| 摘要 |
<p>A system for delivering controlled quantities of a stream of fluid to an application zone includes a positive displacement pump (100) comprising a piston housing (111) with an interior cylindrical wall (115). A pumping chamber (116) lies adjacent a closed end of the pump cylinder. A reciprocating and rotating piston (118) in the cylinder draws fluid into the chamber (116) and expels the fluid therefrom. A barrier fluid inlet (122) adjacent the piston (118) enables barrier fluid to be delivered to the cylinder at a pressure greater than the maximum fluid pressure in the pumping chamber (116) to preclude migration of pumping fluid along the piston to the opposite end of the cylinder.</p> |
