The Experts below are selected from a list of 78 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.
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the effects of key parameters on the tranSItion from SI Combustion to hcci Combustion in a two stroke free piston linear engine
Applied Energy, 2015Co-Authors: Nguyen Ba Hung, Norimasa IidaAbstract:An investigation was conducted to examine the effects of key parameters such as intake temperature, equivalence ratio, engine load, intake pressure, spark timing and spring stiffness on the tranSItion from SI Combustion to HCCI Combustion in a two-stroke free piston linear engine. Operation of the free piston engine was SImulated based on the combination of three mathematical models including a dynamic model, a linear alternator model and a thermodynamic model. These mathematical models were combined and solved by a program written in Fortran. To validate the mathematical models, the SImulation results were compared with experimental data in the SI mode. For the tranSItion from SI Combustion to HCCI Combustion, the SImulation results show that if the equivalence ratio is decreased, the intake temperature and engine load should be increased to get a successful SI-HCCI tranSItion. However, the SImulation results also show that the in-cylinder pressure is decreased, while the peak in-cylinder temperature in HCCI mode is increased SIgnificantly if the intake temperature is increased so much. BeSIde the successful SI-HCCI tranSItion, the increase of intake pressure from Pin=1.1bar to Pin=1.6bar is one of solutions to reduce peak in-cylinder temperature in HCCI mode. However, the SImulation results also indicate that if the intake pressure is increased so much (Pin=1.6bar), the engine knocking problem is occurred. Adjusting spring stiffness from k=2.9N/mm to k=14.7N/mm is also conSIdered one of useful solutions for reducing the peak in-cylinder temperature in HCCI mode as well as avoiding engine knock. BeSIdes, the change of spark timing is suggested as a benefic method to help the control of the SI-HCCI tranSItion to be more convenient. To get a successful SI-HCCI tranSItion with reducing of peak temperature in HCCI mode as well as avoiding engine knock, the SImulation results show that the engine should be operated with following conditions: equivalence ratio ϕ=0.7, engine load RL=180Ω, intake temperature Tin=400K, intake pressure Pin=1.2bar, spark timing in SI mode xig=3mm and spring stiffness k=14.7N/mm.
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.
Jianxin Wang - One of the best experts on this subject based on the ideXlab platform.
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a comparative study of uSIng diesel and poden as pilot fuels for natural gas dual fuel Combustion
Fuel, 2017Co-Authors: Heping Song, Changpeng Liu, Zhi Wang, Shijin Shuai, Jianxin WangAbstract:Abstract Compared to natural gas spark-ignition (SI) Combustion, dual-fuel (DF) mode could achieve higher indicated thermal efficiency (ITE). The major disadvantages of natural gas DF Combustion are rough Combustion at high load, high CO and total hydrocarbon (THC) emisSIons, and low natural gas substitution rate. In the present work, a comparison of uSIng polyoxymethylene dimethyl ethers (PODEn) and diesel as pilot fuels for natural gas DF Combustion is presented. The experiments were conducted at two conditions: 1000 rpm 4 bar indicated mean effective pressure (IMEP), and 1000 rpm 12 bar IMEP. Compressed natural gas (CNG) was injected into the intake manifold and pilot fuel was injected directly into the cylinder. The experiments covered both conventional and low temperature DF Combustion. Experiments were conducted with 0% exhaust gas recirculation (EGR) and 60% CNG substitution ratio at 4 bar IMEP. At 12 bar IMEP, 90% substitution ratio and 30% EGR rate were chosen. The impact of the start of pilot fuel injection (SOI) on natural gas DF Combustion was studied. In comparison with the conventional Combustion, low temperature Combustion reduced NOx emisSIons and improved ITE. Compared to diesel, PODEn achieved lower THC, CO, NOx, soot emisSIons and higher efficiency, indicating it is a promiSIng pilot fuel for natural gas DF Combustion.
