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Characterization, Analysis, and Optimization of Rotary Displacer Stirling Engines

Description: This work focuses on an innovative Rotary Displacer SE (RDSE) configuration for Stirling engines (SEs). RDSE features rotary displacers instead of reciprocating displacers (found in conventional SE configurations), as well as combined compression and expansion spaces. Guided by the research question "can RDSE as a novel configuration achieve a higher efficiency compared to conventional SE configurations at comparable operating conditions?", the goal of this study is to characterize, analyze, and optimize RDSE which is pursued in three technical stages. It is observed the RDSE prototype has an optimum phase angle of > 90° and thermal efficiency of 15.5% corresponding to 75.2% of the ideal (Carnot) efficiency at the source and sink temperatures of 98.6° C and 22.1° C, respectively. Initial results indicate that 125° phase angle provides more power than that of the theoretically optimum 90° phase angle. The results also show comparable B_n and significantly higher W_n values (0.047 and 0.465, respectively) compared to earlier studies, and suggest the RDSE could potentially be a competitive alternative to other SE configurations. Furthermore, due to lack of a regenerator, the non-ideal effects calculated in the analytical approach have insignificant impact (less than 0.03 kPa in 100 kPa). The clearance volume in the shuttled volume has a dramatic negative effect and reduces the performance up to 40%. Ultimately, utilizing CFD, it is proved that the existing geometry is relatively optimized where the optimum phase angle is 121° and geometric ratio D\/L for the displacer is 0.49.
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Date: December 2019
Creator: Bagheri, Amirhossein
Partner: UNT Libraries

Preliminary Analysis of an Innovative Rotary Displacer Stirling Engine

Description: Stirling engines are an external combustion heat engine that converts thermal energy into mechanical work that a closed cycle is run by cyclic compression and expansion of a work fluid (commonly air or Helium) in which, the working fluid interacts with a heat source and a heat sink and produces network. The engine is based on the Stirling cycle which is a subset of the Carnot cycle. The Stirling cycle has recently been receiving renewed interest due to some of its key inherent advantages. In particular, the ability to operate with any form of heat source (including external combustion, flue gases, alternative (biomass, solar, geothermal) energy) provides Stirling engines a great flexibility and potential benefits since it is convinced as engines running with external heat sources. However, several aspects of traditional Stirling engine configurations (namely, the Alpha, Beta, and Gamma), specifically complexity of design, high cost, and relatively low power to size and power to volume ratios, limited their widespread applications to date. This study focuses on an innovative Stirling engine configuration that features a rotary displacer (as opposed to common reciprocating displacers), and aims to utilize analytical and numerical analysis to gain insights on its operation parameters. The results are expected to provide useful design guidelines towards optimization. The present study starts with an overview of the Stirling cycle and Stirling engines including both traditional and innovative rotary displacer configurations, and their major advantages and disadvantages. The first approach considers an ideal analytical model and implements the well-known Schmidt analysis assumptions for the rotary displacer Stirling engine to define the effects of major design and operation parameters on the performance. The analytical model resulted in identifying major variables that could affect the engine performance (such as the dead volume spaces, temperature ratios and the leading phase angle). It was …
Date: December 2015
Creator: Bagheri, Amirhossein
Partner: UNT Libraries

Stirling Engines and Irrigation Pumping

Description: This report was prepared in support of the Renewable Energy Applications and Training Project that is sponsored by the U.S. Agency for International Development for which ORNL provides technical assistance. It briefly outlines the performance that might be achievable from various kinds of Stirling-engine-driven irrigation pumps. Some emphasis is placed on the very simple liquid-piston engines that have been the subject of research in recent years and are suitable for manufacture in less well-developed countries. In addition to the results quoted here (possible limits on M4 and pumping head for different-size engines and various operating conditions), the method of calculation is described in sufficient detail for engineers to apply the techniques to other Stirling engine designs for comparison.
Date: January 1, 1987
Creator: West, C.D.
Partner: UNT Libraries Government Documents Department

Design, fabrication, and testing of a sodium evaporator for the STM4-120 kinematic Stirling engine

