Development and validation of a phenomenological diesel engine combustion model Citation for published version (APA): Seykens, X. L. J. (2010). Development and validation of a phenomenological diesel engine combustion model. Technische Universiteit Eindhoven. https://doi.org/10.6100/IR656995 DOI: 10.6100/IR656995 Document status and date: Published: 01/01/2010 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. 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Willems Voor mijn ouders Copyright © 2009 by X.L.J. Seykens All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the author. Cover design: Paul Verspaget Grafische Vormgeving-Communicatie Printed by the Eindhoven University Press. This project was co-funded by TNO (Nederlandse Organisatie voor toegepast- natuurwetenschappelijk onderzoek). A catalogue record is available from the Eindhoven University of Technology Library ISBN: 978-90-386-2133-3 Table of contents Table of contents v Summary ix 1 Introduction 1 1.1 Introduction 1 1.2 Background 1 1.2.1 Addition of new technologies 3 1.2.2 Engine combustion and engine controller complexity – need for combustion models 4 1.3 Combustion model types 5 1.3.1 State-of-the-art combustion models for controller development 6 1.4 Objectives and requirements 8 1.4.1 Regulated versus modelled emissions 9 1.4.2 Used modeling approach 9 1.5 Overview of combustion model 9 1.5.1 Combustion model inputs 11 1.5.2 Combustion model outputs 11 1.5.3 Combustion model components 11 1.5.4 Measured versus predicted heat release rate 12 1.6 Outline of thesis 12 1.7 References 12 2 Diesel engine combustion 15 2.1 Introduction 15 2.2 The diesel engine combustion process 15 2.3 The fuel spray – phenomenology of oxidizer entrainment 18 2.4 Conceptual model of diesel combustion 19 2.5 NO formation mechanisms in combustion 22 2.6 Soot formation 24 2.6.1 Phenomenology of soot formation 24 2.6.2 Soot formation in combusting diesel fuel sprays 25 2.7 Influence of engine operating variables 26 2.8 Summary 31 2.9 References 32 v Table of contents 3 Fuel injection model 35 3.1 Introduction 35 3.2 Fuel mass injection model 36 3.2.1 The fuel injector 36 3.2.2 Injection delays 37 3.2.3 Reconstruction of injection rate profile 39 3.2.4 Nozzle hole flow model 40 3.3 Fuel mass injection rate measurements 42 3.3.1 Fuel injection system 42 3.3.2 Measurement method 43 3.3.3 Error estimation 44 3.3.4 Measurement results 45 3.4 Momentum flux measurements 47 3.4.1 Variations between individual nozzle holes 49 3.5 Nozzle flow coefficients 49 3.5.1 Nozzle hole momentum coefficient 50 3.5.2 Nozzle hole discharge coefficient 51 3.6 Reconstructed fuel injection rate profiles 52 3.7 Comparison with single-cylinder engine data 52 3.8 Conclusions 54 3.9 References 54 4 NO formation model 55 4.1 Introduction 55 4.2 Historical background to NO formation modeling 56 4.3 Modeling concept and main model assumptions 58 4.4 Combustion product package initialization 59 4.4.1 Hydrocarbon combustion and adiabatic flame temperature 61 4.4.2 Reactant temperature – Evaporative cooling 62 4.4.3 Dissociation 63 4.4.4 Hot soot particle radiative cooling 64 4.4.5 Turbulence effects – flame strain 68 4.4.6 Overview of adiabatic temperature corrections 79 4.5 Combustion product package evolution 80 4.5.1 Combustion product package thermodynamics 80 4.5.2 Hot gas radiation 81 4.5.3 Mixing model 82 4.6 NO postprocessor 90 4.6.1 Considered NO formation pathways 91 4.6.2 Chemical equilibrium assumption 92 4.6.3 NO postprocessor validation 93 4.6.4 NO2 formation 96 4.7 Summary 96 4.8 References 98 5 Soot formation