4 stroke engine working principle
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The document discusses four-stroke and two-stroke engines. It provides animations and explanations of the operating cycles of both engine types, including the individual strokes in each cycle. It also compares the two engine types, noting advantages and disadvantages of each, such as two-stroke engines being lighter and simpler but less fuel efficient and longer lasting than four-stroke engines. Application examples are given for both spark ignition and compression ignition engine types.
4 stroke engine working principle
- 1. EME-505 I.C.ENGINES AND COMPRESSORS UNIT-1 Engine Cycle Animation Prepared by: V.K.Yadav GLBITM 20-May-21
- 3. 4-stroke Cycle SI Engine Principle of Operation • Cycle of operation is completed in 4- strokes of the piston or 2 revolutions of the crankshaft. • Each stroke consists of 180°, of crankshaft rotation and hence a cycle consists of 720°of crankshaft rotation. 20-May-21
- 4. Contd.. 4-stroke SI Engine Principle of Operation • The series of operations of an ideal four- stroke SI engine are as follows 1-Suction Stroke 2-Compression Stroke 3-Expansion or Power Stroke 4-Exhaust Stroke 20-May-21
- 6. injector injector injector injector injector 20-May-21
- 7. Suction Compression Ign.-Combn. Expansion Exhaust 4-stroke Cycle SI Engine Principle of Operation 20-May-21
- 8. Contd.. Principle of Operation Stroke Valve Position Suction Stroke Suction Valve open Exhaust Valve closed Compression Stroke Both Valves closed Expansion or Power Stroke Both Valves closed Exhaust Stroke Exhaust Valve open Suction Valve closed 20-May-21
- 10. Two-stroke Cycle Engine principle of Operation • 2 & 4 stroke – Difference! - method of filling cylinder with fresh charge & removing burned gases from cylinder. • 2 stroke engine suction is accomplished by air/charge compressed in crankcase/by blower. • No piston strokes required for suction/exhaust operations. • 2 piston strokes required to complete cycle, compression and expansion or power stroke. • No separate intake and exhaust 20-May-21
- 11. Two Stroke Spark Ignition Engine • Stroke 1: Fuel-air mixture is introduced into the cylinder and • is then compressed, combustion initiated at the end of the stroke • Stroke 2: Combustion products expand doing work and then exhausted • Power delivered to the crankshaft on every revolution 20-May-21
- 12. 2-stroke engine Compression and power stroke 20-May-21
- 13. ARE YOU READY TO COMPARE NOW??? 20-May-21
- 14. 20-May-21
- 15. TWO STROKE ENGINES Two-stroke engines do not have valves, which simplifies their construction and lowers their weight. Two-stroke engines fire once every revolution, while four-stroke engines fire once every other revolution. This gives two-stroke engines a significant power boost. 20-May-21
- 16. TWO STROKE ENGINES + points These advantages make two-stroke engines lighter, simpler and less expensive to manufacture. Two-stroke engines also have the potential to pack about twice the power into the same space because there are twice as many power strokes per revolution. The combination of light weight and twice the power gives two-stroke engines a great power-to-weight ratio compared to many four-stroke engine designs. 20-May-21
- 17. TWO STROKE ENGINES + points Two-stroke engines can work in any orientation, which can be important in inverted flights or aerobatic flights. A standard four-stroke engine may have problems with oil flow unless it is upright, and solving this problem can add complexity to the engine. 20-May-21
- 18. TWO STROKE ENGINES - points Two-stroke engines don't last nearly as long as four-stroke engines. The lack of a dedicated lubrication system means that the parts of a two-stroke engine wear a lot faster. Two-stroke oil is expensive, and you need about. You would burn about a gallon(3.785 ltrs) of oil every 1,000 miles if you used a two-stroke engine in a car. 20-May-21
- 19. TWO STROKE ENGINES - points Two-stroke engines do not use fuel efficiently, so you would get fewer miles(1.6 km) per gallon(3.785 ltrs). Two-stroke engines produce a lot of pollution -- so much, in fact, that it is likely that you won't see them around too much longer. 20-May-21
- 24. FOUR STROKE ENGINES conventional Otto engines 20-May-21
- 25. FOUR STROKE ENGINE OPERATION 20-May-21
- 26. Comparison between two stroke and four stroke engines
- 27. FOUR stroke Engine CHARACTERISTICS (compared with 2 stroke engines) FOUR STROKE ENGINES LASTS LONGER THAN TWO STROKE ENGINES. The lack of a dedicated lubrication system means that the parts of a two-stroke engine wear a lot faster. FOUR STROKE ENGINES DON’T BURN OIL IN COMBUSTION CHAMBER. Two- stroke oil is expensive, and you need about 113.36 grams of it per gallon of gas. You would burn about a gallon of oil every 1,000 miles if you used a two-stroke engine in a car. FOUR STROKE ENGINES ARE MORE FUEL EFFICIENT. Two-stroke engines do not use fuel efficiently, so you would get fewer miles per gallon. FOUR STROKE ENGINES ARE CLEANER. Two-stroke engines produce a lot of pollution INVERTED FLIGHTS MAY NOT BE EASY IN FOUR STROKE ENGINES. Two- stroke engines can work in any orientation, which can be important in acrobatic flights. A standard four-stroke engine may have problems with oil flow unless it is upright, and solving this problem can add complexity to the engine. 20-May-21
