Upload
mubarak-albriki
View
219
Download
0
Embed Size (px)
Citation preview
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 1/17
SCHOOL OF ENGINEERING DESIGN AND
TECNOLOGY
NAME: Alexandros Alexandrou
U. B. NO: 06025724
COURSE: MSc MECHANICAL ENGINEEERING
SUBMISSION DATE: 18 DECEMBER, 2007
ENGINE AND POWERTRAIN
ENG 3037M
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 2/17
University of Bradford Engine and Powertrain (ENG 3037M)
Table of Contents
Page No:
Introduction………………………………………………………………………………………3
Objectives…………………………………………………………………………………………4
1. Engine
Definition…………………………………………………………………….............4
1.1 Specification of the Engine………………………………………………………………4
1.2 Characteristics of the Engine............................................................................................4
1.2.1 Petrol Engine..........................................................................................................4
1.2.2 Port
Injection......................................................................................................4-5
1.2.3 Exhaust Gas
Ignition…………………………………………………………….6
1.2.4 Three Way Catalytic Converter (TWCC)
……………………………………6-7
1.2.5 Activated Carbon
Canister……………………………………………………7-8
1.2.6 Variable Valve
Timing………………………………………………………...8-9
2. Specification of
EMS………………………………………………………………………...9
2.1 Input Sensors…………………………………………………………………………9-11
2.2 Output Actuators……………………………………………………………………11-12
Alexandros Alexandrou Page 2 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 3/17
University of Bradford Engine and Powertrain (ENG 3037M)
3 Calibration of
EMS................................................................................................................12
4 Operation of
EMS……………………………………………………………………….13-14
5 Discussion………………………………………………………………………………..14
-15
6 Conclusion..............................................................................................................................
15
References....................................................................................................................................16
Introduction
“An Engine Control Unit (ECU), also known as Engine Management System (EMS) is an
electronic system, primarily a computer, which controls an internal combustion engine by reading
several sensors in the engine and using the information to control its ignition systems”.
Engine management in general words is an approach to illustrate an electronically controlledengine system (ECU). The most important task of these systems is the continuous process control
in order to assure better fuel economy, emissions control, ignition timing, variable valve timing,
and boost level in turbocharged cars by sensors and actuators in order to have better performance.
Sensors usually give the input signal to the ECU where it is being processed and then it is sent to
the actuator.
The number and type of sensors and actuators that are being used from the engine control unit haveto be compatible with the precise engine that the ECU is controlling and the specific task.
Alexandros Alexandrou Page 3 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 4/17
University of Bradford Engine and Powertrain (ENG 3037M)
Figure 1: An ECU and its components
Objectives
The main objectives of this coursework are as follows:
To specify an EMS for the engine defined in section (6).
To describe the operation of this EMS.
To evaluate the requirements to calibrate the EMS.
To describe the operation of the EMS for a number of operating regimes of the engine.
1. Engine Definition
1.1 Specification of the Engine
Alexandros Alexandrou Page 4 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 5/17
University of Bradford Engine and Powertrain (ENG 3037M)
The EMS presented in this report is for a port injection turbocharged petrol engine, which utilises
variable valve timing, an exhaust gas ignition with activated carbon canister and a three way
catalytic converter.
1.2 Characteristics of the Engine
1.2.1 Petrol Engine
Petrol engine is a spark ignition engine (SI) that uses pistons that are moving up and down in
cylinders. A mixture of air and petrol is inserted inside the pistons and are ignited. The pressure
that is produced by the gases from the ignition pushes the pistons down generating power. In a four
stroke engine the piston moves up and down four times in order to make a cycle. This motion of
the pistons rotates a crankshaft that transmits the power to the wheels of the car by the use of
transmission system of clutch, gearbox and final drive.
1.2.2 Port Injection
In a port injection engine the air/fuel mixture is injected inside the intake of the manifold as
opposed to direct injection engine the mixture is injected in the combustion chamber. The fuel is
injected directly into the intake valves simultaneously with the intake air and set up the air/fuel
mixture which is then penetrated in the cylinder each stroke the piston is doing.
The first injection system was introduced by General Motors and it was called central port
injection (CPI). This system came in order to replace the carburetor throughout time because of the
high fuel metering characteristics and as the automobile evolved, carburetors became even more
complicated trying to handle all of the operating requirements. Central port injection sprays in the
cylinder through a nozzle continuously. Thus General Motors redeveloped CPI into a sequential
port injection system (SCPI) that uses the valves in order to measure the fuel going inside the
cylinder during intake and controlling time.
