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Personal mobile vehicles have been extensively studied recently, for the benefit of fuel economy and transportation efficiency. This study proposes a personal vehicle system comprising a new tilting mechanism -Stephenson six-bar linkage- combined with a new diamond-shape wheel arrangement chassis for high maneuverability. The present personal concept vehicle not only makes all the wheels and body lean simultaneously, and achieves an effective tilting angle of 32° in cornering, but can also, in normal attitude, turn in a narrow space with the steering front wheel and freely steering rear wheel. The current prototype of the proposed diamond-shape tilting chassis of personal vehicle concept, driven by 1.5kW hub motor in the front wheel, tandem two-seat, is 1m wide by 2.1m long. Preliminary test results indicate that the minimum turning radius is 1.05m for turn-in-spot, and the anti-rollover capability is almost 0.5g.

Two micro injection pumps technology were introduced to a new fuel injection concept called micro-pulsation fuel injection system. A micro thermal bubble injection pump made by MEMS fabrication process had 100 micropumps with nozzle of 80μm diameter to be built in a chip. The flow rate achieves about 4.9cc/min with less than 90μm droplet size and 1.5×109 cycle time at 2 kHz. The piezoelectric plate pump included a small bimoph piezoelectric plate and 3mm × 7mm ×100μm array nozzle plate ejects about 2.4cc/min flow rate with about 49μm SMD droplet size at 17kHz frequency.

A new fuel injection concept called micro-pulsation fuel injection (μPFi) system had been developed for an internal combustion engine. The μPFi system composes an engine management system, a fuel-circulating device, and thermal-bubble fuel injectors with micropumps. The μPFi system had been installed in a commercial 4 stroke, 125cc motorcycle and tested in engine and chassis dynamometers. The measured CO and HC+NOx emissions were 1.5g/km and 1.14g/km respectively in ECE-40 test mode without catalyst converter and secondary air. The results showed that the motorcycle with μPFi system achieves superior exhaust CO emissions than the carburetor system while keeping comparable vehicle performance.

A control system for the intake flow on 4-stroke engines had been developed. It was named the VIP (Variable Intake Port) system. Such system was proved an effective strategy to achieve fast lean-bum at part load and to increase volumetric efficiency at wide open throttle. Test results showed that the maximum power of the VIP engine could rise more than 9 % in comparison with the original one. Under the ECE-40 test mode, this VIP motorcycle, without catalyst and secondary air system, could improve at least 16 % on fuel consumption. Emissions of HC+NOx was reduced from 1.07 to 1.00 g/km, and CO from 3.69 to 0.75 g/km. Not only the combustion variations at part load were improved, but also the maximum vehicle speed and the vehicle acceleration were superior to the original motorcycle.

From the investigations carried out in the two-stroke cycle engine with in-cylinder injection system, it was found that the level of hydrocarbon emissions from the engine was still too high if compared to that of an ordinary four-stroke cycle engine. For such high level of hydrocarbon emissions, it could be identified as coming from the mixture misfiring during the combustion process rather than the mixture short-circuiting during the scavenging process. The reasons for inducing the occurrence of mixture misfiring were also under investigation and could be further classified into five major categories: poor atomization of fuel spray, excessive amount of residual gas, instability of in-cylinder air flow, wall-wetting of the injected fuel spray and phenomena of secondary fuel injection. To overcome the above problems, respective new approaches have been therefore developed.

Experimental studies of the intake-generated charge motion (swirl and tumble) and engine combustion were conducted in a 125 cc four-stroke motorcycle engine. In this work, a Variable Inlet Port (VIP) was designed to generate various levels of charge motion in different operation conditions. The static flow test and the engine experiments were performed to study the effects of inlet charge motion on the engine combustion, cycle variation, fuel consumption and exhaust emissions. The results show that the cycle variation decreased, the lean limit extended, the burning rate and the fuel economy increased when the charge motion increased. With this new design of flow control system, the motorcycle can be run with lean mixture and drastically reduce the exhaust emissions and fuel consumption while still maintaining high specific power output.

In a two-stroke gasoline engine, the in-cylinder spray pattern and fuel atomization of an air-assisted fuel injection system is analyzed. The visualization of the spray inside of the cylinder is achieved by taking photographs through endoscope mounted in the cylinder head viewing the cylinder. The interaction between the fuel spray and in-cylinder flow motion is thus observed. The spray droplet size is measured by a PDPA(Phase Doppler Particle Analyzer) in an open chamber test rig. The results show that air-assisted fuel-injection system achieves much better atomization than the traditional low-pressure solid fuel injection system. The droplet size at the center of spray plume decreases with the increase of fuel injection rate. Also, the optimal air injection timing relative to the fuel injection timing on the droplet size is also investigated.

For a crankcase-scavenged two-stroke cycle S.I. engine, the irregular combustion at light loads results in engine instability and high exhaust hydrocarbon emissions. It is recognized that the poor scavenging process is one of the major contributing factors. From the test data of a single cylinder fuel injected two-stroke cycle engine, it was found that at certain light load conditions the exhaust charge flow could strongly affect the combustion stability. A butterfly valve controlling the passage area of exhaust pipe was designed and installed in the engine to investigate the effect of exhaust charge control strategy on combustion. Test results showed that the exhaust contraction ratio should decrease with decreasing load and speed in order to achieve the improved combustion stability and lower hydrocarbon emissions.

A low-pressure air-assisted fuel injection system had been applied to a 2-stroke motorcycle to reduce the fuel consumption and emissions. This system injected atomized fuel into cylinder through a nozzle located in cylinder wall and resulted in fuel economy and emission improvements. In the ECE40 test, the average fuel consumption and hydrocarbon emission of the fuel-injected motorcycle were reduced by 27.5% and 38.3% compared to the carburetor version.

An air-assisted direct injection system has been developed and applied to a two-stroke spark-ignited motorcycle engine of 82 c.c. displacement to reduce exhaust emissions, particularly unburnt hydrocarbons. The injection system, which induces a small amount of compressed air and metered fuel from electronic-control valve, delivers the air/fuel mixture into the cylinder. This paper shows the preliminary results of engine dynamometer tests. Also investigated are the improvement of combustion and reduction of unburnt HC emission by the use of dual spark plugs and skip injection techniques at light load engine condition.