A modified mathematical model is used to study the effects of various forces on the stability of cavitation bubbles within a diesel droplet. The principal finding of the work is that viscous forces of fluids stabilize...A modified mathematical model is used to study the effects of various forces on the stability of cavitation bubbles within a diesel droplet. The principal finding of the work is that viscous forces of fluids stabilize the cavitation bubble, while inertial force destabilizes the cavitation bubble. The droplet viscosity plays a dominant role on the stability of cavitation bubbles compared with that of air and bubble. Bubble–droplet radius ratio is a key factor to control the bubble stability, especially in the high radius ratio range. Internal hydrodynamic and surface tension forces are found to stabilize the cavitation bubble, while bubble stability has little relationship with the external hydrodynamic force. Inertia makes bubble breakup easily, however, the breakup time is only slightly changed when bubble growth speed reaches a certain value(50 m·s-1). In contrast, viscous force makes bubble hard to break. With the increasing initial bubble–droplet radius ratio, the bubble growth rate increases, the bubble breakup radius decreases, and the bubble breakup time becomes shorter.展开更多
The authors studied diesel combustion improvement with a reformed fuel that mixed nano air-bubbles by using an EMNB （ejector-type micro-nano bubbler）. The EMNB performs adequately and is smaller （20 mm diameter, 34...The authors studied diesel combustion improvement with a reformed fuel that mixed nano air-bubbles by using an EMNB （ejector-type micro-nano bubbler）. The EMNB performs adequately and is smaller （20 mm diameter, 34 mm length） than other micro-nano bubblers. It is quite possible to install it in an actual engine. An experiment was performed using a single cylinder engine with a dish or square shaped combustion chamber cavity, and in order to compare the engine speed change, we also used a four cylinder engine with a turbo-charger. The results showed that an improvement in specific fuel consumption, a decrease in the density of the exhaust smoke and an improvement in charging efficiency etc. were achieved by mixing nano bubbles into gas oil under most conditions. It is confirmed that combustion was promoted and improved by a physical and chemical action through mixing the nano bubbles into gas oil.展开更多
基金Supported by the National Natural Science Foundation of China(51276011)the National High Technology Research and Development Program of China(2013AA065303)+1 种基金Beijing Municipal Natural Science Foundation of China(3132016)the Opening Foundation of State Key Laboratory of Engines(K2013-3)
文摘A modified mathematical model is used to study the effects of various forces on the stability of cavitation bubbles within a diesel droplet. The principal finding of the work is that viscous forces of fluids stabilize the cavitation bubble, while inertial force destabilizes the cavitation bubble. The droplet viscosity plays a dominant role on the stability of cavitation bubbles compared with that of air and bubble. Bubble–droplet radius ratio is a key factor to control the bubble stability, especially in the high radius ratio range. Internal hydrodynamic and surface tension forces are found to stabilize the cavitation bubble, while bubble stability has little relationship with the external hydrodynamic force. Inertia makes bubble breakup easily, however, the breakup time is only slightly changed when bubble growth speed reaches a certain value(50 m·s-1). In contrast, viscous force makes bubble hard to break. With the increasing initial bubble–droplet radius ratio, the bubble growth rate increases, the bubble breakup radius decreases, and the bubble breakup time becomes shorter.
文摘The authors studied diesel combustion improvement with a reformed fuel that mixed nano air-bubbles by using an EMNB （ejector-type micro-nano bubbler）. The EMNB performs adequately and is smaller （20 mm diameter, 34 mm length） than other micro-nano bubblers. It is quite possible to install it in an actual engine. An experiment was performed using a single cylinder engine with a dish or square shaped combustion chamber cavity, and in order to compare the engine speed change, we also used a four cylinder engine with a turbo-charger. The results showed that an improvement in specific fuel consumption, a decrease in the density of the exhaust smoke and an improvement in charging efficiency etc. were achieved by mixing nano bubbles into gas oil under most conditions. It is confirmed that combustion was promoted and improved by a physical and chemical action through mixing the nano bubbles into gas oil.
