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The exhaust gas recirculation (EGR) valve regulates the exhaust gas flow between the engine exhaust manifold and the inlet one. This allows the inlet air to warm up, improving fuel evaporation and reducing the combustion temperature of the charge. Such a valve reduces the number of harmful substances in the exhaust gases. The valve tends to stick when too much sediment builds on the walls of the exhaust system, especially during driving in urban conditions or when leaks in the vacuum or exhaust pipes occur. A faulty valve causes the engine to run unevenly at idle speed and under light loads. The defective EGR valve weakens the inlet manifold capacity, increases combustion, causes clogging of the particulate filter and damage to the lambda probe. Blocked EGR valve may lead to engine immobilization as a result of its computerized control system operations. A model of an EGR valve for a selected diesel engine was developed to determine velocity distribution of the load flowing in it for different values of the degree of valve opening and the volume of deposits on the valve walls. The volume of accumulated carbon deposits on the walls of the EGR valve was measured using a real engine. Based on the recorded mileage of the vehicle, the assumed average speed of the car and the driving style of the driver and the intensity of deposition of carbon particles on the walls was estimated. [ABSTRACT FROM AUTHOR]

Little is known about the effects of using emulsion fuel for extended operation hours. Emulsion fuels comprise of water, low grade diesel fuel (D2) and surfactant in the ratio of 10:89:1 v/v% (E10) and 20:79:1 v/v% (E20). The characteristics of carbon deposits from an engine after a run of 200 h were examined. The carbon deposit analysis performed were macroscopic/microscopic photographs, thermogravimetric analysis (TGA), metal element analysis (MEA) and Fourier transform infrared (FTIR). Increasing water in emulsion fuel decreased particulate matter (PM) and nitrogen oxides (NO x ) altogether. TGA results observed that carbon deposit of E10 engine differed from E20 and D2 engines in terms of its characteristics, which includes darker colour of carbon deposit and the higher volatile content, while the MEA results observed that the elemental metal concentration in the carbon deposit was reduced with increasing water content. The intensity of the spectrum from C H group for the carbon deposit E10 engine was higher compared to carbon deposit D2 and E20 engine respectively due to a complete combustion. Therefore, it was observed that 10% or less water content delivered better fuel consumption, emissions, and carbon deposit. [ABSTRACT FROM AUTHOR]

The emissions from the Compression ignition (CI) engines introduce toxicity to the atmosphere. The undesirable carbon deposits from these engines are realized in the nearby static or dynamic systems such as vehicles, inhabitants, etc. The objective of this research work is to improve the performance and emission characteristics of a diesel engine in the modified re-entrant combustion chamber using a diesel and Jatropha methyl ester blend (J20) at three different injection pressures. From the literature, it is revealed that the shape of the combustion chamber and the fuel injection pressure have an impact on the performance and emission parameters of the CI engine. In this work, a re-entrant combustion chamber with three different fuel injection pressures (200, 220 and 240 bars) has been used in the place of the conventional hemispherical combustion chamber for diesel and J20. From the experimental results, it is found that the re-entrant chamber improves the brake thermal efficiency of diesel and J20 in all the tested conditions. It is also found that the 20% blend of Jatropha methyl ester showed 4% improvement in the brake thermal efficiency in the re-entrant chamber at the maximum injection pressure. Environmental safety directly relates to the reduction in the undesirable effects on both living and non-living things. Currently environmental pollution is of major concern. Even with the stringent emission norms new methods are required to reduce the harmful effects from automobiles. The toxicity of carbon monoxide (CO) is well known. In the re-entrant combustion chamber, the amount of CO emission is reduced by 26% when compared with the conventional fuel operation of the engine. Moreover, the amount of smoke is reduced by 24% and hydrocarbons (HC) emission by 24%. Thus, the modified re-entrant combustion chamber reduces harmful pollutants such as unburned HC and CO as well as toxic smoke emissions. [ABSTRACT FROM AUTHOR]

