Reduction In Smoke Emissions Research Articles

Influence of water emulsified diesel & oxygen-enriched air on diesel engine NO-smoke emissions and combustion characteristics

AbstractOxygen-enriched combustion of diesel engine can reduce smoke emission and improve thermal efficiency, but also lead to the increase of NO emission. In this research, experiments were conducted on a turbo-charged direct injection diesel engine under the two conditions of 2000 rpm and 180 Nm equivalent power (57% of the original max load at 2000 rpm) as well as 100% load of this speed. The combination of intake oxygen enrichment and water emulsified diesel was used to improve the NO-smoke emissions without serious penalty in brake specific fuel consumption (BSFC). The results showed that when engine load was 180 Nm with the conditions of 0%–20% water emulsion ratio and 21%–21.5% intake oxygen concentration, as well as under the condition of 100% load with 10%–15% water emulsion ratio and 21%–22% intake oxygen concentration, the NO-Smoke emissions were lower than that of original engine and BSFC was not exceeding 5% of the original engine by optimized combination of water emulsion ratio and oxygen concentration.

Influence of EGR and oxygen-enriched air on diesel engine NO–Smoke emission and combustion characteristic

The oxygen enriched combustion of diesel engines can reduce smoke emission and increase engine thermal efficiency; however it can also lead to an increase of NO emission. In this paper, experiment was conducted on a turbocharged direct injection diesel engine, and oxygen-enriched and EGR techniques were used to produce lower NO–Smoke emission than the unmodified engine under the same fuel supply rate curve and fuel supply quantity. The specific fuel consumption and the power loss were lower than 5% compared to the unmodified engine. The effect of oxygen enrichment on the particle size distribution was tested and analyzed. The results revealed that the optimal NO–Smoke emission can be achieved at these conditions: 1600rpm of engine speed, full load, 30–40% EGR rate and 21.5–22.5% of intake oxygen density; 2200rpm of engine speed, full load, 20–45% EGR rate and 22–24% of intake oxygen density. The result of particle size distribution tests revealed that oxygen enriched combustion can effectively suppress the diameter growth of particles and lead to fewer large particles with a diameter larger than 100nm emissions; however it did lead to an increase of 15nm small particles. A reduced n-heptane kinetic model was also developed in this research which contained NO and PAHs formation mechanisms, and the model was coupled with a CFD model to simulate the oxygen-enriched combustion of a diesel engine. The calculated results demonstrated that the coupled model can accurately predict ignition time and the change of in-cylinder pressure when the combined oxygen-enriched and EGR technique was used. The computed NO change with in-cylinder oxygen density agreed well with experiment results, and the computed result of the growth experience of PAHs showed that oxygen-enriched combustion can effectively suppress HACA reaction during PAHs formation, which leads to the reduction of large molecule PAHs, and this result agreed well with the observed situation that particle size diameter decreases with the increase of intake oxygen density.

Effects of ethanol–diesel–biodiesel blends on combustion and emissions in premixed low temperature combustion

In this study, the effect of ethanol on combustion and emissions in premixed low temperature combustion (LTC) was investigated in a four cylinders heavy-duty diesel engine. The biodiesel was used as an additive to prevent the stratification of ethanol and diesel blends. The premixed LTC is achieved by the medium level of EGR and the prolonged ignition delay. Compared with diesel fuel, ethanol–diesel–biodiesel blends have lower NOx emissions due to lower combustion temperature, resulting from the higher latent heat of vaporization. Unfortunately, the lower combustion temperature also leads to the higher HC and CO emissions. Smoke emissions for ethanol blends decrease obviously because of higher oxygen content and longer ignition delay. The oxygen in ethanol also has a favorable impact on the reduction of smoke emissions, which is obvious in high loads. Thus, the upper load limit of LTC mode is extended. Compared with diesel fuel, 20 vol.% ethanol in diesel and biodiesel blends (BDE20) has lower NOx and smoke emissions and higher brake thermal efficiency in LTC.

