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Arcoumanis, C.
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Fuel Film Behavior Analysis Using Simulated Intake Port

SAE International Journal of Engines

City University London, UK-G. Wang, C. Arcoumanis
Yamaha Motor Co. LTD-Minoru Iida, Keiichi Yoshikawa, Hiroshi Tanaka
  • Journal Article
  • 2009-32-0129
Published 2009-11-03 by Society of Automotive Engineers of Japan in Japan
Transient behavior of the engine is one of the most crucial factors for motorcycle features. Characterization of the fuel film with port fuel injection (PFI) is necessary to enhance this feature with keeping others, such as high output, low emissions and good fuel consumption. In order to resolve the complicated phenomena in real engine condition into simple physical issues, a simulated intake port was used in our research with Laser Induced Fluorescence (LIF) technique to allow accurate measurement of the fuel film thickness, complemented by visualization of the film development and spray behavior using high-speed video imaging. Useful results have been conducted from the parametric studies with various sets of conditions, such as injection quantity, air velocity and port backpressure.
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Evaluation of the Predictive Capability of Diesel Nozzle Cavitation Models

Delphi Diesel Systems-C. Soteriou, W. Tang
The City University London-E. Giannadakis, D. Papoulias, M. Gavaises, C. Arcoumanis
Published 2007-04-16 by SAE International in United States
The predictive capability of Lagrangian and Eulerian multi-dimensional computational fluid dynamics models accounting for the onset and development of cavitation inside Diesel nozzle holes is assessed against experimental data. These include cavitation images available from a real-size six-hole mini-sac nozzle incorporating a transparent window as well as high-speed/CCD images and LDV measurements of the liquid velocity inside an identical large-scale fully transparent nozzle replica. Results are available for different cavitation numbers, which correspond to different cavitation regimes forming inside the injection hole. Discharge coefficient measurements for various real-size nozzles operating under realistic injection pressures are also compared and match well with models' predictions.The calculations performed have indicated that the two Eulerian models predict a large void zone inside the injection hole and fail to capture the transition from incipient to fully developed cavitation, while the Lagrangian model predicts a more diffused and gradual vapour distribution in agreement with the experimental data. However, all models have predicted similarly the velocity increase inside the injection hole caused by the presence of vapour, and a similar reduction in…
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Spray Structure Generated by Multi-Hole Injectors for Gasoline Direct-Injection Engines

The City University, London, UK-N. Mitroglou, J. M. Nouri, Y. Yan, M. Gavaises, C. Arcoumanis
Published 2007-04-16 by SAE International in United States
The performance of multi-hole injectors designed for use in second-generation direct-injection gasoline engines has been characterised in a constant-volume chamber. Two types of multi-hole injector have been used: the first has 11 holes, with one hole on the axis of the injector and the rest around the axis at 30 degrees apart, and the second has 6 asymmetric holes located around the nozzle axis. Measurements of droplet axial and radial velocity components and their diameter were obtained using a 2-D phase Doppler anemometer (PDA) at injection pressures up to 120 bar, chamber pressures from atmospheric to 8 bar, and ambient temperatures. Complementary spray visualisation made use of a pulsed light and a CCD camera synchronised with the injection process.Comparison of the results between the two injectors has allowed quantification of the influence of the number of holes and nozzle length-to-diameter ratio on the spray structure and spray tip penetration, droplet velocity and size distribution as a function of injection and chamber pressures of relevance to gasoline passenger cars.
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Internal Flow and Cavitation in a Multi-Hole Injector for Gasoline Direct-Injection Engines

