Patent ID: 6732508
Filing Date: 2004-05-11
Classification: F02B,Y02T

Abstract:
An exhaust system for an internal combustion engine, the engine being a low speed, two-cycle engine combusting a normally gaseous hydrocarbon as fuel, the engine comprising a cylinder having an exhaust port in communication with an exhaust manifold, the exhaust system comprising:an exhaust gas inlet, the inlet being connectable to the exhaust manifold of the internal combustion engine, the exhaust system having a direction of flow being the direction of flow of exhaust gases moving through the exhaust system when the system is connected to the exhaust manifold of the internal combustion engine and the engine is operating; an exhaust gas outlet spaced from the exhaust gas inlet in the direction of flow, the outlet being connectable to a muffler; a first tubular portion disposed between the exhaust gas inlet and outlet, the first tubular portion diverging in the direction of flow; and a second tubular portion disposed between the exhaust gas inlet and outlet and spaced from the first tubular portion in the direction of flow, the second tubular portion converging in the direction of flow; wherein, during operation of the engine to which the exhaust system is connected, a first, negative pressure pulse is generated in a direction opposite to the direction of flow to enhance the removal of exhaust gases from the cylinder through the exhaust port and a second, positive pressure pulse is thereafter generated in the direction opposite to the direction of flow to prevent the flow of freshly charged gas from the cylinder; and wherein during operation of the engine to which the exhaust system is connected, the first and second pressure pulses are timed to occur so as to reduce NOx emissions from the engine at a speed in the range of from 250 to 500 rpm.