Burning behaviors of collision-merged water/diesel, methanol/diesel, and water + methanol/diesel droplets

The merging and combustion characteristics of droplets composed of water and diesel, methanol and diesel, and water+methanol (W+M) and diesel were investigated. For the merged droplets of water and diesel, the water droplets inserted into diesel in all test conditions. While only diesel vaporized during the burning period, the remaining water droplet terminated by either flash vaporization into water mist or extinguished as residue. For methanol and diesel, instead, the methanol droplet tended to enclose the diesel droplet when its size was relatively larger than that of diesel and adhered with the diesel droplet when its size was sufficiently small. As methanol content increased beyond ∼50%, the flame became almost invisible after ignition with a delayed, regular explosion occurring after the appearance of a yellowish flame. For those with lower methanol content, an explosion occurred shortly after the ignition with branched flame or slightly delayed with a flame ball. As for W+M and diesel, most of the merged droplets were in adhesive-like mode at the room temperature. However, the initial burning exhibited an insertive-like burning mode, with the yellowish flame as that of pure diesel or merged water and diesel droplet. The burning ended with droplet extinction, flash vaporization, or explosion at different mixing ratios of pre-mixture and diesel content. Practically, water and diesel emulsions could reduce smoke emissions from burning. Our results have shown that by adding methanol into water or alone and mixed with diesel can have superior burning behavior than water/diesel emulsions. Therefore, the potential of separate injections of water, methanol or W+M mixture, and oil in opposed jet arrangements, in direct-injection engines, is suggested.

Effects of fuel constituents and injection timing on combustion and emission characteristics of a compression-ignition engine fueled with diesel-DMM blends

The effects of DMM addition and fuel injection timing on combustion characteristics, fuel efficiency and emissions of a compression-ignition engine fueled with diesel-dimethoxymethane (DMM) blends are investigated experimentally in this study. Three diesel-DMM blends with 15%, 30% and 50% volume fraction of DMM addition respectively are tested at different engine loads and engine speeds. Not only HC, CO, smoke and NOx emissions, but also particle-size distribution and number concentration in exhaust gas have been measured. According to the measured in-cylinder pressure history, the in-cylinder combustion process is promoted by using diesel-DMM blends and can be further improved with early fuel injection. We find that using diesel-DMM blends can improve thermal efficiency and is beneficial to the reduction of smoke and CO emissions as well as particle number of both nanoparticles and ultrafine particles in exhaust gas with slightly increased NOx emission. Both fuel efficiency and thermal efficiency are improved with advanced fuel injection timing. Advancing fuel injection timing reduces smoke emission and particle number at the cost of increased NOx emission. We find that early fuel injection can either increase or decrease nanoparticles in exhaust gas. When advancing fuel injection from 20 to 23 CA BTDC, the number of nanoparticles is reduced; the further advanced fuel injection timing from 23 to 26 CA BTDC produces more nanoparticles. In this study, the lowest nanoparticle number in exhaust gas was achieved by injecting diesel-DMM blends with 50% DMM addition at 23 CA BTDC.

Performance and emissions of a dual fuel operated diesel engine

Vegetable oil and its esters (biodiesel) are the renewable alternative fuels that can be used as a substitute for diesel in the diesel engines. The vegetable oil fuelled diesel engine results in lower efficiency and higher smoke emission. Hence in this work, an attempt has been made to use inedible and under utilised mahua oil (MO) as a substitute for diesel by fumigating liquefied petroleum gas (LPG) along with the air. A single cylinder diesel engine was modified to work in dual fuel mode by suitable retrofitting. The MO was injected into the cylinder using a fuel pump and LPG was fumigated along with the air. In MO + LPG dual fuel mode, 9% increase in brake thermal efficiency and 35% reduction in smoke emission of the engine were observed as compared to the sole fuel mode with MO. Also, the engine performance characteristics in MO + LPG dual fuel mode are close to sole fuel mode with diesel. From this work, it is concluded that LPG can be fumigated along with the air to increase the performance of MO fuelled agricultural diesel engine.

An Experimental Investigation on the Potential of Hydrogen in the Reduction of the Emission Characteristics of an Existing Four-Stroke Single-Cylinder Diesel Engine Operating Under EGR

The present work attempts to explore the emission characteristics of an existing single-cylinder four-stroke compression-ignition engine operated in dual-fuel mode with hydrogen as an alternative fuel. Experimental investigation was carried out with the engine being subjected to different loads at a predefined flow rate of hydrogen induction. The emission characteristics revealed a 71% and a 40.5% reduction of CO2 emissions at 20% and 80% load, respectively, for non-EGR (exhaust gas recirculation) hydrogen enrichment. In CO emissions, non-EGR hydrogen enrichment registered a 69.5% and a 64.3% reduction at 20% and 40% load, respectively. Smoke emissions saw a 61.5% and a 64.3% reduction during non-EGR hydrogen enrichment at 20% and 40% load, respectively. Hydrocarbon (HC) emissions were reduced by 80% and 60.9% as compared with diesel operation at 20% and 60% loads, respectively. Hydrogen enrichment operations without EGR were penalized, however, with an increase of 79.3% and 81.3% in NOx at 40% and 60% load, respectively, as compared with diesel operation. EGR (hot and cold) technique has been implemented in the present work to reduce NOx emissions. In the present study, hydrogen enrichment overcome the inherent penalization of NOx–smoke tradeoff common under such EGR operation and was able to simultaneously decrease NOx emissions and smoke emissions effectively. As an indicator, 20% cooled EGR registered a decrease of 9.2% and 12.3% in NOx emissions at 60% and 80% load, respectively, as compared with diesel operation and simultaneously reduced smoke emissions by 10% and 8.3% as compared with diesel operation.

