A Piezoelectrically Actuated Cryogenic Microvalve with Integrated Sensors.

Microvalve;MEMS;Piezoelectric Actuation;Cryogenic Cooling;Sensors;Electrical Engineering;Engineering;Electrical Engineering

Park, Jong MoonWise, Kensall D. ;

University of Michigan

关键词: Microvalve;    MEMS;    Piezoelectric Actuation;    Cryogenic Cooling;    Sensors;    Electrical Engineering;    Engineering;    Electrical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/62389/parkjong_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Future space missions require cooling of large optical structures and cryogenic storage systems.A distributed network of cooling elements, each including actively controlled valves, can provide location specific temperature control.This thesis presents piezoelectrically actuated microvalves for modulating refrigerant flow in a cryogenic cooling system.The first-generation valve consists of a micromachined die fabricated from silicon and glass wafers, a piezoelectric stack actuator, and Macor ceramic encapsulation, having overall dimensions of 1×1×1 cm3.The silicon valve seat is suspended by a crab-leg flexure formation and attached to the piezoelectric stack actuator, which moves in an out-of-plane motion against the glass substrate.To overcome modest displacement provided by piezoelectric actuation, a perimeter augmentation scheme for the valve seat has been implemented to increase flow area and consequently provide high flow modulation.The valve can modulate the flow from 980 mL/min with the valve fully open (0 V) to 0 mL/min with 60 V actuation voltage at a pressure difference of 55 kPa at room temperature.The operation of the valve has been validated at temperatures over 80-380 K, and at pressures up to 130 kPa.The valve has a response time of less than 1 msec and has an operation bandwidth up to 820 Hz.It is used in the Joule-Thomson self-cooling test with a micromachined recuperative heat exchanger, and a temperature decrease of as much as 42 K is presented.For the second-generation design, a similar architecture is used with integrated sensors for inlet pressure and temperature.Implementation of a membrane type suspension substantially decreased the dead volume inside the valve.At room temperature, a normally-open valve achieved gas flow modulation from 200 mL/min to 0 mL/min with 0 V to 40 V actuation.Sensors are strategically positioned at the upstream end of the valve so that the information can be used for closed-loop control.Sensitivities of 356 ppm/kPa for the piezoresistive pressure sensor and 0.29 %/K for the platinum resistance temperature detector (RTD) are reported.These valves are compatible with liquids, thus the liquid modulation, using the valve for drug delivery application, is briefly discussed.