Journal of Beijing Institute of Technology, 2013, Vol. 22, No. 2
Analysis of vehicle powertrain dynamic performance
LUO Guo鄄liang( 罗国良) 1,苣 ,摇 ZHANG Fu鄄jun( 张付军) 1 ,摇 YUAN Hao鄄jie( 袁豪杰) 2
(1. School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China;
2. Beijing Research Institute of Mechanical & Electrical Technology, Beijing 100074, China)
Abstract: To study the vehicle dynamic characteristics under typical cycle conditions, a steady鄄state
simulation model of the engine in GT鄄Power is established and verified with engine bench test data.
A dynamic model of the engine is then established. A co鄄simulation with the engine dynamic model
in GT鄄Power and the vehicle transmission model in AMESim is conducted based on the technology of
HLA / RTI. The parameter changes of vehicle powertrain in the accelerating process of 0 - 32 km / h,
and vehicle typical cycle conditions are studied. The influence laws of the typical parameters influen鄄
cing vehicle dynamic characteristics are obtained, and a new approach of improving vehicle dynamic
characteristics is proposed. The results show that the vehicle powertrain dynamic model can simu鄄
late, analyze and predict dynamic changes of vehicle in actual operating conditions and guide power鄄
train matching and optimization.
Key words: powertrain; dynamic characteristics; numerical simulation; experimental research
CLC number: TK 422摇 摇 Document code: A摇 摇 Article ID: 1004鄄 0579(2013)02鄄 0171鄄 08
摇 摇 Vehicle蒺s acceleration performance and fuel
zation of the design. The dynamic simulation
combat capability and viability for tracked vehi鄄
vehicle development cycle and reduce develop鄄
economy are important indicators to measure
cles. With actual operating and load conditions,
vehicle powertrain system works under dynamic
method is of great significance to accelerate the
ment cost.
operating conditions. Research shows that when
the vehicle is running on the road, the engine
1摇 Theoretical analysis of the dy鄄
namic model
load and speed and other parameters are also in a
摇 摇 In the vehicle development research and the
state of flux, and 66% to 80% of the total operat鄄
vehicle matching process, it is often necessary to
ing conditions are dynamic conditions
. For
analyze and calculate the performance of power鄄
ating conditions is even higher and the driving
and optimal design of the power transmission de鄄
on the plains, plateau, desert and hills, etc. ,
clude the engine, hydraulic torque converter and
[1]
tracked vehicles, the proportion of dynamic oper鄄
train components, so as to achieve a good match
mode is complex, because they normally travel
vice [2] . The powertrain components mainly in鄄
rarely on the highway. Therefore, the results of
gearbox. In this paper, the forward simulation
vehicle dynamics simulation are close to the
modeling approach was used to develop vehicle
dict vehicle performance more accurately and
model, engine model, the torque converter mod鄄
vehicle蒺s actual operating conditions, and can pre鄄
powertrain dynamic model, including the driver
guide the vehicle powertrain matching and optimi鄄
el, gearbox model, vehicle dynamics model and
Received摇 2011鄄 11鄄 22
Supported by National Ministry Fundamental Research Foun鄄
dation of China ( D2220062905)
苣 Author for correspondence
E鄄mail: luogl@ bit. edu. cn
typical vehicle driving cycle model.
In the
turbo diesel dynamic
simulation
process, some parameters of the engine are not
set in advance, which is different from the stead鄄
— 171 —
Journal of Beijing Institute of Technology, 2013, Vol. 22, No. 2
y鄄state process calculation [3] . These parameters
摇 摇 According to the main technical parameters
of engine performance; while the engine perfo鄄
culation model, which composed of air intake
are functions of time, and change with the variety
mance depend on the vehicle load, moment of in鄄
ertia and the running time. In this paper, turbo
diesel engine dynamic model was designed based
on the idea of transforming steady鄄state model in鄄
to dynamic model. We first established turbo
diesel steady鄄state simulation model in GT鄄Pow鄄
in Tab. 1, the diesel engine is simplified as a cal鄄
system, exhaust system, the combustion ratio
( cylinder) , fuel injection system, supercharging
system, intercooler, environmental boundaries
and the corresponding connecting pipe model,
etc.
