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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN
0976 – 6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
620
ADVANCED TURBOCHARGER TECHNOLOGIES FOR HIGH
PERFORMANCE DIESEL ENGINE - PASSANGER VEHICLE
APPLICATION
Pundlik R. GHODKE
1 , Dr. J. G. SURYAWANSHI
2
1* Research Scholar / DGM , Department of Mechanical Engineering , VNIT, Nagpur ,
Maharashtra, India /Mahindra Research Valley, Mahindra World city, Plot No 41/1
Chengalpattu, Tamilnadu, India
Email: [email protected]/[email protected] 2
Associate Professor, Dept of Mechanical Engineering, VNIT, Nagpur, Maharashtra, India
Email: [email protected]
ABSTRACT
Expectation in next coming years is CO2 emissions reduction for vehicles and demand for more
driving comfort are the challenges for the automobile industry. One approach to this problem is
the reduction of the displacement of the combustion engine while maintaining the characteristics
of large displacement engine. This method is often referred to using the term” downsizing” and
requires the engine to be turbocharged and improve performance and torque. It has been
demonstrated that a simple charging unit alone is not enough and it require more complex
charging systems when emissions are stringent. The goals of developed in terms of the
thermodynamics and operating of future passenger car viz increase in the power density of the
engine, highest possible maximum torque at low engine speeds across the widest possible range
of speeds, improvement of the driving response in transient operating condition like start up
response and elasticity response, reduction of the primary energy consumption during testing
and when driving on the road, observances of the future exhaust gas thresholds which mean a
drastic reduction in the current emission levels.
The latter goals can be reached through the use of smaller displacement engines. Engines with
low engine displacement yield significant advantages in the test cycles with respect to fuel
consumption and emissions, but the torque produced by small engine is pronouncedly less than
that of a large displacement, naturally aspirated engine must be attained in terms of the steady
state response and of the transient response. This paper summarizes review of advancements in
turbocharger technology to meet the demand of high performance and low emission of passenger
car vehicle application.
Keywords: Turbocharger, engine, emission, CO2, performance, VTG, VNT,
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND
TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 3, Issue 2, May-August (2012), pp. 620-632
© IAEME: www.iaeme.com/ijmet.html
Journal Impact Factor (2012): 3.8071 (Calculated by GISI)
www.jifactor.com
IJMET
© I A E M E
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN
0976 – 6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
621
1. INTRODUCTION
The thermodynamic demands placed on modern charging systems for diesel engines in passenger cars
result mainly from the target values of the steady-state and transient characteristics of the charged engine.
The emission values must be observed even when charged. A higher power and torque density result in
shift in the direction of the steady-state power and intermediate pressure generally require an additional
injection of a large amount of fuel in the cylinder and therefore a correspondingly higher air mass flow
rate i.e. higher charging pressure. The initial approximation of the increase in the air mass flow rate
required across the entire operating range of the diesel engine is equal to the realizable increase in
performance and intermediate pressure .An important demand placed on the charging system is therefore
to make a constant high pressure level available across the widest possible range of engine speeds. High
charging pressure at low engine speeds permit high intermediate pressures (Steady-state) to be attained
relatively quickly, which in turn contribute to the amount of surplus torque available and therefore the
acceleration response of the engine.
The airflow required for the rated output range can only be produced by charging device of a
corresponding large design. The design for a high charging pressure even at low engine speeds means in
contrast, however, that the compressor and turbine designs need to be relatively smaller .An ideal yet
impossible to realize reduction to this conflict is charging device for the compressor and turbine that is
continuously variable on the housing and rotor sides. A real possibility that is already the state of the art is
the well known method of designing the charging device with variable elements. Another significant
advance will be made possible by corresponding optimized multistage charging systems. Selected
multistage systems with different performance features will be prepared in addition to single stage units to
fulfill the future demands on diesel engines for passenger cars.
