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sure, but in reality the major work performed in the cylinder is concentrated in a lesser portion of the piston travel. This condition can be compared with a steam engine using high steam pressure with a very short valve cut-off. In a combustion system of this design, the fuel injection valve is inconveniently located in the center of the cylinder head. rating the controlled turbulence chamber removes the foregoing disadvantages in engine operation. As shown in the illustration, a spherical water cooled combustion chamber is cast integrally with the cylinder head, and a throat connects this chamber with the cylinder combustion space. During the compression stroke the air is forced into the chamber, entering tangentially at high velocity and producing vigorous turbulence. Fuel oil at considerably lower pressure is sprayed into the combustion chamber through a multiple ori- fice spray nozzle which has comparatively large openings. The injection period is twice as long as that in a direct injection system. The fuel spray mixes rapidly and thoroughly with the turbu- lent air. As combustion proceeds, the pressure rise per degree of crank travel is only about 26 Ib per sq in. The maximum combustion pressure is |
thereby held to a conservative figure. An indi- cator diagram of this action will show a relatively lower pressure rise at the end of the compression stroke and a broader power or expansion curve. This develops a higher mean effective pressure with the benefit of low compression and combus- tion pressures, and, again in comparison with the steam engine principle, is similar to the use of lower pressure steam with a longer steam cut-off. provides uniform clean and efficient combustion, is less sensitive to variation in fuel oil character- istics, and consequently can burn lower grade, cheaper fuels. The water cooled combustion chamber sepa- rated from the cylinder proper provides protec- tion for the piston rings and exhaust valves from the intense heat to which these parts are exposed in other systems where the combustion chamber is the clearance volume between the piston and the cylinder head. Thus the more common trou- bles such as clogged spray valves and sticking piston rings are avoided. Many years of experience have proved that Diesel engines equipped with a controlled turbu- lence combustion system operate more smoothly, quietly, and with a minimum of maintenance cost and service interruptions. |
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WITH THIS exclusive combustion system, De La Vergne Diesel engines are less sensitive to variations in fuel oil characteristics, without sacrifice of clean, smoke-free combustion. |
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