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Application of biodiesel fuel (BDF) to diesel engine is very effective to reduce CO2 emission, because bio-diesel is carbon neutral in principle. However, when biodiesel was applied to conventional diesel engines without modification for biodiesel, NOx emission was increased by the change in fuel characteristics. It is necessary to introduce some strategies into diesel engines fuelled with biodiesel for lower NOx emission than conventional diesel fuel case. The purpose of this study is to reveal that exhaust gas recirculation (EGR) is one of the solutions for the reduction of NOx emission and meeting the future emission regulations when using biodiesel. Neat Rapeseed oil methyl ester (RME) as a biodiesel (B100) was applied to diesel engines equipped with high pressure loop (HPL) EGR system and low pressure loop (LPL) EGR system. Cooled HPL EGR was increased during steady-state operations and JE05 transient mode tests.

Application of biodiesel fuel (BDF) to diesel engine is very effective to reduce CO2 emission, because biodiesel is carbon neutral in principle. However, biodiesels yield an increase in NOx emission from conventional diesel engine, compared with diesel fuel case. Therefore, some strategies are needed for meeting the future emission regulations when using biodiesel. In this study, rapeseed oil methyl ester (RME) was applied to diesel engine equipped with exhaust gas recirculation (EGR) system and NOx storage reduction (NSR) catalyst. NOx reduction rate of NSR catalyst was drastically decreased by using RME, even if injection quantity of RME for rich spike was enhanced. However, an increase in EGR rate could reduce NOx emission without the deterioration in smoke and PM emissions.

The performance of a medium duty DME truck was evaluated by field tests and engine bench tests. The DME vehicle was given a public license plate on October 2004, after which running tests were continued on public roads and a test course. The DME vehicle could run the whole distance, about 500 km, without refueling. The average diesel equivalent fuel consumption of the fully loaded DME truck was 5.75 km/l, running at 80 km/h on public highways. Remedying several malfunctions that occurred in the power-train subsystems enhanced the vehicle performance and operation. The DME vehicle accumulated 13,000 km as of August, 2006 with no observed durability trouble of the fuel injection pump. Disassembly and inspection of the fuel injectors after 7,700 km operation revealed a few differences in the nozzle tip and the needle compared to diesel fuel operation. However, the injectors were used again after cleanup.

In this study, diesel exhaust emission characteristics were investigated as GTL (Gas To Liquid) fuel was applied to a heavy-duty diesel truck which had been developed to match a Japanese new long-term exhaust emission regulation (NOx < 2.0 g/kWh, PM < 0.027 g/kWh). The results in this study show that although the test vehicle has advanced technologies (e.g. high pressure fuel injection, oxidation catalyst, and urea-SCR aftertreatment system, etc.) which are applied to reduce diesel emissions, the neat GTL fuel has a great advantage to reduce particulate matter emissions and poly aromatic hydrocarbons. And regarding nano-size PM emissions, nuclei mode particles emitted during idling are significantly decreased by using the GTL fuel.

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 %.

It has been clarified that diesel fuel properties have a great effect on the exhaust emissions and fuel consumption of a conventional diesel combustion regime. And as other diesel combustion regimes are applied in order to improve exhaust emissions and fuel consumption, it can be supposed that the fuel properties also have significant effects. The purpose of this study is to propose the optimum diesel fuel properties for a premixed compression ignition (PCI) combustion regime. In this paper, the effect of the auto-ignitability of diesel fuels on exhaust emissions and fuel consumption was evaluated using a heavy-duty single-cylinder test engine. In all experiments, fuels were injected using an electronically controlled, common-rail diesel fuel injector, and most experiments were conducted under high EGR conditions in order to reduce NOx emissions.

The combustion mechanism of a fuel droplet cloud was studied by numerical simulation. We investigated how the flame front speed and combustion products changed depending on the equivalence ratio and initial temperature. Modeling was performed using the KIVA-III software package, a three dimensional analysis software used mainly for internal combustion engine applications. The computational domain was a horizontal 1x1x100 cell sector of a spherical combustion chamber and the fuel was n-decane. Results showed that when all the fuel droplets were assumed to have evaporated, the flame front speed increased from 28 cm/s to 152 cm/s as the equivalence ratio increased. The maximum flame front speed was reached at ϕ=1.1, beyond which it decreased (at richer overall equivalence ratios). With a constant equivalence ratio, the flame front speed decreased near the outside region, because the unburned gas was compressed by the expanding burned gas.

