Spark Plasma in Different Gas Media Under Flow Conditions

2020 ◽  
Vol 48 (1) ◽  
pp. 104-108
Author(s):  
Zhenyi Yang ◽  
Hua Zhu ◽  
Xiao Yu ◽  
Ming Zheng ◽  
David S-K Ting
Keyword(s):  
Flow Conditions ◽  
Spark Plasma

Discharge Characteristics of Current Boosted Spark Events Under Flow Conditions

2017 ◽  
Author(s):  
Xiao Yu ◽  
Zhenyi Yang ◽  
Shui Yu ◽  
Mark Ives ◽  
Ming Zheng
Keyword(s):  
Flow Velocity ◽  
Discharge Current ◽  
Gas Flow ◽  
Spark Ignition ◽  
Current Level ◽  
Flow Conditions ◽  
Kernel Development ◽  
Flame Kernel ◽  
Spark Plasma ◽  
Gas Flow Velocity

With the advancement of spark ignition engines, lean or diluted in-cylinder charge is often used to improve the engine performance. Enhanced in-cylinder charge motion is widely applied under such conditions to promote the flame propagation, which raise challenges for the spark ignition system. In this work, the spark discharging process is investigated under different flow conditions via both optical diagnosis and electrical measurement. Results show that the spark plasma channel is stretched under flow conditions. A higher discharge current can maintain the stretched spark plasma for a longer duration. Re-strikes are observed when the spark plasma is stretched to a certain extent. The frequency of re-strikes increases with increased flow velocity and decreased discharge current level. The discharge duration reduces with the increased flow velocity. The effects of gas flow on the ignition and flame kernel development are studied in a constant volume optical combustion chamber with premixed lean and stoichiometric methane air mixture. Two spark strategies with low and high discharge current are used for the ignition. The flame propagation speed of both lean and stoichiometric mixtures increases with the increased gas flow velocity. A higher discharge current level retains a more stable spark channel and improves the flame kernel development for both lean and stoichiometric conditions, especially under the higher gas flow velocity of 20 m/s.

Investigation of multi-event spark discharge strategy for lean methane-air combustion

2021 ◽  
pp. 095440702098459
Author(s):  
Hua Zhu ◽  
Xiao Yu ◽  
Li Liang ◽  
Ming Zheng ◽  
Graham Reader
Keyword(s):  
Flow Conditions ◽  
Operational Parameters ◽  
High Background ◽  
Flame Kernel ◽  
Single Coil ◽  
Constant Volume Combustion Chamber ◽  
Spark Plasma ◽  
Working Frequency ◽  
Combustion Tests

The characterization of the single-coil repetitive discharge and the dual-coil offset discharge was conducted in a constant volume combustion chamber to better understand the operating principle of the multi-event spark ignition strategies. A parametric study of the dual-coil offset discharge was carried out through electric and optical diagnosis to identify the effective operational parameters, including coil working frequency, charging voltage, and coil inductances. Combustion tests under both quiescent and flow conditions with methane-air mixture were performed to demonstrate the ignition capability of the dual-coil offset strategy. Test results have shown that constantly depositing spark energy through offset discharge is beneficial to secure flame kernel. However, the offset discharge strategy requires a high working frequency, an elevated charging voltage, and fast reacting coils to maintain the spark plasma channel under high background pressure and intensified flow conditions.

Electrical and Optical Characterization Methodologies for Advanced Spark Ignition

2022 ◽  
pp. 1-35
Author(s):  
Linyan Wang ◽  
Guangyun Chen ◽  
Jimi Tjong ◽  
Ming Zheng
Keyword(s):  
Spark Ignition ◽  
Combustion Engines ◽  
Flow Conditions ◽  
Current Management ◽  
Task Control ◽  
Density Flow ◽  
Efficient Combustion ◽  
Spark Plasma ◽  
Aviation Engines ◽  
A Current

Abstract Due to the high transiency and high voltage characteristics of spark ignition, precise measurements are in demand for efficient ignition in future clean combustion engines. The practical challenges of SI systems arise as the gaseous substances vary extensively in density, flow, and temperature. In this paper, a typical transistor coil ignition system with a current management module maintains the transient discharge condition for more credible measurements. Suitable apparatus with FPGA multi-task control systems are established to effectively control and stabilize the discharge current level and duration. The electrical waveforms and spark plasma patterns are correlated, via concurrent electric probing and shadowgraph imaging, under quiescent and flow conditions. The multi-task FPGA provides synchronization of ignition control and data acquisition. The empirical setup and analyzing methods of this work provide essential guidance for facilitating broader innovations in spark ignition, and for advancing the clean and efficient combustion in automotive and aviation engines.

