 Well, friends, I'm Dr. Prakash Sarunke, working as associate professor in Department of Mechanical Engine, Walshian Institute of Technology, Sulapur. Today, we shall be discussing on the topic of fuel systems in CI engine compression ignition engines, the first part in our IC engine series. At the end of this session, students will be able to describe working of solid injection fuel supply systems for CI engine and the types of it. The fuel injection systems are classified as air injection system. In this system, fuel is forced into the cylinder or combustion chamber by means of compressed air. The second type is solid injection system. What do you understand about the word solid injection? Can anybody tell? Can guess? Yes. Actually, in this system, the liquid fuel is injected directly into the combustion chamber or cylinder without the help of compressed air. The correct name should have been liquid injection, but say this solid injection was going on from the beginning, so it is called solid injection only. Now, solid injection systems are most widely used in practice. It is also called airless mechanical injection system, so that is another name, airless. Normally solid injection system consists of following elements, fuel tank, fuel feed pump, injection pump to meter and pressurize the fuel for injection. First fuel feed pump is transferring the fuel from tank to the injector pump. We shall see the details working. Then governor, injector and fuel filters. So, let us see the layout so that we will understand. So, this is the solid injection system. Now, here there is a fuel tank from which say first the fuel will be going say with the help of that transfer pump and here there is a filter, coarse filter, okay. So this filter is so it requires filtration naturally, so there should not be any particles that should go inside the cylinder. Here there is a plunger feed pump. So this is low pressure pump, low pressure pump from which the fuel will be going to here that is a pressure relief valve, pressure relief valve. So pressure relief valve is I mean is for safety of the total system. So if by chance the pressure exceeds the I mean set value then say it will release and the fuel will be sent back here, otherwise the fuel will be going to the fine filter. So here there is a fine filter and from fine filter it will be supplied here to fuel pump. So this is a high pressure pump and high pressure pump will now increase the pressure further and it will supply it to the injector. And from injector say that fuel will be I mean injected inside the combustion chamber or inside the injector cylinder. So some of the here quantity is metered, so remaining quantity and some leakage quantity, so that will be going here say through I mean passage and it will go to this pressure relief valve. Instead of returning it to the system, so it will pass again say through the fine filter and will be going to the cement fuel pump, okay. So this is how a normal solid injection system works. Now what are the different types of solid injection system? Air fuel is injection systems mainly consist of all the fuel injection system mainly consist of two basic elements, one is pump for pressurizing and another is injector for atomizing. So these are two main elements. The different types of solid injection system differ in the manner of operation and control of these elements. The way operation and control of these elements is done based on that say the different solid I mean injection systems are classified. They are classified mainly into four types, one is individual pump and nozzle system, then unit injector, common rail system, distributor system. So these are the main four types, so we shall be discussing them in detail one by one in our subsequent discussion. First individual pump and injector system. As the name implies in this system there is separate metering and compression pump, so which is called as individual pump used for each cylinder. So for each cylinder is a separate. It is also called a jerk pump system because a jerk is experienced. Say for each pump say it is I mean pressurizing to high pressure the fuel. Figure shows the schematic diagram so we shall be going to the figure. Separate pump and separate injector as seen normally reciprocating type of fuel pump is used. So let us first see figure and then we shall return again. You can see here, here there are two cylinders and two pumps separately for each cylinder. The fuel from fuel tank will be coming through this low pressure pump or it is also called as feed pump and it is supplied to high pressure pump. And this HP line now this pump will supply to this cylinder, here the injector is again separate. So individual pump and individual injector. Similarly another I mean cylinder it will be separate pump and separate cylinder okay. So once we understand this normally these pumps are reciprocating to a fuel pump too so that higher pressure can be achieved. In around 20 degrees of crankshaft rotation 65 to 300 pressure bar pressure is developed. So within so small so it is in milliseconds actually 20 degrees of crankshaft so that comes in time I mean time duration as say I mean few milliseconds. So in few milliseconds such high pressure has to be developed. So it requires robust and heavy valve gears for accurate timing length of pressure lines must be identical for each of the cylinder say that must be identical. The quantity and timing both are controlled at the pump itself okay. So that is that the quantity and timing at the pump itself. Now this is a figure so where say separated pumps means these two pumps are separate from each other. There is one more design so where individual pump and nozzle both are mounted in the cluster. All the other working is similar only the mounting is same for both the pumps okay. So that is that's why it is called as pumps in cluster okay. So this is individual pump and injector system. Now there is one more system so that we shall be discussing today so that is known as unit injector system. In the unit injector system the pump and the injector nozzle both are combined in one housing. In individual pump we have seen pump is separate and injector is separate. In unit injector say these both units are combined. Each cylinder is provided with separate unit injector so in it is similar to that individual so individual injector. So it is called as unit injector. Fuel is supplied to the injector by a low pressure pump feed pump from the fuel tank pressure rod and rocker arm actuate the plunger and thus injects the fuel into the cylinder at proper time. So we shall see the arrangement in the figure. The quantity of fuel injected is regulated by the effective stroke of the plunger. So effective stroke of plunger can be varied with the helical groove so that we shall be studying later in detail. Figure shows the schematic so let us see the figure so that it will be more clear. So this is the low pressure pump and it will supply the fuel to here. So here that pressure I mean pump and injector both are combined together so it is called as unit injector only one. Similar to this cylinder another and these are the rocker arm and pressure rod so this mechanism. So camshaft is there which will be operating this particular rod and with the help of rocker arm so this will at a proper time say press or activate the pump and injector. So that at proper time the fuel will be injected inside the engine cylinder. Similarly for each cylinder say there will be separate arrangement so that it can be injected I mean timing for different cylinders can be controlled say differently. Okay so this is how unit injector system works. Now references for this particular discussion were taken from the books of IC engine ML Mathur and RP Sharma from Dhanpat Rai Publications and internal combustion engines book by Veganation, McGraw Hill Education India. I thank to them and I also thank you for the patient listening.