• Transactions of the Korean hydrogen and new energy society
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• v.20 no.5
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• pp.371-377
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• 2009

Backfire characteristics for hydrogen fueled free piston engine with uni-flow scavenging is investigated with different stroke, exhaust vlave openning timing and fuel-air equivalence ratio by using RICEM (Rapid Intake Compression Expansion Machine) for combustion research of free piston engine. As results, it is found that backfire can be occurred due to slow combustion of unhomogeneous mixture in the piston crevice volume or/and in the cylinder near piston head. And the more stroke of free piston H2 engine with uni-flow scavenging is short the more opening timing of exhaust valve have to be advanced to control backfire.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.373-381
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• 2012

To determine the performance characteristics of motorcycle engine using biogas for practical use, the intake system of a 110 cc motorcycle engine is properly modified to operate with biogas as a fuel. Biogas is a potentially renewable fuel for replacing gasoline in future, but it has high percentage of $CO_2$ that could lead to slow the burning rate of biogas-air mixture and cause instability in combustion. Thus, the performance characteristics of biogas-fueled motorcycle engines could be different from those of gasoline motorcycle engines. In this paper, the important parameters of performance characteristics (such as: power output, thermal efficiency, fuel consumption, exhaust emission,${\cdots}$) of biogas-fueled motorcycle engine are studied and estimated with change of engine speed and load. The obtained results when operating with biogas are used to compare with that of gasoline fuel under the same operating conditions. Engine speed in the experimental is changed from 1500 rpm (idle-mode) up to 3500 rpm by a step of 500 rpm. Engine load is changed from zero to maximum load with the help of an exciting voltage device from generator-type dynamometer. The experimental results show that the tested engine operated with richer biogas-air mixture than that of gasoline-air mixture under the same test conditions. Biogas-fueled engine gives a higher fuel consumption and lower thermal efficiency under the same power output. Brake thermal efficiency of biogas engine is found to be about 3% lower than gasoline-fueled motorcycle engine for whole range of speed. Exhaust emission of biogas-fueled motorcycle engine (such as: CO, HC) is found to be lower than the limitation level of the emission standards of Vietnam for motorcycle engines (CO <4.5% HC <1200 ppm).

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.3
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• pp.107-117
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• 2000

Ball poppet valve type high pressure hydrogen injection valve actuated by solenoid has been developed for the feasibility of practical use of hydrogen fueled engine with direct injection and the precise control of fuel injection ratio in hydrogen fueled engine with dual injection. The gas-tightness of ball poppet injection valve is improved by the introduction of ball-shaped valve face, valve end typed spherical pair, and valve stem with rotating blade. Ball poppet valve is mainly closed by differential pressure due to the area difference between valve fillet and pressure piston. So, it can be operated by solenoid actuator with small driving force. From the evaluation of ball poppet injection valve, it was found that the gastightness and controlment of this injection valve are better than those of injection valve had been developed before.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1702-1708
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• 1995

Owing to the serious problem of hydrocarbon fuel such as environmental pollution, the development of alternative fuel is very urgent. To adopt hydrogen to the internal combustion engine, a solenoid-drive type in-cylinder injection system was constructed. The injection system was installed to the single cylinder research engine, and the engine performance and the emission of citric oxide were tested upon the fuel-air equivalence ratio and the spark timing. In the case of in-cylinder injection system, hydrogen is injected after the intake valve is close, so it is possible to operate the engine without the back fire and the fall of its volumetric efficiency. In the region of the fuel-air equivalence ratio below 0.5, hydrogen and air aren't well mixed and the thermal efficiency is lowered, so the nozzle should be designed to inject hydrogen uniformly into the combustion chamber. In the region of the fuel-air equivalence ratio above 0.7,the fuel-air mixture burns very fast and the amount of citric oxide emission increases rapidly, so the spark timing should be retarded as compared with MBT.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.4
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• pp.374-381
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• 2007

