Pumps, positive-displacement flow variations

A simple positive-displacement sampler system is shown in Figure 3. The basic system contains a battery and motor connected to a positive-displacement pump mechanism and provides an efficient means for moving air through the sampler. In order to provide feedback flow control the system must be expanded to include the means to monitor air flow through the pump to compensate for flow variations. 

Mixed acid and glycerine are stored externally in separate tanks and are transferred by means of centrifugal and gear pumps to small feed tanks. From the feed tanks the reactants are sent to the nitrator by means of two positive displacement pumps driven by the same electric motor. Two speed variators allow change in the total flow rate as well as the ratio between acid and glycerine. The glycerine feed pipe in the nitrator, fitted with a multi-nozzle distributing head is... 

There are many variations in the design of the screw-type positive displacement rotary pump. The primary differences consist of the number of intermeshing screws involved, the pitch of the screws, and the general direction of fluid flow, "hvo designs Include a two-screw, low-pitch double-flow pump, and a three-screw, high-pitch double-flow pump. 

Valve-Less Rectification Pumps, Fig. 31 An example of a planar micropump using the principle from Fig. 29. The cavities are made photochemically in a thin plate (above), the driving nozzles are in alternating positions on both sides of the channel. The alternating flow in them is generated by volume variations of an electrostrictive gel in displacement chambers... 

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