 Well friends, today we shall be discussing IC engine series fuels supply systems in CI engines and in that we shall be discussing on the topic fuel injectors. Let me introduce myself first. I am Dr. Prakash Sauronke, working as associate professor in department of mechanical engine. At the end of this session students will be able to describe working of different types of fuel injectors, fuel injector. In IC engine, in CI engine, in a type of IC engine, compression ignition fuel is injected at the end of compression stroke at high pressure through a component which is known as fuel injector. There are mainly three types of fuel injectors. One is blast injector, mechanically operated injector, automatic injector. So blast injector as used in air injection system where air blast will help the fuel to go inside. Atomical engines are mainly fitted with automatic injectors. So because it is not possible to use mechanically operated injectors there, so automatic injector. Now, atomical fuel injectors which are automatic, fuel injectors atomizes that fuel into very fine droplets. Now you tell me why we need to atomize the fuel. Why to atomize? We have seen atomize means breaking into very fine light, fine droplets. But why we need atomization increases the surface area of the fuel droplets. Because very fine droplets are there so it will increase the surface area resulting in better mixing and subsequent combustion, better mixing with air. Better mixing with air and then subsequent combustion so that is necessary. Atomization is done by forcing the fuel through a small orifice under high pressure, small orifice, small hole and under high pressure. The injector assembly that you need consists of different parts, a nozzle valve, a compression spring and an injector body. A cross sectional view of a typical Bosch fuel injector is shown in figure. We shall be seeing the figure. The fuel supplied by the injection pump exerts the force against the spring to lift the nozzle valve. So we shall see the figure and then we will again come here for discussion. So this is how that fuel injector is constructed. So this is nozzle body. This is nozzle valve. So this is the valve. This is the fuel. So that is coming and this nozzle valve is opening here. So there is a hole here but it is right now closed. So this is normally closed type. So fuel will be coming here so that will go here and it will lift this particular nozzle valve. Now this is nozzle cap. Then this is spindle. This is spindle. So this is the fuel supply passage. So this is the leak off. This is the spring and here there is a lock nut. Here there is adjustable screw and here there is a cap. So these are the different parts. Now let us see the working. The fuel supply coming from the pump at high pressure will come here and enter here below this portion of the nozzle. So when say pressure is here so this will lift the nozzle valve against the spring force. Normally the spring will pressurize here through this spindle and this will be normally closed. But when the pressure is higher fuel pressure so this will lift and this will open the passage and then fuel will be injected inside the combustion chamber or inside the engine cylinder. Now the fuel supplied by the injection pump exerts force against the spring to lift the nozzle valve that we have seen just now. Fuel is spread into the combustion chamber in a finely atomized particles because of high pressure and very small opening so that hole which is drilled with very small depth. When fuel from the delivery pump is exhausted the spring pressure pushes the nozzle valve back on its seat. So when the fuel is exhausted the pressure will drop down and when the fuel pressure drops down the spring will push the nozzle valve back to its seat and it will again close the opening. The spring tension and hence the valve opening pressure is controlled by the adjusting screw provided at the top. So we have seen at the top there is a screw if we want to see the figure again so here yes. So this is the adjustable screw and nut okay. So which help us to control the opening pressure as well as spring tension. For lubrication between nozzle valve and its guide some quantity of fuel is allowed to leak through the clearance between them. So there will be slight clearance between the nozzle valve and its guide so that some amount of fuel is leaked so that will I mean cause the lubrication and that will be throwing back to the I mean fuel supply system. So here we have seen that Lycop so Lycop is provided here through which the fuel will return. So this fuel is then drained back to fuel tank through Lycop connection. Nozzle is that part of the injector through which the liquid fuel is spread inside the combustion chamber. The nozzle should perform the following functions so what are the functions expected from the nozzle so that we shall discuss. One is atomization it is required for obtaining proper mixing of the fuel and air in the combustion chamber that we have studied earlier also. Then distribution of fuel so that is one more important function. Distribution of fuel to the different areas within the combustion chamber so that is one more I mean important function so that is expected of the nozzle. Then factors affecting these two are injection pressure. Higher the injection pressure better is the dispersion and penetration of the fuel into the different location in combustion chamber that is natural. So penetration means depth up to which the fuel will be penetrated. Then another factor which affects is density of air in the cylinder. If the density of compressed air in the combustion chamber is high then the resistance to the movement of the droplets is higher and dispersion is better. So resistance to the movement so that will be higher so that will cause the better dispersion. Then apart from that physical properties of the fuel the properties like self-ignition temperature, vapor pressure, viscosity, etc play important role in the distribution. If self-ignition temperature is low vaporization will be earlier vapor pressure will be more. Viscosity is small then distribution will be better. I mean more then distribution will be lesser so all these are the other properties. Apart from that there is one more requirement of the semi nozzle. So that is prevention of the fuel I mean impingement on the walls. There is possibility that fuel may impinge directly on the walls of the combustion chamber or piston. So instead of going in the combustion chamber it will go directly to the walls or I mean combustion chamber as well as the piston top. So this fuel striking the walls decomposes and produces carbon deposits. So since it will be directly going on the walls it will not come I mean combined with the oxygen or air so it will not burn and that will decompose due to high temperature and produce carbon deposits. So it causes smoky exhaust as well as increase in fuel consumption. So smoky exhaust is there because so that that carbon deposits they will enter say the products of combustion and say that will cause incomplete combustion and it will also increase the fuel consumption that is unutilized fuel. So this is say one more drawback another function say that is known as mixing. Mixing the fuel and air especially in case of non-turbulant type of combustion chamber should be ensured by nozzle. So there are normally turbulent type of combustion chamber and non-turbulant so we shall be discussing them later. So in turbulent chambers the turbulence helps for I mean better mixing however in case of non-turbulant since there is no turbulence or movement of the air so mixing function is again the important aspect or important requirement of the semi nozzle. Again discussion from this we are taken from the book of Mathur and Sharma Dhanpatrai Publications. Similarly internal combustion engine book by V. Ganesan's McGraw Hill Publication of India. I thank to them and I also thank you for patient listening.