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Automotive Sensors and Actuators
P.V.ManivannanPEI Lab, Mechanical Department
Automotive Electronic SensorsAutomotive Electronic Sensors
P.V.Manivannan
Precision Engineering and Instrumentation Laboratory
Mechanical Engineering Department
IIT Madras
Automotive Sensors and Actuators
2P.V.Manivannan
PEI Lab, Mechanical Department
The world has long passed the "dangerous level" for greenhouse gases in the
atmosphere. Earth's atmosphere can only stay this loaded with man-made carbon
dioxide for a couple more decades without changes such as mass extinction, ecosystem
collapse and dramatic sea level rises
James Hansen, NASA Scientist( To USA Congress )
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Automotive Sensors and Actuators
3P.V.Manivannan
PEI Lab, Mechanical Department
How to solve the man-made Environmental problems ? (Global Warming)
How to solve the man-made Environmental problems ? (Global Warming)
Reducing utilization of fossil fuel
Reduction in tail pipe emissions
Customer satisfaction
Automotive Sensors and Actuators
4P.V.Manivannan
PEI Lab, Mechanical Department
Trinity of Control SystemTrinity of Control System
Measurement
Algorithm (or) Computation
Control or actuation
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Automotive Sensors and Actuators
5P.V.Manivannan
PEI Lab, Mechanical Department
What is an Electronic Sensor ?What is an Electronic Sensor ?A sensing device which converts a physical, mechanical or optical energy into an electrical signal
The sensing device always extracts some energy from the measured medium – loading effect
A good sensors are designed such that the load effect minimal
The output electrical signal has to be conditioned using additional electronic amplifiers and filters
A Smart sensor is an integrated unit with the all the above elements along with signal processing capability.
Automotive Sensors and Actuators
6P.V.Manivannan
PEI Lab, Mechanical Department
Classification of Electronic SensorsClassification of Electronic SensorsResistance change : Strain Gauges, Resistance
Temperature Detector (RTD)
Capacitance change : Capacitive type displacement / Angle sensor
Inductance change : Inductive RPM sensor, Linear Voltage Differential Transformer
Piezo-electric effect : Piezoelectric Pressure transducer, Accelerometer, Knock sensor
Thermoelectric effect: Thermocouples
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Automotive Sensors and Actuators
7P.V.Manivannan
PEI Lab, Mechanical Department
Sensors in Electronic Engine Management System
Sensors in Electronic Engine Management System
Engine RPM sensorThrottle Position SensorManifold Pressure Sensor (MAP)Mass Air Flow (MAF) sensor O2 or Lambda sensorInlet air & Engine coolant temperature sensorsCrank Angle sensorHall effect sensorKnock sensor
Automotive Sensors and Actuators
8P.V.Manivannan
PEI Lab, Mechanical Department
Most important sensors used in a EMSMost important sensors used in a EMSThe basic sensors required by Electronic Fuel Injection system are:
Engine rpm sensorManifold Absolute-Pressure sensor (MAP)
or Mass Air Sensor (MAS) Throttle-Position Sensor (TPS).
CAM position sensor
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Automotive Sensors and Actuators
9P.V.Manivannan
PEI Lab, Mechanical Department
Electronic Fuel Injection (EFI)Electronic Fuel Injection (EFI)
The ECU of the EFI system needs to know is how much air the engine consumes under a given operating condition to inject the right quantity of fuel.
Three different measurement strategies have evolved to supply the computer with this basic information:
N AlphaSpeed DensityMass Flow metering
Automotive Sensors and Actuators
10P.V.Manivannan
PEI Lab, Mechanical Department
Electronic Fuel Injection (EFI)Electronic Fuel Injection (EFI)N – Alpha :
Look Table based (RPM, TPS value)Open loopGood at Wide open throttleIn-accurate at part throttle: No correction for intake air temperature variation, etc
Speed Density:Look table based with correction for air-density (RPM, load : manifold vacuum in kPa)ECU calculates airflow requirements by referring to a much larger (in comparison to an N Alpha system) preprogrammed lookup table, a map of thousands of values that equates to the engine’s volumetric efficiency (VE) under varying conditions of throttle position and engine speedLambda sensor for closed loop Idle control
Mass FlowDirectly measures the amount of air inducted into the engine. Constant temperature Hot wire Anemometer type The amount of current needed to heat the wire is proportional to the mass of air flowing across the wire. The mass-air meter also includes a temperature sensor that provides a correction for intake air temperature
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Automotive Sensors and Actuators
11P.V.Manivannan
PEI Lab, Mechanical Department
Inductive Speed sensorInductive Speed sensor
Automotive Sensors and Actuators
12P.V.Manivannan
PEI Lab, Mechanical Department
Opto electronic Engine RPM sensorOpto electronic Engine RPM sensor
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Automotive Sensors and Actuators
13P.V.Manivannan
PEI Lab, Mechanical Department
Hall effect sensorHall effect sensorThe Hall effect refers to the potential difference on opposite sides of a thin sheet of conducting or semi-conducting material through which an electric current is flowing, created by a magnetic field applied perpendicular to the Hall element.