For large-scale and reliable implementation of biodiesel in transportation engines, its effects on engine wear and engine durability upon prolonged usage needs to be experimentally investigated. Therefore effects of 20% Karanja biodiesel blend (KOME20) on engine wear and durability was studied vis-à-vis mineral diesel in 250 h long endurance test on a direct injection compression ignition (DICI) engine. Visual inspection of engine components for deposits indicted higher carbon deposits on piston top, cylinder head and injector tip for biodiesel fuelled engine. Relatively lower wear of valves, pistons, piston rings, liners and small end bearings of the connecting rods was observed for biodiesel fuelled engine. Wear of big end bearing of the connecting rods, main bearings and crank pins was found to be higher for biodiesel fuelled engine. Surface texture of cylinder liners remained in acceptable condition after the endurance test for mineral diesel as well as Karanja biodiesel blend. Despite higher carbon deposits and higher wear of some vital engine components, no operational problems were observed during the long-term endurance test for the biodiesel fueled engine. [ABSTRACT FROM AUTHOR]

The cycle-by-cycle fluctuations in peak pressure of combustion in a CI engine were studied for lower and higher blends of diesel and ester, and water-in-ester emulsions, at four injection timings and three injection pressures using coefficient of variation. The sunflower ester-diesel blends are found to have lower cycle-by-cycle fluctuations than pongemia ester-diesel blends. The fluctuations are found to be higher than that of diesel for higher blend proportions of ester. The water-in-ester emulsion show higher cycle-by-cycle fluctuations than that of ester-diesel blends. In most cases, the Brake specific energy consumption is also found to be higher where the coefficient of variation has higher values. [ABSTRACT FROM AUTHOR]

A multi-pulse injection strategy for premixed charge compression ignition (PCCI) combustion was investigated in a four-valve, direct-injection diesel engine by a computational fluid dynamics (CFD) simulation using KIVA-3V code coupled with detailed chemistry. The effects of fuel splitting proportion, injection timing, spray angles, and injection velocity were examined. The mixing process and formation of soot and nitrogen oxide (NOx) emissions were investigated as the focus of the research. The results show that the fuel splitting proportion and the injection timing impacted the combustion and emissions significantly due to the considerable changes of the mixing process and fuel distribution in the cylinder. While the spray, inclusion angle and injection velocity at the injector exit, can be adjusted to improve mixing, combustion and emissions, appropriate injection timing and fuel splitting proportion must be jointly considered for optimum combustion performance. [ABSTRACT FROM AUTHOR]

Biodiesel is biodegradable and nontoxic, and it significantly reduces toxic and other emissions when burned as a fuel. The advantages of biodiesel as diesel fuel are its portability, ready availability, renewability, higher combustion efficiency, non-toxicity, higher flash point, and lower sulfur and aromatic content, higher cetane number, and higher biodegradability. The major disadvantages of biodiesel are its higher viscosity, lower energy content, higher cloud point and pour point, higher nitrogen oxide (NOx) emissions, lower engine speed and power, injector coking, engine compatibility, high price, and greater engine wear. The technical disadvantages of biodiesel/fossil diesel blends include problems with fuel freezing in cold weather, reduced energy density, and degradation of fuel under storage for prolonged periods. The sources of biodiesel are vegetable oils and fats. The direct use of vegetable oils and/or oil blends is generally considered to be unsatisfactory and impractical for both direct injection and indirect type diesel engines because of their high viscosities and low volatilities injector coking and trumpet formation on the injectors, higher level of carbon deposits, oil ring sticking, and thickening and gelling of the engine lubricant oil, acid composition. Biodiesel is obtained by transesterifying triglycerides with methanol. A popular variation of the batch transesterification process which needs high alcohol/acid ratio (several separation problems and high corrosivity and toxicity) is the use of continuous stirred tank reactors in series. This continuous process is heterogeneous and is based on reactive distillation. The key factor is the selection of the right and effective solid catalyst which leads to reduction of energy consumption and investments at all. [ABSTRACT FROM AUTHOR]

