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DRASTIC IMPROVEMENT OF THERMAL EFFICIENCY BY RAPID PISTON-MOVEMENT NEAR TDC
Moriyoshi, Y.,Sano, M.,Morikawa, K.,Kaneko, M. The Korean Society of Automotive Engineers 2006 International journal of automotive technology Vol.7 No.3
A new combustion method of high compression ratio SI engine was studied and proposed in order to achieve high thermal efficiency, comparable to that of CI engine. Compression ratio of SI engine is generally restricted by the knocking phenomena. A combustion chamber profile and a cranking mechanism were studied to avoid knocking with high compression ratio. Because reducing the end-gas temperature will suppress knocking, a combustion chamber was considered to have a wide surface at the end-gas region. However, wide surface will lead to large heat loss, which may cancel the gain of higher compression ratio operation. Thereby, a special cranking mechanism was adapted which allowed the piston to move rapidly near TDC. Numerical simulations were performed to optimize the cranking mechanism for achieving high thermal efficiency. An elliptic gear system and a leaf-shape gear system were employed in numerical simulations. Livengood-Wu integral, which is widely used to judge knocking occurrence, was calculated to verify the effect for the new concept. As a result, this concept can be operated at compression ratio of fourteen using a regular gasoline. A new single cylinder engine with compression ratio of twelve and TGV(Tumble Generation Valve) to enhance the turbulence and combustion speed was designed and built for proving its performance. The test results verified the predictions. Thermal efficiency was improve over 10% with compression ratio of twelve compared to an original engine with compression ratio of ten when strong turbulence was generated using TGV, leading to a fast combustion speed and reduced heat loss.
Charge Density Distributions in Bi4Ti3O12 and Bi3.25La0.75Ti3O12 in the Paraelectric Phase
Chikako Moriyoshi,Sayaka Kimura,Yoshihiro Kuroiwa,김수재,Yuji Noguchi 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
The electron charge density distributions of the bismuth layered ferroelectric materials Bi4Ti3O12 (BiT) and Bi3.25La0.75Ti3O12 (BLT) in the paraelectric phase are demonstrated by analyzing the high-energy synchrotron-radiation powder-diffraction data on the basis of the maximum entropy method (MEM)/Rietveld method. The crystal structures of BiT and BLT are quite similar, and no significant difference is observed in the chemical bonding nature in the paraelectric phase. This result differs from the experimental fact that, in the ferroelectric phase, electron orbital hybridization between Bi and O in the perovskite layer is formed along the a-axis in BiT while the hybridization between Bi/La and O is revealed not only along the a-axis but also along the b-axis in BLT. We attribute the unchanged Curie temperatures for the Bi4−xLaxTi3O12 system to the same crystal structures, including the chemical bonding nature, in the paraelectric phase. The electron charge density distributions of the bismuth layered ferroelectric materials Bi4Ti3O12 (BiT) and Bi3.25La0.75Ti3O12 (BLT) in the paraelectric phase are demonstrated by analyzing the high-energy synchrotron-radiation powder-diffraction data on the basis of the maximum entropy method (MEM)/Rietveld method. The crystal structures of BiT and BLT are quite similar, and no significant difference is observed in the chemical bonding nature in the paraelectric phase. This result differs from the experimental fact that, in the ferroelectric phase, electron orbital hybridization between Bi and O in the perovskite layer is formed along the a-axis in BiT while the hybridization between Bi/La and O is revealed not only along the a-axis but also along the b-axis in BLT. We attribute the unchanged Curie temperatures for the Bi4−xLaxTi3O12 system to the same crystal structures, including the chemical bonding nature, in the paraelectric phase.
