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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/>
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.
Seok Woo Kim,Yasuo Moriyoshi 대한기계학회 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.
( Shunsuke Gotoh ),( Tatsuya Kuboyama ),( Yasuo Moriyoshi ),( Koichi Hatamura ),( Junichi Takanashi ),( Toshio Yamada ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-
The objective of this research is to extend the HCCI operational range by using direct fuel injection system and also our original blowdown supercharge (BDSC) system. The effect of in-cylinder fuel distribution on HCCI operational range was numerically and experimentally investigated. Firstly, a numerical simulation using a multi zone reaction model was carried out. The results showed that a uniform fuel distribution decreases the pressure rise rate (dP/dθ) with the thermal distribution generated by the BDSC system. Next, experiments were carried out using a gasoline engine equipped with the direct fuel injection and BDSC systems. The fuel injection timing, the fuel mass ratio between the direct injection and the port injection was varied as an experimental parameter to investigate the effect of the fuel distribution on the high load HCCI operational limits. The experimental results showed that the HCCI operational robustness at the high load operation was successfully improved by using the direct fuel injection. However, high load HCCI operational limit was hardly extended. Next, by using the endothermic effect of fuel, enhancement of thermal stratification was tested. However, the relationship between CA50 and dP/dθmax was not improved.
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.
2D Analysis of Droplet Size Distribution of Diesel Sprays by using Improved ILIDS Method
( Chang Seong Ryu ),( Yasuo Moriyoshi ),( Masato Yamada ),( Yuzo Aoyagi ) 한국액체미립화학회 2005 한국액체미립화학회 학술강연회 논문집 Vol.2005 No.-
The characteristics of Diesel spray, such as droplet size, velocity and droplet size distribution were simultaneously measured by using an improved ILIDS (Interferometric Laser Imaging for Droplet Sizing) method. Experiments were performed with an accumulator type unit injector system and a constant-volume high-pressure vessel. The injection pressure and ambient gas pressure were changed from 50 MPa to 100 MPa and up to 1 MPa, respectively. Injection duration was set at 2 ms and measurements were made at 3.5 ms after the start of injection. A single hole nozzle with orifice diameter of 0.244 mm was used. The measurement region was chosen at 40-60 mm from the nozzle-tip. In this study, measurement region was set to 10× 10 mm. The obtained images were continuously accumulated in the memory of PC and processed using a commercial software in order to analyze the position of each droplet and the droplet size. Two dimensional cross-section tomograms of sprays were also taken with a double-pulsed 532 nm Nd-YAG laser sheet and 12 bit CCD camera. As a result, curve-fittings of Nukiyama-Tanasawa`s droplet size distribution function were carried out. Under the atmospheric pressure, Value of α became small with going downstream. Meanwhile, under the pressurized condition, the value and droplet distribution was almost same. Furthermore, SMD decreased with going downstream in case of ambient pressure of 0.1 MPa. However, under the pressurized condition, the tendency was reverse.
최승환(Seunghwan Choi),최선모(Sunmo Choi),정동수(Dongsoo Jeong),장영준(Youngjune Chang),Yasuo Moriyoshi 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A new gasoline internal combustion engine was designed and built by improving the cranking mechanism. Numerical simulations were also performed to optimize the cranking mechanism to achieve both a high compression ratio operation without knocking and a high thermal efficiency operation. As a result, a special cranking mechanism was considered to make a rapid piston motion near TDC, leading to less heat loss and also a tolerance for knocking limit. To evaluate this new concept, a leaf-shaped gear system was employed in a test engine. As a result, indicated thermal efficiency with the gear system in compression ratio of 12 was improved by 12% compared to a conventional engine with compression ratio of 10. Moreover, the exhaust gas emissions of HC and NOx were much reduced
Park, Cheolwoong,Kim, Changgi,Kim, Kwantae,Lee, Daehoon,Song, Younghoon,Moriyoshi, Yasuo Elsevier 2010 International journal of hydrogen energy Vol.35 No.4
<P><B>Abstract</B></P><P>Modern diesel engines have improved engine fuel economy and significantly reduced nitrogen oxides (NO<I><SUB>x</SUB></I>) and particulate matter (PM) emissions achieved by advances in both combustion and exhaust aftertreatment technologies. Recently, it has been shown that the vehicle emissions can be further improved by several catalytic systems including fuel reformers and aftertreatment systems, such as the Lean NO<I><SUB>x</SUB></I> Trap (LNT). This NO<I><SUB>x</SUB></I> removal system, called LNT, absorbs NO<I><SUB>x</SUB></I> under lean exhaust gas conditions and releases NO<I><SUB>x</SUB></I> under rich conditions. This technology can provide high NO<I><SUB>x</SUB></I> conversion efficiency, but the right amount of reducing agent should be supplied into the catalytic converter under appropriate conditions.</P><P>In this work, plasma reformer was used to supply a hydrogen-enriched gas as a NO<I><SUB>x</SUB></I> reductant. The plasma reforming is one of the most promising on-board reforming technologies, which allows reformates containing H<SUB>2</SUB> and CO to feed for LNT catalyst efficiently. Partial oxidation is induced by plasma in the fuel reformer and diesel fuel is converted into a hydrogen-enriched gas.</P><P>The supplying strategy was focused on the maximization of NO<I><SUB>x</SUB></I> reduction efficiency varying both the total amount of hydrogen-enriched reformate and the ratio of oxygen molecules to in the reformer air-fuel mixture prior to processing at a fixed engine operating condition. The effect of exhaust gas temperature was also studied. The NO<I><SUB>x</SUB></I> reduction efficiency is closely connected to the amount of supplied fuel to the plasma reformer and the ratio of fuel/air feed rate. The LNT can reduce NO<I><SUB>x</SUB></I> efficiently with only a 2.6% fuel penalty.</P>
Application of Large Eddy Simulation to Diesel Spray
Tsukasa Hori,Jiro Senda,Tanaka Hiroshi,Kyosuke Irie,Kazuya Machida,Yasuo Moriyoshi,Hajime Fujimoto 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
The validation of an evaporative spray simulation with LES has been conducted using Rayleigh scattering method. Rayleigh scattering method is able to measure the instantaneous equivalence ratio on the spray cross section, assuming adiabatic mixture between ambient gas and fuel to estimate the mixture temperature. It is used to validate an evaporative spray simulation with LES. The results showed that the LES simulation was possible to reproduce the evaporative spray development in the quasi-steady condition, using the finer computational grid. In order to improve the computational accuracy, the radial development of the gas velocity from the spray upstream should be reproduced by the improvement of the computational scheme and the spray modeling.