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Mikami, Masato
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The Influence of Connecting-Rod Specifications on the Combustion-Noise Generation from a Diesel Engine

Yamaguchi University-Hitoshi Oguchi, Koki Minato, Takehiko Seo, Masato Mikami
Published 2019-06-05 by SAE International in United States
We experimentally investigated the influence of shifting natural frequencies of the internal transmission system depending on the connecting-rod specifications on the characteristics of noise radiated from a single-cylinder diesel engine. We used FFT analysis to investigate the influence of shifting natural frequencies of the internal transmission system on the radiated noise characteristics. By changing the thinned portion of the connecting-rod, we confirmed that the natural frequency of the piston-connecting-rod-coupled vibration differed from another natural frequency of the engine structure, and thus the engine noise was reduced. This research studied the time-frequency characteristics of combustion impact and engine noise by wavelet analysis of in-cylinder pressure and sound pressure. We examined the vibration-transmission characteristics through the relationship between the maximum engine noise power and the maximum combustion energy in the same cycle for the main frequencies of combustion noise. Two types of connecting-rods were used: the original connecting-rod and a connecting rod that has a short-thinned portion (STP). By shortening the thinned portion of the connecting-rod, the natural frequency of the piston-connecting-rod-coupled vibration became around 2800 Hz…
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Group Combustion Excitation in Randomly Distributed Droplet Clouds Based on Flame-spread Characteristics with Two-droplet Interaction in Microgravity

Sebelas Maret University-Herman Saputro, Laila fitriana
Yamaguchi University-Masato Mikami
  • Technical Paper
  • 2017-32-0077
Published 2017-11-05 by Society of Automotive Engineers of Japan in Japan
Experiments of flame-spread of fuel droplets have been performed in microgravity actively. However, the experiment has limitation in the number of droplets due to relatively short microgravity durations in the ground based facilities. It is difficult to conduct flame spread experiments of large scale droplet clouds in microgravity. This study conducted simulation of flame-spread behavior in randomly distributed large-scale droplet clouds by using a percolation approach, in order to make a theoretical link the gap between droplet combustion experiments and spray combustion phenomenon with considering two-droplet interaction. Droplets are arranged at lattice points in 2D lattice. The occurrence probability of group combustion (OPGC) is calculated as a function of the mean droplet spacing (S/d0)m. The (S/d0)m for 0.5 OPGC is defined as the critical mean droplet spacing (S/d0)critical, which separates the droplet cloud into two groups if the lattice size becomes infinity; relatively dense droplet clouds in which the group combustion is excited through flame spread and dilute droplet clouds in which the group combustion in is never excited. The results show that in 2D…
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Combustion and Noise Characteristics in a Diesel Engine with Hydrogen Addition and Pilot Injection

Yamaguchi University-Ryota Sakane, Toshiki Fujimura, Takehiko Seo, Masato Mikami
Published 2015-09-01 by SAE International in United States
We experimentally investigated effects of pilot diesel-fuel injection on ignition timing variation and noise reduction in a diesel engine with hydrogen addition to the intake pipe. The pilot diesel-fuel injection suppressed ignition timing variation which was significant under hydrogen addition conditions. The heat release by the pilot diesel-fuel injection stably acted as an ignition source of the hydrogen-air mixture. The maximum in-cylinder pressure rise rate increased with the hydrogen fraction. However, the sound pressure level attained minimum around a specific hydrogen fraction.
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Effects of Hydrogen Addition to Intake Mixture on Cyclic Variation of Diesel Engine

Honda R&D Co., Ltd.-Hajime Kabashima, Tomoyuki Hashimoto
Yamaguchi Univ.-Toru Miyamoto, Hirokazu Hasegawa, Takashi Yagenji, Takehiko Seo, Masato Mikami
Published 2011-08-30 by SAE International in United States
The present study experimentally investigated cyclic variation of combustion characteristics of a diesel engine with hydrogen added to the intake air in detail. As the result, there were three ignition modes: (1) hydrogen ignition mode, (2) hydrogen-assisted ignition mode, and (3) diesel-fuel ignition mode. Ignition timing fluctuated from cycle to cycle in each ignition mode and between one ignition mode and another mode. As the coolant temperature was increased, the number of cycles in diesel-fuel ignition mode decreased, and indicated thermal efficiency and cyclic variation was improved. In the case with the blow-by gas introduced to intake port, preflame reaction of blow-by gas first occurred, ignited hydrogen, and then diesel-fuel was ignited by hydrogen combustion in hydrogen ignition mode and hydrogen-assisted ignition mode.
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Investigation of Low Temperature Combustion With Hydrogen Addition to Intake Gas and High Rate EGR

