High pressure pump system for supplying a cryogenic fluid from a storage tank

A method of operating a cryogenic system for pumping a fuel to an engine and controlling mass flow rate, said system comprising a pump operable to pump said fuel, which comprises a cryogenic liquid or a mixture of said cryogenic liquid and vapor, whereby when said system supplies said vapor and/or cryogenic liquid to said pump from a storage tank, said method comprising:

• (a) selecting a first operating mode in which said cryogenic liquid is supplied to said pump to substantially fill a compression chamber with liquid to achieve a high mass flow rate;
• (b) selecting a second operating mode to achieve a mass flow rate lower than said first operating mode by selectively supplying said liquid and said vapor simultaneously to said pump wherein the vapor fraction is higher for said second operating mode compared to the vapor fraction for said first operating mode;
• and
• (c) providing a steady supply of high pressure fuel to said engine by delivering said fuel from said pump to an accumulator vessel and selecting said operating mode to control mass flow rate to maintain pressure within a predetermined range within said accumulator vessel.

A method of operating a cryogenic system for pumping a cryogenic fluid, said system comprising a multi-stage pump that has at least three chambers for compressing said cryogenic fluid wherein a first chamber and a second chamber each have a volume that is larger than a third chamber, said method comprising:

• (a) selectively supplying a cryogenic liquid or a mixture of cryogenic liquid and vapor to said pump such that cryogenic fluid flows through an inlet into said first chamber;
• (b) compressing and condensing cryogenic vapor and compressing cryogenic liquid within said first chamber and transferring cryogenic fluid from said first chamber to said second chamber;
• (c) compressing cryogenic fluid within said second chamber and transferring said cryogenic fluid from said second chamber to said third chamber until said third chamber is filled, and then transferring cryogenic fluid remaining within said second chamber to said first chamber;
• and
• (d) compressing cryogenic fluid within said third chamber and discharging compressed cryogenic fluid from said third chamber through an outlet port.

A method of operating a reciprocating pump for pumping a fluid from a cryogenic storage tank, said pump comprising at least three chambers for compressing said fluid, said chambers divided by a reciprocating piston assembly and said method comprising:

• (a) during a retraction stroke, retracting a piston, and thereby,
• increasing the volume of a first chamber of said pump and selectively introducing into said first chamber, a cryogenic liquid or a mixture of cryogenic vapor and liquid supplied from said storage tank;
• decreasing the volume of a second chamber of said pump, compressing cryogenic fluid within said second chamber, transferring cryogenic fluid from said second chamber into a third chamber until said third chamber is filled, and then returning cryogenic fluid from said second chamber to said first chamber until said retraction stroke is completed;
• increasing the volume of a third chamber of said pump and receiving cryogenic fluid from said second chamber into said third chamber until said third chamber is full;
• and
• (b) during an extension stroke, extending said piston, and thereby,
• decreasing the volume of said first chamber, compressing cryogenic fluid within said first chamber, and transferring cryogenic fluid within said first chamber to said second chamber;
• increasing the volume of said second chamber and drawing fluid into said second chamber from said first chamber;
• decreasing the volume of said third chamber, compressing fluid within said third chamber, and ejecting cryogenic fluid through an outlet from said third chamber.

A method of operating a reciprocating pump for pumping a cryogenic fluid from a sump of a cryogenic storage tank, said pump comprising at least two chambers divided by a reciprocating piston assembly, said method comprising:

• (a) during a retraction stroke,
• increasing the volume of a first compression chamber of said pump and introducing into said first compression chamber a cryogenic fluid supplied from said storage tank;
• decreasing the volume of a second compression chamber of said pump and thereby compressing fluid within said second compression chamber and ejecting compressed fluid from said second compression chamber and out of said pump;
• and
• (b) during an extension stroke,
• decreasing the volume of said first compression chamber and transferring fluid within said first compression chamber to said second compression chamber;
• increasing the volume of said second compression chamber and drawing cryogenic fluid into said second compression chamber from said first compression chamber, wherein the volume of said second compression chamber at the end of said extension stroke is less than the volume of said first compression chamber at the end of said retraction stroke so that when the volume of said second compression chamber is filled by fluid flowing into said second compression chamber from said first compression chamber, to accommodate the transfer into said second chamber of fluid remaining within said first chamber, compressed cryogenic fluid is ejected from said second compression chamber and out of said pump.