2-stroke cycle gasoline engine

Engine construction and design, and principles of operation

1. TWO-STROKE CYCLE GASOLINE ENGINE Engine Construction, Design and Principle of Operation Laboratory Exercise No. 3

2. Diaz, Loieji Lahom , Leslie Joy Llena , Joemar Vela, Ma. Lourdes Maureen Andres, Christian

3. INTRODUCTION Two-stroke cycle engine The gasoline two stroke engine, and the cylinder ports on which it depends, were invented by Joseph Day in 1889. These cylinder ports were subsequently incorporated into diesel two-stroke engines, replacing either just the inlet valves or both inlet and exhaust valves.

4. INTRODUCTION Two-stroke cycle engine performs the same cycle of events as the four-cycle engine intake, compression, power, and exhaust functions take place during only two strokes of the piston ― up & down takes only one revolution of the shaft to complete a two-stroke cycle

5. INTRODUCTION

6. INTRODUCTION

7. OBJECTIVES To discuss the principle of operation of a two-stroke cycle gasoline engine. To enumerate the principal engine parts and functions of a two-stroke cycle engine.

8. PROCEDURE Enumeration of the basic parts of a typical two cycle gasoline engine. Discussion of the function of each part. With the aid of illustration, step by step principle of operation of a two cycle gasoline engine is discussed. the advantages and disadvantages of a two-cycle gasoline engine are enumerated.

9. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine

10. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Cylinder block ─ an  integrated structure comprising the  cylinder  of a reciprocating engine and often some or all of their associated surrounding structures

11. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Piston ─ component of reciprocating engines. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings

12. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Crankshaft ─  mechanical part able to perform a conversion between reciprocating motion  and rotational motion

13. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Connecting rod ─ connects the piston  to the  crank or  crankshaft

14. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Flywheel ─ This is usually made of cast iron and its primary function is to maintain uniform engine speed by carrying the crankshaft through the intervals when it is not receiving power from a piston.

15. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Sparkplug ─ device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark

16. RESULTS & DISCUSSION

17. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Inlet port ─ supplie s the  fuel/air mixture to the  cylinder ─ primary function of the intake manifold is to  evenly   distribute the combustion mixture

18. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Transfer port ─ the simplest of the designs and the most common in small two-stroke engines

19. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Exhaust port ─ the opening, in the cylinder or valve, by which the exhaust steam escapes.

20. RESULTS & DISCUSSION I. Basic parts of a typical two-stroke cycle gasoline engine Deflector ─ where the gas flow within the cylinder must be carefully directed in order to provide efficient scavenging

21. RESULTS & DISCUSSION II. Principle of a two cycle gasoline engine

22. RESULTS & DISCUSSION II. Principle of a two cycle gasoline engine As the piston travels down, the mixture previously drawn into the crankcase is partially compressed. As the piston nears the bottom of the stroke, it uncovers the exhaust and intake ports. The exhaust flows out, reducing the pressure in the cylinder. When the pressure in the combustion chamber is lower than the pressure in the crankcase through the port openings to the combustion chamber, the incoming mixture is deflected upward by a baffle on the piston.

23. RESULTS & DISCUSSION II. Principle of a two cycle gasoline engine As the piston moves up, it compresses the mixture above and draws into the crankcase below a new air-fuel mixture.

24. RESULTS & DISCUSSION II. Advantages of two-stroke Cycle Over Four-stroke Cycle Engines 1) The two-stroke cycle engine gives one working stroke for each revolution of the crankshaft. Hence theoretically the power developed for the same engine speed and cylinder volume is twice that of the four-stroke cycle engine, which gives only one working stroke for every two revolutions of the crankshaft. However, in practice, because of poor scavenging, only 50-60% extra power is developed.

25. RESULTS & DISCUSSION II. Advantages of two-stroke Cycle Over Four-stroke Cycle Engines 2) Due to one working stroke for each revolution of the crankshaft, the turning moment on the crankshaft is more uniform. Therefore, a two-stroke engine requires a lighter flywheel. 3 ) The two-stroke engine is simpler in construction. The design of its ports is much simpler and their maintenance easier than that of the valve mechanism.

26. RESULTS & DISCUSSION II. Advantages of two-stroke Cycle Over Four-stroke Cycle Engines 4) The power required to overcome frictional resistance of the suction and exhaust strokes is saved, resulting in some economy of fuel. 5 ) Owing to the absence of the cam, camshaft, rockers, etc. of the valve mechanism, the mechanical efficiency is higher. 6 ) The two-stroke engine gives fewer oscillations.

27. RESULTS & DISCUSSION II. Advantages of two-stroke Cycle Over Four-stroke Cycle Engines 7) For the same power, a two-stroke engine is more compact and requires less space than a four-stroke cycle engine. This makes it more suitable for use in small machines and motorcycles. 8 ) A two-stroke engine is lighter in weight for the same power and speed especially when the crankcase compression is used.

28. RESULTS & DISCUSSION II. Advantages of two-stroke Cycle Over Four-stroke Cycle Engines 9) Due to its simpler design, it requires fewer spare parts. 10) A two-stroke cycle engine can be easily reversed if it is of the valve less type.

29. RESULTS & DISCUSSION II. Disadvantages of two-stroke Cycle Over Four-stroke Cycle Engines 1. The scavenging being not very efficient in a two-stroke engine, the dilution of the charges takes place which results in poor thermal efficiency.