Despite that the system was still sticky because the valves were sticking all the time. That’s why
another system was developed called Multi-Port fuel injection (MFI) were using one injector in
each cylinder and sprays the pressurized fuel exactly above the intake valves. One very important
factor this system has is that it controls the amount and timing of the fuel injected in each cylinder.
Alexandros Alexandrou Page 5 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 6/17
University of Bradford Engine and Powertrain (ENG 3037M)
Figure 2: Components of Port injection Engine-control System
1.2.3 Exhaust Gas Ignition
Exhaust Gas systems are controlled by vacuum electronically depending on the application.
Exhaust Gas Recirculation (EGR) intend to reduce the level of NOx in the exhaust gas. This
emission increases by means of combustion temperature or lean burnt mixture.
The EGR system introduces calibrated amounts of exhaust gas into the intake system of the engine.
The unburnt fuel in the exhaust gas is driven in the combustion chamber for the next cycle. As this
proportion of exhaust gas has some usable energy less air/fuel mixture is required for the
combustion. This results to fuel economy and combustion chamber temperature drops as well as
NOx emissions. According to researches been done recently it is shown that engines with EGR, the
torque is increased.
Alexandros Alexandrou Page 6 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 7/17
University of Bradford Engine and Powertrain (ENG 3037M)
Figure 3: Typical EGR system
1.2.4 Three Way Catalytic Converter (TWCC)
A catalytic converter is used in automobiles in order to reduce the emissions exerted from an
internal combustion engine exhaust and pollutes the environment.
Three Way Catalytic Converter (TWCC) is the most common catalyst that is being used in spark
ignition engines. Is called three way due to the fact that is doing three tasks simultaneously:
• Reduces nitrogen oxides to nitrogen and oxygen.
• Oxidizes carbon monoxide to carbon dioxide.
• Oxidizes sunburn hydrocarbons to carbon dioxide and water.
The catalyst controls the amount of fuel being burnt and assures that the air/fuel ratio is slightly
above the stoichometric point. This ratio is between 14.8-14.9:1 for gasoline. When there is more
air than fuel then the system is said to be running lean and when there is the opposite is said to be
rich.
This stoichometric point can be achieved by operating an engine management system with lambda
sensors. The sensors can detect variations of air /fuel ratio and sends signals to the control unit that
generates the ratio to cycle quickly and bring the system to balance.
Alexandros Alexandrou Page 7 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 8/17
University of Bradford Engine and Powertrain (ENG 3037M)
Figure 4: Three Way Catalytic Converter
Three Way Catalytic Converter utilizes two types of catalysts. A reduction and an oxidation
catalyst. These are made generally from platinum and have a ceramic formation covered above
them.
1.2.5 Activated Carbon Canister
The operation of activated carbon canister is to absorb harmful hydrocarbons from atmosphere and
supply them back to the engine again when the engine is in operation.
Alexandros Alexandrou Page 8 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 9/17
University of Bradford Engine and Powertrain (ENG 3037M)
Figure 5: Activated Carbon Canister
1.2.6 Variable Valve Timing
Variable valve timing is an electronic and mechanical system that is being used in some engines
such as Honda VTEC and allows the engine to have multiple camshafts. These engines have an
extra intake cam with rocker that follows the cam. This concept keeps the intake valve open
longer. At low engine speeds the rocker is not connected to the valves although at high speeds the
piston locks the extra rocker to the other two rockers that control the two intake valves.
Some cars use a device that can advance the valve timing. This does not keep the valves open
longer instead; it opens them later and closes them later. This is done by rotating the camshaft
ahead a few degrees.
Alexandros Alexandrou Page 9 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 10/17
University of Bradford Engine and Powertrain (ENG 3037M)
Figure 6: The VTEC system Honda uses.
2. Specification of EMS
As it is mentioned before an ECU contains sensors and actuators that convert engines temperature,
pressure and other data information into digital or analog signals in order to control different
systems in an automobile engine.
2.1 Input Sensors
Oxygen Sensor (O2): changing voltage signal which allows the ECU to monitor the oxygen
content of the exhaust-gas (known also as Lambda sensor). Also provides information about the
fuel mixture. The ECU uses this to constantly re-adjust and fine tune the air/fuel ratio. This keeps
emissions and fuel consumption to a minimum.
Crankshaft Position (CKP) Sensor: Provides information on crankshaft position and the engine
speed signal to the ECU and helps the computer determine relative position of the crankshaft so the
Alexandros Alexandrou Page 10 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 11/17
University of Bradford Engine and Powertrain (ENG 3037M)
ECU can control spark timing and fuel delivery in the proper sequence. The ECU also uses the
crank sensor's input to regulate idle speed, or some engines have an additional camshaft position
sensor is used to provide additional input to the ECU about valve timing. Camshaft Position (CMP) Sensor: Produces a signal the ECU to identify the number 1 cylinder and to time sequential fuel injection.