Straight vegetable oil utilization as a diesel engine fuel has the advantages of eliminating the energy, time, and cost involved in biodiesel production. Since straight vegetable oils have quite high viscosity compared with mineral diesel, they have to be modified to bring their combustion-related properties closer to mineral diesel. In this experimental study, a heat exchanger was designed and used to utilize the waste heat of exhaust gases for reducing the viscosity of Karanja oil by preheating. Carbon deposits, wear of vital engine components, and various effects of utilizing preheated Karanja oil on lubricating oil were analysed during a long-term endurance test executed for 512 h. Carbon deposits on various critical parts of the power cell were analysed by visual inspection. For pistons, the piston merit rating was determined. The effect on a lubricating oil because of heated Karanja oil vis-à-vis mineral diesel was evaluated by comparing the densities, viscosities, flash points, carbon residues, ash contents, copper corrosion effect and pentane, benzene insolubility measurements at intervals of every 128 h for 512 h. The wear of the cylinder liner, piston rings, gudgeon pin, and small- and big-end bearings for a Karanja-oil-fuelled engine were also measured and compared vis-à-vis mineral diesel-fuelled engine. [ABSTRACT FROM AUTHOR]

Abstract: The formation processes of carbonaceous deposits in the first piston ring grooves of direct injection diesel engines have been studied. Deposits generated during engine tests were analysed by SEM/EDX, thermogravimetric analysis, pyrolysis/gas chromatography/mass spectrometry, and FT-IR spectroscopy. These analyses showed that the deposits, with a structure of cracked varnishes, mainly resulted from the degradation of lubricants. Their state strongly depends on the severity of the tests, which resulted in the formation of two kinds of deposits, termed as ‘oily’ and ‘dry’, according to their content of volatile organic matters. Then, to better understand the deposit formation process, a thermo-oxidative degradation of the lubricating oil was carried out in a tubular furnace, while varying temperature, duration of the test, and adding metallic elements to simulate the engine wear. The consumption of antioxidant additives and the lubricant carbonization were highlighted. Temperature level was identified as the most influential parameter during the lubricant degradation process. The presence of metallic elements appeared to act as a catalyst by speeding up the degradation when the tests duration was increased. [Copyright &y& Elsevier]

The carbon deposit formation process of a small diesel engine operated using rapeseed methyl ester (RME) and RME blended diesel fuel was examined. The amount of carbon deposits accumulated on the fuel injector nozzle was measured at 2-hour intervals over a 30-hour consecutive operation period. The microstructure of the carbon deposits was observed using scanning electron microscopy (SEM). The effect of fuel properties, such as the distillation property, viscosity and particulate formation tendency, on carbon deposit formation was also investigated. [ABSTRACT FROM AUTHOR]

The startability of diesel engines degrades as the ambient temperature falls, in particular, to the borderline or lower temperature. The essential cause is the deterioration of in-cylinder combustion resulting from worsening of combustion conditions. A membrane-based oxygen-enriched intake air (OEA) method is proposed to improve in-cylinder combustion and then to reduce exhaust emissions during the start-up process. This paper investigates the effects of OEA on startability and exhaust emission behaviour during the engine start-up. The experiments were carried out on a direct-injection diesel engine. A membrane-based oxygen-enrichment system was constructed to supply the test engine with intake air containing 21 vol %, 23 vol %, 25 vol %, and 27 vol % oxygen respectively. The in-cylinder pressure, instantaneous engine speed, and time-resolved engine-out emissions were recorded and compared for the OEA and the baseline methods (ambient air (AA), 21 vol % oxygen). The results show that, at the high intake air temperature (26 °C), the engine could start smoothly. When the intake air temperature fell to the borderline temperature (5 °C), the startability significantly degraded, in-cylinder incomplete combustion was evident during the initial stage of start-up, and the start-up time increased. With OEA at 5 °C, the startability was markedly improved, and the engine experienced fewer cycles than those at the same intake air temperature with AA before it reached idle operation. With OEA, the engine-out hydrocarbon, CO, and smoke emissions throughout the whole start-up process were all reduced considerably, but NOx emissions evidently increased. [ABSTRACT FROM AUTHOR]