Gas appliance combustion systems

A method of reducing required blower power in an induced draft combustion system wherein combustion products are moved through the system by a blower blowing combustion products into an outlet duct, comprising:

• recovering pressure from dynamic energy of flow of said combustion products by gradually diverging said outlet duct in terms of polar coordinates having a polar axis, overlapping radius vectors and a variable polar angle of said overlapping radius vectors relative to said polar axis;
• increasing a difference between said overlapping radius vectors from a minimum near said blower incrementally to a maximum remote from said blower in terms of incremental polar angles;
• and
• structuring said outlet duct with cross-sections increasing incrementally starting near said blower in terms of said increasing difference between said overlapping radius vectors.

A method of reducing required blower power in an induced draft combustion system wherein combustion products are moved through the system by a blower blowing combustion products into an outlet duct, comprising:

• recovering pressure from dynamic energy of flow of said combustion products by gradually diverging said outlet duct by:
• establishing more than one polar coordinate system having said outlet duct therebetween;
• diverging a first part of said outlet duct in a first one of said polar coordinate systems in terms of first overlapping radius vectors and a variable first polar angle of said first overlapping radius vectors relative to a first polar axis;
• increasing a difference between said first overlapping radius vectors from a first minimum near said blower incrementally to a first maximum at an end of said first part of said outlet duct away from said blower in terms of incremental first polar angles;
• structuring said first part of said outlet duct with cross-sections increasing incrementally starting near said blower in terms of said increasing difference between said overlapping first radius vectors to said end of the first part of said outlet duct;
• diverging a second part of said outlet duct in a second polar coordinate system by second overlapping radius vectors and a variable second polar angle of said second overlapping radius vectors relative to a second polar axis;
• increasing a difference between said second overlapping radius vectors from a second minimum at least as large as said first maximum at said end of the first part of said outlet duct incrementally to a second maximum at an end of said second part of said outlet duct away from said first part in terms of incremental second polar angles;
• structuring said second part of said outlet duct with cross-sections increasing incrementally starting near said end of said first part of said outlet duct in terms of said increasing difference between said overlapping second radius vectors to said end of the second part of said outlet duct.

A method of recovering pressure from dynamic energy of flow of combustion products in a combustion system wherein combustion products move through the system into an outlet duct, comprising in combination:

• diverging said outlet duct in terms of polar coordinates having a polar axis, overlapping radius vectors and a variable polar angle of said overlapping radius vectors relative to said polar axis;
• increasing a difference between said overlapping radius vectors in a direction of flow of said combustion products from a minimum incrementally to a maximum in terms of incremental polar angles;
• and
• structuring said outlet duct with cross-sections increasing incrementally starting at said minimum in terms of said increasing difference between said overlapping radius vectors.

In a combustion system wherein combustion products move through the system into an outlet duct, the improvement comprising in combination:

• a divergence of said outlet duct in terms of polar coordinates having a polar axis, overlapping radius vectors and a variable polar angle of said overlapping radius vectors relative to said polar axis;
• a difference between said overlapping radius vectors increasing in a direction of flow of said combustion products from a minimum incrementally to a maximum in terms of incremental polar angles;
• and
• said outlet duct having cross-sections increasing incrementally in said direction of flow of said combustion products in terms of said increasing difference between said overlapping radius vectors.