HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY
SCHOOL OF MECHANICAL ENGINEERING
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REPORT: VEHICAL PROPULSION SYSTEM
Instructor: Assoc.Professor. Khổng Vũ Quảng
Class code: 144083
Group: 1
Members :
Lê Đức Anh 20210033
Lưu Bùi Việt Anh 20217542
Trịnh Tuấn Anh 20217545
Nguyễn Quý Đức 20217554
Nguyễn Trung Dũng 20217550
Nguyễn Quý Dương 20210239
Hanoi, January 2024
HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY
SCHOOL OF MECHANICAL ENGINEERING
---□&□---
REPORT: VEHICAL PROPULSION SYSTEM
Instructor: Assoc.Professor. Khổng Vũ Quảng
Class code: 144083
Group: 1
Members :
Full name Students’ Code Signature
Lê Đức Anh 20210033
Lưu Bùi Việt Anh 20217542
Trịnh Tuấn Anh 20217545
Nguyễn Quý Đức 20217554
Nguyễn Trung Dũng 20217550
Nguyễn Quý Dương 20210239
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Problem 1: Describe the difference between SI and CI engine in terms of :
1-Fuel properties
2-Engine operating, their structure, fuel atomization and detailed combustion
process
3-Engine knocking
4-Exhaust emissions
5-How do you think which is better mechanical design and thermal efficiency.
The difference between SI and CI engine is given below:
Differences SI Engine CI Engine
Fuel - Uses Gasoline - Uses Diesel
properties - Has high Octane rating and is - Has high Cetane rating and is
represented by Octane Number represented by Cetane Number (CN)
(ON) - Relies on compressing air-fuel
- Requires external ignition source mixture to ignite
for combustion
- Easily vaporizes and is highly - Is less volatile and flammable
flammable
Engine - Follows Otto Cycle - Follows Diesel Cycle
operating - Has 2 or 4 strokes: Intake; - Also has 2 or 4 above strokes
Compression; Combustion; and
Exhaust -Ignition method: Ignition occurs due
- Ignition method: Using spark plug to the heat generated by compressing
air. No spark plug is used.
- Air-Fuel mixture: Air is compressed
- Air-fuel mixture: Air and fuel are first, and then fuel is injected
mixed before entering the cylinder,
or if the engine uses GDI it operates
similar to that of CI engines - Combustion Characteristics: Relies
- Combustion Characteristics: on spontaneous ignition under high
Ignition is precisely controlled by a pressure and temperature.
spark plug.
Engine Contains: - Is nearly similar to the structure of
structure - Cylinder block SI Engine
- Connecting rod - No throttle body and spark plug
- Cylinder head included
- Piston ring - Using fuel injector to control
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- Crankcase engine speed
- Camshaft
- Crankshaft
- Valves
- Cylinders
- Injection system
- Combustion chamber
- Throttle body
- Spark plug
Fuel Has various types: Uses Fuel Injection only, which
Atomization - Caburetor engine - MPI includes
engine - Direct Injection
- SPI engine - GDI - Indirect Injection
engine - Common rail
Air-to-fuel ratio: Varies from 18:1 to
Air-to-fuel ratio: 14.7:1 80:1, depending on load and speed
Detailed 3 periods 4 periods
Combustion - Delay - Ignition Delay
Proccess - Main combustion - Premixed or rapid combustion
- After burning - Mixing controlled combustion
- Late combustion
Engine - Timing: Air-fuel mixture ignites - Timing: Related to poor
knocking prematurely, before the piston reach combustion control and irregular
TDC ignition.
- Causes: High compression ratios, -Causes: high compression ratios,
low-octane fuel, and high operating incorrect fuel injection timing,
temperatures inadequate air-fuel mixing, poor fuel
quality
Exhaust -NOx: Exhausts lower emissions - NOx: Exhaust at higher level than
Emissions compared to CI engines because of SI engines due to higher combustion
lower combustion temperatures, temperatures and excessive O in the
which results in less N oxidation. combustion process.
- Particular matter: Also exhaust at
lower levels since gasoline in SI - Particular matter: Produces more
engine tends to combust cleaner. particulate matter as properties to
- CO: As a byproduct of incomplete combust incompletely and the
combustion, SI engine generally presence of carbon particles.
produces more CO compared to CI - CO: Generally has lower emissions
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engines due to more complete combustion
- HC: Has higher levels of
unburned hydrocarbons, especially - HC: Generally has lower emissions
during cold starts or when the air- as the combustion process is often
fuel mixture is not well-mixed. more efficient.
