Optimization of a Marine Medium-Speed Engine With Multi-Injector System by 1D Predictive Simulation

The thermal efficiency and emission of large bore marine medium-speed diesel engine are required to be improved under the stringent legislations. A multi-injector system has been proposed in order to improve the thermal efficiency and NOx emission instantaneously. However, application of the multi-injector system increased the complexity of parameter optimization and control. To develop proper control strategy of the novel multi-injector system, a 1D engine model of the original engine configurations was developed initially, including a predictive combustion model in commercial 1D simulation program (GT-Power). After calibrated by test results and literature data under various engine loads, the engine model was modified from a central single injector engine to a multi-injector engine. On the basis of a conventional direct-injection diesel engine, another two injectors were added to the cylinder as side injectors in the model. And the fundamental combustion characteristics and engine performance of the marine medium-speed diesel engine with multi-injector are investigated under various injection quantity ratio between the central injector and side injectors. The effects of injection timing and split injection are also studied by simulation. The result indicated that the effective thermal efficiency and NOx emission of the medium speed marine diesel engine are optimized instantaneously by changing the injection strategies of the central and side injectors. Finally, the preferred injection strategy is proposed by the 1D model.

Overview of modern control systems for internal combustion engines

The article provides an overview of modern microprocessor control systems for internal combustion engines, which allow improving the entire complex of design, technological, environmental and operational characteristics of engines due to the wide possibilities of regulating the working process in each cycle of each cylinder. The directions of research and development on the creation of adaptive engines are considered. It is indicated that the main distinguishing feature of engines with a variable workflow of any design scheme is that these adaptability properties are achieved by increasing the number of controlled elements in comparison with existing engines. The article provides an overview of the controlled elements implemented in internal combustion transport engines and discusses the technical solutions that are used by well-known global companies in the field of marine medium-and high-speed engines. The directions in the field of improving computers that control engines are described.

Optimization of Marine Medium Speed Diesel Engine Performance based on Multi-Injector System

Multi-injector system is potential to improve thermal efficiency and NOx emission of diesel engine at the same time. In order to optimize the combustion and emission of Marine medium speed diesel engine, the engine combustion with a multi-injector system is simulated and analyzed by CFD software Converge. In this research, two injectors are installed at the side of the cylinder head while the central injector is maintained. Various injection directions of side injectors and injection strategies of multi-injector system are simulated to optimize the fuel spray and combustion. The analysis results show that the spray angle of the side injector plays a key role for effective thermal efficiency improvement, since complex spray jet-jet interaction and spray impingement may deteriorate the combustion if the arrangement of spray angle was not set properly. Once the fuel injection direction has been optimized, the fuel ratio of the three injectors is optimized and improved the effective thermal efficiency with lower NOx emission. The results show that the two side injectors could increase the fuel injection rate into the cylinder, leading to high brake power and consequently increased the thermal efficiency by 1.26% and decreased the NOx emission by 16% for the best optimization.

Analysis of the Impact of Split Injection on Fuel Consumption and NOx Emissions of Marine Medium-Speed Diesel Engine

The medium-speed diesel engine in diesel-electric propulsion systems is increasingly used as the propulsion engine for liquefied natural gas (LNG) ships and passenger ships. The main advantage of such systems is high reliability, better maneuverability, greater ability to optimize and significant decreasing of the engine room volume. Marine propulsion systems are required to be as energy efficient as possible and to meet environmental protection standards. This paper analyzes the impact of split injection on fuel consumption and NOx emissions of marine medium-speed diesel engines. For the needs of the research, a zero-dimensional, two-zone numerical model of a diesel engine was developed. Model based on the extended Zeldovich mechanism was applied to predict NOx emissions. The validation of the numerical model was performed by comparing operating parameters of the basic engine with data from engine manufacturers and data from sea trials of a ship with diesel-electric propulsion. The applicability of the numerical model was confirmed by comparing the obtained values for pressure, temperature and fuel consumption. The operation of the engine that drives synchronous generator was simulated under stationary conditions for three operating points and nine injection schemes. The values obtained for fuel consumption and NOx emissions for different fuel injection schemes indicate the possibility of a significant reduction in NOx emissions but with a reduction in efficiency. The results showed that split injection with a smaller amount of pilot fuel injected and a smaller angle between the two injection allow a moderate reduction in NOx emissions without a significant reduction in efficiency. The application of split injection schemes that allow significant reductions in NOx emissions lead to a reduction in engine efficiency.

On the effect of circulatory flow around objects in marine medium and atmosphere

Analytical expressions of the hydrodynamic reaction of a point dipole in two-layer circulatory fluid flow around it are obtained. The dependence of the wave resistance and the lift force on the flow velocity, the density jump, the circulation and the depth of the sea is investigated. It is shown that the influence of the velocity circulation leads to a change in the lift force acting on the dipole. Moreover, such changes are reversible in a relatively narrow range of the velocity of flow around the pipeline. Along with the pipeline, such features in the nature of the effect of circulation on the lift force can be manifested for self-propelled underwater objects and aerial vehicles.