Description: This report describes the development and testing of a compact heat-pipe heat exchanger kW(e) designed to transfer thermal energy from hot combustion gases to the heater tubes of a 25-kW(e) Stirling engine. In this system, sodium evaporates from a surface that is heated by a stream of hot gases. The liquid metal then condenses on the heater tubes of a Stirling engine, where energy is transferred to the engine`s helium working fluid. Tests on a prototype unit illustrated that a compact (8 cm {times} 13 cm {times} 16 cm) sodium evaporator can routinely transfer 15 kW(t) of energy at an operating vapor temperature of 760 C. Four of these prototype units were eventually used to power a 25-kW(e) Stirling engine system. Design details and test results from the prototype unit are presented in this report.
Date: May 1, 1995
Creator: Rawlinson, K.S. & Adkins, D.R.
Partner: UNT Libraries Government Documents Department

Heat Pipe Solar Receiver Development Activities at Sandia National Laboratories

Description: Over the past decade, Sandia National Laboratories has been involved in the development of receivers to transfer energy from the focus of a parabolic dish concentrator to the heater tubes of a Stirling engine. Through the isothermal evaporation and condensation of sodium. a heat-pipe receiver can efficiently transfer energy to an engine's working fluid and compensate for irregularities in the flux distribution that is delivered by the concentrator. The operation of the heat pipe is completely passive because the liquid sodium is distributed over the solar-heated surface by capillary pumping provided by a wick structure. Tests have shown that using a heat pipe can boost the system performance by twenty percent when compared to directly illuminating the engine heater tubes. Designing heat pipe solar receivers has presented several challenges. The relatively large area ({approximately}0.2 m{sup 2}) of the receiver surface makes it difficult to design a wick that can continuously provide liquid sodium to all regions of the heated surface. Selecting a wick structure with smaller pores will improve capillary pumping capabilities of the wick, but the small pores will restrict the flow of liquid and generate high pressure drops. Selecting a wick that is comprised of very tine filaments can increase the permeability of the wick and thereby reduce flow losses, however, the fine wick structure is more susceptible to corrosion and mechanical damage. This paper provides a comprehensive review of the issues encountered in the design of heat pipe solar receivers and solutions to problems that have arisen. Topics include: flow characterization in the receiver, the design of wick systems. the minimization of corrosion and dissolution of metals in sodium systems. and the prevention of mechanical failure in high porosity wick structures.
Date: January 8, 1999
Creator: Adkins, D.R.; Andraka, C.E.; Moreno, J.B.; Moss, T.A.; Rawlinson, K.S. & Showalter, S.K.
Partner: UNT Libraries Government Documents Department

Status of the Boeing Dish Engine Critical Component Project

Description: The Boeing Company's Dish Engine Critical Component (DECC) project started in April of 1998. It is a continuation of a solar energy program started by McDonnell Douglas (now Boeing) and United Stirling of Sweden in the mid 1980s. The overall objectives, schedule, and status of this project are presented in this paper. The hardware test configuration, hardware background, operation, and test plans are also discussed. A summary is given of the test data, which includes the daily power performance, generated energy, working-gas usage, mirror reflectivity, solar insolation, on-sun track time, generating time, and system availability. The system performance based upon the present test data is compared to test data from the 1984/88 McDonnell Douglas/United Stirling AB/Southem California Edison test program. The test data shows that the present power, energy, and mirror performance is comparable to when the hardware was first manufactured 14 years ago.
Date: January 8, 1999
Creator: Brau, H.W.; Diver, R.B.; Nelving, H. & Stone, K.W.
Partner: UNT Libraries Government Documents Department

