• 한국분무공학회지
• /
• 제28권2호
• /
• pp.55-61
• /
• 2023

Natural gas is a high-octane fuel that is effective in controlling knocking combustion. In addition, as a low-carbon fuel with a high hydrogen-carbon ratio, it emits less carbon dioxide and almost no particulate matter compared to conventional fossil fuels. Stoichiometric combustion engines equipped with a three-way catalyst are useful in various fields such as transportation and power generation because of their excellent exhaust emission reduction performance. However, stoichiometric combustion engines have a disadvantage of lower thermal efficiency compared to lean combustion engines. In this study, a combination of high compression ratio and Atkinson cycle was implemented in a 11 liter, 6-cylinder, spark-ignition engine to improve the thermal efficiency of the stoichiometric engine. As a result, pumping and friction losses were reduced and the operating range was extended with optimized Atkinson camshaft. Based on the exhaust gas limit temperature of 730℃, the maximum load and thermal efficiency were improved to BMEP 0.66 MPa and BTE 35.7% respectively.

• Journal of Advanced Marine Engineering and Technology
• /
• 제37권7호
• /
• pp.701-710
• /
• 2013

The purpose of this study is to investigate experimentally the effect of low purity methanol (LPM) on performance and smoke emission characteristics by using a four-cycle, four-cylinder, water-cooled, direct injection diesel engine with EGR system. The experiments are performed by the change of engine load in the engine load ranges of 25 to 100% with an interval of 25% under the constant engine speed of 2000 rpm. The LPM in the fuel blends contained 24.88% water by volume. The blended fuel ratios of diesel oil to LPM are maintained at 100/0, 95/5, 90/10 and 85/15% on the volume basis. In this paper, EGR rates are varied in three conditions of 0, 12.8 and 16.5%. The result shows that the brake power of a blended fuel with 15% LPM is reduced more 11.1% than that of the neat diesel oil at the full load with the EGR rate of 16.5%. At this condition, also, the brake specific fuel consumption (BSFC) is increased by 3.2%, the exhaust gas temperature is decreased by 10.7%, the smoke opacity is decreased by 18.7% and the brake thermal efficiency is increased by 7.3%. The sharp reduction of smoke opacity for a blended fuel with the LPM content of 15% at the full load without EGR system is observed by 68.4% compared with that of the neat diesel oil due to the high oxygen content of LPM.

• 한국자동차공학회논문집
• /
• 제10권5호
• /
• pp.45-57
• /
• 2002

In this paper, the results gained by applying many impingement models to the cylinder and flat plate were analyzed in comparison with the experimental data to study a spray/wall interaction phenomena. To begin with, the behavior of spray injected normal to the wall was analysed using three different impingement models ; Naber and Reitz model(NR model), Watkins and Wang model(WW model) and Park and Watkins model(PW model) in the present calculation. The results obtained from these models were compared with experimental data of Katsura et. al. The results indicated that PW model was in better agreement with experimental data than the NR and WW model. Also f3r spray injected at 30DEG , the result of three models were compared with experimental data of Fujimoto et. al. The results showed that m model overpredicted the penetration in the radial direction because this model was based on the inviscid jet analogy. WW model did not predicted the radius and height of the wall spray effectively. It might be thought that this discrepancy was due to the lack of consideration of spray film velocity occurred at impingement site. The result of PW model agrees with the experimental data as time goes on. In particular, a height of the spray droplets was predicted more closely to the experimental data than the other two models. The results of PW model in which the spray droplets were distributed densely around the edge of droplet distribution shaped in a circle had an agreement with the experimental data of Fujimoto et. al. Therefore, it was concluded that PW model performed better than M and WW model for prediction of spray behavior. The numerical calculation using PW model performed to the cylinder similar to the real shape of DI engine. The results showed that vortex strength near the wall in the cylinder was stronger than that in the case of flat plate. Contrary to the flat plat, an existence of the side wall in the cylinder caused the tangential velocity component to be reduced and the normal velocity component to be increased. The flow tends to rotate to the inside of cylinder going upward to the right side wall of cylinder gradually as time passes. Also, the results showed that as the spray angle increases, the gas velocity distribution and the tumble flow seemed to be formed widely.

