Patent ID: 7980070

Claim:
An exhaust gas cooling system for an engine, comprising: an exhaust gas conduit having an inner tube defining an exhaust gas passage through which exhaust gases discharged from the engine pass, and an outer tube surrounding the inner tube and thereby defining a cooling water passage between the inner tube and outer tube, the cooling water passage being configured to pass cooling water that has cooled the engine; and a water-lock configured to prevent a backward flow of water, an exhaust gas conduit coupling section being formed at an upstream end portion thereof, the water-lock being coupled with a downstream end of the exhaust gas conduit through the exhaust gas conduit coupling section; wherein the exhaust gas conduit coupling section of the water-lock and the outer tube of the exhaust gas conduit are coupled with each other, the inner tube extending into an interior of the water-lock to form a cooling water releasing port between the exhaust gas conduit coupling section and the inner tube, the cooling water releasing port being configured to release the cooling water flowing through the cooling water passage such that the cooling water released from the cooling water releasing port and the exhaust gases discharged from the exhaust gas passage are mixed together within the water-lock, and wherein a downstream end part of the inner tube is formed such that the diameter of the inner tube becomes larger toward the downstream end so that the cooling water released into the water-lock diffuses.