HEV Engine Optimization PDF

HEV Engine Optimization 1
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Executive summary
Environmentally friendly cars having a wide range of performance abilities exceeding ordinary
and conventional vehicles need a careful and well-maintained balance among the most
competing objectives that will ensure high performance, emissions, and fuel efficiency. The
energy of deceleration can be recuperated for the vehicle to utilize it in battery recharge in the
energy storage hybrid electric vehicle (HEV) and boost the overall state of the batteries
depending on the new prevailing conditions of the braking phase of the vehicle. HEVs have
inbuilt power storage unit, which is used in reducing the needed peak power value from the
prime mover of the car, which forms part of the engine’s internal combustion chamber. This
paper investigates the existing relationship between recuperating energy and the driving cycle
stages of the Hybrid Electric vehicles to the inbuilt battery system of these cars. This works will
also offer various ways to integrate this electric vehicle into a simulated program. Different
methods of improving the overall performance of the vehicle will be posited. An optimization
design framework is used in the research paper to identify the most suitable position that can be
adopted to recuperate the energy of battery recharge in hybrid electric cars.

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Contents
Executive summary.........................................................................................................................2
Introduction......................................................................................................................................5
Problem statement.......................................................................................................................6
Objectives....................................................................................................................................8
Conceptual engine diagram.............................................................................................................8
Configuration description of an HEV..............................................................................................9
Detailed engine components analysis........................................................................................11
Electric motor........................................................................................................................11
Batteries.................................................................................................................................13
Main issues................................................................................................................................14
HEV Control..........................................................................................................................15
HEV energy management......................................................................................................19
Transmission..........................................................................................................................20
Assembled Drawing.......................................................................................................................21
HEV engine optimization..............................................................................................................21
Overview....................................................................................................................................21
Engine modeling process...........................................................................................................22
Mathematical modeling.........................................................................................................22

HEV Engine Optimization 4
Engine mathematical modeling.............................................................................................23
Gera shift process and working modes of the optimized powertrain....................................23
Engine working modes..............................................................................................................24
Electric Vehicle driving mode...............................................................................................24
HEV overpowered and underpowered driving modes...........................................................25
Performance validation..............................................................................................................27
Conclusion.....................................................................................................................................27
Future studies.............................................................................................................................28
References......................................................................................................................................29

HEV Engine Optimization 5
Introduction
Engine emission in automobiles is considered a significant factor in the discharge of
concentrated pollution in the world, especially in cities. However, the internal combustion engine
has remained the most preferred and the dominant automobile mover for technological adoption
and overall cost of production reasons (Zhang and Sheng 2016). Further, the ever-growing
dependency on fossil oil among the increasing concern regarding its overall environmental
impact of personal means of transportation has led to a global need by the governments to initiate
and sponsor various research into the creation of alternative vehicles to save on the overall
amount of the energy consumed, (Jeong, Kim, Lim, Park, Cha, and Jang, 2017). One of the new
automobiles is the creation of hybrid electric vehicles, typically including both the electric motor
and an internal combustion engine, with the primary objective of producing low emissions while
establishing a superior fuel economy around the globe.
As for engine improvement and optimization, numerous actions need to be taken, which include
optimization of the structure of the engine and the use of highly sophisticated engine control
approaches. Currently, HEV technology uses the Atkinson cycle as a mode of energy transfer in
the engine to obtain useful work. The Atkinson sequence is a tool of compensation for the engine
weakness observed in the Atkinson engine with the aid of the motor. Apart from the utilization
of the Atkinson cycle, other systems and technologies, which include the use of cold Exhaust
Gas Recirculation (EGR) and the installation of an optimized cylinder structure, are highly useful
in enhancing engine efficiency. Most of these technologies have been explored by companies
like Honda, Toyota, Hyundai, and Chevrolet.

