Development of a Piezoelectric Micro Engine Using Pulsed Catalytic Combustion

Open Access
Author:
Green, Darren Vincent
Graduate Program:
Mechanical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
November 21, 2008
Committee Members:
  • Domenic Adam Santavicca, Committee Chair
  • Kendra Sharp, Committee Chair
  • Jeffrey M Catchmark, Committee Member
  • Richard A Yetter, Committee Member
Keywords:
  • micro engine
  • piezoelectric
  • catalytic combustion
  • micro power
Abstract:
As electronic devices become smaller and smaller there is an increasing need to produce similarly small power devices to accompany them. Due to the limitations of traditional chemical batteries research is being conducted to develop new ways to produce power at the micro scale. These micro power devices, often referred to as micro engines, attempt to utilize the favorable energy density of hydrocarbon fuel to improve the size, weight, and recharging time offered by traditional chemical batteries. There are several approaches being researched. A few projects have attempted to scale down macro scale power devices, such as turbines and rotary engines, to produce micro scale power devices. Other projects have developed novel approaches to producing power on the micro scale. The research presented in this proposal falls into the second category. The general premise of the proposed micro engine is to use pulsed catalytic combustion to periodically deform a piezoelectric material and generate an electrical output. Initial experimental work focused on the use of pulsed catalytic combustion to produce periodic temperature fluctuations, which could be used to deform a piezoelectric material. The experimental work was then simulated using FLUENT to gain a better understanding of the flow, combustion, and heat transfer processes in the combustor. The numerical predictions were compared to the experimental measurements to validate the model. The experimental and modeling work led to an improved micro engine design. The new micro engine design consists of array of paired cantilever beams. One beam, a bi-layered beam, periodically deflects due to pulsed catalytic combustion. When the beam deflects it exerts a force on the second beam, a piezoelectric beam, causing it to bend and producing an electrical output. Experimental work using a single pair of cantilever beams demonstrated successful operation of the piezoelectric micro engine. In addition, the experimental work was used to characterize and evaluate the micro engine design. After a discussion of ways to optimize the micro engine and other design challenges, the overall feasibility of the micro engine design was assessed.