The City University, London, UK-J. M. Nouri, N. Mitroglou, Y. Yan, C. Arcoumanis
Published 2007-04-16 by SAE International in United States
A transparent enlarged model of a six-hole injector used in the development of emerging gasoline direct-injection engines was manufactured with full optical access. The working fluid was water circulating through the injector nozzle under steady-state flow conditions at different flow rates, pressures and needle positions. Simultaneous matching of the Reynolds and cavitation numbers has allowed direct comparison between the cavitation regimes present in real-size and enlarged nozzles. The experimental results from the model injector, as part of a research programme into second-generation direct-injection spark-ignition engines, are presented and discussed. The main objective of this investigation was to characterise the cavitation process in the sac volume and nozzle holes under different operating conditions. This has been achieved by visualizing the nozzle cavitation structures in two planes simultaneously using two synchronised high-speed cameras.Imaging of the flow inside the injector nozzle identified the formation of three different types of cavitation as a function of the cavitation number, CN. The first is needle cavitation, formed randomly at low CN (0.5-0.7) in the vicinity of the needle, which penetrates into…
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Internal Flow and Spray Characteristics of Pintle-Type Outwards Opening Piezo Injectors for Gasoline Direct-Injection Engines

The City University, London, UK-A. Marchi, J. M. Nouri, Y. Yan, C. Arcoumanis
Published 2007-04-16 by SAE International in United States
The near nozzle exit flow and spray structure generated by an enlarged model of a second generation pintle type outwards opening injector have been investigated under steady flow conditions as a function of flow-rate and needle lift. A high resolution CCD camera and high-speed video camera have been employed in this study to obtain high-magnification images of the internal nozzle exit flow in order to identify the origin of string ligaments/droplets formation at the nozzle exit. The images of the flow around the nozzle seat area showed clearly that air was entrained from outside into the nozzle seat area under certain flow operating conditions (low cavitation number, CN); the formed air pockets inside the annular nozzle proved to be the main cause of the breaking of the fuel liquid film into strings as it emerged from the nozzle with a structure consisting of alternating thin and thick liquid filaments. As the flow rate increased, the air pockets were suppressed, reduced in size and pushed towards the exit of the nozzle resulting in a smoother spray.The…
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Prediction of Liquid and Vapor Penetration of High Pressure Diesel Sprays

Fluid Research Co-A. Theodorakakos
School of Engineering and Mathematical Sciences, City University-S. Tonini, M. Gavaises, C. Arcoumanis
Published 2006-04-03 by SAE International in United States
A dense-particle Eulerian-Lagrangian stochastic methodology, able to resolve the dense spray formed at the nozzle exit has been applied to the simulation of evaporating diesel sprays. Local grid refinement at the area where the spray evolves allows use of cells having sizes from 0.6 down to 0.075mm. Mass, momentum and energy source terms between the two phases are spatially distributed to cells found within a distance from the droplet centre; this has allowed for grid-independent interaction between the Eulerian and the Lagrangian phases to be reached. Additionally, various models simulating the physical processes taking place during the development of sprays are considered. The cavitating nozzle flow is used to estimate the injection velocity of the liquid while its effect on the spray formation is considered through an atomisation model predicting the initial droplet size. Various vaporisation models have been tested, including high-pressure and non-equilibrium effects and chemical composition change. Different droplet break-up and droplet aerodynamic drag models are used to assess the predicted results. In particular, the increased surface area of the droplets associated with…
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Effect of Multi-Injection Strategy on Cavitation Development in Diesel Injector Nozzle Holes

School of Engineering & Mathematical Sciences, City University, London, UK-H. Roth, E. Giannadakis, M. Gavaises, C. Arcoumanis
Toyota Motor Corporation, Japan-K. Omae, I. Sakata, M. Nakamura, H. Yanagihara
Published 2005-04-11 by SAE International in United States
The effect of multiple-injection strategy on nozzle hole cavitation has been investigated both experimentally and numerically. A common-rail Diesel injection system, used by Toyota in passenger car engines, has been employed together with a double-shutter CCD camera in order to visualise cavitation inside a submerged and optically accessible (in one out of the six holes) real-size VCO nozzle. Initially the cavitation development was investigated in single injection events followed by flow images obtained during multiple injections consisting of a pilot and a main injection pulse. In order to identify the effect of pilot injection on cavitation development during the main injection, the dwell time between the injection events was varied between 1.5-5ms for different pilot injection quantities. The extensive test matrix included injection pressures of 400 and 800bar and back pressures ranging from 2.4 up to 41bar. The results have confirmed that cavitation patterns in the pilot are very similar to those of the main injection, while the effect of the dwell time was present through the variation of the actual injection pressure caused by…
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Cavitation Modelling in Single-Hole Diesel Injector Based on Eulerian-Lagrangian Approach

