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This study focused on the technology integration to aim beyond 60% indicated thermal efficiency (ITE) with a single-cylinder heavy-duty diesel engine as an alternative to achieve 55% brake thermal efficiency (BTE) with multiple-cylinder engines. Technology assessment was initially carried out by means of a simple chart of showing ITE and exhaust heat loss as functions of cooling loss and heat conversion efficiency into indicated work. The proposed compression ratio (28:1), excess air ratio and new ideal thermodynamic cycle were then determined by a simple cycle calculation. Except for peak cylinder pressure constraint for each engine, the technical barriers for further ITE improvement are mainly laid in cooling loss reduction, fuel-air mixture formation improvement, and heat release rate optimization under very high temperature and density conditions with very high compression ratio (smaller cavity volume).

In the previous study design of two-component normal paraffin fuel was attempted considering the components and blending ratio. Only the thermodynamic analysis of combustion and analysis of emission characteristics were performed to evaluate the design performance. In this study mixture formation behavior and combustion phenomena of pure and mixed n-paraffin fuels were investigated by direct visualization in an AVL engine with bottom view piston. The experiments included laser-illuminated high-speed photography of the fuel injection phase and combustion phase to investigate physical differences. The results obtained for the proposed fuels are compared with the results of conventional diesel fuel. It was found that the two component normal paraffin fuels with similar thermo physical properties have very similar spray development pattern but evaporation rates are different.

As the petroleum depletion, some of this demand will probably have to be met by increasing the production of diesel fuels from heavy oil or unconventional oil in the near future. Such fuels may inevitably have a lower cetane number (CN) with a higher concentration of aromatic components. The objective of the present research is to identify the effects of a typical biodiesel fuel as a CN improver for a light-duty diesel engine for passenger cars. Our previous study indicates that methyl oleate (MO), which is an oxygenated fuel representative of major constituents of many biodiesel types, can reduce soot and NOx emissions simultaneously by optimizing performance under exhaust gas recirculation (EGR) when used as a diesel fuel additive. In addition, it was found that MO tends to reduce the ignition delay. We employed a 2.2 L passenger car DI diesel engine complying with the Euro 4 emissions regulation.

More stringent emission regulations call for high-efficiency engines in the heavy-duty vehicle sector. Towards this goal, reduced heat losses, as well as increased work output, are needed. In this study, a multiple injector concept to control the combustion as well as reduce the hot boundary zones is proposed. Earlier studies have proven that multiple injectors experience lower heat losses and higher efficiency. However, a comprehensive investigation of the causes for experimental heat loss was not performed in depth. Experiments in a heavy-duty CI engine equipped with three injectors were thus performed. Engine configurations of single, dual and triple injectors were compared for a single-injection case as well as a multi-injection (Sabathe-cycle) case. Heat losses, efficiency and the emission levels were quantified and investigated. Optical experiments were performed to investigate the temperature field as well as flame behavior.

Over the last few years much interest has been shown in Dimethyl Ether (DME) as a new fuel for diesel cycle engines. DME combines the advantages of a high cetane number with soot-free combustion, making it eminently suitable for compression engines. According, however, to past engine test results, the engine output of a DME engine lacking compatibility as a DME injection system, is low in comparison with a diesel engine. Required is development of a DME injection system conforming to DME properties. The purpose of this work is to investigate the feasibility of DME application for a conventional jerk-type in-line injection system that has the actual result of use of a comparatively low lubricity fuel such as methanol.

The objective of the present research is to investigate the effects on diesel engine combustion and NOx and PM emission characteristics in case of blending the ordinary diesel fuel with biodiesel in passenger car diesel engines. Firstly, we conducted experiments to identify the combustion and emissions characteristics in a modern diesel engine complying with the EURO 4 emission standard. Then, we developed a numerical simulation model to explain and generalize biodiesel combustion phenomena in detail and generalize emission characteristics. The experimental and simulation results are useful to reduce biodiesel emissions by controlling engine operating and design parameters in the diesel engine. Engine tests were conducted and a mathematical model created to investigate the effects of 40% and 100% methyl oleate modeled fuel representing Jatropha-derived biodiesel on diesel combustion and emission characteristics, over a wide range of passenger car DI diesel engine operating conditions.

Fuel temperature in the injector of small direct injection gasoline engine is high. On some conditions it is higher than saturated temperature. Over saturated temperature spray characteristics greatly change. In order to predict in-cylinder phenomena accurately, it is important to understand spray behavior and mixture process above saturated temperature. Therefore spray shape, mixture formation process and Sauter mean radius were (SMR) measured in a constant volume chamber. And based on the measurement result initial spray boundary conditions were arranged so that spray characteristics over saturated temperature could be represented by using CFD code KIVA-3[1]. Moreover KIVA-3 code was combined with detailed chemical kinetics code Chemkin II to predict combustion products. [2] Calculated combustion process was validated with visualization of chemiluminescence. As a result, spray shape and penetration length have good agreement with measured ones for each fuel temperature.

