| 摘要 |
<p>In the present method and apparatus, cryogenic liquid and vapor are pumped from a storage tank and the proportion of liquid and vapor is controlled so as to influence flow rate through the apparatus. In an induction stroke, the piston of a reciprocating pump is retracted and cryogenic fluid is drawn from the storage tank into a piston chamber associated with the piston. Flow rate is controlled through the apparatus by controlling the proportion of liquid and vapor supplied to the pump during the induction stroke by supplying substantially only vapor to the pump during a portion of the induction stroke. In a compression stroke, the pump compresses and condenses vapor into liquid and then compresses any liquid within the piston chamber; compressed cryogenic fluid is ultimately discharged from the pump. The apparatus preferably includes a pump with a liquid supply line connecting a pump inlet to a storage tank, a vapor supply line connecting an ullage space with a pump inlet, an automatically actuated valve that opens and closes to control the flow of vapor to the pump inlet, and a controller that controls the valve to achieve a desired flow rate.</p> |
