• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.868-876
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• 2014

The objective of this study is focused on the analyzing combustion, carbon monoxide and hydrocarbon emission characteristics of marine diesel oil, utilized for naval propulsion engine, with varying pre-post injection timing of an optically accessible single cylinder engine. And also the combustion process is analyzed by means of a high speed camera visualization. On the result of retarding pre-injection timing toward main injection timing, the mean effective pressure and maximum pressure of combustion chamber are increased; however, the heat release rate is decreased. Furthermore, the emission rates of carbon monoxide and hydrocarbon are reduced in this case. In hence, when a post-injection timing is advanced, the mean effective pressure and maximum pressure are increased, because the combustion has been performed under the high temperature and high pressurized environment during main injection time, and the emission rates of carbon monoxide and hydrocarbon are increased. From the experimental results, it considered that retarding of pre-injection timing affects to shorten the ignition delay of main injection clearly, and to raise the flame intensity comparing to the advanced state. The ignition delay during post-injection is not appeared at any post-injection time, but the flame intensity has been weakened gradually according to the retarding of post-injection timing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2573-2578
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• 2014

An experimental study was performed to investigate the characteristics of combustion pressure and exhaust emissions when the pilot injection timing and EGR rate were changed in a CRDI 4-cylinder diesel engine using bio-diesel blended fuel. The pilot injection timing and EGR rate have a significant impact on the combustion and emission characteristics of diesel engine. In this study, the pilot injection timing and EGR rate variation were conducted to 2000rpm of engine speed with fuel of bio-diesel blended rate 20%. In these experimental results, IMEP was shown maximum pressure at pilot injection timing BTDC$10^{\circ}$ combustion pressure and heat release rate were decreased in proportion to increase of EGR rate under the same pilot injection timing conditions. The NOx emission was decreased with increasing the EGR rate without influence on pilot injection timing. However, soot emission was reduced to a minimum at pilot injection timing BTDC$20^{\circ}$.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.911-917
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• 2015

The objective of this work focuses on the analysis of injection rate and macroscopic spray behavior characteristics with injection pressures as well as combustion and exhaust emission characteristics with injection timing and injection pressure by using a common rail single-cylinder diesel engine. The injection rate was measured by applying the Bosch method, and macroscopic spray behavior characteristics were analyzed with a constant-volume vessel and a high-speed camera. In addition, combustion and emission characteristics were analyzed in a common-rail single-cylinder diesel engine with precise control of fuel injection timing and pressure. For injection pressures of 30MPa and 50MPa, the injection rate was higher at 50 MPa, and the spray development (penetration) was also higher in the same elapsed time. The peak in-cylinder pressure and rate of heat release showed a tendency to decline as injection timing was delayed, and the peak in-cylinder pressure and rate of heat release were slightly higher for higher injection pressures. Higher injection pressures also reduced the mean effective pressure, while the indicated mean effective pressure and torque increased as injection timing was delayed to TDC. Nitrogen oxides had a peak level at injection timings of $BTDC20^{\circ}$(30MPa) and $BTDC15^{\circ}$(50MPa); carbon monoxide emissions were reduced by delaying injection timing from $BTDC30^{\circ}$.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.6
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• pp.80-88
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• 1989

본 연구에서는 양산중인 배기량 2.4Liter, 간접분사방식의 소형 디젤엔진에서 연소방식을 직접 분사방식으로 연소계를 재설계하여, 간접분사방식과 직접분사방식에 따른 엔진성능상의 차이점을 비교 평가하고, 아울러 직접분사방식에서 연소실 형상과 연소 관련 주요 인자들의 변경시 엔 진성은에 미치는 영향에 대해 고찰하였다. 직접분사방식 엔진은 간접분사방식 엔진에 대해 동 일출력, 동일 Smoke 수준인 경우 10-15%의 연료소비 저감의 효과가 있고, 이에 따라 연소관련 부품의 열부하면에서도 유리하였으나, 소음 및 NOx 배출은 증가하는 것으로 나타났다. 직접분사 연소방식에서는 Deep Bowl 연소실 형태의 Cylindrical Type 과 Re-entrant Type 에서 연비와 Smoke 등을 고려한 최적 분사시기가 Re-entrant Type 에서 4.deg. CA정도 늦었으며, 각기 최적 분사시기에서 스옴, NOx를 비교한 결과 Re-entrant Type이 더 우수하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.75-82
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• 2021

Low-temperature combustion (LTC) strategies, such as HCCI (Homogeneous Charge Compression Ignition), PCCI (Premixed Charge Compression Ignition), and RCCI (Reactivity Controlled Compression Ignition), have been developed to effectively reduce NOx and PM while increasing the thermal efficiency of diesel engines. Through numerical analysis, this study examined the effects of the injection timing and two-stage injection ratio of diesel fuel, a highly reactive fuel, on the performance and exhaust gas of RCCI engines using gasoline as the low reactive fuel and diesel as the highly reactive fuel. In the case of two-stage injection, combustion slows down if the first injection timing is too advanced. The combustion temperature decreases, resulting in lower combustion performance and an increase in HC and CO. The injection timing of approximately -60°ATDC is considered the optimal injection timing considering the combustion performance, exhaust gas, and maximum pressure rise rate. When the second injection timing was changed during the two-stage injection, considering the combustion performance, exhaust gas, and the maximum pressure increase rate, it was judged to be optimal around -30°ATDC. In the case of two-stage injection, the optimal result was obtained when the first injection amount was set to approximately 60%. Finally, a two-stage injection rather than a single injection was considered more effective on the combustion performance and exhaust gas.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.981-987
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• 2011

