Automobile Engineering- UNIT- 2-Engine Auxiliary Systems
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In automobile engineering, Engine Auxiliary Systems support engine performance, efficiency, and reliability. These include cooling, lubrication, fuel, ignition, exhaust, and electrical systems, ensuring smooth operation and longevity.
Automobile Engineering- UNIT- 2-Engine Auxiliary Systems
- 1. 20ME603PE- Automobile Engineering UNIT iI - ENGINE AUXILIARY SYSTEMS Prepared By Chandra kumar S Assistant professor Kongunadu college of engineering and technology
- 2. INJECTION SYSTEM • Fuel into the cylinders by means of a pump rather than by the suction created due the movement of the pistons is called fuel injection. • In SI engines, fuel-injection pumps are often used instead of conventional carburetors. • The primary difference between carburetors and fuel injection – is that fuel injection atomizes the fuel through a small nozzle under high pressure, – while a carburetor relies on suction created by intake air accelerated through a venturi tube to draw the fuel into the airstream. • Diesel engines do not use spark plugs to ignite the fuel which is sprayed or injected directly into the cylinders, instead relying on the heat created by compressing air in the cylinders to ignite the fuel.
- 3. Requirements of fuel injection system: The beginning as well as end of injection should sharply take place The fuel is atomized to the required degree. The fuel is distributed throughout the combustion chamber for better mixing The fuel is injected at correct time in the cycle INJECTION SYSTEM FOR SI ENGINE: 1. Multi-point injection system 2. Monopoint injection system. Multi-point injection system Monopoint injection system.
- 4. FUEL SUPPLY SYSTEM IN CI (DIESEL) ENGINE • In petrol engines, a carburetor is employed to mix air and fuel in the desired ratio. • But in Diesel engines, air alone is compressed in the cylinder • The high pressure is about 35 bar to 40 bar and the temperature of this air after compression is about 600°C. • The fuel is injected through fuel nozzle in fine atomized form at a pressure higher than the pressure of air. • Fuel injection system for a Diesel engine. • It consists of a fuel tank, fuel feed pump, fuel filter, fuel injection pump and injector. Fuel is pumped to the fuel injection pump from fuel tank through the fuel filter.
- 5. FUEL SUPPLY SYSTEM IN CI (DIESEL) ENGINE • Air injection system: – air is initially compressed to a very high pressure – The fuel is metered and pumped to the nozzle – This method is not used nowadays because of the complication and expensive system. • Airless or Solid injection: – greatly replaces the air injection method – The fuel under pressure is directly injected into the combustion chamber in atomized state – further be classified into the following two commonly used systems. (i) Unit injector system or individual pump system. (ii) Common rail direct injection system.
- 6. 1. Unit injector system or individual pump system. i) Fill Phase (fuel from the supply duct into the chamber) ii) Spill Phase (The plunger of the pump is on the way down , Fluid flow return to duct) iii) Injection Phase (Solenoid valve is energized , fluid flow is closed, The fuel cannot pass back into return duct and it is compressed by the plunger until the pressure exceeds specific "opening" pressure) iv) Pressure reduction phase ( fuel to return duct)
- 7. 2. Common Rail Direct Injection System (CRDI) • good fuel efficiency and low CO, emissions. • reduce harmful emissions • combustion takes place directly into the main combustion chamber • injects diesel five times more accurately than the normal injection • Various components of CRDI System are: 1.High pressure fuel pump 2.Common fuel rail 3.Injectors 4.Engine control unit.
