Investigation of a MEMS-Based Boiler and Free Piston Expander for Energy Harvesting

2012 ◽  
Author(s):  
C. Champagne ◽  
L. Weiss
Keyword(s):  
Dynamic Testing ◽  
Waste Heat ◽  
Maximum Velocity ◽  
Operating Conditions ◽  
Small Scale ◽  
Operational Parameters ◽  
Piston Motion ◽  
Free Piston ◽  
Static Test ◽  
And Performance

Initial investigations of a small-scale Free Piston Expander (FPE) are presented. In final form, the FPE will be a MEMS-based device capable of operation from low temperature waste heat sources. In this present study, a millimeter scale device is constructed and tested to yield insight into critical operational parameters. Different constructions and operating conditions are considered as are the effects on basic piston motion and performance. These include piston length and mass. In addition, different sealing and lubricating fluids are considered. Construction of this testbed device is via concentric copper tubing, allowing an effective baseline study of these determining parameters. Results show that, while thick lubricants seal well in a static test, piston motion is decreased in a dynamic test indicating leakages. By contrast, reduced viscosity lubricants dont seal as well in a static test, but yield increased piston motion in dynamic testing. This indicates effective sealing. The trends established by the study of varying viscosity lubricants hold true for pistons of increasing mass and length as well. A mixture of isopropanol and water performed well in these tests, and represented a low viscosity sealing fluid. Compared to conditions where no lubricant was used, maximum velocity was increased up to 50%. These results indicate that a thin, wetting fluid will be the best lubricant for the FPE, due to increased sealing and performance when in dynamic operation.

Design and Optimization of Free Piston Expander for Energy Harvesting

2013 ◽  
Author(s):  
C. Champagne ◽  
L. Weiss
Keyword(s):  
Low Temperature ◽  
Waste Heat ◽  
Operating Efficiency ◽  
Small Scale ◽  
Operational Parameters ◽  
Piston Motion ◽  
Cross Sectional ◽  
Free Piston ◽  
Power Sources ◽  
Potential System

There is a growing opportunity and need for research that investigates alternate power sources. One such source is low temperature waste heat, or energy cast off to the environment as part of some larger process. Through the capture and use of this abundant energy source for power production, it is possible to enhance the overall operating efficiency of the larger system. This presents significant potential for sustainability increase and energy savings. One potential system that can operate from these sources is a low temperature, small-scale steam expander. Investigations of one such device called a Free Piston Expander (FPE) are presented in this work. In final form, the FPE will be a MEMS based device capable of operation as part of a complete low temperature steam system. In this present study, a millimeter scale device is constructed and tested to yield insight into critical operational parameters for future microfabricated designs. Construction of this testbed device is via concentric copper tubing, allowing an effective baseline study of these determining parameters. Parameters studied include device cross sectional area and shape as well as operational pressure. Once consistent parameters are determined, three separate variations of circular FPE design are further tested. These FPEs are designed to either constrain piston rotation or allow for rotational freedom during operation. Testing is performed on these devices for consistency in piston motion. Piston motion is characterized based on a single expansion and reaction of the piston.

Design and Performance of a Diaphragm Free-Piston Stirling Engine for Power Production From Low-Temperature Heat Sources

2018 ◽  
Author(s):  
Anas Nawafleh ◽  
Khaled R. Asfar
Keyword(s):  
Low Temperature ◽  
Waste Heat ◽  
Engine Performance ◽  
Surface Friction ◽  
Stirling Engine ◽  
Operating Conditions ◽  
Physical Parameters ◽  
Free Piston ◽  
And Performance ◽  
Free Piston Stirling Engine

This paper addresses modeling, design, and experimental assessment of a Gamma type low-temperature differential free-piston Stirling engine. The most advanced third-order design analysis method is used to model, simulate and optimize the engine. Moreover, the paper provides an experimental parametric investigation of engine physical parameters and operating conditions on the engine performance. The experimental test results are presented for a model validation, which shows about a 5% to 10% difference in the simulation results. The aim of this study is to design a Stirling engine capable of harvesting low-temperature waste heat effectively and economically and convert it to power. The engine prototype is designed to increase the engine performance by eliminating the main losses occurred in conventional Kinematic engines. Thus, elastic diaphragm pistons are used in this prototype to eliminate the surface friction of the moving parts, the use of lubricant, and to provide appropriate seals. In addition, flat plate heat exchangers, linear flexure bearing, a stainless-steel regenerator and a polyurethane displacer are outlined as the main components of the engine. Experiments successfully confirm the design models for output power and efficiency. Furthermore, it is revealed that the displacer-to-piston natural frequency ratio is an important design point for free-piston Stirling engines and should be addressed in the design for optimum power output.

