History
Nikolaus August Otto as a young man was a traveling salesman for a grocery concern. In his travels he encountered the internal combustion engine built in Paris by Belgian expatriate Jean Joseph Etienne Lenoir. In 1860 Lenoir succeeded in creating a double acting engine which ran on illuminating gas at 4% efficiency. The 18 liter Lenoir Engine was able to produce only 2 horsepower. The Lenoir engine ran on the illuminating gas that was made from coal which had been developed in Paris by Philip Lebon.
In testing a replica of the Lenoir engine in 1861 Otto became aware of the effects of compression on the fuel charge. In 1862 Otto attempted to produce an engine to improve on the poor efficiency and reliability of the Lenoir engine. He tried to create an engine which would compress the fuel mixture prior to ignition, but failed as that engine would run no more than a few minutes prior to its destruction. Many engineers were also trying to solve the problem with no success.In 1864 Otto and Eugen Langen founded the first internal combustion engine production company NA Otto and Cie (NA Otto and Company). Otto and Cie succeeded in creating a successful atmospheric engine that same year.
The four cycles refer to intake, compression, combustion (power), and exhaust cycles that occur during two crankshaft rotations per power cycle of the four-cycle engines. The cycle begins at Top Dead Centre (TDC), when the piston is farthest away from the axis of the crankshaft. A cycle refers to the full travel of the piston from Top Dead Centre (TDC) to Bottom Dead Centre (BDC).(For better understanding refer to our vedio)
Graph showing relation between pressure and voloume(OTTO CYCLE)
PROCESS 1-2 Adiabatic compression
PROCESS 2-3 Constant volume compression or fuel injection
POINT 3 cutoff point
PROCESS 3-4 Adiabatic expansion
PROCESS 4-1 constant volume expansion
THE GREEN LINE INDICATE ENTERING OF FUEL
THE PURPLE LINE INDICATE EXAUST OF FUEL
The graph given below shows the TEMPERATURE VS ENTROPY relation
(NOW REFER VIDEO)
video of one cylinder 4-Stroke Engine
NOW SEE FOR 4 CYLINDER ENGINE BELOW
4 cylinder engine works
INTAKE stroke:
on the intake or induction stroke of the piston, the piston descends from the top of the cylinder to the bottom of the cylinder, reducing the pressure inside the cylinder. A mixture of fuel and air, or just air in a diesel engine, is forced by atmospheric (or greater) pressure into the cylinder through the intake port. The intake valve(s) then close. The volume of air/fuel mixture that is drawn into the cylinder, relative to the volume of the cylinder is called, the volumetric efficiency of the engine.
COMPRESSION stroke:
with both intake and exhaust valves closed, the piston returns to the top of the cylinder compressing the air, or fuel-air mixture into the combustion chamber of the cylinder head.
POWER stroke:
this is the start of the second revolution of the engine. While the piston is close to Top Dead Center, the compressed air–fuel mixture in a gasoline engine is ignited, usually by a spark plug, or fuel is injected into the diesel engine, which ignites due to the heat generated in the air during the compression stroke. The resulting massive pressure from the combustion of the compressed fuel-air mixture forces the piston back down toward bottom dead centre.
EXHAUST stroke:
during the exhaust stroke, the piston once again returns to top dead center while the exhaust valve is open. This action evacuates the burnt products of combustion from the cylinder by expelling the spent fuel-air mixture out through the exhaust valve(s).
Power output limitations
The maximum amount of power generated by an engine is determined by the maximum amount of air ingested. The amount of power generated by a piston engine is related to its size (cylinder volume), in four-stroke design, volumetric efficiency, losses, air-to-fuel ratio, the calorific value of the fuel, oxygen content of the air and speed (RPM). The speed is ultimately limited by material strength and lubrication. Valves, pistons and connecting rods suffer severe acceleration forces. At high engine speed, physical breakage and piston ring flutter can occur, resulting in power loss or even engine destruction. Piston ring flutter occurs when the rings oscillate vertically within the piston grooves they reside in. Ring flutter compromises the seal between the ring and the cylinder wall which results in a loss of cylinder pressure and power. If an engine spins too quickly, valve springs cannot act quickly enough to close the valves. This is commonly referred to as 'valve float', and it can result in piston to valve contact, severely damaging the engine. At high speeds the lubrication of piston cylinder wall interface tends to break down. This limits the piston speed for industrial engines to about 10 m/s.