Dr. Edwin Hall discovered this effect in 1879.
The ratio of the voltage created to the amount of current is known as the Hall coefficientand is a characteristic of the material in the element
Automotive Sensors and Actuators
14P.V.Manivannan
PEI Lab, Mechanical Department
Hall effect sensorHall effect sensor
Hall voltage VH = IB / endI is the current across the plate length, B is the magnetic flux densityd is the depth of the platee is the electron chargen is the bulk density of the carrier electrons.
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Automotive Sensors and Actuators
15P.V.Manivannan
PEI Lab, Mechanical Department
Hall Effect SensorHall Effect Sensor
Integrated smart sensor = sensor + amplifier in single package
Hall effect devices when appropriately packaged are immune to dust, dirt, mud, and water - better for position sensing than alternative means such as optical and electromechanical sensing
Automotive Ignition, fuel injection and wheel-rotation in ABS
If the magnetic field is provided by a rotating magnet resembling a toothed gear, an output pulse will be generated each time a tooth passes the sensor. This is used in modern automotive primary distributor ignition systems, replacing the earlier "breaker" points
Automotive Sensors and Actuators
16P.V.Manivannan
PEI Lab, Mechanical Department
Throttle Position Sensor (TPS)Throttle Position Sensor (TPS)
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Automotive Sensors and Actuators
17P.V.Manivannan
PEI Lab, Mechanical Department
Equivalent circuit of TPS sensorEquivalent circuit of TPS sensor
Automotive Sensors and Actuators
18P.V.Manivannan
PEI Lab, Mechanical Department
Throttle Position Sensor (TPS)Throttle Position Sensor (TPS)Throttle position sensors are typically mounted on the throttle body, directly to the end of the throttle shaft
The Throttle sensor supplies the ECU with information about idle status and driver demand.
This information is used by the ECU to make judgments about power enrichment, deceleration fuel cut-off, idle stability, and spark advance angle corrections
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Automotive Sensors and Actuators
19P.V.Manivannan
PEI Lab, Mechanical Department
Engine RPM SensorEngine RPM Sensor
Engine RPM information, along with information from the air flow or manifold pressure sensor, allows the ECU to calculate the engine's basic operating load.
Based on measured load, basic injection and spark advance angle are accurately calculated
5.604.633.603.042.604000
5.304.924.202.962.723000
5.204.163.442.922.682000
4.764.403.472.922.761000
10080694020
Throttle (%)RPM
Automotive Sensors and Actuators
20P.V.Manivannan
PEI Lab, Mechanical Department
Manifold Absolute Pressure sensorManifold Absolute Pressure sensor
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Automotive Sensors and Actuators
21P.V.Manivannan
PEI Lab, Mechanical Department
Manifold Absolute Pressure sensorManifold Absolute Pressure sensorIt measures intake air volume by monitoring changes in manifold absolute pressure, a function of engine load.
The sensor consists of a piezoresistive silicon chip and an Integrated Circuit (IC).
A perfect vacuum is applied to one side of the silicon chip and manifold pressure applied to the other side.