Development of a 75-kW heat-pipe receiver for solar heat-engines

Description: A program is now underway to develop commercial power conversion systems that use parabolic dish mirrors in conjunction with Stirling engines to convert solar energy to electric power. In early prototypes, the solar concentrator focused light directly on the heater tubes of the Stirling engine. Liquid-metal heat-pipes are now being developed to transfer energy from the focus of the solar concentrator to the heater tubes of the engine. The dome-shaped heat-pipe receivers are approximately one-half meters in diameter and up to 77-kW of concentrated solar energy is delivered to the absorber surface. Over the past several years, Sandia National Laboratories, through the sponsorship of the Department of Energy, has conducted a major program to explore receiver designs and identify suitable wick materials. A high-flux bench-scale system has been developed to test candidate wick designs, and full-scale systems have been tested on an 11-meter test-bed solar concentrator. Procedures have also been developed in this program to measure the properties of wick materials, and an extensive data-base on wick materials for high temperature heat pipes has been developed. This paper provides an overview of the receiver development program and results from some of the many heat-pipe tests.
Date: May 1, 1995
Creator: Adkins, D.R.; Andraka, C.E. & Moss, T.A.
Partner: UNT Libraries Government Documents Department

Rolling Thunder -- Integration of the Solo 161 Stirling engine with the CPG-460 solar concentrator at Ft. Huachuca

Description: Project Rolling Thunder is a dish/Stirling demonstration project at Ft. Huachuca, a US Army fort in southeastern Arizona (Huachuca means rolling thunder in Apache). It has been supported by the Strategic Environmental Research and Development Program (SERDP), a cooperative program between the Department of Defense (DoD) and the Department of Energy (DOE). As part of a 1992 SERDP project, Cummins Power Generation, Inc. (CPG) installed a CPG 7 kW(c) dish/Stirling system at the Joint Interoperability Test Command (JITC) in Ft. Huachuca, Arizona. The primary objective of the SERDP Dish/Stirling for DoD Applications project was to demonstrate a CPG 7-kW(c) dish/Stirling system at a military facility. Unfortunately, Cummins Engine Company decided to divest its solar operations. As a direct result of Ft. Huachuca`s interest in the Cummins dish/Stirling technology, Sandia explored the possibility of installing a SOLO 161 Stirling power conversion unit (PCU) on the Ft. Huachuca CPG-460. In January 1997, a decision was made to retrofit a SOLO 161 Stirling engine on the CPG-460 at Ft. Huachuca. Project Rolling Thunder. The SOLO 161 Demonstration at Ft. Huachuca has been a challenge. Although, the SOLO 161 PCU has operated nearly flawlessly and the CPG-460 has been, for the most part, a solid and reliable component, integration of the SOLO PCU with the CPG-460 has required significant attention. In this paper, the integration issues and technical approaches of project Rolling Thunder are presented. Lessons of the project are also discussed.
Date: September 1, 1998
Creator: Diver, R.B.; Moss, T.A.; Goldberg, V.; Thomas, G. & Beaudet, A.
Partner: UNT Libraries Government Documents Department

Solar-Electric Dish Stirling System Development

Description: Electrical power generated with the heat from the sun, called solar thermal power, is produced with three types of concentrating solar systems - trough or line-focus systems; power towers in which a centrally-located thermal receiver is illuminated with a large field of sun-tracking heliostats; and dish/engine systems. A special case of the third type of system, a dish/Stirling system, is the subject of this paper. A dish/Stirling system comprises a parabolic dish concentrator, a thermal receiver, and a Stirling engine/generator located at the focus of the dish. Several different dish/Stirling systems have been built and operated during the past 15 years. One system claims the world record for net conversion of solar energy to electric power of 29.4%; and two different company`s systems have accumulated thousands of hours of on-sun operation. Due to de-regulation and intense competition in global energy markets as well as the immaturity of the technology, dish/Stirling systems have not yet found their way into the marketplace. This situation is changing as solar technologies become more mature and manufacturers identify high-value niche markets for their products. In this paper, I review the history of dish/Stirling system development with an emphasis on technical and other issues that directly impact the Stirling engine. I also try to provide some insight to the opportunities and barriers confronting the application of dish/Stirling in power generation markets.
Date: December 31, 1997
Creator: Mancini, T.R.
Partner: UNT Libraries Government Documents Department

