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The authors have previously proposed a plume ignition and combustion concept (i.e., PCC combustion), in which a hydrogen fuel is directly injected to the combustion chamber in the latter half of compression stroke and forms a richer mixture plume. By combusting the plume, both cooling losses and NOx formation are reduced. In this study, thermal efficiency was substantially improved and NOx formation was reduced with PCC combustion by optimizing such characteristics as direction and diameter of the jets in combination with combustion of lean mixture. Output power declined due to the lean mixture, however, was recovered by supercharging while keeping NOx emissions at the same level. Thermal efficiency was further improved by slightly re-optimizing the jet conditions.

The results of this study make clear the characteristics of electrode performance deterioration in terms of cell voltage reduction in polymer electrolyte fuel cells (PEFCs) caused by the presence of certain quantities of carbon monoxide and/or hydrogen sulfide in the anode feed. AC impedance measurements of the anode and cathode potentials revealed that both electrode potentials showed deterioration in the presence of each type of poisoning gas. This suggests that the poisoning gases permeated the electrolyte membrane and transferred to the cathode, causing performance deterioration by poisoning the catalyst. In addition, AC impedance measurements indicated that the presence of hydrogen sulfide in the anode feed increased the membrane impedance, thus implying some poisoning effect even on the electrolyte membrane.

This paper presents a study of mixture formation in the combustion chamber of a direct-injection SI engine. In-cylinder flow measurement was conducted using laser Doppler velocimetry (LDV) and particle image velocimetry (PIV), and visualization of fuel vapor behavior was done using laser-induced fluorescence (LIF). Further, fast response flame ionization detector (FID) was used to measure the hydrocarbon (HC) concentrations in the vicinity of the spark plug. Thereby mixture concentrations in the vicinity of the spark plug, within the mixture distribution observed using LIF, were quantified. Results revealed that an upward flow forms near the center of the cylinder in the latter half of the compression stroke and goes from the piston crown toward the cylinder head. This upward flow is caused by the synergistic effect of the swirl motion generated in the cylinder and the cylindrical bowl provided in the piston crown eccentrically to the central axis of the cylinder.

The study investigated the characteristics of the combustion, the emissions and the thermal efficiency of a direct injection diesel engine fuelled with neat n-butanol. Engine tests were conducted on a single cylinder four-stroke direct injection diesel engine. The engine ran at 6.5 bar IMEP and 1500 rpm engine speed. The intake pressure was boosted to 1.0 bar (gauge), and the injection pressure was controlled at 60 or 90 MPa. The injection timing and the exhaust gas recirculation (EGR) rate were adjusted to investigate the engine performance. The effect of the engine load on the engine performance was also investigated. The test results showed that the n-butanol fuel had significantly longer ignition delay than that of diesel fuel. n-Butanol generally led to a rapid heat release pattern in a short period, which resulted in an excessively high pressure rise rate. The pressure rise rate could be moderated by retarding the injection timing and lowering the injection pressure.

The results of our previous study showed that applying hydrogen (H2) to homogeneous charge compression ignition (HCCI) combustion with the assist of di-methyl ether (DME) as a supplement improved thermal efficiency compared with homogeneous hydrogen-fueled spark ignition (SI) combustion [1, 2]. As a general characteristic of HCCI combustion, however, stable engine operation is limited to a narrow region by the occurrence of misfiring and abrupt combustion like knocking. The onset of heat release is still not sufficiently controllable to achieve optimum engine performance. The objective of this study is to control the onset of the main heat release of hydrogen-fueled HCCI combustion by adopting spark ignition to assist autoignition. The results showed that improved thermal efficiency and reduced combustion fluctuation were achieved by attaining MBT operation with the support of spark ignition.

The effects of methanol and EGR on HCCI combustion of dimethyl ether have been tested separately in a diesel engine. The engine was equipped with a common rail injection system which allowed for random injection of DME. The engine could therefore be operated either as a normal DI CI engine or, by advancing the injection timing 360 CAD, as an HCCI engine. The compression ratio of the engine was reduced to 14.5 by enlarging the piston bowls. The engine was operated in HCCI mode with DME at an equivalence ratio of 0.25. To retard the combustion timing, methanol was port fuel injected and the optimum quantity required was determined. The added methanol increased the BMEP by increasing the total heat release and retarding the combustion to after TDC. Engine knock was reduced with increasing quantities of methanol. The highest BMEP was achieved when the equivalence ratio of methanol was around 0.12 at 1000 RPM, and around 0.76 at 1800 RPM. EGR was also used to retarding the timing.

The planned development of a hydrogen ICE system for trucks is one of the technological candidates for air pollution reduction and global warming prevention for the large-sized (heavy-duty) trucks supporting Japanese freightage. This project is the first to develop a DISI multi-cylinder hydrogen ICE system aimed at combining high power output and low NOx generation.

