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Research of Fuel Components to Expand lean-limit in Super lean-burn condition

JXTG Nippon Oil & Energy Corporation-Taketora Naiki, Ken Obata, Manabu Watanabe
Keio University-Takeshi Yokomori, Norimasa Iida
  • Technical Paper
  • 2019-01-2257
Published 2019-12-19 by SAE International in United States
The thermal efficiency of internal combustion engines can be improved dramatically with the right combination of engine technology and fuel technology. Super lean-burn technology is attracting attention as a means of boosting thermal efficiency. However, there is a limit to how lean a fuel-air mixture can be before combustion becomes unstable or misfire occurs. The authors evaluated the effects of various chemical compositions on the lean limit under super lean-burn conditions. By changing the composition of the fuel, it was possible to achieve excess air ratios of over 2.0, resulting in high thermal efficiency.
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Ignition Experiments by Nanosecond Repetitively Pulsed Discharges in Intense Turbulence for Super Lean Burn at Engine Condition

Institute of Fluid Science, Tohoku University-Kodai Uesugi, Youhi Morii, Taichi Mukoyama, Takuya Tezuka, Susumu Hasegawa, Hisashi Nakamura, Hidemasa Takana
Institute of Fluid Science, Tohoku University / ICE Lab. Far-Kaoru Maruta
  • Technical Paper
  • 2019-01-2160
Published 2019-12-19 by SAE International in United States
Ignition by Nanosecond Repetitively Pulsed Discharges (NRPD) at EXponential Increase of Minimum Ignition Energy (MIE-EXI) region under super lean SI engine conditions was studied. Fundamental experiments were conducted with a turbulent ignition test chamber with twin counter-rotating fans. The MIE-EXI region by arc discharge appeared over 6500 rpm of fan speed. In the MIE-EXI region (7000 rpm), successful ignition was achieved by establishing coupled ignition kernels with NRPD at 15 kHz although ignition was unsuccessful at 1 kHz. Results show that ignition by NRPD has potential advantages for lean burn applications. Preliminary engine test results with NRPD were also demonstrated.
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Influence of ethanol blending on knocking in a lean burn SI engine

Keio University-Kazuki Kaneko, Yuki Yasutake, Takeshi Yokomori, Norimasa Iida
  • Technical Paper
  • 2019-01-2152
Published 2019-12-19 by SAE International in United States
Lean burn is one method for improving thermal efficiency in spark ignition (SI) engines. Suppression of knocking provides higher thermal efficiency, and ethanol blending is considered an effective way to suppress knocking due to its high octane and high latent heat of evaporation.We investigate the effect of ethanol blending on knocking in an SI engine under lean operating conditions. The Livengood-Wu (LW) integral was performed based on ignition delay duration estimated from a zero-dimensional detailed chemical reaction calculation with pressure and temperature histories.Knocking was suppressed and thermal efficiency increased with ethanol-gasoline blending fuel, even at 0.5 equivalence ratio. Decrease in unburned gas temperature by latent heat of evaporation had a comparable influence on knocking suppression, which was supported by LW integral analysis.
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A Cycle-to-Cycle Variation Extraction Method for Flow Field Analysis in SI IC Engines Based on Turbulence Scales

Keio University-Masayoshi Matsuda, Takeshi Yokomori, Norimasa Iida
Tokyo Institute of Technology-Yuki Minamoto, Masayasu Shimura, Mamoru Tanahashi
Published 2019-01-15 by SAE International in United States
To adhere to stringent environmental regulations, SI (spark ignition) engines are required to achieve higher thermal efficiency. In recent years, EGR (exhaust gas recirculation) systems and lean-burn operation has been recognized as key technologies. Under such operating conditions, reducing CCV (cycle-to-cycle variation) in combustion is critical to the enhancement of overall engine performance. Flow-field CCV is one of the considerable factors affecting combustion in engines. Conventionally, in research on flow fields in SI engines, the ensemble average is used to separate the measured velocity field into a mean component and a fluctuation component, the latter of which contains a CCV component and a turbulent component. To extract the CCV of the flow field, previous studies employed spatial filter, temporal filter, and POD (proper orthogonal decomposition) methods. Those studies used a constant- separation filter size for the whole crank angle, although the turbulence scales change rapidly during the intake and compression stroke processes. Hence the definition of filter size has some room to be explored in order to take account of these features. The objective of…
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Effect of Temperature-Pressure Time History on Auto-Ignition Delay of Air-Fuel Mixture

Honda R&D-Katsuya Matsuura
Keio University-Norimasa Iida
Published 2018-09-10 by SAE International in United States
When the compression ratio of the spark ignition engine is set high as a method of improving the fuel efficiency of passenger cars, it is often combined with the direct fuel injection system for knock mitigation. In port injection, there are also situations where the fuel is guided into the cylinder while the vaporization is insufficient, especially at the cold start. If the fuel is introduced into the cylinder in a liquid state, the temperature in the cylinder will change due to sensible heat and latent heat of the fuel during vaporization. Further, if the fuel is unevenly distributed in the cylinder, the effect of the specific heat is added, and the local temperature difference is expanded through the compression process.In this research, an experiment was conducted using a rapid compression machine for the purpose of discussing the effect of the temperature-pressure time history of fuel on ignition delay time. From the results, it was confirmed that the ignition timing can be advance and retard depending on the temperature-pressure history regardless of the time for…
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The Effect of Fuel Composition on Ignition Delay and Knocking in Lean Burn SI Engine