2. MODERN TURBOCHARGER DESIGN FOR PASSENGER CAR DIESEL ENGINE
2.1 Single stage charging systems.
In general modern diesel engines place particularly high demands on the charging system in terms of the
air flow required at various engine operating condition. The map width of flow compressor however
becomes increasingly smaller as the pressure ration increase so that the problem of having enough useable
map width arises, especially for high performance turbocharged engines .In the single stage charging
method, the selection of the compressor must therefore be based on the torque or rated output of the
engine. In the former case, the selected compressor can only deliver a high rated output over limited
range, which in the latter case there will not be enough steady state torque available at low engine speeds.
The limited useable compressor map width therefore represents and important and decisive restriction for
an improvement across the entire intermediate pressure curve. This means that an entirely vertical shift of
the intermediate pressure curve of the diesel engine to higher values is not possible with these simple
units. Refer figure 1 for single stage Boosting system.
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
0976 – 6359(Online) Volume 3, Issue 2, May
Figure No 1 : Single stage charging system
2.2 Variable turbine geometry
In single stage charging units,
passenger car diesel engines in addition to modern and economical turbochargers with boost pressure
control valves. The waste gate
engines and designed to meet the requirements of v
this type can also be equipped with a boost pressure control valve,
performance and emissions. Fig.
in the production of passenger car diesel engines
Figure 2
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
622
Figure No 1 : Single stage charging system
turbine geometry charging system
single stage charging units, turbochargers with variable turbine geometry are primarily us
in addition to modern and economical turbochargers with boost pressure
The waste gate turbocharger was developed especially for charging small combustion
to meet the requirements of variable turbine geometries. The turbochargers in
this type can also be equipped with a boost pressure control valve, depending on the requirements
Fig.2 shows a turbocharger with rotary blades (VTG) known for its use
oduction of passenger car diesel engines.
Figure 2 : Turbocharger with Variable Blades ( VTG)
– 6340(Print), ISSN
turbochargers with variable turbine geometry are primarily used for
in addition to modern and economical turbochargers with boost pressure
turbocharger was developed especially for charging small combustion
ariable turbine geometries. The turbochargers in
depending on the requirements of
(VTG) known for its use
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
0976 – 6359(Online) Volume 3, Issue 2, May
An interesting alternative to the VTG with rotary blades,
diesel engines, is the VST turbocharger with variable
there is a bypass valve integrated into the turbine housing for the upper operating range of the engine.
Figure 3: Turbocharger with Variable Turbine Geometry
At low engine speeds only the left duct of t
The efficiency of single flow, unregulated housing is reached in this manner. As the
flow increases, the right channel is constantly actuated by a regulating valve that moves axi
highest range of engines speeds, one control edge of the regulating valve opens a bypass from the right
channel of the turbine housing to the housing outlet. The yoke of a control rod converts rotational motion
introduced from outside of the housing to the axial motion of the regulating valve. The control rod can be
controlled by a pneumatic control box supplied with pressure,
First pass open
Figure
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
623
An interesting alternative to the VTG with rotary blades, especially for small displacement passenger car
is the VST turbocharger with variable slider ring turbine developed.Fig
there is a bypass valve integrated into the turbine housing for the upper operating range of the engine.
Figure 3: Turbocharger with Variable Turbine Geometry
At low engine speeds only the left duct of the double-flow turbine housing conducts exhaust gas (Fig
unregulated housing is reached in this manner. As the
the right channel is constantly actuated by a regulating valve that moves axi
one control edge of the regulating valve opens a bypass from the right
channel of the turbine housing to the housing outlet. The yoke of a control rod converts rotational motion
ousing to the axial motion of the regulating valve. The control rod can be
controlled by a pneumatic control box supplied with pressure, for example
Both Pass open both passes and bypass open
Figure 4: Operating states of VST Turbocharger
– 6340(Print), ISSN
especially for small displacement passenger car
slider ring turbine developed.Fig-3.In this design
there is a bypass valve integrated into the turbine housing for the upper operating range of the engine.
flow turbine housing conducts exhaust gas (Fig-3).
unregulated housing is reached in this manner. As the exhaust gas mass
the right channel is constantly actuated by a regulating valve that moves axially. At the
one control edge of the regulating valve opens a bypass from the right
channel of the turbine housing to the housing outlet. The yoke of a control rod converts rotational motion
ousing to the axial motion of the regulating valve. The control rod can be
both passes and bypass open
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN
0976 – 6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
624
To provide electrical motor drive power to the turbocharger a suitable electric motor is integrated into the
turbocharger shaft, for example between the turbine wheel and compressor impeller shown in figure 4.