When pressure in the intake manifold changes, the silicon chip flexes, causing a change in its resistance. The varying resistance of the sensor causes a change in signal voltage
Automotive Sensors and Actuators
22P.V.Manivannan
PEI Lab, Mechanical Department
MAP sensor working principleMAP sensor working principle
12
Automotive Sensors and Actuators
23P.V.Manivannan
PEI Lab, Mechanical Department
Air flow sensorsAir flow sensorsMeasurement of amount air entering into the cylinder is necessary to control the fuel injected
The quantity of air entering into cylinder is proportional to inlet air temperature, Manifold pressure, speed and load
Most widely used air flow meters are:
Mass Air Flow (MAF) sensor
Vane Air Flow (VAF) sensor
Karmen Vortex Air Flow sensor
Automotive Sensors and Actuators
24P.V.Manivannan
PEI Lab, Mechanical Department
Hotwire Anemometer type MAF sensor Hotwire Anemometer type MAF sensor
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Automotive Sensors and Actuators
25P.V.Manivannan
PEI Lab, Mechanical Department
Hot wire Mass Air Flow sensorHot wire Mass Air Flow sensor
Automotive Sensors and Actuators
26P.V.Manivannan
PEI Lab, Mechanical Department
Working of Hotwire Anemometer type MAF sensor
Working of Hotwire Anemometer type MAF sensor
The primary components of the MAF sensor are a thermistor, a platinum hot wire, and an electronic control circuit.
The thermistor measures the temperature of the incoming air.
The hot wire is maintained at a constant temperature in relation to the thermistor by the electronic control circuit.
An increase in air flow will cause the hot wire to lose heat faster and the electronic control circuitry will compensate by sending more current through the wire.
The electronic control circuit simultaneously measures the current flow and puts out a voltage signal in proportion to current flow
Main advantage is that, the meter is insensitive to the density of the fluid
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Automotive Sensors and Actuators
27P.V.Manivannan
PEI Lab, Mechanical Department
Vane type Air Flow MeterVane type Air Flow Meter
Automotive Sensors and Actuators
28P.V.Manivannan
PEI Lab, Mechanical Department
Vane type Mass Air Flow sensorVane type Mass Air Flow sensor
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Automotive Sensors and Actuators
29P.V.Manivannan
PEI Lab, Mechanical Department
Vane type Mass Air Flow sensorVane type Mass Air Flow sensorPlaced in series with the throttle body and a potentiometer is used as a measuring deviceIdle speed adjustment and inlet air temperature sensor are build-inIntake air volume is a direct measure of the load placed on an engine and the meter measures air volume, not massBy measuring the air temperature and pressure to determine air density, a true mass airflow calculation can be achieved using ideal gas law. ECU uses this parameter for calculating the fuel quantity and ignition timing
Automotive Sensors and Actuators
30P.V.Manivannan
PEI Lab, Mechanical Department
Karman Vortex type MAF sensorKarman Vortex type MAF sensor
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Automotive Sensors and Actuators
31P.V.Manivannan
PEI Lab, Mechanical Department
Working principle of Karman Vortex Airflow Meter
Working principle of Karman Vortex Airflow Meter
Automotive Sensors and Actuators
32P.V.Manivannan
PEI Lab, Mechanical Department
Working principle of Karman Vortex Airflow Meter
Working principle of Karman Vortex Airflow Meter
When air passes through the air flow meter, the vortex generator creates a swirling of the air downstream.
This swirling effect is referred to as a "Karman vortex."
The frequency of this Karman vortex varies with the velocity of the air entering the air flow meter.
The photo-coupler and metal foil mirror are used to detect changes in these vortices.
The metal foil mirror is used to reflect light from the LED to the photo transistor. The foil is positioned directly above a pressure directing hole which causes it to oscillate with the changes in vortex frequency.
The resulting digital signal is a 5 volt square wave which increases in frequency in proportion to increases in intake air flow.
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Automotive Sensors and Actuators
33P.V.Manivannan
PEI Lab, Mechanical Department
Karman Vortex AFM internal circuit and output signal
Karman Vortex AFM internal circuit and output signal
Automotive Sensors and Actuators
34P.V.Manivannan
PEI Lab, Mechanical Department
Air Intake temperature sensorAir Intake temperature sensorAn intake air temperature monitor is necessary in the EFI system because the pressure and density of air changes with temperature.
Depending upon inlet air temperature, the ECU calculates the necessary fuel correction value and adjusts injected fuel quantity (fuel correction program)
AIT : Normally thermistor type which forms an integral part of the MAF sensor
The sensing element is a Thermistor:Oxides of Cobalt, Nickel, BismuthNegative temperature coefficient
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Automotive Sensors and Actuators
35P.V.Manivannan
PEI Lab, Mechanical Department
Engine Coolant temperature sensorEngine Coolant temperature sensorEngine coolant temperature sensor or Water Temperature Sensor (THW) is typically located near the cylinder head water outlet.