- 8. 3. Rotary Distributor System: • The fuel pump supplies the required amount of fuel after metering it to a rotating distributor at the correct time for supply to each cylinder. • The fuel is distributed to cylinders in a correct firing order operated by poppet valves which are opened to admit the fuel to nozzles. Advantages: Easy maintenance, Balanced cylinder fueling Disadvantages: Overall reduced durability
- 9. 4. Distributor Type or CAV Fuel Injection Pump • measure and deliver the correct quantity of fuel at high pressure to the injector. • CAV fuel injection pump is most commonly used in diesel engines CONSTRUCTION: • It is a plunger type pump • reciprocating plunger which reciprocates inside the barrel • The plunger has a helical groove • The plunger is operated by a cam mechanism WORKING: • The plunger is moved up by a cam and return back to its initial position by a tension spring. • The plunger can also be rotated by the rack and pinion arrangement • Two ports are provided in the barrel. • One is known as supply port and the other is known as spill port • The fuel passage or outlet is connected to fuel injector. • supply port is opened, the fuel fills the barrel • The moving plunger first closes the supply and spill ports • the plunger is compressed and high pressure is developed • The remaining fuel in the barrel comes out through the helical groove when the plunger moves up
- 10. Distributor Type or CAV Fuel Injection Pump
- 11. 5. Fuel Injector • fuel injector is to deliver finely atomized fuel into the combustion chamber. • It also assists in bringing each droplet of fuel in contact with sufficient oxygen in the air. CONSTRUCTION: • A nozzle is connected with the housing by a nozzle cap • There is a plunger with a valve • It is connected with a spindle • Fuel passage connects the nozzle and pump WORKING: • High-pressure fuel from the pump comes to the nozzle end through the passage • Due to fuel pressure, the valve is lifted up against the spring force. • the hole in the nozzle is opened. • When the fuel pressure falls, it closes the hole of the nozzle
- 12. ELECTRONICALLY CONTROLLED INJECTION SYSTEM FOR SI ENGINES
- 13. ELECTRONICALLY CONTROLLED INJECTION SYSTEM FOR SI ENGINES It consists of the following four units: (i)Air intake or induction system (ii)Fuel delivery system (iii)Sensors and air flow control system (iv)Electronic control unit (ECU) •Engines uses sensors to monitor engine parameters like speed, load, and temperature. •This data is processed by an ECU (Electronic Control Unit) to calculate the precise fuel quantity and timing. •The ECU controls the fuel injectors to deliver an optimal air-fuel mixture to the combustion chamber. •This ensures improved performance, fuel efficiency, and reduced emissions.
- 14. ELECTRONICALLY CONTROLLED INJECTION SYSTEM FOR CI ENGINES Conventional systems only sense a few parameters and meter the fuel quantity or adjust the injection timing. Therefore, electronically controlled diesel injection systems have been developed. •This system facilitates the precise control of the following parameters. (a)Quantity of fuel injection (b)Injection timing (c)Rate of injection during various stages of injection (d)Injection pressure (e)Speed of nozzle opening (f)Pilot injection timing and its quantity
- 15. ELECTRONICALLY CONTROLLED INJECTION SYSTEM FOR CI ENGINES Components of Electronic Diesel Injection System •The components of electronically controlled diesel injection systems are divided into the following three main groups. (i)Electronic sensors for registering the operating conditions and changes. A wide array of physical inputs is converted into electrical signal outputs. (ii)Actuators or solenoids which convert the electrical output signal of the control unit into mechanical control movement. (iii)ECU (Electronic Control Unit) with microprocessors which process information from various sensors in accordance with programmed software and outputs required electrical signals into actuators and solenoids. •Various sensors used in electronically controlled diesel injection systems are as follows. (i)Injection pump speed sensor: It monitors pump rotational speed. (ii)Fuel rack position sensor: It monitors pump fuel rack position. (iii)Charge air pressure sensor: It measures pressure side of the turbocharger. (iv)Fuel pressure sensor: It measures fuel pressure.
- 16. IGNITION SYSTEM • This system is a part of the electrical system • where the spark necessary • There are different types of ignition systems used in petrol engines. They are as follows. 1. Battery ignition system or Coil ignition system, 2. Magneto ignition system, 3. Electronic ignition system, and 4. Transistorized ignition system.
- 17. Battery Ignition System or Coil Ignition System
- 18. Battery Ignition System or Coil Ignition System • It is employed in petrol engines Construction • It consists of a battery, ignition coil, condenser, contact breaker, distributor and spark plugs • primary winding is formed of 200-300 turns • thick wire of #20-gage • produce a resistance of about 1.5 ohms. • The secondary winding located inside the primary winding consists of 21,000 turns of thin enamelled wire of #38-40 gages • The distributor distributes the high voltage to the respective spark plugs having regular intervals in the sequence of firing order of the engine • The firing order of a 4 cylinder in-line engine is 1-3-4-2 or 1-4-3-2. Working: • The ignition switch is switched on when the engine is cranked. • engine opens and closes the contact breaker points through a cam.
- 20. Magneto Ignition System • the battery is replaced with a magneto • This system is used in two wheelers such as motorcycles, scooters etc. Construction • The armature consists of primary and secondary windings • The primary circuit consists of a primary winding, condenser and contact breaker • secondary circuit consists of secondary windings, distributor and spark plugs Working: When the contact breaker points are closed: • current flows in the primary circuit. • produces a magnetic field • primary current is at the highest peak When the contact breaker points are opened: • magnetic field in the primary winding is suddenly collapsed • high voltage (15000 V) is generated in the secondary winding • distributed to the respective spark plugs • This spark ignites the fuel-air mixture in the engine cylinder
- 21. Comparison of Magneto Ignition and Coil Ignition Systems • Simplicity: – magneto ignition system • Cost: – coil ignition system • Starting and low speed operation: – good spark is given by the coil ignition. • Strength of spark at high speeds: – With the increase in speed, the strength of spark given by the magneto ignition system increases compare to coil ignition system • Dependence on battery and charging dynamo: – magneto ignition system which is more reliable.
