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.

scholarly journals Influence of Chemical Composite Additive on Combustion and Emission Characteristics of a Diesel Engine using Waste Plastic Oil as Fuel and Modified Piston Bowl

2018 ◽  
Vol 34 (6) ◽  
pp. 2806-2813
Author(s):  
Pappula Bridjesh ◽  
Pitchaipillai Periyasamy ◽  
Narayanan Kannaiyan Geetha
Keyword(s):  
Experimental Investigation ◽  
Diesel Engine ◽  
Combustion Chamber ◽  
Emission Characteristics ◽  
Soy Lecithin ◽  
Physiochemical Properties ◽  
Waste Plastic ◽  
Piston Bowl ◽  
Waste Plastic Oil ◽  
Engine Combustion

This experimental investigation is an endeavour to substitute diesel with WPO as fuel on a diesel engine. Enhancing the physiochemical properties of WPO or with hardware modifications on the engine, the performance of engine could not be improved up to the mark. The physiochemical properties of WPO are enhanced by the use of composite additive, which is a mixture of soy lecithin and 2-ethylhexyl nitrate and to improve the in-cylinder air motion; subsequently to increase the swirl and turbulence, standard hemispherical combustion chamber is modified to toroidal spherical grooves combustion chamber. The results of combined effect of modifying the combustion chamber and addition of composite additive suggest that improvements in engine-out emissions can be obtained from current diesel engines by enhancing physiochemical properties of fuel and matching geometry of combustion chamber. Engine combustion and emission characteristics under various loads for various fuels under test are as well studied.

scholarly journals Application of CFD, Taguchi Method, and ANOVA Technique to Optimize Combustion and Emissions in a Light Duty Diesel Engine

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Senlin Xiao ◽  
Wanchen Sun ◽  
Jiakun Du ◽  
Guoliang Li
Keyword(s):  
Diesel Engine ◽  
Taguchi Method ◽  
Fuel Consumption ◽  
Soot Formation ◽  
Dynamics Simulation ◽  
Injection Timing ◽  
Light Duty ◽  
Study Results ◽  
Main Injection ◽  
Pilot Fuel

Some previous research results have shown that EGR (exhaust gas recirculation) rate, pilot fuel quantity, and main injection timing closely associated with engine emissions and fuel consumption. In order to understand the combined effect of EGR rate, pilot fuel quantity, and main injection timing on theNOx(oxides of nitrogen), soot, and ISFC (indicated specific fuel consumption), in this study, CFD (computational fluid dynamics) simulation together with the Taguchi method and the ANOVA (analysis of variance) technique was applied as an effective research tool. At first, simulation model on combustion and emissions of a light duty diesel engine at original baseline condition was developed and the model was validated by test. At last, a confirmation experiment with the best combination of factors and levels was implemented. The study results indicated that EGR is the most influencing factor onNOx. In case of soot emission and ISFC, the greatest influence parameter is main injection timing. For all objectives, pilot fuel quantity is an insignificant factor. Furthermore, the engine with optimized combination reduces by at least 70% forNOx, 20% in soot formation, and 1% for ISFC, in contrast to original baseline engine.

Understanding the soot reduction associated with injection timing variation in a small-bore diesel engine

2019 ◽  
pp. 146808741986805 ◽  
Author(s):  
Lingzhe Rao ◽  
Yilong Zhang ◽  
Sanghoon Kook ◽  
Kenneth S Kim ◽  
Chol-Bum Kweon
Keyword(s):  
Diesel Engine ◽  
Fuel Injection ◽  
Soot Formation ◽  
Soot Oxidation ◽  
Laser Induced Fluorescence ◽  
Injection Timing ◽  
Gas Temperature ◽  
Planar Laser ◽  
Laser Induced Incandescence ◽  
Ambient Gas

