Variable flow nozzle for a burner assembly

Abstract

A nozzle for a burner assembly has a nozzle body, a valve member, and a spring. The nozzle body has an inlet, an outlet, and a fuel passageway extending from the inlet to the outlet. The valve member is positioned within the fuel passageway and is movable between a closed position, in which fuel flow through the outlet is substantially obstructed, and an open position, in which fuel flow through the outlet is permitted. The spring is disposed within the nozzle body and biases the valve member toward the closed position. The valve member moves to the open position in response to a predetermined fuel pressure applied to the valve member. The nozzle operates mechanically and has a variable flow area based on the fuel pressure applied. This increases the dynamic turndown ratio compared to fixed orifice nozzles to provide optimal fuel-air mixing over dynamic flow ranges.

What is claimed is: 
     
         1 . A nozzle, comprising:
 a nozzle body having an inlet, an outlet, and a fuel passageway extending from the inlet to the outlet;   a valve member positioned within the fuel passageway, the valve member movable between a closed position, in which fuel flow through the outlet is substantially obstructed, and an open position, in which fuel flow through the outlet is permitted;   a spring disposed within the nozzle body, the spring having a spring rate and configured to bias the valve member toward the closed position; and   wherein the valve member moves to the open position in response to a predetermined fuel pressure being applied to the valve member, thereby defining a flow area.   
     
     
         2 . The nozzle of  claim 1 , wherein the fuel pressure and the spring rate of the spring determine the flow area. 
     
     
         3 . The nozzle of  claim 1 , further comprising a spring compression adjustment mechanism configured to adjust a spring tension of the spring, thereby adjusting the predetermined fuel pressure required to move the valve member to the open position. 
     
     
         4 . The nozzle of  claim 1 , further comprising at least one shim, the at least one shim configured to adjust a spring tension of the spring to adjust the predetermined fuel pressure. 
     
     
         5 . The nozzle of  claim 1 , wherein the nozzle body further comprises a valve seat configured to receive the valve member when the valve member is in the closed position. 
     
     
         6 . The nozzle of  claim 1 , wherein the valve member further comprises a valve stem extending from the valve member, the guide stem being slidably engaged with a flexure spring positioned within the nozzle body to guide the movement of the valve member between the open and closed positions. 
     
     
         7 . The nozzle of  claim 1 , wherein the spring is a coil spring configured to exert a force against the valve member. 
     
     
         8 . The nozzle of  claim 1 , wherein the flow area is annular. 
     
     
         9 . The nozzle of  claim 8 , wherein the flow area is uniform. 
     
     
         10 . A nozzle, comprising:
 a nozzle body having an inlet to receive fuel, an outlet, and a passageway extending through the nozzle body from the inlet to the outlet;   a valve member positioned within the passageway, the valve member being movable between a closed position, in which the valve member substantially obstructs fuel flow through the outlet and an open position, in which the valve member permits fuel flow through the outlet; and   a return spring disposed within the nozzle body to bias the valve member toward the closed position,   wherein the valve member moves to the open position in response to a fuel pressure applied to the valve member overcoming a resisting force from the return spring, thereby defining a variable flow area through the outlet.   
     
     
         11 . The nozzle of  claim 10 , wherein the valve member and the outlet are profiled such that the flow area is precisely defined as a function of the movement of the valve member. 
     
     
         12 . The nozzle of  claim 10 , further comprising at least one spring shim configured to adjust a spring force of the return spring, thereby adjusting the fuel pressure required to move the valve member to the open position. 
     
     
         13 . The nozzle of  claim 10 , further comprising a valve seat configured to receive the valve member when the valve member is in the closed position. 
     
     
         14 . The nozzle of  claim 13 , wherein the valve member is sized and shaped to seal the outlet when the valve member is in the closed position. 
     
     
         15 . The nozzle of  claim 10 , further comprising a flexure spring configured to maintain annular alignment of the valve member within the nozzle body and with a valve seat. 
     
     
         16 . The nozzle of  claim 10 , further comprising at least one damping device configured to prevent oscillation of the valve member. 
     
     
         17 . The nozzle of  claim 16 , wherein the at least one damping device comprises at least one O-ring configured to provide damping through friction. 
     
     
         18 . The nozzle of  claim 10 , wherein the valve member comprises an upper portion and a lower portion, the upper portion being generally disk-shaped and having an annular seal surface, and the lower portion being a stem for axially guiding the upper portion. 
     
     
         19 . The nozzle of  claim 10 , wherein the return spring has a spring constant that increases the resisting force with displacement of the valve member from the closed position to the open position. 
     
     
         20 . The nozzle of  claim 10 , wherein the nozzle is configured to provide a flow turndown ratio of at least 12:1.