Air/Fuel Sensor: works like Oxygen Sensors and is mounted to upstream of the catalytic
converter. It controls from the ECU the air-fuel ratio, in order to do this it needs a constant flow of
information about the amount of air flowing into the engine. The ECU will send out a signal to the
injectors to provide the correct amount of fuel.
Engine Coolant Temperature (ECT) Sensor: monitors engine coolant temperature and sends the
ECU a voltage signal that affects ECU control of the fuel mixture, ignition timing and EGR
operation. The ECU uses this information to regulate a wide variety of ignition, fuel and emission
control functions. When the engine is cold, for example, the fuel mixture needs to be richer to
improve drivability. Once the engine reaches a certain temperature, the ECU starts using the signal
from the O2 sensor to vary the fuel mixture. This is called "closed loop" operation, and it is
necessary to keep emissions to a minimum.
Intake Air Temperature (IAT) Sensor: provides the ECU with intake air temperature
information, in order to control fuel flow, ignition timing, and EGR system operation.
Throttle Position Sensor (TPS): senses throttle movement and position, and then transmit a
voltage signal to the ECU to determine when the throttle is closed, in a cruise position, or wide
open. The ECU uses this input to change spark timing and the fuel mixture as engine load changes.
A problem here can cause a flat spot during acceleration as well as other drivability complaints.
Mass airflow (MAF) Sensor: measures the mass of the intake air by detecting volume and weight
of the air from samples passing over a hot wire element. Problems with the airflow sensor can
upset the fuel mixture and various drivability problems (hard starting, hesitation, stalling, rough
idle, etc.) There are several types of airflow sensors including hot wire mass airflow sensors and
the older flap-style vane airflow sensors. All are very expensive to replace.
Alexandros Alexandrou Page 11 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 12/17
University of Bradford Engine and Powertrain (ENG 3037M)
Vehicle Speed Sensor (VSS): provides information to the ECU to indicate the vehicle’s speed.
This is needed to control other functions such as torque converter lockup. EGR Valve Position Sensor: monitors the position of the Exhaust Gas Recirculation pintle in
relation to the operating conditions of the EGR system. This allows the ECU to detect problems
with the EGR system that would increase pollution.
Vapour Pressure Sensor: the fuel tank is part of the evaporative emission control system and it is
used to monitor vapour pressure in the fuel tank. The ECU uses this information to turn on and off
the vacuum switching valves (VCV) of the evaporative emission system.
Power Steering Pressure (PSP) Switch: is used to increase engine idle speed during low speed
vehicle manoeuvres.
Knock sensors: are used to detect vibrations produced by detonation. When the ECU receives a
signal from the knock sensor, it momentarily retards timing while the engine is under load to
protect the engine against spark knock.
The manifold absolute pressure (MAP) sensor: measures intake vacuum, which the ECU also
uses to determine engine load. The MAP sensor's input affects ignition timing primarily, but also
fuel delivery
Transmission Sensors: the ECU on models with automatic transmission receive input signals
from a direct clutch (or input shaft) speed sensor.
2.2 Output Actuators
EFI Main Relay: activates power to the fuel pump relay, it is activated by the ignition switch andsupplies battery power to the ECU and the EFI system when the switch is in the Start Position.
Fuel Injectors: the ECU opens the fuel injectors individually. The ECU also controls the time the
injector is open (pulse width).
Alexandros Alexandrou Page 12 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 13/17
University of Bradford Engine and Powertrain (ENG 3037M)
Igniter: triggers the ignition coil and determines the proper spark based on inputs from the ECU.
Idle Air Control (IAC) Valve: controls the amount of air to bypass the throttle plate when the
throttle valve is closed or at idle position. The IAC valve opening and the airflow is controlled by
the ECU.
EVAP Vacuum Switching Valve (VSV): is a solenoid valve operated by the ECU to purge the
fuel vapour canister and route fuel vapour to the intake manifold for combustion.
Vapour Pressure Sensor Vacuum Switching Valve (VSV): is used by the ECU as part of the on-
board diagnostic check and during an emission test of the evaporative system.
3 Calibration of EMS
Calibration is the most important thing in an engine in order to run smoothly and effectively.
Calibration, also known as engine mapping is a procedure which sensors signals are processed by
the ECU and give the most appropriate result. These results are stored in the EMS and are used in
other processes to reduce time response.
