Search Results

In this study, it is purpose to make clear the effect of cavitation phenomenon on the spray atomization. In this report, the cavitation phenomenon inside the nozzle hole was visualized and the pressure measurements along the wall of the nozzle hole were carried out by use of 25-times enlarged acrylic nozzle. For the representatives of regular gasoline, single and two-component fuels were used as a test fuel. In addition, various cavitating flow patterns same as experimental conditions were simulated by use of Barotropic model incorporated in commercial code of Star-CD scheme, and compared with experimental results.

In this study, the purpose is placed in analysis the structure of diesel spray and, especially, making clear the mixture formation process in the evaporative diesel spray. The liquid fuel was injected from a single-hole nozzle (1/d = 1.0 mm/0.2 mm) into a constant-volume vessel possessing phenomena visualization under high pressure and temperature field. As for measurement method, in order to investigate liquid and vapor-phase of injected spray, exciplex fluorescence method was applied in the evaporative fuel spray. And the interested view region in injected spray is the downstream spray. For the minute investigation of spray flow, the liquid and vapor-phase region is taken with 35 mm still camera and CCD camera, respectively.

A phenomenological or empirical model based on experimental results obtained from various optical measurements is critical for the understanding of DI diesel combustion phenomena as well as for the improvement of its emission characteristics. Such a model could be realized by the application of advanced optical measurement, which is able to isolate a particular phenomenon amongst complicated physical and chemical interactions, to a DI diesel combustion field. The authors have conducted experimental studies to clarify the combustion characteristics of unsteady turbulent diffusion flames in relation to the soot formation and oxidation process in a small-sized DI diesel engine. In the present study, the effect of fuel vapor concentration on the process of early combustion and soot formation has been investigated using several optical measurements.

An unsteady single spray of n-tridecane which was mixed with a small quantity of exciplex - forming dopants, that is naphthalene and TMPD, was impinged on a flat wall surface with high temperature of 550 K at a normal angle. These experiments were carried out in a quiescent N2 atmosphere with high temperature of 700 K and high pressure of 2.5 MPa. It was possible to generate the fluorescence emissions from the vapor and liquid phases in this spray, when a laser light sheet from a Nd:YAG laser was passing through the cross section of the spray containing its central axis. Then, clear 2 - D images of vapor and liquid phases in the spray were acquired simultaneously by this method. And, the vapor concentration was analyzed quantitatively by applying Lambert - Beer's law to the measured TMPD monomer fluorescence intensity from vapor phase, and by correcting the intensity for the effect of the quenching process due to the ambient temperature and fuel concentration.

The combustion of a diesel spray includes very complex processes, that is, atomization, evaporation, diffusion, turbulent mixing and burning. On the other hand, there are no phenomena of atomization and evaporation in the combustion of a transient gas jet. However, the latter jet can be treated as a fundamental of the former spray. From the standpoint mentioned above, acetylene gas was injected into the ambient during short duration as a transient gas jet and its flow characteristics were investigated by means of photography with a sheet of laser light and LDV to detect the turbulent vortex generated in the boundary layer between it and surroundings, in the experiments presented here. And the experimental results show that the jet itself is divided into four peculiar regions and the modelling of each region is carried out by use of the results to understand the mixture formation process owing to the turbulent diffusive mixing.

The authors have explored the potential of fuel to control spray and its combustion processes in a diesel engine. Fuel has some potential for low emission and high thermal efficiency because its volatility and ignitability are one of the ultimate performing factors of the engines. In present study, the ignition process of mixed fuel spray was investigated in a constant volume combustion vessel and in a rapid compression and expansion machine, The ignition delay based on the diagram of rate of the heat release, the imaging of natural flame emissions and the numerical simulation were carried out to clarify the effect of the physical and chemical properties of mixed fuel on ignition characteristics.