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In addition to the use of spark ignition, the use of low-temperature combustion has shown signs
of improving the general motor fuel economic performance especially targeting hybrid vehicles,
where electrocution of the powertrain of the engine can give extra amounts of energy units to
propel the car and decouple the driver making the engine to function effectively and efficiently.
Great exploration has been conducted on the LTC engine in different perspectives. In a more
homogeneous charge compression ignition, the cell arrangement was put in a series form, and
three different energy management control was employed to gauge its influence on the fuel
consumption of the car.
In the modern technology-driven engineering modification world, an electro-mechanical
compound hybrid transmission offers an optimum mechanism to improve engine optimization
and maximize the overall performance of the vehicle. In relation to the traits of fast response,
pollution-free and increased adoption of LTC engine, the engine motor is highly suitable to serve
as an alternative source of power to the vehicle. Commonly, HEVs can be subdivided into three
different categories according to the cell’s arrangement in its electric engine compartment;
parallel configuration, series configuration, and series-parallel configuration.
Problem statement
HEV is an automobile having at least two propulsion means. One of these sources is the electric
energy. Most of the common designs in the market today include; electric motor, power control,
and a peaking device that comes in combination with the power units that include: sterling
engine/fuel cell, diesel engine, or spark ignition, (Kim, Kim and Kum 2015). Once the desired
components have been picked, they can be setup in several configurations. The components
arrangements can be put in the form of parallel and series

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Image: https://www.researchgate.net/figure/Configuration-of-the-power-split-HEV-system-
Diagram-adapted-from-12_fig1_283959333
A parallel HEV aids the motor and the engine to propel the wheels of the vehicle independently
or simultaneously. In the series arrangement, batteries can be recharged according to the control
strategy put in place. The configuration setup of the system requires a more concise system
engineering approach. In contrast, components design requires proper evaluation through
analysis of levels of contribution by the various components to the overall desired performance
levels.
Limited studies have been conducted concerning the component configuration of HEV with the
main aim of optimizing their performance and output. Any consideration of acquiring prototypes
will abnormally increase the required costs of production and research. The use of algorithms in
studying the efficiencies of HEV and the configuration of various components will expose the
areas that need reconfiguration for optimization of performances. Analysis of multiple
components such as energy storage systems, configuration modeling, and overall program

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simulation will require high costs to acquire their prototypes (Pei, Su and Zhang 2017).
Therefore, the adoption of the use of algorithms will help to decrease the total costs with reduced
limitations on carrying repeated research exercise. The purpose of the algorithm is preferred over
the use of expensive prototypes. It can be used to carry out simulations and identify the areas that
require reconfiguration to optimize the overall performance of the HEV.
Environmental pollution has attracted global attention, and the manufacturing of HEV offers a
solution to this menace. With the current efforts put in place to tackle the danger, it is essential to
adopt efficient and highly reliable HEVs to help in the reduction of strong emissions. Therefore,
it is crucial to upgrade the current engine configuration that will ensure performance
optimization.
Objectives
1. Understand the overall analysis of the hybrid engine
2. To reconfigure the arrangements of combustion components by modifying the engine
with the introduction of a multi-piston combustion chamber
3. Justify the findings and conclusion
Conceptual engine diagram
Energy and fuel combustion are initiated by the driver through the acceleration piston and during
the deceleration periods while driving. A contemporary image of the HEVs engine is illustrated
in the picture below, showing the flow of command that initiates the acceleration and
deceleration hence calling for energy combustion.

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Image: https://www.researchgate.net/figure/Configuration-of-the-power-split-HEV-system-
Diagram-adapted-from-12_fig1_283959333
Configuration description of an HEV
Besides, the overall analysis of the engine powertrain systems the HEV that tends that employs
rather simple models for the automobile components. I have considered analyzing an integrated
system simulation possessing high-fidelity sub configurations and various component models,
such engine models, transmission models, and the batteries used in the cars. The inclusion of this
individual subsystems extends the design components to specific components and subsystems.
High fidelity introduction leads to increased detail levels (Yadav and Gaur, 2016). Also,
particular elements of the engines can be carried out in refined details while closely monitoring
and tracking the overall impact of a local engine design, which is explained in this paper.

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A parallel HEV engine configuration with a double power path, so that the engines can be used
as a model of automobile propulsion as a single unit or can be used simultaneously to produce
the necessary power to turn the automobile wheels. In one scenario, the electric engine can be
used in covering short distances, and for longer trips, diesel-powered motors can be used as the
main source of energy to the car. The electric engine used as an auxiliary source of energy
assisting while climbing steep roads, increasing the overall reaction of the car to fast acceleration
and other instances when high power is required during the trip (Vinot, Reinbold, and Trigui,
2015). In such type of a vehicle, the engine can be reconfigured about the size of the car,
reducing the average weight and providing fuel efficiency to the fuel-dependent global economy.
The figure below illustrates a schematic configuration of the parallel engine. The engine consists
of both the fuel converter the electric motor that can individually or simultaneously propel the
car. The electric motor receives power supply from the pack of batteries in the car. This is a
typical configuration used in electrically driven vehicles. The engine has a hybrid addition in the
form of a fuel combustion chamber, which is usually an internal minor engine setup whose main
objective is to extend the overall range of the vehicle. When the battery charge is overused, the
fuel converter is used to recharge the batteries.