Laser induced fluorescence (LIF) is a useful method for visualizing the distribution of the air-fuel ratio in the combustion chamber. The way this method is applied mainly depends on the fluorescent tracer used, such as biacetyl, toluene, various aldehydes, fluoranthene or diethylketone, among others. Gasoline strongly absorbs light in the UV region, for example, at the 248-nm wavelength of broadband KrF excimer laser radiation. Therefore, when using this type of laser, iso-octane is employed as the fuel because it is transparent to 248-nm UV light. However, since the distillation curves of iso-octane and gasoline are different, it can be expected that their vaporization characteristics in the intake port and cylinder would also be different. The aim of this study was to find a better fuel for use with LIF at a broadband wavelength of 248 nm. Three tasks were undertaken in this study.

Hydrogen engines are required to provide high thermal efficiency and low nitrogen oxide (NOx) emissions. There are many possible combinations of injection pressure, injection timing, ignition timing, lambda and EGR rate that can be used in a direct-injection system for achieving such performance. In this study, several different combinations of injection and ignition timings were classified as possible combustion regimes, and experiments were conducted to make clear the differences in combustion conditions attributable to these timings. Lambda and the EGR rate were also evaluated for achieving the desired performance, and indicated thermal efficiency of over 45% was obtained at IMEP of 0.95 MPa. It was found that a hydrogen engine with a high-pressure direct-injection system has a high potential for improving thermal efficiency and reducing NOx emissions.

Advances in engine technology in recent years have led to significant reductions in the emission of pollutants and gains in efficiency. As a facet of investigations into clean, efficient combustion, the homogenous charge compression ignition (HCCI) mode of combustion can improve upon the thermal efficiency and nitrogen oxides emission of conventional spark ignition engines. With respect to conventional diesel engines, the low nitrogen oxides and particulate matter emissions reduce the requirements on the aftertreatment system to meet emission regulations. In this paper, n-butanol, an alcohol fuel with the potential to be derived from renewable sources, was used in a light-duty diesel research engine in the HCCI mode of combustion. Control of the combustion was implemented using the intake pressure and external exhaust gas recirculation. The moderate reactivity of butanol required the assistance of increased intake pressure for ignition at the lower engine load range.

In this study, a homogeneous mixture of natural-gas and air was used in a compression ignition engine to reduce NOx emissions and improve thermal efficiency. In order to control ignition timing and combustion, a small amount of DME was mixed with the natural-gas. Engine performance and the exhaust characteristics were investigated experimentally. Results show the following: the engine can run over quite a large load range if a certain amount of DME is added into natural-gas. By optimizing the proportion of DME to natural-gas, NOx emissions can be lowered to near zero levels if the mixture is lean enough. Thermal efficiency is higher than that obtained with normal diesel fuel operation.

An analysis of the factors that limit the improvement in thermal efficiency at higher compression ratios was performed with both thermodynamic calculation and experiment. The results showed that the major factors were cooling loss and unburned fuel. Both of these factors increase with smaller swept volume, larger S/V ratio combustion chamber, and lower engine speed and load. These effects explain the observation that thermal efficiency peaks at relatively low compression ratio.

Hydrogen is expected to be a clean and energy-efficient fuel for the next generation of power sources because it is CO2-free and has excellent combustion characteristics. In this study, an attempt was made to apply Homogeneous Charge Compression Ignition (HCCI) combustion to hydrogen with the aim of achieving low oxides of nitrogen (NOx) emissions and high fuel economy with the assistance of the di-methyl-ether (DME) fuel supplement. As a result, HCCI combustion of hydrogen mixed with 25 vol% DME achieved approximately a 30% improvement in fuel economy compared with HCCI of pure DME and spark-ignited lean-burn combustion of pure hydrogen under almost zero NOx emissions and low hydrocarbon (HC) emissions. This is attributed to control of the combustion process to attain the optimum onset of combustion and to a reduction of cooling losses.

Dual fuel applications of alcohol fuels such as ethanol or butanol through port injection with direct injection of diesel can be effective in reduction of NOx. However, these dual fuel applications are usually associated with an increase in the incomplete combustion products such as hydrocarbons (HC), carbon monoxide (CO), and hydrogen (H2) emissions. An analysis of these products of incomplete combustion and the resulting combustion efficiency penalty was made in the diesel ignited alcohol combustion modes. The effect of EGR application was evaluated using ethanol and butanol as the port injected fuel, with varying alcohol fractions at the mid-load condition (10 -12 bar IMEP). The impact of varying the engine load (5 bar to 19 bar IMEP) in the diesel ignited ethanol mode on the incomplete combustion products was also studied. Emission measurements were taken and the net fuel energy loss as a result of the incomplete combustion was estimated.

