Water injection is one of the most promising technologies to improve the engine combustion efficiency, by mitigating knock occurrences and controlling exhaust gas temperature before turbine. As result, the engine can operate at stoichiometric conditions over the whole engine map, even during the more power-demanding RDE cycles. Antonino Vacca presents a methodology to study and optimize the effect of water injection for gasoline engines by investigating different engine layouts and injection strategies through the set-up of a 3D-CFD virtual test bench. He investigates indirect and direct water injection strategies to increase the engine knock limit and to reduce exhaust gas temperature for several operating points.
Author(s): Antonino Vacca
Series: Wissenschaftliche Reihe Fahrzeugtechnik Universität Stuttgart
Publisher: Springer Vieweg
Year: 2021
Language: English
Pages: 170
City: Wiesbaden
Preface
Contents
Figures
Tables
Abbreviations
Symbols
Abstract
Kurzfassung
1 Introduction
1.1 The performance of water injection to fulfil RDE cycles
1.2 Thermodynamic of water injection
1.2.1 Water injection concept for SI-engines
1.2.2 Water physical properties
1.2.3 Limiting factors for water cooling effect
1.2.4 Influence of ambient air humidity on water injection strategy
1.3 The role of 3D-CFD virtual engine development
1.4 Future of ICEs and electro mobility
1.4.1 Comparison between BEVs and ICEs
1.4.2 Alternative fuels
2 Fundamentals of CFD for ICEs
2.1 The real working process analysis
2.2 1D-CFD simulation
2.3 3D-CFD simulation
2.3.1 Fundamental equations
2.3.2 Turbulence modelling
3 The 3D-CFD Virtual Test Bench
3.1 QuickSim approach and methodology
3.2 Accurate fuel description
3.3 Water injection implementation
3.4 Auto-ignition model and Knock detection criterion
3.5 Influence of water vapour on flame speed and auto-ignition
3.6 Combustion modelling
3.7 Spray modelling
4 Simulation of Injections
4.1 Problematics of spray analysis
4.2 Injector characteristics and optical measurements
4.3 Models used and parameters description
4.3.1 Spray definition and geometrical parameters
4.3.2 Breakup model
4.3.3 Droplet evaporation
4.4 Imaging tool and injector calibration methodology
4.5 Different behaviour between water and gasoline injection
4.6 Spray targeting developments and engine virtual testing
5 Optimization of the Engine Map through Water Injection
5.1 Set-up of the single-cylinder engine test bench
5.2 Building of the 3D virtual test bench in QuickSim
5.3 Model validation and calibration
6 Water Injection for Enhancing Knock Resistance
6.1 Indirect water injection strategies
6.1.1 Influence of water injection pressure
6.1.2 Combustion and Knock analysis
6.2 Direct water injection strategies
6.2.1 Optimization of the water injector targeting
6.2.2 Turbulence enhancement
6.2.3 Water evaporation and influence on mixture formation
6.2.4 Combustion and Knock analysis
6.2.5 Results of the spark advance sweep
6.2.6 Mixture formation induced by water injection
6.2.7 Influence of injection pressure on spark advance
6.3 Water injection in combination with Miller cycle
6.3.1 Increase of back-pressure
6.3.2 Valve strategies and rise of the compression ratio
7 Influence of Water Injection on Soot Formation
7.1 Experimental results
7.2 Simulation results
8 Water Injection for Exhaust Gas Temperature Control
8.1 Indirect water injection strategies
8.1.1 Ignition point sweep at rated power
8.2 Direct water injection strategies
8.3 Comparison between indirect and direct water injection
9 Conclusion and Outlook
9.1 Optical measurements and 3D-CFD injection simulations
9.2 Effects of indirect and direct water injection strategies
9.3 Effects of Miller valve profile
9.4 Outlooks and further possibilities
Bibliography
Appendix
Appendix 1
