The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Norimasa Iida - One of the best experts on this subject based on the ideXlab platform.
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an investigation of multiple spark Discharge using multi coil ignition system for improving thermal efficiency of lean si engine operation
Applied Energy, 2018Co-Authors: Dongwon Jung, Norimasa IidaAbstract:Abstract Lean spark ignition (SI) engine operation can provide improvement of the thermal efficiency relative to that of stoichiometric SI operation. However, the cycle-to-cycle variations of SI combustion increase with increasing air dilution, and become unacceptable. To gain the benefits of lean operation, the ability to ensure stable, complete and fast combustion is required. As a method to enable stable lean operation, this study investigates the effects of multiple spark Discharge on lean SI operation using a multi-coil ignition system that features ten spark coils for a single spark plug. First, the effects of multiple spark Discharge on the combustion phasing and the combustion duration are examined for lean operation (excess-air ratio (λ) = 1.67) under a constant spark timing. The results show that both the total Discharge duration and the total Discharge Energy increase with the extension of time interval between spark Discharges (Δti) for multiple spark Discharge. For the multiple spark Discharge of substantially extended Δti, a number of restrikes occur after the spark blowouts due to the weak Discharge Energy release rate. However, both the total Discharge duration and the total Discharge Energy do not contribute directly to the change of initial combustion phase. Instead, the effective spark Discharge Energy exists within the total Discharge Energy, which actually contributes to the change of initial combustion phase. When the effective spark Discharge Energy is high, it leads to the advancement of the initial combustion phase, resulting in the number of knocking cycles increases with the increase of knocking intensity. Second, additional experiments were conducted under ultra-lean conditions in the λ = 1.82–1.97 range since the effects of multiple spark Discharge on SI combustion are much more pronounced for the leaner operation. The results show that the net indicated thermal efficiency increases quite linearly with increasing λ for all multiple spark Discharges considered. Especially, for the multiple spark Discharge of Δti = 0.2 ms, a proper spark Discharge Energy is generated from the spark timing to a certain timing after the first start of spark Discharge, which advances both the spark timing and the initial combustion phase. A combination of the advanced spark timing and the advanced initial combustion phase leads to the advancement of main combustion phase, and eventually shorten the combustion duration. Because of shortened combustion duration, stable ultra-lean operation at around λ = 1.94 can be achieved with the highest net indicated thermal efficiency of 47.0%.
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Effects of increased spark Discharge Energy and enhanced in-cylinder turbulence level on lean limits and cycle-to-cycle variations of combustion for SI engine operation
Applied Energy, 2017Co-Authors: Dongwon Jung, Kosaku Sasaki, Norimasa IidaAbstract:Abstract Improving the thermal efficiency of spark ignition (SI) engines is strongly required due to its widespread use but considerably less efficiency than that of compression ignition (CI) engines. Although lean SI engine operation can offer substantial improvements of the thermal efficiency relative to that of traditional stoichiometric SI operation, the cycle-to-cycle variations of combustion increase with the level of air dilution, and become unacceptable. For improving the thermal efficiency by extending the lean-stability limit, this study examines the effects of spark Discharge Energy and in-cylinder turbulence level on lean limits and cycle-to-cycle variations of combustion for SI engine operation. The spark Discharge Energy was increased by a high-Energy inductive ignition system using ten spark coils and the in-cylinder turbulence level was enhanced by a custom adapter installed in the intake port. The results show that increased spark Discharge Energy by ten spark coils is effective at shifting the lean-stability limit to leaner operation, compared to that of a single spark coil. With shift of the lean-stability limit, significant improvement of thermal efficiency is observed, relative to that of stoichiometric operation. Furthermore, a combination of increased spark Discharge Energy and enhanced in-cylinder turbulence level makes it possible to allow stable operation at more extended lean-stability limit. This is mainly attributed to shortening the durations of spark timing-to-CA5 and CA10-to-CA90 by both increased spark Discharge Energy and enhanced in-cylinder turbulence level. However, the cycle-to-cycle variations of SI combustion increase with increasing excess-air ratio even for operation by ten spark coils with the intake port adapter. Finally, the relationship between the spark Discharge Energy and the SI combustion is examined and compared for ultra-lean operation without and with the intake port adapter. Although indicated thermal efficiency is improved by increased spark Discharge Energy, the variations of the spark Discharge Energy do not relate to the variations of the combustion, since total spark Discharge Energy does not affect both durations of the spark timing-to-CA5 and the CA10-to-CA90, and eventually the heat-release efficiency.