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Image: https://www.researchgate.net/figure/Configuration-of-the-power-split-HEV-system-
Diagram-adapted-from-12_fig1_283959333
Detailed engine components analysis
Electric motor
It is among the most complex and sophisticated items in the engine setup. In the advanced set up
of the HEV engine configuration, it acts as both the motor and the generator. Its primary function
is to draw energy from the batteries to be used in acceleration, and sometimes in advanced
service, revert the power to the cells during speed slow down. The motor operates through the
interaction of magnetic fields (Tang, Rizzoni, and Onori, 2015). It is fitted, and the electric
current passing through the engine that generates a shaft rotation. It consists of various parts,
which are illustrated in the image below.

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Image: http://oraresearch.com/2015/02/model-based-optimization-of-a-hybrid-electric-vehicle/

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Batteries
They are the primary source of energy for HEVs. However, technological advancement has
profoundly affected their use over time, and the whole process of inventing a better energy
source is ongoing. The commonly used batteries are the Ni-MH, lead-acid Li-ion batteries, and
Li-polymer batteries. The HEVs, the battery pack, is composed of several cells, (Michel, Charlet,
Colin, Chamaillard, Bloch, and Nouillant, 2017). All the cells are required to have similar SOC
at any given time, which will ensure that all the cells will have identical degradation rates and
possess the same energy capacity throughout their lifetime. The figure below shows an equalizer
type of battery cells

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Image: https://www.researchgate.net/figure/Configuration-of-the-power-split-HEV-system-
Diagram-adapted-from-12_fig1_283959333
Main issues
Compared to vehicles running on diesel engines, HEVs can save fuel through the following
ways;
i. They can store part of the kinetic energy produced in the batteries while speed
braking or on downsloping. The same power if otherwise is burnt in the brake’s pads
in the manifestation form of heat in diesel engine cars
ii. The engines of the HEVs can be built with a smaller displacement noble with little or
no compromise on the overall performance of the car

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iii. HEV consists of more than one engine system, and the main problem is on how to
optimize the engine power to realize the best fuel economy or achieve low strong
emissions at the lowest costs, which is commonly referred to as energy management
issues.
iv. HEV engines can make ICE run on a minimum efficiency point through the
regulation of power output of the batteries to satisfy power requirements of the
vehicle
HEV Control
The most fundamental feature of designing and developing the engine of an HEV is to obtain
optimum results with efficient control conversion of power in the engine’s powertrain. Hence,
the modified controller design of the engine is the critical point od the engine design process. the
primary aim of HEV engine design is to
i. ensure excellent drivability of the vehicle
ii. minimize the emission of concentrated gases
iii. minimize the levels of fuel consumption or maximize on the fuel economy
Car Control in HEV
The control system of an HEV car is highly complex. It contains a multilevel control system,
which is a highly relevant car control method for complex and large-scale systems. Thus, the
hierarchical control system method is highly adopted in the HEV control system and its
electronic controller, (Beyfuss, Hofmann, Geringer, and Grassl, 2019). The car system controller
is in control in deciding the torque demands of the engine motor, generator, mechanical brakes,
and the ICE according to the torque demand of the vehicle’s driver, speed of the car, and the
state of the battery charge (Stotsky et al., 207). Where the estimates of the battery management

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system determine the state battery charge, the speed of the car is fed to the sensor. The electronic
controller is the execution level to initiate and carry out the command from the engine system to
make the corresponding parts of the vehicle perform their functions.
Driver command interpreter
The major role of the driver command interpreter is to calculate the torque demand of the driver
in relation to the wanted speed of the car and the actual speed the car is at the current state. The
rate of the car is managed by the accelerator pedal and the position of the brake pedal (Song,
Lee, Kim, Yoo, Rhee & Min 2015). It is a feed control system through adjustment of the
accelerator pedal and the brake pedal positions to make the car respond to the desired speed.
Vehicle system controller
When compared to the conventional vehicles, HEV contains a multilevel engine setup, splitting
the required energy generated from these engines is commonly referred to as energy
management. The vehicle system controller manages the powertrain control by utilizing the

