An experimental investigation on a DI diesel engine using waste plastic oil with exhaust gas recirculation

Environmental degradation and depleting oil reserves are matters of great concern around the globe. Developing countries like India depend heavily on oil import of about 125 Mt per annum (7:1 diesel/gasoline). Diesel being the main transport fuel in India, finding a suitable alternative to diesel is an urgent need. In this context, waste plastic solid is currently receiving renewed interest. Waste plastic oil is suitable for compression ignition engines and more attention is focused in India because of its potential to generate large-scale employment and relatively low environmental degradation. The present investigation was to study the effect of cooled exhaust gas recirculation (EGR) on four stroke, single cylinder, direct injection (DI) diesel engine using 100% waste plastic oil. Experimental results showed higher oxides of nitrogen emissions when fueled with waste plastic oil without EGR. NO_x emissions were reduced when the engine was operated with cooled EGR. The EGR level was optimized as 20% based on significant reduction in NO_x emissions, minimum possible smoke, CO, HC emissions and comparable brake thermal efficiency. Smoke emissions of waste plastic oil were higher at all loads. Combustion parameters were found to be comparable with and without EGR. Compression ignition engines run on waste plastic oil are found to emit higher oxides of nitrogen.     

Biodiesel engine performance and emissions in low temperature combustion

Engine performance and emission comparisons were made between the use of soy, Canola and yellow grease derived B100 biodiesel fuels and an ultra-low sulphur diesel fuel in the high load engine operating conditions. Compared to the diesel fuel engine-out emissions of nitrogen oxides (NO_x), a high-cetane number (CN) biodiesel fuel produced comparable NO_x while the biodiesel with a CN similar to the diesel fuel produced relatively higher NO_x at a fixed start of injection. The soot, carbon monoxide and un-burnt hydrocarbon emissions were generally lower for the biodiesel-fuelled engine. Exhaust gas recirculation (EGR) was then extensively applied to initiate low temperature combustion (LTC) mode at medium and low load conditions. An intake throttling valve was implemented to increase the differential pressure between the intake and exhaust in order to increase and enhance the EGR. Simultaneous reduction of NO_x and soot was achieved when the ignition delay was prolonged by more than 50% from the case with 0% EGR at low load conditions. Furthermore, a preliminary ignition delay correlation under the influence of EGR at steady-state conditions was developed. The correlation considered the fuel CN and oxygen concentrations in the intake air and fuel. The research intends to achieve simultaneous reductions of NO_x and soot emissions in modern production diesel engines when biodiesel is applied.     

Effects of ethyl tert-butyl ether addition to diesel fuel on characteristics of combustion and exhaust emissions of diesel engines

The effects of ethyl tert-butyl ether (ETBE) addition to diesel fuel on the characteristics of combustion and exhaust emissions of a common rail direct injection diesel engine with high rates of cooled exhaust gas recirculation (EGR) were investigated. Test fuels were prepared by blending 0, 10, 20, 30 and 40 vol% ETBE to a commercial diesel fuel. Increasing ETBE fraction in the fuel helps to suppress the smoke emission increasing with EGR, but a too high fraction of ETBE leads to misfiring at higher EGR rates. While the combustion noise and NO_x emissions increase with increases in ETBE fraction at relatively low EGR rates, they can be suppressed to low levels by increasing EGR. Though there are no significant increases in THC and CO emissions due to ETBE addition to diesel fuel in a wide range of EGR rates, the ETBE blended fuel results in higher aldehyde emissions than the pure diesel fuel at relatively low EGR rates. With the 30% ETBE blended fuel, the operating load range of smokeless, ultra-low NO_x (<0.5 g/kWi h), and efficient diesel combustion with high rates of cooled EGR is extended to higher loads than with the pure diesel fuel.     