Biaolin Peng - One of the best experts on this subject based on the ideXlab platform.
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low temperature poling awakened high dielectric breakdown strength and outstanding improvement of Discharge Energy density of pb la zr sn ti o3 relaxor thin film
Nano Energy, 2020Co-Authors: Biaolin Peng, Silin Tang, Li Lu, Qi Zhang, Haitao Huang, Lei Miao, Zhong Lin WangAbstract:Abstract Ferroelectric thin films possessing high dielectric breakdown strength (DBS) are attractive materials employed to satisfy the requirements of miniaturization and integration of electronic components, especially for dielectric capacitors with large Discharge Energy density (W). In this work, it is demonstrated for the first time that high DBS in ferroelectric thin film can be awakened by a low-temperature-poling method. Mn-doped Pb0.97La0.02(Zr0.905Sn0.015Ti0.08)O3 (PLZST) relaxor thin films were prepared by using a sol-gel method, as when poled at near liquid nitrogen temperature, its DBS and W at room temperature are greatly enhanced (nearly doubled) from 1286 kV/cm to 2000 kV/cm, and from 16.6 J/cm3 to 31.2 J/cm3, respectively. The high ordering of defect dipoles during the low-temperature-poling process is responsible for the great enhancement of the awakened DBS and the outstanding improvement of the W. It concludes that the low-temperature-poling method can provide a new alternative strategy to strength the DBS and thus to improve the electrical performances of ferroelectric materials for the applications required strong electric fields in many fields, especially for dielectric Energy storage, electrocaloric cooling, and Energy harvesting, etc.
Dongwon Jung - One of the best experts on this subject based on the ideXlab platform.
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an investigation of multiple spark Discharge using multi coil ignition system for improving thermal efficiency of lean si engine operation
Applied Energy, 2018Co-Authors: Dongwon Jung, Norimasa IidaAbstract:Abstract Lean spark ignition (SI) engine operation can provide improvement of the thermal efficiency relative to that of stoichiometric SI operation. However, the cycle-to-cycle variations of SI combustion increase with increasing air dilution, and become unacceptable. To gain the benefits of lean operation, the ability to ensure stable, complete and fast combustion is required. As a method to enable stable lean operation, this study investigates the effects of multiple spark Discharge on lean SI operation using a multi-coil ignition system that features ten spark coils for a single spark plug. First, the effects of multiple spark Discharge on the combustion phasing and the combustion duration are examined for lean operation (excess-air ratio (λ) = 1.67) under a constant spark timing. The results show that both the total Discharge duration and the total Discharge Energy increase with the extension of time interval between spark Discharges (Δti) for multiple spark Discharge. For the multiple spark Discharge of substantially extended Δti, a number of restrikes occur after the spark blowouts due to the weak Discharge Energy release rate. However, both the total Discharge duration and the total Discharge Energy do not contribute directly to the change of initial combustion phase. Instead, the effective spark Discharge Energy exists within the total Discharge Energy, which actually contributes to the change of initial combustion phase. When the effective spark Discharge Energy is high, it leads to the advancement of the initial combustion phase, resulting in the number of knocking cycles increases with the increase of knocking intensity. Second, additional experiments were conducted under ultra-lean conditions in the λ = 1.82–1.97 range since the effects of multiple spark Discharge on SI combustion are much more pronounced for the leaner operation. The results show that the net indicated thermal efficiency increases quite linearly with increasing λ for all multiple spark Discharges considered. Especially, for the multiple spark Discharge of Δti = 0.2 ms, a proper spark Discharge Energy is generated from the spark timing to a certain timing after the first start of spark Discharge, which advances both the spark timing and the initial combustion phase. A combination of the advanced spark timing and the advanced initial combustion phase leads to the advancement of main combustion phase, and eventually shorten the combustion duration. Because of shortened combustion duration, stable ultra-lean operation at around λ = 1.94 can be achieved with the highest net indicated thermal efficiency of 47.0%.