- 22. Electronic Ignition System • Some drawbacks in above discussed magneto ignition system. • Breaker points will wear out or burn when it is operated with heavy current • Contact breaker is only a mechanical device -cannot operate precisely • The conventional contact breaker can give satisfactory performance only at about 400 sparks per second • At low speeds, relatively high current is drawn from the battery • The system becomes inefficient at low speeds. CONSTRUCTION: • It consists of a battery, ignition switch, electronic control unit, magnetic pick-up, reluctor or armature, ignition coil, distributor and spark plugs. • . In this system, a magnetic pick-up is used instead of contact breaks points in a conventional system. • Also, a cam is replaced by a reluctor or armature.
- 24. Electronic Ignition System • Magnetic Pickup • The magnetic flux is generated by a permanent magnet. • A star shaped rotor called reluctor or armature • voltage in the coil due to the consequent changes in the flux.
- 25. Electronic Ignition System • WORKING: 1. Ignition Switch ON: The reluctor starts rotating. 2. Reluctor and Magnet Interaction: Reluctor teeth approach the permanent magnet, reducing the air gap. 3. Magnetic Field Path: The reluctor directs magnetic lines to the pickup coil. 4. Pulse Generation: As reluctor teeth pass the pickup coil, an electric pulse is generated. 5. Triggering the ECU: The pulse triggers the electronic control unit (ECU), interrupting the battery current to the ignition coil. 6. Voltage Generation: The collapsing magnetic field in the primary winding induces high voltage in the secondary winding. 7. Spark Plug Activation: High voltage is sent to the spark plug via the distributor, causing a spark. 8. Cycle Continuation: The reluctor teeth move past the pickup coil, ending the pulse, and the ECU reactivates the primary circuit for the next cycle.
- 26. Transistorized Ignition System • A transistor interrupts a relatively high current carrying circuit • a transistor is used to assist the work of a contact breaker. • Construction: • It consists of battery, ignition switch, transistor, collector, emitter, ballast resistor, contact breaker, ignition coil, distributor and spark plugs. • The emitter of the transistor is connected to the ignition coil through a ballast resistor. • A collector is connected to the battery. • Working: • The cam in the distributor is rotated by the engine. It opens and closes the contact breaker points. When the contact breaker points are closed: 1. A small current flows in the base circuit of the transistor. 2. A large current flows in the emitter or collector circuit of the transistor and the primary winding of the ignition coil due to the normal transistor action. 3. A magnetic field is set up in the primary winding of the coil.
- 27. Transistorized Ignition System • When the contact breaker points are open: 1. The current flow in the base circuit is stopped. 2. The primary current and the magnetic field in the coil collapse suddenly due to immediate reverting of the transistor to the non-conductive state. 3. It produces a high voltage in the secondary circuit. 4. This high voltage is directed to the respective spark plugs through the rotor of the distributor.
- 28. Capacitive Discharge Ignition System Working of Capacitive Discharge Ignition (CDI) System 1.Additional Components: CDI includes a power converter, capacitor, and thyristor (SCR) in the primary circuit. 2.Power Converter: Converts battery voltage to 250-300 volts to charge the capacitor with the thyristor in the OFF state. 3.Pulse Generator: Sends a signal to the thyristor to activate. 4.Thyristor Activation: •When triggered, the thyristor closes the circuit from the anode to the cathode. •The capacitor discharges rapidly through the primary winding. 5.High Voltage Output: The secondary winding generates high voltage much faster (100x faster) than inductive systems.
- 29. Capacitive Discharge Ignition System 6.Advantages: •Higher Coil Output: Produces a hotter and more precise spark (10-12 microseconds). •Reduced Spark Plug Fouling: Increases spark plug life. •Lower Current Demand: Reduces battery load and enhances battery life. •Low-Resistance Coils: Compatible with low-resistance ignition coils. •Efficient Starting: Better performance during engine start. 7.Electromagnetic Noise: Generates significant electromagnetic interference.
- 30. Distributorless Ignition System •Definition: A system without a distributor; high-voltage wires run directly from ignition coils to spark plugs. •Spark Timing Control: Managed by the Ignition Control Unit (ICU) and Engine Control Unit (ECU). •Coil Configuration: •Shared system: One coil for every two spark plugs. •Individual system: One coil for each spark plug. •Key Features: •Eliminates the distributor for higher reliability and reduced maintenance. •Uses magnetic crankshaft and/or camshaft sensors to determine position and engine speed. •Operation: •Sensors send signals to the control module. •The module energizes the appropriate coil for ignition.