This integrated system results in a noticeably improved transient response at operating points where there
is not much exhaust gas available in spite of the increase in the mass moment of inertia of the rotating
blades. The potential for improvement in the transient operating characteristics depends primarily on the
amount of electric power available and the electrical infrastructure of the vehicle. There are limits
,however, to this approach since improvement s in the steady-state torque curve can only be achieved
within the given compressor map limits due to the single stage processing of the system. The potential for
improvement with this concept is therefore limited when compared to other concepts.
2.3 Electrically driven flow compressors in combination with turbochargers.
This charging system was specially developed to improve the transient response at low engine speeds and
that , in addition to other goals, makes a significant contribution to the development of the future small
displacement engines with a transient torque response that approaches that of large displacement,
naturally aspirated engines.Fig.6 & 7 show the basic design. The e-Booster can be placed before or after
the turbocharger, although placing it before the turbocharger compressor shown in figure 6 provides more
flexibility in terms of the mounting position, while placing it after the exhaust turbocharger compressor
shown in figure 7 allows for shorter cable lengths.
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
0976 – 6359(Online) Volume 3, Issue 2, May
Figure 6 : Basic Schematic
The concept is based on a regulated, two
Booster) is connected in series with an exhaust turbocharger.
exhaust gas available, the two stage
Significant advantages result from the separation of the turbocharger and electrically driven charger when
compared to other approaches. Thanks to its electric drive,
the turbocharger and the thermal energy of the exhaust gases. The electrical system of the vehicle is the
only component that determines the maximum
gained using the e-Booster system in terms of the transient response ar
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
625
Figure 6 : Basic Schematic of e-Booster Before the Exhaust Turbocharger
gulated, two compression in which an electrically driven
in series with an exhaust turbocharger. At operating points where there is
stage compression reaches a higher overall charging pressure level faster.
Significant advantages result from the separation of the turbocharger and electrically driven charger when
Thanks to its electric drive, the e-Booster is completely
d the thermal energy of the exhaust gases. The electrical system of the vehicle is the
only component that determines the maximum amount of energy available. The advantages that can be
Booster system in terms of the transient response are only limited by the amount of
– 6340(Print), ISSN
ooster Before the Exhaust Turbocharger
compression in which an electrically driven compressor (e-
At operating points where there is little
g pressure level faster.
Significant advantages result from the separation of the turbocharger and electrically driven charger when
Booster is completely independent from
d the thermal energy of the exhaust gases. The electrical system of the vehicle is the
advantages that can be
e only limited by the amount of
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
0976 – 6359(Online) Volume 3, Issue 2, May
electrical power made available. An increase in the steady
contrast to the electrically driven turbocharger,
permanently by the vehicle electrical
the necessary charging pressure at the engine speeds below 2000 rpm,
charging pressure at the engine speeds above this value.
Since two centrifugal compressors are combined in this system, their maps can be combined, which then
substantially increases the total map width.
in a significant improvement in the transient re
need to be accelerated with the e-Booster,
therefore a high mass inertia does not have to be accelerated. Numerical simulations show that
consumption of the e-Booster system is about 30% lower than that if the electrically driven turbocharger.
The e-Booster can also be mounted at location where i
turbocharger turbine or a mechanical
The elimination of all lubrication and coolant connections was a requirement right from the start of the
development of the e-Booster shown
and one cable for control of addition to an intake and outlet connection fitting. All power electronics are
integrated into the e-Booster, which represents an important step towards electromagnetic compatibility.