Diesel and rapeseed methyl ester (RME) pilot fuels for hydrogen and natural gas dual-fuel combustion in compression-ignition engines

This paper presents experimental results of rapeseed methyl ester (RME) and diesel fuel used separately as pilot fuels for dual-fuel compression-ignition (CI) engine operation with hydrogen gas and natural gas (the two gaseous fuels are tested separately). During hydrogen dual-fuel operation with both pilot fuels, thermal efficiencies are generally maintained. Hydrogen dual-fuel CI engine operation with both pilot fuels increases NO_x emissions, while smoke, unburnt HC and CO levels remain relatively unchanged compared with normal CI engine operation. During hydrogen dual-fuel operation with both pilot fuels, high flame propagation speeds in addition to slightly increased ignition delay result in higher pressure-rise rates, increased emissions of NO_x and peak pressure values compared with normal CI engine operation. During natural gas dual-fuel operation with both pilot fuels, comparatively higher unburnt HC and CO emissions are recorded compared with normal CI engine operation at low and intermediate engine loads which are due to lower combustion efficiencies and correspond to lower thermal efficiencies. This could be due to the pilot fuel failing to ignite the natural gas-air charge on a significant scale. During dual-fuel operation with both gaseous fuels, an increased overall hydrogen-carbon ratio lowers CO₂ emissions compared with normal engine operation. Power output (in terms of brake mean effective pressure, BMEP) as well as maximum engine speed achieved are also limited. This results from a reduced gaseous fuel induction capability in the intake manifold, in addition to engine stability issues (i.e. abnormal combustion). During all engine operating modes, diesel pilot fuel and RME pilot fuel performed closely in terms of exhaust emissions. Overall, CI engines can operate in the dual-fuel mode reasonably successfully with minimal modifications. However, increased NO_x emissions (with hydrogen use) and incomplete combustion at low and intermediate loads (with natural gas use) are concerns; while port gaseous fuel induction limits power output at high speeds.     

Effect of dimethoxy-methane and exhaust gas recirculation on combustion and emission characteristics of a direct injection diesel engine

The effect of fuel constituents and exhaust gas recirculation (EGR) on combustion characteristics, fuel efficiency and emissions of a direct injection diesel engine fueled with diesel-dimethoxymethane (DMM) blends was investigated experimentally. Three diesel-DMM blended fuels containing 20%, 30% and 50% by volume fraction of DMM, corresponding to 8.5%, 12.7% and 21.1% by mass of oxygen in the blends, were used. By the use of DMM, it is observed that CO and smoke emissions as well as the total number and mass concentration of particulate reduce significantly, while HC emissions and particulate number with lower geometric mean diameters (D_i < 0.039 μm) increase slightly. For each fuel, there is an increase of ignition delay whereas a decrease of cylinder pressure and heat release rate in the premixed combustion phase when the diesel engine was operated with EGR system. The brake thermal efficiency fluctuates at small EGR ratio, while decreases with the further increase of EGR ratio. With an increase of EGR ratio, NO_x emission is reduced at the cost of increased smoke, HC and CO emissions as well as the total number and mass of particulates for each fuel.     

Real-time and robust estimation of biodiesel blends

Biodiesel as a renewable alternative fuel produces lower exhaust emissions with the exception of nitrogen oxides (NO_x) when compared to the conventional diesel fuel. Reducing nitrogen oxides produced from engines running on biodiesel requires proper engine controller adaptations that are linked to the specifics of the fuel blend. Therefore, online estimation of fuel blend is a critical step in allowing diesel engines to maintain performance while simultaneously meeting emission requirements when operating on biodiesel blends. Presented in this paper are three different model-based biodiesel blend estimation strategies using: (i) crankshaft torsionals, (ii) NO_x emissions measurement from the exhaust stream, and (iii) oxygen content measurement of the exhaust stream using a wide-band UEGO sensor. Each approach is investigated in terms of the accuracy and robustness to sensor errors. A sensitivity analysis is conducted for each method to quantify robustness of the proposed fuel blend estimation methods.     

Performance and emission characteristics of an CI engine fueled with diesel–biodiesel–bioethanol blends

The paper presents the experimental results obtained concerning performances and pollution of a diesel engine fueled with diesel–biodiesel–ethanol blends compared with diesel fuel in laboratory tests. The main properties of the researched fuels are presented within this paper, in comparison with classical diesel fuel (chemical composition, density, kinematic viscosity, cold filter plugging point, flash point). Engines’ performances were evaluated by determining the brake specific fuel consumption and brake thermal efficiency. For pollution evaluation the emissions of CO, CO₂, NO_x, HC and smoke have been measured. An increasing of brake specific fuel consumption has been observed, especially at lower engines’ loads, with maximum 32.4%, reducing engine brake thermal efficiency with maximum 21.7%. CO emissions decrease, especially at high loads with maximum 59%, on the basis of CO₂ increased emissions. NO_x emissions slightly increase, especially at partial and high loads, meanwhile HC and smoke emissions decrease in all engines’ load cycles.     

