Increasing Efficiency of SI Engine with Turbocharging and Electrical Assistance

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A RESEARCH PROPOSAL ON INCREASING THE EFFICIENCY OF AN SI ENGINE
A Proposal Paper on Efficiency
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Table of Contents
INTRODUCTION...........................................................................................................................................3
BACKGROUND.............................................................................................................................................4
SI Engine Efficiency..................................................................................................................................5
Turbocharging.........................................................................................................................................6
Turbines...............................................................................................................................................7
Compressors........................................................................................................................................8
Matching of Turbocharger...................................................................................................................9
METHODOLOGY.........................................................................................................................................10
Electrical assistance...............................................................................................................................11
Electrically assisted turbocharging system............................................................................................11
Recovery of Exhaust Energy...................................................................................................................13
Timeline.................................................................................................................................................15
ANALYSIS...................................................................................................................................................16
Energy Recovery....................................................................................................................................18
Safety Issues..........................................................................................................................................19
CONCLUSION.............................................................................................................................................19
BIBLIOGRAPHY...........................................................................................................................................21

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ABSTRACT
The transient performance and energy efficiency are two major factors in the locomotive
industry since they implement the two primary necessities such as drivability and consumption
of fuel. This research paper proposes the turbocharging system as a way of improving the
efficiency of an SI engine through energy recovery in exhaust gas and the turbocharger electrical
assistance concerning the transience operation. An electrical machine is coupled to the shaft of
the turbocharger through planetary gear which enables two modes of operations, namely
generator in energy recovery mode and motor in electrical assistance mode. The methodology
adopted for this research is the simulation of the transient for the module of electrical assistance
having three formations namely bigger turbine, bigger compressor, and standard turbocharger.
Steady-state simulations can be accomplished for the energy recovery module of exhaust gas at
part and full load with two alignments of the turbine, namely bigger turbines and standard
turbines.

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INTRODUCTION
Spark-ignition engine which is also abbreviated as SI engine is an engine of internal
combustion, normally petrol engine, where the combustion process of the ignition of the mixture
of air and fuel is performed by a spark from a spark plug. This is in disparity to the engine of
compression-ignition, such as diesel engine, where the compression generated heat and the fuel
of injection is sufficient to start the process of combustion, without the need of any exterior
spark. The transient performance and energy efficiency convey a main significance in the
locomotive industries since they implement the two main necessities, namely drivability and
consumption of fuel. A large percentage of energy from fuel is lost through exhaust gas in a
Spark-ignition engine hence affecting the consumption of fuel and engine efficiency.
The legislative requirements primarily demands the lowering of the level of CO2 and also
the consumption of fuel. However, reducing the consumption of fuel without sacrificing the
delivered performance level by the present automotive has become a challenge for all the
manufacturers of vehicles (Brejaud & Chamaillard, 2009). There are numerous probable
technical possibilities of decreasing the carbon (iv) oxide while reducing the effect on the
performance of the vehicle, these technologies include engine downsizing, improving the
transmission efficiency, reducing rolling coefficient and drag, electric vehicles, full hybrids, mild
hybrids, and micro-hybrids. Nevertheless, by minimizing the displacement of engine, the SI
engine will use a higher duration during operation at a higher efficiency (Guzzella & Onder,
2009).
The power reduction as a result of downsizing can be resolved through turbocharging.
Nevertheless, the major drawback of the operation of turbomachinery reflect into a deficit of
toque at low speed of the SI engine. This research proposal investigates the prospect of using

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turbocharger assisted electrically for increasing the torque to time operation in the low-end
torque and the prospect of increasing the efficiency of SI engine through the recovery of the
energy from exhaust gas (Voser & Onder, 2013).
BACKGROUND
Numerous car manufacturers are looking into the possibilities if improving the drivability
and the energy efficiency of the vehicles. One of the available options that are currently available
in the market is the SI engine downsizing correlated with turbocharging. Due to the ever-
expanding concerns regarding the depletion of the oil supply globally, a critical area of
development in the automotive industry is the improvement of the fuel efficiency in the vehicles.
Turbocharging a downsized SI engine has emerged as an effective approach of minimizing the
consumption of fuel with low sacrifices in its performance. This approach also provides benefits
of lower maintenance and manufacturing costs compared to other fuel-efficient schemes such as
hybrid vehicles and electric vehicles (Darlington & Cieslar, 2012).
Turbocharged SI engines have an undesired features such as low-pressure boost in the
region of low-end torque which affects the performance negatively. The forced induction
presents some interesting control and estimation problems, since the air dynamics of the
turbocharged setup are substantially more intricate compared to a naturally aspirated scheme.
There is also need of additional control valves so as to maintain the exhaust/intake manifolds
pressures in their respective ranges of operation desired. The KAIS Technologies and the Volvo
Cars Corporation provides a solution of multifunctional hybrid known as NESS which with its
sections like braking, stop, and start energy recovery, exhaust gas energy recovery, and electrical
assistance turbocharger (Davis, 2012).

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SI Engine Efficiency
It is common to group factors related to engine efficiency with their respective process
fundamentals such as friction losses, and thermodynamic factors. Such as by considering the
primary stage during the combustion of fuel, associated hear transfer, and volumetric expansion.
The factors related to this process can be categorized together as thermodynamic component
while numerous processes within the SI engine which moderate the positive work generated can
be categorized as either frictional losses or gas exchange losses. Thermodynamic factors include
working fluid properties, effective expansion, and combustion interval and these factors can be
used to improve the efficiency of the SI engine. Such as allowing a shorter combustion interval
for more combustion heat to experience more expansion and hence result in an increased positive
work (Davis, 2012).
The late exhaust valve opening and high compression ratios can be used in influencing
the ration of expansion so as to improve the SI engine efficiency. High specific heat ration of the
working fluid can also influence the SI engine efficiency. There are also pumping loses which
refers to the pressure gradient induced forces across the piston which opposes the normal
direction of piston during intake and exhaust strokes. The pumping losses affects the
consumption of fuel which occur during the intake stroke when the intake manifold and pressure
in the cylinder are almost equal (Katrašnik & Rodman, 2009).
Turbocharging
The maximum power of an SI engine depends on the quantity of fuel that can be burnt in
the cylinder efficiently. The fuel injected is dependent on the available quantity of air in every
cycle. Hence by air compression to a higher density will enable extra air in the cylinder.
Turbocharged systems are one of the traditional methods of improving density of air by raising
the pressure before getting in the SI engine cylinder. The turbocharging systems are composed of