scholarly journals Thin Gas Film Isothermal Condensation in Aerodynamic Bearings

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Eliott Guenat ◽  
Jürg Schiffmann
Keyword(s):  
High Speed ◽  
Waste Heat ◽  
Load Capacity ◽  
Saturation Pressure ◽  
Operating Conditions ◽  
Fluid Film ◽  
Small Scale ◽  
Vapor Compression ◽  
Density Profiles ◽  
Film Pressure

Abstract High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles is typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might locally reach the saturation pressure with potentially hazardous effects on the performance of the gas bearing. The present work introduces a model based on the Reynolds equation and the development of cavitation modeling in liquid-lubricated bearings for condensing gas bearings. The effect of condensation on load capacity and pressure and density profiles is investigated for two one-dimensional bearing geometries (parabolic and Rayleigh step) and varying operating conditions. The results suggest that the load capacity is generally negatively affected if condensation occurs. An experimental setup consisting of a Rayleigh-step gas journal bearing with pressure taps to measure the local fluid film pressure is presented and operated in R245fa in near-saturated conditions. The comparison between the evolution of the fluid film pressure under perfect gas and near saturation conditions clearly suggests the occurrence of condensation in the fluid film. These results are corroborated by the very good agreement with the model prediction.

Review of Expander Selection for Small-Scale Organic Rankine Cycle

2014 ◽  
Author(s):  
Saeedeh Saghlatoun ◽  
Weilin Zhuge ◽  
Yangjun Zhang
Keyword(s):  
Internal Combustion Engines ◽  
Large Scale ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Small Scale ◽  
Manufacturing Cost ◽  
Operating Characteristics ◽  
Small Scale Industries

After more than twenty years working on the selection of an appropriate expander for Organic Rankine cycles and wide research and attentions about its influence on the performance and total cost of waste heat recovery systems, now there is a good-enough background studies and achievement for large scale applications. But small-scale industries is like a art space to modify and revise the previous results. As it is clearly known, in small-scale applications and industries especially in internal combustion engines, besides the investigation of performance, physical properties and final efficiency of expander, other parameters should be analyzed accurately like manufacturing cost, availability, reliability, sensitivity to operating condition fluctuations. Due to a significant role of expander equipment to enhance the efficiency of ORC system in the first step expanders is investigated. In this paper, as per related operating characteristics, a complete comparison of small-scale expanders will be debated to guide designers to select more appropriate and the best efficient expansion machine as per their requirements. According to available literatures there is more need to do research about different types of expanders with various operating conditions in small-scale industries.

scholarly journals Parametric Simulations on Leakage and Performance of a Miniature Free-Piston Generator (MFPG)

2021 ◽  
Vol 11 (16) ◽  
pp. 7742
Author(s):  
Saifei Zhang ◽  
Chunhua Zhang ◽  
Yong Liu ◽  
Wei Wu ◽  
Han Wu ◽  
...  
Keyword(s):  
Combustion Engine ◽  
Electric Energy ◽  
Voice Coil Motor ◽  
Electrical Equipment ◽  
Energy Conversion Efficiency ◽  
Small Scale ◽  
Portable Devices ◽  
Free Piston ◽  
Heat Engines ◽  
And Performance

The miniaturization of electrical equipment and popularization of portable devices is an appealing motivation for the development of small-scale heat engines. However, the in-cylinder charge leaks severely as the engine dimension shrinks. The free-piston engine on a small scale provides better sealing than other miniature heat engines. Therefore, a miniature free-piston generator (MFPG) with a single-piston internal combustion engine (ICE) and a voice coil motor (VCM) was proposed in this work. A dynamic model with special attention on the heat transfer and leakage was established accordingly, upon which parametric studies of leakage and its effects on the performance of the MFPG system were performed. Four key parameters, including scavenging pressure, ignition position, combustion duration and piston mass, were considered in the model. The results showed that the mass leakage during the compression decreases with the rise of the motoring current. The indicated thermal efficiency can be improved by boosting scavenging pressure and increase motoring current. The critical ignition position is 2 mm before the top dead center. When ignition occurs later than that, the MFPG system is incapable of outputting power. The chemical to electric energy conversion efficiency is about 5.13 %, with an output power of 10~13 W and power density around 4.7~5.7 W/cc.