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comparative study on gasoline homogeneous charge induced ignition hcii by diesel and gasoline diesel blend fuels gdbf Combustion
Fuel, 2013Co-Authors: Jianxin Wang, Zhi Wang, Shijin ShuaiAbstract:Abstract Gasoline Homogeneous Charge Induced Ignition (HCII) by diesel uses port fuel injection of gasoline to form a homogeneous charge and direct injection of diesel fuel as an ignition source. Gasoline/Diesel Blend Fuels (GDBFs) uses a premixed blend of diesel and gasoline which is directly injected into the cylinder for Combustion. Exploratory studies show that these two ways may integrate the advantages of gasoline and diesel fuels to achieve high thermal efficiency and low emisSIon targets. Combustion characteristics, emisSIon characteristics, thermal efficiency and adaptability of low-temperature Combustion in these two Combustion modes have been comparatively investigated on a high-pressure common rail SIngle-cylinder diesel engine. The results show that both HCII and GDBF modes can achieve higher thermal efficiency than gasoline SI Combustion and a SImilar or even higher thermal efficiency than diesel CI Combustion because the Combustion was closer to constant volume Combustion. As gasoline ratio increases, the fuel–air mixing is improved in both HCII and GDBF modes, and thus soot emisSIons reduced dramatically, with a biggest reduction of 90%. The ignition delay in HCII mode remained almost the same, while the ignition delay in GDBF mode increased SIgnificantly with the increase of gasoline ratio. As gasoline ratio increases, the Combustion duration in both HCII and GDBF modes shortened SIgnificantly. Both HCII and GDBF modes can achieve low temperature Combustion with extremely low soot and NO emisSIons when combined with large amounts of EGR. These modes demonstrate an advantage over the diesel CI Combustion mode, where the NO emisSIons decreased and soot emisSIons increased with the increase of EGR, exhibiting the clasSIcal NO-soot trade-off.
Shijin Shuai - One of the best experts on this subject based on the ideXlab platform.
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a comparative study of uSIng diesel and poden as pilot fuels for natural gas dual fuel Combustion
Fuel, 2017Co-Authors: Heping Song, Changpeng Liu, Zhi Wang, Shijin Shuai, Jianxin WangAbstract:Abstract Compared to natural gas spark-ignition (SI) Combustion, dual-fuel (DF) mode could achieve higher indicated thermal efficiency (ITE). The major disadvantages of natural gas DF Combustion are rough Combustion at high load, high CO and total hydrocarbon (THC) emisSIons, and low natural gas substitution rate. In the present work, a comparison of uSIng polyoxymethylene dimethyl ethers (PODEn) and diesel as pilot fuels for natural gas DF Combustion is presented. The experiments were conducted at two conditions: 1000 rpm 4 bar indicated mean effective pressure (IMEP), and 1000 rpm 12 bar IMEP. Compressed natural gas (CNG) was injected into the intake manifold and pilot fuel was injected directly into the cylinder. The experiments covered both conventional and low temperature DF Combustion. Experiments were conducted with 0% exhaust gas recirculation (EGR) and 60% CNG substitution ratio at 4 bar IMEP. At 12 bar IMEP, 90% substitution ratio and 30% EGR rate were chosen. The impact of the start of pilot fuel injection (SOI) on natural gas DF Combustion was studied. In comparison with the conventional Combustion, low temperature Combustion reduced NOx emisSIons and improved ITE. Compared to diesel, PODEn achieved lower THC, CO, NOx, soot emisSIons and higher efficiency, indicating it is a promiSIng pilot fuel for natural gas DF Combustion.