Statistical Identification of Effective Input Variables

Description: This report provides background and procedural information for the use of a general-purpose Stirling-engine analysis code developed at Argonne National Laboratory and available through the National Energy Software Center. Different engine configurations are easily specified, or the user may make use of provided data for existing engines, both kinematic and free piston. The code models heat transfer and fluid mechanics throughout the engine and accounts for system energy flows and losses. Good agreement is shown between code predictions and experimental measurements. The present analysis method was chosen for fast execution and useful information on energy flows in the system. A description is provided of the code structure that is intended to accept different analysis modules that can provide improved system modeling or optimization capability.
Date: September 1982
Creator: Vaurio, J. K.
Partner: UNT Libraries Government Documents Department

Dish/Stirling for Department of Defense applications final report

Description: This report describes a Strategic Environmental Research and Development Program (SERDP) project to field a dish/Stirling system at a southwestern US military facility. This project entitled ``Dish/Stirling for DoD Applications`` was started in August 1993 and was completed in September 1996. The project`s objective was to assist military facilities to field and evaluate emerging environmentally sound and potentially economical dish/Stirling technology. Dish/Stirling technology has the potential to produce electricity at competitive costs while at the same time providing a secure and environmentally benign source of power. In accordance with the SERDP charter, this project leveraged a US Department of Energy (DOE) cost-shared project between Sandia National Laboratories and Cummins Power Generation, Inc. (CPG). CPG is a wholly owned subsidiary of Cummins Engine Company, a leading manufacturer of diesel engines. To accomplish this objective, the project called for the installation of a dish/Stirling system at a military facility to establish first-hand experience in the operation of a dish/Stirling system. To scope the potential DoD market for dish/Stirling technology and to identify the site for the demonstration, a survey of southwestern US military facilities was also conducted. This report describes the project history, the Cummins dish/Stirling system, results from the military market survey, and the field test results.
Date: March 1, 1997
Creator: Diver, R.B. & Menicucci, D.F.
Partner: UNT Libraries Government Documents Department

Concentrating Solar Power Program overview

Description: Over the last decade, the US solar thermal industry has established a track record in the power industry by building and operating utility-scale power plants with a combined rated capacity of 354 megawatts (MW). The technology used in these power plants is based on years of research and development (R and D), much of it sponsored by the US Department of Energy (DOE). DOE`s Concentrating Solar Power (CSP) Program is collaborating with its partners in the private sector to develop two new solar technologies -- power towers and dish/engines -- to meet the huge commercial potential for solar power.
Date: April 1, 1998
Partner: UNT Libraries Government Documents Department

Solar Heat-Pipe Receiver Wick Modeling

Description: Stirling-cycle engines have been identified as a promising technology for the conversion of concentrated solar energy into usable electrical power. In previous experimented work, we have demonstrated that a heat pipe receiver can significantly improve system performance-over a directly-illuminated heater head. The design and operating conditions of a heat pipe receiver differ significantly from typical laboratory heat pipes. New wick structures have been developed to exploit the characteristics of the solar generation system. Typically, these wick structures allow vapor generation within the wick. Conventional heat pipe models do not handle this enhancement yet it can more than double the performance of the wick. In this study, I develop a steady-state model of a boiling-enhanced wick for a solar heat pipe receiver. The model is used for design-point calculations and is written in FORTRAN90. Some limited comparisons have been made with actual test data.
Date: December 21, 1998
Creator: Andraka, C.E.
Partner: UNT Libraries Government Documents Department

Felt-metal-wick heat-pipe solar receiver

Description: Reflux heat-pipe receivers have been identified as a desirable interface to couple a Stirling-cycle engine with a parabolic dish solar concentrator. The reflux receiver provides power nearly isothermally to the engine heater heads while decoupling the heater head design from the solar absorber surface design. The independent design of the receiver and engine heater head leads to higher system efficiency. Heat pipe reflux receivers have been demonstrated at approximately 65 kW{sub t} power throughput. Several 25 to 30-kW{sub e} Stirling-cycle engines are under development, and will soon be incorporated in commercial dish-Stirling systems. These engines will require reflux receivers with power throughput limits reaching 90-kW{sub t}. The extension of heat pipe technology from 60 kW{sub t} to 100 kW{sub t} is not trivial. Current heat pipe wick technology is pushed to its limits. It is necessary to develop and test advanced wick structure technologies to perform this task. Sandia has developed and begun testing a Bekaert Corporation felt metal wick structure fabricated by Porous Metal Products Inc. This wick is about 95% porous, and has liquid permeability a factor of 2 to 8 times higher than conventional technologies for a given maximum pore radius. The wick has been successfully demonstrated in a bench-scale heat pipe, and a full-scale on-sun receiver has been fabricated. This report details the wick design, characterization and installation into a heat pipe receiver, and the results of the bench-scale tests are presented. The wick performance is modeled, and the model results are compared to test results.
Date: December 31, 1994
Creator: Andraka, C. E.; Adkins, D. R.; Moss, T. A.; Cole, H. M. & Andreas, N. H.
Partner: UNT Libraries Government Documents Department