Monitors engine coolant temperature using thermistor
The thermistor has a negative temperature coefficient (NTC), so its resistance value decreases as coolant temperature rises
Automotive Sensors and Actuators
36P.V.Manivannan
PEI Lab, Mechanical Department
Engine Coolant temperature sensorEngine Coolant temperature sensorThe coolant temperature sensor is required because fuel vaporization is less efficient when the engine is cold.
Internal engine friction is also higher during cold operation, increasing operating load.
The THW signal is used by the ECU to determine how much fuel enrichment correction is necessary to provide good cold engine performance.
19
Automotive Sensors and Actuators
37P.V.Manivannan
PEI Lab, Mechanical Department
Stoichiometric ratio Stoichiometric ratio By definition it is the ratio where the fuel is exactly completely consumed by the oxidizer present (normally atmospheric oxygen.)
As the mixture passes from rich, through stoichimetry and on to lean, the CO and HC emission declines while the NOX stays low until the lean side of stoichimetry.
All three are sufficiently low at stoichimetry that a three way cat can clean it up. The three way catalytic converter REQUIRES stoichimetry in order to work.
The Stoichiometric ratio of gasoline can vary from 14:1 to 16:1depending upon type of gasoline composition.
It is varies for different fuels. eg: Methanol is 11:1.
Automotive Sensors and Actuators
38P.V.Manivannan
PEI Lab, Mechanical Department
Lambda SensorLambda Sensor
A Lambda sensor is a device that measures the amount of oxygen in the exhaust gas. It is also called as O2 sensor
Lambda is simply the ratio of the current fuel:air and ideal (stochiometric) fuel:air ratio. Thus a lambda of 1 is stochiometric.
A lambda less than 1 is rich and more than one is lean.
A common term used in fuel injection circles is reciprocal lambda or gamma. This is convenient because it is >1 for richness.
20
Automotive Sensors and Actuators
39P.V.Manivannan
PEI Lab, Mechanical Department
Types of Lambda sensorsTypes of Lambda sensors
Two types of Lambda sensors:
Binary / narrow band Lambda Sensor: The sensor gives 0 volt when the engine runs lean and about 1 volt when the engine runs rich.
Linear or wide band Lambda sensor: Has a built in oxygen pump and heater circuit to achieve a very low change in output voltage even outside the stoichiometric ratio
The sensor directly measures the ratio of oxygen in the exhaust to the oxygen in a reference chamber normally vented to air
Automotive Sensors and Actuators
40P.V.Manivannan
PEI Lab, Mechanical Department
O2 / Lambda SensorO2 / Lambda SensorIt consists of a zirconium dioxide (Zr02) element sandwiched between two platinum electrodes. This sensor behaves very similar to a single cell battery. The electrodes act as the positive (+) and negative (-) plates, and the zirconium dioxide element acts as the electrolyte
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Automotive Sensors and Actuators
41P.V.Manivannan
PEI Lab, Mechanical Department
Characteristic curve of an Nernst Cell type O2 Sensor
Characteristic curve of an Nernst Cell type O2 Sensor
Automotive Sensors and Actuators
42P.V.Manivannan
PEI Lab, Mechanical Department
Working of Binary type Lambda sensorWorking of Binary type Lambda sensorDuring rich operating conditions, the inside, or positive plate, is exposed to a much higher concentration of oxygen than the outside, or negative plate.
The difference in O2 creates a difference in electrical potential, or voltage
When the air/fuel ratio becomes lean, the oxygen content of the exhaust gas increases significantly.
Because both plates are now exposed to a relatively high concentration of oxygen, electrons balance equally between the two plates. This eliminates the electrical potential between theplates.
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Automotive Sensors and Actuators
43P.V.Manivannan
PEI Lab, Mechanical Department
Internal construction of Lambda sensorInternal construction of Lambda sensor
Automotive Sensors and Actuators
44P.V.Manivannan
PEI Lab, Mechanical Department
Wide Band Lambda sensorWide Band Lambda sensorThey provide a precise indication of the exact air/fuel ratio, and over a much broader range of mixtures - all the way from 0.7 lambda (11:1 air/fuel ratio) to atmospheric air
oxygen sensors that uses a flat ceramic Zirconia element. It's called a "planar" sensor because the sensor element is a flat strip of ceramic that is only 1.5mm thick.
