Optical Characterization of the Combustion Process inside a Large-Bore Dual-Fuel Two-Stroke Marine Engine by Using Multiple High-Speed Cameras

Abstract

<div class="section abstract"><div class="htmlview paragraph">Dual-fuel engines for marine propulsion are gaining in importance due to operational and environmental benefits. Here the combustion in a dual-fuel marine engine operating on diesel and natural gas, is studied using a multiple high-speed camera arrangement. By recording the natural flame emission from three different directions the flame position inside the engine cylinder can be spatially mapped and tracked in time. Through space carving a rough estimate of the three-dimensional (3D) flame contour can be obtained. From this contour, properties like flame length and height, as well as ignition locations can be extracted. The multi-camera imaging is applied to a dual-fuel marine two-stroke engine, with a bore diameter of 0.5 m and a stroke of 2.2 m. Both liquid and gaseous fuels are directly injected at high pressure, using separate injection systems. Optical access is obtained using borescope inserts, resulting in a minimum disturbance to the cylinder geometry. In this type of engine, with fuel injection from positions at the rim of the cylinder, the flame morphology becomes asymmetric. The optical spatial mapping and tracking method is demonstrated to be well suited for the study of such an asymmetric combustion system. Spatial mapping and tracking of flame position is applied to both engine operating modes; normal diesel operation and dual-fuel operation with diesel pilot ignition of the gas. Similarities and differences between diesel and gas flame shape and development can thus be visualised directly. The effects of changing charge density, gas injection pressure and injection nozzle geometry on the flame geometry and development are also studied.</div></div>

Effects of the injection direction of pilot fuel on combustion and emissions under two-stroke HPDI dual fuel marine engine-like conditions

“…However, using two separated tables is not recommended when diesel fuel is injected into a premixed air-NG mixture. In a recent study, Hult et al [6] conducted an experimental study on the dual-fuel MAN 4T50ME-X test engine. They compared the flames of dual-fuel and a diesel engine and concluded that the flame length development is similar for two flames because the gas injection system was tuned to achieve a similar combustion rate as the diesel engine mode.…”

“…They compared the flames of dual-fuel and a diesel engine and concluded that the flame length development is similar for two flames because the gas injection system was tuned to achieve a similar combustion rate as the diesel engine mode. However, the lift-off length (which is defined in [6] as the smallest distance from injector to where soot starts form) for the gas flame has a higher value than diesel.…”