abstract
The heaters currently produced by Bosch Thermotechnology rely on valves based on solenoid actuators for regulating the fuel flow. Each actuator is characterized by parameters that ensure the correct functioning of the devices, namely with regard to gas flows and pressure drops through the valves. Bosch Thermotechnology has recently expressed an interest in exploring the feasibility of replacing solenoid actuators with piezoelectric actuators. Its possible interest lies in the need to replace the main raw material of the solenoid, copper, due to its price and variability, dependence on the eastern markets, such as China, and instability of the chemical composition of Cu, which causes fluctuations in the solenoid performance. In the present project we propose solutions based on piezoelectric actuators, for two types of valves in use in Bosch water heaters, the macrovalve and the microvalve. These valves are characterised by XXX For the macrovalve a solution based on a disc type bimorphic piezoelectric actuator is proposed and for the microvalve a bender type bimorph piezoelectric actuator. The proposed solution for the microvalve is detailed here, and two benders of different dimensions are considered. The piezoelectric performances of the benders are characterized in terms of their responses to voltage variations, i.e. displacement curves as a function of the electric field and respective hysteretic behavior. In order to evaluate the impact of the actuator operation on gas flow conditions, a prototype of a microvalve was designed and constructed by additive manufacturing using acrylonitrile-butadiene-styrene (ABS) thermoplastic and the small bender was coupled to the prototype. The characterization of the performance of this prototype through the observed relations between applied voltages, bender displacements, gas pressure drops through the microvalve and associated flow rates allowed to identify conditions of operation of the piezoelectric actuator similar to those of the solenoid actuator microvalve. It has been observed that activations of the bimorph piezoelectric actuator of the bender type with applied voltages close to 35 V ensure pressure drops (and flow rates) similar to those observed in the micro-valve with solenoid actuator. The optimization of the implementation of the piezoelectric actuation in valves of Bosch Thermotechnology, namely in relation to the electrical voltages and cost, may pass through resizing / redesigning some of the valves. In conclusion, the technical feasibility of replacing a solenoid actuator with a bimorph bender piezoelectric actuator was demonstrated in one of Bosch Thermotechnology's current micro-valves, without resorting to a new design of the microvalve.
authors
Tiago José Fontoura Ribeiro
supervisors
Maria Elisabete Jorge Vieira Da Costa , Paula Maria Lousada Silveirinha Vilarinho
Groups