ABSTRACT
We identify the physical mechanism through which newly developed quaternary ammonium salt (QAS) deposit control additives (DCAs) affect the rheological properties of cavitating turbulent flows, resulting in an increase in the volumetric efficiency of clean injectors fuelled with diesel or biodiesel fuels. Quaternary ammonium surfactants with appropriate counterions can be very effective in reducing the turbulent drag in aqueous solutions, however, less is known about the effect of such surfactants in oil-based solvents or in cavitating flow conditions. Small-angle neutron scattering (SANS) investigations show that in traditional DCA fuel compositions only reverse spherical micelles form, whereas reverse cylindrical micelles are detected by blending the fuel with the QAS additive. Moreover, experiments utilising X-ray micro computed tomography (micro-CT) in nozzle replicas, quantify that in cavitation regions the liquid fraction is increased in the presence of the QAS additive. Furthermore, high-flux X-ray phase contrast imaging (XPCI) measurements identify a flow stabilization effect in the region of vortex cavitation by the QAS additive. The effect of the formation of cylindrical micelles is reproduced with computational fluid dynamics (CFD) simulations by including viscoelastic characteristics for the flow. It is demonstrated that viscoelasticity can reduce turbulence and suppress cavitation, and subsequently increase the injector's volumetric efficiency.
ABSTRACT
The head-to-head impact of diesel-fuel droplets on a polished spherical brass target has been investigated experimentally. High-speed imaging was employed to visualize the impact process for wall surface temperatures and Weber and Reynolds numbers in the ranges of 140-340 °C, 30-850, and 210-1135, respectively. The thermohydrodynamic outcome regimes occurring for the aforementioned ranges of parameters were mapped on a We-T diagram. Seven clearly distinguishable postimpact outcome regimes were identified, which are conventionally called the coating, splash, rebound, breakup-rebound, splash-breakup-coating, breakup-coating, and splash-breakup-rebound regimes. In addition, the effects of the Weber number and surface temperature on the wettability dynamics were examined; the temporal variations of the dynamic contact angle, dimensionless spreading diameter, and liquid film thickness forming on the solid particle were measured and are reported.
ABSTRACT
PURPOSE: The purpose of this study was to present the controversial role of adjuvant radiotherapy to a 72-year-old male patient with Masaoka stage II thymoma and coronary artery bypass and to review the relevant literature. METHODS: The data were collected by relevant studies on PubMed and EMBASE. Articles up to March 2017 were included. RESULTS: Although the radiation-induced vascular injury to the internal thoracic artery and its suitability for grafting in a patient who is candidate for coronary artery bypass is documented, the possible catastrophic effect of adjuvant radiotherapy to existing grafts in a patient with prior bypass surgery has not been fully investigated. CONCLUSION: The application of radiotherapy in a patient with R0 stage II thymoma is currently considered of 2B level of evidence but its potential occlusive effect to an underlying coronary graft may dramatically affect the survival of the patient and accordingly drop the level of evidence of its use.