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energy management strategies as needed for the command signals received from the driver of the
vehicle through the driver command interpreter and the generated required feedback from the
electronic controller (US Department of Energy 2018). The vehicle system controller can be put
under three categories;
1. torque interpreter
2. energy management strategies
3. power requirement interpreter
vehicle power requirement interpreter is the function block to effectively convert the torque
demands of the driver to power demands. HEV, in its creation, is a multi-energy system which is
different from the conventional vehicles whose engines are only able to output, batteries can only
absorb the power, but also, they can output power (Ayers et al 2014). For the required strength in
the vehicle, splinting power requirements between the multilevel energy sources and the
mechanical brake system in the view of minimizing average fuel consumption or reduce the
amounts of emissions is the main topic of concern among technology enthusiasts.
The block diagram of the car’s control system can be illustrated as below

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Electronic controller
It is the embedded system that carries various commands from the vehicle system controller to
initiate functions of different corresponding parts. It includes an electronic braking system, an
engine control unit, a generator control unit, a motor control unit, and a battery management
system (Beltramello 2013).
The engine control unit is responsible for controlling the ICE. It enables the ICE required torque
that is received from the vehicle control system command sign by releasing fuel into ICE
combustion chambers, (National Service Center for Environmental Publication 2012). The
operating point of the ICE can be described in terms of speed and torque power. The motor
control unit makes the engine motor to operate at the desired torque power using the FOC
technology. Engine motors that are used for traction most of the time can be converted to the
generator during speed braking or downsloping (Buress et al., 2016). Therefore, the kinetic
energy, which is usually burnt during braking, can be converted to electrical power and is

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redirected to the batteries for storage. If the battery system of the vehicle becomes unreceptive to
the electric energy sent to them, the electronic braking system is called to duty.
HEV energy management
There have been several studies conducted to analyses the energy management for the HEVs.
Energy management is designed according to their efficiency and effectiveness in the
supervisory flow of power in the hybrid powertrain of the car (Edenhofer et al., 2014). The
powertrain supervisory control is set up following the intuition, heuristic, and relevant human
expertise. For instance, the maximum amount of torque power that can be produced in the ICE at
low speed and high speed (Tulpule, Marano, & Rizzoni, 2013). In addressing the energy
management issue, global optimal control retries are mostly adopted (Johnson 2013). HEV
energy management can be categorized into two main methods as indicated in the figure below

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Transmission
Transmissions are used when diesel is bunt to provide the required energy to drive the engine. It
is made up of clutches, shafts, and gears that carry out various functions, which include gear
selection.
Transmission layout

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Image: http://oraresearch.com/2015/02/model-based-optimization-of-a-hybrid-electric-vehicle/
Assembled Drawing
Assembled parallel HEVs engines are arranged in a way that both the ICE and the electric motor
are mechanically attached to the drive wheel of the car. This gives an advantage to the overall
drive system redundancy. If any of the systems fails, the other method will be available for
utilization and run the car for servicing.
HEV engine optimization
Overview
The parallel engine configuration of HEV is emphasized in analysis, which is indicated in figure
2 below, and the torque flow indicated in the figure show the prevailing conditions when the
diesel engine and the electric motor are used simultaneously to propel the vehicle (Solouk &

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Shahbakhti, 2016). Furthermore, the paper uses vehicle technical parameters as they are shown
in the following table (Image: https://www.researchgate.net/figure/Configuration-of-the-HEV-
hybrid-electric-vehicle-T-e-is-the-engine-output-torque-T-g_fig2_324990196)
Future influence on HEV engine powertrain architecture investigation can be viewed as an
optimal control issue whose optimization formula can be expressed as
J[x(t0), t0] = Z tf t0 L[x(t), u(t), t] dt + ϕ [x (tf), tf]
where t0 and tf are the initial and final time, u(t) is the control variable, x(t) is the state variable,
L[x(t), u(t), t] is the fuel consumption and ϕ [x (tf), tf] is the penalty function.
Engine modeling process
Mathematical modeling
The longitudinal alignment of the engine can be expressed as
Twheel = (mg f cosα + mgsinα + CDS 21.15 v 2 + δm dv dt) r
The torque equation is: Twheel = (Teigicge + Tmicgm) i0

