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Journal Article

A Numerical Study on Detailed Soot Formation Processes in Diesel Combustion

This study simulates soot formation processes in diesel combustion using a large eddy simulation (LES) model, based on a one-equation subgrid turbulent kinetic energy model. This approach was implemented in the KIVA4 code, and used to model diesel spray combustion within a constant volume chamber. The combustion model uses a direct integration approach with a fast explicit ordinary differential equation (ODE) solver, and is additionally parallelized using OpenMP. The soot mass production within each computation cell was determined using a phenomenological soot formation model developed by Waseda University. This model was combined with the LES code mentioned above, and included the following important steps: particle inception during which acenaphthylene (A2R5) grows irreversibly to form soot; surface growth with driven by reactions with C2H2; surface oxidation by OH radical and O2 attack; and particle coagulation.
Technical Paper

A Study About In-Cylinder Flow and Combustion in a 4-Valve S.I. Engine

Lean-burn technology is now being reviewed again in view of demands for higher efficiency and cleanness in internal combustion engines. The improvement of combustion using in-cylinder gas flow control is the fundamental technology for establishing lean-burn technology, but the great increase in main combustion velocity due to intensifying of turbulence causes a deterioration in performance such as increase in heat loss and N0x. Thus, it is desirable to improve combustion stability while suppressing the increase in main burn velocity as much as possible (1). It is expected that the fluid characteristics of the in-cylinder tumbling motion that the generated vortices during intake stroke breake down in end-half of compression stroke will satisfy the above requisition. This study is concerned with the effects of enhancing of tumble intensity on combustion in 4-valve S. I. engines.
Technical Paper

A Study of Exhaust and Noise Emissions Reduction on a Single Spray Direct Injection

Exhaust and noise emissions were successfully reduced using a Single Spray Direct Injection Diesel Engine (SSDI) on a two-liter naturally-aspirated four-cylinder engine. The compression ratio, the swirl ratio and the pumping rate were optimized to obtain good fuel economy, high power output and low exhaust emissions. Furthermore, through a modification of the fuel injection equipment, hydrocarbon (HC) emissions were reduced. Upon a test vehicle evaluation of this engine, more than 11% fuel savings relative to Mazda two-liter Indirect Injection Diesel Engines (IDI) were obtained. As for engine noise, structural modifications of the engine were carried out to obtain noise emission levels equivalent to IDI.
Technical Paper

A Study of Jump and Bounce in a Valve Train

Valve train motion was investigated with computer simulation technique. The application of a 5-mass model was found to accurately predict the valve train behavior. It was identified that valve train stiffness and close-side characteristics of valve lift curve have significant effects on bounce occurrence. A valve train with high stiffness tends to develop bounce after jump, while on one with low stiffness, bounce starts in the absence of jump. These findings allowed to develop a new cam form with use of harmonic curves for elevating the revolution limit of the valve train.
Technical Paper

A Study of a Direct-Injection Stratified-Charge Rotary Engine for Motor Vehicle Application

A study of a direct-injection stratified-charge system (DISC), as applied to a rotary engine (RE) for motor vehicle usage, was undertaken. The goals of this study were improved fuel consumption and reduced exhaust emissions. These goals were thought feasible due to the high thermal efficiency associated with the DISC-RE. This was the first application of this technology to a motor vehicle engine. Stable ignition and ideal stratification systems were developed by means of numerical calculations, air-fuel mixture measurements, and actual engine tests. The use of DISC resulted in significantly improved fuel consumption and reduced exhaust emissions. The use of an exhaust gas recirculating system was studied and found to be beneficial in NOx reduction.
Technical Paper

A Study on Improvement of Indicated Thermal Efficiency of ICE Using High Compression Ratio and Reduction of Cooling Loss

Improvement of indicated thermal efficiency of internal combustion engines is required, and increasing the compression ratio is an effective solution. In this study, using a CAE analysis coupling a 0-dimensional combustion analysis and a 1-dimensional heat conduction analysis, the influence of compression ratio on indicated thermal efficiency and combustion was investigated. As a result, it was found that there was an optimal compression ratio that gave the best indicated thermal efficiency, because the increase of cooling loss caused by high compression was bigger than the increase of theoretical indicated thermal efficiency in some cases. Next, the influence of cooling loss reduction on the optimal compression ratio was investigated. It was found that indicated thermal efficiency improved by reducing cooling loss, because the compression ratio which made the best indicated thermal efficiency was shifted to higher compression ratio.
Technical Paper

An Experimental Investigation on Air-Fuel Mixture Formation Inside a Low-Pressure Direct Injection Stratified Charge Rotary Engine

Stratified charge engines have been getting attention for the drastic improvement in thermal efficiency at low-load region. There have been researchers on the two types of engines-the high pressure direct injection stratified charge type in which fuel is supplied directly at high pressure into its combustion chamber right before ignition timings, and the low pressure direct injection stratified charge type in which fuel is injected directly into its cylinder while the cylinder pressure is comparatively low[ 1- 3]. Rotary engines have higher freedom than reciprocating engines in terms of equipping direct fuel injection devices, since their combustion chambers rotate along the rotor housing. The fuel supply units, therefore, need not be exposed to high temperature combustion gas.
Technical Paper

