Stirling Cycle Engines E-Book

Allan J. Organ

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 368

Veröffentlichungsjahr: 2013

Beschreibung

Some 200 years after the original invention, internal design of a Stirling engine has come to be considered a specialist task, calling for extensive experience and for access to sophisticated computer modelling. The low parts-count of the type is negated by the complexity of the gas processes by which heat is converted to work. Design is perceived as problematic largely because those interactions are neither intuitively evident, nor capable of being made visible by laboratory experiment. There can be little doubt that the situation stands in the way of wider application of this elegant concept. Stirling Cycle Engines re-visits the design challenge, doing so in three stages. Firstly, unrealistic expectations are dispelled: chasing the Carnot efficiency is a guarantee of disappointment, since the Stirling engine has no such pretentions. Secondly, no matter how complex the gas processes, they embody a degree of intrinsic similarity from engine to engine. Suitably exploited, this means that a single computation serves for an infinite number of design conditions. Thirdly, guidelines resulting from the new approach are condensed to high-resolution design charts - nomograms. Appropriately designed, the Stirling engine promises high thermal efficiency, quiet operation and the ability to operate from a wide range of heat sources. Stirling Cycle Engines offers tools for expediting feasibility studies and for easing the task of designing for a novel application. Key features: * Expectations are re-set to realistic goals. * The formulation throughout highlights what the thermodynamic processes of different engines have in common rather than what distinguishes them. * Design by scaling is extended, corroborated, reduced to the use of charts and fully Illustrated. * Results of extensive computer modelling are condensed down to high-resolution Nomograms. * Worked examples feature throughout. Prime movers (and coolers) operating on the Stirling cycle are of increasing interest to industry, the military (stealth submarines) and space agencies. Stirling Cycle Engines fills a gap in the technical literature and is a comprehensive manual for researchers and practitioners. In particular, it will support effort world-wide to exploit potential for such applications as small-scale CHP (combined heat and power), solar energy conversion and utilization of low-grade heat.

Leseprobe

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Library of Congress Cataloging-in-Publication Data

Organ, Allan J.      Stirling cycle engines: inner workings and design / Allan J Organ.         pages cm      Includes bibliographical references and index.      ISBN 978-1-118-81843-5 (cloth)    1. Stirling engines. 2. Stirling engines–Design and construction. I. Title.      TJ765.O738 2014      621.4′2–dc23

2013031868

A catalogue record for this book is available from the British Library.

ISBN: 9781118818435

About the Author

Apart from a six-year spell developing tooling for high-speed metal forming, the author’s academic research career – which concluded with 20 years in Cambridge University Engineering Department where he learned more than he taught – has focused on Stirling cycle machines.

It would be gratifying to be able to claim that this commitment had resulted in his becoming an authority – perhaps the authority. However, it is a feature of the Stirling engine – perhaps its irresistible attraction – that it does not yield up its subtleties quite so readily. Thus the author writes, not as a self-styled expert, but as a chronic enthusiast anxious that the results of his most recent enquiries should not expire with him! It must now fall to a more youthful intellect to pursue matters.

With the 200th anniversary of the 1816 invention fast approaching, the author remains optimistic of a commercial future for a design targeting appropriate applications and undertaken with realistic expectations. Readers interested in this vision may wish to look out for a work of fiction entitled ‘The Bridge’.

Foreword

What is the source of the Stirling cycle’s siren song? Why has it attracted so many for so long (including yours truly over some 30-plus years)? In part, it is simply that Stirling engines are not in common use, so that each idealist who stumbles upon some brief description of such, perceives that he has stumbled upon hidden gold, a gift to the world that needs only to be unwrapped and presented to a grateful society that will receive its promise of clean, quiet, reliable power. No valves, no timing, no spark, no explosions – what could be simpler? Arthur C. Clarke said “Any sufficiently developed technology is indistinguishable from magic”. Surely, then, with just a bit of development, or better materials, or the keen insight of one who sees what others have missed, the Stirling engine will blossom into the fruition of its magical promise.

And yet. …

The first such machines were built two centuries ago, though only retrospectively identified with their eponymous creator, Rev. Robert Stirling. That naming came mostly by virtue of his invention of the “economizer” (what we now recognize as the regenerator in a reciprocating machine of this type), and was promoted most effectively by Rolf Meijer, who led the change from air-charged machines to light-gas, pressurized devices at Philips in the 1940s. Dr. Meijer might be said to be the father of the modern Stirling engine, as the earlier work did not have the benefits of thermodynamics as a science or modern materials like stainless steel.

And yet. … 

It is remarkable that some 70 years after the Philips Stirling generator sets were produced, then abandoned as unprofitable, they remain one of the benchmarks against which novel attempts at Stirling engines of practical utility are measured. Few have succeeded in bettering their technical performance, and fewer still have achieved any greater commercial returns. Countless hobbyists, dozens of corporate ventures, and even a few large-scale government projects have come and gone.

