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A 2D finite element program, known as FAST_FORM2D, was developed at FTI to carry out section analysis in die design. Incremental method is employed and plane strain condition is assumed for 2D sections. Contact behavior and friction force are simulated by a developed algorithm. Therefore, the divergence problems related to the conventional contact techniques can be reduced or avoided. An adaptive mesh generation scheme is implemented to achieve computation efficiency. With the code, it is possible to evaluate tension, strain, thickness distributions and punch force at different stages for any 2D section cut from 3D panels. User can easily input or modify forming conditions to get the best solution.

Multi-hole DI injectors are being adopted in the advanced downsized DISI ICE powertrain in the automotive industry worldwide because of their robustness and cost-performance. Although their injector design and spray resembles those of DI diesel injectors, there are many basic but distinct differences due to different injection pressure and fuel properties, the sac design, lower L/D aspect ratios in the nozzle hole, closer spray-to-spray angle and hense interactions. This paper used Phase-Contrast X ray techniques to visualize the spray near a 3-hole DI gasoline research model injector exit and compared to the visible light visualization and the internal flow predictions using with multi-dimensional multi-phase CFD simulations. The results show that strong interactions of the vortex strings, cavitation, and turbulence in and near the nozzles make the multi-phase turbulent flow very complicated and dominate the near nozzle breakup mechanisms quite unlike those of diesel injections.

The fuel spray behavior in the near nozzle region of a gasoline injector is challenging to predict due to existing pressure gradients and turbulences of the internal flow and in-nozzle cavitation. Therefore, statistical parameters for spray characterization through experiments must be considered. The characterization of spray velocity fields in the near-nozzle region is of particular importance as the velocity information is crucial in understanding the hydrodynamic processes which take place further downstream during fuel atomization and mixture formation. This knowledge is needed in order to optimize injector nozzles for future requirements. In this study, the results of three experimental approaches for determination of spray velocity in the near-nozzle region are presented. Two different injector nozzle types were measured through high-speed shadowgraph imaging, Laser Doppler Anemometry (LDA) and X-ray imaging.

A time-resolved x-radiographic technique has been employed for measuring the fuel distribution close to a single-hole nozzle fitted in a high-pressure diesel injector. Using a monochromatic synchrotron x-ray beam, it is possible to perform quantitative x-ray absorption measurements and obtain two-dimensional projections of the mass of the fuel spray. We have completed a series of spray measurements in the optically dense, near-nozzle region (< 15 mm from the nozzle orifice) under ambient pressures of 1, 2, and 5.2 bar N2 and 1 bar SF6 at room temperature with injection pressures of 500 and 1000 bar. The focus of the measurements is on the dynamical behaviors of the fuel jets with an emphasis on their penetration in the near-nozzle region. Careful analysis of the time-resolved x-radiographic data revealed that the spray penetration in this near nozzle region was not significantly affected by the limited change of the ambient pressure.

The performance of Gasoline Direct Injection (GDI) engines is governed by multiple physical processes such as the internal nozzle flow and the mixing of the liquid stream with the gaseous ambient environment. A detailed knowledge of these processes even for complex injectors is very important for improving the design and performance of combustion engines all the way to pollutant formation and emissions. However, many processes are still not completely understood, which is partly caused by their restricted experimental accessibility. Thus, high-fidelity simulations can be helpful to obtain further understanding of GDI injectors. In this work, advanced simulation and experimental methods are combined in order to study the spray characteristics of two different 3-hole GDI injectors.

Stringent emission standards are driving the development of diesel-fuel injection concepts to mitigate in-cylinder formation of particulates. While research has demonstrated significant reduction in particulate formation using micro-orifice technology, implementation requires development of industrial processes to fabricate micro-orifices with diameters as low as 50 μm and with large length-to-diameter ratios. This paper reviews the different processes being pursued to fabricate micro-orifices and the advanced techniques applied to characterize the performance of micro-orifices. The latter include the use of phase-contrast x-ray imaging of electroless nickel-plated micro-orifices and laser imaging of fuel sprays at elevated pressures. The experimental results demonstrate an industrially viable process to create small uniform orifices that improve spray formation for fuel injection.

Improvement of spray atomization and penetration characteristics of the gasoline direct-injection (GDi ) multi-hole injector is a critical component of the GDi combustion developments, especially in the context of engine down-sizing and turbo-charging trend that is adopted in order to achieve the European target CO₂, US CAFE, and concomitant stringent emissions standards. Significant R&D efforts are directed towards optimization of the nozzle designs, in order to improve the GDi multi-hole spray characteristics. This publication reports VOF-LES analyses of GDi single-hole skew-angled nozzles, with β=30° skew (bend) angle and different nozzle geometries. The objective is to extend previous works to include the effect of nozzle-hole skew angle on the nozzle flow and spray primary breakup. VOF-LES simulations of a single nozzle-hole of a purpose-designed GDi multi-hole seat geometry, with three identical nozzle-holes per 120° seat segment, are performed.