Comparison of emissions of a direct injection diesel engine operating on biodiesel with emulsified and fumigated methanol

Biodiesel is an alternative fuel for internal combustion engines. It can reduce carbon monoxide (CO), hydrocarbon (HC) and particulate matter (PM) emissions, compared with diesel fuel, but there is also an increase in nitrogen oxides (NO_x) emission. This study is aimed to compare the effect of applying a biodiesel with either 10% blended methanol or 10% fumigation methanol. The biodiesel used in this study was converted from waste cooking oil. Experiments were performed on a 4-cylinder naturally aspirated direct injection diesel engine operating at a constant speed of 1800 rev/min with five different engine loads. The results indicate a reduction of CO₂, NO_x, and particulate mass emissions and a reduction in mean particle diameter, in both cases, compared with diesel fuel. It is of interest to compare the two modes of fueling with methanol in combination with biodiesel. For the blended mode, there is a slightly higher brake thermal efficiency at low engine load while the fumigation mode gives slightly higher brake thermal efficiency at medium and high engine loads. In the fumigation mode, an extra fuel injection control system is required, and there is also an increase in CO, HC and NO₂ (nitrogen dioxide) and particulate emissions in the engine exhaust, which are disadvantages compared with the blended mode.     

Determination of performance and exhaust emissions properties of B75 in a CI engine application

In this study, performance and exhaust emissions of biodiesel in a compression ignition engine was experimentally investigated. Therefore, biodiesel has been made by transesterification from cotton seed oil and then it was mixed with diesel fuel by 25% volumetrically, called here as B75 fuel. B75 fuel was tested, as alternative fuel, in a single cylinder, four strokes, and air-cooled diesel engine. The effect of B75 and diesel fuels on the engine power, engine torque and break specific fuel consumption were clarified by the performance tests. The influences of B75 fuel on CO, HC, NOx, Smoke opacity, CO₂, and O₂ emissions were investigated by emission tests. The engine torque and power, for B75 fuel, were lower than that of diesel fuel in range of 2-3%. However, for the B75, specific fuel consumption was higher than that of diesel fuel by approximately 3%. CO₂, CO, HC, smoke opacity and NO_x emissions of B75 fuel were lower than that of diesel fuel. The experimental results showed that B75 fuel can be substituted for the diesel fuel without any modifications in diesel engines.     

Performance, emission and combustion evaluation of soapnut oil-diesel blends in a compression ignition engine

Soapnut (Sapindus mukorossi) oil, a nonedible straight vegetable oil was blended with petroleum diesel in various proportions to evaluate the performance and emission characteristics of a single cylinder direct injection constant speed diesel engine. Diesel and soapnut oil (10%, 20%, 30% and 40%) fuel blends were used to conduct short-term engine performance and emission tests at varying loads in terms of 25% load increments from no load to full loads. Tests were carried out for engine operation and engine performance parameters such as fuel consumption, brake thermal efficiency, and exhaust emissions (smoke, CO, UBHC, NO_x, and O₂) were recorded. Among the blends SNO 10 has shown a better performance with respect to BTE and BSEC. All blends have shown higher HC emissions after about 75% load. SNO 10 and SNO 20 showed lower CO emissions at full load. NO_x emission for all blends was lower and SNO 40 blend achieved a 35% reduction in NO_x emission. SNO 10% has an overall better performance with regards to both engine performance and emission characteristics.     

