Co-axial quill assembly for dual fuel common rail system

A method of supplying fuels to a fuel injector with a coaxial quill assembly that includes a block;

• a quill at least partially positioned in the block and defining a first fuel passage extending between a first fuel inlet and a first fuel outlet, and a second passage extending between a second fuel inlet and a second fuel outlet;
• an outer tube with one end extending into the block, and being fluidly connected the second fuel outlet of the quill;
• an inner tube positioned in the outer tube, and being fluidly connected the first fuel outlet of the quill;
• a first compression load adjuster attached to the block and operably coupled to adjust a compression load on the inner tube;
• and a second compression load adjuster attached to the block and operably coupled to adjust a compression load on the outer tube;
• the method comprising the steps of:
• moving a first fuel at a first pressure from a first common rail through the first fuel passage, through the inner tube and into a fuel injector;
• moving a second fuel at a second pressure from a second common rail through the second fuel passage, through a space between the outer tube and the inner tube and into the fuel injector;
• inhibiting leakage of the second fuel into the first fuel includes setting the first pressure higher than the second pressure;
• inhibiting leakage of the first fuel into the second fuel includes setting a compression load on the inner tube above a first predetermined threshold with the first compression load adjuster;
• and
• inhibiting leakage of the second fuel to atmosphere includes setting a compression load on the outer tube above a second predetermined threshold with the second compression load adjuster.

A dual fuel common rail fuel system comprising:

• a quill defining a first fuel passage extending between a first fuel inlet and a first fuel outlet, and a second passage extending between a second fuel inlet and a second fuel outlet;
• a fuel injector defining an outer conical seat concentrically surrounding an inner conical seat, and including an inner fuel inlet surrounded by the inner conical seat, and an outer fuel inlet positioned between the inner conical seat and the outer conical seat;
• an outer tube compressed between the quill and the fuel injector and fluidly connecting the second fuel outlet of the quill to the second fuel inlet of the fuel injector;
• an inner tube positioned in the outer tube and being compressed between the quill and the fuel injector, and fluidly connecting the first fuel outlet of the quill to the first fuel inlet of the fuel injector;
• a first compression load adjuster operably coupled to adjust a load of the inner tube on the first conical seat;
• and
• a second compression load adjuster operably coupled to adjust a load of the outer tube on the second conical seat.