Burner, combustion apparatus, water heating apparatus and combustion method

1. A burner comprising:

a plurality of first burner ports that combust a first air-fuel mixture to generate first flames;

a gap that surrounds the first burner ports; and

a plurality of second burner ports that are disposed on either side of the gap, the second burner ports combusting a second air-fuel mixture to generate second flames and hold the first flames,

wherein the second burner ports include first pairs of second burner ports and second pairs of second burner ports, each first pair of second burner ports being formed on either side of a corresponding one of the first burner ports, each second pair of second burner ports being formed on either side of a corresponding one of drawing parts formed between the first burner ports, an interval between each second pair of second burner ports being narrower than an interval between each first pair of second burner ports, and

wherein the gap blocks a passage of the first air-fuel mixture.

2. The burner of claim 1 , wherein

the second flames are formed by combustion of the second air-fuel mixture whose air/fuel ratio is lower than the first flames.

3. The burner of claim 1 , further comprising:

a first burner unit part that includes the first burner ports; and

a second burner unit part that includes the second burner ports,

wherein the gap is made outside the first burner unit part by the second burner unit part.

4. The burner of claim 1 , wherein each first burner port includes a plurality of small burner ports.

5. The burner of claim 1 , further comprising:

a first burner unit part that includes the first burner ports; and

a second burner unit part that includes the second burner ports,

wherein the gap is formed on the first burner unit part.

6. The burner of claim 1 , wherein

the interval between each second pair of second burner ports is narrower than a width of each first burner port.

7. The burner of claim 1 , wherein

a shape of each first burner port is any of a pentagon, an oval and a circle, to generate a lean combustion surface of a corresponding one of the first flames that is either a circle or an oval, and the second burner ports generate an annular flame surface around the lean combustion surface using the second flames.

8. The burner of claim 1 , wherein

the second pairs of the second burner ports protrude toward the gap between the plurality of the first burner ports that are adjacent to each other.

9. The burner of claim 1 , wherein

each of the second burner ports includes an outer wall that is higher than an end of each first burner port, the outer wall guiding the second flame to either a side of the first flames or a side of another second flame that faces thereto.

10. A combustion apparatus comprising:

a housing;

a burner that is disposed in the housing; and

a mixing unit that differentiates a mixing ratio of air to fuel gas to generate a first air-fuel mixture and a second air-fuel mixture that have different air-fuel ratios,

wherein the burner includes:

a plurality of first burner ports that combust the first air-fuel mixture, which is supplied from the mixing unit, to generate first flames;

a gap that surrounds the first burner ports;

a plurality of second burner ports that are disposed on either side of the gap, the second burner ports combusting the second air-fuel mixture, which is supplied from the mixing unit, to generate second flames and hold the first flames, and

wherein the second burner ports include first pairs of second burner ports and second pairs of second burner ports, each first pair of second burner ports being formed on either side of a corresponding one of the first burner ports, each second pair of second burner ports being formed on either side of a corresponding one of drawing parts formed between the first burner ports, an interval between each second pair of second burner ports being narrower than an interval between each first pair of second burner ports, and

wherein the gap blocks a passage of the first air-fuel mixture.

11. A combustion method comprising:

combusting a first air-fuel mixture using a plurality of first burner ports, to generate first flames;

combusting a second air-fuel mixture using a plurality of second burner ports that are disposed on either side of a gap, to generate second flames, the gap surrounding the first burner ports, the gap blocking a passage of the first air-fuel mixture, the second burner ports including first pairs of second burner ports and second pairs of second burner ports, each first pair of second burner ports being formed on either side of a corresponding one of the first burner ports, each second pair of second burner ports being formed on either side of a corresponding one of drawing parts formed between the first burner ports, an interval between each second pair of second burner ports being narrower than an interval between each first pair of second burner ports; and

holding the first flame by the second flames.

12. A water heating apparatus comprising:

a heat exchanging unit that carries out heat exchange between combustion exhaust of a burner and supplied water, the heat exchanging unit supplying hot water using the supplied water,

wherein the burner includes:

a plurality of first burner ports that combust a first air-fuel mixture, to generate first flames;

a gap that surrounds the first burner ports;

a plurality of second burner ports that are disposed on either side of the gap, the second burner ports combusting a second air-fuel mixture, to generate second flames and hold the first flames, and

wherein the second burner ports include first pairs of second burner ports and second pairs of second burner ports, each first pair of second burner ports being formed on either side of a corresponding one of the first burner ports, each second pair of second burner ports being formed on either side of a corresponding one of drawing parts formed between the first burner ports, an interval between each second pair of second burner ports being narrower than an interval between each first pair of second burner ports, and

wherein the gap blocks a passage of the first air-fuel mixture.