Simulation of cavitation in outward-opening piezo-type pintle injector nozzles

2008 ◽  
Vol 222 (10) ◽  
pp. 1895-1910 ◽  
Author(s):  
E Giannadakis ◽  
D Papoulias ◽  
A Theodorakakos ◽  
M Gavaises
Keyword(s):  
Bubble Growth ◽  
Large Scale ◽  
Direct Injection ◽  
Bubble Formation ◽  
Needle Valve ◽  
Transient Effects ◽  
Cavitation Model ◽  
Gasoline Engines ◽  
Opening And Closing ◽  
Vapour Film

The onset and development of cavitation in the annular needle seat passage of piezo-driven outward-opening pintle injector nozzles used with spray-guided direct-injection gasoline engines are studied using a Eulerian-Lagrangian computational fluid dynamics cavitation model. Cavitation is formed because of the fluid acceleration taking place at the needle sealing area and it has been found to be affected by its geometric details. Various submodels for nucleation and bubble formation, further bubble growth and collapse, as well as bubble break-up and transport are incorporated into the model. Qualitative model validation is performed against experimental data reported elsewhere in large-scale nozzle replicas, showing similar cavitation patterns to be formed. These consist of vapour pockets rather than a continuous vapour film and develop transiently in a rather chaotic manner around the circumferential needle sealing area, even under stationary geometry and fixed-flowrate conditions. Further transient effects associated with the fast opening and closing of the piezo-controlled needle valve are also presented.

Quick Response Fuel Injector for Direct-Injection Gasoline Engines

2011 ◽  
Author(s):  
Motoyuki Abe ◽  
Noriyuki Maekawa ◽  
Yoshihito Yasukawa ◽  
Tohru Ishikawa ◽  
Yasuo Namaizawa ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Delay Time ◽  
Direct Injection ◽  
Dominant Factor ◽  
Needle Valve ◽  
Quick Response ◽  
Fuel Injector ◽  
Gasoline Engines ◽  
Injection Quantity ◽  
Closing Mechanism

We developed a new injector for direct injection gasoline engines that reduce the exhaust emissions and help to reduce fuel consumption. The newly developed actuator in this injector has two features. One is a bounce-less valve closing mechanism, and the second is quick-response moving parts. The first feature, the bounce-less valve closing mechanism, can prevent ejecting a coarse droplet, which causes unburned gas emission. The new actuation mechanism realizes the bounce-less valve closing. We analyzed the valve motion and injection behavior. The second feature, the quick response actuator, achieves a smaller minimum injection quantity. This feature assists in reducing the fuel consumption under low load engine conditions. The closing delay time of the needle valve is the dominant factor of the minimum injection quantity because the injection quantity is controlled by the duration time of the valve opening. The new actuator movements can be operated with a shorter closing delay time. The closing delay time is caused by a magnetic delay and kinematic delay. A compact magnetic circuit of the actuator reduces the closing delay time by 26%. In addition, the kinematic delay was improved when the hydraulic resistance was reduced by 9%. As a result, the new injector realizes reduction of the minimum injection quantity by 25% compared to a conventional injector.

Quick Response Fuel Injector for Direct-Injection Gasoline Engines

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Motoyuki Abe ◽  
Noriyuki Maekawa ◽  
Yoshihito Yasukawa ◽  
Tohru Ishikawa ◽  
Yasuo Namaizawa ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Delay Time ◽  
Direct Injection ◽  
Dominant Factor ◽  
Needle Valve ◽  
Quick Response ◽  
Fuel Injector ◽  
Gasoline Engines ◽  
Injection Quantity ◽  
Closing Mechanism

We developed a new injector for direct injection gasoline engines that reduce the exhaust emissions and help to reduce fuel consumption. The newly developed actuator in this injector has two features. One is a bounceless valve closing mechanism, and the second is quick response moving parts. The first feature, the bounceless valve closing mechanism, can prevent ejecting a coarse droplet, which causes unburned gas emission. The new actuation mechanism realizes the bounceless valve closing. We analyzed the valve motion and injection behavior. The second feature, the quick-response actuator, achieves a smaller minimum injection quantity. This feature assists in reducing the fuel consumption under low load engine conditions. The closing delay time of the needle valve is the dominant factor of the minimum injection quantity because the injection quantity is controlled by the duration time of the valve opening. The new actuator movements can be operated with a shorter closing delay time. The closing delay time is caused by a magnetic delay and kinematic delay. A compact magnetic circuit of the actuator reduces the closing delay time by 26%. In addition, the kinematic delay was improved when the hydraulic resistance was reduced by 9%. As a result, the new injector realizes reduction of the minimum injection quantity by 25% compared to a conventional injector.

scholarly journals An ultra-low-cost electroporator with microneedle electrodes (ePatch) for SARS-CoV-2 vaccination

2021 ◽  
Vol 118 (45) ◽  
pp. e2110817118
Author(s):  
Dengning Xia ◽  
Rui Jin ◽  
Gaurav Byagathvalli ◽  
Huan Yu ◽  
Ling Ye ◽  
...  
Keyword(s):  
Immune Responses ◽  
Large Scale ◽  
Low Cost ◽  
Electrode Array ◽  
Dna Vaccination ◽  
Intradermal Injection ◽  
Antibody Responses ◽  
Transient Effects ◽  
Electric Pulses ◽  
High Electric Field Strength

Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other pathogens with pandemic potential requires safe, protective, inexpensive, and easily accessible vaccines that can be developed and manufactured rapidly at a large scale. DNA vaccines can achieve these criteria, but induction of strong immune responses has often required bulky, expensive electroporation devices. Here, we report an ultra-low-cost (<1 USD), handheld (<50 g) electroporation system utilizing a microneedle electrode array (“ePatch”) for DNA vaccination against SARS-CoV-2. The low cost and small size are achieved by combining a thumb-operated piezoelectric pulser derived from a common household stove lighter that emits microsecond, bipolar, oscillatory electric pulses and a microneedle electrode array that targets delivery of high electric field strength pulses to the skin’s epidermis. Antibody responses against SARS-CoV-2 induced by this electroporation system in mice were strong and enabled at least 10-fold dose sparing compared to conventional intramuscular or intradermal injection of the DNA vaccine. Vaccination was well tolerated with mild, transient effects on the skin. This ePatch system is easily portable, without any battery or other power source supply, offering an attractive, inexpensive approach for rapid and accessible DNA vaccination to combat COVID-19, as well as other epidemics.

Cavitation in Fuel Injection Systems for Spray-Guided Direct Injection Gasoline Engines

2007 ◽  
Author(s):  
D. Papoulias ◽  
E. Giannadakis ◽  
N. Mitroglou ◽  
M. Gavaises ◽  
A. Theodorakakos
Keyword(s):  
Fuel Injection ◽  
Direct Injection ◽  
Gasoline Engines

Simulation of Coarse Droplet and Liquid Column Formed around Nozzle Outlets Due to Valve Wobble of a Gasoline Direct Injection Injector

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Eiji Ishii ◽  
Yoshihito Yasukawa ◽  
Kazuki Yoshimura ◽  
Kiyotaka Ogura
Keyword(s):  
Surface Tension ◽  
Particulate Matter ◽  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Fuel Spray ◽  
Direct Injection Engines ◽  
Fuel Injectors ◽  
Multiple Injections ◽  
Fuel Mixtures ◽  
Opening And Closing

The generation of particulate matter (PM) is one problem with gasoline direct-injection engines. PM is generated in high-density regions of fuel. Uniform air/fuel mixtures and short fuel-spray durations with multiple injections are effective in enabling the valves of fuel injectors not to wobble and dribble. We previously studied what effects the opening and closing of valves had on fuel spray behavior and found that valve motions in the opening and closing directions affected spray behavior and generated coarse droplets during the end-of-injection. We focused on the effects of valve wobbling on fuel spray behavior in this study, especially on the behavior during the end-of-injection. The effects of wobbling on fuel spray with full valve strokes were first studied, and we found that simulated spray behaviors agreed well with the measured ones. We also studied the effects on fuel dribble during end-of-injection. When a valve wobbled from left to right, the fuel dribble decreased in comparison with a case without wobbling. When a valve wobbled from the front to the rear, however, fuel dribble increased. Surface tension significantly affected fuel dribble, especially in forming low-speed liquid columns and coarse droplets. Fuel dribble was simulated while changing the wetting angle on walls from 60 to 5 deg. We found that the appearance of coarse droplets in sprays decreased during the end-of-injection by changing the wetting angles from 60 to 5 deg.

Spray Atomization Study on Multi-Hole Nozzle for Direct Injection Gasoline Engines

2013 ◽  
Author(s):  
Motoyuki Abe ◽  
Ehara Hideharu ◽  
Soma Masahiro ◽  
Tohru Ishikawa
Keyword(s):  
Direct Injection ◽  
Spray Atomization ◽  
Gasoline Engines

Numerical Simulation of Bubble Formation in Co-Flowing Mercury

2008 ◽  
Author(s):  
Ashraf Ibrahim ◽  
Mark Wendel ◽  
David Felde ◽  
Bernard Riemer
Keyword(s):  
Acoustic Waves ◽  
Bubble Growth ◽  
Gas Flow ◽  
Bubble Formation ◽  
Science Center ◽  
Proton Radiography ◽  
Two Phase ◽  
Vof Model ◽  
Computational Fluid Dynamics Cfd ◽  
Bubble Sizes

In this work, we present computational fluid dynamics (CFD) simulations of helium bubble formation and detachment at a submerged needle in stagnant and co-flowing mercury. Since mercury is opaque, visualization of internal gas bubbles was done with proton radiography (pRad) at the Los Alamos Neutron Science Center (LANSCE2). The acoustic waves emitted at the time of detachment and during subsequent oscillations of the bubble were recorded with a microphone. The Volume of Fluid (VOF) model was used to simulate the unsteady two-phase flow of gas injection in mercury. The VOF model is validated by comparing detailed bubble sizes and shapes at various stages of the bubble growth and detachment, with the experimental measurements at 1.66 mg/min helium gas flow rate and different mercury velocities. The experimental and computational results show a two-stage bubble formation in stagnant mercury. The first stage involves growing bubble around the needle, and the second follows as the buoyancy overcomes wall adhesion. The comparison of predicted and measured bubble sizes and shapes at various stages of the bubble growth and detachment is in good agreement.

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