A study has been made of an automotive direct injection diesel engine designed to reduce exhaust emissions, particularly NOx and particulates, without performance deterioration. Special emphasis has been placed on air-fuel mixing conditions controlled by the fuel injection rate, the intake swirl ratio, and the intake boost pressure. By means of increasing the injection rate, ignition delay can be shortened enough to improve particulate emissions at retarded injection timings. Enhancing the intake swirl velocity contributes to the reduction of soot emission in spite of the deterioration of NOx emission. Supercharging can favorably enhance diffusion combustion resulting in improved fuel economy for retarded injection timings and reduced emissions. As a result, a good compromise can be achieved between fuel economy and exhaust emissions by increasing the injection rate along with retarding the injection timing. Supercharging was found to be more favorable than swirl enhancement.

The purpose of this study is to improve low-temperature flow-properties of biodiesel fuels (BDF) by blending with ethanol and to analyze the combustion characteristics in a diesel engine fueled with BDF/ethanol blended fuel. Because ethanol has a lower solidifying temperature, higher oxygen content, lower cetane number, and higher volatility than BDF, ethanol blending would have a large effect on cold flow performance, mixture formation, ignition, combustion, and exhaust emissions. The engine experiments in the study were performed with a diesel engine and blends of BDF and ethanol at different blending ratios. The cold flow performance of the blended fuels was evaluated by determining the fuel cloud point. The experimental results show that the ethanol blending lowers the cloud point of the blended fuel and significantly reduces smoke emissions from the engine without deteriorating other emissions or thermal efficiency.

A development project for a hydrogen internal combustion engine (ICE) system for trucks supporting Japanese freightage has been promoted as a candidate for use in future vehicles that meet ultra-low emission and anti-global warming targets. This project aims to develop a hydrogen ICE truck that can handle the same freight as existing trucks. The core development technologies for this project are a direct-injection (DI) hydrogen ICE system and a liquid hydrogen tank system which has a liquid hydrogen pump built-in. In the first phase of the project, efforts were made to develop the DI hydrogen ICE system. Over the past three years, the following results have been obtained: A high-pressure hydrogen gas direct injector developed for this project was applied to a single-cylinder hydrogen ICE and the indicated mean effective pressure (IMEP) corresponding to a power output of 147 kW in a 6-cylinder hydrogen ICE was confirmed.

The cordierite filter has been widely studied because of it's inherent, high capacities in the collection efficiency and heat-resistance. During the regeneration process of a cordierite filter, failure of ignition or incomplete burning propagation occurs, and additionally melts or cracks develop sometimes. In this study, the problems stated above are considered from a new standpoint, and a regeneration method that does not strictly depend on accumulated soot quantity is discussed. A filter made of SiC (Silicon carbide) possesses the requisite electric resistance and it's possible to heat it uniformly by using electricity. Accumulated soot can be uniformly incinerated not by burning propagation but by simultaneous ignition and burning of all accumulated soot. Silicon carbide has a higher resistance to heat than cordierite. Therefore, a self-heating filter made of SiC makes it possible to regenerate the filter in a wider range of accumulated soot.

For further increase in thermal efficiency of heavy-duty diesel engines, flexible regulation of the heat release rate (HRR) profile combined with higher compression ratio could have more rooms to improve indicated thermal efficiency by overcoming various drawbacks relevant to higher compression ratio. A new ideal HRR profile, which starts as a kind of delta shape to fulfil the isobaric cycle from top-dead-center (TDC) and is followed by the significant increase in HRR to reach the maximum cylinder pressure in the retarded timing, was proposed. We call it as ‘High-heels’ HRR profile from its two-step-increase delta shape. To confirm the potential of the ideal HRR profile by utilizing a single- cylinder heavy-duty diesel engine, a variable fuel injection rate equipment, novel combustion chamber designs, and an offset orifices nozzle were investigated as the technologies for modifying HRR profile.

Hydrogen engines are required to provide high thermal efficiency and low nitrogen oxide (NOX) emissions. There are many possible combinations of injection timing, ignition timing, lambda and EGR rate that can be used in a direct-injection system for achieving such performance. In this study, NOX emissions of natural aspirated 4 cylinders engine with management strategies involving the injection timing, ignition timing, lambda and the EGR rate were evaluated under a Japanese JE05 emissions test cycle. Finally, the paper projects the potential of direct injection hydrogen engine for obtaining high output power and attaining low NOX emissions of 0.7 g/kWh under the emission test cycle.

