【作者】

Dino Imhof，Daisuke Tsuru，Hiroshi Tajima

【摘要】

论文已在中国上海举行的2013年CIMAC大会上发表，论文的版权归CIMAC所有。The use of natural gas as fuel for vessels is a highly promising solution to meet the challenges of technical compliance requested by upcoming CO2, SOx, NOx and soot emission regulations. In gas injection (GI) engines, gas sprays burn as diffusive combustion without knocking or misfiring. The thermal efficiency is high because a high compression ratio, equal to diesel engines, can be applied. However, unlike lean burn gas engines, an additional device, such as an EGR or SCR system, is required to meet IMO Tier III NOx regulations. In order to analyze and understand the combustion processes of such potential concepts to reduce emissions, a Rapid Compression Expansion Machine (RCEM) with relevant dimensions of marine engines has been developed at Kyushu University. The RCEM is utilized as a research model for GI engines. An electronically controlled high-pressure gas injection system enables injection pressures of up to 50 MPa. Diesel pilot sprays in dual fuel mode as well as glow plugs are used for ignition. Air conditions in the cylinder at the gas injection are about 10 MPa and 550 °C, simulating a current GI engine. In a first series of experiments, a cylinder head with a cubic shaped clearance volume and an observation view of 200 mm in width and 50 mm in height is applied to analyze the spray combustion. In the experiments, pure methane, the main component of natural gas, is used. At first, the GI combustion is compared to the diesel spray combustion. As a result, rates of heat release for GI and diesel combustion are comparable, while the emissions decrease by using gas. However, the direct photos taken with 20’000 fps show a different flame behavior between the two fuels. Such differences in the flame characteristics are examined in detail applying the ’Laser shadowgraph’ and the ’BDL (Back Diffused Laser)’ optical techniques. Furthermore, in order to meet IMO Tier III NOx regulations, the oxygen content of the intake air is reduced as a good approximation for an Exhaust Gas Recirculation (EGR) system. As expected, the brightness of the flame decreases and a NOx reduction of 75 % in 17 % O2 can be achieved. For a second series of experiments, a cylinder head with a cylindrical clearance volume is newly developed to allow different swirl velocities and an observation view over the whole 240 mm in diameter window; the side injection system corresponds to a common two-stroke engine. Injection nozzles with different numbers of injection holes are tested, applying different injection pressures, and multi flames are visualized. In conclusion it can be stated that experiments with the RCEM help to determine emission influencing parameters and optimization potential, to visualize and to analyze phenomena that have not been simulated yet.

【会议名称】

第27届CIMAC会议

【会议地点】

上海

【下载次数】

1

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