GB704800A - Improvements in or relating to an internal combustion engine - Google Patents

Abstract

704,800. Combustion chambers. TEXACO DEVELOPMENT CORPORATION. Oct. 16, 1951, No. 24091/51. Classes 7(2) and 7(3) The invention relates to internal-combustion engines with fuel injection and ignition means having an auxiliary combustion chamber. The cylinder head 16, Fig. 1, of a four-stroke engine is formed with a disc-shaped auxiliary combustion chamber 20 that is surrounded by a water jacket 21, the diameter of chamber 20 being only slightly less than that of the cylinder 10 and having flat end walls 22, Fig. 2; the latter may alternatively be convex or concave so that the chamber is nearly spherical in shape or the chamber may comprise the space formed by any solid of revolution, all such configurations being defined as " disc-shaped." In one wall 22 is the inlet valve 25 and in the other wall is the exhaust valve 27 whilst the chamber 20 is connected to the main combustion space 28 by means of a throat 29, Fig. 1, of circular or elliptical cross-section which is tangential to a circle concentric with but having a diameter of between 0.5-0.75 of that of the auxiliary combustion chamber. Extending into the chamber 20 is a fuel injection nozzle 32 having a cone-shaped spray which substantially fills the width of the auxiliary combustion chamber whilst less than 90 degrees in an anticlockwise direction from the fuel nozzle is located a sparking or glow plug 35. As the piston 12 approaches T.D.C. on the compression stroke the air in the main combustion space 18 is forced into the chamber 20 and the disposition of the throat 29 is such as to cause it to swirl in the chamber in the direction of the arrow 30 whilst the constricted area of the throat, i.e. between 0.09-0.13 square inches produces an excess of pressure of between 25- 50 pounds per square inch in the space 18 over that in the auxiliary chamber 20 at the time fuel injection commences which is between 50 degrees-25 degrees before T.D.C.; this excess pressure continues until between 25 degrees-15 degrees before T.D.C. at which time about 75 per cent of the air has been forced into the auxiliary chamber 20 where it rotates as a speed of between 4-15 rotations per engine revolution. Even though the pressure rises very rapidly in the chamber 20 during the last stages of the combustion and quickly exceeds that in the main space. 18 the compression air swirl in the chamber 20 is relatively unaffected at such a late period in the compression stroke since any tendency for backflow from chamber 20 into the main space is prevented by the piston blocking the throat until T.D.C. has been passed by which time the injection under any conditions of load has been completed, the air swirl having ensured the impregnation of the air at the desired fuel-air ration throughout the injection period. When the injection starts on each cycle the immediate ignition of the first increment of injected fuel initiates combustion and a flame front is established which extends from the sparking plug 35 to the centre of the chamber and travels at high velocity counter to the direction of the air swirl although it remains stationary with respect to the chamber walls. The succeeding increments of fuel-impregnated compressed-swirling air sustains the flame fronts until injection has ceased and the piston has passed T.D.C. The engine compression ratio is between 8-13:1 and empirical formulµ are given for obtaining the swirl rate, air velocity and pressure drops through the throat. In a modification, as applied to a uniflow scavenged two-stroke engine with piston controlled inlet ports just above the B.D.C. position of the piston, the auxiliary combustion chamber is mounted vertically at the side of the top part of the cylinder and communicates with the main combustion space through a horizontal throat, the chamber having an exhaust valve in each side wall. In a further modification, the position of the inlet and exhaust ports in the two-stroke engine is interchanged and the auxiliary combustion chamber is arranged horizontally at the side of the top of the cylinder. In another modification, the engine is provided with an overhead auxiliary combustion chamber 119, Fig. 8, and piston controlled inlet and exhaust ports just above the B.D.C. position of the piston; two sets of inlet ports 130, 131, Fig. 9, are provided, the sets being opposed and each comprising three ports that are inclined so that the centre lines thereof intersect at a focal point 135 in the lower part of the cylinder and to one side of its longitudinal axis. The set of exhaust ports 138, which is located opposite the focal point 135 and between the two sets of inlet ports extend further up the height of the cylinder wall than the inlet ports 130, 131. The two streams of scavenging air meet at the focal point 135, are thereby deflected upwardly and follow the path indicated by the arrows 140, 141, Fig. 8, so that the scavenging air does not transverse the chamber 119, thus enabling a scavenging ratio of 1.2-1.6: 1 to be attained. In the foregoing embodiments the timing of the ignition spark is set to coincide with the injection advance and the peak pressure rise of the cycle occurs about 5 degrees after T.D.C. Examples of the dimensions of the cylinder and combustion chamber are given.