This study investigated neat n-butanol combustion, emissions and thermal efficiency characteristics in a compression ignition (CI) engine by using two fuelling techniques - port fuel injection (PFI) and direct injection (DI). Diesel fuel was used in this research for reference. The engine tests were conducted on a single-cylinder four-stroke DI diesel engine with a compression ratio of 18.2 : 1. An n-Butanol PFI system was installed to study the combustion characteristics of Homogeneous Charge Compression Ignition (HCCI). A common-rail fuel injection system was used to conduct the DI tests with n-butanol and diesel. 90 MPa injection pressure was used for the DI tests. The engine was run at 1500 rpm. The intake boost pressure, engine load, exhaust gas recirculation (EGR) ratio, and DI timing were independently controlled to investigate the engine performance.

In order to establish standard method to evaluate cooling loss in combustion chamber of internal combustion engines based on measurement of instantaneous heat flux / wall temperature with higher response and accuracy than previously reported coaxial type thin-film temperature sensor by applying thin film fabrication technology based on PVD method (Physical Vapor Deposition method) which improved to realize higher responsiveness than the conventional sensor was developed by the authors, and it was confirmed that the sensor has sufficient durability in conditions in which the hydrogen jet and flame directly contacts surface of the sensor by thin-film material change. The influence of the improvement on the measurement accuracy was verified by numerical analysis including thermoproperty evaluation. In this report, the configuration of measurement system that can measure minute voltage from the sensor with low noise and high response is reported.

In this study, impacts of neat n-butanol fuel injection parameters on direct injection (DI) compression ignition (CI) engine performance were investigated to gain knowledge for understanding the fuel injection strategies for n-butanol. The engine tests were conducted on a four-stroke single-cylinder DI CI engine with a compression ratio of 18.2:1. The effects of fuel injection pressure (40, 60 and 90 MPa) and injection timing in a single injection strategy were investigated. The results showed that an increase in injection pressure significantly reduced nitrogen oxides (NOx) emissions which is the opposite trend seen in conventional diesel combustion. The parallel use of a higher injection pressure and retarded injection timing was a proposed method to reduce NOx and cylinder pressure rise rate simultaneously. NOx was further reduced by using exhaust gas recirculation (EGR) while keeping near zero soot emissions.

High-speed laser shadowgraph cinematography synchronized with measurement of the pressure in the combustion chamber was employed in order to observe the location and magnitude of autoignition that causes cylinder gas oscillation. The use of a laser light source enabled the exposure time to be set at 0.8 microseconds with a high film speed of 30,000 f.p.s. . An image processing system was also used to determine the exact location of autoignited gases. The results clarified that the location of autoignition varied cycle-by-cycle. In some cycles it occurred in the vicinity of the cylinder wall, in some cycles it originated in the middle of the end gas and just in front of the propagating flame. It was also made clear that the occurrence of autoignition at a traceknock spark timing did not always bring about an oscillation in the chamber gases in case where the speed of the autoignited gas did not exceed a certain value.

The methodology of lubricity evaluation for DME fuel was established by special modified HFRR (High-Frequency Reciprocating Rig) such as Multi-Pressure/Temperature HFRR (MPT-HFRR). The obtained results were summarized as follows: The HFRR method is adaptable with DME fuel. There is no effect of the test pressure (up to 1.8 MPa) and the test temperature (up to 100°C) of MPT-HFRR on wear scar diameter. The results with MPT-HFRR can be applied at the sliding parts of the injection needle and the fuel supply pump's plungers which are secured lubricity by the boundary lubrication mode mainly and the mixed lubrication mode partially. Using the fatty-acid-based lubricity improver in amounts of approximately 100 ppm, the lubricity of DME, which has a lack of self-lubricity, is ensured as same as the diesel fuel equivalent level. There is a big deviation of measured wear scar diameter when the LI concentration is not enough.

The dual-fuel application using ethanol and diesel fuels can substantially improve the classical trade-off between oxides of nitrogen (NOx) and smoke, especially at moderate-to-high load conditions. However, at low engine load levels, the use of a low reactivity fuel in the dual-fuel application usually leads to increased incomplete combustion products that in turn result in a significant reduction of the engine thermal efficiency. In this work, engine tests are conducted on a high compression ratio, single cylinder dual-fuel engine that incorporates the diesel direct-injection and ethanol port-injection. Engine load levels are identified, at which, diesel combustion offers better efficiency than the dual-fuel combustion while attaining low NOx and smoke emissions. Thereafter, a cycle-to-cycle based closed-loop controller is implemented for the combustion phasing and engine load control in both the diesel and dual-fuel combustion regimes.