Combined Experimental and Numerical Investigation of the ECN Spray G under Different Engine-Like Conditions

A detailed understanding of Gasoline Direct Injection (GDI) techniques applied to spark-ignition (SI) engines is necessary as they allow for many technical advantages such as increased power output, higher fuel efficiency and better cold start performances. Within this context, the extensive validation of multi-dimensional models against experimental data is a fundamental task in order to achieve an accurate reproduction of the physical phenomena characterizing the injected fuel spray. In this work, simulations of different Engine Combustion Network (ECN) Spray G conditions were performed with the Lib-ICE code, which is based on the open source OpenFOAM technology, by using a RANS Eulerian-Lagrangian approach to model the ambient gas-fuel spray interaction. Foremost, the main scope of the activity was to identify the most accurate numerical set-up in terms of atomization ad secondary break-up models, thanks to a validation of the computed results against experimental data available for the ECN Spray G baseline condition. Specifically, attention was focused on spray penetration along with an analysis of spray morphology and effects of plume-to-plume interaction. Afterwards, the reference set-up was tested and validated under different operating conditions, characterized by detailed experimental measurements specifically provided for this work. In particular, Mie scattering and Schlieren techniques allowed the quasi-simultaneous acquisition of both vapor and liquid penetrations, while a customized image-processing procedure, developed in Matlab environment, was used for the outline of the spray contours of both fuel phases to measure the parameters characterizing the jet development. A robust reference numerical set-up was identified, capable to reproduce with good accuracy the injection process of a multi-hole GDI spray under the wide range of tested operating conditions

Quantum Backaction on kg-Scale Mirrors: Observation of Radiation Pressure Noise in the Advanced Virgo Detector

The quantum radiation pressure and the quantum shot noise in laser-interferometric gravitational wave detectors constitute a macroscopic manifestation of the Heisenberg inequality. If quantum shot noise can be easily observed, the observation of quantum radiation pressure noise has been elusive, so far, due to the technical noise competing with quantum effects. Here, we discuss the evidence of quantum radiation pressure noise in the Advanced Virgo gravitational wave detector. In our experiment, we inject squeezed vacuum states of light into the interferometer in order to manipulate the quantum backaction on the 42 kg mirrors and observe the corresponding quantum noise driven displacement at frequencies between 30 and 70 Hz. The experimental data, obtained in various interferometer configurations, is tested against the Advanced Virgo detector quantum noise model which confirmed the measured magnitude of quantum radiation pressure noise

Numerical study of the mixture formation process in a four-strokeGDI engine for two-wheel applications

Guidelines for managing the mixture formation process in a high-performance four-stroke Gasoline Direct Injection (GDI) engine for two-wheel applications are discussed, as derived from a multidimensional modelling of the in-cylinder processes. Gasoline adduction from a multi-hole injector is simulated by resorting to a properly developed model that accounts for the dependence of the initial droplets size distribution upon injection pressure. The model portability is preliminary demonstrated by comparison with experimental measurements carried out on sprays entering a confined vessel at controlled conditions. The simulation of different engine operating conditions highlights the capability to work under the so-called ‘‘mixed mode” boosting with spray guided mixture formation

Proof of Principle of a Fuel Injector Based on a Magnetostrictive Actuator

One of the goals of modern internal combustion engines is the NOx-soot trade-off, and this would be better achieved by a better control of the fuel injection. Moreover, this feature can be also useful for high-performance hydraulic systems. Actual fuel injection technology either allows only the control of the injection time or it is based on very complex mechanical-hydraulic systems, as in the case of piezo-actuators. This work describes the basic steps that brought the authors to the realization of a concept fuel injector based on a Terfenol-D magnetostrictive actuator that could overcome the previous issues, being both simple and controllable. The study provides the design, development, and a feasibility analysis of a magnetostrictive actuator for fuel injection, by providing a basic magneto-static analysis of the actuator, the adaptation of a suitable standard fuel injector, and its experimental testing in a lab environment, with different shapes and amplitude of the reference signal to follow

Experimental and numerical characterization of high-pressure spray for GDI engines

Direct-injection is now widely applied in spark-ignition engines in combination with turbocharging to reduce the fuel consumption and the knock risks. This is achieved through the use of multi-hole, high-pressure injectors whose features are rather different with respect to the hollow-cone, low-pressure configurations that were adopted in the last decade. This last aspect has to be taken into account when multi-dimensional simulations of GDI engines have to be performed. In particular, suitable models are needed to describe the spray atomization and the wall-impingement processes. In this paper experimental investigations were performed using a 6-hole injector in a constant-volume vessel with optical access. Spray images were acquired by a CCD camera and processed to obtain the spray penetration and cone angles for the different tested operating conditions. The effects of injection pressure were evaluated in the range 3.0 - 20 MPa at ambient density of the gas. A flat plate was added to the experimental apparatus for investigation of the spray-wall impingement and liquid-film images were acquired. On the basis of the experimental database, a CFD methodology for gasoline spray simulations was implemented into the Lib-ICE code, developed under the OpenFOAM technology. The evolution of the resulting liquid film was also taken into account by solving the mass and momentum equations on the mesh boundary

Experimental and Numerical Characterization of Gasoline-Ethanol Blends from a GDI Multi-Hole Injector by Means of Multi-Component Approach

This paper reports an experimental and numerical investigation of the spray structure development for pure gasoline fuel and two different ethanol-gasoline blends (10% and 85% ethanol). A numerical methodology has been developed to improve the prediction of the pure and blends fuel spray. The fuel sprays have been simulated by means of a 3D-CFD code, adopting a multi-component approach for the fuel simulations. The vaporization behavior of the real fuel has been improved testing blends of 7 hydrocarbons and a reduced multi-component model has been defined in order to reduce the computational cost of the CFD simulations. Particular care has been also dedicated to the modeling of the atomization and secondary breakup processes occurring to the GDI sprays. The multi-hole jets have been simulated by means of a new atomization approach combined with the Kelvin-Helmholtz/Rayleigh-Taylor hybrid model. At the nozzle hole exit an initial distribution of atomized droplets has been predicted by the numerical approach taking into account cavitation phenomena and turbulent effects. Sprays have been investigated using a 6-hole gasoline direct-injection (GDI) injector and injecting fuel into an optically-accessible constant volume vessel at 5.0, 10.0, and 15.0 MPa of injection pressure, at ambient back pressure. Mie-scattering images have been performed using a high-speed camera and a pulsed-wave flash system which is able to track liquid phase in order to estimate the spray development, morphology and cone angle. Moreover fuel injection rates measurements have been carried out using a meter working on the Bosch tube principle to characterize the injected mass. The liquid fuel penetration registered highest values for gasoline fuel with respect to its blends with ethanol at different percentages