Fuel Rail Pressure Rise during Cold Start of a Gasoline Direct Injection Engine
Gasoline direct injection provides reduced engine emissions, increased power, and increased fuel economy as compared to port fuel injection (PFI). Reduced emissions are largely due to starting the engine using high fuel pressure (up to 150 bar) and injecting into the compression stroke. During a cold start, fuel pressure must be increased from lift pump pressure (typically 4 to 6 bar) to desired injection pressure (typically 25 bar minimum). Start times are therefore impacted by the high pressure pump's ability to quickly build fuel pressure during crank. This study investigates the temperature and pressure affects during engine soak which allow vapor and air to form in the fuel system. Vapor and/or air in the system cause a slower fuel pressure build and increases start times. The scope of the problem and possible solutions were determined using theoretical and empirical testing. By preventing air and vapor formation in the fuel system, reduced and more consistent start times are achieved.
Cold-Start Computational Fluid Dynamics Simulation of Spark-Ignition Direct-Injection Engine
Reliably starting the engine during extremely cold ambient temperatures is one of the largest calibration and emissions challenges in engine development. Although cold-start conditions comprise only a small portion of an engine's typical drive cycle, large amounts of hydrocarbon and particulate emissions are generated during this time, and the calibration of cold-start operation takes several months to complete. During the cold start period, results of previous cycle combustion event strongly influences the subsequent cycle due to variations in engine speed, residual fraction, residual wall film mass, in-cylinder charge and wall temperatures, and air flow distribution between cylinders. Including all these parameters in computational fluid dynamics (CFD) simulation is critical in understanding the cold start process in transient and cumulative manner. Measured cold start data of a production of four-cylinder spark-ignition (SI) direct-injection engine were collected for this study with an ambient temperature of −30 °C. Three-dimensional (3D) transient engine flow, spray, and combustion simulation over first three consecutive engine cycles is carried out to provide a better understanding of the cold-start process. Measured engine speed and one-dimensional (1D) conjugate heat transfer (CHT) model is used to capture realistic in-cylinder flow dynamics and transient wall temperatures for more accurate fuel–air mixing predictions. The CFD predicted cumulative heat release trend for the first three cycles matches the data from measured pressure analysis. The same observation can be made for the vaporized fuel mass as well. These observations are explained in the report.
Iustitia Dei: A History of the Christian Doctrine of Justification
Preface Acknowledgements 1. Prolegomena 2. The fountainhead: Augustine of Hippo 3. The development of the doctrine in the medieval period 4. The medieval schools of thought on justification 5. The transition from the medieval to the modern period 6. The development of the doctrine in the Reformation period 7. The Tridentine decree of justification 8. The legacy of the English Reformation 9. The modern period Appendix: a glossary of medieval soteriological terms Abbreviations Notes Bibliography Index.