Numerical Investigation of Combustion and Emission With Different Diesel Surrogate Fuel by Hybrid Breakup Model

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Wenliang Qi ◽  
Pingjian Ming ◽  
Ming Jia ◽  
Ye Peng ◽  
Chen Liu
Keyword(s):  
Diesel Engine ◽  
Oxygen Concentration ◽  
Ignition Delay ◽  
Soot Formation ◽  
Combustion Engine ◽  
Flame Stabilization ◽  
Emission Characteristics ◽  
Air Mixing ◽  
Hybrid Breakup Model ◽  
Breakup Model

Injection flow dynamics plays a significant role in fuel spray; this process controls the fuel–air mixing, which in turn is critical for the combustion and emissions process in diesel engine. In the current study, an integrated spray, combustion, and emission numerical model is developed for diesel engine computations based on the general transport equation analysis (GTEA) code. The model is first applied to predict the effect of turbulence inside the nozzle, which is considered by the submodel of hybrid breakup model on diesel spray process. The results indicate that turbulence term enhances the rate of breakup, resulting in more new droplets and smaller droplet sizes, leading to high evaporation rate with more evaporated mass. The model is also applied to simulate combustion and soot formation process of diesel. The effects of ambient density, ambient temperature, oxygen concentration and reaction mechanism on ignition delay, flame lift-off length, and soot formation are analyzed and discussed. The results show that although higher ambient density and temperature reduce the ignition delay and cause the flame stabilization location to move upstream, this is not helpful for fuel–air mixing because it increases the soot level in the fuel jet. While higher oxygen concentration has negative effects on soot formation. In addition, the model is employed to simulate the combustion and emission characteristics of a low-temperature combustion engine. The overall agreement between the measurements and predictions of in-cylinder pressure, heat release, and emission characteristics are satisfactory.

scholarly journals Comparative Evaluation on Combustion and Emission Characteristics of a Diesel Engine Fueled with Crude Palm Oil Blends

2021 ◽  
Vol 11 (23) ◽  
pp. 11502
Author(s):  
Jun Cong Ge ◽  
Sam Ki Yoon ◽  
Jun Hee Song
Keyword(s):  
Diesel Engine ◽  
Vegetable Oil ◽  
Palm Oil ◽  
Combustion Engine ◽  
Engine Performance ◽  
Alternative Fuel ◽  
Emission Characteristics ◽  
Crude Palm Oil ◽  
Maximum Heat ◽  
Performance And Emission

Vegetable oil as an alternative fuel for diesel engine has attracted much attention all over the world, and it is also expected to achieve the goal of global carbon neutrality in the future. Although the product after transesterification, biodiesel, can greatly reduce the viscosity compared with vegetable oil, the high production cost is one of the reasons for restricting its extensive development. In addition, based on the current research on biodiesel in diesel engines, it has been almost thoroughly investigated. Therefore, in this study, crude palm oil (CPO) was directly used as an alternative fuel to be blended with commercial diesel. The combustion, engine performance and emissions were investigated on a 4-cylinder, turbocharged, common rail direct injection (CRDI) diesel engine fueled with different diesel-CPO blends according to various engine loads. The results show that adding CPO to diesel reduces the maximum in-cylinder pressure and maximum heat release rate to 30 Nm and 60 Nm. The most noteworthy finding is that the blend fuels reduce the emissions of hydrocarbons (HC), nitrogen oxides (NOx) and smoke, simultaneously. On the whole, diesel fuel blended with 30% CPO by volume is the best mixing ratio based on engine performance and emission characteristics.

A Computational Investigation of Fuel Chemical and Physical Properties Effects on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine

2017 ◽  
Author(s):  
Yu Zhang ◽  
Alexander Voice ◽  
Yuanjiang Pei ◽  
Michael Traver ◽  
David Cleary
Keyword(s):  
Diesel Engine ◽  
Physical Properties ◽  
Ignition Delay ◽  
Fuel Efficiency ◽  
Air Entrainment ◽  
Compression Ignition ◽  
Heavy Duty ◽  
Heavy Duty Diesel Engine ◽  
Air Mixing ◽  
Heavy Duty Diesel

