Understanding fuel-injection processes is important for improving combustion in compression-ignition engines. To understand and model injection processes in detail, it is necessary to measure the instantaneous mass flow rate of fuel through each orifice of the injector nozzle. Due to constraints from injector design and operation, injection rate is typically measured downstream from the orifice exit. Measuring injection rate from a multi-orifice nozzle adds several geometric constraints, particularly when measuring fuel flow from a single orifice. The injection ratemeter discussed in this paper is designed to fit inside an optical research engine so that the injection rate can be measured without having to place the injector in an external fixture. The injection rate is calculated from a measurement of the momentum flux of a jet of fuel impinging upon the surface of a piezoelectric force (or pressure) transducer, combined with a measurement of the quantity of fuel injected, as demonstrated previously [1–3]. The ratemeter includes a thermal shield to limit the effects of temperature fluctuations on the transducer output. Data were acquired for one injector nozzle at several different injection durations and compared to results from literature for similar injector designs. Estimates for the uncertainty of the measured injection rates are provided and the calibration technique used is presented.
The Prime Focus Spectrograph (PFS) is an optical/near-infrared multi-fiber spectrograph with 2394 science fibers, which are distributed in 1.3 degree diameter field of view at Subaru 8.2-meter telescope. The simultaneous wide wavelength coverage from 0.38 μm to 1.26 μm, with the resolving power of 3000, strengthens its ability to target three main survey programs: cosmology, Galactic archaeology, and galaxy/AGN evolution. A medium resolution mode with resolving power of 5000 for 0.71 μm to 0.89 μm also will be available by simply exchanging dispersers. PFS takes the role for the spectroscopic part of the Subaru Measurement of Images and Redshifts (SuMIRe) project, while Hyper Suprime-Cam (HSC) works on the imaging part. HSC's excellent image qualities have proven the high quality of the Wide Field Corrector (WFC), which PFS shares with HSC. The PFS collaboration has succeeded in the project Preliminary Design Review and is now in a phase of subsystem Critical Design Reviews and construction.To transform the telescope plus WFC focal ratio, a 3-mm thick broad-band coated microlens is glued to each fiber tip. The microlenses are molded glass, providing uniform lens dimensions and a variety of refractive-index selection. After successful production of mechanical and optical samples, mass production is now complete. Following careful investigations including Focal Ratio Degradation (FRD) measurements, a higher transmission fiber is selected for the longest part of cable system, while one with a better FRD performance is selected for the fiber-positioner and fiber-slit components, given the more frequent fiber movements and tightly curved structure. Each Fiber positioner consists of two stages of piezo-electric rotary motors. Its engineering model has been produced and tested. After evaluating the statistics of positioning accuracies, collision avoidance software, and interferences (if any) within/between electronics boards, mass production will commence. Fiber positioning will be performed iteratively by taking an image of artificially backilluminated fibers with the Metrology camera located in the Cassegrain container. The camera is carefully designed so that fiber position measurements are unaffected by small amounts of high special-frequency inaccuracies in WFC lens surface shapes.Target light carried through the fiber system reaches one of four identical fast-Schmidt spectrograph modules, each with three arms. All optical glass blanks are now being polished. Prototype VPH gratings have been optically tested. CCD production is complete, with standard fully-depleted CCDs for red arms and more-challenging thinner fully-depleted CCDs with blue-optimized coating for blue arms. The active damping system against cooler vibration has been proven to work as predicted, and spectrographs have been designed to avoid small possible residual resonances.
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