• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1050-1056
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• 2010

Diesel engines introduce only air into the cylinder, and the air is high lycompressed. Fuel is directly injected into the combustion chamber in high temperature and pressure. Therefore diesel engines have high thermal efficiency because of the high compression ratio, while having high level of particulate matter and nitrogen oxide emissions because of the direct fuel injection. Many technologies have been developed to reduce particulate matter and nitrogen oxide emissions from diesel engines. One of the technologies is hydrogen fuel introduced into the combustion chamber with diesel fuel. In this thesis tiny amount of hydrogen is supplied into the combustion chamber in order to enhance the combustion performance. The engine, in which hydrogen is introduced, is tested. There are 20 test conditions given as 5 torque values of 100%, 75%, 50%, 25%, 0%, and 4 engine speeds of 700rpm, 1000rpm, 1500rpm and 2000rpm for the two cases with or without hydrogen addition. Maximum torques and Idle torques at each engine speed are measured, then the torque values are divided into 4 levels with 25% increasing step. The result shows that the fuel consumption, smoke, CO are reduced while the NOx emission is slightly increased, and the hydrogen addition has not a great effect on the performance at low loads but a great effect at a maximum load.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.118-125
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• 2009

Calculation of indicated mean effective pressure(IMEP) requires high cylinder pressure sampling rate and heavy computational load. Because of that, it is difficult to implement in a conventional electronic control unit. In this paper, a cylinder pressure based real-time IMEP estimation method is proposed for controller implementation. Crank angle at 10-bar difference pressure($CA_{DP10}$) and cylinder pressure difference between $60^{\circ}$ ATDC and $60^{\circ}$ BTDC($DP_{deg}$) are used for IMEP estimation. These pressure variables can represent effectively start of combustion(SOC) and fuel injection quantity respectively. The proposed IMEP estimation method is validated by transient engine operation using a common-rail direct injection diesel engine.

• Journal of Power System Engineering
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• v.19 no.2
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• pp.64-69
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• 2015

Marine diesel engines with high thermal efficiency and fuel diversity used for propulsive power have been taking charge of important position on marine transport. However, marine environment has recently focused on emissions such as nitrogen oxide and sulfur oxide which is generated from combustion of low grade fuels. EGR(Exhaust gas recirculation) system is one of effective methods to reduce the nitrogen oxide emission from marine diesel engines. In general, it is considered that recirculating gas influences fuel combustion and emissions in diesel engines. However, along with positive effects of EGR, the EGR system using fuels of including high sulfur concentration should be considered about re-combustion and activation of sulfur dioxide in recirculating gas. Therefore, in experimental study, an author investigates effects of sulfur dioxide mixture concentration in intake air on combustion and exhaust emission characteristics in a direct injection diesel engine. In results, change of sulfur dioxide concentrations in intake air had negligible impact on combustion chamber pressure, rate of heat release and emissions compared with effects of oxygen decreasing and carbon dioxide increasing of EGR.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.73-83
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• 2014

CFD(computational fluid dynamics) model is developed to simulate direct injection of ammonia gas phase from ammonia transporting materials into the SCR catalyst in the exhaust pipe of the engine with solid SCR. Configurations of one-hole and four-hole nozzle, circumferential type, porous tube type, and the effect of mixer configurations which commonly used in liquid injection of AdBlue are considered for complex geometries. Mal-distribution index related to concentration of ammonia gas, flow uniformity index related to velocity distribution, and pressure drop related to flow resistance are compared for different configurations of complex geometries at the front section of SCR catalyst. These results are used to design the injection system of ammonia gas phase for solid SCR of target vehicle.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.83-87
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• 2008

We have a lot of interest in alternative fuels to provide energy independence from oil producing country and to reduce exhaust emissions for air pollution prevention. Biodiesel, which can be generated from natural renewable sources such as new or used vegetable oils or animal fats, may be used as fuel without change of engine structure in diesel engine of compression ignition engine. In this paper, the test results on specific fuel consumption and exhaust emissions of neat diesel oil and biodiesel blends(10 vol.% biodiesel and 20 vol.% biodiesel) were presented using four stroke, direct injection diesel engine. Especially this biodisel was produced from rape oil at our laboratory by ourselves. This study showed that specific fuel consumption and NOx emission were slightly increased, on the other hand CO emission and Soot were tolerably decreased more in the case of biodiesel blends than neat diesel oil.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.16-21
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• 2015

Nitrous oxide($N_2O$) concentration in the atmosphere has been constantly increased by the human activities with industrial growth after the industrial revolution. One of factors to increase $N_2O$ concentration in the atmosphere is the $N_2O$ emission caused by the combustion of marine fuel. Especially, a sulfur component included in marine fuel oils is known as increasing the $N_2O$ formation in diesel combustion. Form this point of view, $N_2O$ emission from a ship is not negligible. On the other hand, Exhaust gas recirculation(EGR) that have thermal, chemical and dilution effect is effective method for reducing the NOx emission. In this study, an author investigated $N_2O$ reduction by using EGR on a direct injection diesel engine. The test engine was a 4-stroke diesel engine with maximum output of 12 kW at 2600rpm, and operating condition of the engine was a fixed load of 75%. The experimental oil was a blend-fuel that were adjusted with sulfur ratio of 3.5%, and EGR ratio of 0%, 10%, 20% and 30%. In conclusion, diesel fuel that contained 3.5% sulfur component increased $SO_2$ emission in exhaust gas, and increment of EGR ratio reduced NO emission. Moreover, $N_2O$ emission was decreased as over 50% at EGR ratio of 10% and reduced 100% at EGR ratio of 30% compared with $N_2O$ emission of 0% EGR ratio.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.10-21
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• 2006