Analysis of Performance and Emissions of an Automotive Euro 5 Diesel Engine Fuelled with B30 from RME and JME

The effects of using a B30 blend of ultra low sulphur diesel and two different Fatty Acid Methyl Esters (FAME) obtained from both Rapeseed Methyl Ester (RME) and Jatropha Methyl Ester (JME) in a Euro 5 small displacement passenger car diesel engine on both full load performance and part load emissions have been evaluated in this paper. In particular the effects on engine torque were firstly analyzed, for both a standard ECU calibration (i.e. without any special tuning for the different fuel characteristics) and for a specifically adjusted ECU calibration obtained by properly increasing the injected fuel quantities to compensate for the lower LHV of the B30: with the latter, the same torque levels measured under diesel operation could be observed with the B30 blend too, with lower smoke levels, thus highlighting the potential for maintaining the same level of performance while achieving substantial emissions benefits. Moreover, the effects of the two different 30% vol. blends on brake specific fuel consumption and on engine-out exhaust emissions (CO2, CO, HC, NOx and smoke) were also evaluated at 6 different part load operating conditions, representative of the New European Driving Cycle. Both standard engine calibration (change of the accelerator pedal position) and specifically adjusted engine calibration (adjustment of the energizing time of main injection) were evaluated for part load operating conditions, highlighting a 4% average rise of fuel consumption, on a mass basis, at same fuel conversion efficiency and CO2 emissions. A noticeable increase of CO and HC emissions at low load could also be noticed, along with a significant NOx emissions decrease when using a specifically adjusted engine calibration, and a considerable smoke emission reduction

The influence of n-butanol/diesel fuel blends utilization on a small diesel engine performance and emissions

Nitrogen oxides and smoke emissions are the most significant emissions for the diesel engines. Especially, fuels containing high-level oxygen content can have potential to reduce smoke emissions significantly. The aim of the present study is to evaluate the influence of n-butanol/diesel fuel blends (as an oxygenation additive for the diesel fuel) on engine performance and exhaust emissions in a small diesel engine. For this aim five-test fuels, B5 (contains 5% n-butanol and 95% diesel fuel in volume basis), B10, B15, B20 and neat diesel fuel, were prepared to test in a diesel engine. Tests were performed in a single cylinder, four stroke, unmodified, and naturally aspirated DI high speed diesel engine at constant engine speed (2600 rpm) and four different engine loads by using five-test fuels. The experimental test results showed that smoke opacity, nitrogen oxides, and carbon monoxide emissions reduced while hydrocarbon emissions increased with the increasing n-butanol content in the fuel blends. In addition, there is an increase in the brake specific fuel consumption and in the brake thermal efficiency with increasing n-butanol content in fuel blends. Also, exhaust gas temperature decreased with increasing n-butanol content in the fuel blends.

Castor oil-based lubricant reduces smoke emission in two-stroke engines

Smoky emissions from two-stroke gasoline engines (2T) are a problem for the environment. Use of vegetable oil (oxygenate) is one solution. A biodegradable 2T-oil was developed from castor oil, which consisted of tolyl monoesters and performance additives but no miscibility-solvent. Evaluation revealed that on one hand it reduced smoke by 50–70% at 1% oil fuel ratio and on the other hand it was at par with standard product specification. Starting problems, piston-seizer or any other driving problems were not observed during the test. There is excellent potential for castor oil based biodegradable 2T-lubricant as a smoke pollution reducer.

Smoke Emission Reduction during Startup of a Standby Gas Turbine Generator Set

Smoke Emission Reduction during Startup of a Standby Gas Turbine Generator Set

Experimental Investigations on CI Engine in HCCI and Conventional Diesel Mode

An experimental investigation was carried out in diesel engine operated in both homogeneous charge compression ignition (HCCI) and conventional modes. The engine used in this investigation is single cylinder, 4 stroke, water cooled, constant speed, variable compression ratio diesel engine with a displacement of 553 cc. In conventional diesel mode, the fuel was injected 27 0 bTDC with a nozzle included angle 140 0 and the compression ratio 16.5. In HCCI mode, the fuel was injected 80 0 bTDC during compression stroke by using modified camshaft, with a nozzle 60 0 included angle. In HCCI mode, to control the phasing and rate of combustion, the effective compression ratio was reduced to 14.5. From the experimental results it is inferred that, HCCI mode of operation results in reduced smoke and NOx emissions significantly with a little increase of HC and CO emissions.

