Experimental Study of Biodiesel Spray and Combustion Characteristics

In this paper, the spray and combustion characteristics of biodiesel and diesel were investigated. The spray pictures of single injection, by means of a diesel pump test-bed, were taken by a high-speed camera video system in an atmospheric condition, and the effects of the pump speed, nozzle orifice diameter and nozzle opening pressure on the fuel spray structure and characteristics were studied under atmosphere condition. The results showed that the general law of biodiesel spray characteristics was similar to that of diesel. However, the spray penetration of biodiesel was longer than that of diesel, and the spray angles of biodiesel were only half angle of diesel.

The experiment of combustion characteristics was conducted in a vitiated coflow combustor with the same diesel pump test-bed. The images of combustion flame were recorded by the high-speed camera system. Then the ignition characteristics were evaluated from the digital pictures by computer. Simultaneously, the transient emission of the combustion (NO and THC) was measured by the fNOX400 and HFR500 from the Cambustion Ltd. The results showed that ignition delay and flame structure of biodiesel were different from that of diesel, and the transient emission characteristics showed that THC and NO in the biodiesel flame are lower than that in diesel flame.