Quantitative analysis of dribble volumes and rates using three-dimensional reconstruction of X-ray and diffused back-illumination images of diesel sprays

[EN] Post-injection fuel dribble is known to lead to incomplete atomisation and combustion due to the release of slow-moving, and often surface-bound, liquid fuel after the end of injection. This can have a negative effect on engine emissions, performance and injector durability. To better quantify this phenomenon, we developed an image-processing approach to measure the volume of ligaments produced during the end of injection. We applied our processing approach to an Engine Combustion Network 'Spray B' 3-hole injector, using datasets from 220 injections generated by different research groups, to decouple the effect of gas temperature and pressure on the fuel dribble process. High-speed X-ray phase-contrast images obtained at room temperature conditions (297 K) at the Advanced Photon Source at Argonne National Laboratory, together with diffused back-illumination images captured at a wide range of temperature conditions (293-900 K) by CMT Motores Termicos were analysed and compared quantitatively. We found a good agreement between image sets obtained by Argonne National Laboratory and CMT Motores Termicos using different imaging techniques. The maximum dribble volume within the field of view of the imaging system and the mean rate of fuel dribble were considered as characteristic parameters of the fuel dribble process. Analysis showed that the absolute mean dribble rate increases with temperature when injection pressure is higher than 1000 bar and slightly decreases at high injection pressures (>500 bar) when temperature is close to 293 K. Larger maximum volumes of the fuel dribble were observed at lower gas temperatures (similar to 473 K) and low gas pressures (<30 bar), with a slight dependence on injection pressure.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The image processing research was supported by the United Kingdom's Engineering and Physical Science Research Council (Grants EP/K020528/1 and EP/M009424/1) and BP Formulated Products Technology. The X-ray measurements were performed at the Advanced Photon Source at Argonne National Laboratory. Use of the Advanced Photon Source (APS) is supported by the U.S. Department of Energy (DOE) under Contract No. DEAC02-06CH11357. The X-ray component of this research was partially funded by DOE's Vehicle Technologies Program, Office of Energy Efficiency and Renewable Energy.Sechenyh, V.; Duke, DJ.; Swantek, AB.; Matusik, KE.; Kastengren, AL.; Powell, CF.; Viera, A.... (2020). 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An experimental investigation of gas fuel injection with X-ray radiography

In this work, an outward-opening compressed natural gas, direct injection fuel injector has been studied with single-shot X-ray radiography. Three dimensional simulations have also been performed to compliment the X-ray data. Argon was used as a surrogate gas for experimental and safety reasons. This technique allows the acquisition of a quantitative mapping of the ensemble-average and standard deviation of the projected density throughout the injection event. Two dimensional, ensemble average and standard deviation data are presented to investigate the quasi-steady-state behavior of the jet. Upstream of the stagnation zone, minimal shot-to-shot variation is observed. Downstream of the stagnation zone, bulk mixing is observed as the jet transitions to a subsonic turbulent jet. From the time averaged data, individual slices at all downstream locations are extracted and an Abel inversion was performed to compute the radial density distribution, which was interpolated to create three dimensional visualizations. The Abel reconstructions reveal that upstream of the stagnation zone, the gas forms an annulus with high argon density and large density gradients. Inside this annulus, a recirculation region with low argon density exists. Downstream, the jet transitions to a fully turbulent jet with Gaussian argon density distributions. This experimental data is intended to serve as a quantitative benchmark for simulations. (C) 2017 Elsevier Inc. All rights reserved

Gaseous jet through an outward opening injector: Details of mixing characteristic and turbulence scales

Direct injection (DI) strategy of natural gas (NG) into internal combustion engines (ICE) has led to higher thermal efficiency and lower exhaust emissions. In order to thoroughly understand the most relevant phenomena affecting the performances of such engines, computational fluid dynamics (CFD) plays a key role as an accurate description of the jet evolution and interaction within the combustion chamber is required to that aim. Accurate description of high-pressure gaseous jets is rather challenging at high Mach numbers, as the injected gas is strongly under-expanded once in the ambient, giving room to shocks due to compressibility effects. Also the interaction between shock waves and mixing layers needs to be carefully represented with a multi-dimensional model, calling for substantial computational resources requirements. In this paper a numerical investigation of the behavior of a gaseous jet (Argon) through an outward opening injector has been carried out. A Large Eddy Simulation (LES) approach has been used in order to track the structures derived by the interaction of the injected fuel with the surrounding ambient. Although already good results were obtained using a Reynolds Averaged Navier-Stokes (RANS) approach, the adoption of LES is required to characterize more accurately the jet properties in terms of vortex structures and mixing effectiveness. The effect of the Nozzle Pressure Ratio (NPR) on the jet evolution has been highlighted in the paper, showing how a higher NPR would give a faster injection process, compromising however the homogeneity of the mixture

Lycopene suppresses LPS-induced NO and IL-6 production by inhibiting the activation of ERK, p38MAPK, and NF-kappa B in macrophages

Lycopene has antioxidant, anticancer, and anti-inflammatory effects with molecular mechanisms not fully identified. We investigated the effects of lycopene on the inflammatory responses to lipopolysaccharide (LPS) in RAW264.7 cells and the signal transduction pathways involved. Lycopene inhibited LPS-induced production of nitric oxide (NO) and interleukin-6 (IL-6) with decreased mRNAs of inducible nitric oxide synthase and IL-6 but had no effect on TNF-alpha. Further study showed that lycopene also inhibited LPS-induced I kappa B phosphorylation, I kappa B degradation, and NF-kappa B translocation. Moreover, lycopene blocked the phosphorylation of ERK1/2 and p38 MAP kinase but not c-Jun NH2-terminal kinase. To confirm the causal link between MAP kinase inhibition and its anti-inflammatory effects, we treated the cells with SB 203580 and U0126. These inhibitors significantly inhibited LPS-induced NO and IL-6 formation. Lycopene inhibits the inflammatory response of RAW 264.7 cells to LPS through inhibiting ERK/p38 MAP kinase and the NF-kappa B pathway