ABSTRACT  Single cylinder diesel engines in present use are noisy and have no vibration. The problems of obtaining satisfactory engine performance consist of chiefly in adjusting conditions so as to keep down to certain limits the final pressure and the rate of rise of combustion pressure inside the combustion chamber. Crankshafts of these engines are normally connected to through a rigid link with the fly wheel. The pressure rise in steps in the piston cylinder assembly during the power stroke, since it has to overcome the inertia of flywheel. This is the prime reason for noisiness, Vibration and formation of NOx. This is achieved by introducing a rubber spring loaded flywheel in place of a rigid link that is presently used. In this project design of a rubber spring loaded flywheel is carried out and the modified engines performance is studied. It is understood that there is a drastic reduction in noisiness and vibration.          A

CAUSES OF VIBRATION,NOISE AND NOx

In I.C engines there are three type of forces which may cause vibration in I.C engines, they are: Inertia of reciprocating partsCentrifugal forces due to unbalance in the rotating parts andTorsional vibration.  The vibration due to reciprocating masses and the unbalance rotatory masses can be minimized by balancing and by means of counter weights.

TORSIONAL VIBRATIONS During down stroke of the piston a heavy force is imposed on the

crankpin. This force tends to twist the crankshaft. At the end of this stroke, the force is relieved and the twisted crankshaft returns beyond the original position, so the twisting in two directions sets up torsional vibration in the crankshaft.

Torsional vibrations are of a great hazard for the following reasons,It may result in dangerously high stress in the shaftIt affects other parts, especially gears, bushes, etc.

These torsional vibrations depend on the parameters of vibrating material of the system like mass, rigidity and ability to absorb vibrational energy.

The force which produces torsional vibration in I.C, engine shaft comes from the variable gas pressure on the piston, the forces of inertia and the impact force on the piston. As the forces of inertia cannot be reduced, the reduction of peak pressure and the impact forces is carried out.

This can be achieved by substituting a flexible link place of the existing rigid link between the crankshaft and the flywheel which offers a greater resistance for piston travel.

In case of a flexible link, this pressure is partially transmitted as a resilient energy of the spring and thus reduces the load on the flywheel (i.e. fluctuations of speed in the flywheel will be minimal in this case of than that of the previous case). Since speed fluctuations are directly propotional to the mass of flywheel, lesser mass of flywheel can be used. There by reducing the overall weight of the engine. This gives a better pickup and better starting of the engine thus reducing the fuel consumption.

SOUND FORMATION AND CHARACTERISTICS

During suction and compression stroke the sound

produced by the engine is less.

During combustion stroke maximum noise is produced

At exhaust stroke sound level is slightly less than that of the combustion.

NOx

Oxides of nitrogen which also occur only in the engine exhaust are a combination of nitric oxide (NO) and nitrogen di-oxide (NO2). Nitrogen and oxygen react at relatively high temperatures. Therefore high temperatures and availability of oxygen are the two main reasons for the formation of NOx .

When the proper amount of oxygen is available, the higher the peak combustion temperature the more is the NO formed. Since the peak pressure is reduced in the modified setup, the peak temperature also gets reduced. Thus the formation of NOx is reduced.

DESIGN OF FLYWHEEL

Flywheel is designed to store the energy during the power stroke and supply during the other strokes.

•The flywheel will not run at constant speed.

•During power stroke expansion will takes place inside the cylinder against the inertia of the flywheel.

•So the flywheel is divided into two parts

1.Primary flywheel

2.Secondary flywheel

•Primary flywheel is designed to rotate the engine without combustion (i.e. suction, compression, exhaust).

•Secondary flywheel is used to store energy produced during combustion (i.e. power output of the engine).

•Now energy from the primary flywheel to the secondary flywheel is transferred through a rubber spring.

•During power stroke excess energy supplied, is transmitted through a rubber spring to the secondary flywheel which is connected to a load rotating at constant speed.

•It is known that during power stroke the primary flywheel connected to the engine rotates at higher rpm than mean rpm.

•During that time energy is stored in this rubber spring and gradually delivered to the secondary flywheel when the energy level falls.

•Thus the speed of the secondary flywheel is maintained constant irrespective of the primary flywheel.

Fig. shows the sectional view of the flywheel setup

Outer diameter of the primary flywheel=23.5 cmThickness = 2.2 cmWidththickness = 3.7 cmShaft diameter = 3.1 cmHUBInner diameter = 3.1cmOuter diameter = 6.1cm

SPECIFICATIONS OF FLYWHEEL

Fig. shows the three dimensional view of the flywheel setup

Fig. Shows the three dimensional view of flywheel setup

Fig. Shows the detailed view of flywheel setup

EXTENSIONS OF CRANK SHAFT

•For the purpose of extension the crank shaft key is removed and the keyway is welded.•The taper end of the crank shaft is turned to its minor diameter up to the oil seal •The surface finish is improved by grinding•A shaft is turned and threaded at the end so as to match the internal thread in the crank shaft.•The shaft is fastened to the crank shaft and the space between them is welded.•To ensure the alignment the extended shaft is turned •A hole is drilled across the shaft to make provisions for attachments.

MODIFICATION OF PULLEYS

•The procured double belt pulley is drilled and bored to the extended shaft diameter with some clearance•The rear side of the pulley is machined to form a boss that matches with the projection in the flywheel•The flywheel and pulley faces were cleared to have a good surface contact•The flywheel and pulley were fixed such that the boss holds the projection•Four holes were drilled on flywheel pulleys assembly•The hole in the flywheel were taped to hold the bolt•The hole in the pulley is enlarged and the end is countersunk to seat the CSK bolt head•To seat the pulley within the cooling fins one of the belt groove is machined•A hole is drilled to hold the web of the torsion spring and the corresponding hole in the flywheel is taped•The induction motor pulley is drilled so as to hold the motor shaft•The motor shaft is fixed with the pulley through a lock nut

CRANKSHAFT ATTACHMENTS

•A step turned attachment is made and it is drilled so as to ensure a clearance fit over the extended shaft•A drill hole is made across to match with the hole in the extended shaft•A slit is made across the shaft to enhance the grip•One end of the drilled hole in the attachment is tapped so that when the attachment is fastened a good hold is provided •One end of the spring which has to be attachment is traced•A series of drill holes were made all through the traced path so that the end of the spring has no movement in the slot.

RESULTS

From the design, it is inferred that the following may be obtained•The sound level is may reduce on the average•It could be felt, there may an appreciable decrease in the vibration level•From the decrease in sound level it may be conclude that reduction in peak pressure may attained•Decrease in noise level•Decrease in vibration level •More gradual reduction of pressure in the combustion chamber•Reduction of peak pressure