2.4 Two-stage regulated Turbocharging
The main advantage of two stage charging systems over the single
compressors can be connected in series,
each airflow rate range. This then circumvents the restrict
The two stage regulated charger consists of two exhaust turbochargers of different sizes connected in
series shown in figure 9 .The advantage of this type of charging system over the single
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
626
electrical power made available. An increase in the steady-state torque at low engine speeds is possible, in
contrast to the electrically driven turbocharger, if the electrical power required can be made available
y by the vehicle electrical system. While the e-Booster and turbocharger combination supply
the necessary charging pressure at the engine speeds below 2000 rpm, the turbocharger alone supplies the
charging pressure at the engine speeds above this value.
ince two centrifugal compressors are combined in this system, their maps can be combined, which then
substantially increases the total map width. The separation of the turbocharger and electric motor results
in a significant improvement in the transient response since only the compressor impeller and the rotor
Booster, and a turbine wheel with a comparatively high density and
therefore a high mass inertia does not have to be accelerated. Numerical simulations show that
ooster system is about 30% lower than that if the electrically driven turbocharger.
Booster can also be mounted at location where it is not subject to a thermal l
turbocharger turbine or a mechanical load from the operation of the combustion engine.
The elimination of all lubrication and coolant connections was a requirement right from the start of the
Booster shown in figure 8. The e-Booster has only one cable for supplying power
ble for control of addition to an intake and outlet connection fitting. All power electronics are
which represents an important step towards electromagnetic compatibility.
Turbocharging
vantage of two stage charging systems over the single stage units is that two different sized
compressors can be connected in series, parallel & mixed way so that an optimized map is available for
This then circumvents the restriction of the limited useable compressor map.
The two stage regulated charger consists of two exhaust turbochargers of different sizes connected in
.The advantage of this type of charging system over the single stage
– 6340(Print), ISSN
state torque at low engine speeds is possible, in
if the electrical power required can be made available
Booster and turbocharger combination supply
the turbocharger alone supplies the
ince two centrifugal compressors are combined in this system, their maps can be combined, which then
The separation of the turbocharger and electric motor results
sponse since only the compressor impeller and the rotor
and a turbine wheel with a comparatively high density and
therefore a high mass inertia does not have to be accelerated. Numerical simulations show that the power
ooster system is about 30% lower than that if the electrically driven turbocharger.
t is not subject to a thermal load from the
the operation of the combustion engine.
The elimination of all lubrication and coolant connections was a requirement right from the start of the
le for supplying power
ble for control of addition to an intake and outlet connection fitting. All power electronics are
which represents an important step towards electromagnetic compatibility.
units is that two different sized
parallel & mixed way so that an optimized map is available for
ion of the limited useable compressor map.
The two stage regulated charger consists of two exhaust turbochargers of different sizes connected in
stage version is the
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
0976 – 6359(Online) Volume 3, Issue 2, May
increase in the rated output while simultaneously improving the steady state torque at low engine speeds
and the acceleration response of the passenger car diesel engine by quickly building up charging pressure.
The entire fresh air flow is compressed first
stage, the charging air is compressed further and then cooled. Due to the pre
relatively small high pressure compressor can reach a high pressure level so that it can f
amount of air flow through the system
Structural design of a two stag regulated charging system on a passenger car diesel engine
figure 10.
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
627
crease in the rated output while simultaneously improving the steady state torque at low engine speeds
and the acceleration response of the passenger car diesel engine by quickly building up charging pressure.
fresh air flow is compressed first by the low pressure stage in this design. In the high pressure
the charging air is compressed further and then cooled. Due to the pre-compression process, the
small high pressure compressor can reach a high pressure level so that it can f
system.
regulated charging system on a passenger car diesel engine
– 6340(Print), ISSN
crease in the rated output while simultaneously improving the steady state torque at low engine speeds
and the acceleration response of the passenger car diesel engine by quickly building up charging pressure.
In the high pressure
compression process, the
small high pressure compressor can reach a high pressure level so that it can force the required
regulated charging system on a passenger car diesel engine is shown in
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
0976 – 6359(Online) Volume 3, Issue 2, May
.Figure 10 : Two stage regulated charging system
With the use of a bypass on the exhaust side, for example a waste gate valve
LRK), it is possible to expand the entire exhaust mass flow using the high pressure turbin
some of the mass flow to the low pressure turbine located downstream.
