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- 2. Aleksey Terentyev Contact Information: Izhevsk State Technical University, 7 Studencheskaya street, Building 2, Room 415 426069,
- 3. The carburetor The carburetor is a device used to mix proper amounts of air and fuel
- 4. When this vapor enters the combustion chamber of the engine and is compressed by the action
- 5. When the fuel and air are combined within the engine’s combustion chamber, a chemical balance is
- 6. The ratio of air to fuel in a theoretically perfect stoichiometric mixture is approximately 15:1; that
- 7. Table lists the proper amounts of air and fuel, with regard to different engine running conditions
- 8. Gasoline is a liquid. Oxygen, on the other hand, is a gas and has the ability
- 9. Principle of Atomization Atomization is the process of combining air and liquid, in this case fuel,
- 10. Figure 1 This illustration shows how atomization takes place in an engine. Atomization is the process
- 11. The Venturi Principle Carburetor design is based on the Venturi principle. The Venturi principle simply states
- 12. Figure 2 The Venturi principle. A venturi has a particular shape—a modified hourglass figure, you might
- 13. Figure 3 The effect of low pressure in a venturi. The major air passage in the
- 14. As mentioned earlier, as air speed increases, air pressure decreases. The speed of air as it
- 15. The fuel is atomized under the influence of atmospheric pressure as it’s mixed with the incoming
- 16. A large engine that creates a high vacuum uses a carburetor with a large venturi. A
- 17. FUEL DELIVERY SYSTEMS The various components of the fuel delivery system of most gasoline-powered engines will
- 18. In many cases, the fuel tank uses a gravity feed system to allow fuel to flow
- 19. Fuel Valves Fuel valves, also known as fuel petcocks, are on/off valves that control the flow
- 20. Figure 5 Fuel valves are designed to open and close the flow of fuel to the
- 21. Fuel Lines Fuel lines are used to flow gasoline from the fuel valve to the carburetion
- 22. Fuel Pumps Some power equipment engines use a fuel pump. The purpose of a fuel pump
- 23. Mechanical Fuel Pumps The mechanical fuel pump is a pump that uses a diaphragm operated by
- 24. As the cam rotates, the rocker arm moves up and down. The lever is connected to
- 25. Vacuum Fuel Pumps The vacuum fuel pump (Figure 7), also called an impulse fuel pump, uses
- 26. Electric fuel pump The electric fuel pump is operated electronically by the use of an electric
- 27. CARBURETOR TYPES AND OPERATION The carburetor has the task of combining the air and fuel into
- 28. Cold Start Systems For the cold start phase of engine operation, a rich fuel mixture is
- 29. Primer Cold Start System A primer cold start system is a rubber squeeze bulb used to
- 30. There are two different types of the primer cold start system in power equipment engines: wet
- 31. Choke Plate Cold Start System The choke plate cold start system is an air restriction system
- 32. This plate has a small hole cut into it, a cut out in the plate, or
- 33. Choke Plate Operation The choke plate can be operated manually or by an automatic choke, as
- 34. When the engine is started, low pressure is created in the cylinder during the intake stroke.
- 35. When the engine is cold, the bimetal spring contracts. The end of the spring moves the
- 36. Types of Carburetors There are many types of carburetor designs, but as you’ve learned, the fundamental
- 37. 1. Vacuum Carburetors The vacuum carburetor, also called the suction carburetor, is a common carburetor often
- 38. Figure 14 The vacuum type carburetor uses a simple, one-piece housing. A vacuum carburetor has a
- 39. There is a throttle valve inside the carburetor just past the air entrance. Below the throttle
- 40. A low pressure (vacuum) is created inside the carburetor as the piston moves down on the
- 41. There are two circuits in the carburetor housing: low speed and high speed (Figure 17). Fuel
- 42. 2. Float Carburetors Many power equipment engines use a float carburetor (Figure 18), which is a
- 43. The fuel line from the fuel tank provides fuel to the carburetor. The fuel line is
- 44. The float bowl is a component that provides a storage area for fuel in the carburetor.
- 45. As the engine runs, fuel in the float bowl is used up. The fuel level in
- 46. Float Carburetor Types All float carburetors use a float to control the fuel level. There are,
- 47. An updraft carburetor (Figure 21) is a carburetor in which the air flows into the venturi
- 48. A downdraft carburetor (Figure 22) is a carburetor in which the air flows into the venturi
- 49. A sidedraft carburetor (Figure 23) is a carburetor in which the air flows into the venturi
- 50. Float Carburetor Operation Most float carburetors operate in the same fashion. The operation of the carburetor
- 51. The float system operates at all times and at all engine speeds (Figure 24). It provides
- 52. As the bowl fills, the float rises, raising the inlet needle valve toward the inlet seat
- 53. When the engine is idling, the throttle valve is in the closed (or nearly closed) position.
