Injector Nozzles

(c) A controlled seepage exists between the lapped surfaces of the

nozzle valve and its body to provide for lubrication. The leakage or

overflow passes around the spindle and into the pressure adjusting spring

chamber. From here, the fuel leaves the injector through the overflow

outlet and finally to the overflow lines, which lead back to the low

(4) Injector Nozzles (figure 45 on the following page). Because of

the widely differing requirements in the shapes of the fuel spray for

various chamber designs, and the wide range of engine power demands, there

is a large variety of injector nozzles in use. The spray nozzles are put

into two basic groups: pintle nozzles and hole nozzles. Pintle nozzles

generally are used in engines having precombustion or turbulence chambers,

whereas the hole nozzles generally are used in open chamber engines.

(a) In pintle nozzles, the nozzle valve carries an extension at

its lower end in the form of a pin (pintle) which protrudes through the hole

in the nozzle bottom. This requires the injected fuel to pass through an

annular orifice, producing a hollow, coneshaped spray, the nominal included

angle of which may be from 0 to 60, depending on the combustion chamber

requirement. The projection of the pintle through the nozzle orifice

includes a selfcleaning effect, discouraging the accumulation of carbon at

this point.

(b) A specific type of pintle nozzle used extensively in small

bore highspeed diesel engines is the throttling nozzle. It differs from

the standard pintle nozzle in that the pintle projects from the nozzle for a

much greater distance, and the orifice in the bottom of the nozzle body is

much longer. The outstanding feature of the throttling nozzle is its

control of the rate at which fuel is injected into the combustion chamber.

When no fuel is being injected, the pintle extends through the nozzle

orifice. At the beginning of the injection period, only a small quantity of

fuel

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