• 한국산학기술학회논문지
• /
• 제21권7호
• /
• pp.692-698
• /
• 2020

본 논문은 커먼레일 단기통 디젤엔진에서 다단 파일럿 분할 분사 전략이 연소 및 배기가스 배출특성에 미치는 영향을 분석하는 데 초점을 두었다. 실린더 내부 최고 압력과 열발생률은 단일분사 조건에서 가장 높았으며, 파일럿 분사량이 균등하게 분할되어 분사 횟수가 증가할수록 감소하는 경향으로 나타났다. IMEP, 엔진 토크 및 연소 효율은 1단 파일럿 분사 조건에서 가장 낮게 나타나는 특성을 보였으나, 다단 파일럿 분할 분사 전략 적용 시 증가하는 경향으로 분석되었다. COV_IMEP는 연소 효율이 가장 낮은 1단 파일럿 분사 조건에서 가장 높았으며, 이는 연소 안정성이 낮다는 것을 의미한다. 배기가스 중 산소농도는 단일분사 조건에서 가장 낮았고, 이산화탄소는 가장 높게 배출되는 특성을 보였다. 다단 분할 분사 전략 적용 시 저온 연소과정이 진행되기 때문에 일산화탄소의 산화율은 낮아지게 되고 배출수준은 증가하는 특성을 보였다. 탄화수소는 국부적으로 농후한 혼합기가 형성되는 단일분사 조건에서 가장 높은 결과를 보였다. 질소산화물은 다단 파일럿 분할 분사 전략 중 3단 파일럿 분사 조건에서 55.6%까지 감소하는 특성을 보였다.

• Steel and Composite Structures
• /
• 제43권5호
• /
• pp.523-532
• /
• 2022

Turbocharger technology is one of the ways to survive in a competitive market that is facing increasing demand for fuel and improving the efficiency of vehicle engines. Turbocharging allows the engine to operate at close to its maximum power, thereby reducing the relative friction losses. One way to optimally understand the behavior of a turbocharger is to better understand the heat flow. In this paper, a 1.7 liter, 4 cylinder and 16 air valve gasoline engine turbocharger with compressible, viscous and 3D flow was investigated. The purpose of this paper is numerical investigation of the number of heat transfer in gasoline engines turbochargers under 3D flow and to examine the effect of different types of coatings on its performance; To do this, modeling of snail chamber and turbine blades in CATIA and simulation in ANSYS-FLUENT software have been used to compare the results of turbine with experimental results in both adiabatic and non-adiabatic (heat transfer) conditions. It should be noted that the turbine blades are modeled using multiple rotational coordinate methods. In the experimental section, we simulated our model without coating in two states of adiabatic and non-adiabatic. Then we matched our results with the experimental results to prove the validation of the model. Comparison of numerical and experimental results showed a difference of 8-10%, which indicates the accuracy and precision of numerical results. Also, in our studies, we concluded that the highest effective power of the turbocharged engine is achieved in the adiabatic state. We also used three types of SiO₂, Sic and Si₃N₄ ceramic coatings to investigate the effect of insulating coatings on turbine shells to prevent heat transfer. The results showed that SiO₂ has better results than the other two coatings due to its lower heat transfer coefficient.

