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.

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.

Laser ignition and flame kernel characterization of HCNG in a constant volume combustion chamber

Fuel ◽  
2017 ◽  
Vol 190 ◽  
pp. 318-327 ◽  
Author(s):  
Rajesh Kumar Prasad ◽  
Siddhant Jain ◽  
Gaurav Verma ◽  
Avinash Kumar Agarwal
Keyword(s):  
Combustion Chamber ◽  
Constant Volume ◽  
Laser Ignition ◽  
Flame Kernel ◽  
Constant Volume Combustion ◽  
Constant Volume Combustion Chamber ◽  
Kernel Characterization

scholarly journals Fabrication and Characterization of Quinary High Entropy-Ultra-High Temperature Diborides

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 108-120
Author(s):  
Simone Barbarossa ◽  
Roberto Orrù ◽  
Valeria Cannillo ◽  
Antonio Iacomini ◽  
Sebastiano Garroni ◽  
...  
Keyword(s):  
High Temperature ◽  
Single Phase ◽  
Nominal Composition ◽  
High Entropy ◽  
Chemical Complexity ◽  
Alternative Processing ◽  
Plasma Sintering ◽  
High Temperature Synthesis ◽  
Spark Plasma

Due to their inherent chemical complexity and their refractory nature, the obtainment of highly dense and single-phase high entropy (HE) diborides represents a very hard target to achieve. In this framework, homogeneous (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2, (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2, and (Hf0.2Zr0.2Nb0.2Mo0.2Ti0.2)B2 ceramics with high relative densities (97.4, 96.5, and 98.2%, respectively) were successfully produced by spark plasma sintering (SPS) using powders prepared by self-propagating high-temperature synthesis (SHS). Although the latter technique did not lead to the complete conversion of initial precursors into the prescribed HE phases, such a goal was fully reached after SPS (1950 °C/20 min/20 MPa). The three HE products showed similar and, in some cases, even better mechanical properties compared to ceramics with the same nominal composition attained using alternative processing methods. Superior Vickers hardness and elastic modulus values were found for the (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2 and the (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2 systems, i.e., 28.1 GPa/538.5 GPa and 28.08 GPa/498.1 GPa, respectively, in spite of the correspondingly higher residual porosities (1.2 and 2.2 vol.%, respectively). In contrast, the third ceramic, not containing tantalum, displayed lower values of these two properties (25.1 GPa/404.5 GPa). However, the corresponding fracture toughness (8.84 MPa m1/2) was relatively higher. This fact can be likely ascribed to the smaller residual porosity (0.3 vol.%) of the sintered material.

scholarly journals Development of a User-Friendly Pipeline for Mutational Analyses of HIV Using Ultra-Accurate Maximum-Depth Sequencing

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1338
Author(s):  
Morgan E. Meissner ◽  
Emily J. Julik ◽  
Jonathan P. Badalamenti ◽  
William G. Arndt ◽  
Lauren J. Mills ◽  
...  
Keyword(s):  
Error Rates ◽  
Maximum Depth ◽  
Sequencing Data ◽  
Background Error ◽  
High Background ◽  
Immunodeficiency Virus ◽  
User Friendly ◽  
Viral Mutagenesis ◽  
Hiv 1

Human immunodeficiency virus type 2 (HIV-2) accumulates fewer mutations during replication than HIV type 1 (HIV-1). Advanced studies of HIV-2 mutagenesis, however, have historically been confounded by high background error rates in traditional next-generation sequencing techniques. In this study, we describe the adaptation of the previously described maximum-depth sequencing (MDS) technique to studies of both HIV-1 and HIV-2 for the ultra-accurate characterization of viral mutagenesis. We also present the development of a user-friendly Galaxy workflow for the bioinformatic analyses of sequencing data generated using the MDS technique, designed to improve replicability and accessibility to molecular virologists. This adapted MDS technique and analysis pipeline were validated by comparisons with previously published analyses of the frequency and spectra of mutations in HIV-1 and HIV-2 and is readily expandable to studies of viral mutation across the genomes of both viruses. Using this novel sequencing pipeline, we observed that the background error rate was reduced 100-fold over standard Illumina error rates, and 10-fold over traditional unique molecular identifier (UMI)-based sequencing. This technical advancement will allow for the exploration of novel and previously unrecognized sources of viral mutagenesis in both HIV-1 and HIV-2, which will expand our understanding of retroviral diversity and evolution.