The electrodes, conductive layer of ceramic, insulation and heater are laminated together on a single strip
The new heater element also requires less electrical power and brings the sensor up to operating temperature in only 10 seconds.
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Automotive Sensors and Actuators
45P.V.Manivannan
PEI Lab, Mechanical Department
Linear Lambda sensor constructionLinear Lambda sensor construction
Automotive Sensors and Actuators
46P.V.Manivannan
PEI Lab, Mechanical Department
Wide Band Lambda sensorWide Band Lambda sensor
The Nernst cell still senses oxygen in the same way that a conventional thimble-type O2 sensor does.
To get the added precision, the oxygen pump uses a heated cathode and anode to pull some oxygen from the exhaust into a "diffusion" gap between the two components.
The Nernst cell and oxygen pump are wired together in such a way that it takes a certain amount of current to maintain a balanced oxygen level in the diffusion gap.
The amount of current required to maintain this balance is directly proportional to the oxygen level in the exhaust.
24
Automotive Sensors and Actuators
47P.V.Manivannan
PEI Lab, Mechanical Department
Wide Band Lambda sensorWide Band Lambda sensorWhen the air/fuel mixture is perfectly balanced at 14.7:1 (the stoichiometric ratio and lambda equals 1), the sensor produces no output current.
For a rich air/fuel mixture, the sensor produces a "negative" current that goes from zero to about 2.0 milliamps when lambda is 0.7 ( air/fuel ratio is near 11:1)
When the air/fuel mixture is lean, the sensor produces a "positive" current that goes from zero up to 1.5 milliamps as the mixture becomes almost air.
Automotive Sensors and Actuators
48P.V.Manivannan
PEI Lab, Mechanical Department
Lambda Sensor in EMSLambda Sensor in EMS
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Automotive Sensors and Actuators
49P.V.Manivannan
PEI Lab, Mechanical Department
Late response; any problem ?Late response; any problem ?More pollutants emitted during first few minutes of
engine warm-up.
The sensor does not begin to generate it's full output until it reaches about 600°F.
A typical zirconia sensor has a response time constant of under a millisecond
All these leads no control of emissions in a Gasoline engine inspite of having advanced EMS and Catalytic converter
Automotive Sensors and Actuators
50P.V.Manivannan
PEI Lab, Mechanical Department
Physical Location of a Lambda Sensor in an Engine
Physical Location of a Lambda Sensor in an Engine
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Automotive Sensors and Actuators
51P.V.Manivannan
PEI Lab, Mechanical Department
Piezoelectric Pressure transducer Piezoelectric Pressure transducer Certain crystals like Quartz produce electrical charges under mechanical loading
Crystals produce an electrical output only when they experience a change in load - Dynamic Measurements.
True static measurements are not possible
Quartz transducers, paired with adequate signal conditioners, offer excellent quasi-static measuring capability
Automotive Sensors and Actuators
52P.V.Manivannan
PEI Lab, Mechanical Department
Piezoelectric Pressure transducerPiezoelectric Pressure transducerQuartz piezoelectric transducers consist essentially of thin slabs or plates cut in a precise orientation to the crystal axes depending on the application.
Piezoelectric transducers incorporate a quartz element which is sensitive to either compressive or shear loads.
The shear cut is used for patented multi-component force and acceleration measuring transducers.
The transverse cut for some pressure transducers
The polystable cut for high temperature pressure transducers
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Automotive Sensors and Actuators
53P.V.Manivannan
PEI Lab, Mechanical Department
Different type of cuts in Quartz crystalDifferent type of cuts in Quartz crystal
Automotive Sensors and Actuators
54P.V.Manivannan
PEI Lab, Mechanical Department
Piezoelectric pressure transducer Piezoelectric pressure transducer
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Automotive Sensors and Actuators
55P.V.Manivannan
PEI Lab, Mechanical Department
Properties of Quartz crystal transducerProperties of Quartz crystal transducerQuartz is employed preferentially in transducer designs because of the following excellent properties:
high material stress limit, approximately 20,000 psi
temperature resistance up to 500°C
very high rigidity, high linearity and negligible hysteresis
almost constant sensitivity over a wide temperature range
ultra high insulation resistance (1014 ohms) allowing low frequency measurements (<1 Hz)
Automotive Sensors and Actuators
56P.V.Manivannan
PEI Lab, Mechanical Department
Charge amplifierCharge amplifier
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Automotive Sensors and Actuators
57P.V.Manivannan
PEI Lab, Mechanical Department
Typical Frequency Response Curve of Quartz transducer
Typical Frequency Response Curve of Quartz transducer
Automotive Sensors and Actuators
58P.V.Manivannan
PEI Lab, Mechanical Department
Why do we measure cylinder pressure ?Why do we measure cylinder pressure ?