Cylinder model is core of the model [5] . Mod鄄
er [4] , and verified the model using the steady鄄
els including geometric model, combustion mod鄄
the accuracy of the model meet the needs of the
will be defined here. Among them, the combus鄄
state engine bench test data in order to make sure
transformation into a dynamic model. Secondly,
by examining test data and the results of steady鄄
state model, we selected typical parameters,
which change significantly with the engine operat鄄
ing conditions, to form a function of engine speed
or load and establish the engine map that changes
with speed and load. These map data will provide
boundary conditions for the dynamic process cal鄄
culation, by using table look鄄up method based on
these engines work operating point position.
Therefore, the model is capable of changing with
the speed or load and making the appropriate re鄄
el, the wall temperature and heat transfer model
tion model is the most important because it deter鄄
mines series of processes including the cylinder
gas mixture, combustion and heat release and has
a decisive impact on the performance of the en鄄
gine [6] . In this paper, the entire combustion
process is divided into pre鄄mixed combustion
phase, the mixing鄄controlled combustion phase
and late burning phase, by using ternary Weber
model. The combustion heat release rate curve
can be given by the superposition of three Weber
function curves [7] , as shown below:
X = X1 + X2 + X3 ,
sponse; external load are applied to the engine
dynamic model and provide dynamic variable load
dX dX1 dX2 dX3
=
+
+
,
d准 d准 d准 d准
(1)
(2)
to balance the engine torque. Finally, we set
where X1 , X2 , X3 denotes the fuel fraction of pre鄄
calculation mode, to obtain simulation results of
combustion phase and late burning phase respec鄄
2摇 Modeling
at the same time, and has its own combustion du鄄
some parameters, such as the GT鄄Power software
the engine dynamic process.
mixed combustion phase, the mixing鄄controlled
tively. Each part of the combustion model starts
ration and combustion index.
A turbo diesel engine model was established
Experimental data are used as the inputs for
based on DEUTZ BF6M1015CP diesel engine, u鄄
turbocharger, intercooler and air filter modules.
the engine are shown in Tab. 1, where D denotes
coefficient, the simulation results agreed well
the compression ratio, n is the rated engine
parameters in the model were calibrated by the
Tab. 1摇 Main parameters of diesel engine
model can adequately reflected the characteristics
sing GT鄄Suite software. Specific parameters of
By adjusting the flow coefficient and heat transfer
the cylinder diameter, S denotes the stroke, 着 is
with the experimental data. Then, four typical
speed, and P represents the rated engine power.
results of engine steady鄄state test so that the
D / mm
S / mm
着
132
145
17郾 5
n / ( r·min - 1 )
2 100
P / kW
300
of the engine under steady state operating condi鄄
tions. These parameters were the engine power,
air flow, engine fuel consumption rate and boost
— 172 —
LUO Guo鄄liang( 罗国良) et al. / Analysis of vehicle powertrain dynamic performance
pressure, which were measured in 100% , 80% ,
then we revised the model. The inlet flow was
ating point.
of Toceil Company. The cylinder pressure was
60% and 40% throttle opening under typical oper鄄
The dynamic
characteristic
of
hydraulic
torque converter in unsteady conditions is defined
as the relationship curves for the pump wheel dy鄄
namic torque, turbine shaft dynamic torque, an鄄
gular velocity, speed ratio and time
tively, M
D
P
and M
D
T
[8]
. Respec鄄
are the dynamic torque of
pump and turbine under the unsteady operation
condition; M
HD
P
and M
HD
T
are the dynamic hydraulic
torque of pump and turbine under the unsteady
operation condition; J P and J T are the pump
measured with the 20N125 hot鄄film air flow meter
measured with the transient cylinder pressure sen鄄
sor of Kistler. The intake pressure and tempera鄄
ture of the cold air were measured with steady鄄
state pressure sensor and thermistor of PT100.
The exhaust pressure and temperature before tur鄄
bine were measured with steady鄄state pressure
sensor and K type thermocouples. The fuel con鄄
sumption was measured with MF鄄3200 fuel con鄄
sumption.