Characterization of Soot Deposition and Particle Nucleation in Exhaust Gas Recirculation Coolers

Cooled exhaust gas recirculation (EGR) is used to control engine out NO_x (oxides of nitrogen) emissions from modern diesel engines by re-circulating a portion of the exhaust gases into the intake manifold of an engine after cooling it through a heat exchanger commonly referred to as an EGR cooler. However, EGR cooler fouling due to presence of soot particles and hydrocarbons (HC) in engine exhaust leads to a decrease in cooler efficiency and increased pressure drop across the cooler. This can adversely affect the combustion process, engine durability, and emissions. In this study, a multicylinder diesel engine was used to produce a range of engine out HC and soot concentrations to investigate soot deposition and particle nucleation in an EGR cooler. A portion of the engine exhaust was passed through an EGR cooler, while particle size and HC concentration measurements were made at the cooler inlet and outlet. Tests were conducted over a range of EGR cooler coolant temperatures and engine out soot and HC concentrations to determine the impact on the nucleation and accumulation modes of the exhaust particle size distributions. A reduction in the accumulation mode particle concentration at the EGR cooler outlet was observed for high soot concentrations indicating soot deposition within the EGR cooler. As the EGR coolant temperature was reduced, the outlet accumulation mode particle concentration was reduced further, indicating increased soot deposition in the cooler due to increased thermophoresis. There were no signs of diffusiophoresis due to HC diffusion within the cooler over the range of conditions used in the study. A significant increase in outlet nucleation mode particle concentration was observed for the low soot concentrations. This mode increased with either increasing HC concentration or decreasing coolant temperature, indicating the saturation ratio (SR) dependence of the nucleation mode formation. However, as the soot concentration was increased, the nucleation mode disappeared because of HC adsorption onto the increased soot surface area.

Copyright 2012 American Association for Aerosol Research     

An analysis for effect of cetane number on exhaust emissions from engine with the neural network

Decoupling cetane number from the other compositions and properties of diesel fuel, the individual effect of cetane number on the exhaust emissions from an engine may be researched. This paper has presented a back-propagation neural network model predicting the exhaust emissions from an engine with the inputs of total cetane number, base cetane number and cetane improver, total cetane number and nitrogen content in the diesel fuel; as well as the output of the exhaust emissions of hydrocarbon (HC), carbon oxide (CO), particulate matter (PM) and nitrogen oxide (NO_x). An optimal design has been completed for the number of hidden layers, the number of hidden neurons, the activation function, and the goal errors, along with the initial weights and biases in the back-propagation neural network model. HC, CO, PM and NO_x have been predicted with the model, the effects of cetane improver and nitrogen content on them have also been analyzed, and better results have been achieved.     

Experimental investigation of mineral diesel fuel, GTL fuel, RME and neat soybean and rapeseed oil combustion in a heavy duty on-road engine with exhaust gas aftertreatment

The effects of mineral diesel fuel, gas-to-liquid fuel, rapeseed methyl ester, neat soybean and neat rapeseed oil on injection, combustion, efficiency and pollutant emissions have been studied on a compression ignition heavy duty engine operated near full load and equipped with a combined exhaust gas aftertreatment system (oxidation catalyst, particle filter, selective catalytic NO_x reduction). In a first step, the engine calibration was kept constant for all fuels which led to differences in engine torque for the different fuels. In a second step, the injection duration was modified so that all fuels led to the same engine torque. In a third step, the engine was recalibrated in order to keep the NO_x emissions at an equal level for all fuels (injection pressure, injection timing, EGR rate). The experiments show that the critical NO_x emissions were higher (even behind the exhaust gas aftertreatment systems) for oxygenated fuels in case of the engine not being recalibrated for the fuel. GTL and the oxygenated fuels show lower emissions for some pollutants and higher efficiency after recalibration to equal NO_x levels.     

Combustion and emissions of a DI diesel engine fuelled with diesel-oxygenate blends

Combustion and emissions of a DI diesel engine fuelled with diesel-oxygenate blends were investigated. The results show that there exist the different behaviors in the combustion between the diesel-diglyme blends and the other five diesel-oxygenate blends as the diglyme has the higher cetane number than that of diesel fuel while the other five oxygenates have the lower cetane number than that of diesel fuel. The smoke concentration decreases regardless of the types of oxygenate additives, and the smoke decreases with the increase of the oxygen mass fraction in the blends without increasing the NO_x and engine thermal efficiency. The reduction of smoke is strongly related to the oxygen-content of blends. CO and HC concentrations decrease with the increase of oxygen mass fraction in the blends. Unlike conventional diesel engines fueled with pure diesel fuel, engine operating on the diesel-oxygenate blends presents a flat NO_x/Smoke tradeoff curve versus oxygen mass fraction.     

