Fuel injector with an optimized metering device

A metering valve comprising:

• a bushing having terminus first and second edges;
• a hollow elongate valve member slidably disposed within said bushing along an axial direction of said valve member, said valve member having opposing open and closed ends and a flow metering valve head located at said closed end, said valve member further including at least one transverse bore formed therethrough adjacent said closed end,
• wherein said valve head includes a shoulder sized so as to be selectively engageable said terminus first end edge of said bushing, and a radially inwardly tapering exterior diameter in the axial direction away from said shoulder and towards said open end,
• wherein an annular volume is defined between an interior of said bushing and an exterior of said valve member, a first axial end of said annular volume being selectively closed by engagement between said shoulder and said first end edge of said bushing and a second axial end of said annular volume opposite said valve head being substantially closed, an interior of said valve member being in communication with said annular volume through said at least one transverse bore,
• wherein said radially inwardly tapering exterior diameter of said valve head defines an annular flow opening that increases in area as said shoulder moves away from engagement with said first end edge of said bushing, the extent of movement of said shoulder away from engagement with said first end edge of said bushing being selectively limited such that the change in area of said annular flow opening is limited.

A fuel injector comprising:

• an injector body including a fuel inlet and first and second fuel outlet paths, a portion of the admitted fuel leaving said injector body through said first fuel outlet path;
• a metering valve located in said injector body and comprising:
• a bushing having first and second end edges;
• a hollow elongate valve member slidably disposed within said bushing along an axial direction of said valve member, said valve member having opposing open and closed ends and a flow metering valve head located at said closed end, said valve member further including at least one transverse bore formed therethrough adjacent said closed end, wherein said valve head includes a shoulder sized so as to be selectively engageable with said first end edge of said bushing, and a radially inwardly tapering exterior diameter in the axial direction away from said shoulder,
• wherein an annular volume is defined between an interior of said bushing and an exterior of said valve member, a first axial end of said annular volume being selectively closed by engagement between said shoulder and said first end edge of said bushing and a second axial end of said annular volume opposite said valve head being substantially closed, an interior of said valve member being in communication with said annular volume through said at least one transverse bore,
• wherein said radially inwardly tapering exterior diameter of said valve head defines an annular flow opening that increases in area as said shoulder moves away from engagement with said first end edge of said bushing, the extent of movement of said shoulder away from engagement with said first end edge of said bushing being limited;
• wherein said second fuel outlet path is defined by said valve member having said open end thereof in communication with said interior of said injector body, said annular volume between said bushing and said valve member, and said annular flow opening selectively provided between said first end edge of said bushing and said valve head.

In a turbomachine combustion chamber including a plurality of fuel injectors constructed and arranged to introduce fuel into the combustion chamber, a method for adjusting a fuel flow from each fuel injector into the combustion chamber so as to conform with a desired relationship between fuel pressure and fuel flow rate, the method comprising:

• providing a metering valve in each fuel injector, each metering valve being constructed and arranged to present a fuel flow opening through which fuel can pass through the metering valve, the area of the fuel flow opening varying in proportion to a fuel pressure exerted on the metering valve between a first fuel pressure at which the metering valve is actuated and a second fuel pressure greater than the first fuel pressure, wherein at fuel pressures above the second fuel pressure, the area of the fuel flow opening area remains constant;
• identifying a fuel pressure at which a desired fuel flow rate out of the fuel injector occurs;
• and
• limiting the mechanical operation of the metering valve so that the second fuel pressure is made equal to the fuel pressure at which the desired fuel flow rate occurs, such the fuel flow opening area remains constant at fuel pressures above the fuel pressure at which the desired fuel flow rate occurs.

A metering valve comprising:

• a bushing having terminus first and second edges;
• an elongate valve member slidably disposed within said bushing along an axial direction of said valve member, said valve member having opposing first and second ends and a flow metering valve head located at said second end,
• wherein said valve head includes a shoulder sized so as to be selectively engageable with said terminus first end edge of said bushing, and a radially inwardly tapering exterior diameter in the axial direction away from said shoulder and towards said first end of said valve member,
• wherein an annular volume is defined between an interior of said bushing and an exterior of said valve member, an axial end of said annular volume being selectively closed by engagement between said shoulder and said first end edge of said bushing, said annular volume communicating with a fluid inlet to receive a fluid to be metered by the selective engagement between said shoulder and said first end edge of said bushing,
• wherein said radially inwardly tapering exterior diameter of said valve head defines an annular flow opening that increases in area as said shoulder moves away from engagement with said first end edge of said bushing, the extent of movement of said shoulder away from engagement with said first end edge of said bushing being selectively limited such that the change in area of said annular flow opening is limited.