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The volatile organic compounds (VOC) from diesel engines, including formaldehyde and benzene, are concerned and remain as unregulated harmful substances. The substances are positively correlated with THC emissions, but the VOC and aldehyde compounds at light load or idling conditions are more significant than THC. When coolant temperatures are low at light loads, there are notable increases in formaldehyde and acetaldehyde, and with lower coolant temperatures the increase in aldehydes is more significant than the increase in THC. When using ultra high EGR so that the intake oxygen content decreases below 10%, formaldehyde, acetaldehyde, benzene, and 1,3-butadiene increase significantly while smokeless and ultra low Nox combustion is possible.

A simulation framework for vehicle aerodynamics using up to 10 billion fully unstructured cells has been developed on a world-fastest class supercomputer, called the K computer, in Kobe, Japan. The simulation software FrontFlow/red-Aero was fully optimized on the K computer to utilize up to 10,000 processors with tens of thousands of cores. A hybrid parallelization method using MPI among processors and OpenMP among cores inside each processor was adopted. The code was specially tuned for unsteady aerodynamic simulation including large-eddy simulation, and low Mach number approximation was adopted to avoid excessive iterations usually required for the fully incompressible algorithm. The automated mesh refining system was developed to generate unstructured meshes of up to 10 billion cells. In the system, users only generate unstructured meshes in the order of tens of millions of cells directly using commercial preprocessing software.

The objective of this study was to develop a test method for heavy-duty HEVs using a hardware-in-the-loop simulator (HILS) to enhance the type-approval-test method. To achieve our objective, HILS systems for series and parallel HEVs were actually constructed to verify calculation accuracy. Comparison of calculated and measured data (vehicle speed, motor/generator power, rechargeable energy storage system power/voltage/current/state of charge, and fuel economy) revealed them to be in good agreement. Calculation error for fuel economy was less than 2%.

The emissions reduction potential of neat GTL (Gas to Liquids: Fischer-Tropsch synthetic gas-oil derived from natural gas) fuels has been preliminarily evaluated by three different latest-generation diesel engines with different displacements. In addition, differences in combustion phenomena between the GTL fuels and baseline diesel fuel have been observed by means of a single cylinder engine with optical access. From these findings, one of the engines has been modified to improve both exhaust emissions and fuel consumption simultaneously, assuming the use of neat GTL fuels. The conversion efficiency of the NOx (oxides of nitrogen) reduction catalyst has also been improved.

This study makes use of the detailed mechanisms of n-heptane combustion, from gas reactions to soot particle formation and oxidation, and a two-stage model based on the CHEMKIN reactor network is developed and used to investigate the trade-off between soot and NOx emissions. The effects of the equivalence ratio, EGR, ambient pressure and temperature, and initial particle diameter are observed for various residence times. The results show that high rates of NOx formation are unavoidable under conditions where high reduction rates of soot particles are obtained. This suggests that suppression of the amount of soot during the formation stage is essential for simultaneous reductions in engine-out soot and NOx emissions.

Diesel particulate trap systems are one of the effective means for the control of particulate emission from diesel vehicles. Hino has been researching and developing various diesel particulate trap systems for city buses. This paper describes two of the systems. One uses a wall flow filter equipped with an electric heater and a sensing device for particulate loading for the purpose of filter regeneration. Another makes use of a special filter named “Cross Flow Filter” with an epoch-making regeneration method called “Reverse Jet Cleaning”, by which it becomes possible to separate the part for particulate burning from the filter. Both systems roughly have come to satisfy the functions of trap systems for city buses, but their durability and reliability for city buses are not yet sufficient.

The influence of fuel properties on the operational range and the thermal efficiency of premixed diesel combustion was evaluated with an ordinary diesel fuel, a primary reference fuel for cetane numbers, three primary reference fuels for octane numbers, and two normal heptane-toluene blend fuels in a single-cylinder DI diesel engine. The fuel injection timing was set at 25°CA BTDC and the maximum rate of pressure rise was maintained below 1.0 MPa/°CA when lowering the intake oxygen concentration by cooled EGR. With increasing octane numbers, the higher intake oxygen concentration can be used, resulting in higher indicated thermal efficiency due to a higher combustion efficiency. The best thermal efficiency at the optimum intake oxygen concentration with the ordinary diesel fuel is lower than with the primary reference fuels with the similar ignitability but higher volatility.

Water and diesel fuel emulsions containing 13% and 26% water by volume were investigated in a modern diesel engine with relatively early pilot injection, supercharging, and cooled EGR. The heat release from the pilot injection with water emulsions is retarded toward the top dead center due to the poor ignitability, which enables larger pilot and smaller main injection quantities. This characteristic results in improvements in the thermal efficiency due to the larger heat release near the top dead center and the smaller afterburning. With the 26% water emulsion, mild, smokeless, and very low NOx operation is possible at an optimum pilot injection quantity and 15% intake oxygen with EGR at or below 0.9 MPa IMEP, a condition where large smoke emissions are unavoidable with regular unblended diesel fuel. Heat transfer analysis with Woschni's equation did not show the decrease in cooling loss with the water emulsion fuels.

