Low Frequency Operation of the P3 Micro Heat Engine

2002 ◽  
Author(s):  
Scott A. Whalen ◽  
Michael R. Thompson ◽  
Cecilia D. Richards ◽  
David F. Bahr ◽  
Robert F. Richards
Keyword(s):  
Combustion Engine ◽  
Thermal Power ◽  
Electrical Power ◽  
Heat Engine ◽  
Low Frequency ◽  
Thermodynamic Cycle ◽  
Mechanical Power ◽  
Peak Voltage ◽  
Macro Scale ◽  
Micro Heat Engine

The development and low frequency testing of a micro heat engine is presented. Production of electrical power by a dynamic micro heat engine is demonstrated. The prototype micro heat engine is an external combustion engine in which thermal power is converted to mechanical power through a novel thermodynamic cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. This design is well suited to photolithography-based batch fabrication methods and is unlike any conventionally manufactured macro-scale engine. A peak-to-peak voltage of .84 volts, and power output of 1.5 microwatts have been realized at operating speeds of 10 Hz. Measurements are also presented for the engine operating at resonant conditions. Cycle speeds up to 240 Hz have been obtained, with peak-to-peak voltages of 70 millivolts.

A Micro Heat Engine for MEMS Power (Keynote Paper)

2002 ◽  
Author(s):  
C. D. Richards ◽  
D. F. Bahr ◽  
R. F. Richards
Keyword(s):  
Combustion Engine ◽  
Thermal Power ◽  
Electrical Power ◽  
Heat Engine ◽  
Thermodynamic Cycle ◽  
Mechanical Power ◽  
Batch Fabrication ◽  
Macro Scale ◽  
Micro Heat Engine ◽  
External Combustion

Progress in the development of a micro heat engine is presented. The prototype micro heat engine is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. The design, well suited to photolithography-based batch fabrication methods, is unlike any conventionally manufactured macro-scale engine. In this paper, the design, fabrication and preliminary testing of a working prototype are discussed. The operation of the engine and its key component, the piezoelectric membrane generator is presented. For the first time, the production of electrical power by a dynamic micro heat engine is demonstrated.

Design of a Micro Heat Engine

2000 ◽  
Author(s):  
C. Xu ◽  
J. Hall ◽  
C. Richards ◽  
D. Bahr ◽  
R. Richards
Keyword(s):  
Combustion Engine ◽  
Thermal Power ◽  
Electrical Power ◽  
Heat Engine ◽  
Thermodynamic Cycle ◽  
Mechanical Power ◽  
Carnot Cycle ◽  
Mems Fabrication ◽  
Micro Heat Engine ◽  
External Combustion

Abstract The design for a totally new class of heat engine, a micro heat engine, which takes advantage of thermophysical phenomena unique to small scales, is introduced. The proposed engine is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle which approaches the ideal vapor Carnot cycle. Mechanical power is converted into electrical power through the use of a piezoelectric generator. The generator, which takes the form of a flexible membrane, can be readily manufactured using MEMS fabrication techniques but still delivers high conversion efficiency. This approach eliminates the requirement to manufacture complex micromachines such as rotary compressors and turbines, resulting in a very simple but highly efficient device.

The P3 Micro Power Generation System

2001 ◽  
Author(s):  
C. Richards ◽  
D. Bahr ◽  
C.-G. Xu ◽  
R. Richards
Keyword(s):  
Power Generation ◽  
Combustion Engine ◽  
Thermal Power ◽  
Electrical Power ◽  
Heat Engine ◽  
Mechanical Power ◽  
Carnot Cycle ◽  
Generation System ◽  
Power Generation System ◽  
Micro Heat Engine

Abstract Work toward the development of a new MEMS power generation system, the P3 micro heat engine, is presented. The P3 micro heat engine is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle that approaches the ideal vapor Carnot cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. A numerical model of the engine, SIMP3, is introduced. The model is used, first to illustrate the micro heat engine’s operation, and then to explore the optimization of the engine. The major parameters controlling the performance of the P3 micro engine are discussed.

