Search Results

Maritime environmental regulations stipulate lower emissions from the shipping industry. To cope with these rules, improving the combustion processes, make use of cleaner alternative fuels and implement exhaust gas cleaning systems is necessary. Alternative fuels, like fish oil, have a potential to reduce soot formation during the combustion process and will be deeply investigated in this paper. For this purpose, two different types of fish oil and their blends with marine gas oil (MGO) have been tested in a constant volume pre-combustion cell (CVPC). The CVPC laboratory was built in collaboration between MARINTEK and NTNU. To generate similar injection condition in the combustion cell as in an internal combustion engine, the CVPC is heated using a chemical heating process. The CVPC is used as a fundamental investigation tool for studying the fuel injection system for large engine applications.

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.

The maritime transportation sector is facing new international restrictions on exhaust emissions. NOx and SOx emissions from traditional marine fuels are a major challenge, which make natural gas a promising new clean alternative. Since the late 1980s, new concepts for medium-speed natural gas-fuelled engines have been developed, primarily for stationary power generation. This technology is currently entering the mobile sector, where Spark Ignition engines, Dual-Fuel engines and High Pressure Gas engines offer advantages such as high efficiency, low emissions and fuel flexibility. The availability of liquefied natural gas (LNG) is increasing, not least via small-scale distribution systems. In Norway, 23 coastal traffic vessels operate on LNG supplied by a distribution system that also supplies city bus fleets. This paper discusses the development of natural gas engines and fuel system technology, and describes experiences from LNG-fuelled ships in operation in Norway.

The use of numerical models and simulation during development, testing and operation of fuel injection systems is becoming more and more an important tool as modern computer capability increase rapidly. Numerical simulations support the engineer in understanding his system better, and enables him to make modifications and test the response within seconds. Advanced fuel injection systems consist of components from several different energy domains such as hydraulics, mechanics and electronics, working together in a highly dynamic process. Despite the latest development of powerful numerical methods and computer capability, the preparation of a mathematical model in the proper form is not a trivial task, particularly when the system is nonlinear and involves more than one energy domain as for the fuel injection systems. Bond Graph modeling has proven to handle these multi domain systems efficiently and consistently in a unified approach.

Variable composition of natural gas depending on the gas source causes variable ignition and combustion properties when used as fuel in internal combustion engines. Ignition and combustion problems lead to reduced efficiency, increased levels of emissions, as well as increased mechanical and thermal loads on engine components. The main objective of this study is to investigate the influence of natural gas composition on ignition properties in a direct injection hot surface assisted compression ignition engine. Previous investigations have shown that ignition of methane require hot surface temperature in the range of 1200-1400 K in order to obtain an ignition delay within 2 milliseconds. Pure methane and several natural gas mixtures have been tested under various conditions in a constant volume combustion bomb and in a test engine. Ignition delay and cycle to cycle variations are used to compare the combustion qualities of the different gas.

Burning natural gas in a direct injection diesel engine, requires a special arrangement to secure ignition. In this study a hot surface assisted ignition concept is investigated in a constant volume combustion bomb and a test engine with the objective to develop a better understanding of the mechanisms involved. The experiments show that surface temperature above 1200 K is required to achieve acceptable ignition, strongly dependant on natural gas composition and system parameters such as injection and hot surface geometry. A mathematical model of the concept is also being developed. Numerical simulations combined with experiments allow us to look closer into the processes, and to expand the test matrix even outside the physical limits of the test engine. This paper will give an outline of the investigation including some results from experiments and numerical simulations.