The Utility-Scale Joint-Venture Program

Description: The Department of Energy`s Utility-Scale Joint-Venture (USJV) Program was developed to help industry commercialize dish/engine electric systems. Sandia National Laboratories developed this program and has placed two contracts, one with Science Applications International Corporation`s Energy Projects Division and one with the Cummins Power Generation Company. In this paper we present the designs for the two dish/Stirling systems that are being developed through the USJV Program.
Date: June 1, 1994
Creator: Gallup, D. R. & Mancini, T. R.
Partner: UNT Libraries Government Documents Department

Solar heat pipe testing of the Stirling thermal motors 4-120 Stirling engine

Description: Stirling-cycle engines have been identified as a promising technology for the conversion of concentrated solar energy into usable electrical power. A 25kW electric system takes advantage of existing Stirling-cycle engines and existing parabolic concentrator designs. In previous work, the concentrated sunlight impinged directly on the heater head tubes of the Stirling Thermal Motors (STM) 4-120 engine. A Sandia-designed felt-metal-wick heat pipe receiver was fitted to the STM 4-120 engine for on-sun testing on Sandia`s Test Bed Solar Concentrator. The heat pipe uses sodium metal as an intermediate two-phase heat transfer fluid. The receiver replaces the directly-illuminated heater head previously tested. The heat pipe receiver provides heat isothermally to the engine, and the heater head tube length is reduced, both resulting in improved engine performance. The receiver also has less thermal losses than the tube receiver. The heat pipe receiver design is based on Sandia`s second-generation felt-wick heat pipe receiver. This paper presents the interface design, and compares the heat pipe/engine test results to those of the directly-illuminated receiver/engine package.
Date: July 1, 1996
Creator: Andraka, C.E.; Rawlinson, K.S.; Moss, T.A.; Adkins, D.R.; Moreno, J.B.; Gallup, D.R. et al.
Partner: UNT Libraries Government Documents Department

An investigation of corrosion in liquid-metal heat pipes

Description: Research is underway to develop a 75-kW heat pipe to transfer solar energy from the focus of a parabolic dish concentrator to the heater tubes of a Stirling engine. The high flux levels and high total power level encountered in this application have made it necessary to use a high-performance wick structure with fibers on the order of 4 to 8 microns in diameter. This fine wick structure is highly susceptible to corrosion damage and plugging, as dissolved contaminants plate out on the evaporator surface. Normal operation of the heat pipe also tends to concentrate contaminants in localized areas of the evaporator surface where heat fluxes are the highest. Sandia National Laboratories is conducting a systematic study to identify procedures that reduce corrosion and contamination problems in liquid-metal heat pipes. A series of heat pipes are being tested to explore different options for cleaning heat-pipe systems. Models are being developed to help understand the overall importance of operating parameters on the life of heat-pipe systems. In this paper, the authors present their efforts to reduce corrosion damage.
Date: August 1, 1998
Creator: Adkins, D.R.; Rawlinson, K.S.; Andraka, C.E.; Showalter, S.K.; Moreno, J.B.; Moss, T.A. et al.
Partner: UNT Libraries Government Documents Department