Characterization of reactive spark plasma sintered (Zr,Ti)B2–ZrC–SiC composites

2021 ◽  
Vol 119 ◽  
pp. 187-195 ◽  
Author(s):  
Abbas Sabahi Namini ◽  
Seyed Ali Delbari ◽  
Mehdi Shahedi Asl ◽  
Quyet Van Le ◽  
Mohammadreza Shokouhimehr
Keyword(s):  
Spark Plasma ◽  
Sic Composites

Characterization of mullite-Nd2O3 composite prepared through spark plasma sintering

2021 ◽  
Vol 47 (11) ◽  
pp. 16200-16207
Author(s):  
Ehsan Ghasali ◽  
Yasin Orooji ◽  
Aida Faeghi-nia ◽  
Masoud Alizadeh ◽  
Touradj Ebadzadeh
Keyword(s):  
Spark Plasma Sintering ◽  
Plasma Sintering ◽  
Spark Plasma

scholarly journals Quantitative Characterization of Geotrichum candidum Growth in Milk

2021 ◽  
Vol 11 (10) ◽  
pp. 4619
Author(s):  
Petra Šipošová ◽  
Martina Koňuchová ◽  
Ľubomír Valík ◽  
Monika Trebichavská ◽  
Alžbeta Medveďová
Keyword(s):  
Growth Parameters ◽  
Mechanistic Model ◽  
Geotrichum Candidum ◽  
Activity Level ◽  
Effect Of Temperature ◽  
Operational Parameters ◽  
Quantitative Characterization ◽  
Essential Knowledge ◽  
Cardinal Temperatures

The study of microbial growth in relation to food environments provides essential knowledge for food quality control. With respect to its significance in the dairy industry, the growth of Geotrichum candidum isolate J in milk without and with 1% NaCl was investigated under isothermal conditions ranging from 6 to 37 °C. The mechanistic model by Baranyi and Roberts was used to fit the fungal counts over time and to estimate the growth parameters of the isolate. The effect of temperature on the growth of G. candidum in milk was modelled with the cardinal models, and the cardinal temperatures were calculated as Tmin = −3.8–0.0 °C, Topt = 28.0–34.6 °C, and Tmax = 35.2–37.2 °C. The growth of G. candidum J was slightly faster in milk with 1% NaCl and in temperature regions under 21 °C. However, in a temperature range that was close to the optimum, its growth was slightly inhibited by the lowered water activity level. The present study provides useful cultivation data for understanding the behaviour of G. candidum in milk and can serve as an effective tool for assessing the risk of fungal spoilage, predicting the shelf life of dairy products, or assessing the optimal conditions for its growth in relation to the operational parameters in dairy practices.

Determination of Bio Content in Polymers used in the Packaging of food Products

Radiocarbon ◽  
2019 ◽  
Vol 61 (6) ◽  
pp. 1973-1981
Author(s):  
C Telloli ◽  
A Rizzo ◽  
C Canducci ◽  
P Bartolomei
Keyword(s):  
Food Packaging ◽  
Liquid Scintillation ◽  
Scintillation Counting ◽  
Operational Parameters ◽  
Original Design ◽  
Plastic Materials ◽  
Different Types ◽  
Scintillation Method

ABSTRACTThe ENEA Radiocarbon Laboratory (Bologna, Italy) has been operating since 1985; it is the oldest among such laboratories operating in Italy and has been active for about 30 years in the field of dating of different types of samples with the radiocarbon (14C) liquid scintillation method. This study shows the detailed procedure for radiocarbon analysis on bioplastic materials by means of the synthesis of benzene, which includes CO2 production and purification, synthesis of acetylene, and synthesis and collection of benzene. The changes made to the original design of the synthesis procedures and the operational parameters adopted to optimize the combustion of the plastic materials are described. The measurement of 14C activity was performed using the liquid scintillation counting technique by a QuantulusTM 1220 low-background counter. The δ13C content was compared with the percentage of 14C concentration for the characterization of the bio content in plastic used in the food packaging.

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