- 28. Advantages of Two-stroke Engines Advantages (over 4-stroke Engines) • Power developed nearly twice compared • Work required to overcome the friction of the exhaust and suction strokes is saved. • More uniform turning moment - lighter flywheel • Engines lighter & occupy less space • Construction is simple - reduces maintenance problems • Because of scavenging, burnt gases do not remain in the clearance space as in case of four-stroke engines. 20-May-21
- 29. Disadvantages of Two-stroke Engines Disadvantages (over 4-stroke Engines) • High speed - less efficient - reduced volumetric η • Short circuiting increases fuel consumption & reduces the thermal η • Effective compression is less • Liable to cause a heavier consumption of lubricating oil. • With heavy loads, engines get heated due to excessive heat produced. Also at light loads, running of engine is not very smooth because of the increased dilution of charge. 20-May-21
- 30. Scavenging process in 2 stroke Engines • Scavenging?? • The replacement of the products of combustion in the cylinder from the previous power stroke with fresh-air charge to be burned in the next cycle . 20-May-21
- 31. Theoretical Scavenging Processes • The actual scavenging process is neither one of perfect scavenging nor perfect mixing. It probably consists partially of perfect scavenging, mixing and short-circuiting. • The first phase of the scavenging process is a perfect scavenging process which then gradually changes into a complete mixing process 20-May-21
- 32. Types of 2 Stroke Engines- Based on scavenging techniques 1-Based on scavenging (sweeping out of burnt gases by fresh charge)method i)Crankcase & ii) Separately scavenged engine 2-Based on scavenging process (air flow) i)Cross flow scavenging, ii)Loop scavenging (MAN, Schnuerle, Curtis type) iii)Uni-flow scavenging (opposed piston, poppet valve, sleeve valve) 3-Based on overall port-timing i) Symmetrical & ii) Unsymmetrical scavenging 20-May-21
- 34. Separately Scavenged Engine Loop-scavenged 2-stroke Engine 20-May-21
- 35. Classification Based On Scavenging Process Cross Loop Uniflow 20-May-21
- 36. Classification Based On Scavenging Process… Uni-flow Scavenging by Poppet Valve 20-May-21
- 38. Comparison of Two-stroke CI And SI Engines • 2-stroke SI engine suffers from -fuel loss & idling difficulty. -fuel loss & hence low indicated thermal efficiency - (SI) More Dilution, Short Circuit, Back Firing at low speeds, less air available for combustion after scavenging -Fuel injection (CI) improves idling, avoids loss of fuel and also eliminates backfiring as there is no fuel present in the inlet system. 20-May-21
- 39. SI Engine Advantages The SI engine offers the following advantages • Low initial cost. • Low weight for a given power output. • Smaller size for a given power output. • Easy starting. • Less noise. • Less objectionable exhaust gas odor and less smoke. 20-May-21
- 40. SI engine application • Uses of Two stroke (SI)petrol engines finds extensive use in motor cycles, scooters, mopeds, pleasure motor boats, etc., because of simplicity and low cost. • Moped (50cc) with 1.5 KW at 5000 rpm • Scooter (100cc) with 3.5 KW at 5000 rpm • Scooter(150cc) with 5 KW at 5300 rpm • Motor cycle (250cc) with 9 KW at 4500 rpm • Uses of Four stroke petrol engines finds extensive use in motor cycles, cars, jeeps,buses, trucks, pumping sets, mobile electric generating sets because of simplicity and low cost. • Fiat car (1089cc) 4-cylinder with 32 KW at 5000 rpm • American car 6 cylinder with 185 KW at 5000 rpm • Jeeps(4000cc) 6 cylinder with 90 KW at 20-May-21
- 41. CI engine application • Uses of Two stroke (CI) Diesel engines finds extensive use in ship propulsion • Ships with 20,000 KW at 120 rpm • 400-900 mm bore • Uses of Four stroke diesel engines(Most versatile and thermally efficient) • 100-4500 rpm and 1 to 35000 KW • Tractors- 30 KW • Jeep, buses, trucks – 40 to 100 KW • Diesel engines- more than 100 KW • Earth movers – supercharged with 200 to 400 KW • Locomotives – 600 to 4000 KW • Marine – 100 to 35000 KW • Main draw back – Vibration and unpleasant smell from smoke 20-May-21
- 42. CI Engine Advantages The CI engine offers the following advantages. • Low specific fuel consumption at both full load and part load conditions. • Utilizes less expensive fuels. • Reduced fire hazard • Long operating life. • Better suited for supercharging. • Better suited for two-stroke cycle operating, as there is no loss of fuel in scavenging. 20-May-21
- 43. Bajaj Pulsar Specifications www.mypulsar.com • Bajaj pulsar 200 NS Bajaj pulsar 150 • Type : SOHC-4V-Liquid cooled 4 stroke DTSI • Cost in delhi Rs. 85000 • Bore: 72 mm • Stroke: 49 mm • Displacement: 199.5 cc 149 cc • Max power: 23.52 PS@9500 15.06 PS@9000 • Max torque: 18.3 NM @8000 12.5 Nm @6500 • Fuel system: Carburettor • 6 gears • Combustion system: Triple spark 4 valves engines 27 % faster than twin spark and 50% faster than single spark • Bajaj Discover 125 ST • Cost Rs. 54200 • 125 cc • 4 valves • 65 Km/hr
- 47. The 4-Stroke Engine • Stroke Breakdown: (18) – Intake: – Compression: – Power: – Exhaust:
- 52. Four Stroke Cycle Animation • Four Stroke Spark Ignition Engine
- 55. 4-Stroke Engine • Valve Operation During a Cycle: (4) • Briggs & Stratton 3hp Engine: (3) • Firing Order: (4) (exercise) • 4-Stroke Characteristics: (12)
- 57. The 2-Stroke Cycle Engine: • Introduction: (3) • Strokes: (2) • No Valve Mechanisms: (3)
- 58. 2-Stroke Engine • Stroke Breakdown: (11) – Power: – Compression: • Differences Between The 2 & 4 Stroke: (3) • Advantages of the 2-Stroke: (8) • Disadvantages of the 2-Stroke: (6)