This study shows the in-cylinder soot reduction mechanism associated with injection timing variation in a small-bore optical diesel engine. For the three selected injection timings, three optical-/laser-based imaging diagnostics were performed to show the development of high-temperature reaction and soot within the cylinder, which include OH* chemiluminescence, planar laser–induced fluorescence of hydroxyl and planar laser–induced incandescence. In addition, detailed soot morphology analysis was conducted using thermophoresis-based soot particle sampling from two locations within the piston bowl, and the subsequent analysis of transmission electron microscope (TEM) images of the sampled soot aggregates was also conducted. The results suggest that when fuel injection timing is varied, ambient gas temperature makes a predominant effect on soot formation and oxidation. This is primarily combustion phasing effect as the advanced fuel injection moved the start of combustion closer to the top dead centre, and therefore, soot formation and oxidation occurred at elevated ambient gas temperature. There was an overall development pattern of in-cylinder soot consistently found for three injection timings of this study. The planar laser–induced incandescence images showed that a few small soot pockets first appear around the jet axis, which promptly grow into large soot regions behind the head of the flame marked planar laser–induced fluorescence of hydroxyl. The soot signals disappear due to significant oxidation induced by surrounding OH radicals. When the injection timing is advanced, the soot formation becomes higher as indicated by higher total laser–induced incandescence coverage, increased sampled particle counts and larger and more stretched soot aggregate structures. However, soot oxidation is also enhanced under this elevated ambient temperature environment. At the most advanced injection timing of this study, the enhanced soot oxidation outperformed the increased soot formation with both peak laser–induced incandescence signal coverage and late-cycle coverage showing lower values than those of more retarded injection timings.

scholarly journals Effect of Nitromethane and Jatropha Biodiesel on the Combustion, Performance and Emission Characteristics of Diesel Engine

2021 ◽  
Vol 18 (3) ◽  
pp. 8986-8997
Author(s):  
Alireza Valipour Berenjestanaki ◽  
Dilawar Hussain
Keyword(s):  
Diesel Engine ◽  
Biodiesel Production ◽  
Injection Timing ◽  
Emission Characteristics ◽  
Engine Test ◽  
Gas Temperature ◽  
Performance And Emission ◽  
Combustion Performance ◽  
Blended Fuels ◽  
Load Conditions

The experimental work reported has been carried out in two parts; Jatropha biodiesel production and engine test. The engine test has been carried out on a direct injection, single-cylinder, water-cooled stationary diesel engine. Several diesel fuel blends which contain 10% and 20% by volume of JBD and 1% and 3% nitromethane were prepared. The effects of these blends on the combustion, performance, and emission characteristics of diesel engine were studied. The tests were performed under constant speed and varying load conditions without altering injection timing. A maximum increase of 11.73%, 3.2 % and 7.68 % in the brake thermal efficiency, the brake specific fuel consumption and exhaust gas temperature were achieved respectively for 20% Jatropha biodiesel and 3% nitromethane at full engine load. Compared to the pure diesel operation, the peak in-cylinder pressure of blended fuels was lower at the full load conditions. Also, the maximum net heat release rate of blended fuels was lower than that of diesel at all loading conditions. In regards to the engine emissions, the results showed that the blended fuels reduced carbon monoxide at 18.6–28.9% and unburned hydrocarbon of 7.5-24.2%, while increased the emission of nitrogen oxides at 6.9–14.3% and carbon dioxide at 4.3-10.5%.

Two-Stroke Marine Diesel Engine Variable Injection Timing System Performance Evaluation and Optimum Setting for Minimum Fuel Consumption at Acceptable NOx Levels

2014 ◽  
Author(s):  
Dimitrios T. Hountalas ◽  
Spiridon Raptotasios ◽  
Antonis Antonopoulos ◽  
Stavros Daniolos ◽  
Iosif Dolaptzis ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Engine Performance ◽  
Operating Conditions ◽  
Specific Fuel Consumption ◽  
Injection Timing ◽  
Nox Emissions ◽  
Pressure Measurements ◽  
Cylinder Pressure ◽  
Start Of Injection

