Vessel propulsion apparatus, vessel, vessel engine, and exhaust structure of vessel engine
A vessel propulsion apparatus includes an engine and a propulsion unit to be driven by the engine. The engine includes cylinders arranged in series, exhaust ports respectively connected to combustion chambers of the cylinders and curved in a predetermined downstream direction to allow exhaust gases to flow out from the combustion chambers, and a collecting exhaust pipe. The collecting exhaust pipe is integral with the exhaust ports, and extends in the downstream direction to allow exhaust gases in the exhaust ports to flow in the downstream direction. At least one of a plurality of connector portions that individually connect the exhaust ports to the collecting exhaust pipe includes a concave portion at an inner surface thereof.
1. A vessel propulsion apparatus comprising:
an engine; and
a propulsion unit to be driven by the engine; wherein
the engine includes:
a plurality of cylinders arranged in series and each including a combustion chamber;
a plurality of exhaust ports respectively connected to the combustion chambers of the plurality of cylinders and curved in a predetermined downstream direction of a flow of exhaust gases to allow the exhaust gases to flow out from the combustion chambers;
a collecting exhaust pipe integral with the plurality of exhaust ports and extending in the downstream direction to allow the exhaust gases in the plurality of exhaust ports to flow in the downstream direction; and
a plurality of connector portions that individually connect the plurality of exhaust ports to the collecting exhaust pipe, and each of the plurality of connector portions includes a first concave portion at an inner surface thereof and a second concave portion located in a region of an inner surface of the collecting exhaust pipe, and the first concave portion and the second concave portion do not extend through the plurality of connector portions.
2. The vessel propulsion apparatus according to claim 1 , wherein
each of the plurality of exhaust ports includes an upstream portion connected to the combustion chamber and a downstream portion that is curved from the upstream portion in the downstream direction and connected to the collecting exhaust pipe; and
the first concave portion is located at an inner surface of the downstream portion.
3. The vessel propulsion apparatus according to claim 2 , wherein the first concave portion is located in a region of the inner surface of the downstream portion that is more distant from a center of curvature of the downstream portion than a central axis of the downstream portion.
4. The vessel propulsion apparatus according to claim 3 , wherein
the exhaust port includes a pair of exhaust ports for each of the plurality of cylinders;
the pair of exhaust ports include an upstream exhaust port and a downstream exhaust port located farther downward in the downstream direction of the flow of exhaust gases than the upstream exhaust port;
the downstream portion of the upstream exhaust port and the downstream portion of the downstream exhaust port are merged together; and
the first concave portion is located in a region of an the inner surface of the downstream portion of the upstream exhaust port that is more distant from a center of curvature of the downstream portion of the upstream exhaust port than a central axis of the downstream portion of the upstream exhaust port.
5. The vessel propulsion apparatus according to claim 4 , wherein, in a cross section of the downstream portion containing the center of the curvature of the downstream portion and the central axis of the downstream portion, the first concave portion has a radius of curvature that is smaller than a radius of curvature of the region of the inner surface of the downstream portion.
6. The vessel propulsion apparatus according to claim 2 , wherein
the plurality of cylinders include a first cylinder located at a top of the plurality of cylinders in a direction opposite to the downstream direction and a second cylinder adjacent to the first cylinder; and
the first concave portion located at the exhaust port connected to the combustion chamber of the second cylinder is larger than the first concave portion located at the exhaust port connected to the combustion chamber of any cylinder other than the second cylinder of the plurality of cylinders.
7. The vessel propulsion apparatus according to claim 1 , wherein
each of the plurality of exhaust ports includes an upstream portion connected to the combustion chamber and a downstream portion that is curved from the upstream portion in the downstream direction and connected to the collecting exhaust pipe; and
the second concave portion is located in a region of the inner surface of the collecting exhaust pipe that is adjacent to the downstream portion.
8. The vessel propulsion apparatus according to claim 7 , wherein the second concave portion is located in a region of the inner surface of the collecting exhaust pipe that is closer to the exhaust port than a central axis of the collecting exhaust pipe.
9. The vessel propulsion apparatus according to claim 7 , wherein
the plurality of cylinders include a first cylinder located at a top of the plurality of cylinders in a direction opposite to the downstream direction and other cylinders; and
the second concave portion, located in a region of the inner surface of the collecting exhaust pipe that is adjacent to the downstream portion of the exhaust port connected to the combustion chamber of the first cylinder, is larger than the second concave portion located in a region that is adjacent to the downstream portion of the exhaust port connected to the combustion chamber of each of the other cylinders.
10. The vessel propulsion apparatus according to claim 1 , wherein
the first concave portion and the second concave portion define to direct the exhaust gases in the plurality of connector portions in the downstream direction.
11. The vessel propulsion apparatus according to claim 1 , wherein
the engine includes a crankshaft extending along a vertical direction; and
the vessel propulsion apparatus includes an outboard motor including a drive shaft connected to the crankshaft and extending along the vertical direction, a propeller shaft extending along a horizontal direction, a propeller functioning as the propulsion unit and connected to the propeller shaft, and a transmission to transmit rotation of the drive shaft to the propeller shaft.
12. A vessel comprising:
a hull; and
the vessel propulsion apparatus according to claim 1 mounted to the hull to provide a thrust to the hull.
13. A vessel engine comprising:
a plurality of cylinders arranged in series and each including a combustion chamber;
a plurality of exhaust ports respectively connected to the combustion chambers of the plurality of cylinders and curved in a predetermined downstream direction of a flow of exhaust gases to allow the exhaust gases to flow out from the combustion chambers;
a collecting exhaust pipe integral with the plurality of exhaust ports and extending in the downstream direction to allow the exhaust gases in the exhaust ports to flow in the downstream direction; and
a plurality of connector portions that individually connect the plurality of exhaust ports to the collecting exhaust pipe, and each of the plurality of connector portions including a first concave portion at an inner surface thereof and a second concave portion located in a region of an inner surface of the collecting exhaust pipe, and the first concave portion and the second concave portion do not extend through the plurality of connector portions.
14. An exhaust structure for a vessel engine, the exhaust structure comprising:
a plurality of exhaust ports respectively connected to combustion chambers of a plurality of cylinders arranged in series and curved in a predetermined downstream direction of a flow of exhaust gases to allow the exhaust gases to flow out from the combustion chambers;
a collecting exhaust pipe integral with the plurality of exhaust ports and extending in the downstream direction to allow the exhaust gases in the plurality of exhaust ports to flow in the downstream direction; and
a plurality of connector portions that individually connect the plurality of exhaust ports to the collecting exhaust pipe, and each of the plurality of connector portions including a first concave portion at an inner surface thereof and a second concave portion located in a region of an inner surface of the collecting exhaust pipe, and the first concave portion and the second concave portion do not extend through the plurality of connector portions.