Characterization of a Piezoelectric Membrane for MEMS Power

2001 ◽  
Author(s):  
K. Bruce ◽  
R. Richards ◽  
D. Bahr ◽  
C. Richards
Keyword(s):  
Thin Film ◽  
Power System ◽  
Combustion Engine ◽  
Thermal Power ◽  
Operating Conditions ◽  
Mechanical Power ◽  
Central Component ◽  
Carnot Cycle ◽  
Modular Architecture ◽  
Micro Power

Abstract Work toward the development of a thin-film piezoelectric membrane generator is presented. The membrane generator is the central component of a new MEMS power generation system, the P3 micro power system. The P3 micro power system is based on a two-dimensional, modular architecture, in which the individual generic modules or unit cells each have all the functions of an engine integrated. Each unit cell is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle that approaches the ideal vapor Carnot cycle. Mechanical power is converted into electrical power through the use of a thin-film piezoelectric membrane generator. This paper introduces the concept of the thin-film piezoelectric membrane generator, and describes its design and fabrication. Results of a study to characterize the performance of the piezoelectric membrane generator under expected operating conditions are presented. Current prototypes of the membrane generator are shown to be capable of producing a peak power of 0.1 milliWatts at a voltage of 0.5 Volts.

PZT and Electrode Enhancements of Mems Based Micro Heat Engine for Power Generation

2002 ◽  
Vol 730 ◽  
Author(s):  
A.L. Olson ◽  
L.M. Eakins ◽  
B.W. Olson ◽  
D.F. Bahr ◽  
C.D. Richards ◽  
...  
Keyword(s):  
Bottom Electrode ◽  
Mechanical Energy ◽  
Electrical Power ◽  
Heat Engine ◽  
Mems Devices ◽  
Stress Concentrations ◽  
Process Yield ◽  
Micro Heat Engine ◽  
Reducing Stress ◽  
And Diffusion

AbstractThe P3 Micro Heat Engine relies on a thin film PZT based transducer to convert mechanical energy into usable electrical power. In an effort to increase process yield for these were used on sputtered Ti/Pt bottom electrodes to compare roughness, grain size, and diffusion for annealing temperatures between 550 and 700 °C. For an optimized bottom electrode, process yield for various sized top electrodes were then studied for PZT thickness between 0.54 and 1.62 for reducing stress concentrations. Two PZT etching geometries on 2.3 μm thick Si/SiO2 membranes, with 1.5-3.5 mm side-lengths, were examined and one was used to increase the strain at failure by at least 40%. Integrating improvements in process yield and strain at failure, single PZT based MEMS devices capable of generating power of up to 1 mW and in excess of 2 volts have been demonstrated operating at frequencies between 300 and 1,100 Hz.

The Mechanical Behavior of a Micromachined PZT Membrane

2003 ◽  
Author(s):  
I. Demir ◽  
R. F. Richards ◽  
D. F. Bahr ◽  
C. D. Richards
Keyword(s):  
Thin Film ◽  
Mechanical Behavior ◽  
Material Properties ◽  
Energy Minimization ◽  
Variational Approach ◽  
Piezoelectric Ceramic ◽  
Electrical Power ◽  
Heat Engine ◽  
Silicon Membrane ◽  
Micro Heat Engine

The mechanical behavior of a micromachined PZT membrane for power applications is investigated. The membrane is a bulk-micromachined silicon membrane that supports a thin film of piezoelectric ceramic (PZT) sandwiched between platinum and gold electrodes. The membrane undergoes large periodic deflections to convert mechanical power to electrical power in a micro heat engine. An analysis using a variational approach is developed to find an approximate closed from solution based on energy minimization. Experiments were conducted to obtain material properties, residual stresses, and pressure deflection relationships. The modeled results compare well to the experimental results.

Development of Scaling Model for a MEMS-Based Micro Heat Engine

2010 ◽  
Author(s):  
H. Bardaweel ◽  
B. S. Preetham ◽  
R. Richards ◽  
C. Richards ◽  
M. Anderson
Keyword(s):  
Combustion Engine ◽  
Heat Engine ◽  
Working Fluid ◽  
Thin Membranes ◽  
Micro Heat Engine ◽  
Heat Of Evaporation ◽  
Major Factors ◽  
Engine Components ◽  
External Combustion ◽  
Thermal Physical Properties

In this work we investigate issues related to scaling of a MEMS-based resonant heat engine. The engine is an external combustion engine made of a cavity encapsulated between two thin membranes. The cavity is filled with saturated liquid-vapor mixture working fluid. We use both model and experiment to investigate scaling of the MEMS-based resonant heat engine. The results suggest that the performance of the engine is determined by three major factors: geometry of the engine, speed of operation, and thermal physical properties of engine components. Larger engine volumes, working fluids with higher latent heat of evaporation, slower engine speeds, and compliant expander structures are shown to be desirable.