-CO2: Produces lower CO2 since
gasoline has a higher H-to-C ratio - CO2: Tends to emit more CO2 per
than diesel unit of energy due to the higher
carbon content of diesel
- In terms of mechanical design, SI engine can be lighter since the engine structure
doesn't have to withstand high temperature and pressure like in CI engine. SI
engine can also achieve higher redline, increase its power potential.
- CI engine runs leaner mix compared to SI engine, and diesel fuel also has higher
energy density than petrol, thus CI engine has advantages in efficiency compared
to SI engine.
Problem 2:
Content: Architectures of HEV drive train
- HEVs are presently classified as follows: series hybrid, parallel hybrid, and
series– parallel hybrid.
Series hybrid drive trains:
Figure 2: Series hybrid electric vehicle
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- A series hybrid drive train is a drive train in which two electrical power
sources feed a single electrical power plant (electric motor) that propels the
vehicle.
- The unidirectional energy source is a fuel tank, and the unidirectional energy
converter (power plant) is an IC engine coupled to an electric generator.
- The output of the electric generator is connected to a power DC bus through a
controllable electronic converter (rectifier). The bidirectional energy source is a
battery pack connected to the power DC bus by means of a controllable,
bidirectional power electronic converter (DC/DC converter). The power bus is
also connected to the controller of the electric motor.
- The traction motor can be controlled as either a motor or a generator, and in
forward or reverse motion. This drive train may need a battery charger to
charge the batteries by wall plug‐in from a power grid.
a) Series hybrid electric drive trains potentially have the following
operation modes:
1. Pure electric mode: The engine is turned off and the vehicle is
propelled only by the batteries.
2. Pure engine mode: The vehicle traction power only comes from the
engine-generator, while the batteries neither supply nor draw any power
from the drive train. The electric machines serve as an electric
transmission from the engine to the driven wheels.
3. Hybrid mode: The traction power is drawn from both the engine
generator and the batteries.
4. Engine traction and battery charging mode: The engine-generator
supplies power to charge the batteries and to propel the vehicle.
5. Regenerative braking mode: The engine-generator is turned off and the
traction motor is operated as a generator. The power generated is used to
charge the batteries.
6. Battery charging mode: The traction motor receives no power and the
engine-generator charges the batteries.
7. Hybrid battery charging mode: Both the engine-generator and the
traction motor operate as generators to charge the batteries.
b) Advantages of series hybrid drive train:
- The engine is fully mechanical when decoupled from the driven wheels.
Consequently, the engine can be potentially operated at any point on its
speed–torque (power) map. This distinguished advantage, with
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sophisticated power flow control, provides the engine with opportunities
to be operated always within its maximum efficiency region.
- Because electric motors have a torque–speed profile that is very close to
the ideal for traction, as shown in torque‐speed curves, the drive train
may not need multi-gear transmission.
- Simplicity of drive train: The structure of the drive train can be greatly
simplified and is of less cost. Furthermore, two motors may be used, each
powering a single wheel, and the mechanical differential can be removed.
Consequently, the drivability of the vehicle can be significantly
enhanced.
- The control strategy of the drive train may be simple, compared to other
configurations,
because of its fully mechanical decoupling between the engine and
wheels. Flexibility of location of engine‐generator set.
- Suitable for short trips with stop and go traffic.
c) Disadvantages of series hybrid drive train:
- It needs three propulsion components: ICE. Generator, and motor.
- The motor must be designed for the max sustained power that the vehicle
may require, such as when climbing a high grade. However, the vehicle
operates below the max power
most of the time. The generator adds additional weight and cost. All three
drive train components need to be sized for max power for long distance,
sustained, high speed driving.
- A generator and motor are required, making the system heavy.
Parallel hybrid drive:
Figure 3: Parallel hybrid electric power train
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- The key of this configuration is that two mechanical powers are added together in
a mechanical coupler. The IC engine is the primary power plant, and the batteries
and electric motor drive constitute the energy bumper. The power flows can be
controlled only by the power plants—the engine and electric motor.
+ Advantages of the parallel hybrid drive train
- It needs only two propulsion components: ICE and motor/generator. Motor can
be used as the generator and vice versa.
- Most of the power is delivered mechanically, thus avoiding electrical losses.
- Peak performance is met using both systems, so that the electric machine can be
kept small.
- Only one electric machine is required.
+ Disadvantages of parallel hybrid electric power train:
- Engine cannot always run at its optimum operating point.
- A mechanical transmission is required.
- The configuration is harder to implement, with mechanical coupling and a more
complicated control system.