30. RESULTS & DISCUSSION II. Disadvantages of two-stroke Cycle Over Four-stroke Cycle Engines 2. The two-stroke spark ignition engines do not have a separate lubrication system and normally, lubricating oil is mixed with the fuel. This is not as effective as the lubrication of a four-stroke engine. Therefore, the parts of the two-stroke engine are subjected to greater wear and tear.

31. RESULTS & DISCUSSION II. Disadvantages of two-stroke Cycle Over Four-stroke Cycle Engines 3. In a spark ignition two-stroke engine, some of the fuel passes directly to the exhaust. Hence, the fuel consumption per horsepower is comparatively higher. 4 . With heavy loads a two-stroke engine gets heated up due to the excessive heat produced. At the same time the running of the engine is riot very smooth at light loads.

32. RESULTS & DISCUSSION II. Disadvantages of two-stroke Cycle Over Four-stroke Cycle Engines 5. It consumes more lubricating oil because of the greater amount of heat generated.

33. RESULTS & DISCUSSION II. Disadvantages of two-stroke Cycle Over Four-stroke Cycle Engines 6. Since the ports remain open during the upward stroke, the actual compression starts only after both the inlet and exhaust ports have been closed. Hence, the compression ratio of this engine is lower than that of a four-stroke engine of the same dimensions. As the efficiency of an engine is directly proportional to its compression ratio, the efficiency of a two-stroke cycle engine is lower than that of a four-stroke cycle engine of the same size.

34. CONCLUSION ‰ T he basic parts of a two stroke cycle gasoline engine are: piston, cylinder block, crankshaft, piston rod, flywheel, sparkplug, inlet port, exhaust port, transfer port and deflector . Each downward stroke of the piston is a power stroke and each upward stroke of the piston is a compression stroke.

35. CONCLUSION ‰ The intake and exhaust cycle may be considered a part of the power and compression stroke and begins after completion of the power stroke as the exhaust valves open. The intake and exhaust cycle ends after the piston closes off the intake ports of the cylinder liner on the compression stroke.

36. SUPPLEMENTAL QUESTIONS 1. What is more powerful, two-stroke or four-stroke cycle engine? Why? Two-stroke cycle engine is more powerful than four-stroke cycle engine. It is capable of producing quick and sudden bursts of power that are not sustained for a long period of time. It produces high power for a relatively short period while four-stroke cycle engine produces low power for a long period of time.

37. SUPPLEMENTAL QUESTIONS 1. What is more powerful, two-stroke or four-stroke cycle engine? Why? In 2 stroke engine, every alternate stroke is power stroke, unlike in a 4 stroke engine in which power gets delivered only once in every 4 strokes. This gives a significant power boost. Also, the acceleration will be higher & power delivery will be uniform due to same reason.

38. SUPPLEMENTAL QUESTIONS 2. Explain why two-stroke cycle engines produces more smoke compared to four-stroke cycle engine. 2-stroke cycle engines are not efficient in burning fuel. The burning of lubricating oil that is being mixed and the exhaust of un-burnt fuel makes them a lot more polluting than 4-stroke engines of same power. The combustion of oil added in the mixture creates a lot of smoke which leads to air pollution.

39. SUPPLEMENTAL QUESTIONS 3. What are the distinguishing features of a two-stroke cycle gasoline engine? • 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.

40. SUPPLEMENTAL QUESTIONS 3. What are the distinguishing features of a two-stroke cycle gasoline engine? • Two-stroke engines can work in any orientation, which can be important in something like a chainsaw. 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.

41. SUPPLEMENTAL QUESTIONS 4. What is the reason why oil is being mixed to the fuel of a two-stroke cycle engine? Oil is being mixed to the fuel of a two-stroke cycle engine because the crankcase is part of the intake process, it cannot act as an oil sump as is found on four-cycle engines. In 2-stroke, lubricating oil is mixed with fuel so it burns as fuel burns and consumed more, while in 4-stroke, lubricating oil is contained in the crankcase.

42. SUPPLEMENTAL QUESTIONS 4. What is the reason why oil is being mixed to the fuel of a two-stroke cycle engine? Two-stroke engines employ a total-loss lubrication system that combines oil and fuel to provide both energy and engine lubrication. The oil and fuel are combined in the cylinder’s intake tract and lubricate critical components such as the crankshaft, connecting rods and cylinder walls.

43. SUPPLEMENTAL QUESTIONS 4. What is the reason why oil is being mixed to the fuel of a two-stroke cycle engine? In general, two-stroke engines are known to wear more quickly than four-stroke engines because they don’t have a dedicated lubricant source; however, high-quality two-stroke oil significantly reduces engine wear.

44. SUPPLEMENTAL QUESTIONS 5. What specific job applications do two-cycle gasoline engine find itself most suitable? Two-strok engines are ideal in applications such as chainsaws, weed trimmers, outbourd motors, off-road motorcycles and racing applications. Two-stroke engines are also easier to start in cold temperatures, making them ideal for use in snowmobiles.

45. REFERENCES Print-outs Internal Combustion Engine Fundamentals. John B. Heywood. McGraw-Hill, Inc. USA. 1988 Basic of Engine Operations. The Goodheart Willcox Co., Inc AENGR411lecture handout. Emmnuel Sicat.2016 Online http://www.slideshare.net/amanina_mal/agriculture-engineeringchptr15 http://en.wikipedia.org/wiki / Others Microsoft Student 2008 Encarta Encyclopedia