Development of a Spray Model for Swirl-Type Gasoline DI Injectors
Yasuo Moriyoshi,Masahide Takagi,Xiao Hu 한국자동차공학회 2001 한국자동차공학회 Symposium Vol.- No.-
Prediction of the mixture formation process inside a gasoline DI engine is strongly required to improve both the fuel consumption rate and the exhaust gas emissions. A swirl-type injector, widely used for a gasoline DI engine, is characterized with drastic changes of the cone angle caused by ambient pressure. Numerical simulations of a free spray formed by a swirl-type injector have been carried out on the basis of a method of DDM (Discrete Droplet Model). In this study, firstly the ambiguity how to give the initial conditions is discussed. Secondly, the droplet deformation calculated by a breakup model was incorporated into the drag force tenn to take the influence of the drag variation into account. As a result. by performing optimizations of the initial conditions, the breakup models and the drag force model, spray characteristics of a swirl-type injector were predicted quantitatively.<br/> <br/>
DRASTIC IMPROVEMENT OF THERMAL EFFICIENCY BY RAPID PISTON-MOVEMENT NEAR TDC
Y. MORIYOSHI,M. SANO,K. MORIKAWA,M. KANEKO 한국자동차공학회 2006 International journal of automotive technology Vol.7 No.3
A new combustion method of high compression ratio SI engine was studied and proposed in order to achieve high thermal efficiency, comparable to that of CI engine. Compression ratio of SI engine is generally restricted by the knocking phenomena. A combustion chamber profile and a cranking mechanism were studied to avoid knocking with high compression ratio. Because reducing the end-gas temperature will suppress knocking, a combustion chamber was considered to have a wide surface at the end-gas region. However, wide surface will lead to large heat loss, which may cancel the gain of higher compression ratio operation. Thereby, a special cranking mechanism was adapted which allowed the piston to move rapidly near TDC. Numerical simulations were performed to optimize the cranking mechanism for achieving high thermal efficiency. An elliptic gear system and a leaf-shape gear system were employed in numerical simulations. Livengood-Wu integral, which is widely used to judge knocking occurrence, was calculated to verify the effect for the new concept. As a result, this concept can be operated at compression ratio of fourteen using a regular gasoline. A new single cylinder engine with compression ratio of twelve and TGV (Tumble Generation Valve) to enhance the turbulence and combustion speed was designed and built for proving its performance. The test results verified the predictions. Thermal efficiency was improve over 10% with compression ratio of twelve compared to an original engine with compression ratio of ten when strong turbulence was generated using TGV, leading to a fast combustion speed and reduced heat loss.
Analysis of Mixture Formation and Combustion Process in a DISC Engine
Yasuo, Moriyoshi 경상대학교 공과대학 항공기계공학부 1999 WORKSHOP 자료집 Vol.1999 No.1
In this report, the author has, briefly introduced research summary on the stratified charge combustion system that has a possibility of simultaneous reduction of exhaust emissions and fuel' consumption rate. Firstly, the effect of spatial distribution of mixture stratification on combustion characteristics was investigated using a constant volume chamber. Secondly, the break-up process of fuel spray was examined to control the mixture formation process. Thirdly, turbulence and combustion modeling was discussed as a tool to clarify the physical phenomena. Finally, a model GDI engine was employed to evaluate a new concept.
Kim, Seok-Woo,Moriyoshi, Yasuo The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.8
A two-stroke Schnurle-type gasoline engine was modified to enable compression-ignition in both the port fuel injection and the in-cylinder direct injection. Using the engine, examinations of compression-ignition operation and engine performance tests were carried out. The amount of the residual gas and the in-cylinder mixture conditions were controlled by varying the valve angle rate of the exhaust valve (VAR) and the injection timing for direct injection conditions. It was found that the direct injection system is superior to the port injection system in terms of exhaust gas emissions and thermal efficiency, and that almost the same operational region of compression-ignition at medium speeds and loads was attained. Some interesting combustion characteristics, such as a shorter combustion period in higher engine speed conditions, and factors for the onset of compression-ignition were also examined.
Origin of Ultrahigh Dielectric Constants for Barium Titanate Nanoparticles
Satoshi Wada,C Moriyoshi,H. Yasuno,K Kakemoto,K Takizawa,M Ohishi,T Hoshina,T Tsurumi,Y Kuroiwa 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
Barium titanate (BaTiO3) nanoparticles with various particle sizes from 17 to 1,000 nm were prepared by using the 2-step thermal decomposition method of barium titanyl oxalate under various degree of vacuum. Various characterizations revealed that these particles were impurity-free, defectfree, dense BaTiO3 nanoparticles. When the degree of vacuum was high (pressure of 150 Pa at 650 C), the dielectric constant of BaTiO3 particles with a size of around 60 nm exhibited a maximum of around 15,000. On the other hand, when the degree of vacuum was low (pressure of 400 Pa at 650 C), no dielectric maximum was observed. To explain this size dependence, we precisely investigated a particle structure by using synchrotron radiation. As a result, the particles were always composed of two layers, i.e., a surface cubic layer and a bulk tetragonal layer, and the thickness of the surface cubic layer decreased with increasing degree of vacuum during the preparation of BaTiO3 nanoparticles. Thus, we confirmed that the surface structure was an important factor in determining the dielectric properties of BaTiO3 nanoparticles.