Combustion and exhaust gas emissions of alcohol and vegetable oil blends including a 20% ethanol + 40% 1-butanol + 40% vegetable oil blend and a 50% 1-butanol + 50% vegetable oil blend were examined in a single cylinder, four-stroke cycle, 0.83L direct injection diesel engine, with a supercharger and a common rail fuel injection system. A 50% diesel oil + 50% vegetable oil blend and regular unblended diesel fuel were used as reference fuels. The boost pressure was kept constant at 160 kPa (absolute pressure), and the cooled low pressure loop EGR was realized by mixing with a part of the exhaust gas. Pilot injection is effective to suppress rapid combustion due to the lower ignitability of the alcohol and vegetable oil blends. The effects of reductions in the intake oxygen concentration with cooled EGR and changes in the fuel injection pressure were investigated for the blended fuels.

Port injection of ethanol addition as an ignition inhibitor was implemented to control ignition timing and expand the operating range in DME fueled HCCI combustion. The ethanol reduced the rate of low-temperature oxidation and consequently delayed the onset of the high-temperature reaction with ultra-low NOx over a wide operating range. Along with the ethanol addition, changes in intake temperature, overall equivalence ratio, and engine speed are investigated and shown to be effective in HCCI combustion control and to enable an extension of operation range. A chemical reaction analysis was performed to elucidate details of the ignition inhibition on low-temperature oxidation of DME-HCCI combustion.

Historically the high speed diesel engine for commercial vehicles has been developed along with its combustion system in compliance with political and economical changes. After the 1970's, stricter exhaust emission regulations and fuel economy requirements induced combustion developments and application of turbocharged and inter cooled engines. From the late 1980's, high pressure fuel injection has been investigated and recognized as an essential tool for lowering emissions especially of particulate matter. Although turbulence effects on both in-cylinder air motion and during the combustion process are quite effective, they show different phenomena in conventional and advanced high pressure fuel injection systems. In the 1990's, multiple injection with high pressure has been attempted for further reduction of NOx and particulate matter.

Newly designed laboratory measurement system, which reproduces particle number size distributions of both nuclei and accumulation mode particles in exhaust emissions, was developed. It enables continuous measurement of nano particle emissions in the size range between 5 and 1000 nm. Evaluations of particle number size distributions were conducted for diesel vehicles with a variety of emission aftertreatment devices and for gasoline vehicles with different combustion systems. For diesel vehicles, Diesel Oxidation Catalyst (DOC), urea-Selective Catalytic Reduction (urea-SCR) system and catalyzed Diesel Particulate Filter (DPF) were evaluated. For gasoline vehicles, Lean-burn Direct Injection Spark Ignition (DISI), Stoichiometric DISI and Multi Point Injection (MPI) were evaluated. Japanese latest transient test cycles were used for the evaluation: JE05 mode driving cycle for heavy duty vehicles and JC08 mode driving cycle for light duty vehicles.

In order to clarify future automobile technologies and fuel qualities to improve air quality, second phase of Japan Clean Air Program (JCAPII) had been conducted from 2002 to 2007. Predicting improvement in air quality that might be attained by introducing new emission control technologies and determining fuel qualities required for the technologies is one of the main issues of this program. Unregulated material WG of JCAPII had studied unregulated emissions from gasoline and diesel engines. Eight gaseous hydrocarbons (HC), four Aldehydes and three polycyclic aromatic hydrocarbons (PAHs) were evaluated as unregulated emissions. Specifically, emissions of the following components were measured: 1,3-Butadiene, Benzene, Toluene, Xylene, Ethylbenzene, 1,3,5-Trimethyl-benzene, n-Hexane, Styrene as gaseous HCs, Formaldehyde, Acetaldehyde, Acrolein, Benzaldehyde as Aldehydes, and Benzo(a)pyrene, Benzo(b)fluoranthene, Benzo(k)fluoranthene as PAHs.

Since in-cylinder flame temperature has a direct effect on an engine's NOx characteristics, these phenomena have been studied in detail in a DI diesel engine using a newly developed method allowing the in-cylinder temperature distribution to be measured by the two color method. The flame light introduced from the visualized combustion chamber of the engine is divided into two colors by filters. The images of combustion phenomena using the two wavelengths are recorded with a framing streak camera which includes a CCD camera. The flame temperature is immediately calculated by a computer using two color images from the CCD camera. A parameter study was then carried out to determine the influence of intake valve number of the engine, and fuel injection rate (pilot injection) on the in-cylinder temperature distribution.