In order to verify the feasibility of expansion of back-fire limit equivalence ratio in the hydrogen-fueled engine with external mixture, the characteristics of performance and combustion are experimentally analyzed with change of intake/exhaust valve timings under the fixed valve overlap period of $0^{\circ}$ CA(non-valve overlap period). These characteristics are also tested for the change of exhaust valve closing timing while intake valve opening timing is fixed to clear the main cause of back-fire occurrence. As the results, the less valve overlap period center is retarded, the more back-fire limit equivalence ratio increases and back-fire does not occurred after TDC. In addition, it was shown that the control of back-fire is dependent on intake valve opening timing than valve overlap period.

• Journal of the korean Society of Automotive Engineers
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• v.6 no.2
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• pp.47-54
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• 1984

The predictions of the mean effective pressure and the exhaust emission of NOx in hydrogen fueled spark ignition engine were studied. And the predictions were compared to the experimental results of D.B. Kittelson and H.S.Homan. The modeling was based on Otto cycle and the prediction of NOx was performed by extended Zeldovich mechanism. The differences between predictions and experimental results were 20 - 30% in the mean effective pressure and 10 - 20% in the concentration of NOx where the equivalence ratio .phi. was 0.6 - 0.8.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.98-103
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• 2010

In order to develop two-stroke free-piston hydrogen engine to obtain high thermal efficiency and low emission, backfire occurrence have to be prevented. In this research, backfire characteristics are analyzed as functions of the intake valve opening timing and compression chamber pressure under piston by using RICEM (Rapid Intake Compression Expansion Machine) that has reverse uni-flow scavenging. As the result, reverse uni-flow scavenging is advantage about back fire. but, it exists suitable intake valve opening timing and its timing become known that equivalence ratio 1 retard until the piston rises. Also, To rise chamber pressure of lower piston, this does not cause backfire occurs in equivalent ratio 0.6 observed back fire. Therefore, 2cycle hydrogen fueled free-piston engine is undesirable scavenging compression by compressing the piston.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.3
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• pp.182-188
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• 2008

In order to improve scavenging performance of free piston hydrogen fueled engine, this study estimate compatibility of uni-flow scavenging. The scavenging flow characteristics in the cylinder is investigated by flow visualization and PIV method. Consequently it has been found that the scavenging performance decreased with abnormal expansion of piston and delay of the exhaust valve opening timing. And the scavenging performance of exhaust valve located center in cylinder head is better than that of exhaust valve located side in cylinder head.

• Journal of the Korean Institute of Gas
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• v.24 no.6
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• pp.28-33
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• 2020

In this study the possibility of hydrogen as a fuel in a small-sized two-stroke SI (Spark ignition) engine was investigated. For this purpose, experimental setup including an engine, a dynamometer, equipments for hydrogen and lubricant oil supply was prepared. And then preliminary experiments for the hydrogen-fueled engine combustion were conducted. In the case of hydrogen-fueled engines comparing to gasoline backfire occurs when the excess air ratio is lower than a specific value. This can cause engine power reduction and damage to the engine parts. The engine was controlled to operate at lean conditions to prevent backfire. Through the control of excess air ratio, the maximum engine brake power output of 3 kW was achieved in a 210 cc engine, while it was 6 kW in case of gasoline fuel.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.3
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• pp.103-110
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• 2003

The present work was conducted to achieve the better understanding of the performance analysis technique for the expander type air turbo ramjet engine. For this purpose, the performance analysis was carried out using a small engine(8.0kN thrust) with two types of fuels. From this analysis, at the same input condition, the thrust of methane-fueled engine was 25% lower than that of hydrogen. In addition, the case of methane shows the inapplicable engine performance cycle.(i.e., The compressor work exceeds the turbine output power) These results come mainly from the different heating value of each fuel and specific heat. This analysis also shows that, to build a same performance cycle as the hydrogen case, the methane-fueled engine requires increased air and fuel flow rates, increased turbine expansion ratio, and decreased compressor pressure ratio.