In order to simulate the combustion process
( pump wheels and pump axle) and turbine ( tur鄄
in the cylinder under the dynamic conditions more
Based on Newton蒺s law, a mathematical
curve changed with the engine speed and load
bine and turboshaft) moment of inertia.
model of hydraulic torque converter in dynamic
state can be expressed as
M DP = M HP + 籽F Py
M DT = M HT - 籽F Ty
dQ ( J P + J Py ) d棕 P
+
,
dt
dt
dQ ( J T + J Ty ) d棕 T
,
dt
dt
(3)
(4)
where M HP and M HT are respectively the dynamic
hydraulic torque of pump and turbine under the
unsteady operation condition; J Py and J Ty are the
moment of inertia of working fluid in pump and
turbine; F Py and F Ty are shape factor of the geo鄄
metric parameters of flow channel between the
pump and turbine蒺s blades. Q is the circulation
flow rate of fluid in the torque converter working
chamber.
accurately, the combustion heat release rate
changes during the dynamic simulation of en鄄
gine [9] . Depending on the test data of the com鄄
bustion heat release rate curve in different engine
operating conditions, the three Weber combustion
models of the GT鄄Power were studied to deter鄄
mine the value of each parameter. By selecting a
different operating point, we got the combustion
model under different conditions, with the inter鄄
polation methods to obtain the point between the
two operating point and to get the variation of the
engine combustion heat release rate under differ鄄
ent conditions. Map of main combustion and
quality factor are respectively shown in Fig. 1 and
Fig. 2.
Mathematical formula of gearbox model can
be expressed as
Ti - J
dN i T o
= ,
dt
ig
Ni = No ig ,
(5)
(6)
where T i and T o are the input and output torque of
gearbox, N i and N o are the input and output rota鄄
tional speed of gearbox, i g is the transmission ra鄄
tio, J is the gearbox moment of inertia.
Fig. 1摇 Map of main combustion duration
Since the engine speed changes with the ex鄄
3摇 Experimental research
A test bench was designed and established,
ternal load under dynamic conditions, a fixed a鄄
mount of fuel injection in a cycle can爷 t meet the
— 173 —
Journal of Beijing Institute of Technology, 2013, Vol. 22, No. 2
Fig. 2摇 Map of main combustion quality factor
Fig. 4摇 Injection advance angle map
requirements of the model. So we need to change
less torque sensor nodes, gateways BeeNet net鄄
the cycle fuel to achieve the changes of engine
speed and load under dynamic conditions. If the
map figure of cycle fuel in different speed and
load is given, we can change the fuel under dif鄄
ferent conditions. Under the dynamic condition,
the injection advance angle should be changed
with the changes of engine speed and load ac鄄
cordingly. If the map figure of the injection ad鄄
vance angle under different speeds and loads is
given, we can achieve the different injection ad鄄
vance angles under different conditions. The cy鄄
cle fuel map and the injection advance angle map
are shown in Fig. 3 and Fig. 4.
The flywheel鄄side gap of the engine in the
tracked vehicles power compartment used in this
test is small, so it 爷 s difficult to install torque
measuring device. We don爷 t measure the torque
of engine output shaft directly, but measure the
torque of the gearbox output shaft. We select the
strain type torque sensor TQ101 of Bichuang
Technology to measure torque. The measuring
system of wireless torque sensor consists of wire鄄
work protocol, BeeData computer acquisition and
processing software.
Wireless torque sensor node is connected
with battery and strain gauges and fixed to the ro鄄
tation axis, directly measuring the strain of the
rotation axis, at the same time, transmitting the
strain to the gateway node with wireless, to get
the torque value with the use of acquisition and
control software. Wireless gateway is responsible
to transmit the received wireless data to a com鄄
puter for storage, analysis and processing via
computer interface. Wireless transmission elimi鄄
nates the noise interference caused by long cable
and slop ring, so the entire measurement system
has the high accuracy and noise immunity.