Gasoline compression ignition (GCI) offers the potential to reduce criteria pollutants while achieving high fuel efficiency in heavy-duty diesel engines. This study aims to investigate the fuel chemical and physical properties effects on GCI operation in a heavy-duty diesel engine through closed-cycle, 3-D computational fluid dynamics (CFD) combustion simulations, investigating both mixing-controlled combustion (MCC) at 18.9 compression ratio (CR) and partially premixed combustion (PPC) at 17.3 CR. For this work, fuel chemical properties were studied in terms of the primary reference fuel (PRF) number (0–91) and the octane sensitivity (0–6) while using a fixed fuel physical surrogate. For the fuel physical properties effects investigation, PRF70 was used as the gas-phase chemical surrogate. Six physical properties were individually perturbed, varying from the gasoline to the diesel range. Combustion simulations were carried out at 1375 RPM and 10 bar brake mean effective pressure (BMEP). Reducing fuel reactivity (or increasing PRF number) was found to influence ignition delay time (IDT) more significantly for PPC than for MCC due to the lower charge temperature and higher EGR rate involved in the PPC mode. 0-D IDT calculations suggested that the fuel reactivity impact on IDT diminished with an increase in temperature. Moreover, higher reactivity gasolines exhibited stronger negative coefficient (NTC) behavior and their IDTs showed less sensitivity to temperature change. When exploring the octane sensitivity effect, ignition was found to occur in temperature conditions more relevant to the MON test. Therefore, increasing octane sensitivity (reducing MON) led to higher reactivity and shorter ignition delay. Under both MCC (TIVC: 385K) and PPC (TIVC: 353K), all six physical properties showed little meaningful impact on global combustion behavior, NOx and fuel efficiency. Among the physical properties investigated, only density showed a notable effect on soot emissions. Increasing density resulted in higher soot due to deteriorated air entrainment into the spray and the slower fuel-air mixing process. When further reducing the IVC temperature from 353K to 303K under PPC, the spray vaporization and fuel-air mixing were markedly slowed. Consequently, increasing the liquid fuel density created a more pronounced presence of fuel-rich and higher reactivity regions, thereby leading to an earlier onset of hot ignition and higher soot.

scholarly journals Combustion and Emission Characteristics of a Diesel Engine Operating with Varying Equivalence Ratio and Compression Ratio - A CFD Simulation

2020 ◽  
Vol 01 (03) ◽  
pp. 101-110
Author(s):  
Kazi Mostafijur Rahman ◽  
Zobair Ahmed
Keyword(s):  
Diesel Engine ◽  
Compression Ratio ◽  
Equivalence Ratio ◽  
Internal Combustion Engines ◽  
Cfd Simulation ◽  
Combustion Engine ◽  
Computational Cost ◽  
Injection Timing ◽  
Emission Characteristics ◽  
Engine Operation

The performance of diesel engine highly depends on atomization, vaporization and mixing of fuel with air. These factors are strongly influenced by various parameters e.g. injection pressure, injection timing, compression ratio, equivalence ratio, cylinder geometry, in cylinder air motion etc. In this study, a diesel engine has been investigated by employing a commercial CFD software (ANSYS Forte, version 18.1) especially developed for internal combustion engines (ICE) modeling; focusing primarily on the effects of equivalence ratio and compression ratio on combustion and emission characteristics. RNG k-ε model was employed as the turbulence model for analyzing the physical phenomena involved in the change of kinetic energy. In order to reduce the computational cost and time, a sector mesh of 45o angle with periodic boundary conditions applied at the periodic faces of the sector, is considered instead of using the whole engine geometry. Simulations are performed for a range of equivalence ratio varying from 0.6 to 1.2 and for three compression ratios namely, 15:1, 18:1 and 21:1. Results show that, improvement in combustion characteristics with higher compression ratio could be achieved for both lean and rich mixtures. Peak in-cylinder pressure and peak heat release nearer to TDC are achieved for compression ratio of 18:1 that could results in more engine torque. For compression ratio beyond 16:1, effects of fuel concentration on ignition delay is more pronounced. At lower compression ratio, in-cylinder temperature is not sufficiently high for atomization, vaporization, mixing of fuel with air, and preflame reactions to occur immediately after the fuel injection. NOx emission in diesel engine increases due to higher pressure and temperature inside the cylinder associated with relatively higher compression ratio. Rich mixture leads to more CO and unburnt hydrocarbon emission compared to lean mixture as result of incomplete combustion. Engine operation with too high compression ratio is detrimental as emission is a major concern.

