Unit ii engine auxiliary systems
- 2. • CARBURETORS: • Carburetor is a device used for atomoizing and vapourizing the fuel and mixing it with the air in varying proportions to suit for changing the operating conditions of engines. • Functions of carburetor: It prepares a mixture of petrol and air in correct proportions. It maintains a small reserve of petrol in the float chamber at constant head It atomizes and vaporizes the fuel. It supplies a fine spray of petrol It produces a homogeneous mixture It measures and supplies the proper quantity and proportions of air and fuel under all conditions of engine operation such as temperature, speed and load
- 5. SOLEX CARBURETOR TYPES OF CIRCUITS 1. Float circuit 2. Starting circuit 3. Idle and slow running circuit 4. Normal running circuit 5. Acceleration circuit
- 9. ELECTRONIC FUEL INJECTION SYSTEM FOR SI ENGINE
- 10. Limitation of carburetor • In multi cylinder engines, it becomes very difficult for simple carburetor to supply uniform quality and quantity • The induction passages are of unequal lengths • Venturi throat of the carburetor causes a restriction in the passage of air flow to the engine. • Air-fuel mixture supply becomes acute at low speed and air velocity decreases which causes less efficient atomization • There is a loss of volumetric efficiency • Carburetor has many wearing parts. After wear, it operates less efficiently
- 11. GASOLINE INJECTION SYSTEM 1. Multi-point injection system 2. Monopoint injection system
- 14. Electronically Controlled Gasoline Injection System • Fuel delivery system • Air injection system • Sensors and flow control system • Electronic control unit
- 16. • Air sensor: How much of air being draw into the intake manifold for adjusting the quantity of fuel • Intake air temp sensor:measure the temp of the intake air for fine tuning the mixture strength • Exhaust gas oxygen: located in the exhaust system provides ECU the amount of oxygen in exhaust gases. ECU determine if the air/fuel ratio is correct. • Manifold absolute pressure: It senses the vacuum pressure in the engines inlet manifold & gives an indication of the load to the engine. • Speed/crankshaft:It provided the information to ECU about engine rotating speed and the position of the crankshaft. • Engine temp: sense the temp of the coolant in the engine. • Knock sensor: is a microphone type sensor that detects the sounds of knocking so that ignition timing can be retarded.
- 17. • Advantages: • Very high quality fuel distribution is obtained • Increase the volumetric efficiency • No problem of air and fuel separation & design of manifold becomes simple. • Reduces the specific fuel consumption • It is free from blowbacks • Exhaust emission are less • Better starting • Disadvantages • Initial cost high • More completed mechanism • Increased service problem • More noise is generated • Weight and space requirement are more than conventional carburettor.
- 18. ELECTRONIC DIESEL INJECTION SYSTEM 1. Unit injector system 2. Rotary Distributor system 3. Common rail direct injection system 4. (In this injection system such as timing, rate of injection, end of injection, quantity of fuel injected etc., is difficult if the engine is operated at high speed). It may result the reduced efficiency and higher emission levels.
- 19. • Control of the parameters: • Quantity of fuel injection, Injection timing, Rate of injection during various stages of injection, Injection pressure, speed of nozzle opening, pilot injection timing and its quantity. • Components of diesel injection system: • Electronic sensors for registering operating conditions and changes. A wide array of physical inputs is converted into electrical outputs. • Acuators or solenoids which convert the control units electrical output signal into mechanical control movement. • ECU with microprocessors which process information from various sensors in accordance with programmed software and out put required electrical signals into actuators and solenoids.
- 20. • Various sensors used in diesel injection system: • Injection pump speed sensor • Fuel rack position sensor • Charge air pressure sensor • Fuel pressure sensor • Engine position sensor • Temperature sensor • Vehicle speed sensor • Brake pedal sensor • Clutch pedal sensor • Accelerator pedal sensor • Injector needle movement sensor
- 22. • Four separate phases: • 1. Filling phase • 2. Spill phase • 3. Injection phase • 4. Pressure reduction phase • Advantages: • High performance for clean and powerful engines • High engine power balanced against low consumption and low engine emissions • High degree of efficiency due to compact design. • Low noise level due to direct assemble in the engine block.
- 24. • Advantages • Simple construction • Low initial cost • Easy maintenance • Balanced cylinder fueling • Disadvantages: • Overall reduced durability • Practically suitable for small bore engines
- 25. Common rail direct injection system
- 26. • Good fuel efficiency and low CO2 emission • System injects diesel five times more accurately than the normal injection system by high response injects with electronic control. The result is higher reduction in the Nox and improving the fuel efficiency and increase the torque. • Reduce the engine noise and vibration. • High pressure fuel pump • Common fuel rail • Injectors • Engine control unit • Injection pressure does not depend on engine speed and loads. • Control of injection parameters is easy. • Pilot injection reduce the engine noise and Nox • Fuel pressure is fed to both top and bottom of the needle value. • Fuel will flow through nozzle holes.
- 27. • Advantages: • It delivers 25% more power and torque than the normal direct injection. • Initial cost is low • Superior pick up is possible • It maintain lower levels of noise and vibration • Higher mileage is obtained • Emissions are low • Fuel consumption is less • Improved performance is obtained. • Disadvantages: • Many parts involve the complicated design • Production cost is high • High degree of engine maintenance is required.
