Advanced Materials Research Vols. 354-355

Abstract: To study all-regime performance of marine diesel propulsion system in ship maneuvering, an all-regime model for diesel propulsion system is established, including starting, braking, reversing, etc. The dynamic simulation models of propeller running across four quadrants and ship longitudinal motion are given too. A 76000DWT bulk carrier is selected as plant. The simulation results show that steady data of diesel are in good accordance with test-bed data, and dynamic data match to ship sea trial data in crash stop condition. The model is accurate and effective.

Abstract: Material of Sm₂Zr₂O₇ composition powder was synthesized by coprecipitation method using Sm₂O₃ and ZrOCl₂•8H₂O as raw materials, and applied as ceramic topcoats of thermal barrier coating (TBC) by atmospheric plasma spraying (APS). The ceramics powder was prepared with proper distribution of particle size about 30-70μm by spray-dried method. Phase analyses revealed that Sm₂Zr₂O₇ coatings keeping the single phase with pyrochlore structure before and after the thermal cycling test. The thermally grown oxide at the topcoat-bondcoat interface and the formation of transverse crack were the major factors that lead to the coating failure on thermal cycling.

Abstract: Heavy-duty gas turbine is used widely in power generation industry for many advantages. Gas turbine inlet system is an important component of the gas turbine. The work to study the inlet elbow system was less in the past. In fact, structure design of the inlet elbow system has important influence on performance and life of the gas turbine. In this paper, the three-dimensional structural model of gas turbine inlet elbow system is built; the stress field for the inlet elbow system is analyzed by using finite element method (FEM). The maximum stress and distribution characteristics of stress field in the inlet elbow system is computed. It provides a reliable basis for reasonable design and safety evaluation of the inlet elbow system in gas turbine.

Abstract: Experimental investigation results of the fuel injector group in a heavy-duty gas turbine are presented. Atomization characteristic has great impact about combustion, inflame, temperature field of outlet. Obtained atomization characteristic about spray particle size and spray angle using LDV/PDPA system, determined dimension of injector group. On the basis of these tests, the combustion testing of the injector group in the flame tube is made, its every targets are arrived in the design requirements. This has demonstrated: the test systems and test methods are practical, feasible and reliable. These experimental data have provided the reliable basis for the injector group design and development.

Abstract: An experimental investigation was conducted on 4100 engine to study the influences of different percentages of methanol in DME/diesel blended fuel on combustion and emission performance. The result indicates that a certain amount of methanol in DME/diesel blended fuel can reduce production cost, improve the engine's power performance at the same time, but when the methanol percentage is increased (over 2%), the power performance will decrease. With the increase of methanol proportions, the maximum cylinder pressure is slightly increased, the peak of heat-release curves are declined and delayed, the cylinder temperature is decreased, the ignition timings are delayed and the combustion duration is shortened. In addition, NOx emissions were further reduced, but the HC emission, the CO emission and the soot emission has a little rise.

Abstract: Spring nozzles are widely used in deaerators. The spray issued from a spring nozzle was studied numerically with an adapted volume of fluid method combined with a continuous surface force model to capture the gas–liquid interface dynamics. The present analysis focuses on the formation of a water film and the generation of droplets near the spring nozzle outlet. The numerical simulation results show that the water film breaks up to droplets at the location 20~25cm from the nozzle exit vertically. The vortical structures are formed due to the interaction between the liquid film and the surrounding air, which leads to air recirculation and water film instability. When the inlet water velocity decreases from 5.33m/s to 4.1m/s, it results in a slightly reduced spray angle. But the vertical break up length is not obviously influenced. The water sheet disintegration is probably at the transition state between Rayleigh and first wind-induced breakup regimes.

Abstract: Based on sensitivity of fuel physicochemical property to temperature,in order to study the effects of fuel injection temperature on spray and combustion performance of diesel engine, commercial CFD software STAR-CD is used to simulate the spray and combustion processes of diesel engine with heating fuel spray. Through compared with experimental results, calculation models are proved to be validity. The effects of different fuel injection temperatures on in–cylinder air motion, temperature field and exhaust emissions are researched in the CA6DL1-30 diesel engine. The results show that there is a valid temperature range for fuel injection in diesel engine. And it’s possible to implement Low NO_x Combustion with heating fuel spray.

Abstract: The study on combustion characteristics of different excess air ratios (λ) and ignition timings was conducted on a lean-burn spark-ignition CNG engine, and the corresponding emission characteristics was also analyzed. The results show that the curve of cylinder pressure moves towards TDC, and the CoVimep decreases with the advance of ignition timing. With the excess air ratio increasing, the CoVimep increases while the cylinder pressure decreases firstly, and then increases. The flame development duration increases with the ignition timing advanced, but the rapid flame duration decreases, the total combustion duration basically keep constant, and all of them increase with the increasement of excess air ratio. Best fuel economy was gotten at λ=1.2. With the excess air ratio increasing, the CO and NMHC emissions decrease, the NOx emission firstly reaches to a peak value, which is about 3000ppm at λ=1.2, and then decreases. Both of the THC and CH4 emissions have opposite trends to NOx emission. All the emissions mentioned above increases with the advance of ignition timing.

Abstract: A three-dimensional model of a diesel Urea-SCR（Selective Catalytic Reduction）catalytic converter system was set up with aid of CFD software AVL FIRE coupled with available knowledge of SCR chemical reaction kinetics. Basing on the validation of the spray injection model of Urea-water-solution, the numerical simulation was made to get the distribution of pressure, velocity, temperature and species concentration in the converter and NO_x conversion in different conditions by considering the injection and evaporation of the urea-water-solution, the thermal decomposition and hydrolysis into ammonia and the surface catalytic reactions in the monolith. The simulated results have some reference meaning for improving NO_x conversion efficiency and optimizing the diesel SCR catalytic converter.

Abstract: The research is conducted on emulsified fuel applied to engine YC6J190 without any modification of the engine. In this experiment, the contrast of the fuel consumption and the emissions is studied with having water or not. From the results, it can be concluded that the emulsified fuel can reduce the NOx and smoke emissions greatly at the same time, but the fuel consumption is different in different conditions. The emulsified fuel with 20% water is most suitable for this type of engine regarding fuel consumption and emissions. Then dynamic characteristics is tested using the emulsified fuel with 20% water to find that the decline in power and torque output is not apparent. At the end, we conclude that emulsion containing 20% of water would replace diesel as for this type of engine.