压电式喷油器学术搜索.doc

一Internal Flow and Spray Characteristics of Pintle-Type Outwards Opening Piezo Injectors for Gasoline Direct-Injection EnginesDate Published: 2007-04-16Paper Number: 2007-01-1406 DOI: 10.4271/2007-01-1406 Citation:Marchi, A., Nouri, J., Yan, Y., and Arcoumanis, C., Internal Flow and Spray Characteristics of Pintle-Type Outwards Opening Piezo Injectors for Gasoline Direct-Injection Engines, SAE Technical Paper 2007-01-1406, 2007, doi:10.4271/2007-01-1406.Author(s):A. Marchi - City University, London J. M. Nouri - City University, London Y. Yan - City University, London C. Arcoumanis - City University, London View All CollapseAbstract: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 results showed that the number of strings increased linearly, within the measured range, with liquid exit velocity and that the spray cone angle was smaller or larger than the nominal value depending on the attachment of air pockets to the cartridge or needle surfaces, respectively; these two distinct small and large cone angles were found to be dominant at low and high lifts. Increasing the flow rate further so that CN exceeds the critical value, gave rise to pockets of vapour that started to emerge in the nozzle seat region and disintegrated rapidly as they were convected towards the nozzle exit. The analysis of the near nozzle flow visualizations has shown the existence of air entrainment and cavitation as two different phenomena occurring under different operating conditions.File Size: 4445KProduct Status: In Stock Included in: SP-2084 See papers presented at SAE World Congress & Exhibition, April 2007, Detroit, MI, USA, Session: Direct Injection SI Engine Technology (Part 2 of 3)Purchase more technical papers and save! With TechSelect, you decide what SAE Technical Papers you need, when you need them, and how much you want to pay. Learn more 二Effect of Injector Type on Fuel-Air Mixture Formation of High-Speed Diesel Sprays1. Sung Wook Park12. Jae Wouk Kim23. Chang Sik Lee31. 1Graduate School of Hangyang University, Seoul, Republic of Korea 2. 2Department of Automobile Engineering, Doowon Technical College, Anseong, Republic of Korea 3. 3Department of Mechanical Engineering, Hanyang University, Seoul, Republic of Korea AbstractThis study was performed to analyse the characteristics of fuel sprays issued from a piezo-driven injector and to compare both experimental results and numerical predictions with those from a solenoid-driven injector. In order to study the effect of the injector type, two injectors with the same specifications - except for their drive type - were used in the experiments. In this work, the profiles of injection rates, processes of spray development, mean droplet size distributions, and mean velocities were obtained using an injection rate meter, a spray visualization system, and a phase Doppler particle analyser (PDPA) system. In order to calculate the atomization process of the injected spray, the Kelvin-Helmholtz instability/droplet deformation and break-up (KH-DDB) model was used, and the prediction accuracies were verified by comparing them with experimental results. For the numerical approach using the KIVA code, the nozzle flow and droplet break-up models were modified to consider the conditions of a common-rail injection system. The input parameters for the KIVA calculations were determined based on the nozzle flow model considering the effect of cavitation. In addition, the effects of injector type on the evaporation characteristics were calculated using the modified Spalding evaporation model. This study reveals that the injection delay of the piezo-driven injector is shorter than that of the solenoid-driven injector by 0.06 ms, and that the atomization and evaporation performances of the fuel spray can be enhanced by using the piezo injector instead of the solenoid injector. 三Effect of piezo-driven and solenoid-driven needle opening of common-rail diesel injectors on internal nozzle flow and spray developmentA prototype piezo-driven diesel injector has been developed and characterized in terms of measured flowrate, predicted cavitating nozzle hole flow distribution, and visual spray development. Results are compared with those obtained for a conventional solenoid-driven diesel injector equipped with the same micro-sac multi-hole injection nozzle. The response time and the needle lift trace for both injectors have been predicted for injection pressures up to 1300 bar using a hydraulic simulation model. Mie spray images obtained using a high-speed camera and utilizing diffusion illumination light, have allowed estimation of the spray tip penetration and spray cone angle under a variety of back pressures. The experimental results show that the piezo-driven injector produces longer spray ti