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Technical Paper

Measurement of Soot Concentration in a Prototype Multi-Hole Diesel Injector by High-Speed Color Diffused Back Illumination Technique

2017-10-08
2017-01-2255
A prototype multi-hole diesel injector operating with n-heptane fuel from a high-pressure common rail system is used in a high-pressure and high-temperature test rig capable of reaching 1100 Kelvin and 150 bar under different oxygen concentrations. A novel optical set-up capable of visualizing the soot cloud evolution in the fuel jet from 30 to 85 millimeters from the nozzle exit with the high-speed color diffused back illumination technique is used as a result of the insertion of a high-pressure window in the injector holder opposite to the frontal window of the vessel. The experiments performed in this work used one wavelength provide information about physical of the soot properties, experimental results variating the operational conditions show the reduction of soot formation with an increase in injection pressure, a reduction in ambient temperature, a reduction in oxygen concentration or a reduction in ambient density.
Technical Paper

Assessment on Internal Nozzle Flow Initialization in Diesel Spray Simulations

2015-04-14
2015-01-0921
Proper initial conditions are essential to successfully perform a simulation, especially for highly transient problems such as Diesel spray injection. Until now, no much attention has been paid to the internal nozzle flow initialization because spray simulations are usually decoupled from the nozzle. However, new homogeneous models like Eulerian Spray Atomization (ESA) model allow to simulate the internal nozzle flow and the spray seamlessly. Therefore, the behavior of the spray for the first microseconds is highly influenced by the initial conditions inside the nozzle. Furthermore, last experiments confirm the presence of gas inside the nozzle between successive injections. This work deals with the initialization procedure in a way that mass flow rate and spray penetration curves are well predicted by the model.
Technical Paper

Transient Rate of Injection Effects on Spray Development

2013-09-08
2013-24-0001
Transients in the rate of injection (ROI) with respect to time are ever-present in direct-injection engines, even with common-rail fueling. The shape of the injection ramp-up and ramp-down affects spray penetration and mixing, particularly with multiple-injection schedules currently in practice. Ultimately, the accuracy of CFD model predictions used to optimize the combustion process depends upon the accuracy of the ROI utilized as fuel input boundary conditions. But experimental difficulties in the measurement of ROI, as well as real-world affects that change the ROI from the bench to the engine, add uncertainty that may be mistaken for weaknesses in spray modeling instead of errors in boundary conditions. In this work we use detailed, time-resolved measurements of penetration at the Spray A conditions of the Engine Combustion Network to rigorously guide the necessary ROI shape required to match penetration in jet models that allow variable rate of injection.
Journal Article

Schlieren Methodology for the Analysis of Transient Diesel Flame Evolution

2013-09-08
2013-24-0041
Schlieren/shadowgraphy has been adopted in the combustion research as a standard technique for tip penetration analysis of sprays under diesel-like engine conditions. When dealing with schlieren images of reacting sprays, the combustion process and the subsequent light emission from the soot within the flame have revealed both limitations as well as considerations that deserve further investigation. Seeking for answers to such concerns, the current work reports an experimental study with this imaging technique where, besides spatial filtering at the Fourier plane, both short exposure time and chromatic filtering were performed to improve the resulting schlieren image, as well as the reliability of the subsequent tip penetration measurement. The proposed methodology has reduced uncertainties caused by artificial pixel saturation (blooming).
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