초록 ▼

A reciprocating cryogenic pump, suitable for medium and high pressures having very low net positive suction head (NPSH) requirements. The pump comprises a cylinder having both liquid inlets and vapor outlets, and two interacting pistons, each piston reciprocably movable within the cylinder, and each

A reciprocating cryogenic pump, suitable for medium and high pressures having very low net positive suction head (NPSH) requirements. The pump comprises a cylinder having both liquid inlets and vapor outlets, and two interacting pistons, each piston reciprocably movable within the cylinder, and each piston having flow conduits there through generally co-axial with the piston and with the cylinder. The conduit of one piston preferentially connects to the liquid inlets and the conduit of the other piston preferentially connects to the vapor outlets, which are at a higher elevation than the liquid inlets. Both conduits are selectively and mechanically opened to the pumping chamber by the reciprocating motion, and the pump is oriented to allow liquid flowing into the pumping chamber by the natural tendency of liquid to flow downwards and residual vapor to leave the pumping chamber by the natural tendency of vapor to flow upwards, an act that in encouraged by the conduit connecting to the vapor outlets being opened before the conduit connecting to the liquid inlets. One use of this pump is for any on-board, mobile (truck, rail or ship), LNG fuel systems for Diesel engines.

대표청구항 ▼

[ I claim:] [1.] In a station for pumping a low NPSH cryogenic liquid to about medium or high pressures, the station comprising:insulated storage tank means for holding said cryogenic liquid to be pumped and, above said liquid, vapor holding means for the respective vapor phase of said liquid in the

[ I claim:] [1.] In a station for pumping a low NPSH cryogenic liquid to about medium or high pressures, the station comprising:insulated storage tank means for holding said cryogenic liquid to be pumped and, above said liquid, vapor holding means for the respective vapor phase of said liquid in the ullage volume of said tank means,a reciprocating pump mounted to said tank in an inclined or vertical position having,cylinder means,piston means reciprocally movable within said cylinder means,liquid outlet valve means mounted in a closure attached to the discharge end of said cylinder means,combination valve means for liquid inlet and vapor outlet into and out of said cylinder,piston rod means reciprocally movable generally along the axis of said cylinder means in a direction toward said outlet valve means and in a reciprocal direction causing a compression stroke and then an intake stroke by said piston means to which said rod means is linked, said rod means and said piston means loosely connected so that they form said combination valve means,said cylinder means, said outlet valve means and said closure, said combination valve means and the compression face of said reciprocally moving piston means defining a pumping chamber,said cylinder means, said rod means, said combination valve means, and the intake face of said reciprocally moving piston defining part of an annular intake chamber,conduit or conduits having one end in communication with said liquid in said storage tank means and the other end in communication with said intake chamber or extensions thereof, said conduit or conduits located generally above that portion of said intake chamber that said piston traverses during said intake stroke,drive means attached to the upper end of said rod means for providing a reciprocating motion causing said intake and said compression strokes by said piston means,pressure seal means located between said cylinder means and said piston means so as to reduce leakage between said compression chamber and said intake chamber during said compression stroke,said combination valve means operatively associated with said rod means and said piston means in a lost motion type arrangement, whereby said combination valve means is mechanically caused to open during said intake stroke and to close during said compression stroke,said combination valve means and said intake chamber located above said compression chamber so that when said combination valve means is open, either said liquid can flow downwardly from said intake chamber into said compression chamber, or said vapor can flow upwards from said compression chamber into said intake chamber, all as influenced by gravity or the changes in relative size of said compression and intake chambers andsaid outlet valve means being a check valve type responsive to the flow therethrough of said liquid caused by said compression stroke or by the lack of flow caused by said intake stroke;the improvement comprising:said conduit or conduits consisting of first conduit or conduits and second conduit or conduits, the ends of said first conduit or conduits in communication with said storage tank means at a higher elevation than the ends of said second conduit or conduits,whereby during said intake or compression strokes, said vapor formed in said pump collects in said intake chamber and returns to said ullage volume of said tank means by said first conduit or conduits and said liquid tends to flow into said intake chamber by said second conduit or conduits, thereby the flow of said vapor leaving tending to not impede the flow of said liquid entering, said vapor resulting from said liquid vaporizing due to contact with portions of said pumping chamber that had been warmed by friction of said seals means, or caused by said liquid that had been warmed by the heat of compression but not discharged from said pumping chamber and upon being depressurized during said intake stroke, or caused by heat incursion, or caused by any other reason, thereby reducing the volumetric efficiency of said pump,and whereby any of said vapor, produced during said compression stroke by leakage of said seal means of said liquid thereby passing from said compression chamber to said intake chamber, then returns to said tank means by said first conduit or conduits, thereby not disturbing said liquid about to enter said intake chamber via said second conduit or conduits, said leakage thereby not reducing the volumetric efficiency of said pump.