We installed the vehicle speed sensor and en鄄
gine speed sensor on the tested vehicle, and used
the PXI鄄6624 calculator / timer capture board to
collect signals of the vehicle speed and engine
speed. The board consists of eight 32 bit counter /
timers, and with optical isolation between chan鄄
nels, to support up to 48VDC input and output
signals. NI PXI鄄6624 can be used to perform
measurement tasks of a variety of counter / timer,
including event
calculation,
period / frequency
measurement, quadrature encoder position meas鄄
urement, pulse width measurement, pulse gener鄄
ation and pulse train generation.
The road slope was measured by MTi attitude
sensor from Xsens Technologies B. V in Dutch.
Fig. 3摇 Cycle fuel map
MTi is a small inertial measurement with compre鄄
hensive three鄄dimensional magnetometer, which
— 174 —
LUO Guo鄄liang( 罗国良) et al. / Analysis of vehicle powertrain dynamic performance
includes the processor that can do real鄄time cal鄄
culation of three鄄axis acceleration, angular speed
and magnetic field strength. Attitude sensor is
fixed on the vehicle chassis, and the front of the
vehicle is the x鄄axis direction, so the angle a鄄
round the y鄄axis is the road slope.
Transmission is automatic transmission with
torque converter. The solenoid valve of high鄄
speed shift controls the hydraulic system to imple鄄
ment shift. The information collection of gear is
the collection of the state of shift solenoid, shift
solenoid signal is digital, with state of 0 and 1.
PXI鄄6123蒺s multi鄄synchronous acquisition card
from NI Company is used in our test. It has a
dedicated analog to digital converter ( ADC) for
each channel, so we can acquire the most power鄄
ful capacity and higher multichannel accuracy. NI
PXI鄄6123 has 500 kHz adoption rate of each chan鄄
nel, four input ranged from 依 1郾 25 V to 依 10 V,
two 24鄄bit counter / timers and eight hardware鄄
timed digital I / O lines, which is suited for a varie鄄
ty of applications.
The comparison of the transmission output
shaft torque measured in the test and the simula鄄
tion is shown in Fig. 5. The comparison of the
simulated engine fuel consumption of time course
and the experimental values is shown in Fig. 6.
Comparing the torque of transmission output
shaft and vehicle fuel consumption, we can see
the experimental data fit well with the simulation
ones. So the model of simulation is satisfied for
the accuracy requirements of vehicle dynamic a鄄
nalysis.
Fig. 6摇 Fuel consumption comparison graph
4摇 Calculated results and analysis
摇 摇 Based on the revised model, this paper ex鄄
pound on research of engine and vehicle dynamic
process under actual working conditions. Two
typical working
conditions,
the
acceleration
process from 0 to 32 km / h and typical cycle
working condition of tracked vehicles, were in鄄
vestigated. Then matching dynamic function was
built to do simulations so that the simulation mod鄄
el can perfectly simulate the dynamic process un鄄
der the actual working conditions. Finally, we
formulated an action plan to improve the vehicle
performance in dynamic process.
4郾 1摇 Acceleration process from 0 to 32 km / h
A main reason for the poor dynamic perform鄄
ance of
turbocharged
diesel
engine
is
the
turbocharger蒺s lag in response. In the dynamic
process, when the energy of exhausts gets into
turbocharger, just a small part is transformed into
mechanical work used by compressor and a large
part is used to accelerate turbine rotor. The rota鄄
ry inertia of turbine rotor affects the acceleration
process. Figs. 7 - 10 compare different engine
speeds, intake air pressures, turbine speeds and
acceleration time of vehicle from 0 to 32 km / h re鄄
spectively. These graphs show the effect of rotary
inertia of turbine rotor on the acceleration
process. The original rotary inertia of turbine ro鄄
tor is 0郾 000 85 kg·m3 , and the decreased rotary
inertia of turbine rotor is 0郾 000 5 kg·m3 .
Fig. 5摇 Torque comparison graph
From Figs. 7 - 10 we can see, with the same
energy of exhausts, the turbine with a smaller ro鄄
— 175 —
Journal of Beijing Institute of Technology, 2013, Vol. 22, No. 2
tion performs better. Under this circumstance,
the time decreases when engine work under the
condition of maximal engine fuel injection vol鄄
ume, in other words, in the condition of minimal
coefficient of excess air. The engine thermal load
and exhausts decrease. Therefore, the output
torque of turbocharged diesel engine increases rel鄄
evantly and the acceleration ability of vehicle is
improved.