Optimization of soy-biodiesel combustion in a modern diesel engine

As global petroleum demand continues to increase, alternative fuel vehicles are becoming the focus of increasing attention. Biodiesel has emerged as an attractive alternative fuel option due to its domestic availability from renewable sources, its relative physical and chemical similarities to conventional diesel fuel, and its miscibility with conventional diesel. Biodiesel combustion in modern diesel engines does, however, generally result in higher fuel consumption and nitrogen oxide (NO_x) emissions compared to diesel combustion due to fuel property differences including calorific value and oxygen content. The purpose of this study is to determine the optimal engine decision-making for 100% soy-based biodiesel to accommodate fuel property differences via modulation of air-fuel ratio (AFR), exhaust gas recirculation (EGR) fraction, fuel rail pressure, and start of main fuel injection pulse at over 150 different random combinations, each at four very different operating locations. Applying the nominal diesel settings to biodiesel combustion resulted in increases in NO_x at three of the four locations (up to 44%) and fuel consumption (11-20%) over the nominal diesel levels accompanied by substantial reductions in particulate matter (over 80%). The biodiesel optimal settings were defined as the parameter settings that produced comparable or lower NO_x, particulate matter (PM), and peak rate of change of in-cylinder pressure (peak dP/dt, a metric for noise) with respect to nominal diesel levels, while minimizing brake specific fuel consumption (BSFC). At most of the operating locations, the optimal engine decision-making was clearly shifted to lower AFRs and higher EGR fractions in order to reduce the observed increases in NO_x at the nominal settings, and to more advanced timings in order to mitigate the observed increases in fuel consumption at the nominal settings. These optimal parameter combinations for biodiesel were able to reduce NO_x and noise levels below nominal diesel levels while largely maintaining the substantial PM reductions. These parameter combinations, however, had little (maximum 4% reduction) or no net impact on reducing the biodiesel fuel consumption penalty.     

Katalysatoren für den Umweltschutz

Catalysts for environmental protection. The main emitters of anthropogenic air pollution are internal combustion engines, power plants, and production processes. Components of exhaust gases which are regarded as pollutants are hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NO_x), sulfur dioxide (SO₂), and dust. Three main types of catalyst are understood to improve the environment; namely automotive emission control, NO_x abatement and oxidation. To reduce the pollutants HC, CO, and NO_x in automobile exhaust gas, three-way catalysts are currently applied. The reduction of particle emissions in diesel exhaust gas is achieved by diesel filters and oxidation catalysts. Pollutants from power plants are mainly the inorganic components NO_x and SO₂. In the SCR process, NO_x is catalytically reduced to nitrogen and water. The DESONOX process is suited for the simultaneous catalytic abatement of NO_x and SO_x. Exhaust gases from production processes in many areas require after-treatment. Therefore catalyst formulations depend on process parameters and exhaust gas components. This overview presents and explains catalyst types, design, mode of operation, and processes.     

Combustion, performance and emission characteristics of a DI diesel engine fueled with ethanol-biodiesel blends

In this study, Euro V diesel fuel, biodiesel, and ethanol-biodiesel blends (BE) were tested in a 4-cylinder direct-injection diesel engine to investigate the combustion, performance and emission characteristics of the engine under five engine loads at the maximum torque engine speed of 1800 rpm. The results indicate that when compared with biodiesel, the combustion characteristics of ethanol-biodiesel blends changed; the engine performance has improved slightly with 5% ethanol in biodiesel (BE5). In comparison with Euro V diesel fuel, the biodiesel and BE blends have higher brake thermal efficiency. On the whole, compared with Euro V diesel fuel, the BE blends could lead to reduction of both NO_x and particulate emissions of the diesel engine. The effectiveness of NO_x and particulate reductions increases with increasing ethanol in the blends. With high percentage of ethanol in the BE blends, the HC, CO emissions could increase. But the use of BE5 could reduce the HC and CO emissions as well.     