A Computational Study on the Effects of Pre-Ignition Processes on Diesel Engine Combustion and Emissions

2011 ◽  
Author(s):  
S. K. Aggarwal ◽  
D. E. Longman
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Soot Formation ◽  
Premixed Combustion ◽  
Injection Timing ◽  
Emission Characteristics ◽  
Moderate Increase ◽  
Gas Temperature ◽  
Piston Bowl ◽  
Engine Combustion

There has been significant progress in reducing NOx and particulate emissions from diesel engines. However, many challenges remain particularly in view of the global energy issues and increasingly stringent emission regulations. Several recent efforts have focused on achieving low-temperature, premixed combustion for simultaneously reducing NOx and PM emissions, but without any detrimental effect on fuel consumption and energy density. Various strategies being explored include homogeneously charged compression ignition (HCCI), reducing flame temperature through excessive EGR, enhancing premixed combustion by controlling injection parameters, and promoting premixing by using early injection and low cetane number fuels. The present study is aimed at examining the effects of injection timing, initial gas temperature, and cylinder and piston wall temperatures on the spray processes, and thereby on the ignition, combustion and emission characteristics in a diesel engine. The reacting two-phase flow field in a 1.9L, 4-cylinder GM diesel engine is simulated using a CFD code ‘CONVERGE’, which employs an innovative cut-cell Cartesian method for grid generation, and a semi-detailed reaction mechanism for n-heptane combustion. A 51.430 sector with a single hole is considered to simulate the 7-hole common-rail injector. Results indicate that while the initial gas temperature does not affect the spray and combustion behavior qualitatively, it modifies combustion temperatures and thus NOx emissions noticeably. On the other hand, the piston and cylinder wall temperatures qualitatively influence the spray behavior and thereby the combustion and emission behavior. The injection timing has a strong influence on the spray and mixture formation processes, and thus on the combustion and emission characteristics. Delaying the start of injection (SOI) can lead to a significant reduction in NOx formation with only a moderate increase in soot formation. A detailed analysis of the spray and combustion processes indicated two main fuel consumption regions, one near the piston bowl wall and the other in the main spray near the injector. Fuel consumption in the first region mainly follows the conventional diesel combustion model involving rich premixed burning and diffusion burning, while that in the second region involves premixed combustion. As the SOI is delayed, the spray impingement on the piston bowl wall increases, causing more fuel consumption in the first region, which leads to reduction in NOx but increase in soot formation, indicating a tradeoff between NOx and soot emissions. However, with further delay in the SOI, the amount of fuel consumption in the first region increases significantly, while that in the main spray region involves lean premixed combustion. The net effect is a significant reduction in NOx with only a moderate increase in soot emission. Future studies will focus on the effects of modifying the level of premixing and the ignition delay on diesel engine combustion and emission.

260 Ignition delay and emission characteristics under low revolution of DI Diesel Engine

2010 ◽  
Vol 2010.59 (0) ◽  
pp. 119-120
Author(s):  
Yoshihiro HATAKEYAMA ◽  
Yasushi HAMAGUCHI ◽  
Tarou UNNO ◽  
Naoki UCHIYAMA ◽  
Susumu NODA
Keyword(s):  
Diesel Engine ◽  
Ignition Delay ◽  
Emission Characteristics ◽  
Di Diesel Engine

scholarly journals Effects of Fuel Injection Pressure on Combustion and Emission Characteristics under Low Speed Conditions in a Diesel Engine Fueled with Palm Oil Biodiesel

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3264 ◽  
Author(s):  
Ho Young Kim ◽  
Jun Cong Ge ◽  
Nag Jung Choi
Keyword(s):  
Diesel Engine ◽  
Palm Oil ◽  
Engine Speed ◽  
Fuel Injection ◽  
Soot Formation ◽  
Injection Pressure ◽  
Combustion Efficiency ◽  
Emission Characteristics ◽  
Fuel Injection Pressure ◽  
Palm Oil Biodiesel

