On the formation of string cavitation inside fuel injectors

The formation of vortex or ‘string’ cavitation has been visualised in the flow upstream of the injection hole inlet of an automotive-sized optical diesel fuel injector nozzle operating at pressures up to 2,000 bar. Three different nozzle geometries and three-dimensional flow simulations have been employed to describe how, for two adjacent nozzle holes, their relative positions influenced the formation and hole-to-hole interaction of the observed string cavitation vortices. Each hole was shown to contain two counter-rotating vortices: the first extending upstream on axis with the nozzle hole into the nozzle sac volume and the second forming a single ‘bridging’ string linked to the adjacent hole. Steady-state and transient fuel injection conditions were shown to produce significantly different nozzle-flow characteristics with regard to the formation and interaction of these vortices in the geometries tested, with good agreement between the experimental and simulation results being achieved. The study further confirms that the visualised vortices do not cavitate themselves but act as carriers of gas-phase components within the injector flow

‘Here to support anybody who needs to come’? An investigation of the provision for EAL pupils in secondary school libraries in England

This paper presents the findings of a mixed methods investigation of the effectiveness of provision for EAL pupils by secondary school libraries in England. Data from a quantitative survey of secondary school librarians are triangulated with those of qualitative interviews with staff responsible for EAL provision. A picture emerges of a hybrid environment which addresses a number of the educational, cultural and social needs of EAL learners, but in which a series of barriers to effective provision are also identified. Recommendations are made to key stakeholder groups for the short and long term improvement of EAL provision, and for further research

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

The flow inside a purpose built enlarged single-orifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and high-speed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can be a reliable tool for cavitation in nozzle orifices operating under nominal steady-state conditions

Simulation of Cavitating Flows in Diesel Injectors

International audienceWith a new two fluid model it is possible to carry out three-dimensional CFD calculations of cavitating flows in hydraulic components of Diesel injection systems. As model geometries a ball valve, a sac-hole nozzle and a one-hole nozzle have been used to test the applicability of the method. Calculations of the ensemble averaged volume fraction show the distribution of cavitation zones. Force calculations were in good agreement with the experiment. With this new tool, the design of new components can be improved

Luteinizing hormone induces mouse vas deferens protein expression in the murine ovary

The aim of our study was to isolate and identify novel proteins that are involved in the process of ovulation. To achieve this goal we used the technique of proteome analysis. Comparison of ovary protein patterns, obtained by high resolution two-dimensional gel electrophoresis from recombinant FSH (rFSH)- and rFSH + human CG (hCG)-treated mice, showed significant differences in protein spot positions and intensities. Subsequent analysis of one of these proteins was performed by mass spectrometry, resulting in the identification of the mouse vas deferens protein (MVDP). MVDP, which was absent in the two-dimensional gel electrophoresis protein pattern of rFSH-primed mice and appeared 3 h aider the hCG surge, is a member of the aldo-keto reductase superfamily and was originally identified in the mouse vas deferens. This is the first study describing MVDP expression and regulation by LH in the ovary. Northern blot analysis of female mice tissues showed that mvdp messenger RNA (mRNA) was only present in adrenal glands and in hCG-treated ovaries. In situ hybridization studies localized the mvdp mRNA unequivocally to ovarian thecal and interstitial cells with an expression profile starting already 1.5 h, and decreasing 24 h, after LH treatment. In the adrenal glands, mvdp mRNA was not regulated by LH and localized in the cells of the zona fasciculata. In murine adrenocortical cells, a recent study proposed a detoxifying role of MVDP, MVDP might fulfill the same function in the ovary; however, because of its strong and early transcriptional induction by LH, it is also possible that MVDP catalyses another important step during the cascade of events occurring at the time of ovulation

Simulation of Cavitating Flows in Diesel Injectors

With a new two fluid model it is possible to carry out three-dimensional CFD calculations of cavitating flows in hydraulic components of Diesel injection systems. As model geometries a ball valve, a sac-hole nozzle and a one-hole nozzle have been used to test the applicability of the method. Calculations of the ensemble averaged volume fraction show the distribution of cavitation zones. Force calculations were in good agreement with the experiment. With this new tool, the design of new components can be improved