High-Speed Flow and Fuel Imaging Study of Available Spark Energy in a Spray-Guided Direct-Injection Engine and Implications on Misfires

The spark energy transferred under the highly stratified conditions during late injection in a spray-guided spark-ignition direct-injection (SG-SIDI) engine is not well characterized. The impact of high pressures, temperatures, velocities, and variations in local fuel concentration along with temporal and/or spatial variations on spark performance must be better characterized. Previous spark ignition studies have not addressed the full range of conditions that are present in SG-SIDI engines. Therefore, high-speed particle image velocimetry (PIV) experiments are conducted to characterize the spark energy dependence for a wide range of well-defined homogeneous fuel–air equivalence ratios (W50–2.9) and average air velocities (0–8m/s) in an optical SG-SIDI engine. Amoderate dependence of spark energy on equivalence ratio is shown to exist with average values of spark energy increasing by 21 per cent for the equivalence ratio range of W50–2.3. Air injection into the motored engine is used to prepare well-defined flow conditions without the complications of fuel concentration gradients that are present during fuel injection. This allows the study of the effects of velocity, shear strain rate, and vorticity on spark energy. The spark energy increases with velocity at the spark plug. This observation is consistent with findings reported in the literature for low-pressure conditions. A linear increase is shown between shear strain rate and spark energy, while vorticity and spark energy are only weakly correlated. Simultaneous high-speed PIV, planar laser-induced fluorescence, and spark-discharge electrical measurements are also performed in the optical SG-SIDI engine to measure flow properties and fuel concentrations under late injection. Operating parameters are chosen to be near peak indicated mean effective pressure performance, but they occasionally provide a random misfired or partial burned cycle. Misfired cycles occur under stoichiometric-to-lean mixtures and low velocities near the spark plug. The lower spark energies observed under these conditions are in agreement with the observationsmade under well-controlled mixture and flow conditions reported in this study. All mixture conditions found in misfiring and partially burning cycles are within the ignitability range and fall within the general population of all, predominantly well-burning, cycles. There is no predominant impact of shear strain rate and vorticity under late injection operation on misfires and partial burns.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86771/1/Sick7.pd

Using Electron Scattering Superscaling to predict Charge-changing Neutrino Cross Sections in Nuclei

Superscaling analyses of few-GeV inclusive electron scattering from nuclei are extended to include not only quasielastic processes, but now also into the region where $\Delta$-excitation dominates. It is shown that, with reasonable assumptions about the basic nuclear scaling function extracted from data and information from other studies of the relative roles played by correlation and MEC effects, the residual strength in the resonance region can be accounted for through an extended scaling analysis. One observes scaling upon assuming that the elementary cross section by which one divides the residual to obtain a new scaling function is dominated by the $N\to\Delta$ transition and employing a new scaling variable which is suited to the resonance region. This yields a good representation of the electromagnetic response in both the quasielastic and $\Delta$ regions. The scaling approach is then inverted and predictions are made for charge-changing neutrino reactions at energies of a few GeV, with focus placed on nuclei which are relevant for neutrino oscillation measurements. For this a relativistic treatment of the required weak interaction vector and axial-vector currents for both quasielastic and $\Delta$-excitation processes is presented.Comment: 42 pages, 9 figures, accepted for publication in Physical Review

Nuclear mass form factors from coherent photoproduction of π0\pi^0 mesons

Data for coherent photoproduction of $\pi^0$ mesons from nuclei ($^{12}$C, $^{40}$Ca, $^{93}$Nb, $^{nat}$Pb), recently measured with the TAPS detector at the Mainz MAMI accelerator, have been analyzed in view of the mass form factors of the nuclei. The form factors have been extracted in plane wave approximation of the $A(\gamma ,\pi^0)A$ reaction and corrected for final state interaction effects with the help of distorted wave impulse approximations. Nuclear mass rms-radii have been calculated from the slope of the form factors for $q^2\to 0$. Furthermore, the Helm model (hard sphere form factor folded with Gaussian) was used to extract diffraction radii from the zeroes of the form factor and skin thicknesses from the position and height of its first maximum. The diffraction radii from the Helm model agree with the corresponding charge radii obtained from electron scattering experiments within their uncertainties of a few per cent. The rms-radii from the slope of the form factors are systematically lower by up to 5% for PWIA and up to 10% for DWIA. Also the skin thicknesses extracted from the Helm model are systematically smaller than their charge counter parts.Comment: Accepted for publication in Eur. Phys. J.

Role of Non-Stationary Collisional Dynamics in Determining Nitric Oxide LIF Spectra

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77182/1/AIAA-2004-389-525.pd

y scaling in electron-nucleus scattering

Data on inclusive electron scattering from A = 4, 12, 27, 56, 197 nuclei at large momentum transfer are presented and analyzed in terms of y scaling. We find that the data do scale for y 1), and we study the convergence of the scaling function with the momentum transfer Q^2 and A

A high-precision polarimeter

We have built a polarimeter in order to measure the electron beam polarization in hall C at JLAB. Using a superconducting solenoid to drive the pure-iron target foil into saturation, and a symmetrical setup to detect the Moller electrons in coincidence, we achieve an accuracy of <1%. This sets a new standard for Moller polarimeters.Comment: 17 pages, 9 figures, submitted to N.I.

Pendlingens sociale geografi: Transportmiddelvalg i lyset af pendlerens politiske holdninger, sociale normer og kultur

Danske pendlere kører fortrinsvist i bil – også i store byer som København. Når rejsetiden er 20 minutter i bil var der blandt pendlere bosiddende i Hovedstaden godt 15 % cyklister, 35 % bilister og 15 % i offentlig transport. De resterende 35 % var enten til fods eller vekslede mellem forskellige transportmidler fra dag til dag. Tilsvarende ved 20 minutter var andelene blandt sjællændere godt 5 % cyklister, 55 % bilister og godt 5 % i offentlig transport. Region Nord- og Midtjylland havde begge 5 % på cykel, 75 % i bil og 5 % i offentlig transport. I Syddanmark sås ved 20 minutters rejsetid 10 % cyklister, 60 % i bil og 5 % i bus/tog. Beregningerne er baseret på data fra en spørgeskemaundersøgelse blandt 2235 pendlere. Vi estimerede elasticitet i transportmiddelvalget med hensyn til rejsetid i bil. Rejsetiderne blev beregnet ved brug af Google Maps Distance Matrix. Pendlerne var alle i beskæftigelse, 18-65 år og med samme fordeling af køn, alder, geografi og uddannelse, som den danske baggrundsbefolkning. Desuden præsenteres en typologi afpendlere, der indeholder 4 overordnede grupperinger. “Bilister uden klare holdninger” (32 %), “grønne pendlere i storbyen” (30 %), “bilister der bor uden for de store byer” (23 %) og endelig ”anti-grønne bilister” (15 %). Denne opdeling i pendler-grupperinger indeholdt overraskende få holdninger og kultur