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In previous Life Cycle Assessment (LCA) methods, environmental burden items to be analyzed, prior to a life cycle inventory analysis, were assumed as the main factors of environmental problems regardless of the product category. Next, the life cycle inventory analysis, in which the total amount of environmental burden items emitted during the life cycle of a product was calculated, and an environmental impact assessment were performed. The environmental impact assessment was based on the initially assumed environmental burden items. The process, in other words, was a particular solution based on this assumption. A general solution unconstrained by this assumption was necessary. The purpose of this study was to develop a general method of LCA that did not require such initially assumed environmental burden items, and to make it possible to perform a comprehensive environmental impact assessment and strategically reduce environmental burden of a product.

The abnormal combustion resulted by the auto-ignition of lubricating oil is a great challenge to the development of Otto-cycle gas engines. In order to investigate the mechanism of lubricating oil droplet vaporization process, a crucial sub-process of auto-ignition process, a new multi-component vaporization model was constructed for high temperature and pressure, and forced gas flow conditions as encountered in practical gas engines. The vaporization model has been conducted with a multi-diffusion sub-model considering the multi-component diffusivity coefficients in the gas phase. The radiation heat flux caused by ambient gas was taken into account in high temperature conditions, and a real gas equation of state was used for high pressure conditions. A correction for mass vaporization rate was used for forced gas flow conditions. Extensive verifications have been realized, and considerable results have been achieved.

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.

A solution for cylinder wall scuffing is researched. By means of the finite element method, a mathematical model to investigate the temperature field and thermal deformation of the piston is established, which can be used for predicting the cylinder wall scuffing in both the design process of a new diesel engine and the improvement process of the combustion system of an operating diesel engine. The experimental data support the calculated results obtained by using the model. As an application example, the temperature fields and thermal deformations of the piston in the 6E150C diesel engine, which suffers from the cylinder wall scuffing during the period of operation, are analyzed quantitatively by using the mathematical model. After an improved piston with new structure and good cooling system is used in the 6E150C diesel engine, the cylinder wall scuffing no longer occurs.

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.

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.

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.

Working process of diesel engine refers to airflow, turbocharger, fuel injection, combustion, heat transfer and chemical reaction powers etc. Hence, it influences power output, fuel consumption, combustion noise and emissions, moreover directly influences reliability and durability of diesel engine. The working process of 6106 diesel engine is simulated by large universal internal combustion engine working process numerical simulation software GT-Power in this paper, and the effects of compression ratio, fuel supply advance angle and valve timing system on performance of diesel engine are analyzed. When valve-timing system is studied, the influence of intake valve close timing, exhaust valve open timing and valve overlap angle on performance are analyzed. On different operating conditions, the different timing of intake close and exhaust open, valve overlap were computed and analyzed. Finally, at different engine conditions, various optimum results were obtained.

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.

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.

In order to comply with the stringent emission regulations, many researchers have been focusing on diesel-compressed natural gas (CNG) dual fuel operation in compression ignition (CI) engines. The diesel-CNG dual fuel operation mode has the potential to reduce both the soot and NOx emissions; however, the thermal efficiency is generally lower than that of the pure diesel operation, especially under the low and medium load conditions. The current experimental work investigates the potential of using diesel-1-butanol blends as the pilot fuel to improve the engine performance and emissions. Fuel blends of B0 (pure diesel), B10 (90% diesel and 10% 1-butanol by volume) and B20 (80% diesel and 20% 1-butanol) with 70% CNG substitution were compared based on an equivalent input energy at an engine speed of 1200 RPM. The results indicated that the diesel-1-butanol pilot fuel can lead to a more homogeneous mixture due to the longer ignition delay.

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.

Increasingly strict emission regulations and unfavorable economic climate bring severe challenges to the energy conservation of marine low-speed engine. Besides traditional methods, the energy and exergy analysis could acknowledge the losses of fuel from a global perspective to further improve the engine efficiency. Therefore, the energy and exergy analysis is conducted for a marine low-speed engine based on the experimental data. Energy analysis shows the exhaust gas occupies the largest proportion of all fuel energy waste, and it rises with the increment of engine load. The heat transfer consumes the second largest proportion, while it is negatively correlated to engine load. The energy analysis indicates that the most effective way to improve the engine efficiency is to reduce the energy wasted by exhaust gas and heat transfer. However, the latter exergy analysis demonstrates that there are other effective approaches to improve the engine efficiency.

