Yasuhiro Daisho

Combustion and exhaust gas emission characteristics of a diesel engine dual-fueled with natural gas

Abstract This paper deals with a diesel engine dual-fueled with natural gas. This system can achieve a high thermal efficiency at higher loads by utilizing the premixed lean natural gas mixture ignited by pilot-injected diesel fuel. At low loads, however, high THC emission and low thermal efficiency were observed. To resolve these problems, effects of EGR and intake heating with an exhaust to intake heat exchanger on engine performance and exhaust gas emissions were investigated, especially at low loads. In addition, 3-CFD simulations were conducted to analyze the combustion process in the combustion chamber, using the KIVA-3 code. The result indicates that thermal efficiency and THC emission at lower loads can be improved by intake air heating combined with EGR.

Effects of diesel fuel characteristics on spray and combustion in a diesel engine

Abstract Fuel properties play a dominant role in the spray, mixture formation and combustion process, and are a key to emission control and efficiency optimization. This paper deals with the influence of the fuel properties on the spray and combustion characteristics in a high-pressure and temperature chamber. Light diesel fuel spray and combustion images were taken by using a high-speed video camera and analyzed by their penetration and evaporation characteristics in comparison with current diesel fuel. Then, a single-cylinder DI engine was used to investigate combustion and exhaust characteristics. The mixture formation of the light diesel fuel is faster than that of the current fuel depending on physical properties like boiling point, density, viscosity and surface tension. Engine test results show that smoke is reduced without an increase in other emissions.

Experimental study on unregulated emission characteristics of turbocharged di diesel engine with common rail fuel injection system

In this study, we selected four unregulated emissions species, formaldehyde, benzene, 1,3-butadiene and benzo[a]pyrene to research the emission characteristics of these unregulated components experimentally. The engine used was a water-cooled, 8-liter, 6-cylinder, 4-stroke-cycle, turbocharged Dl diesel engine with a common rail fuel injection system manufactured for the use of medium-duty trucks, and the fuel used was JIS second-class light gas oil, which is commercially available as diesel fuel. The results of experiments indicate as follows: formaldehyde tends to be emitted under the low load condition, while 1,3-butadiene is emitted at the low engine speed. This is believed to be because 1,3-butadiene decomposes in a short time, and the exhaust gas stays much longer in a cylinder under the low speed condition than under the high engine speed one. Benzene is emitted under the low load condition, as it is easily oxidized in high temperature. Benzo[a]pyrene exists in the gas phase, because its boiling point is about 750K (at 128kPa). Once gaseous benzo[a]pyrene condenses, it is trapped by a filter with soot or sulfate. If it stays in the high temperature area, large part of it is oxidized. Consequently, benzo[a]pyrene is not emitted in great quantity under the high load condition.

Effects of Combustion Chamber Geometry on Diesel Combustion

Influence de la geometrie de la chambre de combustion sur la combustion dans un moteur diesel

Development of a non-contact rapid charging inductive power supply system for electric-driven vehicles

Non-contact rapid charging inductive power supply (IPS) system has been developed and tested as a charger for electric-driven vehicles (EdV). By using the developed system, EdV charging can be carried out safely, easily, and in a short period. Optimizing the track and pick up design of the IPS based on finite-element electromagnetic field analyses achieved significant improvements in efficiency (92%), weight (35kg), thickness (33mm), and air gap length (100mm) during 30kW power transmissions.

Homogeneous charge compression ignition and combustion characteristics of natural gas mixtures: the visualization and analysis of combustion

Abstract The purpose of this study is to elucidate autoignition characteristics of HCCI of natural gas mixtures during the compression process in the engine. A rapid compression and expansion machine was used to reproduce and visualize autoiginition combustion. The test results show that initial temperature and density, and hydrocarbon contents other than methane, are important parameters influencing autoignition timing and the successive combustion. A detailed chemical kinetics model combined with a multi-dimensional CFD code supports these autoignition characteristics.

Numerical analysis of Miller-premixed charge compression ignition combustion on a dynamic φ-T map

Abstract A variable valve timing mechanism has been applied in a high-speed direct injection diesel engine. The effective compression ratio (εeff) is lowered by means of late intake valve closing, while keeping the expansion ratio constant. Premixed charge compression ignition (PCCI) combustion, adopting the Miller cycle, was experimentally realized and numerically analysed. Significant improvements in NO x (nitrogen oxides) and soot emissions were achieved for a wide range of engine speeds and loads frequently used in a transient mode test. The operating range of the Miller-PCCI combustion has been expanded up to an indicated mean effective pressure of 1.3 MPa.

Emissions suppression mechanism of premixed diesel combustion with variable valve timing

Abstract A variable valve timing (VVT) mechanism is applied to achieve premixed diesel combustion at higher load for low emissions and high thermal efficiency in a light-duty diesel engine. By means of late intake valve closing (LIVC), compressed gas temperatures near the top dead centre are lowered, thereby preventing too early ignition and increasing ignition delay to enhance fuel-air mixing. The variability of an effective compression ratio has significant potential for ignition timing control of conventional diesel fuel mixtures. At the same time, the expansion ratio is kept constant to ensure thermal efficiency. Combining the control of LIVC, exhaust gas recirculation (EGR), supercharging systems, and high-pressure fuel injection equipment can simultaneously reduce NO x and smoke. The NO x and smoke suppression mechanism in the premixed diesel combustion is analysed using a three-dimensional computational fluid dynamics (3D-CFD) code combined with detailed chemistry. LIVC can achieve a significant NO x and smoke reduction due to lowering combustion temperatures and avoiding local overrich regions in the mixtures respectively.

Spray characteristics of alternative fuels in constant volume chamber (comparison of the spray characteristics of LPG, DME and n-dodecane)

It has been recognized that alternative fuels such as dimethyl ether (DME) and liquefied petroleum gas (LPG) have less polluting combustion characteristics than diesel fuel. In this study, such alternative fuels were injected into a high pressure and temperature chamber by means of an electronically controlled common rail injection system to reproduce their charge stratification processes in the engine. Their spray images were taken by using a high-speed video camera and copper-vapor laser to analyze their penetration and evaporation characteristics in comparison with normal-dodecane (n-dodecane) which represent the physical and chemical characteristics as a replacement for diesel fuel. The mixture formation of DME and LPG sprays is faster than that of n-dodecane due to their flash boiling characteristics at high pressures and temperatures.

Development and performance evaluation of a non-contact rapid charging inductive power supply system for electric micro-bus

A non-contact rapid charging inductive power supply (IPS) system has been developed and tested as a charger for electric-driven vehicles (EdV). By using this system, EdV charging can be carried out safely, easily, and in a short period. Optimizing the track and pick up design of the IPS based on finite-element electromagnetic field analyses achieved significant improvements in efficiency (92%), weight (35kg), thickness (33mm), and air gap length (100mm) during 30kW power transmission. Testing on public roads of an electric-micro bus equipped with the IPS is also detailed.