CFD Modeling of Flow and Heat Transfer Inside a Liquid-Cooled Exhaust Manifold

2003 ◽  
Author(s):  
Rade Milanovic ◽  
Chenn Q. Zhou ◽  
Jim Majdak ◽  
Robert Cantwell
Keyword(s):  
Heat Transfer ◽  
Flow Property ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Inlet Temperature ◽  
Operational Parameters ◽  
Manifold Optimization ◽  
Parametric Effects ◽  
And Performance

Liquid cooled exhaust manifolds are used in turbo charged diesel and gas engines in the marine and various industrial applications. Performance of the manifold has a significant impact on the engine efficiency. Modifying manifold design and changing operational parameters are ways to improve its performance. With the rapid advance of computer technology and numerical methods, Computational Fluid Dynamics (CFD) has become a powerful tool that can provide useful information for manifold optimization. In this study, commercial CFD software (FLUENT®) was used to analyze liquid cooled exhaust manifolds. Detailed information of flow property distribution and heat transfer were obtained in order to provide a fundamental understanding of the manifold operation. Experimental data was compared with the CFD results to validate the numerical simulation. Computations were performed to investigate the parametric effects of operating conditions (engine rotational speed, coolant flow rate, coolant inlet temperature, exhaust gas inlet temperature, surface roughness of the manifold’s material) on the performance of the manifold. Results were consistent with the experimental observations. Suggestions were made to improve the manifold design and performance.

Analysis and Comparison Between Fixed and Variable Volume Ratio Expander for Micro-Scale ORC

2015 ◽  
Author(s):  
Sergei Gusev ◽  
Martijn van den Broek
Keyword(s):  
Waste Heat ◽  
Volume Ratio ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Variable Volume ◽  
Fixed Volume ◽  
Wide Range ◽  
The Right

Waste heat recovery has become very important in the last decennia. The Organic Rankine Cycle is the most popular technology to transform waste heat into mechanical work or electricity. While large and medium scale installations are widely available on the market for various temperature and power levels, small scale ORCs are still in a pre-commercial phase because of a relatively high specific price. To make small scale ORCs more attractive for potential customers, the price has to be drastically reduced which means reducing the manufacturing and assembling operations, the number of parts in assemblies and unification of these assemblies. In addition, the performance has to be increased by using advanced cycle architectures and the right fluids. Not only the right choice of the working fluid is important but also the expander built-in volume ratio (BVR) has to be optimal or improved. Neither a fixed volume ratio expander, nor a turbine can provide an optimal expansion of a working fluid in a wide range of operating conditions [1]. In automotive applications, for instance, a strongly fluctuating heat input will be introduced to an ORC unit. To estimate losses caused by non-optimal operation, a model of a volumetric expander has been developed and verified using the result of extensive test campaigns with a screw expander. The volume ratio of the expander mentioned cannot be physically changed, so under widely changing pressure ratio, caused by varying inlet waste heat and ambient temperatures, it operates mostly far from its design point. The model gives a possibility to vary the BVR in order to compare a fixed-volume ratio expander with a variable one. Benefits from replacement of this expander by an adaptive one are studied. Only steady states are taken into account since there is no dynamic model of this expander developed yet. As a consequence of the results obtained, a concept of a variable volume ratio expander is proposed.

MODERN EQUIPMENT FOR DETERMINING TRACTOR-SPEED PROPERTIES OF THE VEHICLE: CHARACTERISTICS’ ANALYSIS IN LABORATORY CONDITIONS

2019 ◽  
Vol 16 (3) ◽  
pp. 276-289
Author(s):  
N. V. Savenkov ◽  
V. V. Ponyakin ◽  
S. A. Chekulaev ◽  
V. V. Butenko
Keyword(s):  
Environmental Performance ◽  
Operating Conditions ◽  
Special Role ◽  
Development Stages ◽  
Advantages And Disadvantages ◽  
Force Transfer ◽  
Characteristics Analysis ◽  
And Performance ◽  
Loading Devices ◽  
Structural Solutions

Introduction. At present, stands with running drums are widely used for various types of tests. Power stands play a special role. Such stands take the mechanical power from the driving wheels of the car. This simulates the process of movement of the vehicle under operating conditions. Such equipment has various designs, principles of operation and performance. It is also used in tests that are different by purpose, development stages and types: research, control, certification, etc. Therefore, it is necessary in order to determine the traction-speed, fuel-efficient and environmental performance characteristics.Materials and methods. The paper provides the overview of the power stands with running drums, which are widespread on the domestic market. The authors carried out the analysis of the main structural solutions: schemes of force transfer between the wheel and the drum; types of loading devices; transmission layout schemes and features of the control and measuring complex. The authors also considered corresponding advantages and disadvantages, recommended spheres of application, demonstrated parameters and characteristics of the units’ workflow, presented components and equipment.Discussion and conclusions. The authors critically evaluate existing models of stands with running drums. Such information is useful for choosing serial models of stands and for developing technical tasks for designing or upgrading the equipment.

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