In recent years, improving fuel efficiency and collision safety are important issue. We have worked on a new construction method to develop body structure which is light weight and strong/stiff. We adopt multi type Tailor-Welded Blanks (TWB) which is formed after welding several steel sheets for ATENZA (MAZDA 6), NEW DEMIO (MAZDA 2), and RX-8. This is a technology to consistently improve of such product properties and to reduce costs. Laser welding is a common TWB welding method, but for further equipment cost reductions and productivity improvements, we have developed a higher welding speed and robust plasma welding and introduced this to mass production. We introduce this activity and results in this report.

This paper presents two factors for improving the performance and emissions characteristics in HCCI diesel combustion, one is reducing compression ratio and another is changing the injector position. In a previous study, it was shown that HCCI diesel combustion could be realized by utilizing a hollow-cone spray with normal injection pressure. However there remained two major problems of engine instability and increase in BSFC (decrease in brake thermal efficiency). By reducing the compression ratio from 18.8 to 16.8, the engine stability was much improved to the level of conventional diesel combustion and the increase in BSFC became almost half, which was mainly due to the change of combustion phasing. In addition to this, application of 5 mm inside position of the injector realized almost no penalty of BSFC at higher load condition.

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%.

Acetone-Butanol-Ethanol (ABE) is an intermediate product in the ABE fermentation process for producing bio-butanol. As an additive for diesel, it has been shown to improve spray evaporation, improve fuel atomization, enhance air-fuel mixing, and enhance combustion as a whole. The typical compositions of ABE are in a volumetric ratio of 3:6:1 or 6:3:1. From previous studies done in a constant volume chamber, it was observed that the presence of additional acetone in the blend caused advancement in the combustion phasing, but too much acetone content led to an increase in soot emission during combustion. The objective of this research was to investigate the combustion of these mixtures in a diesel engine. The experiments were conducted in an AVL 5402 single-cylinder diesel engine at different speeds and different loads to study component effects on the various engine conditions. The fuels tested in these experiments were D100, ABE(3:6:1)10, ABE(3:6:1)20, ABE(6:3:1)10, and ABE(6:3:1)20.

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.

Lean-burn combustion is an effective method for increasing the thermal efficiency of gasoline engines fueled with stoichiometric fuel-air mixture, but leads to an unacceptable level of high cyclic variability before reaching ultra-low nitrogen oxide (NOx) emissions emitted from conventional gasoline engines. Multi-point micro-flame ignited (MFI) hybrid combustion was proposed to overcome this problem, and can be can be grouped into double-peak type, ramp type and trapezoid type with very low frequency of appearance. This research investigates the micro-flame ignition stages of double-peak type and ramp type MFI combustion captured by high speed photography. The results show that large flame is formed by the fast propagation of multi-point flame occurring in the central zone of the cylinder in the double-peak type. However, the multiple flame sites occur around the cylinder, and then gradually propagate and form a large flame accelerated by the independent small flame in the ramp type.

Multi-dimensional models coupled with a reduced chemical mechanism were used to investigate the effect of fuel on exergy destruction fraction and sources in a reactivity controlled compression ignition (RCCI) engine. The exergy destruction due to chemical reaction (Deschem) makes the largest contribution to the total exergy destruction. Different from the obvious low temperature heat release (LTHR) behavior in gasoline/diesel RCCI, methanol has a negative effect on the LTHR of diesel, so the exergy destruction accumulation from LTHR to high temperature heat release (HTHR) can be avoided in methanol/diesel RCCI, contributing to the reduction of Deschem. Moreover, the combustion temperature in methanol/diesel RCCI is higher compared to gasoline/diesel RCCI, which is also beneficial to the lower exergy destruction fraction. Therefore, the exergy destruction of methanol/diesel RCCI is lower than that of gasoline/diesel RCCI at the same combustion phasing.