 Well friends, I'm Dr. Prakash Soundke, working as Associate Professor in Department of Mechanical Engineering in Valsion Institute of Technology, Solapur. Today we shall be continuing our discussion on IC engine series and today's topic is fuel supply system in CI engines in that types of nozzles. At the end of this session, students will be able to describe working of different types of fuel nozzles used in CI engines compression ignition engines. Fuel nozzles in CI engines. Nozzle is that part of an injector through which the liquid fuel is spread into the combustion chamber. The nozzle should fulfill the following functions. We have discussed it earlier also. Atomization of fuel droplets. Distribution of fuel in different areas of combustion chambers. Prevention of impingement of fuel droplets on the walls of the cylinder. So these are and better mixing of fuel with air. The design of nozzle should be able to perform these required functions. The design of nozzle is closely related to the type of combustion chamber used. So that we shall be discussing later combustion chambers. The nozzles widely used in atobiles are normally closed type. Various types of nozzles used in CI engine are as follows. Single hole nozzle, multi hole nozzle, Pinter nozzle and Pintox nozzle. So let us start our discussion with single hole nozzle. At the center of the nozzle body there is a single hole drilled which is closed by the nozzle wall as shown in the figure. So we shall be seeing the figure. First we shall see the figure so that yes. So this is the body. This is the nozzle. This is the nozzle. Here there is a hole. Here there is a hole and this is the tapered portion conical taper to this nozzle. The fuel will be supplied through this passage and it will go in this annular area, annular area and then say here of course above this so we have seen in the fuel injector there will be spindle and spring that will be forcing the nozzle to close this particular hole. Now right now it is slightly lifted like lifted so fuel when introduced in this annular area will lift the semi nozzle against the spring force and then this hole will be opened okay. So this is how this construction is there. The size of the hole is usually of the order of 0.2 mm okay 200 microns. Spray cone angle is around 15 degree. Spray cone angle means through which say the angle which is covered by that cone. Major disadvantage is that at the start of upward movement of the needle wall lesser flow passage area is available than the orifice. So because it is a conical taper is there so all area will not be opened so only small area will be open initially available for injection and this causes the pressure drop. So because change in pressure I mean area so that will cause pressure drop. Hence in the beginning there is weak injection and at the end there is tendency of dribbling okay because of low pressure weak injection and at the end of the stroke again area will be smaller so leakage or dribbling. Secondly one more drawback is that the spray angle 15 degrees too narrow to facilitate good mixing. Hence higher velocities of the air are required okay. So that is there because there will not be proper distribution with I mean narrow spray angle. We have seen the distribution. So instead of single hole multi-hole nozzles are preferred it consists of a number of holes in the tip of the nozzle as shown in the figure. The holes vary in number from 4 to 18 and the size varies from 35 to 200 microns. The angle angle is from 20 degree upwards so we shall let us try to understand so this with the help of figure. Now here the nozzle body nozzle so this is the fuel passage so this is as usual so this is the main hole and these are the other holes. Now here only one hole is seen in this cross-sectional area there can be number of holes we have seen say they may refer from 3 to 18 5 to 18 and the diameter vary from 35 to 200 microns okay. Now this angle between the main vertical and say this is more than 20 degree 20 degree and more. So it can be maximum say that 90 degree to this on all around the periphery so that holes will be there. These nozzles operate at a very high injection pressures of around 18 megapascal or 180 to 200 bar. Now why we need higher pressures? Who can tell why we need such higher pressures? In single hole it is 100 bar in multiple 5 yes because the hole size is smaller so that is 1 35 to 200 microns and secondly there are number of holes and say through all the holes the fuel must be distributed. The advantage of this particular I mean nozzle is that ability to distribute the fuel properly even with lower air motion available in open combustion chambers. Since there are number of sprays number of sprays number of holes through which the fuel will be going inside and that again at different angles say naturally the mixing is very I mean proper and distribution is also uniform throughout the combustion chamber. So in open combustion chamber so that is a type of combustion chamber when there is no turbulence so there also you know that fuel is properly distributed. So the construction we already seen. Now one more type here is the third type that we shall be discussing is Pintel nozzle. In this type of type the stem of the nozzle wall is extended to form a spindle or Pintel which protrudes through the mouth of the nozzle body as shown in the figure. So we shall see the figure. Stem of the nozzle end of the nozzle wall is extended to form a spindle instead of conical shape. So there is a spindle we shall see the figure first so you will understand yes. So here the end is say the stem so that is in the form of cylindrical stem or spindle spindle okay. So it differs from the single hole nozzle so there is a taper it is not there. Rest of the arrangement is similar. Now let us try to understand what is the advantage of this. The size and shape of the Pintel is varied according to requirement size as well as shape so that is I mean varied. It provides a spray operating at low injection pressure so that is one advantage over the multi hole nozzle okay similar to single hole nozzle. The spray obtained is hollow conical and cone angle is generally 60 degree. Since there is a stem in the center say the spray will be hollow it will not be solid and the angle cone angle is varying that is 60 degree so that is more at the start when the wall is wall lifts the Pintel partially blocks the orifice and prohibits high pressure drop. So that is the advantage over the conical end of the single hole nozzle. So since there is stem it even if it is lifted so it will be partially it will be blocking the orifice and so that will prohibit the high pressure drop when the nozzle will be further lifted then so this avoids weak injection and dribbling it prevents the carbon deposits on the nozzle hole. So that we have seen say that injection and dribbling so that will cause the carbon deposits. As the wall lift increases the orifice is fully uncovered as the wall is further lifted so that is hole will be fully uncovered and complete area is available. So Pintel nozzle produces good atomization but reduces the penetration. Penetration is reduced because there is hollow I mean cone at the center there is that stem so because of which the penetration is less but cone angle is better and it is hollow so because of which there is good atomization. Normally used in pre combustion and high swirl chambers then one more type is Pintox nozzle it is development of Pintel nozzle which has an auxiliary hole drilled in the nozzle body as shown in the figure. So we shall see the figure so there is one more hole. A small amount of fuel is injected through its additional hole air in the upstream direction slightly before the main injection this is called as pilot injection. So this will be clear when we shall see the figure. The needle wall does not lift fully at low speeds hence the more most of the fuel is injected through the auxiliary wall. Main advantage of this nozzle is better cold starting performance 20 to 25 degrees lower than multi-hole design Here this is the auxiliary hole the shape is Pintel only but through this auxiliary hole there will be pilot same in injection so that will enhance the cold starting. A major drawback of this nozzle is that injection characteristics are not or poorer than the multi-hole nozzle not equal to multi-hole. So there is also possibility of auxiliary hole to choke hence needs better filtration. References for these are taken by Icingis Mathur Sharma Dhanpat Republigation and Icingis Bookbag Veganation Magro Hill of India. I thank to them and I thank you also