City Univ.-M. Gavaises, C. Arcoumanis
Imperial College London-E. Giannadakis, H. Roth
  • Technical Paper
  • 2004-30-0004
Published 2004-09-07 by CMT in Spain
A cavitation model for automotive fuel injection systems has been developed based on the Eulerian-Lagrangian approach. The model incorporates many of the fundamental physical processes assumed to take place in cavitating flows such as bubble formation through nucleation, momentum exchange between the bubbly and the carrier liquid phases, bubble growth and collapse due to non-linear dynamics, bubble turbulent dispersion and both bubble turbulent/hydrodynamic break-up. The effect of bubble-to-bubble interaction on momentum exchange and during bubble growth/collapse is also considered. In addition, the model incorporates a novel approach accounting for bubble motion in Eulerian grids with cell size comparable to that of the bubbles. This effect is accounted for through an improved conservative method that calculates the volume fraction of bubbles which extend to more than one cell, and an improved impingement methodology that considers the actual point of contact of the bubble surface with the solid boundary. The developed model has been used to simulate the cavitating flow of a planar real-size single- hole nozzle; simulations include both fully transient and 'pseudo' steady state operation.…

Nozzle flow and spray characteristics from VCO diesel injector nozzles

City Univ.-M. Gavaises, C. Arcoumanis, H. Roth
Imperial College of Science, Technology and Medicine-Y. S. Choi
  • Technical Paper
  • 2002-30-0002
Published 2002-09-10 by CMT in Spain
Imaging of the transient flow inside one of the six holes of a real-size, VCO-type injector incorporating a quartz window has allowed visualization of the cavitating flow in the nozzle sac and holes under realistic injection conditions. Interpretation of these two-phase nozzle flow patterns has been assisted by images obtained with both a CCD and a high-speed camera in an identical enlarged transparent injector as well as through CFD and 1-D fuel injection system calculations incorporating a bubble dynamics cavitation model and a phenomenological cavitation- induced atomization model. Identification of the link between the internal nozzle flow and the spray characteristics has been achieved by phase doppler measurements of the droplet size and velocities inside a constant-volume chamber for a variety of gas pressure/temperature and injection pressure conditions.

Strategies for Gasoline Particulate Emission Control - A “Foresight Vehicle” Project

Dept of Mechanical Engineering, Imperial College of Science, Technology & Medicine-R. I. Crane, L. Rubino
Johnson Matthey Technology Centre-S. E. Golunski, J. M. McNamara, S. Poulston, R. R. Rajaram
Published 2002-06-03 by SAE International in United States
The health threat from sub-100 nm particulates, emitted in significant numbers from gasoline vehicles, and anticipated changes in legislation to address this, have prompted investigation of techniques capable of trapping and oxidizing particulates from gasoline engines. Numerical studies have indicated that cooling to encourage particle capture by thermophoresis is less effective than use of electrostatic fields. A laboratory wire-cylinder electrostatic trap is under development, showing promising initial results. As an alternative trapping technique, the effectiveness of a cordierite wall-flow filter has been demonstrated, in simulation experiments and on a GDI-engined vehicle. Catalysts have been identified for particulate oxidation at typical exhaust temperatures, using water vapour and carbon dioxide as the oxygen source and retaining activity after short-term high-temperature aging.
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