The aim in this study is to develop the combined EGR system with a non-thermal plasma reactor for reducing exhaust emissions and improving fuel economy in turbo intercooler ECU common-rail diesel engines. At the first step, in this paper, the characteristics of performance and $NO_x{\cdot}THC$ emissions under four kinds of engine loads are experimentally investigated by using a four-cycle, four-cylinder, direct injection type, water-cooled turbo intercooler ECU common-rail diesel engine with a combined plasma exhaust gas recirculation(EGR) system operating at three kinds of engine speeds. The EGR system is used to reduce $NO_x$ emissions, and the non-thermal plasma reactor and turbo intercooler system are used to reduce THC emissions. The plasma system is a flat-to-flat type reactor operated by a plasma power supply. The fuel is sprayed by pilot and main injections at the variable injection timing between BTDC $15^{\circ}$ and ATDC $1^{\circ}$ according to experimental conditions. It is found that the specific fuel consumption rate with EGR is increased, but the fuel economy is better than that of mechanical injection type diesel engine as compared with the same output. Results show that $NO_x$ emissions are decreased, but THC emissions are increased, as the EGR rate is elevated. $NO_x$ and THC emissions are also slightly decreased as the applied electrical voltage of the non-thermal plasma reactor is elevated. Thus one can conclude that the influence of EGR in $NO_x$ and THC emissions is larger than that of the non-thermal plasma reactor, but THC emissions are greatly influenced by the non-thermal plasma reactor as the EGR rate is elevated.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.162-173
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• 1998

The high pressure common rail injection system offers a high potential for improving emmisions and performance characteristics in large direct diesel engines. High pressures in the common rail with electronic control allows the fuel quantity and injection timing to be optimized and controlled throughout a wide range of engine rpm and load conditions. In this study, high pressure supply pump, common rail, pipes, solenoid and control chamber, and nozzle were modeled in order to predict needle lift, rate of injection, and total injected fuel quantity. When the common rail pressure is raised up to 13.0 ㎫ and the targer injection duration is 1.0ms, the pressure drop in common rail is about 5.0㎫. The angle of effective pressurization is necessary to be optimized for the minimum pump drive torque and high pressure in common rail depending on the operating conditions. The characteristics of injection were also greatly influenced by the pressures in common rail, the areas of the inlet and exit orifice of the control chamber.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.78-85
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• 2007

Recently, diesel vehicles have been increased and their emission standards have been getting strict. The emission of diesel vehicles contains numerous dangerous compounds, especially particulate matters cause a serious environmental pollutant and affect to human health seriously. Thousands of studies have already reported that particulate matters are associated with respiratory and cardiovascular diseases, and death. Due to these, it is necessary to measure the soot concentration and soot particle size in laboratory flames or practical engines to recognize the soot formation, and develop the control strategies for soot emission. In this study, the characteristics of exhausted soot particle size and volume fraction from 2.0L CRDI diesel engine have been investigated as varying engine speed and load. Laser induced incandescence has been used to measure soot concentration. Time-resolved laser induced incandescence has been used to determine soot particle size in the engine. The soot volume fraction is increased as increasing engine load but soot volume fraction is decreased as increasing engine speed. The primary particle size is distributed about $35nm{\sim}60nm$ at each experimental conditions.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.555-561
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• 2005

This experimental study was executed to obtain basic data for actual engine operation using radical induced ignition method (RI) which can achieve emission reduction and high efficiency due to the rapid bulk combustion. In this study, a direct injection diesel engine was converted into SI type engine with a sparkplug. The modified SI type engine can be divided into two classes. One is the SI engine with a sparkplug only at the cylinder head, and the other is the SI engine with the sparkplug which is enveloped in a sub-chamber. Also, a basic experimental was conducted in order to investigate combustion mechanism of radical induced injection before the experiment execution for actual engine using the modified SI engine. The bulk combustion phenomenon of radical induced ignition method was analyzed from the basic experiment by using a constant volume chamber. Volume value of sub-chamber used in this experiment is approximately $0.2\%$ of one of the main combustion chamber. In this paper, combustion characteristics using radical induced injection method was compared with that of using spark ignition method according to change in the engine speed and equivalence ratio. As a result, in the case of the radical induced injection engine, the combustion duration and cycle variation were respectively reduced ranged from $\Phi$(equivalence ratio)=0.8 (lean mixture ratio) to $\Phi$=1.0 (stoichiometric ratio).