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Technical Paper

Research into Autoignition Characteristics of Diesel Fuel in a Controllable Active Thermo-Atmosphere

2006-04-03
2006-01-0073
A novel method is applied to analysis the autoignition phenomenon. Experiments on the study of autoignition characteristics of diesel fuel were carried out with a Controllable Active Thermo-Atmosphere Combustor. The results show that the method for autoignition studying of liquid fuel is of feasibility. Autoignition delay time and autoignition height from the nozzle increase with the coflow temperature decreasing and autoignition delay time changes sensitively under lower coflow temperature. Liftoff height of diesel spray flame decreases with the increasing of coflow temperature. Lower temperature causes higher variance of liftoff height. It might be speculated that there are two different mechanisms of flame stabilization that the lower lift-off heights flames are related to a balance between the flow velocity and flame speed while the higher lift-off heights flames are stabilized by the mixture autoignition.
Technical Paper

Experimental Study of Biodiesel Spray and Combustion Characteristics

2006-10-16
2006-01-3250
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.
Technical Paper

Evaporation Characteristics of n-Heptane Droplet Streams in a Heated Air Channel Flow

2016-04-05
2016-01-0843
An experimental study is presented on the evaporation of diluted droplet-laden two-phase jet flows within a heated air channel co-flow. In this study, n-heptane is pre-atomized by an ultrasonic nozzle to produce droplet cluster with a median diameter of about15μm, and a continuous cold air flow is applied to carry the fuel droplet cluster to emerge from a nozzle tube, producing a free turbulent jet of droplet stream. The droplet stream is then introduced as a central jet into a square-shaped channel with heated air co-flow for evaporation investigations. With flexibilities of the initial properties of droplet stream and surrounding conditions of channel flow, the axial evolution of droplet size is determined to characterize the evaporation behavior of n-heptane droplet stream under various boundary conditions. The equivalence ratios of droplet streams are varied by changing both the carrier-air flow rate and the fuel flow rate.
Technical Paper

Effect of Nozzle Geometry on Macroscopic Behavior of Diesel Spray in the Near-Nozzle Field

2013-04-08
2013-01-1587
In this study, the orifice inlet rounding radii of four diesel nozzles with different hydro erosive grinding time were measured based on the x-ray CT scan technology provided by Shanghai Synchrotron Radiation Facility (SSRF), and a wide parametrical study of the spray macroscopic behavior in the first 18 mm from the nozzle tip have been carried out with high speed camera. And then the influence of orifice inlet rounding radius on the spray behavior in the near-nozzle field was thoroughly investigated. The investigation results show that: the mean values of orifice inlet rounding radii of different nozzles are measured to be on the order of 21.5-56.8 μm. Although the spray tip penetrations of different nozzles tend to increase with the hydro erosive grinding time through statistical analyzing method, the variations of penetration from nozzles are less than 15% according to different hydro erosive grinding timing.
Technical Paper

Development and Evaluation of the Performance Characteristics of a Poly-Disperse Droplet Stream Generator

2013-04-08
2013-01-1617
A specially designed generator has been developed to produce poly-disperse droplet streams: A liquid fuel (n-heptane) is metered to an ultrasonic atomizer to produce droplets, which are then carried and accelerated vertically upwards through a nozzle tube by carrier-air flow. Conditions of the streams at the nozzle exit are modulated by varying the length of nozzle tubes, the fuel and carrier-air flow rate. Optical measurement techniques such as direct photography method, schlieren photography and particle image velocimetry (PIV) are employed to characterize its performance characteristics. Effects of the nozzle tube length, the carrier-air and fuel flow rate are investigated to evaluate the performance of the generator. Longer nozzle tubes provide a better flow guidance for the carrier-air, and tend to generate streams with less and smaller droplets due to the transporting losses.
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