In this study, single cylinder engine experiment was carried out to investigate combustion characteristics spray guided direct injection spark ignition engine. In the result of engine experiment, it was shown that flammable window of injection timing was existed. The combustion efficiency increased with retarding injection timing, reaching a peak value, subsequent to decrease again. These results were likely due to the effect of ambient pressure on stratified-premixed mixture preparation. 150 bar injection pressure condition and retarded injection timing from the best combustion efficiency injection timing showed the highest IMEP value due to the advanced combustion phase of the maximum combustion efficiency condition. HC emission showed same trend of combustion efficiency, and smoke emission was increased as injection timing was retarded due to the increased locally rich area in the high ambient pressure. NOx emission showed decreasing trend as injection timing was retarded. This is likely due to the maximum in-cylinder temperature was decreased with retarded combustion phase.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.525-530
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• 2013

In this study, the generator engine of training ship M/S "HAE RIM" of Kunsan National University which is being operated for 20 years was used in the experiment. The experiment was carried out under the engine speed of 1200rpm, then the load was varied 30 kW intervals from 0 to 90 kW and the injection timing was varied $2^{\circ}$CA intervals from BTDC $19^{\circ}$ to $23^{\circ}$CA. In the case of advancing fuel injection timing from BTDC $21^{\circ}$CA to $23^{\circ}$CA, specific fuel consumption is decreased by 1.37%, NOx is increased by 11.59 %, soot is decreased by 23.5 % and $SO_2$ is decreased by 2.8 %. Accoring to the analysis of effects of fuel injection timing on combustion & exhaust emissions characteristics on an old marine diesel engine, it is proved that the optimum fuel injection timing is BTDC $23^{\circ}$ which is $2^{\circ}$ faster than that of original injection timing.

• Journal of Power System Engineering
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• v.15 no.1
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• pp.11-17
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• 2011

본 연구는 라디칼 착화(Radical Ignition이하 RI) 기술을 적용한 부실직분식 CNG(Compressed Natural Gas) 엔진의 구동특성에 관한 것이다. 실험엔진은 단기통 디젤엔진을 개조하여 사용하였으며, 이는 부실식 디젤엔진처럼 연소실이 주실과 부실로 나누어져 있다. 부실에 분사된 CNG는 스파크플러그로 점화하며, 부실로 부터의 연소가스가 주실 희박 혼합기를 시켜 구동하는 엔진이다. RI 기술은 연소속도를 향상시킬 수 있다. 본 연구는 주로 저부하 RI-CNG 엔진의 성능을 연구하였다. 연료분사기간은 9 ms, 공기과잉률은 1.0, 1.2, 1.4로 하였다. 연료분사시기는 엔진의 배가밸브가 닫히는 ATDC $20^{\circ}CA$ 부터 $120^{\circ}CA$ 사이로, $20^{\circ}CA$ 간격으로 지각시켜 가며 실험하였다. 본 연구는 연료분사시기 및 공기과잉률이 연소최고압력 ($P_{max}$), 연소최고압력시기(${\Theta}_{pmax}$), 도시평균유효압력(IMEP), 사이클 변동계수($COV_{imep}$), 연소속도에 미치는 양향 등을 구하고 분석하였다.

• Journal of Energy Engineering
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• v.27 no.2
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• pp.49-54
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• 2018

The common rail diesel engine used in this study is a remanufactured waste engine. The fuel injection timing of the waste engine is set to be suitable for the operating conditions of the vehicle. However, the engine of a generator is operated at a constant speed and mainly at partial load. Therefore, it is necessary to change the fuel injection timing suitable for the power generation engine, and the cost and the time required for such change must be minimized as much as possible. As a result of the analysis, it was confirmed that the fuel efficiency improves according to the fuel injection timing suitable for the engine for the generator, thereby increasing the performance and fuel efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.607-614
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• 2013

Nowadays, automotive manufacturers have developed various technologies to improve fuel economy and reduce harmful emissions. The ultra-lean direct injection engine is a promising technology because it has the advantage of improving thermal efficiency through the deliberate control of fuel and ignition. This study aims to investigate the development of a spray-guided-type lean-burn LPG direct injection engine through the redesign of the combustion system. This engine uses a central-injection-type cylinder head in which the injector is installed adjacent to the spark plug. Fuel consumption and combustion stability were estimated depending on the ignition timing and injection timing at various air-fuel ratios. The optimal injection timing and ignition timing were based on the best fuel consumption and combustion stability.