Fuel injector with radial and axial air inflow

1. A fuel injector comprising:

a pilot injector configured to spray fuel so as to form a first combustion region in a combustion chamber;

a main injector provided coaxially with the pilot injector so as to surround the pilot injector and configured to supply a fuel-air mixture that is a mixture of the fuel and air to form a second combustion region in the combustion chamber; and

an annular dividing wall configured to define a boundary between the pilot injector and the main injector, wherein:

the main injector includes:

a first inflow channel configured to take the air therethrough and give the air a major flow component in an axial direction;

a second inflow channel configured to take the air therethrough and give the air a major flow component in a radial direction;

a premixing chamber located downstream of the first inflow channel and the second inflow channel such that the air from the first inflow channel and the air from the second inflow channel meet in the premixing chamber; and

a main fuel injecting portion configured to inject the fuel only to the second inflow channel;

the first inflow channel supplies to the premixing chamber the air having the major flow component in the axial direction;

the second inflow channel supplies to the premixing chamber the air having the major flow component in a direction from a radially outer side toward a radially inner side;

a position of an exit end of the pilot injector is upstream of a position of an exit end of the main injector in the axial direction; and

the exit end of the pilot injector is an exit end of the annular dividing wall.

2. The fuel injector according to claim 1 , wherein the main fuel injecting portion injects the fuel to the second inflow channel from a portion which defines a boundary between the first inflow channel and the second inflow channel.

3. The fuel injector according to claim 1 , wherein a ratio W/Dm that is a ratio of an axial distance W between the exit ends to an inner diameter Dm of the exit end of the main injector is between 0 and 0.25.

4. The fuel injector according to claim 1 , wherein

a ratio T/Dp that is a ratio of a radial width T of the exit end of the annular dividing wall to an inner diameter Dp of the exit end of the pilot injector is 0.02 to 0.15.

5. The fuel injector according to claim 1 , wherein a radially inner surface of the first inflow channel includes: an inside flare portion formed in a vicinity of an exit end of the radially inner surface and configured to increase in diameter toward a downstream side; and an inside reduced-diameter portion provided upstream of the inside flare portion and configured to reduce in diameter toward the downstream side.

6. The fuel injector according to claim 1 , wherein a ratio Q 1 /Q 2 that is a ratio of a flow quantity Q 1 of the air flowing through the first inflow channel to a flow quantity Q 2 of the air flowing through the second inflow channel is in a range from 3/7 to 7/3.

7. The fuel injector according to claim 1 , wherein:

a swirling unit is attached to an entrance of the second inflow channel; and

the swirling unit includes swirl blades, each of which is formed in such a twisted shape that when the air flows through a portion of the swirl blade that is closest to the main fuel injecting portion, the air flows straight in a substantially radially inward direction, and a swirling component of the air increases as a portion where the air flows becomes further away from the main fuel injecting portion.

8. A fuel injector comprising:

a pilot injector configured to spray fuel so as to form a first combustion region in a combustion chamber;

a main injector provided coaxially with the pilot injector so as to surround the pilot injector and configured to supply a fuel-air mixture that is a mixture of the fuel and air to form a second combustion region in the combustion chamber; and

an annular dividing wall configured to define a boundary between the pilot injector and the main injector, wherein:

the main injector includes: a first inflow channel configured to take the air therethrough and give the air a major flow component in an axial direction; a second inflow channel configured to take the air therethrough, give the air a major flow component in a radial direction, and cause the air therein to meet the air from the first inflow channel; and a main fuel injecting portion configured to inject the fuel only to the second inflow channel;

a first swirling unit and a second swirling unit are respectively attached to an entrance of the first inflow channel and an entrance of the second inflow channel;

the second swirling unit includes a plurality of swirling portions, the swirling portion located closest to the main fuel injecting portion causes inflow air to flow straight in a substantially radially inward direction, and the remaining swirling portions give a swirl velocity component to inflow air;

a position of an exit end of the pilot injector is upstream of a position of an exit end of the main injector in the axial direction; and

the exit end of the pilot injector is an exit end of the annular dividing wall.

9. A fuel injector comprising:

a pilot injector configured to spray fuel so as to form a first combustion region in a combustion chamber; and

a main injector provided coaxially with the pilot injector so as to surround the pilot injector and configured to supply a fuel-air mixture that is a mixture of the fuel and air to form a second combustion region in the combustion chamber, wherein:

the main injector includes:

a first inflow channel configured to take the air therethrough and give the air a major flow component in an axial direction;

a second inflow channel configured to take the air therethrough and give the air a major flow component in a radial direction;

a premixing chamber located downstream of the first inflow channel and the second inflow channel such that the air from the first inflow channel and the air from the second inflow channel meet in the premixing chamber; and

a main fuel injecting portion configured to inject the fuel only to the second inflow channel;

the first inflow channel supplies to the premixing chamber the air having the major flow component in the axial direction;

the second inflow channel supplies to the premixing chamber the air having the major flow component in a direction from a radially outer side toward a radially inner side;

the fuel injector further comprises an annular dividing wall configured to define a boundary between the pilot injector and the main injector; and

virtual extended inner peripheral surface extending from an exit end of an inner peripheral surface of the annular dividing wall in a downstream direction and a virtual extended outer peripheral surface extending from an exit end of an outer peripheral surface of the annular dividing wall in the downstream direction gradually separate from each other as the virtual extended inner peripheral surface and the virtual extended outer peripheral surface extend in the downstream direction.

10. A fuel injector comprising:

a pilot injector configured to spray fuel so as to form a first combustion region in a combustion chamber; and

a main injector provided coaxially with the pilot injector so as to surround the pilot injector and configured to supply a fuel-air mixture that is a mixture of the fuel and air to form a second combustion region in the combustion chamber, wherein:

the main injector includes: a first inflow channel configured to take the air therethrough and give the air a major flow component in an axial direction; a second inflow channel configured to take the air therethrough, give the air a major flow component in a radial direction, and cause the air therein to meet the air from the first inflow channel; and a main fuel injecting portion configured to inject the fuel only to the second inflow channel;

a first swirling unit and a second swirling unit are respectively attached to an entrance of the first inflow channel and an entrance of the second inflow channel;

the second swirling unit includes a plurality of swirling portions, the swirling portion located closest to the main fuel injecting portion causes inflow air to flow straight in a substantially radially inward direction, and the remaining swirling portions give a swirl velocity component to inflow air;

the fuel injector further comprises an annular dividing wall configured to define a boundary between the pilot injector and the main injector; and

a virtual extended inner peripheral surface extending from an exit end of an inner peripheral surface of the annular dividing wall in a downstream direction and a virtual extended outer peripheral surface extending from an exit end of an outer peripheral surface of the annular dividing wall in the downstream direction gradually separate from each other as the virtual extended inner peripheral surface and the virtual extended outer peripheral surface extend in the downstream direction.