Series – parallel hybrid drive train:
The distinguished feature of this configuration is:
- The employment of two power couplers—mechanical and electrical.
- Actually, this configuration is the combination of series and parallel
structures, possessing the major features of both and more plentiful operation
modes than those of the series or parallel structure alone.
- On the other hand, it is relatively more complicated and may be of higher cost.
- Well ‐ to ‐ wheel efficiency is the same as in the parallel HEV and is about
24%.
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+ Advantages of series‐parallel hybrid power train
1) The engine is at optimal engine operation at all times.
2) Much of power (at cruising speed) is delivered mechanically to the wheels,
thereby increasing efficiency.
3) Charging is possible even when the vehicle is stationary.
4) Combined torque of the ICE and motor is available, improving performance.
5) Maximum flexibility to switch between electric and ICE pow.
+ Disadvantages of combined hybrid vehicles
1) Very complicated system and it is more expensive than parallel hybrid.
2) The efficiency of the power train transmission is dependent on the amount of
power being transmitted over the electrical path, as multiple conversions, each
with their own efficiency, lead to a lower efficiency of that path (~70%).
Problem 3: Describe the structure and system of hybrid electric vehicles.
I.Introduction of hybrid engine system:
- HEV, which use two power sources‐a primary power source and a secondary
power source have the advantages of both ICE vehicles and EV and overcome their
disadvantages.
- Hybrid electric vehicles combine electric and internal combustion engine drive.
Hybrid electric vehicles combine the zero pollution benefits of electric motors with
the high fuel energy density benefits of the thermal engine.
II.HEV principle:
- Overview structure of HEV principle: The term “hybrid electric vehicle” or
“hybrid vehicle” generally refers to vehicles that use an IC engine in conjunction
with one or more electric machines for vehicle
propulsion.
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Figure: 1 Hevs basic structure
- The primary energy conversion devices in an electric hybrid vehicle are the
IC engine, the electric machine, and the energy storage device.
- The electric machine can be used either as a motor or as a generator to
convert mechanical power to electrical power or vice versa.
- In fuel cell electric vehicles, the fuel cell is the engine that converts chemical
energy to an electrical form.
- The transmission in the vehicle is a key component for power transfer from
the IC engine to the wheels.
III.Main component of HEV:
Figure 1: classification of Hybrid vehicles
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1. Fuel tank: The fuel tank in a hybrid car serves as a storage unit for biofuel,
gasoline, or diesel, which are alternate sources of energy and power for the
vehicle. Its primary role is to ensure a portable supply of power, similar to
conventional gasoline cars. The design of the fuel tank depends on the type of
fuel and the vehicle's capacity and demand. Some hybrid vehicles use liquid
hydrogen as an alternate energy source.
2. Internal combustion engine (ICE): The internal combustion engine, also known
as the gasoline engine, combines the advantages of both gasoline and electric
vehicle technologies in hybrid vehicles. It generates power through the
combustion of fuel, converting heat energy into mechanical energy required for
the car's operation. The design and capacity of the internal combustion engine
depend on the vehicle's needs and specifications. It is often connected to the
electric motor and transmission components, collectively known as the
Integrated Motor Assist (IMA).
3. Electric motor: The electric motor is a vital component of hybrid cars,
responsible for propulsion and power generation. It relies on stored electricity
as one of its power supply options. The electric motor converts electricity into
mechanical energy, enabling the vehicle to accelerate and rotate the wheels. It
also assists in power storage by converting mechanical waste energy during
regenerative braking into electricity through electromagnetic induction. Electric
motors can be classified into AC and DC categories, with AC motors being
more commonly used due to higher efficiency and safety.
4. Battery: The battery system supplies stored power to various parts of a hybrid
car, primarily supporting the electric motor's operation. The battery system can
consist of one or multiple batteries, with voltage capacities ranging from 12V to
over 200V. Through regenerative braking, the battery system captures and
stores waste mechanical energy, contributing to energy conservation.
Depending on the design, hybrid car batteries can be recharged through
regenerative braking, the combustion engine, or external power sources in plug-
in hybrid electric vehicles (PHEVs).
5. Transmission: The transmission unit connects all power-supplying components
and directly supports propulsion in a hybrid car. It transfers mechanical energy
from the combustion engine and electric motor to the wheels. As the final
energy transfer route, the transmission controls the torque and alternation
between battery and gasoline power sources, affecting the vehicle's
performance and energy efficiency.
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6. Electric generator: Electric generators are components found in series hybrid
cars, where power supply systems are connected in series. They improve energy
efficiency by generating electricity from the mechanical rotation of other parts,
such as the electric motor shaft and wheels. The electric generator typically
generates power from the wheels during acceleration and braking, which is then
stored in the battery system.
7. Exhaust: The exhaust system in hybrid vehicles handles the gaseous byproducts
produced during operation. It releases these byproducts from the vehicle.
Exhaust systems in hybrids are designed to reduce emissions and improve
sustainability. Monitoring exhaust emissions can provide insights into the
performance of a hybrid car.
8. DC/DC Converter: The DC/DC converter plays a role similar to a conventional
inverter in a hybrid car. It converts power from one form to another as needed,
typically transforming high-voltage DC from the battery system or engine into
low-voltage DC used to power vehicle accessories. The use of converters in
hybrid cars aims to improve engine output and drive range.
9. Thermal regulation system: The thermal regulation system, also known as the
thermal management system, is responsible for managing the temperature of
various components in a hybrid car. It ensures cooling to prevent overheating of
sensitive parts like the electric motor, battery system, engine, and accessories.
Additionally, it provides heating to augment engine heat and warm the vehicle's
interior. The thermal management system conserves energy by minimizing heat
losses and maintaining optimal operational temperatures through the use of heat
transfer fluids and mechanisms.
10.Power Control Unit (PCU): The Power Control Unit, or power controller,
regulates the flow of electricity to all parts of a hybrid car. Its primary function
is to control the speed and torque of the electric motor, thereby influencing the
vehicle's performance. Working alongside the DC/DC converter, the power
control unit optimizes power supply within the vehicle.
Problem 4: Why do you study in “Vehicle propulsion system’’? What do you
think about your duty for the development of the “Vietnam automotive
industry” or “Vietnam's industrial development”?
1. Why do you study in “Vehicle propulsion system’’?
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The differences in performance between the first automotives and the modern one
are becoming more obvious, based on the development of “vehicle propulsion
systems”. So “vehicle propulsion systems” is a very interesting & important
subject.
“Vehicle propulsion systems” provide a wide range of knowledge:
1. In the first chapters, I have study about the tradition internal combustion engine
and its characteristics (components, Structure, operation, ignition process,…). I
also can calculate some simple problems involve kinetic (speed, acceleration);
thermodynamic; fluid dynamic,…
2. There is a chapter that help me a lot about charging systems like supercharger
and turbocharger.
3. In the last chapters I have learn about alternative fuel engine (electric vehicle,
hybrid vehicle and fuel cell vehicle); its applications and also its future in Vietnam.
4. Vehicle popularity (combustion engine, electric vehicle, turbine engine).
5. Models of the most significant vehicle propulsion systems' maneuverability and
fuel consumption (IC engines, batteries and fuel cells, short-range energy storages,
etc.).
6. A number of illustrations of cutting-edge powertrain designs and their
enhancement (fuel cell, hybrid electric, etc.).
7. The most important concepts of mathematical system optimization using vehicle
propulsion problems as examples. Several model classes of propulsion systems and
components.
8. The ability to access technologies for contemporary system optimization and
control of vehicle propulsion systems.
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After studying and understanding this subject, I can:
- Participate in the global automobile industry's development.
- Solve many serious and urgent problems, such as: improve efficiency of
engine, develop alternative fuel, reduce pollution from the engine…
- Apply the most recent system optimization and control tools to develop
vehicle propulsion systems.
2. What do you think about your duty for the development of the “Vietnam
automotive industry” or “Vietnam's industrial development”?
Though many lives are being greatly impacted by automobiles and technologies, it
is the duty of the next generation of engineers and technicians to influence the
growth of the automotive sector in our country in order to improve both society
and the environment.
My duty in particular and the duty for students in general:
- Obtain the most recent technical information and practical abilities in the fields of
relevant engineering, vehicle design, manufacture, testing, and manufacturing.
- Develop expertise in areas that play a significant role in shaping the future of the
automotive industry, especially to Vietnam's automotive industry, such as electric
vehicles, connectivity and telematics, lightweight materials, and autonomous
driving technologies.
- Keep an open mind and a growth-oriented perspective.
- During the study process, establish a network of contacts with engineers who
possess a high level of skill and experience. Talk about expertise, experience, and
career guidance with Vietnamese student communities as well as engineers on a
regular basis.
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In conclusion:
- I am getting geared to become the kind of automotive engineer that Vietnam's
rapidly expanding automobile industry sorely requires.
- Focusing on acquiring the right expertise, forming the right connections, and
developing the right mentality.
- Always willing to share my knowledge, experience,… with fellow engineers and
researchers.
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