A Micro Heat Engine Executing an Internal Carnot Cycle

2008 ◽  
Author(s):  
Eli Lurie ◽  
Abraham Kribus
Keyword(s):  
Strong Dependence ◽  
Heat Engine ◽  
Thermodynamic Cycle ◽  
Maximum Power ◽  
Working Fluid ◽  
Carnot Cycle ◽  
Heating And Cooling ◽  
Engine Design ◽  
Power Point ◽  
Micro Heat Engine

A micro heat engine, based on a cavity filled with a stationary working fluid under liquid-vapor saturation conditions and encapsulated by two membranes, is described and analyzed. This engine design is easy to produce using MEMS technologies and is operated with external heating and cooling. The motion of the membranes is controlled such that the internal pressure and temperature are constant during the heat addition and removal processes, and thus the fluid executes a true internal Carnot cycle. A model of this Saturation Phase-change Internal Carnot Engine (SPICE) was developed including thermodynamic, mechanical and heat transfer aspects. The efficiency and maximum power of the engine are derived. The maximum power point is fixed in a three-parameter space, and operation at this point leads to maximum power density that scales with the inverse square of the engine dimension. Inclusion of the finite heat capacity of the engine wall leads to a strong dependence of performance on engine frequency, and the existence of an optimal frequency. Effects of transient reverse heat flow, and ‘parasitic heat’ that does not participate in the thermodynamic cycle are observed.

On the Thermodynamic Cycle of a MEMS-Based External Combustion Resonant Engine

2010 ◽  
Author(s):  
H. Bardaweel ◽  
R. Richards ◽  
C. Richards ◽  
M. Anderson
Keyword(s):  
Heat Transfer ◽  
Heat Engine ◽  
Fluid Motion ◽  
Thermodynamic Cycle ◽  
Working Fluid ◽  
Thermal Mass ◽  
Compression Pressure ◽  
Heat Addition ◽  
Irreversible Effects ◽  
Micro Heat Engine

In this work we investigate the thermodynamic cycle of a resonant, MEMS-based, micro heat engine. The micro heat engine is made of a cavity encapsulated between two membranes. The cavity is filled with saturated liquid-vapor mixture working fluid. Heat is added/rejected from the engine at a frequency equal to its resonant frequency. Both pressure-volume and temperature-entropy diagrams of the resonant engine are used to investigate the thermodynamic cycle of the resonant micro heat engine. The results show that the thermodynamic cycle of the engine consists of four major processes: heat addition, expansion, heat rejection, and compression. pressure-volume and temperature-entropy diagrams are bounded by two constant temperature processes and two constant volume processes. The temperature-entropy and pressure-volume diagrams show deviations from this ideal description and are rounded due to the presence of irreversible effects. Major sources of irreversibility in the engine are heat transfer over finite temperature differences during heat addition and rejection, heat transfer into and out of engine thermal mass and viscous losses due to liquid working fluid motion. The measured second law efficiency of the micro heat engine is about 16%.

scholarly journals Changes in electromyographic activity, mechanical power, and relaxation rates following inspiratory ribcage muscle fatigue

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Antonio Sarmento ◽  
Guilherme Fregonezi ◽  
Maria Lira ◽  
Layana Marques ◽  
Francesca Pennati ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Low Frequency ◽  
Mechanical Power ◽  
Electromyographic Activity ◽  
Median Frequency ◽  
Relaxation Rates ◽  
Shortening Velocity ◽  
Inspiratory Muscles ◽  
Underlying Mechanisms

AbstractMuscle fatigue is a complex phenomenon enclosing various mechanisms. Despite technological advances, these mechanisms are still not fully understood in vivo. Here, simultaneous measurements of pressure, volume, and ribcage inspiratory muscle activity were performed non-invasively during fatigue (inspiratory threshold valve set at 70% of maximal inspiratory pressure) and recovery to verify if inspiratory ribcage muscle fatigue (1) leads to slowing of contraction and relaxation properties of ribcage muscles and (2) alters median frequency and high-to-low frequency ratio (H/L). During the fatigue protocol, sternocleidomastoid showed the fastest decrease in median frequency and slowest decrease in H/L. Fatigue was also characterized by a reduction in the relative power of the high-frequency and increase of the low-frequency. During recovery, changes in mechanical power were due to changes in shortening velocity with long-lasting reduction in pressure generation, and slowing of relaxation [i.e., tau (τ), half-relaxation time (½RT), and maximum relaxation rate (MRR)] was observed with no significant changes in contractile properties. Recovery of median frequency was faster than H/L, and relaxation rates correlated with shortening velocity and mechanical power of inspiratory ribcage muscles; however, with different time courses. Time constant of the inspiratory ribcage muscles during fatigue and recovery is not uniform (i.e., different inspiratory muscles may have different underlying mechanisms of fatigue), and MRR, ½RT, and τ are not only useful predictors of inspiratory ribcage muscle recovery but may also share common underlying mechanisms with shortening velocity.

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