Analysis in cyclic combustion Variation in a Lean Operating S.I. Engine

The causes of the cyclic combustion variation in a lean operating SI engine have been identified using multivariate analysis on the pressure-time data. Principal component analysis on the combustion characteristics obtained from the pressure-time data was conducted in order to select an index of an optimal released heat pattern for analyzing the causes of the cyclic combustion variation. Using this index and the released heat quantity, the IMEP variation was subjected to multiple regression analysis to identify the causes of the cyclic combustion variation. Optimizing the fuel injection timing and swirl ratio made it possible to enrich the mixture near the spark plug. With the lean limit thus extended, a SI engine was operated in a lean range, and the resultant pressure-time data were analyzed. It was found that the main cause of the IMEP variation in the lean operating SI engine was the released heat quantity variation.
Technical Paper

Combustion Characteristics in Hydrogen Fueled Rotary Engine

A hydrogen-fueled rotary engine was investigated with respect to the effects of the fuel supply method, spark plug rating and spark plug cavity volume on abnormal combustion. It was found that abnormal combustion was caused by pre-ignition from the spark plugs and gas leakage through the plug hole cavity. The hydrogen-fueled rotary engine could function through a wide operating range at a theoretical air-to-fuel ratio by optimising the above factors. Consequently, the hydrogen-fueled rotary engine achieved output power of up to 63%-75% of the gasoline specification, while the hydrogen-fueled reciprocating engine only reached 50%.
Journal Article

Combustion Technology Development for a High Compression Ratio SI Engine

Internal combustion engines still play a vital role in realizing the low carbon society. For spark ignition engines, further improvement in thermal efficiency can be achieved by increasing both compression and specific heat ratios. In the current work, the authors developed practical technologies to prevent output power loss due to knocking at full load, which is a critical issue for increasing compression ratio. These new technologies allowed to increase the compression ratio significantly and provide an equivalent torque level as a conventional engine. As a result, thermal efficiency has been improved at partial load.
Technical Paper

Development of Lean Burn Catalyst

A new type of three way catalyst for lean engine was developed in order to reduce hydrocarbon (HC), carbon-monoxide (CO) and nitrogen-oxides (NOx) in lean exhaust gas. This catalyst has a base support material of MFI zeolite loaded with active metals including platinum (Pt), iridium (Ir) and rhodium (Rh). It showed good catalytic activity and thermal durability on a lean engine. This catalyst made it possible to enlarge the lean operating region of the lean burn engine. It showed the NOx reduction of 51% in Japanese 10-15 mode emission test and the emissions were found low enough to satisfy the new Japanese emission standards. Consequently, fuel economy of the lean vehicle with this catalyst has been improved about 16% in comparison with a comparable current stoichiometric combustion vehicle. This catalyst has been mass-produced for Mazda 323 lean burn vehicle (Z-Lean) for the Japanese domestic market.
Technical Paper

Development of Low Particulate Engine with Ceramic Swirl Chamber

An all-ceramic swirl chamber has been developed which meets the 1987 U.S. particulate emission standard for LDV. The all ceramic construction raises combustion temperature to reduce particulate emission to the necessary level. But particulate reduction led to two-fold increase in NOx. This problem was coped with by applying EGR and fuel injection timing control. As a result NOx has been cut to the same level as with a base engine and particulate has been further reduced.
Technical Paper

Development of Sliding Surface Material for Combustion Chamber of High-Output Rotary Engine

The present trend of internal combustion engines toward higher-speed and higher-output capacity is pressing the need for improved lubrication of sliding parts in the combustion chamber to secure reliability. To meet this need, investigation into frictional phenomena was made with a rotary engine, which led to the development of a method of coating the inner surface of the rotor housing with fluorocarbon resin superior in self-lubrication and friction resistance. Rotary engines given this surface finishing showed no trace of irregular wear of the sliding surfaces even when subjected, prior to completion of run-in firing (in green condition), to high-speed and high-load tests, indicating this method's noteworthy benefit of improving comformability. This method offers an excellent surface finish for sliding parts of internal combustion engines (rotary and reciprocating) which will gain increasingly higher output in the future.
Technical Paper

Development of V6 Miller Cycle Gasoline Engine

A gasoline engine with an entirely new combustion cycle deriving from Miller Cycle is developed. By delaying closing timing of intake valve and with new Lysholm Compressor which provides higher boost pressure, engine knocking is avoided while high compression ratio is maintained and approximately 1.5 times larger toque than that of a naturally aspirated(NA) engine of the same displacement is realized. This V6 Miller Cycle gasoline engine can be the alternative to a larger displacement NA engine because of its equivalent torque performance and its lower fuel consumption by the effect of smaller displacement.
Technical Paper

