Hello guy’s In previous article we have studied that in four stroke of engine in four times travelling of piston up and down there is only one power stroke rest are ideal stroke and do not produce any power.
To reduce the number of Ideal stroke 2-stroke engine was invented in which complete operation induction compressor power and exhaust is completed in two stroke in moving the Piston Once Up and once Town or in one revolution of the crankshaft as such theoretically the two stroke engine should produce and double the Horse Power in the same size of engine then four stroke cycle engine.
●What is “2-STROKE” S.I. Engine ?
The 2-stroke engines have a thing happen with the cylinder at bottom dead center. Exhaust gas is pushed out of the cylinder by intake air, which is actively pumped into the cylinder. This is called scavenging 2-stroke engine.
●Invented of 2-STROKE Engine.
“Mr. Dugad Clark” who invented it in the year 1880. 2-stroke cycle engine is also called as “clark cycle engine”.
●Working of 2-STROKE Engine.
The previous article we have studied that all the four operation induction, compression, power and exhaust are completed in into stroke the one revolution of crankshaft.
An other words every time Piston comes down from TDC to BDC there is a power stroke now let us study how it works.
In small engines exhaust and inlet ports are made in the cylinder liner.when the Piston comes down from TDC to BDC in power stroke it opens the exhaust port which is made at a lower portion of eyeliner due to uncovering of Port by Piston the exhaust gases escape out through the port.
The Piston travels down little more is is it also and covers the inlet port which is usually made opposite to exhaust port due to an covering of inlet Port by the Piston fresh charge find its way in the cylinder the piston of the pot and working of the stroke cycle engine.
As such we had seen that when the piston is reaching BDC both the operation induction and exhaust are completed in one stroke.
Now when the Piston travels up from BDC to TDC it covers both the ports inlet and exhaust and the charge which had found its way in cylinder gets trapped and starts getting pressed the commencement of compression stroke.
when the Piston reach TDC the charge gases expand spontaneously causing on the Piston head making it moves down with force.
The Piston moves down with force from TDC to BDC after the charge is ignited it is known as power stroke.
When the piston is at the Piston skirt and covers the port in the cylinder liner from where the price charged find its way from manifold to crank case due to partial vacuum created by the crankshaft.
And its weight and when the Piston starts moving down in power stroke the charge which has come in the crankcase is press by crank weight to the inlet port side ready for being taken to the cylinder in this way the complete cycle works.
The Piston used in this type of two stroke engine are dome type up the slope in the piston is given in such a way that is deflect the incoming charges to word top and slope on other side deflects the exhaust gases to get out from the exhaust port.
In case it was a fault head Piston then the incoming charge will find its way out through exhaust port resulting in loss of power and more fuel consumption.
You have seen that mixture of petrol and air called charge in first slightly compress in the crankcase and then it finds its way to the cylinder as such it is not possible to keep lubrication oil in the sum for lubrication of crankshaft but all such parts namely crankshaft main big and gudgeon pin cylinder liner have to be lubricated otherwise the engine will seize.
To lubricated all such part certain percentage of lubricating oil which is about 4 to 5% of petrol is mix as such when the charge gets into the crankcase The lubricating oil present in the charge lubricate main big and bearing of crankshaft gudgeon pin Bush connecting rod small and Piston skirt and liner.
we have just study the working of two stroke engine where in it was explain that every time Piston travel from TDC to bdc there is power stroke or in other words it has twice the power strokes than the names size of 4 stroke engine
It mean that two stroke engine have Double the number of power stroke than the four stroke engine should produce double the horse power than 4 stroke engine of the same size but in actual practice it is not so it only produce 20 to 40% more horsepower than 4 stroke engine of same size.
●The reason for not producing double horse powers are as under:
(A) When the Piston reach bdc at the end of power stroke both the inlet and exhaust ports are open irrespective of giving slope in the Dome type of piston used in such engine certain amount of fresh charge escapes out along with exhaust gas.
(B) As the inlet port remains open for a short time as compared to four stroke engine as such due to the short time less quantity of charge can find its way in the current case.
Due to the above stated to main reason the two stroke engine does not develop double horse power than 4 stroke engine of the same size.
This type of engines being light in weight and giving more power than 4 stroke engines are mostly used for Moped, motorcycles, scooters, motor boats and many other small portable machines.
In big engines to increase its efficiency superchargers are used for filling charge in the cylinder in such cases charge is not routed through crankcase the super charger is connected directly to inteke port.
Such engines give more power than the port type of engines various in some other makes of engines instead of providing exhaust port of the cylinder wall exhaust valve are provided.
#Now we discussed about both engines:-
4- STROKE ENGINE
2- STROKE ENGINE
It gives one power Stroke in four stroke in two revolution of crankshaft since three stroke are ideal strokes.
Powerstroke takes place in every two strokes one power stroke for one revolution of crankshaft.
Due to more ideal strokes and non uniform load on the crankshaft heavier flywheel is required.
Engine has more uniform load as every time Piston comes down it has power stroke as such light flywheel is necessary.
Engine has more parts such S valves and its operating machanism engines are heavier.
Engine has no valve and their operating mechanism these are light in weight.
Engine are costlier as it has more parts fitted in it.
Engine is cheap as it has less parts.
Engine efficiency is more as charge gets completely burnt fuel consumption is less.
efficiency is lower is some parts of the charge gets escaped rooj exhaust port with this field collection is more.
Engine while working makes list sound as part of sound gets damp due to water jacket around it.
Mostly the engines are air cooled and there is no damping off sound as search engine produce more sound.
engine gives clean exhaust as charge gets completely burnt.
Due to less time available for burning of charge some of the environment charge gets escaped through which exhaust port giving smoke.
Engine requires more space.
Engine are compact in size.
lubricating oil consumption is less as the soil gets recirculated.
Lubricating oil is mixed in the fuel and gets burnt in the consumption chamber oil consumption is more.
Engine is best suitable for vehicle and stationary application as its running cost is less.
Engine is more suitable where weight consideration is a deciding factor such as Marine engine lawn mower motorcycle and two wheelers.
Aajmaesh due to more moving parts friction losses are more it’s mechanical efficiency is less.
Due to less moving parts mechanical efficiency is more.
Decarbonizing is required after long time.
Engine require decarbonizing frequently.
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