Keio University-Yasunobu Goto, Dongwon Jung, Toshihisa Ueda, Norimasa Iida
  • Technical Paper
  • 2017-32-0112
Published 2017-11-05 by Society of Automotive Engineers of Japan in Japan
Super lean burn technology is conceived as one of methods for improving the thermal efficiency of SI engines[1][2]. For lean burn, reduction of heat loss and the due to decrease in flame temperature can be expected. However, as the premixed gas dilutes, the combustion speed decreases, so the combustion fluctuation between cycles increases. Also, to improve the thermal efficiency, the ignition timing is advanced to advance the combustion phase. However, when the combustion phase is excessively advanced, knocking occurs, which hinders the improvement of thermal efficiency. Knocking is a phenomenon in which unburned gas in a combustion chamber compressed by a piston and combustion gas suffer compression auto-ignition. It is necessary to avoid knocking because the amplitude of the large pressure wave may cause noise and damage to the engine. Also, knocking is not a steady phenomenon but a phenomenon that fluctuates from cycle to cycle. Many studies have already been made on the knocking characteristics that occurred during stoichiometric combustion[3], but there have been no reports on knocking characteristics in super lean burn near…
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Effects of Spark Discharge Characteristic on Cycle-to-Cycle Variations of Combustion for Lean SI Operation with High Tumble Flow

Keio University-Kosaku Sasaki, Dongwon Jung, Takeshi Yokomori, Norimasa Iida
  • Technical Paper
  • 2017-32-0111
Published 2017-11-05 by Society of Automotive Engineers of Japan in Japan
It has been shown that lean burn is effective for improving the thermal efficiency of gasoline SI engines. This happens because the reduction of heat loss by decrease of flame temperature. On the other hand, the fuel dilution of the premixed gas makes the combustion speed low, and cycle-to-cycle variations of combustion are increased by excessive dilution, it is difficult to increase the thermal efficiency of the gasoline SI engine. Influence of ignition by spark discharge is considered as a factor of combustion variation, and it is necessary to understand the effects of spark discharge characteristics on the lean combustion process. Spark discharge in the SI engines supplies energy to the premixed-gas via a discharge channel in the spark plug gap which ignites the premixed-gas. The discharge channel is elongated by in-cylinder gas flow and its behavior varies in each cycles. When the discharge channel is elongated, the premixed-gas on the discharge channel increases and the gap resistance increases. As a result, the pattern of the discharge energy supply to the premixed gas by the…
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Investigation of Cycle-to-Cycle Variation of Turbulent Flow in a High-Tumble SI Engine

Keio Univ.-Masayoshi Matsuda, Takeshi Yokomori, Norimasa Iida
Published 2017-10-08 by SAE International in United States
The thermal efficiency of a spark-ignition (SI) engine must be improved to reduce both environmental load and fuel consumption. Although lean SI engine operation can strongly improve thermal efficiency relative to that of stoichiometric SI operation, the cycle-to-cycle variation (CCV) of combustion increases with the air dilution level. Combustion CCV is caused by CCVs of many factors, such as EGR, spark energy, air-fuel ratio, and in-cylinder flow structure related to engine speed. This study focuses on flow structures, especially the influence of a tumble structure on flow fluctuation intensity near ignition timing. We measured the flow field at the vertical center cross section of an optically accessible high-tumble flow engine using time-resolved particle image velocimetry. There are many factors considered to be sources of CCV, we analyzed three factors: the intake jet distribution, distribution of vortex core position and trajectory of the fluid particle near the spark plug. To estimate the trajectory of fluid particle, the flow structure near the spark plug is tracked backward from the ignition timing to the intake stroke. The CCV…
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Combined Effects of Spark Discharge Pattern and Tumble Level on Cycle-to-Cycle Variations of Combustion at Lean Limits of SI Engine Operation

Keio University-Dongwon Jung, Kosaku Sasaki, Kenji Sugata, Masayoshi Matsuda, Takeshi Yokomori, Norimasa Iida
Published 2017-03-28 by SAE International in United States
Improving the thermal efficiency of spark ignition (SI) engine is strongly required due to its widespread use but considerably less efficiency than that of compression ignition (CI) engine. 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 increases with the level of air dilution, and becomes unacceptable. To improve the stability of lean operation, this study examines the effects of spark discharge pattern and tumble level on cycle-to-cycle variations of combustion at lean limits. The spark discharge pattern was altered by a custom inductive ignition system using ten spark coils and the tumble level was increased by a custom adapter installed in the intake port (tumble adapter).The results show that increased discharge energy by ten spark coils (without discharge offset) extends the lean limits with an improvement of indicated thermal efficiency (ηth), relative to that of stoichiometric operation. Furthermore, a combination of increased discharge energy and higher tumble level by tumble adapter makes it possible to allow stable…
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Effect of Heat Release Pattern of Flame during Propagation on Auto-Ignition Process of End-Gas

Honda R&D Co.,Ltd. Automobile R&D Center-Katsuya Matsuura, Yoshihisa Sato
Keio University-Keito Nakano, Keisuke Shimizu, Norimasa Iida
Published 2016-04-05 by SAE International in United States
Knock is a factor hindering enhancement of the thermal efficiency of spark ignition engines, and is an unsteady phenomenon that does not necessarily occur each cycle. In addition, the heat release history of the flame also fluctuates from cycle to cycle, and the auto-ignition process of the unburned mixture (end-gas), compressed by the global increase in pressure due to release of chemical energy, is affected by this fluctuation. Regarding auto-ignition of the end-gas, which can be the origin of knock, this study focused on the fluctuation of the flame heat release pattern, and used a zero-dimensional (0D) detailed chemical reaction calculation in an attempt to analyze and examine the consequence on the end-gas compression and auto-ignition process of changes in the i) start of combustion, ii) combustion duration and iii) center of heat release of the flame.The results showed that the compression speed of the end-gas varies according to the heat release pattern of the flame, and the ignition delay is affected by the compression speed. Furthermore, when the compression speed is slow, the temperature…
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