Development of cabin air filter with aldehyde capture function

Aldehydes are the cause of sick house syndrome or chemical sensitivity and have harmful influences for human beings. In the cabin of vehicle, aldehydes which are included in the volatilization gas from the interior materials, DE emission gas in intake air, cigarette smoke and so on spoil the comfortableness. Active carbon, which has been used as an adsorbent, shows an excellent removal efficiency for most of the gas components by physical adsorption. But for aldehydes, it has difficulty because aldehydes are hard to be adsorbed physically. We have developed new aldehydes adsorbent undergoing addition reaction with gaseous aldehydes on its surface. Aldehydes capture material (ACM) make use of the chemical reaction using a resorcin as a reagent and an H-type zeolite as a water-containing support, and active hydrogen is used as a catalyst to promote the reaction. In addition, we have applied ACM to cabin air filter (CAF) of vehicle.
Technical Paper

Development of the Stratified Charge and Stable Combustion Method in DI Gasoline Engines

The new combustion method in DISC engine has been developed. It has a double structure combustion chamber characterized as ‘Caldera’. The chamber is constructed by a center cavity for the purpose of forming a stable mixture around a spark plug electrode, and by an outer cavity which has a role of a main chamber. This method makes possible a perfect un-throttling operation, and a fuel consumption equal to a diesel engine is achieved. With regard to an out-put of DISC engine, a stoichmetric combustion and a high torque are achieved by controling a fuel injection timing with an electro-magnetic injection system device. With regard to emission regulations, a heavy EGR include residual gas decreases greatly NOx and HC emissions simultaneously, and which suggests a possibility to achieve LEV/ULEV regulations.
Technical Paper

Diagnosis and Objective Evaluation of Gear Rattle

The objectives of this work were to establish a method to diagnose the source of gear rattle and to evaluate the rattle objectively. The methods are described in detail, applied to two passenger cars as an example. Investigations were conducted into transmission rattle under transient conditions. By analysing the transmission casing vibration with respect to the engine flywheel angle, and presenting the data in the form of contour maps, it was shown that the two vehicles had different characteristics of gear impacts. Further measurements of the angular motion of each gear revealed the impact conditions at the input mesh in the transmission largely controlled the character of the rattle and were fundamentally different between the two vehicles. A rattle index was developed, based on the casing vibration under transient driving conditions.
Journal Article

Diesel Combustion Noise Reduction by Controlling Piston Vibration

It has been required recently that diesel engines for passenger cars meet various requirements, such as low noise, low fuel consumption, low emissions and high power. The key to improve the noise is to reduce a combustion noise known as “Diesel knock noise”. Conventional approaches to reduce the diesel knock are decreasing combustion excitation force due to pilot/pre fuel injection, adding ribs to engine blocks or improving noise transfer characteristics by using insulation covers. However, these approaches have negative effects, such as deterioration in fuel economy and increase in cost/weight. Therefore, modification of engine structures is required to reduce it. We analyzed noise transfer paths from a piston, a connecting rod, a crank shaft to an engine block and vibration behavior during engine operation experimentally, and identified that piston resonance was a noise source.
Journal Article

Effect of Spray/Wall Interaction on Diesel Combustion and Soot Formation in Two-Dimensional Piston Cavity

The effects of spray/wall interaction on diesel combustion and soot formation in a two-dimensional piston cavity were studied with a high speed color video camera in a constant volume combustion vessel. The two-dimensional piston cavity was applied to generate the impinging spray flame. In the cavity, the flat surface which plays a role as the cylinder head has a 13.5 degree angle with the injector axis and the impinging point was located 30 mm away from the nozzle tip. Three injection pressures of 100, 150, and 200 MPa and a single hole diesel injector (hole diameter: 0.133mm) were selected. The flame structure and combustion process were examined by using the color luminosity images. Two-color pyrometry was used to measure the line-of sight soot temperature and concentration by using the R and B channels of the color images. The soot mass generated by impinging spray flame is higher than that of the free spray flame.
Technical Paper

Improving NOx and Fuel Economy for Mixture Injected SI Engine with EGR

A large quantity of recirculated exhaust gas is used to reduce NOx emissions and improve fuel economy at the same time. The effect of exhaust gas recirculation (EGR) was investigated under the stoichiometric and lean operating conditions and compared with the effect of lean operation without EGR. A mixture injected SI engine that has a mechanically driven mixture injection valve installed was prepared. In this engine, it is possible to charge combustible mixture independently from combustion air and recirculated exhaust gas introduced from intake port in order to stratify the mixture. The effect of the EGR ratio on NOx emissions and fuel consumption was measured under the stoichiometric and lean operating conditions. Due to the mixture distribution controlled by the mixture injection, a large quantity of recirculated exhaust gas could be introduced into the combustion chamber under the stoichiometric air/fuel ratio. The limit of EGR ratio was 48 %.