Estimation of IMEP and Frictional losses
Study of pumping losses and the intake and exhaust strokes
Calculation of fuel burning rates
Estimation of gas pressures and temperatures
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Automotive Sensors and Actuators
59P.V.Manivannan
PEI Lab, Mechanical Department
Unwanted emissions from SI EnginesUnwanted emissions from SI EnginesCarbon monoxide: A poisonous gas that is colorless and odorless.
Hydrocarbons or volatile organic compounds (VOC's): Produced mostly from unburned fuel that evaporates. Sunlight breaks these down to form oxidants, which react with oxides of nitrogen to cause ground level ozone, a major component of pollution.
Oxides of nitrogen: Contributes to smog and acid rain, and also causes irritation to human mucus membranes
Automotive Sensors and Actuators
60P.V.Manivannan
PEI Lab, Mechanical Department
Three Way Catalytic Converter (TWC)Three Way Catalytic Converter (TWC)"Three-way" refers to the three regulated emissions it helps to reduce -- carbon monoxide, unburnt HC and NOx molecules.
The converter uses two different types of catalysts, a reduction catalyst and an oxidation catalyst.
Both types consist of a ceramic structure coated with a metal catalyst, usually platinum, rhodium and/or palladium.
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Automotive Sensors and Actuators
61P.V.Manivannan
PEI Lab, Mechanical Department
Catalytic Converter EfficiencyCatalytic Converter Efficiency
Automotive Sensors and Actuators
62P.V.Manivannan
PEI Lab, Mechanical Department
Internal Structure of Three Way Catalytic Converter ( TWC )
Internal Structure of Three Way Catalytic Converter ( TWC )
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Automotive Sensors and Actuators
63P.V.Manivannan
PEI Lab, Mechanical Department
Reduction CatalystReduction CatalystUses platinum and rhodium to help reduce the NOx emissions.
When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2.
The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2
2NO => N2 + O2 or 2NO2 => N2 + 2O2
Automotive Sensors and Actuators
64P.V.Manivannan
PEI Lab, Mechanical Department
The Oxidization CatalystThe Oxidization CatalystThe oxidation catalyst is the second stage of the catalytic converter.
It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst.
This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas
2CO + O2 => 2CO2
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Automotive Sensors and Actuators
65P.V.Manivannan
PEI Lab, Mechanical Department
Does the location matters ?Does the location matters ?One of the catalytic converter's biggest shortcomings is that itonly works at a fairly high temperature.
Place the catalytic converter closer to the engine. This means that hotter exhaust gases reach the converter and it heats up faster, but this may also reduce the life of the converter by exposing it to extremely high temperatures.
The converter is placed under the front passenger seat, far enough from the engine to keep the temperature down to levels that will not harm it.
Preheating the catalytic converter could be a good way to reduce emissions using electric resistance heaters.