Results of the Boeing/DOE DECC Phase 1 stirling engine project

Description: Phase I of Boeing Company/DOE Dish Engine Critical Component (DECC) Project started in April of 1998 and was completed in 1999. The Phase I objectives, schedule, and test results are presented in this paper. These data shows the power, energy, and mirror performance are comparable to that when the hardware was first manufactured 15 years ago. During the Phase I and initial Phase II test period the on-sun system accumulated over 3,800 hours of solar-powered operating time, accumulated over 4,500 hours of concentrator solar tracking time, and generated over 50,000 kWh of grid-compatible electrical energy. The data also shows that the system was available 95 {percent} of the time when the sun's insolation level was above approximately 300 w/m{sup 2}, and achieved a daily energy efficiency between 20{percent} and 26{percent}. A second concentrator was refurbished during Phase I and accumulated over 2,200 hours of solar track time. A second Stirling engine operated 24 hours a day in a test cell in Sweden and accumulated over 6,000 test hours. Discussion of daily operation shows no major problems encountered during the testing that would prevent commercialization of the technology. Further analysis of the test data shows that system servicing with hydrogen, coolant and lubricating oil should not be a major O and M cost.
Date: March 2, 2000
Partner: UNT Libraries Government Documents Department

Solar dish/engine systems

Description: Solar dish/engine systems convert the energy from the sun into electricity at a very high efficiency. Using a mirror array formed into the shape of a dish, the solar dish focuses the sun's rays onto a receiver. The receiver transmits the energy to an engine that generates electric power. Because of the high concentration ratios achievable with parabolic dishes and the small size of the receiver, solar dishes are efficient at collecting solar energy at very high temperatures. Tests of prototype systems and components at locations throughout the US have demonstrated net solar to electric conversion efficiencies as high as 30%. This is significantly higher than any other solar technology.
Date: April 1, 1998
Partner: UNT Libraries Government Documents Department

A long-term strategic plan for development of solar thermal electric technology

Description: Solar thermal electric (STE) technologies--parabolic troughs, power towers, and dish/engine systems--can convert sunlight into electricity efficiently and with minimum effect on the environment. These technologies currently range from developmental to early commercial stages of maturity. This paper summarizes the results of a recent strategic planning effort conducted by the US Department of Energy (DOE) to develop a long-term strategy for the development of STE technologies (DOE, 1996). The planning team led by DOE included representatives from the solar thermal industry, domestic utilities, state energy offices, and Sun-Lab (the cooperative Sandia National Laboratories/National Renewable Energy Laboratory partnership that supports the STE Program) as well as project developers. The plan was aimed at identifying specific activities necessary to achieve the DOE vision of 20 gigawatts of installed STE capacity by the year 2020. The planning team developed five strategies that both build on the strengths of, and opportunities for, STE technology and address weaknesses and threats. These strategies are to support future commercial opportunities for STE technologies; demonstrate improved performance and reliability of STE components and systems; reduce STE energy costs; develop advanced STE systems and applications; and address nontechnical barriers and champion STE power. The details of each of these strategies are discussed.
Date: June 1997
Creator: Williams, T. A.; Burch, G. D.; Chavez, J. M.; Mancini, T. R. & Tyner, C. E.
Partner: UNT Libraries Government Documents Department

Heat-Pipe Wick Characterization

Description: The development of liquid metal heat-pipes for use in solar powered Stirling engines has led to an in-depth analysis of heat-pipe wick properties. To model the flow of liquid sodium through the wick its two-phase permeability measurement is of interest. The permeability will be measured by constructing a test cell made up of a wick sample sintered to a manifold. Measuring the volumetric flow rate through the wick will allow for a determination of the wick's permeability as a function of pressure. Currently, simple estimates of permeability as a function of vapor fraction of a porous media are being used as a model to calculate the two-phase permeability. The above mentioned experiment will be used to test the existing formulas validity. The plan is to make use of a known procedure for testing permeability and apply those techniques to a felt-metal wick. The results will be used to verify and/or modify the two-phase permeability estimates. With the increasing desire to replace directly illuminated engines with the much more efficient heat-pipe apparatus it is inherently clear that the usefulness of known wick properties will make wick permeability design a simpler process.
Date: August 15, 2000
Partner: UNT Libraries Government Documents Department
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