Technical Training Carburetion What does a carburetor do
Technical Training Carburetion
What does a carburetor do? How does it do it? Why so many different types?
Pressure n. Atmospheric n 14. 7 pressure at sea level is 14. 7 PSI = 1 bar = 100 kilopascal = 29. 5 inches of mercury n. Anything less than that is low pressure or vacuum n. A carburetor operates on a pressure differential created by a venturi fluids
Daniel Bernoulli's Theorem In 1738 Daniel Bernoulli, a Swiss physicist, observed and measured fluid flow behavior. He proposed that a fluid’s velocity, or it’s speed, increases, the pressure decreases. This is known as the Bernoulli Effect or the Bernoulli Principle.
Pressure Differential Experiments it rises up faster moving air causes a low pressure area on top of the paper, air pressure in the room pushes up on the bottom of the paper they roll together Paper Strip Soda Cans low pressure is created between the cans, high pressure in the room pushes them together
What is a venturi? n. The above picture represents a tube that has been narrowed down, forming a venturi. n. The red arrows represent air moving through the venturi.
Venturi Effect a fine spray of atomized water will appear fast moving air going across the top of the straw creates a low pressure zone, higher air pressure in the room pushes down on the water in the cup, pushing the water up the tube Main Nozzle Demonstrator
Atomization and Vaporization atomized vaporized
Venturi Examples Airflow Main Fuel Discharge Nozzle
Carburetor Function Fuel Pump Jet System Metering Systems
Typical Chain Saw Carburetor Yellow Indicates Fuel Blue Lines indicate Airflow Bypass Ports Discharging Fuel Main Nozzle Discharging Fuel
Crankcase Vacuum atmospheric
Fuel Pump Operation Pumping Chamber Check Valves Impulse Port Filter Screen & Opening to Inlet Needle
Fuel Pump Action Diaphragm Flexes Up Diaphragm Flexes Down
Metering System Brass Seat Inlet Needle Viton Tip
Discharge Ports
Fuel Metering Control Mixture Adjustment Screws Fixed Metering Jet leaner Limiter Caps Over Screws
Carb Operation
Summary n Bernoulli Effect states that as the velocity of a fluid, or air, increases, the pressure decreases n Carburetors air to mix use a venturi to create the low pressure zone for fuel and n Fuel is atomized in the venturi and further vaporized by the heat of the engine components, which aids in cooling n Small, handheld equipment engines use compact, diaphragm type carburetors that combine the fuel pump, metering system, and fuel delivery, through a jet and port system, for precise control of fuel for engine needs
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