The process of spray atomization has typically been understood in terms of the Rayleigh-Taylor instability theory. However, this mechanism has failed to fully explain much of the measured data. For this reason a number of new atomization mechanisms have been proposed. The present study intends to gain an understanding of the spray dynamics and breakup processes in the near-nozzle region of heavy-duty diesel injector sprays. As this region is optically dense, synchrotron x-rays were used to gain new insights. This spray study was performed using a prototype common-rail injection system, by injecting a blend of diesel fuel and cerium-containing organometalic compound into a chamber filled with nitrogen at 1 atm. The x-rays were able to probe the dense region of the spray as close as 0.2 mm from the nozzle. These x-ray images showed two interesting features. The first was a breakup of the high density region about 22 μs After the Start Of Injection (ASOI).

By taking advantage of high-intensity and high-brilliance x-ray beams available at the Advanced Photon Source (APS), ultrafast (150 ps) propagation-based phase-enhanced imaging was developed to visualize high-pressure high-speed diesel sprays in the optically dense near-nozzle region. The sub-ns temporal and μm spatial resolution allows us to capture the morphology of the high-speed fuel sprays traveling at 500 m/s with a negligible motion blur. Both quality and quantitative information about the spray feature can be readily obtained. In the experiment, two types of single-hole nozzles have been used, one with a hydroground orifice inlet and the other with a sharp one. Within 3 mm from the nozzle, the sprays from these nozzles behave differently, ranging from laminar flow with surface instability waves to turbulent flow. The sprays are correlated with the nozzle internal geometry, which provides practical information for both nozzle design and supporting numerical simulation models.

Most previous measurements of diesel sprays have yielded few details regarding the near-nozzle structure of the sprays. X-ray radiography measurements have provided quantitative, time-resolved measurements of spray behavior, but the radiography data are projections of the actual fuel distribution. In this study, diesel sprays from two axial, single-hole nozzles are measured using x-ray radiography from several viewing angles. A model-based reconstruction is used to determine the actual density distribution from the projected data. The spray from the hydroground nozzle is eccentric and relatively dense, while the spray from the non-hydroground nozzle is asymmetric and far less dense. Even several mm from the nozzles, the calculated density values are high enough to call into question the assumptions underlying many standard CFD spray models.

Propagation-based and phase-enhanced x-ray imaging was developed as a unique metrology technique to visualize the internal structure of high-pressure fuel injection nozzles. We have visualized the microstructures inside 200-μm fuel injection nozzles in a 3-mm-thick steel housing using this novel technique. Furthermore, this new x-ray-based metrology technique has been used to directly study the highly transient needle motion in the nozzles in situ and in real-time, which is virtually impossible by any other means. The needle motion has been shown to have the most direct effect on the fuel jet structure and spray formation immediately outside of the nozzle. In addition, the spray cone-angle has been perfectly correlated with the numerically simulated fuel flow inside the nozzle due to the transient nature of the needle during the injection.

In order to analyze the effects of nozzle geometry on the structure of fuel sprays, quantitative x-ray measurements have been performed on sprays from nozzles with different degrees of hydro-grinding. The two nozzles were measured at injection pressures of 500 and 1000 bar in an ambient environment of 1 bar nitrogen gas. Time-resolved x-radiography was used to measure the two-dimensional mass distributions of the spray as a function of time for the entire spray event. The initial mass flow through the nozzles was determined from the x-ray data, the nozzles showed no appreciable differences in the early part of the injection event. The transverse mass distributions were fit with Gaussian curves, and the assumption of axisymmetry was used to calculate the volume fraction of each spray. It was observed that the nozzle which had undergone extensive hydro-grinding generated a more dense spray than the sharp-edged nozzle at an injection pressure of 1000 bar.

A quantitative and time-resolved technique has been developed to probe the fuel distribution very near the nozzle of a high-pressure diesel injector. This technique uses the absorption of synchrotron x-rays to measure the fuel mass with good time and position resolution. The penetrating power of x-rays allows measurements that are difficult with other techniques, such as quantitative measurements of the mass and penetration measurements of the trailing edge of the spray. Line-of-sight measurements were used to determine the fuel density as a function of time. The high time resolution and quantitative nature of the measurement also permit an accurate measure of the instantaneous mass flow rate through the nozzle.