Currently the most promising solution for marine propulsion is the two-stroke low-speed diesel engine. Start of Injection (SOI) is of significant importance for these engines due to its effect on firing pressure and specific fuel consumption. Therefore these engines are usually equipped with Variable Injection Timing (VIT) systems for variation of SOI with load. Proper operation of these systems is essential for both safe engine operation and performance since they are also used to control peak firing pressure. However, it is rather difficult to evaluate the operation of VIT system and determine the required rack settings for a specific SOI angle without using experimental techniques, which are extremely expensive and time consuming. For this reason in the present work it is examined the use of on-board monitoring and diagnosis techniques to overcome this difficulty. The application is conducted on a commercial vessel equipped with a two-stroke engine from which cylinder pressure measurements were acquired. From the processing of measurements acquired at various operating conditions it is determined the relation between VIT rack position and start of injection angle. This is used to evaluate the VIT system condition and determine the required settings to achieve the desired SOI angle. After VIT system tuning, new measurements were acquired from the processing of which results were derived for various operating parameters, i.e. brake power, specific fuel consumption, heat release rate, start of combustion etc. From the comparative evaluation of results before and after VIT adjustment it is revealed an improvement of specific fuel consumption while firing pressure remains within limits. It is thus revealed that the proposed method has the potential to overcome the disadvantages of purely experimental trial and error methods and that its use can result to fuel saving with minimum effort and time. To evaluate the corresponding effect on NOx emissions, as required by Marpol Annex-VI regulation a theoretical investigation is conducted using a multi-zone combustion model. Shop-test and NOx-file data are used to evaluate its ability to predict engine performance and NOx emissions before conducting the investigation. Moreover, the results derived from the on-board cylinder pressure measurements, after VIT system tuning, are used to evaluate the model’s ability to predict the effect of SOI variation on engine performance. Then the simulation model is applied to estimate the impact of SOI advance on NOx emissions. As revealed NOx emissions remain within limits despite the SOI variation (increase).

A Computational Investigation of Piston Bowl Geometry for a Large Bore Two-Cycle Diesel Engine

2011 ◽  
Author(s):  
Jonathan Dolak ◽  
Deep Bandyopadhyay
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Simulation Software ◽  
Spray Angle ◽  
Tier 2 ◽  
Piston Bowl ◽  
Cylinder Test ◽  
Advanced Combustion ◽  
Combustion Simulation ◽  
Reduce Emissions

The objective of this research was to optimize an Electro-Motive Diesel (EMD) large-bore, two-cycle diesel engine (710 cubic inches of displacement per cylinder) at high load to minimize soot, nitrogen oxide (NOx) and fuel consumption. The variables considered were the number of spray-hole nozzles per injector, including spray angle and piston bowl geometry, for a range of injection pressures. Analytical simulations were conducted for a calibrated EMD 710 Tier 2 engine and a few of the top-performing cases were studied in detail. CONVERGE™, a commercially available, advanced combustion simulation software was used in this analysis. A surface deforming tool, Sculptor®, was used to obtain various piston bowl geometries. MiniTab® was utilized for statistical analysis. Results show that optimal combinations of injection variables and piston bowl shape exist to simultaneously reduce emissions and fuel consumption compared to Tier 2 EMD 710 engines. These configurations will be further tested in a single-cylinder test cell and presented later. This investigation shows the importance of bowl geometry and spray targeting on emissions and fuel consumption for large-bore, two-stroke engines with high power density.

scholarly journals Effect of Partially Premixed Fuel on Performance and Emission Characteristics of Compression Ignition (CI) Engine

2019 ◽  
Vol 8 (4S2) ◽  
pp. 163-166
Keyword(s):  
Diesel Engine ◽  
New Technology ◽  
Control Unit ◽  
Injection Timing ◽  
Emission Characteristics ◽  
Compression Ignition ◽  
Fuel Injector ◽  
Si Engine ◽  
Performance And Emission ◽  
Partially Premixed

In this world, the population is increased and the number of vehicles increased. Not only population the pollution is increased lot by vehicles in the world harmful pollutant is realized from the vehicles like CO, HC, NOx and smoke particulates. It is inevitable to find some new technology, which increases the better performance and emission characteristics. Partially premixed compression ignition (PCCI) is the best technology for the reducing of harmful pollution in the vehicle, which uses the diesel as fuel it, gives the advantages of both CI and SI engine. This paper investigates the performance and emission characteristics of partially premixed diesel engine. Diesel engine has two injectors of port fuel injector (PFI) and direct injector (DI) to inject the fuel in different timing and electrical control unit (ECU) passes the power to PFI; it can control the injection timing and increases the fuel content from the fuel pump. The main aim in this paper is studied is effect of partially premixed ratio, performance of engine and emission characteristics of diesel engine

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