To suppress knock in small gasoline engines, the coolant flow of a single-cylinder engine was improved by using two methods: a multi-dimensional knock prediction method combining a Flamelet model with a simple chemical kinetics model, and a method for predicting combustion chamber wall temperature based on a thermal fluid calculation that coupled the engine coolant and the engine structure (engine head, cylinder block, and head gasket). Through these calculations as well as the measurement of wall temperatures and the analysis of combustion by experiments, the effects of wall temperature distribution and consequent unburnt gas temperature distribution on knock onset timing and location were examined. Furthermore, a study was made to develop a method for cooling the head side, which was more effective to suppress knock: the head gasket shape was modified to change the coolant flow and thereby improve the distribution of wall temperatures on the head side.

To reduce carbon dioxide (CO2) emissions from heavy-duty diesel engines down to zero until 2050, alternative powertrain strategies have been proposed in lieu of the improvements in internal combustion engines (ICEs). However, total amount of renewable electricity could be limited for the constructing infrastructure, the production of new battery and/or fuel cell vehicles and the operation of them compared with the growing demand of transportation in the future. Therefore, drastic improvement in transport efficiency with suppressing the increase of total CO2 emissions is essential. From these points of view, extremely high efficiency ICEs, combined or at least compatible with carbon neutral or renewable fuels having the capability of drop-in into the conventional fuels, should be attracted attention. Nevertheless, there have been few studies on the effects of fuel properties for further improving fuel consumption of diesel ICEs.

Study of DME diesel engines was conducted to improve fuel consumption and emissions of its. Additionally, DME trucks were built for the promotion and the road tests of these trucks were executed on EFV21 project. In this paper, results of diesel engine tests and DME truck driving tests are presented. As for DME diesel engines, the performance of a DME turbocharged diesel engine with LPL-EGR was evaluated and the influence of the compression ratio was also explored. As for DME trucks, a 100,000km road test was conducted on a DME light duty truck. After the road test, the engine was disassembled for investigation. Furthermore, two DME medium duty trucks have been developed and are now the undergoing practical road testing in each area of two transportation companies in Japan.

An experimental and numerical study has been conducted on the emission and reduction of HCHO (formaldehyde) and other pollutants formed in the cylinder of a direct-injection diesel engine fueled by methanol. Engine tests were performed under a variety of intake conditions including throttling, heating, and EGR (exhaust gas recirculation) for the purpose of improving these emissions by changing gas compositions and combustion temperatures in the cylinder. Moreover, a detailed kinetics model was developed and applied to methanol combustion to investigate HCHO formation and the reduction mechanism influenced by associated elementary reactions and in-cylinder mixing.

The engine in the research is a single cylinder DI diesel using the emission reduction techniques such as high boost, high injection pressure and broad range and high quantity of exhaust gas recirculation (EGR). The study especially focuses on the reduction of particulate matter (PM) under the engine operating conditions. In the experiment the authors measured engine performance, exhaust gases and mass of PM by low sulfur fuel such as 3 ppm and low sulfur lubricant oil such as 0.26%. Then the PM components were divided into soluble organic fraction (SOF) and insoluble organic fraction (ISOF) and they were measured at each engine condition. The mass of SOF was measured from the fuel fraction and lubricant oil fraction by gas chromatography. Also each mass of soot fraction and sulfate fraction was measured as components of ISOF. The experiment was conducted at BMEP = 2.0 MPa as full load condition of the engine and changing EGR rate from 0% to 40 %.

The increase in number of automobiles due to its convenience brought serious increases in environmental load. The rate of attainment of environmental standards for nitrogen dioxide (NO2) and suspended particulate matter (SPM) in urban areas is still low in Japan. Diesel vehicles emit the vast majority of air pollutants from exhaust. Therefore, developing emission measures, particularly for diesel vehicles, is an urgent task for addressing air pollution. Furthermore, at the Third Conference of the Parties to the UN Framework Convention on Climate Change (COP 3) held in Kyoto in December 1997, Japan pledged to reduce greenhouse gas emissions to 6 percent below 1990 levels for the first commitment period of 2008 to 2012. To address vehicle emissions, Japan is gradually introducing increasingly strict NOx and particulate matter regulations.

As a technology required for future commercial heavy-duty diesel engines, this study reexamines the potential of the multiple injection strategy for improving the thermal efficiency while maintaining low engine-out exhaust emissions with a high EGR rate of more than 50% and high boost pressure of 276.3 kPa abs under medium load conditions. The experiments were conducted with a single cylinder research engine. The engine was operated at BMEP of 0.8 MPa at a medium speed. Using multiple injections, the temporal and spatial in-cylinder temperature distribution was changed to investigate the effect on fuel consumption and exhaust emissions. The results showed that the multiple injection strategy combined with higher EGR rate could improve fuel consumption by about 3% due to the reduction of heat loss from the wall.