At low engine speeds, meaning when the exhaust mass flow rate is low,
entire exhaust mass flow is fully expanded by the small high pressure turbine.
pressure that is built up quickly. The
flow is constantly transferred to the low pressure turbine by
regulated charging therefore allows for continues,
actual requirements of the operating engine.
Fig-11 shows a comparison of the measured intermediate pressure curve of the passenger car diesel
engine with two stage regulated charging to
with the variable geometry turbocharger (VTG)
with two stage regulated charging can be seen in fig
passenger car diesel engines with VTG turbocharg
stage regulated charging .
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
628
Figure 10 : Two stage regulated charging system
e exhaust side, for example a waste gate valve (German Abbrivation
it is possible to expand the entire exhaust mass flow using the high pressure turbin
some of the mass flow to the low pressure turbine located downstream.
ngine speeds, meaning when the exhaust mass flow rate is low, the bypass remains closed and the
exhaust mass flow is fully expanded by the small high pressure turbine. This yields a high charging
The exhaust gas mass flow increases, the work of expanding the mass
flow is constantly transferred to the low pressure turbine by increasingly opening the bypass. Two stage
regulated charging therefore allows for continues, variable adaptation of the turbine and compressor
of the operating engine.
shows a comparison of the measured intermediate pressure curve of the passenger car diesel
two stage regulated charging to that of passenger car diesel engine charged by a turbocharger
with the variable geometry turbocharger (VTG) with the same rated output. The potential of downsizing
with two stage regulated charging can be seen in figure 11.The plot of a standardized torque curve of two
passenger car diesel engines with VTG turbochargers is compared to that of a diesel engine with two
– 6340(Print), ISSN
(German Abbrivation is
it is possible to expand the entire exhaust mass flow using the high pressure turbine or to redirect
the bypass remains closed and the
This yields a high charging
ss flow increases, the work of expanding the mass
opening the bypass. Two stage
variable adaptation of the turbine and compressor to the
shows a comparison of the measured intermediate pressure curve of the passenger car diesel
that of passenger car diesel engine charged by a turbocharger
The potential of downsizing
torque curve of two
ers is compared to that of a diesel engine with two
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN
0976 – 6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
629
3. EVALUATING THE CHARGING SYSTEM FOR PERFORMANCE
An evaluation scheme for the various charging concepts can be created from the thermodynamic
requirements. The requirements results primarily from the steady state response and the transient response
of the turbocharged passenger car diesel engine.
With respect to the steady state response, the higher output density of the engine targeted requires a
parallel vertical shift of the entire power curve/intermediate pressure curve to higher values.
Consequently, an important evaluation criterion is whether or not a charging system can shift the entire
intermediate pressure curve upwards and if so, how far it can be shifted upwards.
There are some other important parameters from transient operations to be used in the comparison. These
parameters are the amount of startup ( low speed) torque the engine supplies at 1000 rpm, the acceleration
performance from 0-100 km/hr and the acceleration performance when in the upper gears(acceleration
from 60-100 km/hr and from 80-120 km/hr).
Table-1 shown below for the charging systems described is evaluated qualitatively in terms of the
criteria stated as the basis for an exhaust turbocharger with integrated damper control(Waste
gate/LRK),and the evaluation is then discussed after that.
Table 1 : Comparison of different Turbocharger system and selection criteria
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN
0976 – 6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
630
3.1 Shifting the intermediate pressure curve
In single stage charging, the shift of the entire intermediate pressure curve to a higher pressure level is
only possible within the prescribed compressor map limits. An engine charged with a VTG, VST and eu-
ATL turbocharger has no appreciable potential for increasing the steady state torque values when
compared to turbochargers with waste gates.