The Effects of Neat Biodiesel Usage on Performance and Exhaust Emissions from a Small Displacement Passenger Car Diesel Engine

The effects of using neat FAME (Fatty Acid Methyl Ester) in a modern small displacement passenger car diesel engine have been evaluated in this paper. In particular the effects on engine performance at full load with standard (i.e. without any special tuning) ECU calibration were analyzed, highlighting some issues in the low end torque due to the lower exhaust gas temperatures at the turbine inlet, which caused a remarkable decrease of the available boost, with a substantial decrease of the engine torque output, far beyond the expected engine derating due to the lower LHV of the fuel. However, further tests carried out after ECU recalibration, showed that the same torque levels measured under Diesel operation can be obtained with neat biodiesel too, thus highlighting the potential for maintaining the same level of performance. Moreover, the effects of FAME on brake specific fuel consumption and on engine out exhaust emissions (CO2, CO, HC, NOx and PM) were also evaluated at 7 different part load operating conditions, representative of the New European Driving Cycle. Both standard and specifically adjusted engine calibrations were evaluated for part load operating conditions, highlighting a 13% average rise of fuel consumption, on a mass basis, at same fuel conversion efficiency and CO2 emissions. A remarkable increase of CO and HC emissions at low load could be noticed, along with an almost negligible increase in NOx emissions when using a specifically adjusted engine calibration, and a considerable smoke emission reduction

Performance and combustion characteristics of biodiesel–diesel–methanol blend fuelled engine

An experimental investigation was conducted to evaluate the effects of using methanol as additive to biodiesel–diesel blends on the engine performance, emissions and combustion characteristics of a direct injection diesel engine under variable operating conditions. BD50 (50% biodiesel and 50% diesel in vol.) was prepared as the baseline fuel. Methanol was added to BD50 as an additive by volume percent of 5% and 10% (denoted as BDM5 and BDM10). The results indicate that the combustion starts later for BDM5 and BDM10 than for BD50 at low engine load, but is almost identical at high engine load. At low engine load of 1500 r/min, BDM5 and BDM10 show the similar peak cylinder pressure and peak of pressure rise rate to BD50, and higher peak of heat release rate than that of BD50. At low engine load of 1800 r/min, the peak cylinder pressure and the peak of pressure rise rate of BDM5 and BDM10 are lower than those of BD50, and the peak of heat release rate is similar to that of BD50. The crank angles at which the peak values occur are later for BDM5 and BDM10 than for BD50. At high engine load, the peak cylinder pressure, the peak of pressure rise rate and peak of heat release rate of BDM5 and BDM10 are higher than those of BD50, and the crank angle of peak values for all tested fuels are almost same. The power and torque outputs of BDM5 and BDM10 are slightly lower than those of BD50. BDM5 and BDM10 show dramatic reduction of smoke emissions. CO emissions are slightly lower, and NO x and HC emissions are almost similar to those of BD50 at speed characteristic of full engine load.

Experimental study of effects of oxygen concentration on combustion and emissions of diesel engine

Effects of oxygen concentration on combustion and emissions of diesel engine are investigated by experiment. The intake oxygen concentration is controlled by adjusting CO2. The results show that very low levels of both soot and NOx emissions can be achieved by modulating the injection pressure, timing, and boost pressure at the low levels of oxygen concentration. However, both CO and HC emissions and fuel consumption distinctly increase at the low levels of oxygen concentration. The results also indicate that NOx emissions strongly depend on oxygen concentration, while soot emissions strongly depend on injection pressure. Decreasing oxygen concentration is the most effective method to control NOx emissions. High injection pressure is necessary to reduce smoke emissions. High injection pressure can also decrease the CO and HC emissions and improve engine efficiency. With the increase of intake pressure, both NOx and smoke emissions decrease. However, it is necessary to use the appropriate intake pressure in order to get the low HC and CO emissions with high efficiency.

Controlled Injection of Compressed Air in Marine Diesel Engine Intake for Improved Load Acceptance

Abstract This paper addresses the improvement of load acceptance and the reduction of smoke emissions in a turbocharged marine diesel engine, during transient operation involving rapid load increases. The engine models were derived with system identification methods. Model Predictive Control provided the optimal quantity of injected air in the engine while minimizing smoke density (opacity), with constraint not to exceed a limit in intake manifold pressure, in order to avoid surge in the compressor. The effectiveness of the proposed control system was verified with transient response experiments on a full-scale marine diesel test engine. Results from various engine parameters comparing the standard operation without air injection showed improvement in transient loading.