Thrombus formation on artificial surfaces: Correlative microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 840-841
Author(s):  
Quintin J. Lai ◽  
Stuart L. Cooper ◽  
Ralph M. Albrecht
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Low Voltage ◽  
Thrombus Formation ◽  
Blood Platelets ◽  
Polymer Surfaces ◽  
Flow Conditions ◽  
Transmission Electron ◽  
Adhesion Of Platelets ◽  
Microscopic Techniques

Thrombus formation and embolization are significant problems for blood-contacting biomedical devices. Two major components of thrombi are blood platelets and the plasma protein, fibrinogen. Previous studies have examined interactions of platelets with polymer surfaces, fibrinogen with platelets, and platelets in suspension with spreading platelets attached to surfaces. Correlative microscopic techniques permit light microscopic observations of labeled living platelets, under static or flow conditions, followed by the observation of identical platelets by electron microscopy. Videoenhanced, differential interference contrast (DIC) light microscopy permits high-resolution, real-time imaging of live platelets and their interactions with surfaces. Interference reflection microscopy (IRM) provides information on the focal adhesion of platelets on surfaces. High voltage, transmission electron microscopy (HVEM) allows observation of platelet cytoskeletal structure of whole mount preparations. Low-voltage, high resolution, scanning electron microscopy allows observation of fine surface detail of platelets. Colloidal gold-labeled fibrinogen, used to identify the Gp Ilb/IIIa membrane receptor for fibrinogen, can be detected in all the above microscopies.

Hydrodynamic flow conditions through permeable walls

1992 ◽  
Vol 2 (8) ◽  
pp. 1565-1569
Author(s):  
S. Vollmar ◽  
J. A. M. S. Duarte
Keyword(s):  
Hydrodynamic Flow ◽  
Flow Conditions ◽  
Permeable Walls

Platelet and Shear Rate Promote Tumor Cell Adhesion to Human Endothelial Extracellular Matrix - Absence of a Role for Platelet Cyclooxygenase

1989 ◽  
Vol 61 (03) ◽  
pp. 485-489 ◽  
Author(s):  
Eva Bastida ◽  
Lourdes Almirall ◽  
Antonio Ordinas
Keyword(s):  
Cell Adhesion ◽  
Shear Rate ◽  
Tumor Cell ◽  
Umbilical Vein ◽  
Blood Platelets ◽  
Flow Conditions ◽  
Tumor Cell Adhesion ◽  
Rate Dependent ◽  
Static Conditions

SummaryBlood platelets are thought to be involved in certain aspects of malignant dissemination. To study the role of platelets in tumor cell adherence to vascular endothelium we performed studies under static and flow conditions, measuring tumor cell adhesion in the absence or presence of platelets. We used highly metastatic human adenocarcinoma cells of the lung, cultured human umbilical vein endothelial cells (ECs) and extracellular matrices (ECM) prepared from confluent EC monolayers. Our results indicated that under static conditions platelets do not significantly increase tumor cell adhesion to either intact ECs or to exposed ECM. Conversely, the studies performed under flow conditions using the flat chamber perfusion system indicated that the presence of 2 × 105 pl/μl in the perfusate significantly increased the number of tumor cells adhered to ECM, and that this effect was shear rate dependent. The maximal values of tumor cell adhesion were obtained, in presence of platelets, at a shear rate of 1,300 sec-1. Furthermore, our results with ASA-treated platelets suggest that the role of platelets in enhancing tumor cell adhesion to ECM is independent of the activation of the platelet cyclooxygenase pathway.

Fabrication and Mechanical Properties of ultra fine WC-6wt.%Co by Spark Plasma Sintering Process

2011 ◽  
Vol 49 (01) ◽  
pp. 40-45 ◽  
Author(s):  
Hyun-Kuk Park ◽  
Seung-Min Lee ◽  
Hee-Jun Youn ◽  
Ki-Sang Bang ◽  
Ik-Hyun Oh
Keyword(s):  
Mechanical Properties ◽  
Spark Plasma Sintering ◽  
Sintering Process ◽  
Plasma Sintering ◽  
Spark Plasma
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