model 103 5.1 Introduction 103 5.2 Soot formation modeling 103 vi Table of contents 5.3 Soot formation model 104 5.3.1 Modeling concept 104 5.3.2 Soot formation rate 106 5.3.3 Soot oxidation rate 109 5.4 Adaptations to the original soot model 110 5.4.1 Soot from premixed burned fuel 110 5.4.2 Available fuel mass for soot formation 111 5.4.3 Soot formation and oxidation during the burn-out phase 112 5.4.4 Influence of residual gasses - EGR 115 5.5 Conclusions 117 5.6 References 118 6 Emission model identification and validation 121 6.1 Introduction 121 6.1.1 Overview of identification and validation process 122 6.1.2 Outline of the chapter 123 6.2 Emission model inputs 125 6.2.1 Trapped in-cylinder conditions 125 6.2.2 Heat release rate from measured pressure curve 126 6.2.3 Accuracy of NO prediction 127 6.3 The single-cylinder engine measurement set-up 128 6.3.1 Single-cylinder engine set-up 129 6.3.2 Single-cylinder engine measurement matrix 131 6.3.3 Fuel injection equipment characterization 131 6.3.4 Fuel spray characterization 131 6.4 NO model results – Identification and validation 132 6.4.1 NO model results – Temperature of reaction zone 133 6.4.2 NO model results – Oxidizer entrainment 139 6.4.3 NO model results – NO formation kinetics 143 6.5 Single-cylinder engine soot model results 145 6.5.1 Determination of measured soot mass emission 146 6.5.2 Spray cone angle 146 6.5.3 The burn-out phase – Introduced model parameters 147 6.5.4 Injection timing and EGR variation 150 6.5.5 Injection pressure variation 150 6.5.6 Engine speed variation 152 6.6 Multi-cylinder engine 153 6.6.1 Multi-cylinder engine set-up 153 6.6.2 Measurement matrix 154 6.6.3 FIE and spray characterization 155 6.6.4 Model inputs 155 6.6.5 NO model results 155 6.6.6 Soot model results 155 6.6.7 Individual cylinder emission formation prediction 156 6.7 Emission model results analysis 157 6.7.1 NO emission error map 158 6.7.2 Soot emission error map 159 6.7.3 NO reducing phenomena 160 vii Table of contents 6.7.4 Influence of oxidizer entrainment on NO formation 163 6.7.5 Inclusion of the N2O-intermediate pathway 165 6.8 Summarizing conclusions 166 6.9 References 167 7 Heat release rate model 171 7.1 Introduction 171 7.2 Reaction rate model principles 172 7.3 Premixed combustion phase 174 7.3.1 Premixed heat release rate model 174 7.3.2 Available fuel mass for premixed combustion 175 7.3.3 Mean equivalence ratio of premixed burned mixture 178 7.4 Mixing controlled combustion phase 178 7.4.1 Mixing controlled heat release rate model 178 7.4.2 Adaptations to original model 179 7.4.3 Transition between premixed and mixing controlled heat release rate 181 7.5 Results 182 7.5.1 Tuning of model parameters 182 7.5.2 Reconstruction of fuel injection rate 183 7.5.3 Single-cylinder engine results 184 7.5.4 Multi-cylinder engine results 187 7.5.5 Combustion phasing control – CA50 189 7.6 NO and soot emission using predicted ROHR 190 7.6.1 Reconstruction of in-cylinder pressure 191 7.6.2 NO emission using predicted ROHR 191 7.6.3 Soot emission using predicted ROHR 193 7.7 Recapitulation 195 7.8 References 196 8 Conclusions and recommendations 197 8.1 General observations 197 8.2 Conclusions 198 8.3 Recommendations 201 Nomenclature 203 A Liquid length model 207 B In-cylinder pressure signal pegging procedure 209 C Diesel fuel properties 213 Samenvatting 215 Curriculum Vitae 217 Dankwoord 219 viii Summary Development and validation of a phenomenological diesel engine combustion model Reduction of engine development time and cost is of primary interest for combustion engine manufacturers.