 Hello students, myself, Siddhasher B. Thurzapure, Associate Professor, Department of Mechanical Engineering, Valchain Institute of Technology, Solapur. So, today we are going to deal with the topic, it is Introduction to Flywheel, the Learning Outcome. At the end of this session, students will be able to explain the role of flywheel. The contents are, firstly the definition of flywheel, then parts of flywheel, then the turning movement diagram which is associated with the flywheel, then variation of crank speed due to the variation in torque, then examples of flywheel application, then we will shift to the difference between flywheel and governor, and then material of flywheel, lastly the references which we have used for this session. Let us see the definition of the flywheel. A flywheel is a heavy wheel which serves as a reservoir, storing energy during the period when the supply of energy is more than the requirement and releases it during the period when the requirement of energy is more than the supply. By the definition itself, you can observe that we are we are in the requirement of a reservoir and the reservoir is required because we are going to have the variation in the supply and the demand. The demand if it is more then and if supply is lesser, we should have one more source it is, then if the demand is lesser and supply is more, we should have the storage of that one. So, flywheel serves as a reservoir, storing the energy whenever the excess it is in available and then it is releasing it whenever we are in need of that one. The different parts of the flywheel we will observe. Flywheel basically it is a wheel which is heavier and next to that one as it is a wheel it is circular then you can observe the different say parts of it firstly at the center of the wheel we are going to have the hole. So this hole it is needed because the flywheel it is to be fitted on the crankshaft and then surrounding this hole we are going to have this part which is called as hub and then the outermost part of the wheel flywheel you can observe so it is called as rim. Then the hub and the rim these are connected to each other with the help of the arms or these are also called as spokes. So now in this case four arms are there so at the center it is hub and hub is having a hole and on the outer side it is the rim so you can observe the same here. So here it is the crankshaft on which the flywheel it has been fitted and then here the number of arms these are more. So here it is four and here it is five and then the outer rim portion you can observe. Then the turning movement diagram it is associated with the flywheel. So the turning movement diagram we have seen in detail in the first session. So here again just we will have the revision of that one. So in case of the say internal combustion engines or in case of the reciprocating steam engines etc we are not having the constant output torque with reference to the crank angle. That is crankshaft it is rotating about its own axis and the angular motion it is taking place. If we are representing it in terms of the theta here and the turning moment it is represented on the y axis the blue color line it is showing you that the torque it is continuously varying. So in case of these due to the power stroke say the energy will be available and during the other strokes like suction, compression and exhaust etc the power will be consumed. So because of which we are going to have the variation in the torque. So the torque is not continuously produced by these types of the engines. So as the power stroke it is taking place in case of this one the speed of the crankshaft or the crank it is going to increase. So we are going to have corresponding to this one the angular motion will be there. So the angular speed or the angular velocity it will be say omega max it is given. So because it will be higher and then next to that one when the energy or instead of say being produced by these types of the engines during the other strokes like say suction, compression and then the exhaust etc. So if the energy is consumed in those cases we are going to have the reduction in the speed and say the speed is reduced and it is going to have some other value which is shown as omega minimum. So as the time passes so you can see that the x axis it is representing the time and on the y axis we are having the speed of rotation. So in case of this one we are going to have the continuous variation in the speed in every cycle. So you can have one cycle from here to here and then again the continuous repetition it is occurring and number of cycles are there here. And in one cycle only you can consider from here to here also. So in case of this there is variation in the speed. So increase and decrease in the speed it is going to occur and the highest value of the omega we are going to have that is called as omega max and lowest value it is omega minimum. So like this the crank speed it is continuously varying due to the variation in the torque which is due to the intermittent power strokes and not the continuous power strokes. Now think of whether a flywheel is needed in case of a punching operation in a punching press which is driven by an electric motor. See in case of electric motor there is no power stroke and say suction stroke etc. So here electrical energy it is converted into the mechanical energy. But in case of this one also we are in the requirement of a flywheel. See the flywheel it is needed basically in two cases. One when the load is constant and torque it is varying the torque which is available it is varying but the load is constant like say in case of the vehicles if suppose the vehicle is carrying a constant load from one place to another place the load it is going to be constant and the torque which is provided by the engine of that vehicle it is varying continuously in a cycle. So in case of that one say like say IC engines etc. Or you can think of also reciprocating steam engines etc. So in those machines which are say using these types of the engines we are going to have the use of flywheel. And then secondly we are going to have the say one more type where like say the machine is there which is now punching press and in case of this one the electric motor has been used which is going to provide you the constant torque throughout the cycle. But when the ram it is coming from the top side to the bottom up to touching that sheet metal. So till then it will have very less load and then during the punching operation it will have very high load and then again the while the ram is moving vertically upwards to the original position the again the load it is load it is very less. Like that in case of the punching press what is happening is the torque is constant which is provided by the electric motor but the load it is varying. So either of these two that is either the load is varying or the torque which is used it is varying. So out of these two if anyone is varying we are in need of the flywheel to reduce the fluctuation in the speed. Examples of the flywheel applications the flywheel applications you can observe that say in case of the sewing machine also say during the stitching only the say power required it will be more. So in sewing machine we are going to have this wheel say which is going to act as a flywheel. Then in case of the punching machine just now we have discussed the flywheel is there. Then next to that one in case of the two wheelers also we are in need of the flywheel two wheelers because they are using internal combustion engines. Now let us see the difference between the flywheel and the governor. Governor also we are knowing flywheel reduces the fluctuation of the speed of the crankshaft during every revolution that is this fluctuation is mainly due to the non availability of the power stroke continuously. So power stroke availability is intermittent and during the other strokes like suction compression exhaust etcetera the energy will be utilized and due to that one we are going to have the variation in the speed. So this variation that is omega max and omega minimum we have just seen so if this difference between omega max and omega minimum if it is to be reduced then we have to make use of the flywheel. So flywheel basically reduces the fluctuation of speed even though we are making use of the flywheel there will be fluctuation but that will be lesser when as compared to when we are not using it. On the other hand the governor these are say keeping the speed of the crankshaft as constant. So in case of the say the turbines etcetera which are coupled to the electrical generators so in case of that one we are in need of the constant speed of the say generator shaft because the electricity produced will be depend the frequency of that one it is dependent upon the shaft speed. So if the generator shaft it is rotating at different speeds the frequency with which the electricity is generated will vary. So there we require the speed of the generator shaft as constant one so there we are going to have the governor to control the speed of the turbine shaft which ultimately leads to the control of the speed of the generator shaft. Now in case of the materials of the flywheel we are in need of the energy storage so heavy materials are to be used hub and the spokes or the arms these are contributing very less. So the lighter materials can be used for this and the rim that is outer part it is contributing very large say up to 90 percent etcetera. So because of which the high density material can be used hub and the spokes these are leading to 10 to 15 percent of the contribution for the energy storage. So even though the flywheel it is to be heavier the for efficient flywheel the rim it is to be made for half high density material and hub and the spokes these should be made up of lighter material. So these are the references which have been used for this session. Thank you.