Preliminary results from a numerical study on the appendix gap losses in a Stirling engine

Stig Kildegård Andersen, Henrik Carlsen, Per Grove Thomsen

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearch

Abstract

Analytical expressions for the losses in the displacer clearance gap, a.k.a. the appendix gap, have been refined during the last decades. But most real life Stirling engines violate the assumptions behind these expressions and hence the expressions may not be applicable. In this study the gap has been included directly into a one dimensional Stirling engine model. Practical aspects of the method, such as handling the moving wall in the gap while achieving an energy conserving model formulation and handling discontinuous derivatives in the equations, are discussed. A study on the convergence of the spatial discretisation in the gap showed that a relatively coarse discretisation was adequate for studying the appendix gap losses and showed significant variations in the axial wall temperature gradients along the gap. A parameter study on the size of the displacer clearance gap was performed with different algorithms for computing the heat transfer in the gap. The results showed higher losses for small gap sizes but smaller losses for large gap sizes when compared to analytical expressions for the appendix gap losses. The appendix gap losses were found to influence both the heat intake and work output of the engine.
Original languageEnglish
Title of host publicationProceedings of the 12th International Stirling Engine Conference and Technology Exhibition
Number of pages478
Volume1
Place of PublicationDurham, UK
PublisherDurham University, UK
Publication date2005
Edition1
Pages336-347
ISBN (Print)0-9535-5582-8
Publication statusPublished - 2005
Event12th International Stirling Engine Conference and Technology Exhibition - Durham, United Kingdom
Duration: 7 Sep 20059 Sep 2005
Conference number: 12

Conference

Conference12th International Stirling Engine Conference and Technology Exhibition
Number12
CountryUnited Kingdom
CityDurham
Period07/09/200509/09/2005

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