Modeling and Simulation for Design and Testing of Direct Injection Gaseous Fuel Systems for Medium-Speed Engines

摘要

The purpose of this study is to develop a modeling and simulation environment for the early design and testing for high pressure injection of alternative fuels in a medium-speed engine application. The proper injection of fuel into the cylinder at the correct timing and with the desired rate is a key to high combustion efficiency. The fuel spray and gas jet characteristics are governed by the injection pressure and nozzle geometry. Incorrect injection causes a reduced efficiency and increasing concentration of harmful emissions. In addition to efficient and clean combustion, safety issues are also important design features for fuel injection systems. In particular, the handling of volatile alternative fuels such as natural gas requires special safety functions to prevent hazardous incidents. Efficient and safe fuel injection is obtained through an increased understanding of the dynamic behavior of the complex fuel injection systems, which involves mechatronics, hydraulics and gas dynamics. The objective of this research is to perform an early design evaluation and testing of these complex fuel injection systems to better optimize design parameters, thereby reducing the need for costly prototypes. This simulation-based testing also includes safety functions and failure mode modeling, both of which are extremely difficult and hazardous to test in full scale. Despite the development of powerful numerical methods and computer capability, the modeling of these multi physics systems is not a trivial task, particularly when the systems are non-linear and involve several energy domains. The proper mathematical model representation for mechanical components, hydraulics and compressible gas must be linked together in an interactive model. In this study, the general modeling and simulation software 20-sim has proven to be an excellent tool for this type of analysis. Based on conservation principles, each component of the fuel injection system is modeled separately in a model library and then assembled into a system model. This paper includes application examples in which a system is designed and tested using these simulation models and software tools.