- 32. SUPERCHARGING •An engine may not produce the same power output when it is operated at different locations and altitudes. •Supercharging and turbo charging are used to overcome this problem. •Supercharger is a pressure boosting device which supplies air in a diesel engine or air-fuel mixture in a petrol engine at high pressure. •Types of Supercharging Methods: •Positive displacement type: (Positive displacement blowers and compressors ) •Dynamic compressors type: (air to high speed and then exchanging its velocity for the increase in pressure by diffusing or slowing it down) • Centrifugal type supercharging •Roots type supercharging: •Screw type supercharging:
- 33. Centrifugal Type super charging Roots Type super charging Screw type supercharging
- 34. TURBO CHARGERS • Boost the pressure of air and send it to the let of the engine cylinder. • The turbocharger compresses the air and supplies it back to the engine which ensures all fuel is burned before being vented. Principle of working of a turbocharger: •A turbocharger uses engine exhaust gases to drive a turbine connected to a compressor, which compresses atmospheric air or air-fuel mixture and delivers it to the engine. •The turbine and compressor share a common shaft, enabling efficient use of exhaust energy to improve engine performance
- 35. TURBO CHARGERS Types of Turbochargers (i)Wastegate turbocharger (WGT) (ii)Variable geometry turbocharger (VGT) 1) Wastegate Turbochargers (WGT) •A Wastegate Turbocharger (WGT) uses a bypass valve to redirect excess exhaust gas, preventing damage to the turbocharger at high speeds. •The bypass valve controls the turbine's exhaust gas inflow, ensuring optimal boost pressure and preventing overload. •WGT allows the use of smaller turbines with better performance at lower exhaust flows for improved efficiency.
- 36. TURBO CHARGERS 2) Variable geometry turbocharger (VGT) •Variable Geometry Turbochargers (VGTs) adjust the turbine's aspect ratio to optimize performance at varying engine speeds, minimizing lag and improving efficiency. •Stator vanes, controlled by the vehicle's ECU, alter the nozzle angle to regulate exhaust flow, boosting low-speed performance and avoiding choking at high speeds. •VGTs maintain optimal boost pressure across engine speeds, reducing exhaust manifold pressure and pumping losses while enhancing power output.
- 37. TURBO CHARGERS Methods of Turbocharging •Turbocharging is carried out in six methods such as 1.Constant pressure turbocharging Exhaust gases from all cylinders are collected in a high-pressure manifold, where their blow-down energy is converted into useful work by the turbine, with higher pressure ratios enabling greater energy recovery. 2.Pulse turbocharging Exhaust pulse turbocharging uses separate exhaust pipes for each cylinder, allowing blow-down energy pulses to enter the turbine directly for enhanced energy recovery without interference 3.Pulse converter turbocharging Pulse converter turbocharging combines pulse and constant pressure turbocharging by using a venturi junction to connect manifold branches before the turbine for improved efficiency. 4.Two-stage turbocharging Two-stage turbocharging uses a high-pressure turbo in pulse mode and a low- pressure turbo in constant pressure mode, providing high supercharging for diesel
- 38. TURBO CHARGERS 5.Miller turbocharging The Miller system increases the expansion ratio by early inlet valve closure with higher boost pressure but is less popular due to frequent exhaust valve failures. 6.Hyper turbocharging. This turbocharging system features a diesel engine with low compression, a turbine with high-pressure ratio, and an auxiliary combustion chamber positioned between the exhaust valve and turbine.
- 40. ENGINE EMISSION CONTROL • The primary engine emissions include – carbon monoxide (CO), – hydrocarbons (HC), – and nitrogen oxides (NOx), primarily resulting from insufficient oxygen during combustion. CO and HC arise from rich air-fuel mixtures, while NOx forms from secondary reactions involving nitrogen in the combustion air. 1. Evaporative Emission Control for SI engine 2. Evaporative Emission Control System for CI Engine
- 41. ENGINE EMISSION CONTROL 1. Evaporative Emission Control for SI engine Petrol vapour from the fuel tank is captured by a carbon canister to control emissions, with vapour-liquid separators ensuring only vapour enters the canister while liquid petrol returns to the tank. During engine operation, the trapped vapour is purged from the canister and mixed with incoming air-fuel for combustion, with venting controlled by mechanical or electrical valves.
