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In an attempt to grab potential issues with a hydrogen direct injection lean burn engine to have similar power output to a gasoline-fuelled engine, emission characteristics of a hydrogen engine was investigated. It is demonstrated that low NOx emission can be achievable without any catalytic converter. Two major issues, however, have been recognized, that is, combustion instability at low load conditions and too low temperature of exhaust gas to get enough boosting pressure. Hydrogen concentration heterogeneous of the mixture was focused in the CFD and visualization study. Hydrogen jet design of an injector could contribute to improvement of mixing.

A new 660cc turbo-charged Spark-Ignition Direct-Injection (SIDI) engine was developed. The mini-car equipped with this engine is the first mini-car with a turbocharged SIDI engine to receive the Japanese Ultra-Low-Emission-Vehicle (ULEV) certification. The vehicle achieved a 5.7% fuel economy improvement on the Japanese 10-15 mode compared to the mini-car equipped with the baseline port fuel injection (PFI) engine. The baseline engine is currently used for both the mini-car and snow mobile vehicles, and it is feasible to expand the SIDI engine application to also cover snow mobile applications, and achieve the demonstrated benefits of low emission, low fuel consumption and high engine output

The purpose of this study was to find compatible specifications both of emission reduction and high power output with good throttle response for a sports utility motorcycle. In the emission reduction challenge, we examined equipping the exhaust system with a catalytic converter to achieve sufficient emission reduction. The catalytic converter, however, caused a temperature rise in the exhaust system, which caused a pressure propagation change. Additional muffler design optimization effectively maintained high performance and acceleration. The exhaust valve device was also optimized for emission reduction and high power output over a wide engine speed range. The optimized control of the exhaust valve was beneficial to preventing short-circuit of fresh mixture gas and early activation of the catalyst. Such comprehensive specifications could satisfy the performance and driveability characteristics required for sports utility motorcycles.

The purpose of this study is to reveal the flame propagation characteristics. Planar OH* image and local radical emission were measured simultaneously. Planar OH* images were used to analyze the flame propagation characteristics by high-speed camera. These images were then used to evaluate the speed of distribution and the direction of flame propagation. By comparing local point radical emission and planar OH*, the flame propagation characteristics was measured and evaluate that. And the time history of the radical intensity and planar OH* distribution were compared. The relation ship between flame propagation speed and initial heat generation was discussed. The variation of flame propagation speed and the difference of propagation speed in both port sides were confirmed.

The purpose of this study is to evaluate the effect of an exhaust throttle installed in an exhaust pipe in a two-stroke motorcycle engine. In the experimental study, the exhaust-throttle system prevented fresh-gas from short-circuiting and consequently, improved unburnt hydrocarbon emissions and fuel economy, along with enhancing combustion stability. In actual running, in order to minimize HC emission level and stabilize cycle-to-cycle fluctuation of combustion including intermittent misfiring, an air-induction system and a long-duration spark ignition were used in addition to the exhaust throttle system. The control software for the integrated system was also a key point in improving HC and CO emission levels in the ECE-40 operation cycle. For detecting misfiring in the ECE-40 cycle, time-resolved HC variation was measured by a fast-response gas analyzer.

The purpose of this study was to detect a misfiring cycle in terms of the transfer-passage and the exhaust-pipe flow rate by experimental measurements. Simultaneous measurements of flow rates and in-cylinder pressure were carried out. The flow rate data were grouped into the different combustion classes by the in-cylinder pressure. A large flow rate of exhaust blow-down and a large reverse flow rate were observed in the cycle before misfiring, compared with in the cycle before firing. It showed that high concentration of the residual burnt gas in the cylinder was the main source of misfiring, this feature was also demonstrated by the complementary measurement of CO and CO2 concentrations.

The purpose of this study is to show cycle-to-cycle combustion variation in transient conditions of quick throttle opening and to control the combustion fluctuation improve acceleration in a two-stroke motorcycle engine. Two phases of engine operation were focused on: the low-load condition before quick throttle opening, and the transient condition after quick throttle opening. The time-series variation of the heat release rate based on the in-cylinder pressure, the engine-speed and the exhaust pressure variation were measured simultaneously, in an engine with a new multiple-timing-ignition-system, and in an engine with a modified exhaust port. Stable ignition performance and fast burning velocity were the keys to attaining smooth acceleration.

The purpose of this study is to experimentally investigate in-cylinder flows with cyclic variation in a practical part-loaded two-stroke engine. First, the in-cylinder LDV measurements are introduced, which were carried out above the port layout and the combustion chamber as well as the exhaust pipe or the transfer port together with the simultaneous pressure measurements. Second, the in-cylinder flow characteristics in different combustion groups were discussed. The in-cylinder flow and the combustion-chamber flow were not simply characterized by the pressure variation in the engine or the other passage flow in the exhaust pipe or the transfer port. Finally, the in-cylinder flow structure with three stages was shown using the vector variation analysis and the drawing of the velocity profiles in the engine parts.

The purpose of this study is to experimentally understand the cyclic variation of combustion state in a two-stroke engine with respect to the variations in scavenging flow and the CO and CO2 emissions. The criteria of grouping combustion states into misfiring were established using the in-cylinder pressure at the crankangle of maximum variability in peak pressure instead of indicated mean effective pressure. The CO and CO2 emissions and the flow velocity variations in the transfer port and the exhaust pipe were measured. Combustion of each cycle was grouped into misfiring, incomplete firing or firing by the criteria of the in-cylinder pressure. In the cycle before misfiring, the CO and CO2 concentration showed high level and the first peak of the exhaust flow showed large velocity and the positive velocity remained for long duration, and the exhaust and the transfer port flow were steeply decelerated to negative velocity midway between scavenge port opening and bottom dead center.

Misfiring cycles were detected by a conditional sampling method to demonstrate the differences between firing and misfiring of the scavenging flow characteristics at the scavenging port and exhaust pipe using LDV method. The results show that the flow at the scavenging port was not influenced significantly by misfiring, but the blowdown flow in the exhaust pipe greatly depended on the combustion status. The blow-down flow of fired cycles at a light-load condition was very similar to the flow at a full-load condition. It was also found that measured flow characteristics at partial load should not be considered by averaging firing and misfiring cycles. The occurrence pattern of misfiring should be quantified and considered in the analysis.

The velocity variations of the burnt exhaust gas in a practical fired two-stroke engine operating under wide-open-throttle conditions were measured by a fiber LDV ( FLDV ). The characteristics of the exhaust flow are discussed in comparison with those in motoring and in a transfer port. The relation between velocity variation and pressure wave propagation in the exhaust pipe are also investigated. The measured results show that the velocity distribution in the exhaust pipe can be characterized as pulsative flow. The flow characteristics had large influence by the combustion pressure wave propagation. During exhaust and transfer-port opening, the intake flow and the blow-down flow have similar velocity gradient and peak location. The velocity distribution in the exhaust pipe was also measured, which showed pulsative flow variation having no recirculating vortex.