Mühlbauer, Monika (2010)
Modelling wall interactions of a high-pressure, hollow cone spray.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
Spray/wall interactions significantly influence air/fuel mixing and emissions in modern spark-ignited, direct injection engines. Yet, the complex phenomena are hardly understood - especially not with respect to the large number of parameters and the associated wide ranges occuring in an engine. Modelling spray/wall interactions thus presents a major drawback in numerical simulations done in engine development. This thesis focuses on the impact of dense, high-pressure hollow cone sprays for which existing wall interaction models are evaluated in detail and shown to fail. To the best of the author's knowledge no model adapted to the considered spray type was available which was furthermore accompanied by a severe lack of quantitative experimental data. Therefore, Phase Doppler Anemometry (PDA) is used to gather data on the normal impact of an isooctane spray with 50 bar injection pressure on a hemispherical copper target. The latter can be heated and wall temperatures up to 200°C are studied. Moreover, an additional oil film can be applied on the surface to simulate the oil film on a cylinder liner lubricating the piston motion. Variations in the particle Reynolds number between 2000 and 3000 on impact are achieved in changing the distance between injector and target. As the question how PDA data concerning spray/wall interaction have to be evaluated has not been studied thoroughly yet, a fundamental analysis was carried out and is presented in this thesis. The results are not limited to dense and high-pressure, hollow cone sprays but may serve as general guidelines for future data evaluation. Based on the measurements, the impact mechanisms of dense, high-pressure sprays are discussed where film fluctuations leading to ligament breakup are found to be decisive. For the considered high Reynolds numbers, inertial forces dominate all other forces which results in negligible parameter influence of the mean Reynolds number and the wall temperature. The oil film is observed to be quickly removed by the impacting spray which points out that spray/wall interactions on a cylinder liner may seriously endanger the operability of an engine. Finally, empirical correlations describing the secondary spray on wall interaction are developed from the gathered data and an extrapolation to oblique impact is proposed. This first empirical model adapted to dense, high-pressure hollow cone sprays is implemented in numerical code in a Lagrangian approach. Details of the implementation are given. The model is validated in several cases for impact angles between 30° and 90° measured relative to the wall and for injection pressures of 50 bar and 200 bar with very good results.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2010 | ||||
Autor(en): | Mühlbauer, Monika | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Modelling wall interactions of a high-pressure, hollow cone spray | ||||
Sprache: | Englisch | ||||
Referenten: | Tropea, Prof. Dr.- Cameron ; Sommerfeld, Prof. Dr.- Martin ; Roisman, Priv.-Doz. Ilia | ||||
Publikationsjahr: | 7 Januar 2010 | ||||
Ort: | Darmstadt | ||||
Verlag: | Technische Universität | ||||
Datum der mündlichen Prüfung: | 4 September 2009 | ||||
URL / URN: | urn:nbn:de:tuda-tuprints-20191 | ||||
Kurzbeschreibung (Abstract): | Spray/wall interactions significantly influence air/fuel mixing and emissions in modern spark-ignited, direct injection engines. Yet, the complex phenomena are hardly understood - especially not with respect to the large number of parameters and the associated wide ranges occuring in an engine. Modelling spray/wall interactions thus presents a major drawback in numerical simulations done in engine development. This thesis focuses on the impact of dense, high-pressure hollow cone sprays for which existing wall interaction models are evaluated in detail and shown to fail. To the best of the author's knowledge no model adapted to the considered spray type was available which was furthermore accompanied by a severe lack of quantitative experimental data. Therefore, Phase Doppler Anemometry (PDA) is used to gather data on the normal impact of an isooctane spray with 50 bar injection pressure on a hemispherical copper target. The latter can be heated and wall temperatures up to 200°C are studied. Moreover, an additional oil film can be applied on the surface to simulate the oil film on a cylinder liner lubricating the piston motion. Variations in the particle Reynolds number between 2000 and 3000 on impact are achieved in changing the distance between injector and target. As the question how PDA data concerning spray/wall interaction have to be evaluated has not been studied thoroughly yet, a fundamental analysis was carried out and is presented in this thesis. The results are not limited to dense and high-pressure, hollow cone sprays but may serve as general guidelines for future data evaluation. Based on the measurements, the impact mechanisms of dense, high-pressure sprays are discussed where film fluctuations leading to ligament breakup are found to be decisive. For the considered high Reynolds numbers, inertial forces dominate all other forces which results in negligible parameter influence of the mean Reynolds number and the wall temperature. The oil film is observed to be quickly removed by the impacting spray which points out that spray/wall interactions on a cylinder liner may seriously endanger the operability of an engine. Finally, empirical correlations describing the secondary spray on wall interaction are developed from the gathered data and an extrapolation to oblique impact is proposed. This first empirical model adapted to dense, high-pressure hollow cone sprays is implemented in numerical code in a Lagrangian approach. Details of the implementation are given. The model is validated in several cases for impact angles between 30° and 90° measured relative to the wall and for injection pressures of 50 bar and 200 bar with very good results. |
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Alternatives oder übersetztes Abstract: |
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Freie Schlagworte: | spray/wall interaction high-pressure, hollow cone spray modelling impact mechanism Phase Doppler Anemometry data evaluation | ||||
Zusätzliche Informationen: | Die Druckausgabe der Dissertation ist im Shaker-Verlag (Aachen) als Bd. 22 der Schriftenreihe "Forschungsberichte Strömungslehre und Aeordynamik) mit der ISBN 978-3-8322-8645-3 erschienen. |
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Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 500 Naturwissenschaften 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau |
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Fachbereich(e)/-gebiet(e): | 16 Fachbereich Maschinenbau > Fachgebiet Strömungslehre und Aerodynamik (SLA) 16 Fachbereich Maschinenbau |
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Hinterlegungsdatum: | 19 Jan 2010 11:31 | ||||
Letzte Änderung: | 05 Mär 2013 09:30 | ||||
PPN: | |||||
Referenten: | Tropea, Prof. Dr.- Cameron ; Sommerfeld, Prof. Dr.- Martin ; Roisman, Priv.-Doz. Ilia | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 4 September 2009 | ||||
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