Pump

Abstract

A fluid pump comprising a flow channel containing an fluid inlet and a fluid outlet and bounded by two side walls, a substantially planar flap positioned inside the flow channel, and an actuator capable of transmitting an oscillating force or torque to the flap, where the side walls extend from the inlet to the outlet and are substantially planar and parallel to the flap and extend beyond the downstream end of the flap towards the outlet by a distance such that l d ≧l f /2, where l f is the length of the flap, where the side wall separation, h, length, l w , and width, w w , satisfy the relationships: l w > h and w w >h, whereby in use, the actuator drives oscillatory motion of the flap in a direction substantially perpendicular to the side walls with motion of the flap having larger amplitude near the outlet than near the inlet.

1 . A fluid pump comprising:
 a flow channel containing an fluid inlet and a fluid outlet and bounded by two side walls,   a substantially planar flap positioned inside the flow channel, and   an actuator capable of transmitting an oscillating force or torque to the flap,   where the side walls extend from the inlet to the outlet and are substantially planar and parallel to the flap and extend beyond the downstream and of the flap towards the outlet by a distance such that l d ≧l f /2, where l f  is the length of the flap,   where the side wall separation, h, length l w , and width, w w , satisfy the relationships: l w >h and w w >h,   whereby in use, the actuator drives oscillatory motion of the flap in a direction substantially perpendicular to the side walls with motion of the flap having larger amplitude near the outlet than near the inlet.   
     
     
         2 . A pump according to  claim 1 , where the region of flow channel between the flap and the outlet is substantially unobstructed. 
     
     
         3 . A pump according to  claim 1 , wherein the flap length l f  satisfies the condition l f >2h. 
     
     
         4 . A pump according to  claim 1 , where the side walls extend beyond the downstream end of the flap towards the outlet by a distance l d  such that l d >2 h . 
     
     
         5 . A pump according to  claim 1 , where the where the flap width, w f , satisfies the condition w f >2h. 
     
     
         6 . A pump according to  claim 1 , where the flap and flow channel have sector annular forms. 
     
     
         7 . A pump according to  claim 1 , where the flow channel is also bounded by one or more edge walls, where the edge walls are perpendicular to the side walls and parallel to the flow direction. 
     
     
         8 . A pump according to  claim 1 , where the flap and flow channel have full annular forms. 
     
     
         9 . A pump according to  claim 1 , where motion of the flap causes creation and shedding of vortices into the fluid being pumped, with interaction of the shed vortices with the side walls, with each other and with the flap creating a pressure rise downstream of the flap. 
     
     
         10 . A pump according to  claim 1 , where the flap has an aerodynamic or aerofoil shape or a thin trailing edge. 
     
     
         11 . A pump according to  claim 1 , where the flap has substantially uniform cross-section perpendicular to the width direction. 
     
     
         12 . A pump according to  claim 1 , where a piezoelectric or magnetostrictive bending actuator is incorporated into or mounted on the flap. 
     
     
         13 . A pump according to  claim 1 , where the flap is driven by a remote actuator using a mechanical connection or a hydraulic or pneumatic drive. 
     
     
         14 . A pump according to  claim 1 , where the flap is driven by electrostatic or magnetic forces. 
     
     
         15 . A pump according to  claim 1 , where the flow channel inlet is divided into two regions to combine two fluid inlet streams and, in use, the motion of the flap generates vortices causing the two inlet fluid streams to be pumped and mixed downstream of the flap. 
     
     
         16 . A pump according to  claim 1 , where a temperature difference is applied between the side walls and inlet fluid stream, such that in use, the motion of the flap generates vortices causing the inlet fluid stream to be pumped and to exchange heat with one or both side walls. 
     
     
         17 . A pump according to  claim 1 , where the motion of the flap is driven at ultrasonic frequencies (>20 kHz). 
     
     
         18 . A pump according to  claim 1 , where the motion of the flap is driven at low frequencies (<400 Hz). 
     
     
         19 . A pump according to  claim 1 , where maximum peak-to-peak displacement of the flap, A, is between 10% and 70% of the side wall separation, h. 
     
     
         20 . A pump according to  claim 1 , where the oscillation frequency, f, is chosen to give a Strouhal number, St=f A/U between 0.1 and 0.5, where U is the average fluid flow speed in the flow channel. 
     
     
         21 . A pump according  claim 1 , where the amplitude of flap motion is amplified by mechanical resonance of the flap. 
     
     
         22 . A pump according to  claim 1 , where the flap is clamped at the edge near the inlet. 
     
     
         23 . A pump according to  claim 1 , where the flap oscillates with fixed centre of mass and is supported by two pivot supports at nodal locations or is supported by a flexible vibration isolating support. 
     
     
         24 . A pump according to  claim 1 , where an electromechanical actuator mounted on the flap is provided with electrical connections by using flexible support wires or a flexible circuit acting as a vibration isolating support. 
     
     
         25 . A pump according to  claim 1 , where the flap has flexible construction such that fluid loading causes non-sinusoidal motion. 
     
     
         26 . One or more pumps according to  claim 1 , including a total of two or more flaps, where the flaps move with out of phase motion to avoid noise and vibration. 
     
     
         27 . A pump according to  claim 1 , where the flap includes a folded sheet structure with a welded or adhesive bonded seam. 
     
     
         28 . An array of pumps according to  claim 1 . 
     
     
         29 . A heat exchanger containing an array of devices as  claim 1 . 
     
     
         30 . An array of devices according to  claim 1  where a single actuator drives multiple taps. 
     
     
         31 . An array of devices according to  claim 1  where multiple flaps are fabricated from a single sheet. 
     
     
         32 . An array of devices according to  claim 1  where multiple flaps are supported in a common support frame.