The objective of this study is to improve fuel economy and reduce carbon dioxide emissions in diesel-electric hybrid automotive powertrains by developing an exhaust gas turbine generator system which utilizes exhaust gas energy from the turbocharger waste gate. The design of the exhaust gas turbine generator was based on a conventional turbocharger for a direct-injection diesel engine. Data from steady-state bench tests using air indicates about 50% of the turbine input energy can be converted to electric energy. Turbine generator output averaged 3 kW, while a maximum of about 6 kW was observed. Based on this data, we estimate that energy consumption in a vehicle could be reduced between 5% and 10%. Engine tests were conducted under both steady-state and transient conditions. These tests revealed that optimal performance occurred under high-speed, high-load conditions, typical of highway or uphill driving, and that performance at low-speed, low-loads was relatively poor.

To reduce NOx and Particulate Matter (PM) emissions from a heavy-duty diesel engine, the effects of urea selective catalytic reduction (SCR) systems were studied. Proto type urea SCR system was composed of NO oxidation catalyst, SCR catalyst and ammonia (NH3) reduction catalyst. The NOx reduction performance of urea SCR system was improved by a new zeolite type catalyst and mixer for urea distribution at the steady state operating conditions. NOx and PM reduction performance of the urea SCR system with DPF was evaluated over JE05 mode of Japan. The NOx reduction efficiency of the urea SCR catalyst system was 72% at JE05 mode. The PM reduction efficiency of the urea SCR catalyst system with DPF was 93% at JE05 mode. Several kinds of un-regulated matters were detected including NH3 and N2O leak from the exhaust gas. It is necessary to have further study for detailed measurements for un-regulated emissions from urea solution.

A new concept for diesel combustion has been investigated by means of engine experiments and combustion observations in order to realize a simultaneous reduction of NOx and particulate emissions. The concept is based on pre-mixed compression ignition combustion combined with multiple injection. In this method, some part of fuel is injected at an early stage of the process to form a homogeneous lean pre-mixture, then the remaining fuel is injected at around the TDC in the same manner as a conventional diesel injection. The emissions, ROHR (rate of heat release), and combustion pictures of conventional combustion, pilot injection combustion, and this new combustion concept were compared and analyzed. Engine tests were carried out using a single cylinder research engine equipped with a common rail injection system.

This paper describes the combustion optimizations of heavy-duty diesel engines for the anticipated future emissions regulations by means of an electronically controlled common rail injection system. Tests were conducted on a turbocharged and aftercooled (TCA) prototype heavy-duty diesel engine. To improve both NOx-fuel consumption and NOx-PM trade-offs, fuel injection characteristics including injection timing, injection pressure, pilot injection quantity, and injection interval on emissions and engine performances were explored. Then intake swirl ratio and combustion chamber geometry were modified to optimize air-fuel mixing and to emphasize the pilot injection effects. Finally, for further NOx reductions, the potentials of the combined use of EGR and pilot injection were experimentally examined. The results showed that the NOx-fuel consumption trade-off is improved by an optimum swirl ratio and combustion chamber geometry as well as by a new pilot concept.

The requirements for emission control, lower fuel consumption and higher engine output have changed the engine valve train system to 4-valve/cylinder and higher cam lift designs, and these changes make the cam/tappet lubrication conditions more severe than before. Under such a working condition, there is a high possibility that cam/tappet surface damages such as scuffing, pitting and wear may occur. Among the damages, the wear of cam/tappet is the most difficult to predict since the wear mechanism still remains unclear. To understand the lubrication condition and therefore, the wear mechanism at the cam/tappet contact, friction was measured with a newly developed apparatus. Measurement results showed that the lubrication condition between cam and tappet is predominantly in the mixed and boundary lubrication conditions.

In Biodiesel Fuel Research Working Group(WG) of Japan Auto-Oil Program(JATOP), some impacts of high biodiesel blends have been investigated from the viewpoints of fuel properties, stability, emissions, exhaust aftertreatment systems, cold driveability, mixing in engine oils, durability/reliability and so on. In the impact on exhaust emissions, the impact of high biodiesel blends into diesel fuel on diesel emissions was evaluated. The wide variety of biodiesel blendstock, which included not only some kinds of fatty acid methyl esters(FAME) but also hydrofined biodiesel(HBD) and Fischer-Tropsch diesel fuel(FTD), were selected to evaluate. The main blend level evaluated was 5, 10 and 20% and the higher blend level over 20% was also evaluated in some tests. The main advanced technologies for exhaust aftertreatment systems were diesel particulate filter(DPF), Urea selective catalytic reduction (Urea-SCR) and the combination of DPF and NOx storage reduction catalyst(NSR).