- 42. ENGINE EMISSION CONTROL 2. Evaporative Emission Control for CI engine •The fuel injection system in IC engines lacks a float bowl, necessitating an evaporative control system to manage fuel vapour from the tank. •This system features a canister with connections to the fuel tank and throttle body, utilizing an electric purge control solenoid instead of a vacuum-operated purge valve.
- 43. ENGINE EMISSION CONTROL Exhaust Gas Recirculation (EGR) System •Excessive nitrogen oxides (NOx) are reduced by the Exhaust Gas Recirculation (EGR) system, which recirculates about 10% of exhaust gas back into the intake manifold to lower peak combustion temperatures. •The EGR valve, controlled by a vacuum diaphragm, opens under throttle and includes a thermal vacuum switch to prevent recirculation until the engine reaches 38°C, ensuring minimal NOx formation during cold starts.
- 44. ENGINE EMISSION CONTROL BY CATALYTIC CONVERTER • A catalytic converter, made of stainless steel with a ceramic or metallic base coated with precious metals, converts harmful exhaust gases like hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) into harmless gases through chemical reactions without participating in the reactions themselves. • The converter features a honeycomb or ceramic bead structure to maximize surface area for gas flow, and it can be categorized as either a two-way or three-way type, with most modern vehicles utilizing the honeycomb design. Two Types: • Two-way or oxidation catalytic converter • Three-way catalytic converter
- 45. ENGINE EMISSION CONTROL BY CATALYTIC CONVERTER Two-way or oxidation catalytic converter •Two-way catalytic converters, also known as oxidation converters, effectively convert harmful carbon monoxide (CO) and hydrocarbons (HC) into harmless carbon dioxide (CO2) and water using a precious-metallic catalyst, primarily in low compression engines. •These converters are most efficient with lean air/fuel mixtures, providing sufficient oxygen for the combustion of pollutants, but they have limited effectiveness against nitrogen oxides (NOx) and particulate matter. Three-way catalytic converter •Three-way catalytic converters are designed to treat three types of emissions: carbon monoxide (CO), hydrocarbons (HC or volatile organic compounds), and nitrogen oxides (NOx), converting them into harmless carbon dioxide (CO2), water, and nitrogen (N2). •These converters feature a base structure coated with catalysts like platinum, rhodium, and palladium, maximizing catalyst surface area for exhaust flow while minimizing the
- 46. Emission Norms for Automobiles European Emission Standard (Euro) for Automobiles: •The European Union has established Euro emission standards, starting from Euro 1 and progressing to Euro 6 by 2014, classifying vehicles based on weight and engine capacity, with stricter regulations primarily for gasoline-fueled cars and similar requirements for diesel vehicles and commercial trucks. •Euro 5 standards, implemented in 2009 and 2011, further tighten emission limits for carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM) from both petrol and diesel cars to improve public health.
- 47. Emission Norms for Automobiles Bharat Stage Emission (BS) Norms for Automobiles: •Bharat Stage emission standards, established by the Government of India, regulate air pollutant emissions from internal combustion engines, with initial regulations introduced in 1989 and progressively adopting European standards for various vehicle types since 2000. •The National Auto Fuel Policy announced in 2003 aimed to implement Euro 2 to Euro 4 emission and fuel regulations by 2010, focusing on real emission reductions through test cycles that reflect normal driving conditions and considering factors like vehicular technology, fuel quality, and vehicle maintenance.
- 48. Emission Norms for Automobiles Comparison of Bharat Stage III (BS-III) and Bharat Stage IV (BS-IV) Emission Norms: 1.Introduction and Technology: BS-III norms were implemented in India in 2010, while BS-IV norms were introduced in 2017, requiring vehicles to be equipped with evaporative emission control units to significantly reduce pollution levels, although this led to increased vehicle costs due to enhanced technology. 2.Emission Limits: •Petrol Emission Norms (g/km): •BS-III: CO: 2.30, HC: 0.20, NOx: 0.15 •BS-IV: CO: 1.00, HC: 0.10, NOx: 0.08 •Diesel Emission Norms (g/km): •BS-III: CO: 0.64, HC: 0.56, NOx: 0.50 •BS-IV: CO: 0.50, HC: 0.30, NOx: 0.25
- 49. Emission Norms for Automobiles Comparison between Euro and BS emission norms: •While both Euro and Bharat Stage (BS) emission norms are based on similar standards, BS norms are tailored to meet the specific environmental and geographical conditions of India, differing primarily in testing temperatures and conditions. •For example, Euro-III is tested at sub-zero temperatures, while BS-III is tested at an average annual temperature of 24 to 28°C, and the maximum speed for testing is 90 km/hr for BS-III compared to 120 km/hr for Euro-III.