- 54. Here it mixes with air from the idle air bleed. The air–fuel mixture is then pulled
- 55. When an operator wants a speed increase, the throttle linkage is used to open the throttle
- 56. When the operator moves the throttle linkage past the part throttle position to more fully open
- 57. This air enters through the main pickup tube bleed holes. There, it mixes with the fuel
- 58. 3. Diaphragm Carburetors A diaphragm carburetor (Figure 29) is a carburetor that has a flexible diaphragm
- 59. Diaphragm Carburetor Operation The diaphragm carburetor is, in many ways, very much the same as a
- 60. Figure 30 The parts of a diaphragm carburetor Instead, it uses a diaphragm similar to that
- 61. The diaphragm is made from a flexible, rubber-like material. It’s stretched across a small space above
- 62. Figure 31 A diaphragm carburetor has two chambers: one for fuel and one for atmospheric pressure
- 63. As fuel flows from the fuel tank to the fuel inlet, the spring pushes down on
- 64. Downward movement of the diaphragm causes the control lever to pivot upward. This movement pushes up
- 65. Modes of Operation of a Diaphragm Carburetor Just as with every other type of carburetor, the
- 66. ■ Cold starting The only air that can get into the engine enters through openings around
- 67. During idle speeds, only a small amount of fuel is needed to keep the engine running.
- 68. When the throttle valve is moved past the idle position, it uncovers one more discharge port,
- 69. Fuel flows into the main nozzle through a passageway from the diaphragm chamber. Fuel going up
- 70. 4.Suction Feed Diaphragm Carburetors The suction feed diaphragm carburetor is a carburetor that combines the features
- 71. Some carburetors have the diaphragm mounted in a side chamber. Others have the diaphragm located between
- 72. A diaphragm fits between the carburetor and the fuel cup. The diaphragm works like an impulse
- 73. Fuel Systems FUEL INJECTION
- 74. FUEL INJECTION Fuel injection is the most modern method for carburetion in today’s power equipment engines.
- 75. FUEL INJECTION In today’s power equipment engines, fuel injection is becoming popular as using it leads
- 76. Conditions such as temperature, humidity, and altitude affect traditional carburetion, altering the efficiency of a carbureted
- 77. The disadvantage of fuel injection? Cost. Due to the high cost of fuel injection systems, almost
- 78. Direct Fuel Injection The direct system injects an extremely fine mist of fuel into the combustion
- 79. Indirect Fuel Injection The indirect fuel injection system is the most common type of fuel injection
- 80. Indirect Fuel Injection All modern fuel-injected power equipment engines use a type of electronic fuel injection
- 81. Fuel Injection System Сomponents Although many small power equipment engines don’t use fuel injection now, their
- 82. Fuel Pumps Fuel pumps used with electronic fuel-injected power equipment engines have three primary requirements: ■
- 83. The fuel pump consists of an electric armature that spins between two magnets and turns an
- 84. A check valve (outlet check ball) is incorporated to maintain pressure at the fuel injectors to
- 85. Fuel Filters Before fuel enters the fuel pump, it must go through a mesh filter that
- 86. Fuel Lines The damage in many cases will be internal and therefore you’ll not see it
- 87. Fuel Pressure Regulators The fuel pressure regulator maintains correct fuel pressure and keeps it above the
- 88. Fuel Injectors The fuel injector is an electronically operated solenoid that turns fuel on and off
- 89. The fuel injectors generally closed and are either fully closed or fully open. The ECM “tells”
- 90. Fuel injector tip openings are designed to provide a spray pattern that atomizes the fuel to
- 91. ECM The heart of all fuel injection systems is the ECM. The ECM receives signals from
- 92. ECM Inputs and Outputs The ECM has three types of inputs (Figure 43): ■ Basic ■
- 93. ECM Inputs and Outputs The basic inputs provide information that the ECM needs to select a
- 94. The correction inputs provide the information that the ECM needs to adjust the basic fuel discharge
- 95. Various sensors monitor the engine and atmospheric conditions such as throttle position, engine revolutions per minute
- 96. Engines with EFI may have one throttle valve for each cylinder. The throttle body contains the
- 97. EFI Self-Diagnostics Most modern power equipment engines that use EFI have a self-diagnostic system incorporated to
- 98. Basic Operation of the Fuel Injection System In a typical EFI system, the ECM must “know”
- 99. Electronic feedback and closed loop Electronic feedback means the system is self-regulating and the ECM is
- 100. Control loops and catalytic converters When conditions such as starting or wideopen throttle demand that the
- 101. Summary ■ The primary principles of carburetor operation are atomization, the process of combining air and
- 102. Wankel engine The Wankel engine is a type of internal combustion engine using an eccentric rotary
- 103. The engine was invented by German engineer Felix Wankel. He received his first patent for the
- 104. Design In the Wankel engine, the four strokes of a typical Otto cycle occur in the
- 105. The central drive shaft 8, called the eccentric shaft or E-shaft, passes through the center of
- 106. The best way to visualize the action of the engine is to look not at the
- 107. As the rotor rotates and orbitally revolves, each side of the rotor is brought closer to
- 108. While a four-stroke piston engine makes one combustion stroke per cylinder for every two rotations of
- 109. Wankel engines also generally have a much higher redline than a reciprocating engine of similar power
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