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Engine mathematical modeling
According to the research information provided in the introduction, engine diesel consumption is
expected to continue decreasing in the future engine designs and technological progression. With
inspiration from the available research literature, an optimal engine map can be illustrated as
below;
Image: https://commons.erau.edu/cgi/viewcontent.cgi?article=1278&context=edt
Gera shift process and working modes of the optimized powertrain
Parallel engine configuration of HEVs has been used in numerous studies, and this study will
evaluate a parallel HEV powertrain configuration, which is indicated in the images shown below.
The first image shows that the gear ratio of the powertrain ig is made up of engine gear ratio ie and
motor gear ratio im. It can be calculated using the following formula; ig = ie · im. A starter motor
is fitted with an engine so that it can be switched on when it is needed (Williamson 2013).

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Image: https://commons.erau.edu/cgi/viewcontent.cgi?article=1278&context=edt
Powertrain architecture and gear ratios. 1. driven gear wheel of the main reducer; 2. half axle; 3.
first gear wheel; 4. first synchronizer; 5. driving gear wheel of the main reducer; 6. second gear
wheel; 7. electric motor; 8. third gear wheel; 9. first input transmission shaft; 10. second
synchronizer; 11. fourth gear wheel; 12. engine; 13. fifth gear wheel; 14. second input
transmission shaft; 15. six gear wheel; 16. dual-plate dry clutch; 17. output transmission shaft;
18. differential; ie: engine gear ratio; im: motor
Engine working modes
The powertrain architecture can operate on three modes; HEV overpowered driving mode, HEV
underpowered driving mode and electric vehicle (EV) driving mode
Electric Vehicle driving mode
The motor only supplies the demand power, and the diesel engine is not involved. The setup has
two gears, which are referred to as high-speed gear and low-speed gear (Liu & Peng 2016). In

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the low-speed gear, the torque is transmitted through the engine synchronizer. The torque is
transmitted to the vehicle through the clutch in the high-speed gear.
Image: https://commons.erau.edu/cgi/viewcontent.cgi?article=1278&context=edt
HEV overpowered and underpowered driving modes
Both the electric motor and the diesel engine get involved in supplying demand power, and the
transmission is transmitted through four gears fitted into the setup (Fontaras, Pistikopoulos, and
Samaras, 2016). In underpowered driving mode, both the diesel engine and the electric motor
supply-demand power, however, in the overpowered driving mode, the motor is used in charging
the batteries, and the engine is used to power the vehicle and drive the motor to charge the
batteries, (Hannan, Azidin, & Mohamed, 2014).

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Image: https://www.greencarcongress.com/2017/10/20171005-accord.html
To effectively utilize the available energy, HEVs use several mass reduction techniques and
aerodynamics, and car bodyweight is decreased using lightweight material. It is essential to use
the regenerative braking in restoring fuel used during car breaking (Yadav and Gaur, 2016).
Restored energy can thus be stored in a myriad of ways; it can be saved by compressing the
resulting air using a hydraulic motor or can be stored in ESS. Active regeneration of the energy
used in breaking down the speed of the car can mostly optimize the overall performance of the
HEV engine.

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Performance validation
To validate the performance of the ideal optimum engine powertrain architecture, the following
simulation model shows the parallel arrangements of engine parameters.
Image: https://www.greencarcongress.com/2017/10/20171005-accord.html
Conclusion
Energy crisis experienced in the world and the need for environmental protection has increased
the urge to develop EV. However, PEV is not globally used due to the dissatisfaction customer
realize from their usage given the high costs and short lifespan associated to them. This has led
to the development of hybrid cars mainly to cover short distances. According to the analysis of
HEV engine performance and composition, displaying various fields of braking energy
regeneration during the driving cycle is critical to optimizing engine performances. The IC
engine is majorly used in recharging the electric engine batteries during actual car driving.
Regenerative braking is essential to recovering valuable energy used. Furthermore, it is

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necessary for decreasing the amount of fuel used by the vehicle, which ultimately reduces
emission volumes.
Future studies
Improvement of the existing charging system
Development of batteries that are made up of non-toxic components and possess high power
density

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