Simultaneous reduction in cloud point, smoke, and NOx emissions by blending bioethanol into biodiesel fuels and exhaust gas recirculation

Palm oil has the important advantage of productivity compared with other vegetable oils such as rapeseed oil and soybean oil. However, the cold flow performance of palm oil methyl ester (PME) is poorer than other vegetable-oil-based biodiesel fuels. Previous research by the current authors has shown that ethanol blending into PME improves the cold flow performance and considerably reduces smoke emission. The reduced smoke may be expected to allow an expansion in the exhaust gas recirculation (EGR) limit and lead to reduced oxides of nitrogen (NO x). This paper experimentally analyses the influence of EGR on smoke and NO x emissions with ethanol-blended PME. The results show that the combination of ethanol blending and EGR is effective in reducing NO x and smoke simultaneously without the thermal efficiency deteriorating. The smoke reduction can be attributed to an improved fuel—air mixing by an increased ignition delay owing to the low cetane number of ethanol and by a promoted fuel spray atomization caused by the low boiling point of ethanol. The increase in the oxygen content also leads to lower soot emission. The decrease in local equivalence ratio by ethanol blending was also suggested by the flame observation in which flame with high luminosity, high temperature, and high KL factor shrinks.

Impact of thermal barrier coating application on the performance and emissions of a turbocharged diesel engine

In this study, the effect of thermal-barrier-coated piston top and combustion chamber surfaces on turbocharged diesel engine performance was experimentally investigated. Satisfactory performance was obtained with TBC1 (with coated cylinder head and valves) and TBC2 (with coated cylinder head, piston top, and valves). Compared with a standard diesel engine, engine power was increased by 2 per cent, the engine torque was increased by 1.5–2.5 per cent, and brake specific fuel consumption (b.s.f.c.) was decreased by 4.5–9 per cent. The NO x emissions were increased by 10 per cent in diesel engines with TBC coatings compared with a standard diesel engine. Experimental studies have shown that there is a reduction in smoke emissions of up to 18 per cent as a result of TBC application.

Study of performance, combustion and emission characteristics of diesel homogeneous charge compression ignition (HCCI) combustion with external mixture formation

The present investigation was to study the performance, combustion and emission characteristics of homogeneous charge compression ignition (HCCI) combustion of diesel fuel with external mixture formation technique. A stationary four stroke, single cylinder, direct injection diesel engine capable of developing 4.4 kW at 1500 rpm was modified to operate in HCCI mode. To achieve homogeneous mixture, diesel fuel was inducted in vapour form by using a diesel fuel vaporizer. The fuel vaporizer was mounted in the intake system to provide diesel vapour, which is mixed with air and inducted into the cylinder. To control the early ignition of diesel vapour–air mixture, cooled EGR technique was adopted. Experiments were conducted with diesel vapour induction without EGR and diesel vapour induction with 10% EGR and results are compared with conventional diesel fuel operation (DI @ 23 deg bTDC and 200 bar injection pressure). From the experimental results, it is found that, the ignition delay is reduced considerably for diesel vapour induction due to better mixture preparation and results in low emissions. A reduction of about 55% and 80% in NO x emissions and 20% and 30% reduction in smoke emissions are obtained for diesel vapour induction without EGR and Diesel vapour induction with 10% EGR compared to conventional mode of operation.

Characteristics of Unburned Hydrocarbons in a Low Compression Ratio Diesel Engine (Characteristics under Transient Operation and Reduction with Low Distillation Temperature Fuels)

In a DI diesel engine, reducing the compression ratio is effective to reduce smoke emissions without deterioration of NOx and thermal efficiency. However, with lower compression ratios, a low coolant temperature, or during the transient state, THC emissions significantly increase when using ordinary diesel fuel. The THC emissions during increasing loads significantly increased to very high concentrations from just after the start of the load increase until around the 10th cycle, rapidly decreased until the 20th cycle, and then gradually decreased to a steady state value after 1000 cycles. The dominant components present in the THC transient spike were lower hydrocarbons with carbon numbers around or below eight. In particular, ethylene showed a much higher concentration than the other components. In fully-warmed steady state operation with a compression ratio of 16 and diesel fuel, THC is reasonably low, but THC increases with lower coolant temperature or during the transient period just after increasing the load. This problem can be eliminated with a low distillation temperature fuel such as normal heptane. Benzene, butadiene, and other unregulated harmful emissions also increase under the high THC conditions with diesel fuel.