Automotive Sensors and Actuators
66P.V.Manivannan
PEI Lab, Mechanical Department
Optical Crank Angle EncoderOptical Crank Angle Encoder
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Automotive Sensors and Actuators
67P.V.Manivannan
PEI Lab, Mechanical Department
Typical Crank Angle Encoder output signals
Typical Crank Angle Encoder output signals
Automotive Sensors and Actuators
68P.V.Manivannan
PEI Lab, Mechanical Department
Piezoelectric sensor internal construction and frequency response curve
Piezoelectric sensor internal construction and frequency response curve
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Automotive Sensors and Actuators
69P.V.Manivannan
PEI Lab, Mechanical Department
Knock Signal from Piezo sensorKnock Signal from Piezo sensor
Automotive Sensors and Actuators
70P.V.Manivannan
PEI Lab, Mechanical Department
Crank Angle EncoderCrank Angle Encoder
Crank angle information is needed for calculating Indicated Mean Effective Pressure (IMEP) and heat release
To plot Pressure -Volume diagram
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Automotive Sensors and Actuators
71P.V.Manivannan
PEI Lab, Mechanical Department
Knocking in EnginesKnocking in EnginesUncontrolled combustion in an Engine
results in very high rate of pressure rise and results in high pressure pulses. This phenomenon is called as Knock or ping
Reasons for knocking are:Higher compression ratio Fuel qualityHot spots inside the combustion chamber
Automotive Sensors and Actuators
72P.V.Manivannan
PEI Lab, Mechanical Department
Properties of knock signalProperties of knock signal
Knock frequency depends on the mass of the engine
Amplitude of the knock signal depends on the intensity of knock
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Automotive Sensors and Actuators
73P.V.Manivannan
PEI Lab, Mechanical Department
Hot spots inside the combustion chamberHot spots inside the combustion chamber
Automotive Sensors and Actuators
74P.V.Manivannan
PEI Lab, Mechanical Department
Type of Knock sensorType of Knock sensor
Microphone
Piezoelectric pressure sensor
Washer type knock sensor
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Automotive Sensors and Actuators
75P.V.Manivannan
PEI Lab, Mechanical Department
Knock Sensor (micro phone ) outputKnock Sensor (micro phone ) output
Automotive Sensors and Actuators
76P.V.Manivannan
PEI Lab, Mechanical Department
Cylinder pressure sensor outputCylinder pressure sensor output
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Automotive Sensors and Actuators
77P.V.Manivannan
PEI Lab, Mechanical Department
Output of a Knock sensorOutput of a Knock sensor
Vibration Signal During Knock
-40
-20
0
20
40
60
330 350 370 390 410
Crank angle (o)
Acce
lera
tion
(m/s
2 )
Automotive Sensors and Actuators
78P.V.Manivannan
PEI Lab, Mechanical Department
Washer type piezoelectric knock sensorWasher type piezoelectric knock sensor
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Automotive Sensors and Actuators
79P.V.Manivannan
PEI Lab, Mechanical Department
Piezoelectric cylinder pressure sensor used for heat release computation
Piezoelectric cylinder pressure sensor used for heat release computation
Automotive Sensors and Actuators
80P.V.Manivannan
PEI Lab, Mechanical Department
Conventional Electromagnetic type fuel injector
Conventional Electromagnetic type fuel injector
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Automotive Sensors and Actuators
81P.V.Manivannan
PEI Lab, Mechanical Department
Exhaust Gas Recirculation ( EGR )Exhaust Gas Recirculation ( EGR )The modern multi-valve, high compression engine can create NOx (Nitrous Oxide) during the high temperature combustion process.
NOx reacts with sunlight to create atmospheric problems such as smog and acid rain.
EGR is considered a `metered intake leak' and was developed to reduce the combustion temperatures to below 2,500 degrees, the threshold where NOx is created.
Automotive Sensors and Actuators
82P.V.Manivannan
PEI Lab, Mechanical Department
Vacuum-operated EGR valve Vacuum-operated EGR valve
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Automotive Sensors and Actuators
83P.V.Manivannan
PEI Lab, Mechanical Department
Exhaust Gas RecirculationExhaust Gas RecirculationThe EGR valve meters a readily available inert gas into the combustion chamber to effectively reduce the volume.
Smaller effective displacement means less fire, and less heat and thus lower temperatures.
The lower temperature inside the cylinder reduces formation of NOx emissions.
Automotive Sensors and Actuators
84P.V.Manivannan
PEI Lab, Mechanical Department
When EGR control valve is operated ?When EGR control valve is operated ?EGR reduces the volume of the combustion chambers and during sudden acceleration the EGR is turned off when you need full power (Wide Open throttle conditions).
At idle, the engine is very sensitive to air/fuel mixture ratios and swirl in the combustion chamber, so introducing EGR at idle is not on either.
During the cruise condition the Fuel/Air mixture is set as lean as possible for maximum economy and this in turn generates the highest temperatures, which leads to formation of very high level of NOx, pre-ignition and knocking.
At cruise, the EGR valve is operated in order to inject exhaust gas into the inlet manifolds to reduce emissions.
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Automotive Sensors and Actuators
85P.V.Manivannan
PEI Lab, Mechanical Department
Components of MPFI SystemComponents of MPFI System
Automotive Sensors and Actuators
86P.V.Manivannan
PEI Lab, Mechanical Department
Thank You