In the systems with two stages, the overall useable compressor map is substantially wider, which means
that it is possible to shift the intermediate pressure curve upwards. The e-Booster system in combination
with an exhaust turbocharger, being a two stage compression variant, basically allows an increase in the
intermediate pressure curve regardless of how much exhaust gas is available, although the potential
available from the electrical system of the vehicle is limited. Two stage regulated charging allows the
intermediate pressure curve to be moved upward across the entire speed range and there is also unlimited
availability of the higher torque when operating in the steady state.
3.2 Startup torque at and engine speed of 1000 rpm
There is no increase in the startup torque to be expected when a VTG or VST exhaust turbocharger is
used when compared to the basic version, but a satisfactory potential is offered by two stage regulated
charging when the high pressure turbine is designed accordingly.
The electrically driven designs have significant advantages over charging system driven only by exhaust
gas in terms of a high start up torque. The eu-ATL permits an improvement within the limits of its
compressor map. The greatest potential for improvement can be seen in the e-Booster concept. Realize
charging pressure depends mainly on the amount of electrical power supplied.
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN
0976 – 6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
631
3.3 Acceleration from 0 to 100 km/h
The perforrmance of a vehcile accelerating from 0 to 100 km/h primarily depends on the rated output of
the motor, which in turn depends on the amount of air availble in the motor and therrfore on the map of
the turbocharger compressor.
Assuming the compressor impellers are the same in the VTG/VST exhaust turbocharger, in the eu-ATL
and in the exhaust turbocharger of the e-Booster system, the same rated motor output is obtained in an
initial approximation for all engines charged in this manner. This means that all of the designs stated also
have about the same potential in terms of the acceleration from 0 to 100 km/h. However, it must be kept
in mind that the current design of the e-Booster unit is only active at engine speeds below about 2000
rpm. Since the limitation of a single compressor map is not present in two stage regulated charging. This
charging system offers the greatest potential for increasing the rated output and therefore for improving
the acceleration from 0 to 100 km/h
3.4 Acceleration from 60 to 100 km/h and from 80 to 120 km/h
A very important criterion used to evaluate an engine is its elasticity, which is usually assessed using the
acceleration performance from 60 to 100 km/h and or 80 to 120 km/h.In this case, turbochargers with
variable turbine geometries (VTG or VST) achieve perfectly satisfactory improvements in comparison to
the turbocharger with the waste gate(LRK).However, a substantially greater potential for increasing the
elasticity driven systems and two stage regulated charging, although the advantage of the electric system
increases as the amount of readily available extra power from the vehicle electrical system increases.
4. SUMMARY AND CONCLUSION
The thermodynamic demands placed on modern charging systems for diesel engines in passenger cars
result mainly from the criteria relating to the steady state and transient characteristics of the charged
engine. The increasing demands placed in the future on exhaust emission values must also be met, even
when charged. A higher output and torque density initially leads to the demand to shift the entire power
curve/intermediate pressure curve of the charged passenger car diesel engine to higher values.
Higher rated output and higher effective intermediate pressure require the injection of a large amount of
fuel into the cylinder and a corresponding high air mass flow rate, which is achieved through a higher
charging pressure. An important demand placed on future charging systems is therefore to make a high
pressure level available continuously across the widest possible range of engine speeds. A higher air flow
for the rated output range always requires a correspondingly large turbocharger in order to handle high
mass flow rates at high efficiency levels. Desire for a high charging pressure even at low engine speeds
means that the compressor and turbine designs need to be relatively small. In order to fulfill both these
contradictory demands, turbo suppliers is refining the designs of existing charging concepts with variable
turbine geometries with the goal of designing a single stage unit that operates at the limits of what is
technically possible.
Other leading modern charging concepts for passenger car diesel engines result in systems that are too
complex according to the current state of art. Expansion is possible with two stage systems (i.e.an e-
Booster in combination with an exhaust turbocharger and two stage regulated charging, the known limits
of single stage turbochargers, which results from a compressor map from just one single compressor).In
connection with the increase in the pressure ratio, these systems provide important characteristics that can
be used to meet the high demands placed on the future diesel engines.
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN
0976 – 6359(Online) Volume 3, Issue 2, May-August (2012), © IAEME
632
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