Mr. Education

Problems Caused by Engine Emissions: Internal combustion engine generates undesirable emissions which can cause serious problems: Global Warming  Acid Rain Smog Odors Respiratory Problems  Health Problems Classification of Engine Emissions: Engine emissions are further classified into two types: 1. Exhaust Emissions: These emissions will result after the combustion of fuel. These emissions include: Unburnt Hydrocarbon (HC) Oxides of Carbon (Carbon Monoxide & Carbon Dioxide) Oxides of Nitrogen(NO & Nitrogen Dioxide) Oxides of Sulphur(SO & Sulphur Dioxide) Particulates  Soot and Smoke 2. Non-Exhaust Emissions: These emissions result before the combustion of fuel. These emissions include: Fuel Tank   ↣  The fuel tank emits fuel vapor into the atmosphere. Carburetor   ↣  It also gives fuel vapor. Crankcase   ↣  It emits blow-by gases and fuel vapor into the atmosphere. Causes of E...

Necessity Of Engine Cooling: If there is no engine cooling system in a car, it might reaches higher temperature which can important components burn gasket, delivery lines. If no engine cooling system, lubrication oil can change its composition. High temperature attainment can reduce the strength of piston, cylinder lining, etc. Engine cooling is required to keep the temperature low to increase volumetric efficiency, reduce engine failure. Demerits Of Over-Cooling: Disadvantages of over-cooling are: Starting of engine becomes difficult. Reduction in engine life. Inadequate lubrication of engine. Improper vaporization of fuel. Demerits Of Under-Cooling: Disadvantages of under-cooling are: Reduction in life of piston and cylinders due to the attainment of high temperature. Under cooled engine lead to pre-ignition of fuel in SI engines. Composition of lube oil may change. Effects of Operating Variables on Engine Heat Transfer: Compression Ratio ...

Lubrication: It is defined as the admittance of oil between two surfaces having relative motion. Why do we need Lubrication? The functions of lubrication are described ahead: Reduce friction between moving parts. Reduce wear and tear of parts. Shock absorbing. To cool the surfaces in contact. Properties of Lubricants: Following are the properties of Lubricants: Viscosity   ➸  Internal resistance to flow of liquid. It is the ability of oil to resists internal deformation due to load and mechanical stresses. Viscosity Index   ➸  It represents the change in viscosity of oil with temperature. The greater the viscosity index, the smaller the change in viscosity with temperature. Flash Point Temperature   ➸  The lowest temperature at which vapor of lubricating oil will ignite when given an ignition source. Fire Point Temperature   ➸   It is the minimum temperature at which vapor of fluid will keep burning after the i...

Combustion: The ignition of fuel in the presence of air producing carbon dioxide, water and heat energy. The topics like Calorific value, Net Calorific Value and Gross Calorific Value is defined by Calorific Value . Homogeneous Mixture: It is the mixture of two components such that you have the same proportion of components in each sample. It is used in SI engines. Combustion starts at the end of compression stroke. When A/F mixture is ignited, flame front appear and starts to spread. Propagation of flame is due to heat transfer and diffusion. Velocity with which the flame front moves is called Normal Flame Velocity. If equivalence ratio is in between 1-1.2, the flame velocity is maximum. If heat due to combustion zone becomes equal to the heat due to adjacent zone then flame gets extinguished. Heterogeneous Mixture: It is the mixture of two components such that you have the different proportion of components in each sample. It is used in CI engines. ...

Mechanical Injection System: Used to inject fuel into the combustion chamber. Fuel speed > air speed at delivery point to atomize fuel. Amount of fuel delivered into the air stream going into the engine is controlled by pump which forces the fuel under pressure. A device used to initiate and control the combustion process is called Mechanical Injection System. Functional Requirements of Injection System: Metering of Fuel:   Used to control fuel to meet speed and load requirements of the engine. Injection Timing:  Have proper injection timing to obtain max. power, fuel economy and proper burning. It is done by  Camshaft or Push rod (Rocker Arm) Mechanism . Proper Control of Injection Rate:  To get desired heat release pattern during combustion. Proper Atomization of Fuel:  Proper making of droplets to make best Air/Fuel mixture. Proper Spray Pattern:  Distribution of droplets to ensure rapid mixing of fuel & air. Uniform Distribut...

Carburetion: The process by which combustible fuel-air mixture is made by mixing the proper amount of fuel is called Carburetion. The device which does this job is called Carburetor. Air speed > fuel speed at fuel nozzle to atomize fuel. Amount of fuel drawn into the engine depends upon the air velocity in the venturi. Factors Affecting Carburetion: 1. Engine Speed: The greater the speed of engine, the lesser the time for carburetion. 2. Vaporization Characteristic of Fuel: If distillation temperature is lower, the vapor content is higher which results in good vaporization characteristics which make carburetion better. 3. Air Inlet Temperature: If incoming air has high temperature then the volatility increases which result in good carburetion. 4. Design: The intake system & Combustion chamber design has a significant impact on carburetion. Air-Fuel Mixture & Their Requirements: There are three types of air-fuel mixture which are as follo...