Pressurized air seal for combustion chamber

Abstract

Combustion apparatus (10) includes a combustion chamber (12, 212), a cover (24, 208) covering an end wall (14, 210) of the combustion chamber and defining a buffer space (26, 206) therebetween, and a blower (32, 202) external to the cover and supplying air to the buffer space and pressurizing the buffer space to a higher pressure than the combustion chamber such that leakage at penetrations (46) and/or interface (334, 336) flows from the buffer space into the combustion chamber, rather than the reverse, eliminating the need for leak-tight seals, and instead permitting leakage in a desired direction. In one embodiment, a first conduit (58) supplies air along a path (34) from the blower to the mixer and burner assembly without passing through the buffer space, and a second conduit (60) independently supplies air from the blower to the buffer space. A pressure dropping orifice (36) is provided between the blower and the mixer and burner assembly. A gas inlet port (40) is external to the cover (24) and downstream of the pressure dropping orifice (36). The buffer space (26) communicates with the blower (32) along an air flow path (44) upstream of the pressure dropping orifice (36). In another embodiment, air flows through the buffer space (20) to the mixer and burner assembly. The buffer space (26, 206) is thin and flat, and the cover (24, 208) covers only one end wall (14, 210) of the combustion chamber, not the other end wall nor the sidewall, such that the latter are accessible without removing the cover.

We claim:  
     
       1. Combustion apparatus comprising: 
       a combustion chamber having distally opposite first and second end walls, and having a sidewall extending between said end walls;  
       a cover external to said combustion chamber and covering said first end wall and defining a buffer space therebetween;  
       one or more penetrationsa plurality of penetrations including a mixer and burner assembly, a liquid inlet, a liquid outlet, a flame sensor, and an igniter, each extending through said first end wall between said buffer space and said combustion chamber;  
       a blower external to said cover and supplying air to said buffer space and pressurizing said buffer space to a higher pressure than said combustion chamber such that leakage at said one or more penetrations  penetrations in the first end wall flows from said buffer space into said combustion chamber;  
       asaid mixer and burner assembly extending into said combustion chamber and receiving combustion air from said blower;  
       a pressure dropping orifice between said blower and said mixer and burner assembly such that the pressure in said combustion chamber is lower than the pressure in said buffer space;  
       a first conduit supplying air from said blower to said mixer and burner assembly, and a second conduit independently supplying air from said blower to said buffer space,  
       wherein air flows through said first conduit along a path from said blower to said mixer and burner assembly without passing through said buffer space.  
     
     
       2. Combustion apparatus comprising: 
       a combustion chamber having distally opposite first and second end walls, and having a sidewall extending between said end walls;  
       a cover external to said combustion chamber and covering said first end wall and defining a buffer space therebetween;  
       one or more penetrationsa plurality of penetrations including a mixer and burner assembly, a liquid inlet, a liquid outlet, a flame sensor, and an igniter, each extending through said first end wall between said buffer space and said combustion chamber;  
       a blower external to said cover and supplying air to said buffer space and pressurizing said buffer space to a higher pressure than said combustion chamber such that leakage at said one or more penetrations  penetrations in the first end wall flows from said buffer space into said combustion chamber;  
       asaid mixer and burner assembly extending into said combustion chamber and receiving combustion air from said blower;  
       a pressure dropping orifice between said blower and said mixer and burner assembly such that the pressure in said combustion chamber is lower than the pressure in said buffer space,  
       wherein said mixer and burner assembly includes a portion external of said combustion chamber, and comprising a second cover external to said first mentioned cover and covering said external portion of said mixer and burner assembly and defining a second buffer space therebetween, said mixer and burner assembly having an inlet port communicating with said second buffer space.  
     
     
       3. The invention according to claim  2  wherein said first cover has a port communicating with said second buffer space such that said first mentioned buffer space and said second buffer space are in communication with each other through said port in said first cover, and such that air from said blower supplied to said first buffer space also flows through said port in said first cover to said second buffer space and then to said inlet port of said mixer and burner assembly. 
     
     
       4. Combustion apparatus comprising: 
       a combustion chamber having distally opposite first and second end walls, and having a sidewall extending between said end walls;  
       one or morea plurality of penetrations, including a mixer and burner assembly, a liquid inlet, a liquid outlet, a flame sensor, and an igniter, each extending through said first end wall;  
       a cover external to said combustion chamber and covering said first end wall and defining a buffer space therebetween;  
       a blower supplying air to said mixer and burner assembly along a first path through a first conduit, and supplying air to said buffer space along a second path through a second conduit and pressurizing said buffer space to a higher pressure than said combustion chamber, such that, in use, leakage at penetrations in the first end wall flow from the buffer space to the combustion chamber, wherein said first path extends from said blower to said mixer and burner assembly without passing through said buffer space.  
     
     
       5. The invention according to claim  4  comprising a pressure dropping orifice between said blower and said mixer and burner assembly such that the pressure in said combustion chamber is lower than the pressure in said buffer space. 
     
     
       6. The invention according to claim  5  wherein said mixer and burner assembly includes a gas inlet port downstream of said pressure dropping orifice. 
     
     
       7. The invention according to claim  6  wherein said gas inlet port is external to said cover. 
     
     
       8. The invention according to claim  5  wherein said buffer space communicates with said blower along said second path through said second conduit upstream of said pressure dropping orifice. 
     
     
       9. Combustion apparatus comprising: 
       a combustion chamber having distally opposite first and second end walls, and having a sidewall extending between said end walls, said combustion chamber having an exhaust outlet;  
       one or morea plurality of penetrations, including a mixer and burner assembly, a liquid inlet, a liquid outlet, a flame sensor, and an igniter, extending through said first end wall;  
       a cover external to said combustion chamber and covering said first end wall and defining a buffer space therebetween, said buffer space having a buffer outlet;  
       a blower supplying air to said buffer space and to said mixer and burner assembly,  
       wherein there is a first pressure drop R 1  from said blower to said mixer and burner assembly, a second pressure drop R 2  from said mixer and burner assembly to said combustion chamber, a third pressure drop R 3  from said blower to said buffer space, a fourth pressure drop R 4  across said buffer outlet, and a fifth pressure drop R 5  across said exhaust outlet, wherein            R                 3       R                 4       <           R                 1     +     R                 2         R                 5       .