The emission reduction from diesel engines is one of major issues in heavy duty diesel engines. Super Clean Diesel (SCD) Engine for heavy-duty trucks has also been researched and developed since 2002. The main specifications of the SCD Engine are six cylinders in-line and 10.5 l with a turbo-intercooled and cooled EGR system. The common rail system, of which the maximum injection pressure is 200 MPa, is adopted. The turbocharger is capable of increasing boost pressure up to 501.3 kPa. The EGR system consists of both a high-pressure loop (HP) EGR system and a low-pressure loop (LP) EGR system. The combination of these EGR systems reduces NOx and PM emissions effectively in both steady-state and transient conditions. The emissions of the SCD Engine reach NOx=0.2 g/kWh and PM=0.01 g/kWh with aftertreatment system. The adopted aftertreatment system includes a Lean NOx Trap (LNT) and Diesel Particulate Filter (DPF).

The bore scope system can visualize not only diesel combustion in the research engine but also in actual diesel combustion in a multi-cylinder engine. The experimental engine has 2.0-liter displacement and has an external supercharger with up to two times the boost pressure of the naturally aspirated engine condition. The video camera used for this study is nac GX-1. From observed data under the several experimental conditions such as increased injection pressures, swirl ratios, and EGR rates, the flame temperature and KL factor were obtained by two-color method analysis. The diesel combustion processes are understood well by analyzing high-speed movies of the diesel flame motion and its temperature. NOx and smoke are mutually related to maximum flame temperature even in an engine with low NOx emission and lean smoke. It is reconfirmed as necessary to maintain a maximum flame temperature of 2,000–2,200K to reduce emissions of NOx and smoke simultaneously.

Lean NOx trap (LNT) and Urea-SCR system are effective aftertreatment systems as NOx reduction device in diesel engines. On the other hand, DPF has already been developed as PM reduction device and it has been used in various vehicles. LNT can absorb and reduce NOx emission in wide range exhaust temperatures, from 150°C to 400°C, and the size of LNT component can be compact in comparison with Urea-SCR system because LNT uses the diesel fuel as a reducing agent and it is needless to install the reducing agent tank in the vehicle. In this study, authors have shown that the NOx conversion rate of LNT is high in the case of extremely low NOx concentration from the engine. Also, the effects of LNT and DPF were examined using the Super Clean Diesel (SCD) Engine, which has low NOx level before aftertreatment and has been finished as Japanese national project.

For reducing NOx emissions, EGR is effective, but an excessive EGR rate causes the deterioration of smoke emission. Here, we have defined the EGR rate before the smoke emission deterioration while the EGR rate is increasing as the limiting EGR rate. In this study, the high rate of EGR is demonstrated to reduce BSNOx. The adapted methods are a high fuel injection pressure such as 200 MPa, a high boost pressure as 451.3 kPa at 2 MPa BMEP, and the air intake port that maintains a high air flow rate so as to achieve low exhaust emissions. Furthermore, for withstanding 2 MPa BMEP of engine load and high boosting, a ductile cast iron (FCD) piston was used. As the final effect, the installations of the new air intake port increased the limiting EGR rate by 5%, and fuel injection pressure of 200 MPa raised the limiting EGR rate by an additional 5%. By the demonstration of increasing boost pressure to 450 kPa from 400 kPa, the limiting EGR rate was achieved to 50%.

The tasks to improve diesel emissions and fuel consumption must be accomplished with urgency. However, due to the trade-off relationship between NOx emissions, soot emissions and fuel consumption, clean diesel combustion should be achieved by both innovative combustion and fuel technologies. The objective of this study is to extend the clean diesel combustion operating range (Engine-out emission: NOx ≺ 0.2 g/kWh, Soot ≺ 0.02 g/kWh). In this study, performance of a single-cylinder test engine equipped with a hydraulic valve actuation system and an ultra-high pressure fuel injection system was investigated. Also evaluated, were the effects of fuel properties such as auto-ignitability, volatility and aromatic hydrocarbon components, on combustion performance. The results show that applying a high EGR (Exhaust gas recirculation) rate can significantly reduce NOx emission with an increase in soot emission.

In this study, advantages of GTL fueled DI diesel engine were observed, then, some cautionary areas, notably the aptitude for sealing materials, were investigated. Some advantages of using GTL as a diesel engine fuel include reduction of soot emission levels, power output and fuel consumption with GTL to conventional diesel fuel operation is equivalent, super-low sulfur content of GTL and its liquid state at normal temperature and pressure. However, there are some problems with putting GTL fuel on the market, such as lubricity, aptitude for sealing materials, high cetane index and high pour point. It is necessary to use additives to improve GTL's lubricity, and selecting the most appropriate type of lubricity improver is also important. The influence of GTL on the swelling properties of standard rubber materials seem basically the same, but it is necessary to notice on used rubbers.

Since dimethyl ether (DME) is a synthetic fuel, it is possible to make it from natural gas, coal and biomass. It is a low-emission, oxygenated fuel, which does not generate soot in the exhaust. Therefore, it has recently been identified as a possible replacement for diesel fuel. In Japan, the new short-term emissions regulations will be enforced beginning in 2003, and the long-term emissions regulations are scheduled to be enforced in 2005. In order to meet these more stringent emissions regulations, existing diesel engines would not be as widely used in the near future as they currently are. This will thus bring about a more widespread use of DME engines due to their low emissions potential. Moreover, when the modification of existing diesel engines into DME engines is available at a moderate cost, the wider use of DME engines can be expected. This study targeted development and application of DME engine technology for diesel engine retrofit, in a used diesel vehicle.

