CARBURETOR 



1181 



CARBURETOR 



buncles and other precious gems. The car- 

 buncle is named in Exodus XXVIII as one of 

 the gems in the breastplate of Aaron, the high 

 priest of the Children of Israel. See GARNET; 

 PRECIOUS STONES; HIGH PRIEST. 



CARBURETOR, kar'buretur. In an inter- 

 nal combustion engine using a liquid fuel, a 

 carburetor is a device for converting the liquid 

 into a mist or vapor and for mixing the vapor 

 with air in such proportions that the mixture 

 will burn instantly and without smoke. The 

 function of the carburetor, in other words, is 

 to insure perfect combustion. It must mix the 

 fuel with air under wide variations of engine 

 speed and power, must vaporize the mixture 

 under variations of temperature, must respond 

 at once to a demand for greater or less speed, 



the carburetor sometimes by gravity from a 

 tank situated at a higher level; but usually it 

 is forced into the carburetor by air pressure or 

 automatically by combustion which creates a 

 pressure greater than the pressure of air in 

 the storage tank. An excessive flow of gasoline 

 into the carburetor is prevented by a float in 

 a chamber through which the gasoline flows. 

 As the level of gasoline in the carburetor 

 reaches the desired point, the float rises and 

 finally closes a valve in the supply pipe. 



From the float chamber a passage leads to 

 a jet nozzle, through which the gasoline is 

 sprayed into the mixing chamber. The nozzle 

 is about one-sixteenth of an inch above the 

 level of the liquid in the float chamber when 

 the air pressure at the jet and in the float 



High Speed 

 Adjustment 



Constant Metering 

 AirOpening Pin 



Metering Upper 

 Pin Nozzle Automatic 

 Air Valve 



Spray Nozzle' 



ONE FORM OF CARBURETOR 

 Showing exterior appearance and cross-section through center. 



and must do all these things in spite of varia- 

 tions in the quality of the gasoline or other 

 fuel used. The carburetor is, therefore, a very 

 delicate instrument, but at the same time its 

 method of operation is simple and easily under- 

 stood. 



The process may be more quickly under- 

 stood if the meaning of the word carburetor 

 is known. To carburate means to saturate or 

 combine chemically with carbon; that is, the 

 carburetor combines air with carbon, which is 

 not pure, but may be in the form of gasoline, 

 kerosene or other liquid. The process of mix- 

 ing the air and carbon is called carburation. 

 The modern carburetor usually has three inlets 

 and one outlet. One of the inlets is for the 

 fuel, another is for air, and there is usually an 

 additional inlet, called the auxiliary or second- 

 ary inlet, also for air. The only outlet is to 

 the engine, and it usually has the throttle 

 valve attached to it. 

 The Process of Carburation, The fuel enters 



chamber are the same. Under these conditions 

 there is no flow of liquid. However, when the 

 piston of .the engine is drawn back, the air 

 pressure at the nozzle and in the air pipe is 

 reduced. As the pressure at the nozzle is then 

 less than the pressure in the float chamber, 

 the liquid is at once forced through the nozzle 

 into the mixing chamber. When the engine 

 has been at rest it is necessary to make this 

 initial suction at the nozzle by "turning the 

 engine over," or "cranking" it, which may be 

 done by hand or by a mechanical appliance 

 called a "starter." 



The air inlet, which is usually protected with 

 a fine screen to keep out dirt, also opens into 

 the mixing chamber. Under normal conditions 

 the air inlet is adjusted so that a sufficient sup- 

 ply of air enters to secure perfect combustion. 

 However, if the engine is going at high speed, 

 the liquid, being heavier, tends to flow into 

 the mixing chamber more rapidly than needed. 

 To offset this increase, most carburetors are 