- 32. Advantages • Increase the life of contact breaker point • It gives higher ignition voltage • It gives longer duration of spark • It has very accurate control of timing • Less maintenance • Disadvantages • More mechanical points are needed similar to conventional system • It has a tendency to side tracking
- 34. Advantages • No timing adjustments are required • No distributor cap and rotor are required • There are no moving parts to wear out • Less maintenance is required • It does not require a distributor to drive thus providing less engine drag
- 35. TURBO CHARGERS
- 36. • Purpose of turbocharger: • To reduce the weight per horse power of the engine as required in aero engine • To reduce the space occupied by the engine as required in marine engines. • To have better turbulence and it ensured more complete combustion giving greater power and low specific fuel consumption • To improve the volumetric efficiency • To maintain the power of a reciprocating IC engine even at high altitudes where less oxygen is a available for combustion.
- 37. • Engine pollutants: • Carbon monoxide(CO): air fuel mixture due to lack of sufficient oxygen for the combustion of the fuel. • CO has more affinity than oxygen for hemoglobin in our blood. Affect the nervous system , finally affects heart. • Carbon dioxide (CO2): During complete combustion the hydrocarbons in the fuel are converted into carbon dioxide is 13.7% of exhaust gas. • Nitrogen oxides(NOx):All combustion processes where air containing nitrogen is burned. In high temp, nitrogen reacts with oxygen produces nitric oxide (NO) and nitrogen dioxide(NO2). Affect living organisms & blood purification system. • Hydrocarbons(HC): emissions are also the result of inadequate amount of oxygen being present to support the complete combustion of the air fuel mixture. This is produces smog, affects vision of human being.
- 38. • Smoke: produced because of insufficient mixing of fuel and air. It contains Co andCO2. When cold starting, blue white smoke is produced when more carbon particles are mixed with exhaust. Irritation of eyes, coughing, headache and vomiting. • Sulphur oxide: is produced if the fuel has sulphur. It may damage the plants. It causes irritation to eye and throat and it gives respiratory troubles to children. • Lead: It is a toxic air pollutant. It affects liver and kidneys. It causes mental effects to children.
- 39. • Pollution control: • They formation of pollutants is prevented as far as possible • The pollutants are destroyed after thery are formed. • Hydrocarbon: • Reducing the compression ratio • Changing the design of combustion chamber • Changing the design of piston • By supplying lean mixture • By maintaining of piston and piston ring. • Methods of destroying of Hydrocarbon: • By suppyling air to the inle manifold • By using after burner • By using catalytic converter
- 40. • Control of CO: • By using closed loop control • By supplying lean mixture • By providing suitable overlap of valves • Methods of destroying Co: • By using reactor in the exhaust manifold • By using after burner • By using catalyst converter • Control of oxides of nitrogen” • BY supplying the exhaust again to the inlet manifold • By spraying water in the inlet manifold to add moisture to the mixture • By using catalyst converter in the exhaust the oxides of nitrogen can be destroyed
- 41. • Control of smoke and smog: • Running the engine with a limited load • Maintaining the engine well • By adding barium salt in the fuel • By using a catalyst muffler • Methods of control: • BY using catalyst muffler • By changing the injection system in diesel engine
- 42. • Evaporative emission control for SI engine. • Petrol vapour from fuel tank escapes into atmosphere by evaporation • When the engine is not running, petrol will evaporate in the carburettor float chamber. • Is consists of a device to store fuel vapour produced in the fuel system due to evaporation • Vapour liquid separater provided at the top of a fuel tank. Vapour goes to the top of the separater where the liquid petrol is separated and it is returned to the tank. • A vent valve is provided for venteing the fuel vapour to the canister. • A canister containing activated charcoal is used to store the fuel vapour. The canister adsorbs the vapour and store it. • When engine running, the vacuum created in the intake manifold is used to draw fuel vapour from the canister into the engine. • Purging air is sucked through the canister which leads the fuel vapour from canister to the engine.
- 43. • Purging is the process by which the petrol vapour is removed from the charcoal particles inside the canister. • Electronically controlled purge valve is used. • During engine acceleration additional mixture enrichment can be tolerated and under these operating conditions the stored fuel vapour are usually purged into the intake manifold. • This system is a fully closed system. • Flow of vapour from the fuel tank may be controlled by a mechanically operated vent valve or an electrically operated solenoid valve.
- 44. EXHAUST GAS RECIRCULATION SYSTEM
- 45. • Excessive nitrogen oxides(NO2) form when the peak combustion temp exceeds 1950 C. to Lower the combustion temp, may engines have EGR system • Cooler exhaust gas absorbs heat from combustion process. • It reduces the peak combustion temp and lowers the formation of NO2. • EGR system provides a passage between exhaust manifold and inlet manifold. • EGR control valve is used to regulate flow of EGR depending upon engine operating conditions. • The intake manifold pressure and exhaust manifold back pressure may be used to control the EGR rate with vary with engine load. • It consists of a spring loaded vacuum diaphragm linked to a tapered valve. • A vacuum chamber is provided at the top of the valve. • This valve controls the passage of exhaust gas • The chamber is connected by tube to a vacuum port in the throttle body.
- 46. • When there is no vacuum at this port, the spring pushed the diaphragm down and keeps the passage closed. • No exhaust gas recirculated. It happens during idle when NO2 formation is at a minimum. • When the throttle is opened from the idle position, vacuum applied will gradually open throttle valve. • It causes the exhaust gas to flow into the intake manifold. Open throttle, the intake manifold vacuum is low and EGR valve is closed by the spring. • EGR valve system do not affect full power operation. • The exhaust gas is recirculated only in this system when the engine operating conditions are supposed to form NO2.
- 48. • EMISSION NORMS (EURO AND BS): • Reduction in emission: • Vehicular technology • Fuel quality • Inspection & maintenance of in use vehicles • Road and traffic management