In order to remove the diesel particulate matter (PM) and nitrogen oxides (NOx) from diesel exhaust, the gas is passed through a corona discharge collector for PM and another corona discharge device for NOx oxidation. With the PM collector, PM is accumulated on the central electrode, after that, it is removed by incineration technique. NOx concentration is decreased by oxidation to HNO3. In this study, these corona discharge reactors were coupled for removal of PM and NOx in progression, and attempted to remove these emissions in a slipstream of 14 liters/min of an experimental diesel engine and an actual vehicle, respectively. In case of the experimental test engine, it is found that nearly 100% and 15% of the PM and NOx emissions were removed even at a low input power of 26W (1560 J/L specific energy deposition). In the vehicle tests 1) a PM removal rate of 60% is obtained at an input power of over 40W, 2) a NOx removal rate of 97% is obtained at an input power of over 100W.

This work aimed to develop an LPG fueled direct injection SI engine, especially in order to improve the exhaust emission quality while maintaining high thermal efficiency comparable to a conventional engine. In-cylinder direct injection engines developed recently worldwide utilizes the stratified charge formation technique at low load, whereas at high load, a close-to-homogeneous charge is formed. Thus, compared to a conventional port injection engine, a significant improvement of fuel consumption and power can be achieved. To implement such a combustion strategy, the stratification of mixture charge is very important, and an understanding of its combustion process is also inevitably necessary. In this work, a numerical simulation was performed using a CFD code (KIVA-3), where the shape of a combustion chamber, swirl intensity, injection timing and duration, etc. were varied and their effects on the mixture formation and combustion process were investigated.

In this study, engine performances and exhaust emissions characteristics of compression ignition engine fueled with GTL were investigated by comparison with diesel fuel. Diesel engine could be operated fueled with GTL without any special modify for the test engine. With the high cetane number of GTL, the ignition lag was shorter, and the combustion started earlier than that of diesel fuel. Brake thermal efficiency operated with GTL increased at middle load conditions due to incomplete combustion emission such as CO and THC were lower than that of diesel fuel operation. NOx emission with GTL was comparable to diesel fuel, and there was a little decrease at high load. With GTL, soot emission was lower than with diesel fuel at above middle load condition. It seemed to be a reason of soot reduction that there was little sulphur contained in GTL.

Recently, dimethyl ether (DME) has been attracting much attention as a clean alternative fuel, since the thermal efficiency of DME powered diesel engine is comparable to diesel fuel operation and soot free combustion can be achieved. In this experiment, the effect of ambient pressure on DME spray was investigated with observation of droplet size such as Sauter mean diameter (SMD) by the shadowgraph and image processing method. The higher ambient pressure obstructs the growth of DME spray, therefore faster breakup was occurred, and liquid column was thicker with increasing the ambient pressure. Then engine performances and exhaust emissions characteristics of DME diesel engine were investigated with various compression ratios. The minimum compression ratio for the easy start and stable operation was obtained at compression ratio of about 12.

This research investigated the performance and emissions of a direct injection (DI) Diesel engine operated on 100% butane liquid petroleum gas (LPG). The LPG has a low cetane number, therefore di-tertiary-butyl peroxide (DTBP) and aliphatic hydrocarbon (AHC) were added to the LPG (100% butane) to enhance cetane number. With the cetane improver, stable Diesel engine operation over a wide range of the engine loads was possible. By changing the concentration of DTBP and AHC several different LPG blended fuels were obtained. In-cylinder visualization was also used in this research to check the combustion behavior. LPG and only AHC blended fuel showed NOX emission increased compared to Diesel fuel operation. Experimental result showed that the thermal efficiency of LPG powered Diesel engine was comparable to Diesel fuel operation. Exhaust emissions measurements showed that NOX and smoke could be considerably reduced with the blend of LPG, DTBP and AHC.

HCCI (Homogeneous Charge Compression Ignition) combustion results in very low NOx emissions, however, it is not without problems. One of them is that the heavy load operation range is limited by knock, due to an exceptionally high heat release rate. Knock increases the heat loss to the cylinder walls and piston, reducing thermal efficiency. To help solve these problems, direct (in-cylinder) water injection has been suggested to lower the local temperatures that seem to cause knock in HCCI. Water injection was adapted in an HCCI engine fueled with DME and Propane. Results showed that the indicated thermal efficiency was improved by about 2% (λ = 3.0, NA), and the operation range was expanded from 460kPa to 700kPa (NA) maintaining a low NOx level.