Rod and piston-to-stroke ratio
The rod-to-stroke ratio is the ratio of the length of the connecting rod to the length of the piston stroke. A longer rod will reduce the sidewise pressure of the piston on the cylinder wall and the stress forces, hence increasing engine life. It also increases the cost and engine height and weight.
A "square engine" is an engine with a bore diameter equal to its stroke length. An engine where the bore diameter is larger than its stroke length is an oversquare engine, conversely, an engine with a bore diameter that is smaller than its stroke length is an undersquare engine.
Valvetrain
The valves are typically operated by a camshaft rotating at half the speed of the crankshaft. It has a series of cams along its length, each designed to open a valve during the appropriate part of an intake or exhaust stroke. A tappet between valve and cam is a contact surface on which the cam slides to open the valve. Many engines use one or more camshafts “above” a row (or each row) of cylinders, as in the illustration, in which each cam directly actuates a valve through a flat tappet. In other engine designs the camshaft is in the crankcase, in which case each cam contacts a push rod, which contacts a rocker arm which opens a valve. The overhead cam design typically allows higher engine speeds because it provides the most direct path between cam and valve.
Valve clearance
Valve clearance refers to the small gap between a valve lifter and a valve stem that ensures that the valve completely closes. On engines with mechanical valve adjustment excessive clearance will cause noise from the valve train. Typically the clearance has to be readjusted each 20,000 miles (32,000 km) with a feeler gauge.
Most modern production engines use hydraulic lifters to automatically compensate for valve train component wear. Dirty engine oil may cause lifter failure.
Energy balance
Otto engines are about 30% efficient; in other words, 30% of the energy generated by combustion is converted into useful rotational energy at the output shaft of the engine, while the remainder being losses due to friction, engine accessories, and waste heat. There are a number of ways to recover some of the energy lost to waste heat. The use of a Turbocharger in Diesel engines is very effective by boosting incoming air pressure and in effect provides the same increase in performance as having more displacement. The Mack Truck company decades ago developed a turbine system which converted waste heat into kinetic energy which was fed back into the engine's transmission. In 2005, BMW announced the development of the turbosteamer, a two stage heat recovery system similar to the Mack system that recovers 80% of the energy in the exhaust gas and raised the efficiency of the Otto engines it is applied to by 15%.
HERE IS GIVEN FIRING SEQUENCE IN PETROL ENGINE
No. of cylinder
|
Firing sequence (as per cylinder)
|
2 cylinder
|
1 cylinder,2 cylinder
|
3 cylinder
|
1 cylinder,3 cylinder,2 cylinder
|
4 cylinder
|
1 cylinder, 3 cylinder, 4 cylinder, 2cylinder OR 1 cylinder, 2cylinder,4 cylinder,3 cylinder
|
6 cylinder
|
1 cylinder,5 cylinder,3 cylinder,6 cylinder,2 cylinder,4 cylinder OR 1 cylinder, 4 cylinder, 2 cylinder,6 cylinder ,3 cylinder,5 cylinder
|
8 cylinder
|
1 cylinder,6 cylinder,2 cylinder,5 cylinder,8 cylinder,3 cylinder,7 cylinder,4 cylinder OR 1 cylinder,8 cylinder,7 cylinder,3 cylinder,6 cylinder,5 cylinder,4 cylinder,2 cylinder
|
Categories:
automobile,
engines,
mechanical
video helps to understand very well !!! good sir !!
hi,
this is nice post. I want to know that is there any other application of otto cycle except petrol engine.
The most important requirement for debt settlement in California is a california debt settlement license . This license is issued by the Department of Business Oversight, and it is required for any person or company offering debt settlement services in the state.