Honda R&D Co., Ltd.-Hajime Kabashima, Yasuhiro Urata
Yamaguchi Univ.-Toru Miyamoto, Hirokazu Hasegawa, Masato Mikami, Naoya Kojima
  • Technical Paper
  • 2010-08-0480
Published 2010-09-29 by Society of Automotive Engineers of Japan in Japan
This study experimentally investigated low temperature diesel combustion with small amount of hydrogen added to the intake air at high EGR rate. If EGR rate is high, combustion temperature and NO emission is low. Ignition delay is prolonged by high rate EGR and hydrogen addition. Smoke emission decreases by ignition prolongation and replacement of diesel fuel by hydrogen. The present study tried to simultaneously decrease NO and smoke emission by low temperature combustion with hydrogen addition and EGR at high load condition.
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Effect of Hydrogen Fraction in Intake Mixture on Combustion and Exhaust Emission Characteristics of a Diesel Engine

Honda R&D Co., Ltd.-Hajime Kabashima, Yasuhiro Urata
Yamaguchi University-Toru Miyamoto, Masato Mikami, Naoya Kojima
Published 2009-09-13 by Consiglio Nazionale delle Ricerche in Italy
The present study experimentally investigated the performance and emission characteristics of the diesel engine with hydrogen added to the intake air at late diesel-fuel injection timings. The diesel-fuel injection timing and the hydrogen fraction in the intake mixture were varied while the gross heating value per second of diesel fuel and hydrogen was kept constant at a certain value. NO showed minimum at specific hydrogen fraction. The maximum rate of incylinder pressure rise also showed minimum at 10 vol% hydrogen fraction. The indicated thermal efficiency was almost constant or slightly increased with small amount of hydrogen. A combination of hydrogen addition and late diesel-fuel injection timing contributed to low temperature combustion, in which NO decreased without the increase in unburned fuel.
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Effects of Hydrogen Addition to Intake Mixture on Combustion and Exhaust Emission Characteristics of a Diesel Engine

Honda R&D Co., Ltd.-Hajime Kabashima, Yasuhiro Urata
Yamaguchi Univ.-Toru Miyamoto, Masato Mikami, Naoya Kojima
  • Technical Paper
  • 2009-08-0141
Published 2009-05-20 by Society of Automotive Engineers of Japan in Japan
The present study experimentally investigated the performance and emission characteristics of the diesel engine with hydrogen added to the intake air at late diesel-fuel injection timings. The diesel-fuel injection timing and the hydrogen fraction in the intake mixture were varied while the gross heating value of diesel fuel and hydrogen was kept constant at a certain value. As the hydrogen fraction was increased, NO first decreased, attained minimum, and then increased. The maximum rate of in-cylinder pressure rise also showed minimum at 10 vol% hydrogen fraction. The indicated thermal efficiency was almost constant or slightly increased with small amount of hydrogen. A combination of hydrogen addition and late diesel-fuel injection timing contributed to low temperature combustion, in which NO decreased without the increase in unburned fuel.
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Effects of Fuel Volatility on Combustion Characteristics of PCCI Diesel Engine

Honda R&D Co., Ltd.-Tomohiro Kanda
Yamaguchi University-Bansei Kobayashi, Shinji Najima, Masato Mikami, Naoya Kojima
Published 2007-07-23 by SAE International in United States
In PCCI diesel engine, the fuel is injected much earlier than the injection timing of conventional diesel engines. Exhaust-emission improvements are attained by the lean-premixed combustion. It is expected that fuel properties influence mixture formation and combustion characteristics. In this research, experiments were carried out using a single-cylinder PCCI diesel engine operating on pure fuels with different volatilities. The injection timing and overall equivalence ratio of the premixed spray were varied. The results showed that the maximum heat release rate was smaller for lower-volatility fuel while ISFC was maintained smaller. So the combustion of a lower-volatility fuel would moderately make progress.
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Development of Solid Door Closing Sound

Mazda Motor Corp.-Hiroshi Uchida, Seishi Nakamura, Katsuhisa Yamada, Kuniaki Nagano
Yamaguchi Univ.-Naoya Kojima, Masato Mikami
  • Technical Paper
  • 2002-08-0435
Published 2002-11-28 by Society of Automotive Engineers of Japan in Japan
The solidity of the door closing sound of passenger cars has been investigated. As the result of multiple regression analyses, subjective ratings of ""solidity"" well correlate to the time integral of the low frequency (under 200 Hz) loudness. For the door with good solidity closing sound, the vibration energy flow at the moment of door closing is uniform and the low frequency sound of high energy level is also radiated uniformly.
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Effects of fuel properties on exhaust and combustion characteristics of early fuel injection diesel engine

Yamaguchi Univ.-Kimitaka Akahata, Masato Mikami, Naoya Kojima
  • Technical Paper
  • 2001-08-0302
Published 2001-10-23 by Society of Automotive Engineers of Japan in Japan
The objective of this research is to investigate the effects of fuel properties on exhaust and combustion characteristics of early fuel injection diesel engine. The engine tests were carried out using diesel fuel, n-heptane, and n-tridecane as the fuels. Results showed that in the case of low-volatility fuel, the combustion phenomena were controlled by vaporization, and the occurrence of heat release delayed. Earlier fuel injection contributed to wider range of the overall equivalence ratio within which low NO emission was attained.