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Effects of increased spark Discharge Energy and enhanced in-cylinder turbulence level on lean limits and cycle-to-cycle variations of combustion for SI engine operation
Applied Energy, 2017Co-Authors: Dongwon Jung, Kosaku Sasaki, Norimasa IidaAbstract:Abstract Improving the thermal efficiency of spark ignition (SI) engines is strongly required due to its widespread use but considerably less efficiency than that of compression ignition (CI) engines. Although lean SI engine operation can offer substantial improvements of the thermal efficiency relative to that of traditional stoichiometric SI operation, the cycle-to-cycle variations of combustion increase with the level of air dilution, and become unacceptable. For improving the thermal efficiency by extending the lean-stability limit, this study examines the effects of spark Discharge Energy and in-cylinder turbulence level on lean limits and cycle-to-cycle variations of combustion for SI engine operation. The spark Discharge Energy was increased by a high-Energy inductive ignition system using ten spark coils and the in-cylinder turbulence level was enhanced by a custom adapter installed in the intake port. The results show that increased spark Discharge Energy by ten spark coils is effective at shifting the lean-stability limit to leaner operation, compared to that of a single spark coil. With shift of the lean-stability limit, significant improvement of thermal efficiency is observed, relative to that of stoichiometric operation. Furthermore, a combination of increased spark Discharge Energy and enhanced in-cylinder turbulence level makes it possible to allow stable operation at more extended lean-stability limit. This is mainly attributed to shortening the durations of spark timing-to-CA5 and CA10-to-CA90 by both increased spark Discharge Energy and enhanced in-cylinder turbulence level. However, the cycle-to-cycle variations of SI combustion increase with increasing excess-air ratio even for operation by ten spark coils with the intake port adapter. Finally, the relationship between the spark Discharge Energy and the SI combustion is examined and compared for ultra-lean operation without and with the intake port adapter. Although indicated thermal efficiency is improved by increased spark Discharge Energy, the variations of the spark Discharge Energy do not relate to the variations of the combustion, since total spark Discharge Energy does not affect both durations of the spark timing-to-CA5 and the CA10-to-CA90, and eventually the heat-release efficiency.
Zhong Lin Wang - One of the best experts on this subject based on the ideXlab platform.
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low temperature poling awakened high dielectric breakdown strength and outstanding improvement of Discharge Energy density of pb la zr sn ti o3 relaxor thin film
Nano Energy, 2020Co-Authors: Biaolin Peng, Silin Tang, Li Lu, Qi Zhang, Haitao Huang, Lei Miao, Zhong Lin WangAbstract:Abstract Ferroelectric thin films possessing high dielectric breakdown strength (DBS) are attractive materials employed to satisfy the requirements of miniaturization and integration of electronic components, especially for dielectric capacitors with large Discharge Energy density (W). In this work, it is demonstrated for the first time that high DBS in ferroelectric thin film can be awakened by a low-temperature-poling method. Mn-doped Pb0.97La0.02(Zr0.905Sn0.015Ti0.08)O3 (PLZST) relaxor thin films were prepared by using a sol-gel method, as when poled at near liquid nitrogen temperature, its DBS and W at room temperature are greatly enhanced (nearly doubled) from 1286 kV/cm to 2000 kV/cm, and from 16.6 J/cm3 to 31.2 J/cm3, respectively. The high ordering of defect dipoles during the low-temperature-poling process is responsible for the great enhancement of the awakened DBS and the outstanding improvement of the W. It concludes that the low-temperature-poling method can provide a new alternative strategy to strength the DBS and thus to improve the electrical performances of ferroelectric materials for the applications required strong electric fields in many fields, especially for dielectric Energy storage, electrocaloric cooling, and Energy harvesting, etc.
Pao-lin Su - One of the best experts on this subject based on the ideXlab platform.
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Effects of electrical Discharge Energy on machining performance and bending strength of cemented tungsten carbides
Journal of Materials Processing Technology, 2008Co-Authors: Lih-ren Hwang, Chao-hsu Cheng, Pao-lin SuAbstract:This work elucidates the effect of electrical Discharge Energy on surface crack and bending strength of cemented tungsten carbide by electrical Discharge machining (EDM). Cemented tungsten carbides graded K10 and P10 were used as workpiece materials, and the machining parameters of EDM were varied to study the effects of electrical Discharge Energy on material removal rate (MRR) and surface roughness. Moreover, the micro-cracks on the machined surface induced by EDM and the effects of electrical Discharge Energy on the bending strength were also examined. The experimental results reveal that the MRR increased with the electrical Discharge Energy. The surface cracks on the machined surface were more serious when the Discharge Energy was higher. The surface cracks and large Discharge craters on the machined surface markedly reduced the bending strength. Thus, using EDM process to machine cemented tungsten carbides depends on carefully setting the machining parameters to prevent surface crack.