Thermodynamic performance of heat exchangers in a free piston Stirling engine

There is an increasing request in energy recovery systems that are more efficient, environmentally friendly and economical. The free piston Stirling engine has been investigated due to its structural simplicity and high efficiency, coupled with its cogeneration ability. This study presents the numerical investigation of quasi-steady model of a gamma type free piston Stirling engine (FPSE), including the thermodynamic analysis of the heat exchangers. Advanced thermodynamic models are employed to derive the initial set of operational parameters of the FPSE due to the coupling of the piston’s (displacer and piston) dynamics and the working process. The proximity effect of the heater and cooler on the regenerator effectiveness in relation to the heat losses, output power, net work and thermal efficiency of the FPSE are also observed and presented in this study. It can be observed that at temperatures of 541.3 °C and 49.8 °C of the heater and cooler, respectively, with heater volume of 0.004 m3, regenerator volume of 0.003 m3 and cooler volume of 0.005 m3, the FPSE produced an output performance of 996.7 W with a thermal efficiency of 23% at a frequency of 30 Hz. This approach can be employed to design effective high performance FPSE due to their complexity and also predict a satisfactory performance

Optimisation of a quasi-steady model of a free-piston Stirling engine

Energy from waste heat recovery is receiving considerable attention due to the demand for power systems that are less polluting. This has led to the investigation of external combustion engines such as the free-piston Stirling engine (FPSE) due to its ability to generate power from any source of heat and, especially, waste heat. However, there are still some limitations in the modelling, design and practical utilisation of this type of engine. Modelling of the FPSE has proved to be a difficult task due to the lack of mechanical linkages in its configuration, which poses problems for achieving stability. Also, a number of studies have been reported that attempt to optimise the output performance considering the characteristics of the engine configuration. In this study the optimisation of the second-order quasi-steady model of the gamma-type FPSE is carried out using the genetic algorithm (GA) to maximise the performance in terms of power output, and considering the design parameters of components such as piston and displacer damper, geometry of heat exchangers, and regenerator porosity. This present study shows that the GA optimisation of the RE-1000 FPSE design parameters improved its performance from work done and output power of 33.2 J and 996 W, respectively, with thermal efficiency of 23%, to 44.2 J and 1326 W with thermal efficiency of 27%

Bibliography of Lewis Research Center technical publications announced in 1993

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1993. All the publications were announced in the 1993 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Unified modelling of aerospace systems: a bond graph approach

Systems Integration is widely accepted as the basis for improving the efficiency and performance of many engineering products. The aim is to build a unified optimised system not a collection of subsystems that are combined in some ad hoc manner. This moves traditional design boundaries and, in so doing, enables a structured evolution from an integrated system concept to an integrated system product. It is recognised that the inherent complexity cannot be handled effectively without mathematical modelling. The problem is not so much the large number of components but rather the very large number of functional interfaces that result. The costs involved are high and, if the claims of improved efficiency and performance are to be affordable (or even achievable), predictive modelling and analysis will play a major role in reducing risk. A modelling framework is required which can support integrated system development from concept through to certification. This means building a 'system' inside a computer and demonstrating the feasibility of an entire development cycle. The objective is to provide complete coverage of system functionality so as to gain confidence in the design before becoming locked into a full development programme with associated capital investment and contractual arrangements. With these points in mind the purpose of this thesis is threefold. First, to demonstrate the application of bond graphs as a unified modelling framework for aerospace systems. Second, to review the main principles involved with the modelling of engineering systems and to justify the selection of the bond graph notation as a suitable means of representing the power flow (i.e. the dynamics) of physical systems. Third, to present an exposition of the bond graph method and to evolve it into a versatile notation for integrated systems. The originality of the work is based on the recognition that systems integration is a relatively new field of interest without a mature body of academic literature or reported research. Apparently, there is no open literature on the modelling of complete air vehicles plus their embedded vehicle systems which deals with issues of integrated dynamics and control. To this end, bond graph concepts need to be developed and extended in new direction in order to facilitate an intuitive approach to the modelling of integrated systems

Bibliography of Lewis Research Center Technical Publications announced in 1991

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific engineering work performed and managed by the Lewis Research Center in 1991. All the publications were announced in the 1991 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Dynamical systems : mathematical and numerical approaches

Proceedings of the 13th Conference „Dynamical Systems - Theory and Applications" summarize 164 and the Springer Proceedings summarize 60 best papers of university teachers and students, researchers and engineers from whole the world. The papers were chosen by the International Scientific Committee from 315 papers submitted to the conference. The reader thus obtains an overview of the recent developments of dynamical systems and can study the most progressive tendencies in this field of science

Energy: A continuing bibliography with indexes, issue 38

This bibliography lists 1367 reports, articles and other documents introduced into the NASA scientific and technical information system from April 1, 1983 through June 30, 1983

Energy: A continuing bibliography with indexes

This bibliography lists 1096 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System from April 1, 1979 through June 30, 1979

ECOS 2012

The 8-volume set contains the Proceedings of the 25th ECOS 2012 International Conference, Perugia, Italy, June 26th to June 29th, 2012. ECOS is an acronym for Efficiency, Cost, Optimization and Simulation (of energy conversion systems and processes), summarizing the topics covered in ECOS: Thermodynamics, Heat and Mass Transfer, Exergy and Second Law Analysis, Process Integration and Heat Exchanger Networks, Fluid Dynamics and Power Plant Components, Fuel Cells, Simulation of Energy Conversion Systems, Renewable Energies, Thermo-Economic Analysis and Optimisation, Combustion, Chemical Reactors, Carbon Capture and Sequestration, Building/Urban/Complex Energy Systems, Water Desalination and Use of Water Resources, Energy Systems- Environmental and Sustainability Issues, System Operation/ Control/Diagnosis and Prognosis, Industrial Ecology

NASA Tech Briefs, April 1993

Topics include: Optoelectronics; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences