• 한국수소및신에너지학회논문집
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• 제33권3호
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• pp.255-260
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• 2022

Hydrogen gas fuel was applied to a small-sized two stroke engine for a mobile power source instead of gasoline fuel. Port fuel supply showed a limitation in terms of power due to the back fire at the engine intake manifold. So in this study, hydrogen direct injection system was applied to overcome this drawback by using a low pressure direct gas injector. The result from this strategy showed that hydrogen direct injection improved fuel efficiency as well as torque and power comparing to the port fuel supply system.

• 한국수소및신에너지학회논문집
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• 제27권1호
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• pp.106-113
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• 2016

Lean burn engine, classified into port injection and direct injection, is recognized as a promising way to meet better fuel economy. Especially, LPG direct injection engine is becoming increasingly popular due to their potential for improved fuel economy and emissions. Also, LPDi engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. However, LPDi engine has many difficulties to be solved, such as complexity of injection control mode (fuel injection timing, injection rate), fuel injection pressure, spark timing, unburned hydrocarbon and restricted power. This study is investigated to the influence of spark timing, fuel injection position and fuel injection rate on the combustion stability of LPDi engine. Piston shape is constituted the bowl type piston. The characteristics of combustion is analyzed with the variations of spark timing, fuel injection position and fuel injection rate (early injection, late injection) in a LPDi engine.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3090-3095
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• 2008

In this study, variable compression ratio system(VCRS) was applied on the heavy-duty CNG engine and the characteristics of power and emission was investigated according to the increasing of compression ratio. As compression ratio increasing, the increasing of thermal efficiency in direct injection is three times higher than that in port injection. The emission of HC and CO in direct injection is reduced about 14.2%, 17.7% but NOx is increased because of increasing temperature in cylinder.

• 동력기계공학회지
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• 제20권2호
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• pp.32-42
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• 2016

Under part load condition of spark-ignition engine, pumping loss had great effect on engine efficiency. To reduce pumping loss, the study designed spark-ignited engines to make direct spray of gasoline to combustion chamber. In spark-ignited direct-injection engines, ignition probability is important for successful combustion and flame propagation characteristics are also different from pre-mixed combustion. This study designed a visualization testing device to study ignition probability of spark-ignited direct-injection LPG fuel and combustion flame characteristics. This visualization device consists of combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. Ambient pressure, ambient temperature and ambient air flow velocity are important parameters on ignition probability of LPG-air mixture and flame propagation characteristics, and the study also found that sprayed LPG fuel can be directly ignited by spark-plug under proper ambient conditions. To all successful cases of ignition, the study recorded flame propagation image in digital method through ICCD camera and its flame propagation characteristics were analyzed.

• 동력기계공학회지
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• 제19권4호
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• pp.56-68
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• 2015

Liquefied petroleum gas and compressed natural gas haven been regarded as promising alternative fuels because of no smoke, and they are also clean fuel for spark-ignited engine. In spark-ignited direct-injection engine, direct injection technology can increase engine volumetric efficiency significantly and also reduce necessity of throttle valve. This study designed combustion chamber equipped with visualization system. To improve ignition probability, the study designed to help three types of impingement-walls to form mixture. In doing so, LPG CNG-air mixture could be easily formed after spray-wall impingement and ignition probability increased too. The results of this study could contribute as basic resources of spark-ignited direct injection LPG and CNG engine design and optimization extensively.

• Journal of Power Electronics
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• 제9권4호
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• pp.582-592
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• 2009

This paper proposes a new speed sensorless direct torque and flux controlled interior permanent magnet synchronous motor (IPMSM) drive. Closed-loop control of both the torque and stator flux linkage are achieved by using two proportional-integral (PI) controllers. The reference voltage vectors are generated by a SVM unit. The drive uses an adaptive sliding mode observer for joint stator flux and rotor speed estimation. Global asymptotic stability of the observer is achieved via Lyapunov analysis. At low speeds, the observer is combined with the high frequency signal injection technique for stable operation down to standstill. Hence, the sensorless drive is capable of exhibiting high dynamic and steady-state performances over a wide speed range. The operating range of the direct torque and flux controlled (DTFC) drive is extended into the high speed region by incorporating field weakening. Experimental results confirm the effectiveness of the proposed method.

• 동력기계공학회지
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• 제22권1호
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• pp.56-63
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• 2018

After the recent fabrication of diesel vehicle exhaust gas by Volkswagen, nitrogen oxides ($NO_x$) and particulate matter (PM) are drawing attention as representative pollutants included in exhaust gas. When gasoline and diesel fuels are combusted through direct injection into a combustion chamber at high pressure, PM emission is actually increased. To find a solution to this problem, a basic study was conducted to derive an optimized variable for combustion of compressed natural gas (CNG) by applying CNG, acknowledged as a clean fuel, to direct injection system. The essence of this study is in the introduction of a radical ignition technology for compressed natural gas (RI-CNG) in a sub-chamber type engine. The direct injection system was applied to a sub-chamber to remove residual gas from previous combustion cycle. In addition, optimal mixer distribution was achieved by precisely setting ignition timing based on fuel injection timing and excess air ratio.

• 동력기계공학회지
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• 제19권2호
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• pp.49-56
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• 2015

As an alternative fuel that can be used in SI engine, LPG is one of clean fuels with larger H/C ratio compared to gasoline, low $CO_2$ emission, and small amount of pollutants such as sulfur compounds. When LPG is used in spark ignition engine, volumetric efficiency of the engine can be improved and pumping loss can be reduced by performing direct injection into the combustion chamber instead of port fuel injection. LPG-DI engine allows for lean combustion and stratified combustion under low load. In case of stratified combustion, air fuel ratio can be greatly increased compared to theoretic mixture ratio combustion. Improved thermal efficiency of the engine and reduced pumping loss can be expected from stratified combustion. Accordingly in this study, an experimental apparatus for visualization was designed and manufactured to study the combustion process of LPG after injection and ignition, intended to examine ignition probability and combustion characteristics of spark ignition direct injection(SIDI) LPG fuel. Ambient pressure, ambient temperature and fuel injection pressure were found as important variables that affect ignition probability and flame propagation characteristics of LPG-air mixture. Also, it was verified that the injected LPG fuel can be directly ignited by spark plug under appropriate ambient conditions.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.155-165
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• 2013

The effect of gaseous ammonia direct injection on the engine performance and exhaust emissions in gasoline-ammonia dual fueled spark-ignition engine was investigated in this study. Results show that based on the gasoline contribution engine power increases as the ammonia injection timing and duration is advanced and increased, respectively. However, as the initial amount of gasoline is increased the maximum power output contribution from ammonia is reduced. For gasoline-ammonia, the appropriate injection timing is found to range from 320 BTDC at low loads to 370 BTDC at high loads and the peak pressures are slightly lower than that for gasoline due to the slow flame speed of ammonia, resulting in the reduction of combustion efficiency. The brake specific energy consumption (BSEC) for gasoline-ammonia has little difference compared to the BSEC for gasoline only. Ammonia direct injection causes slight reduction of $CO_2$ and CO for all presented loads but significantly increases HC due to the low combustion efficiency of ammonia. Also, ammonia direct injection results in both increased ammonia and NOx in the exhaust due to formation of fuel NOx and ammonia slip.

• 대한기계학회논문집B
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• 제22권8호
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• pp.1101-1110
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• 1998

Computational investigation was conducted to examine the performance of a high pressure common-rail fuel injection system which is used to power a passenger car direct injection (Dl) diesel engine. The pipe flows were modeled by one dimensional wave equation and solved by implicit FDM Each volume of injector was considered as chambers with orifice nozzle in connections. These simulation results were compared with the experimental data of Ganser Hydromag. The comparison of needle life and rate of injection between simulation data and experimental data showed quite a good agreement Different shape of injection rate can be made by adjusting the size of inlet orifice and exit orifice in the piston chamber The pilot injection was accomplished by adjusting command signal.