Fig. 7摇 Engine speed with different rotor inertias
In the process of engine test鄄bed experiment,
the cooling capacity of intercooler is stronger than
the cooling capacity of vehicle鄄mounted intercool鄄
er. Thus, in actual running process, the intake
air temperature is higher, and the intake air flow
is less than in experiment, result in decreasing of
air鄄fuel ratio, combustion performs deteriorate.
Especially in the acceleration process, engine in鄄
takes air flow later than fuel injection because of
Fig. 8摇 Acceleration time of vehicle from 0 to 32 km / h
rotary inertia of turbocharged diesel engine爷 s tur鄄
bine rotor. Thus the air鄄fuel ratio decreases, and
combustion performs deteriorate. Moreover, in鄄
creasing of intake air temperature and decreasing
of air amount in cylinder make the combustion
performs and engine instantaneous working condi鄄
tion poorer [10] . Under conditions of 330 K and
370 K, the speed variation in acceleration process
from 0 to 32 km / h and air flow variation are
shown in Fig. 11 and Fig. 12.
Fig. 9摇 Turbine speed with different rotor inertias
Fig. 10摇 Boost pressure with different turbine rotor inertias
Fig. 11摇 Vehicle acceleration process with
tary inertia has higher turbine acceleration speed
and stronger pressurization ability. Consequently,
the intake pressure in engine cylinder increases
rapidly because the intake air flow and air鄄fuel ra鄄
tio increase rapidly. The time of engine instanta鄄
neous working condition is shortened, combus鄄
different intake temperatures
From Figs. 11 - 12 we can see, as the intake
air temperature increases, the decrease of density
of intake air and air amount in a same volume
means the decrease of intake air flow. Conse鄄
quently, the intake air flow is less than the fuel
— 176 —
LUO Guo鄄liang( 罗国良) et al. / Analysis of vehicle powertrain dynamic performance
Fig. 12摇 Air flow rate with different intake temperatures
Fig. 13摇 Variation process of boost pressure
injected into cylinder required. Therefore, incom鄄
plete combustion becomes more seriously, and
engine performance was seriously weakened. Es鄄
pecially under instantaneous working condition,
engine intakes air later than fuel injection due to
the lag resulted from rotary inertia of turbine ro鄄
tor. Additionally, the effect of increasing intake
air temperature and a small air鄄fuel ratio is taking
into account. Thus the combustion performs dete鄄
Fig. 14摇 Variation process of air flow rate
riorate and engine performance weaken more.
4郾 2摇 Typical cycle condition of vehicle
In a typical cycle of vehicles, speed changes
frequently and the vehicle is often under the con鄄
ditions of acceleration or deceleration. So the ro鄄
tary inertia of turbine rotor has an impact on vehi鄄
cle performance in a typical cycle. Graphs from
Fig. 13 to Fig. 15 compare different boost pres鄄
sures, air flows and engine fuel consumption
rates for different turbine rotor inertia. The origi鄄
Fig. 15摇 Fuel efficiency of different rotary inertias
nal rotary inertia of turbine rotor is 0郾 000 85 kg·m ,
erbates the match of gas and air in the transient
0郾 000 5 kg·m3 . As shown in the graphs, the tur鄄
flow in entire cycle, in that, the air鄄fuel ratio be鄄
bine acceleration speed, consequently, the intake
combustion increases. Consequently, engine per鄄
the degree of incomplete combustion reduces,
temperature of intake air causes the increase of
tent. At the moment, the engine fuel consump鄄
economy performance. The increase temperature
economy.
ty, and the air mass flow rate in the inner cylinder
the engine air intake flow, therefore affecting the
will be insufficient, air鄄fuel ratio decreases, the
High temperature after intercooler not only exac鄄
Consequently, the engine emitted power is re鄄
3
and the decreased rotary inertia of turbine rotor is
process, but also has an effect on the air intake
bine with a smaller rotary inertia has higher tur鄄
comes smaller, and the degree of incomplete
air flow and air鄄fuel ratio increase rapidly. And
formance is weakened more [11] . The increase
and the engine蒺s power increases to a certain ex鄄
the engine fuel consumption, which leads to poor
tion will decrease, resulting some improvement in
of intake air causes the decreases of the air densi鄄
The temperature of intake air directly affects
will be reduced accordingly. Then air flow rate
air鄄fuel ratio and cylinder combustion process.
degree of incomplete combustion of fuel increase.