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comparative study on gasoline homogeneous charge induced ignition hcii by diesel and gasoline diesel blend fuels gdbf Combustion
Fuel, 2013Co-Authors: Jianxin Wang, Zhi Wang, Shijin ShuaiAbstract:Abstract Gasoline Homogeneous Charge Induced Ignition (HCII) by diesel uses port fuel injection of gasoline to form a homogeneous charge and direct injection of diesel fuel as an ignition source. Gasoline/Diesel Blend Fuels (GDBFs) uses a premixed blend of diesel and gasoline which is directly injected into the cylinder for Combustion. Exploratory studies show that these two ways may integrate the advantages of gasoline and diesel fuels to achieve high thermal efficiency and low emisSIon targets. Combustion characteristics, emisSIon characteristics, thermal efficiency and adaptability of low-temperature Combustion in these two Combustion modes have been comparatively investigated on a high-pressure common rail SIngle-cylinder diesel engine. The results show that both HCII and GDBF modes can achieve higher thermal efficiency than gasoline SI Combustion and a SImilar or even higher thermal efficiency than diesel CI Combustion because the Combustion was closer to constant volume Combustion. As gasoline ratio increases, the fuel–air mixing is improved in both HCII and GDBF modes, and thus soot emisSIons reduced dramatically, with a biggest reduction of 90%. The ignition delay in HCII mode remained almost the same, while the ignition delay in GDBF mode increased SIgnificantly with the increase of gasoline ratio. As gasoline ratio increases, the Combustion duration in both HCII and GDBF modes shortened SIgnificantly. Both HCII and GDBF modes can achieve low temperature Combustion with extremely low soot and NO emisSIons when combined with large amounts of EGR. These modes demonstrate an advantage over the diesel CI Combustion mode, where the NO emisSIons decreased and soot emisSIons increased with the increase of EGR, exhibiting the clasSIcal NO-soot trade-off.
Sotirios Mamalis - One of the best experts on this subject based on the ideXlab platform.
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experimental study of lean spark ignition Combustion uSIng gasoline ethanol natural gas and syngas
Fuel, 2019Co-Authors: Deivanayagam Hariharan, Benjamin Lawler, Sotirios MamalisAbstract:Abstract In the development of internal Combustion engines, engineers and researchers are facing the challenge of improving engine efficiency while reducing harmful exhaust emisSIons. Previous research has shown that lean Combustion is one of the viable techniques that can improve engine efficiency while effectively reducing exhaust emisSIons. Lean burn engines operate at low burned gas temperatures and can achieve high thermal efficiency based on favorable mixture thermodynamic properties. However, under high dilution levels, a lean misfire limit is reached where the Combustion process becomes unstable and incomplete Combustion starts to occur. Instability SIgnificantly affects engine efficiency, driveability, and exhaust emisSIons, which limit the full potential of lean burn engines. The lean misfire limit is not only dependent on engine deSIgn but also on fuel properties. Therefore, fuels that are conducive to lean Combustion can provide the opportunity for enhanced efficiency and reduced emisSIons. Spark ignited (SI) Combustion with conventional gasoline has shown to have relatively narrow range of fuel-air equivalence ratio; therefore, it is deSIred to explore the lean limit of SI Combustion by uSIng alternative fuels, which can also contribute to the reduction of greenhouse gas emisSIons from transportation and power generation. Experiments were conducted on a Cooperative Fuel Research (CFR) engine with varying fuel-air equivalence ratio (φ) to assess the engine performance and emisSIons with three alternative fuels, natural gas, ethanol, and syngas, at compresSIon ratio of 8:1 and engine speed of 1200 rev/min. Equivalence ratio was varied by decreaSIng the mass of fuel while keeping the mass of air the same. The lean misfire limit was defined as the equivalence ratio where the CoV of IMEP across multiple consecutive engine cycles was greater than 5%. It was found that syngas can maintain stable Combustion at extremely lean conditions and has the lowest lean misfire limit. Natural gas Combustion achieved a lower lean misfire limit than gasoline and ethanol. Gasoline and ethanol had SImilar lean misfire limits, but it was found that gasoline helped the engine to achieve higher load and fuel converSIon efficiency compared to the three alternative fuels.