In this study, the effect of injection pressure on combustion and emission characteristics was evaluated on a common rail direct injection diesel engine fueled with palm oil biodiesel. Recently, many studies have been conducted to utilize biodiesel produced from various sources to prevent environmental pollution and the depletion of petroleum resources. The oxygen content and high cetane number of biodiesel can reduce the production of exhaust pollutants by improving the combustion, but its high viscosity deteriorates the atomization of the injected fuel. Particularly at low engine speed conditions like idle, poor atomization and low airflow in the cylinder deteriorates the combustion efficiency. Increasing the fuel injection pressure is one of the effective methods to improve the atomization of biodiesel without mechanical modification of the current diesel engine. In this study, combustion characteristics and emission levels of pollutants were measured by varying the fuel injection pressure applying palm oil biodiesel. As a result, it was confirmed that increasing the injection pressure to apply palm oil biodiesel at low engine speed can reduce ignition delay and improve combustion efficiency so that nitrogen oxides (NOx) is increased but soot formation is reduced. Carbon monoxide (CO) and hydrocarbon (HC) are slightly reduced but these are increased again when using 100% palm oil biodiesel. The increased NOx due to increased injection pressure can be reduced by applying exhaust gas recirculation (EGR).

A comparison of spray and combustion characteristics of biodiesel (soy methyl ester, rapeseed methyl ester) with diesel

2018 ◽  
Vol 233 (7) ◽  
pp. 1712-1723
Author(s):  
Wenliang Qi ◽  
Pingjian Ming ◽  
Aisha Jilani ◽  
Haiyang Zhao ◽  
Ming Jia
Keyword(s):  
Methyl Ester ◽  
Physical Properties ◽  
Ignition Delay ◽  
Combustion Engine ◽  
Emission Characteristics ◽  
Low Temperature Combustion ◽  
Lift Off ◽  
Soy Methyl Ester ◽  
Lower Vapor Pressure ◽  
Surrogate Fuel

Physical properties are known to play a pivotal role in the different characteristics of spray, combustion, and emission between diesel and biodiesel. This paper reports the development and application of physical properties of diesel and biodiesel for fuel spray and combustion modeling under various conditions. An integrated numerical model has been developed based on the General Transport Equation Analysis code. The effect of turbulence in the nozzle was considered by the hybrid breakup model in the simulation, and the skeletal mechanism of diesel surrogate fuel and biodiesel surrogate fuel was used to simulate fuel oxidation. The results indicated that liquid lengths and droplet sizes are always higher for biodiesel because of its bigger surface tension and worse vaporization characteristics caused by higher critical temperature and lower vapor pressure. This phenomenon has strong influence on fuel evaporation process and results in slow evaporation rate, and this is not helpful for the mixture preparation process. The effects of ambient density, ambient temperature, and oxygen concentration on ignition delay and lift-off length of diesel and biodiesel are also analyzed and discussed. This analysis revealed that longer ignition delay usually results in longer lift-off length and biodiesel always has longer ignition delay and lift-off length compared to diesel. The flame propagation was observed to be similar for both fuels. In addition, diesel and biodiesel were employed to simulate the combustion and emission characteristics of a low-temperature combustion engine. The different combustion and NO x emission characteristics between diesel and biodiesel were observed, and the different physical properties may be the reason for these discrepancies.

scholarly journals Numerical Investigation of the Combustion Characteristics of an Internal Combustion Engine with Subcritical and Supercritical Fuel

2020 ◽  
Vol 10 (3) ◽  
pp. 862 ◽  
Author(s):  
Yukun Song ◽  
Zhaolei Zheng ◽  
Tao Peng ◽  
Zhanfeng Yang ◽  
Weidong Xiong ◽  
...  
Keyword(s):  
Internal Combustion Engine ◽  
Fuel Injection ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Pollutant Emissions ◽  
Subcritical State ◽  
Emission Characteristics ◽  
Local Concentration ◽  
No Emission ◽  
Air Mixing

The similarities and differences in the combustion and emission characteristics of supercritical- and subcritical-state fuel injection conditions of an internal combustion engine was clarified. The effects of fuel state on temperature, pressure, turbulent kinetic energy, heat release rate, NO, and soot in the cylinder during the operation of the internal combustion engine were simulated. Ignition occurred faster, and the peak temperature in the cylinder was achieved in shorter time under the supercritical-state fuel injection condition than under the subcritical condition. The cylinder pressures in both states peaked at the same time, but the value of pressure in the supercritical fuel state was larger than that in the subcritical state. Furthermore, the turbulence in the supercritical fuel state was more intense than that in the subcritical state. The intense turbulence was beneficial to fuel and air mixing. NO emission increased, and soot emission decreased in the supercritical fuel state. The results show that supercritical fuel can be fully mixed with air to reduce the local concentration area in the cylinder, improve the combustion performance of the engine, and greatly reduce pollutant emissions.

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