Engine performance and emission characteristics of a three-phase emulsion of biodiesel produced by peroxidation

Biodiesel, which is produced from vegetable oils, animal fats or used cooking oils, can be used as an alternative fuel for diesel engines. The high oxygen content of biodiesel not only enhances its burning efficiency, but also generally promotes the formation of more nitrogen oxides (NO_x) during the burning process. Fuel emulsification and the use of NO_x inhibitor agents in fuel are considered to be effective in reducing NO_x emissions. In the study reported herein, soybean oil was used as raw oil to produce biodiesel by transesterification reaction accompanied by peroxidation to further improve the fuel properties of the biodiesel, which was water washed and distilled to remove un-reacted methanol, water, and other impurities. The biodiesel product was then emulsified with distilled water and emulsifying surfactant by a high-speed mechanical homogenizer to produce a three-phase oil-droplets-in-water-droplets-in-oil (i.e. O/W/O) biodiesel emulsion and an O/W/O emulsion that contained aqueous ammonia, which is a NO_x inhibitor agent. A four-stroke diesel engine, in combination with an eddy-current dynamometer, was used to investigate the engine performance and emission characteristics of the biodiesel, the O/W/O biodiesel emulsion, the O/W/O biodiesel emulsion that contained aqueous ammonia, and ASTM No. 2D diesel. The experimental results show that the O/W/O emulsion has the lowest carbon dioxide (CO₂) emissions, exhaust gas temperature, and heating value, and the largest brake specific fuel consumption, fuel consumption rate, and kinematic viscosity of the four tested fuels. The increase of engine speed causes the increase of equivalence ratio, exhaust gas temperature, CO₂ emissions, fuel consumption rate, and brake specific fuel consumption, but a decrease of NO_x emissions. Moreover, the existence of aqueous ammonia in the O/W/O biodiesel emulsion curtails NO_x formation, thus resulting in the lowest NO_x emissions among the four tested fuels in burning the O/W/O biodiesel emulsion that contained aqueous ammonia.     

Effect of variation in LPG composition on emissions and performance in a dual fuel diesel engine

This paper investigates the effect of variation in LPG composition on emissions and performance characteristics in a dual fuel engine run on diesel fuel and five gaseous fuel of LPG with different composition. To quantify the best LPG composition for dual fuel operation especially in order to improve the exhaust emissions quality while maintaining high thermal efficiency comparable to a conventional diesel engine, a two-cylinder, naturally aspirated, four-stroke, DI diesel engine converted to run as pilot-injected dual fuel engine. The tests and data collection were performed under various conditions of load at constant engine speed. From the results, it is observed that the exhaust emissions and fuel conversion efficiency of the dual fuel engine are found to be affected when different LPG composition is used as higher butane content lead to lower NO_x levels while higher propane content reduces CO levels. Fuel #3 (70% propane, 30% butane) with mass fraction 40% substitution of the diesel fuel was the best LPG composition in the dual fuel operation except that at part loads. Also, tests were made for fuel #3-diesel blend in the dual fuel operation at part loads to improve the engine performances and exhaust emissions by using the Exhaust Gas Recirculation (EGR) method.     

Improving performances of a lean burn cogeneration biogas engine equipped with combustion prechambers

Tests of the unscavenged prechamber ignition system on a 150 kW cogeneration engine fed with biogas are presented. The objective was to reach at least 36% in fuel conversion efficiency with exhaust gas emissions lower than the Swiss regulations limits (NO_x, CO: 400 and 650 mg/Nm³, 5% O₂ and 0% relative humidity) without exhaust gas after treatment. With a compression ratio of 12.0, it is shown that 40% of CO₂ induces a CO reduction of 15% and an HC reduction of 8% for the same NO_x emissions, but with a slight reduction of 1% in fuel conversion efficiency compared to pure natural gas. The results for the compression ratio of 13.3, a spark timing of 8 ca_BTDC, an air factor λ of 1.57 and 39.5% CO₂ are a fuel conversion efficiency of 37.7% while keeping the NO_x and CO emissions below the Swiss limit. This study shows that using unscavenged prechambers in biogas engines is particularly beneficial to reach interesting conversion efficiencies with low emissions. It allows a significant boost in energy conversion from biogas compared to existing systems.