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A Study of Particulate Emission Formation Mechanism from Injector Tip in Direct-Injection Gasoline Engines

SAE International Journal of Advances and Current Practices in Mobility

Nissan Motor Co., Ltd.-Yoshihiro Imaoka, Yutaka Hashizume, Takao Inoue, Taisuke Shiraishi
  • Journal Article
  • 2019-01-2244
Published 2019-12-19 by SAE International in United States
The mechanism causing in-cylinder injector tip soot formation, which is the main source of particle number (PN) emissions under operating conditions after engine warm-up, was analyzed in this study. The results made clear a key parameter for reducing injector tip soot PN emissions. An evaluation of PN emissions for different amounts of injector tip wetting revealed that an injector with larger tip wetting forms higher PN emissions. The results also clarified that the amount of deposits does not have much impact on PN emissions. The key parameter for reducing injector tip soot is injector tip wetting that has a linear relationship with injector tip soot PN emissions.
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A Study of Combustion Technology for a High Compression Ratio Engine: The Influence of Combustion Chamber Wall Temperature on Knocking

SAE International Journal of Engines

Nissan Motor Co., Ltd.-Yoshihiro Imaoka, Kiyotaka Shouji, Takao Inoue, Toru Noda
  • Journal Article
  • 2016-01-0703
Published 2016-04-05 by SAE International in United States
Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio is an example of a technology for improving the thermal efficiency of gasoline engines. A significant issue of a high compression ratio engine for improving fuel economy and low-end torque is prevention of knocking under a low engine speed. Knocking is caused by autoignition of the air-fuel mixture in the cylinder and seems to be largely affected by heat transfer from the intake port and combustion chamber walls. In this study, the influence of heat transfer from the walls of each part was analyzed by the following three approaches using computational fluid dynamics (CFD) and experiments conducted with a multi-cooling engine system. First, the temperature rise of the air-fuel mixture by heat transfer from each part was analyzed. Heat transfer from the intake port and cylinder head was found to be higher than that from other parts due to the high flow velocity during the intake stroke. Therefore,…
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A Study of a Multistage Injection Mechanism for Improving the Combustion of Direct-Injection Gasoline Engines

SAE International Journal of Engines

Nissan Motor Co., Ltd.-Yoshihiro Imaoka, Kiyotaka Shouji, Takao Inoue, Toru Noda
  • Journal Article
  • 2015-01-0883
Published 2015-04-14 by SAE International in United States
Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio for improving thermal efficiency and downsizing the engine based on fuel-efficient operating conditions are good examples of technologies for enhancing gasoline engine fuel economy. A direct-injection system is adopted for most of these engines. Direct injection can prevent knocking by lowering the in-cylinder temperature through fuel evaporation in the cylinder. Therefore, direct injection is highly compatible with downsized engines that frequently operate under severe supercharging conditions for improving fuel economy as well as with high compression ratio engines for which susceptibility to knocking is a disadvantage. On the other hand, direct-injection engines have certain issues such as the need to reduce particulate matter (PM) emissions, and technical measures must be developed for that purpose. Multistage injection is one method of improving direct-injection engines and has both advantages and disadvantages. One benefit of multistage injection is lower PM emissions caused by liquid fuel impinging on the cylinder wall. That…
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Improvement of Combustion Stability under Cold Ambient Condition by Mixture Control

SAE International Journal of Engines

Nissan Motor Co., Ltd.-Manabu Hasegawa, Toru Nishizawa, Yoshihiro Imaoka, Keiji Kawamoto, Atsushi Teraji, Shuichi Iio
  • Journal Article
  • 2013-01-1303
Published 2013-04-08 by SAE International in United States
For diesel engine, lower compression ratio has been demanded to improve fuel consumption, exhaust emission and maximum power recently. However, low compression ratio engine might have combustion instability issues under cold temperature condition, especially just after engine started.As a first step of this study, cold temperature combustion was investigated by in-cylinder pressure analysis and it found out that higher heat release around top dead center, which was mainly contributed by pilot injection, was the key factor to improve engine speed fluctuation.For further understanding of combustion in cold condition, particularly mixture formation near a glow plug, 3D CFD simulation was applied. Specifically for this purpose, TI (Time-scale Interaction) combustion model has been developed for simulating combustion phenomena. This model was based on a reasonable combustion mode, taking into account the characteristic time scale of chemical reactions and turbulence eddy break-up. In addition, parameters of the ignition model and computational grids near glow plug were improved to apply under cold start conditions.As a result, the result of this study reveal that controlling an equivalence ratio and temperature…
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Study of Improvement for Combustion Stability Under Cold Start Condition of DI Diesel Engine (First Report)~Study for Improvement of Combustion Stability by Multiple Injection

Nissan-Toru Nishizawa, Yoshihiro Imaoka, Shuichi Iio, Manabu Hasegawa, Keiji Kawamoto
  • Technical Paper
  • 2012-08-0602
Published 2012-10-03 by Society of Automotive Engineers of Japan in Japan
For diesel engine, more lower compression ratio has been demanded to improve fuel consumption, output power and emission recently. However, low compression ratio engine may have some issues in combustion instability under cold start condition. In this study, the validity of the multi pilot injection which was combustion instability improvement methods of diesel engine was considered using the combustion analysis by cylinder pressure sensor with glow plug function and CFD simulation which was improved to apply under cold start condition. As a result, it was found that controlling the equivalence ratio and temperature surrounding glow plug appropriately by multi pilot injection was contributing to the improvement of combustion stability under cold start condition.
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Study of Improvement for Combustion Stability Under Cold Start Condition of DI Diesel Engine (2nd Rep.): Application of TI (Time-Scale Interaction) Combustion Model for Cold Start Condition

Nissan-Yoshihiro Imaoka, Toru Nishizawa, Shuichi Iio, Atsushi Teraji, Manabu Hasegawa, Keiji Kawamoto
  • Technical Paper
  • 2012-08-0603
Published 2012-10-03 by Society of Automotive Engineers of Japan in Japan
Diesel engines of low compression ratio have issues of white smoke and combustion instability under cold start conditions. TI (Time-scale Interaction) combustion model applied cold start conditions in order to resolve those issues. TI combustion model has been developed for simulating combustion phenomena with high accuracy from premixed charged combustion to diffusion combustion. This model is based on a reasonable combustion mode, taking into account the characteristic time scale of chemical reactions and turbulence eddy break-up. In addition, parameters of the ignition model and computational grids near glow-plug were improved to apply under cold start conditions. Comparisons of measured and calculated heat release patterns show good agreement under cold conditions. It was shown by application of TI combustion model under cold start conditions that the fuel reaction near the glow plug is significant for ignition.
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Development of a Three-Dimensional Diesel Combustion Model Considering Premixed Region

NISSAN MOTOR CO., LTD.-Yoshihiro Imaoka, Atsushi Teraji, Tsuyoshi Tsuda, Toru Noda, Masaaki Kubo, Shuji Kimura
  • Technical Paper
  • 2007-08-0611
Published 2007-10-01 by Society of Automotive Engineers of Japan in Japan
Diesel combustion is a complex process, including autoignition, premixed combustion and diffusion combustion. A novel TI (Time-scale Interaction) combustion model has been developed for simulating combustion phenomena with high accuracy from premixed charged combustion to diffusion combustion. This model is based on a reasonable combustion mode, taking into account the characteristic time scale of chemical reactions and turbulence eddy break-up. Comparisons of measured and calculated heat release patterns and pressure histories showed good agreement for various operating conditions. The diesel combustion mechanism was analyzed under several fuel injection timings and engine loads using TI combustion model.