And yet. …

Not one living person in a million today has seen, used, or been empowered by a Stirling engine. Why then, do we persist in our apparently sisyphean pursuit of this esoteric system? And commensurately, why is the present book important?

It has been noted that most diversity exists at the interfaces among ecosystems: that the junctions of field and forest, sea and shore, or sky and soil support more life in more forms than the depths of any one such domain. It is sure that these are the sites of evolution. As an inventor–instructor–entrepreneur, it has been apparent to me that a similar effect applies to intellectual pursuits: the greatest opportunities for development are to be found at the intersections of disciplines, rather than at their cores. Recent advances in combination fields such as mechatronics, evolutionary biology, and astrophysics might be evidence of some truth in this observation. Let us consider the Stirling engine in this light, the better to appreciate the value of this book.

Thermodynamics, heat transfer, fluid science, metallurgy, structural mechanics, dynamics of motion: all these and more are essential elements in Stirling embodiments and their mastery serves as arrows in the quiver of the developer aiming for Stirling success. Perhaps this is one reason why we are attracted to the Stirling – each finds his own expertise essential to it. And perhaps this is one reason why success is so hard to achieve, for who has all these skills at hand? And if success demands such polymath capacities, where is one to begin?

There are many published works on the broad topic of Stirling cycles, engines, and coolers, especially if the reader seeks descriptive or historical information. A selection of analytical texts can be found for those seeking guidance on the first-principles design of aspects of a new engine, including some worthy treatises on the numerical simulation of complete engines (or coolers). Yet none provides a technically sound, computationally compact path to buildable, valid engines.

This new work builds on the author’s earlier focus on the essential regenerator and the application of similarity principles, validated by well-documented machines that serve here as a basis for scaling rules and the design of new engines for applications and operating conditions that superficially differ greatly from prior examples. It must be at those new conditions, perhaps at the intersections of conventional mechanics with micro-, or bio-, or other technologies, that new and evolved implementations of Stirling technology will arise and become, perhaps, successful. In this offering, Dr. Organ does the world of Stirling developers (and would-be Stirling magnates) a great service. For many times, new energy has been brought to this field and applied without reference to the experiences, successes, and failures of the past, here applied to great effect.

That tendency to dive in without a thorough grounding in the prior art is due only in part to the aforementioned siren song of Stirling and its addling effect on the newly captured. Such repetitive waste is also driven by the relative inaccessibility of much of the greater body of Stirling technical literature (e.g., I watched the published output of one famous free-piston company go through several 2-year cycles of re-inventions, as successive tiers of graduate students rotated through!).

The challenge is that, even when accessible as correct content, much of what is published in Stirling literature is either uselessly facile or excruciatingly partial in scope, so as to preclude its ready application to new designs. Tools to fit that job have not heretofore been available to those not willing or able to amass and absorb a gargantuan (if dross-filled) library of publications and apply that through associated years of experimental training. This book, through the author’s elegant nomographic presentation – fully sustained by clear text and mathematical underpinnings – provides just that holistic entry point, presented with wit and minimal pain in calculations.

Hints of whole-physics participation in Stirling analysis abound here, not least in the dismissal of Schmidt models for their gross errors and oversimplifications that have led to conceptual misunderstandings and hampered many development efforts. I am particularly pleased at the refutation of long-standing shibboleths such as the “evil” of dead space; shattered here with clear and concrete constructions of the actual effects of dead space, and its value in the right places and amounts. In my own work of recent years, which has merged a long Stirling experience with more recently developed thermoacoustic science, the key has been full consideration of the inertial properties of the cycle fluids, which is ignored by most Stirling models and simulations. Here, those effects are illustrated and their contributions to actual Stirling device behaviors discussed in a unique bridge between closed-form, analytical methods, and the full physics of numerical simulation, including a proper dressing-down and reformulation of the steady-flow correlations so often misapplied to this oscillatory system. The resulting graphics are both useful and beautiful.

Dr. Organ’s offered tools, FastTrack, FlexiScale, and ReScale fulfill his promise of guiding the designer of a new Stirling engine to a safe island in the sea of possibilities. This traceable relation from technically successful engines of the past (although I am, of course, crushed that none of mine are among those cited), without the need to extract and refine the data from disparate sources elsewhere, opens the possibility of building a useful Stirling engine to a much larger population of aspirants. Perhaps by this means, some clever member thereof will at last find the sweet spot for commercial success; but at the very least, innumerable hours that would otherwise have been wasted in blind stabs can now be channelled into production refinements on a sturdy base. This is indeed a grand achievement, and being provided in so readable a volume is all the more so: a gift to the Stirling Community sure to be acclaimed throughout.

I am honored to call this author my friend and fellow explorer, and to introduce you, the reader, to this work with the certainty that if you have heard already that siren song of Stirling, this book by Allan Organ can lead you to safe harbor in plotting your course in response. Gentlefolk, Start Your Engines!

Dr John Corey