The most important factor for an engine to run smoothly and effectively is the calibration. This
occurs through a procedure that signals from sensors of the engine are processed by the ECU and
accordingly give the ideal result every time. These results are stored in the EMS as tables and may
be used in next processes to reduce time respond. Once the data required is chosen then the output
signals are deployed. These signals are used by components that are going to make the adjustments
to the engine.
4 Operation of EMS
Alexandros Alexandrou Page 13 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 14/17
University of Bradford Engine and Powertrain (ENG 3037M)
Start from cold
Primary control throughout engine cracking
Fuel pump is filled with fuel to control pressure and when the pressure reaches the required fuel
line it switches off for safety reasons.
The speed of the engine at cracking is above 1500 rpm but below idle speed.
The engine coolant temperature is low; the air/fuel ratio is below stoichometric. Also the
microprocessors use calibration tables to run the engine taking measurements from temperature
sensors on the manifold.
The pressure inside the combustion chamber is equal to the atmospheric pressure.
Throughout this phase the turbocharger is not rotating and returns pressure to the system.
Idling
ECU controls the spark timing. Generally the lowest spark angle value is selected and that depends
according the data received.
The engine coolant temperature is still low but rising. As the temperature is still low the ECUkeeps the air/fuel mixture rich and when the temperature starts to rise keeps the mixture close to
stoichometric.
Rapid acceleration
Sensors time respond to the ECU creates a delay among the opening of the throttle and the
response of the system
Accelerator clamp occurs when the ECU adds extra fuel over short periods
Open loop is used by the ECU in order to adjust the control of fuel flow rate, ignition time and
spark angle in the engine
Alexandros Alexandrou Page 14 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 15/17
University of Bradford Engine and Powertrain (ENG 3037M)
W.O.T (Wide open throttle)
Spark timing is retarded
Zero losses from the pump
The pressure from the manifold is achieved by the turbocharger and depends according to the
specifications each manufacturer gives.
Engine Switched Off
Ignition and fuel pump switches off by the ECU when the engine is turned off
The cooling system works for a few minutes after the engine is turned off in order to cool down the
engine
5 Discussion
Engine Management System was developed in order to control and make sure the polluting
emissions created by the engine were reduced. Also improves the performance and provides fuel
economy.
These can be achieved by the use of different systems such as the three way catalyst, the most
common device used in a spark ignition engine, which controls the emissions in a gasoline engine
by reducing the polluting emissions.
The ECU can control the Ignition Timing, Variable Valve Timing and other regimes like start from
cold, idle speed, WOT, engine switched off. For each case the ECU is taking signals from
different sensors in order to control these operations.
Alexandros Alexandrou Page 15 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 16/17
University of Bradford Engine and Powertrain (ENG 3037M)
The power produced is regulated by the use of engine control. The driver controls engine power
via the accelerator pedal, which determines the setting of the throttle via a mechanical linkage
system. The throttle plate is situated in the air intake.
The power produced by the engine is proportional to the mass flow rate of air into the engine. Thedriver can control the engine power by controlling air mass flow rate going into the engine using
the throttle plate.
The power produced by the engine is also dependent on the fuel being presented in the correct
proportions. The fuel introduced to the air in the fuel-metering device.
The control of the spark timing is carried out by the ECU and is dependent on the data such as
load and rotational speed.
6 Conclusion
A turbocharged spark ignition engine can achieve high performance characteristics if is using a
good and complicated engine management system. This is not a turnover because it can maintain
fuel economy and exhaust gas emissions relatively to high speeds. New technologies applied to the
ECU and calibration process can achieve the tasks mentioned above.
Also consumer demands have forced the industry to rapidly develop engine management systems
in order to control the engine and exhaust emissions for better efficiency, performance, durability
and noise levels. Most modern systems use sophisticated control and monitor several engines
variables so the ECU can take the appropriate action.
Alexandros Alexandrou Page 16 of 17
8/2/2019 Course Work Report ENG 3037M
http://slidepdf.com/reader/full/course-work-report-eng-3037m 17/17
University of Bradford Engine and Powertrain (ENG 3037M)
References
1. Catalytic converters: http://www.madabout-kitcars.com/kitcar/kb.php?aid=381
2. Emissions Control: http://www.carcare.org/Emission_Control/egr.shtml
3. Dr. Seale, Engine and Powertrain (ENG3037M), lecture notes
4. Robert Bosch, (2004), Gasoline-Engine Management, 2nd edition
5. Engine Definition: http://www.autospeed.com/
Alexandros Alexandrou Page 17 of 17