor with DME be adjusted lower than that with diesel, because DME
is a clean fuel with good self- ignition charateristics. The ignition delay calibration factor with DME
can be chosen value of 1.37 while it is 1 with diesel. The ignition delay calibration factor with DME is
lower average 27% than that with diesel. (Fig 3).
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Figure 3 Ignition delay with diesel and DME
Addition, when the ignition delay calibration factor reduces, the pressure in the cylinder increases. When
the ignition delay calibration factor reduces, that mean the ignition delay period is longer and premixed
combustion phase is shorter, so the pressure in the cylinder increases.
Figure 4 Pressure in the cylinder with diesel and DME
The combustion parameter coefficient is an important factor because it has the most impact on the rate
of heat release graph. The value of this coefficient is more higher, and the combustion in the cylinder is
more quickly. Cetane number of DME is high, so the combustion parameter coefficient with DME is
lower than that with diesel and lower average 68.8%. (Fig 4)
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Figure 5 Combustion parameter with diesel and DME
The premix combustion parameter influences premixed combustion phase. The coefficient is determined
by the amount of fuel in the ignition delay period and premixed combustion phase. The premix
combustion parameter with DME is 1 while it is 0.7 with diesel.
Figure 6 Premix combustion parameter with diesel and DME
3.2 Model validation
The model has been validated by experiment in case of using conventional diesel and DME. It showed
that the torque as well as fuel consumption between simulation and experiment in case of diesel matched
quite well: on average the difference in torque and fuel consumption was about 1.7 % and 1.9 %,
respectively. Thus, it is possible to use this model to simulate the engine with DME fuel (Fig 5, Fig 6).
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Figure 7 Torque with diesel
Figure 8 Fuel consumption with diesel
In case of DME, the torque as well as fuel consumption between simulation and experiment are similar,
on average the difference in torque and fuel consumption was about 1.7 % and 3.1 % (Fig 7, Fig 8).
Figure 9 Torque with DME
128
Figure 10 Fuel consumption with DME
4. Conclusions
The engine was modeled by AVL Boost software and validated by experience.
The ignition delay calibration factor with DME can be chosen value of 1.37 while it is 1 with diesel.
The combustion parameter coefficient with DME is lower average 68.8% than that with diesel.
The premix combustion parameter with DME is 1 and it is 0.7 with diesel.
Performance of DME fueled Kubota diesel engine are simulated by AVL Boost software. The model is
verified by experiment: the torque as well as fuel consumption between simulation and experiment in
case of diesel and DME matched quite well.
References:
[1] Yoshio Sato, Akira Noda and LiJun, “Effects of Fuel Injection Characteristics on Heat Release
and Emissions in a DI Diesel Engine Operated on DME” SAE 2001-01-3634,2001.
[2] Kanit Wattanavichien. “Implementation of DME in a Small Direct Injection Diesel Engine”. 1st
AUN- SeeedNet Regional Workshop on New and Renewable Energy, 12-13 March 2009, at ITB,
Bandung, Indonesia
[3] Nguyen Lan Huong, Luong Cong Nho, Pham Huu Tuyen. “Dimethyl Ether (DME)- An alternative
fuel for diesel engine”. Journal of Transportation December- 2012.
[4] Nguyen Lan Huong, Luong Cong Nho, Pham Huu Tuyen. “ Investigating Dimethyl ether (DME)
fuel systems for Diesel engine”. Journal of Transportation March- 2013.
[5] Nguyen Lan Huong, Luong Cong Nho, Pham Huu Tuyen. “Simulation study on diesel engine
fueled by Dimethyl Ether (DME)”. scientific conference mechanical pneumatic 2013.
[6] G. D’Errico, et al. (2002). “Modeling the Pollutant Emissions from a S.I. Engine”, SAE paper No.
2002-01-0006.
[7] Users guide- AVL Boost version 2011.1. Theory- AVL Boost version 2011.1
[8] G. Woschni (1967). “A Universally Applicable Equation for the Instantaneous Heat Transfer
Coefficient in Internal Combustion Engines”. SAE paper No. 6700931.