— 177 —
Journal of Beijing Institute of Technology, 2013, Vol. 22, No. 2
duced, and fuel consumption is increased. There鄄
References:
of the engine operating point in the universal
[1] 摇 Zhang Junzhi. Study on the hybrid simulation meth鄄
fore, the engine performs poorly. The distribution
od of engine dynamic test鄄used by simulation [ J] .
characteristic diagram is shown in Fig. 16. When
Transactions of CSICE, 2000,18(1) :1 - 5. ( in Chi鄄
the temperature of intake air is 330 K, the engine
operating condition is relatively economy. The
cooling capacity of the intercooler enhancement
nese)
[2] 摇 Mahmoud K G, Loibner E, Wiesler B, et al. Simula鄄
tion鄄based vehicle thermal management system鄄con鄄
cept and methodology, SAE Paper, 2003鄄01鄄0276
plays a big role in vehicle performance under the
[ R] . Warrendale, PA, USA: Society of Automotive
actual working condition.
Engineering, 2003.
[3] 摇 Chen Zhennan. Simulation study on environment a鄄
daptability of vehicle power system [ D ] . Beijing:
Beijing Institute of Technology, 2010. ( in Chinese)
[4] 摇 Gamma Technologies.
GT鄄power user蒺s manual
[ EB / OL ] . [ 2006鄄09鄄12 ] . http: 椅 wenku. baidu.
com.
[5] 摇 Xue Xingyu. Dynamic modeling and simulating of
turbocharged diezel engine [ D] . Beijing: Beijing In鄄
stitute of Technology,2009. ( in Chinese)
[6] 摇 Lei Jilin, Huang Zhiping. Working process simula鄄
tion and performance parameter optimization of
high鄄pressure common rail diesel engine [ J] . Vehi鄄
Fig. 16摇 Engine working condition points of different
cle Engine, 2011,5(196) :53 - 58. ( in Chinese)
intake air temperatures
[7] 摇 Liu Yongchang. Simulation of internal combustion
5摇 Conclusions
engine thermodynamics[ M] . Beijing: Mechanical In鄄
We comprehensively studied the dynamic
process of the vehicle power transmission device
and established a coupled model to carry out sim鄄
dustry Press,2001:107 - 112. ( in Chinese)
[8] 摇 Cheng Gang, Wang Hongyan. Modeling and smimu鄄
lating of vehicle trasmission system[ J] . Journal of
the Academy of Armored Forces Engineering,2005,
ulation. The results show that:
19(2) :59 - 63. ( in Chinese)
淤 Vehicle dynamics is largely influenced by
[9] 摇 Zhang Yongfeng, Luo Guoqing. Research on dynam鄄
key to improvement of the vehicle dynamic char鄄
cademy of Armored Forces Engineering,2006,20:32
the dynamic characteristics of the engine, so the
acteristics is to improve the engine 爷 s dynamic
characteristics.
于 From the quantitative comparative analy鄄
ic character of diesel engine[ J] . Journal of the A鄄
- 36. ( in Chinese)
[10] 摇 Zhang Zhiqiang, He Yongling, Han Zhiqiang,et al.
sis, the use of a turbine with a smaller rotary in鄄
ertia and the control of air after the intercooler in
low temperature, have a significant influence on
the improvement of vehicle dynamic acceleration
process and the fuel economy.
— 178 —
Analysis of the influence of plateau environment on
vehicle diesel and countermeasure [ J] . Equipment
Environment Engineering, 2009, 6(2) :27 - 32. ( in
Chinese)
( Edited by Cai Jianying)