Patent ID: 6382959
Filing Date: 2002-05-07
Classification: F23D,F23N

Abstract:
A method of designing a throttle ring for use in a burner so as to reduce a first blower pressure P1 upstream of a throttle plate movable within the throttle ring to a prescribed pressure P2 between the throttle plate and a retention plate downstream of the throttle plate at an adjustment range of the throttle plate within the throttle ring between a minimum air flow position and a maximum air flow position, comprising the steps of:measuring P1 values as a function of a range of flow rate values Q through the burner; measuring prescribed P2 values as a function of the range of flow rate values Q through the burner; measuring the air flow rate values Q through the burner as a function of movement of the retention plate within a retention ring of the burner distances X from the minimum flow position to the maximum flow position, the retention plate and the throttle plate being interconnected so as to move together; selecting a radius R1 of the throttle plate; selecting apertures in the throttle plate which provide air for a low firing rate at the minimum air flow position; calculating a minimum throttle ring radius R2 when the throttle plate is located at the minimum air flow position, using: (i) the following known or measured values: the air flow Q through the burner=the total flow through the burner, based upon a prescribed fuel flow rate and prescribed air/fuel ratio of said burner, AV1=an annular clearance area between the throttle plate and the throttle ring, QV1=an air flow rate through said annular clearance area AV1, CV1=a discharge coefficient of said annular clearance area AV1, P1=the blower discharge pressure upstream of the throttle plate, P2=the prescribed pressure between the throttle plate and the retention plate, AC1=a total fixed aperture area in the throttle plate, QC1=air flow through said fixed area AC1, CC1=a discharge coefficient of said fixed area AC1, R1=the throttle plate outside radius, R2=the throttle ring inside radius, Ve1=the air velocity generated by P1-P2, X=the displacement of the throttle plate or retention plate from the minimum air flow position, S=the length of a segment normal to air flow through the annular space between the throttle plate and the throttle ring, &rgr;W=the density of water, &rgr;A=the density of air, g=the acceleration due to gravity;and (ii) the equation, R2=(AV1/B+R12)Â½ based on the following relationships (1)-(5): Ve1=(2g(P1âˆ’P2)Â·(&rgr;W/&rgr;A))Â½â€ƒâ€ƒ(1) QV1=Qâˆ’QC1â€ƒâ€ƒ(2) QC1=CC1Â·AC1(2g(P1âˆ’P2)Â·(&rgr;W/&rgr;A))Â½â€ƒâ€ƒ(3) AV1=QV1/(CV1Â·Ve1),â€ƒâ€ƒ(4) AV1=&pgr;(R22âˆ’R12)â€ƒâ€ƒ(5); anddetermining a contoured surface of the throttle ring comprising the steps of: (a) assuming a plurality of small incremental adjustments of the throttle plate from the minimum air flow position toward the maximum air flow position along the central axis resulting in a segment at each increment on a reference line parallel to the central axis, (b) locating a transverse line S at the start of a segment at an angle &thgr; between said transverse line S and said reference line which is perpendicular to a section of said contoured surface corresponding to a prior segment nearer to said minimum flow position, said transverse line S being positioned to extend from the reference line, (c) inserting the angle &thgr; into the equation, R2=SÂ·sin(&thgr;)+R1, (d) determining a length of the transverse line S by substituting the equation resulting from step (c) into the equation, &pgr;Â·SÂ·(R1+R2)=QV1/(CV1Â·Ve1), thereby determining the coordinates of a point at said contoured surface of said throttle ring, and (e) repeating steps (b) through (d) to determine all of the points desired at the contoured surface of said throttle ring.