• 한국자동차공학회논문집
• /
• 제17권5호
• /
• pp.61-66
• /
• 2009

An experimental investigation was conducted to analyze the effects of biodiesel-ethanol and biodiesel-diesel blended fuels on the characteristics of combustion and exhaust emissions, and size distributions of particulate matter in a single cylinder diesel engine. The three types of test fuel were biodiesel and two blended fuels which were added ethanol and diesel by 20 % volume based fraction into biodiesel, respectively. In this study, the injection rate, combustion pressure, exhaust emissions and size distributions of particulate matter were measured under various injection timings and injection pressures. The experimental results show that biodiesel-ethanol blended fuel has lengthened ignition delay and low combustion pressure in comparison with those of biodiesel and biodiesel-diesel blended fuel even if all fuels indicated similar trends of injection rate under equal injection pressures. In addition, the ethanol blended fuel significantly reduced nitrogen oxidies (NOx) and soot emissions. And then the size distribution of particulate matters shows that blended fuels restrain the formation of particles which were beyond the range of 150nm comparison with biodiesel fuel.

• 한국자동차공학회논문집
• /
• 제21권5호
• /
• pp.151-156
• /
• 2013

The experiment was done on cars travelling at the speeds of 20km/h, 60km/h and 100km/h using the performance testing mode for chassis dynamometer. In this experiment, the relativity between the secondary waveform coming from ignition coil and exhaust emissions were measured in case of cars with failures, in oxygen sensor, spark plugs. The following results obtained by analysis of the relativity between the secondary waveform and exhaust emissions. 1) When the oxygen sensor is failure, the average value of CO emission measured was 6.8 times higher than the standard CO emission value and the average value of HC emission measured was 2.3 times higher than the standard emission level. 2) When engine parts are in failure, more fuel enters the cylinder due to longer opening duration of injector, and it tended to make CO and HC emission values increase. 3) Combustion duration, the shape of flame propagation during spark line, and the size of the discharge-induced energy were the three main elements that directly cause variations in CO and HC emission values.

• 한국자동차공학회논문집
• /
• 제10권5호
• /
• pp.1-8
• /
• 2002

For gasoline engines, a three-way catalytic converter that has the maximum efficiency at stoichiometric air/fuel ratio is used to clean up the exhaust gas. So a precise air/fuel ratio control is necessary to maximize the catalytic conversion efficiency, For a transient condition, a fred-forward air/fuel ratio control method that estimates the air mass inducted into a cylinder is being used. In this study, a fuel injection map that makes an accurate air/fuel ratio control possible was constructed for the very same transient condition. For the same condition above, intake air model and fuel model were refined so that fuel injection values based on air mass through a throttle valve and intake manifold pressure are equal to the map values.

• Journal of Advanced Marine Engineering and Technology
• /
• 제16권1호
• /
• pp.35-46
• /
• 1992

In this study, we calculated gas flow fields and distribution of fuel droplet and mass fraction using the CONCHAS-SPRAY code which modified to execute in IBM PC and changed three important factors, injection rate pattern (BASIC, I, II, III), different bowl shape and spray type. Especially vortices which be influenced by fuel-air mixing process, evaporation and flame propagation are generated more strongly in the bowl-piston type combustion chamber than in the flat-piston type. As the spray type changes, it is found that conical type produced large and strong vortices and fuel droplets are effictively diffused into the entire combustion chamber. As the injection rate pattern changes I, II, III based on BASIC type, we confirmed that End-of-Injection Effect strongly influence on droplets life time.

• Archives of Metallurgy and Materials
• /
• 제64권3호
• /
• pp.841-844
• /
• 2019

Poppet valves made from high-frequency heat-treated SUH3 steel have insufficient durability, and scratches appear on the valve face in prolonged use. It is necessary to develop surface treatment technology with excellent durability to prevent the deterioration of engine performance. Therefore, a surface treatment technology with higher abrasion resistance than existing processes was developed by direct metal deposition to the face where the cylinder and valve are closed. In this study, heat pretreatment and deposition tests were performed on three materials to find suitable powders. In the performance evaluation, the hardness, friction coefficient, and wear rate were measured. Direct metal deposition using Inconel 738 and Stellite 6 powders without heat pretreatment were experimentally verified to have excellent durability.