Effects of fuel reactivity and injection timing on diesel engine combustion and emissions

Recent strategies for simultaneously reducing NOx and soot emissions have focused on achieving nearly premixed, low-temperature combustion (LTC) in diesel engines. A promising approach in this regard is to vary fuel reactivity in order to control the ignition delay and optimize the level of premixing and reduce emissions. The present study examines such a strategy by performing 3-D simulations in a single-cylinder of a diesel engine. Simulations employ the state-of-the-art two-phase models and a validated semi-detailed reaction mechanism. The fuel reactivity is varied by using a blend of n-heptane and iso-octane, which represent surrogates for gasoline and diesel fuels, respectively. Results indicate that the fuel reactivity strongly influences ignition delay and combustion phasing, whereas the start of injection (SOI) affects combustion phasing. As fuel reactivity is reduced, the ignition delay is increased and the combustion phasing is retarded. The longer ignition delay provides additional time for mixing, and reduces equivalence ratio stratification. Consequently, the premixed combustion is enhanced relative to diffusion combustion, and thus the soot emission is reduced. NO_x emission is also reduced due to reduced diffusion combustion and lower peak temperatures caused by delayed combustion phasing. An operability range is observed in terms of fuel reactivity and SOI, beyond which the mixture may not be sufficiently well mixed, or compression ignited. The study demonstrates the possibility of finding an optimum range of fuel reactivity, SOI, and EGR for significantly reducing engine out emissions for a given load and speed.     

Performance of a diesel engine with water emulsified diesel prepared with optimized process parameters

An attempt has been made to produce stable water–diesel emulsion with optimal formulation and process parameters and to evaluate the performance and emission characteristics of diesel engine using this stable water–diesel emulsion. A total of 54 samples were prepared with varying water/diesel ratio, surfactant amount and stirring speed and water separation was recorded after 24 and 48 hr of emulsification. The recorded data were used in artificial neural network (ANN)-particle swarm optimization (PSO) technique to find the optimal parameters to produce water–diesel emulsion for engine testing. The predicted optimal parameters were found as 20% water to diesel ratio, 0.9% surfactant and 2200 rpm of stirrer for a water separation of 14.33% in one day with a variation of 6.54% against the actual value of water separation. Water–diesel emulsion fuel exhibited similar fuel properties as base fuel. The peak cylinder gas pressure, peak pressure rise rate and peak heat release rate for water–diesel were found higher as compared to diesel at medium to full engine loads. The improved air-fuel mixing in water–diesel emulsion enhanced brake thermal efficiency (BTE) of engine. The absorption of heat by water droplets present in water–diesel emulsion led to reduced exhaust gas temperature (EGT). With water–diesel emulsion fuel, the mean carbon monoxide (CO), unburned hydrocarbon and oxides of nitrogen (NO_x) emissions reduced by 8.80, 39.60, and 26.11%, respectively as compared to diesel.     

Experimental investigation on the performance and emission characteristics of a diesel engine by varying the injection pressure and injection timing using mixed biodiesel

Biodiesel is a promising fuel for compression ignition engines instead of diesel fuel. Due to the depletion of diesel fuel, an alternative fuel can be used in an engine. The experiments were conducted on a four-stroke, single cylinder CI engine. In this present investigation, an attempt has been made to study the influence of injection pressure (IP) and injection timing (IT) on the performance and emission characteristics of diesel engines by using mixed biodiesel (Thevetia peruviana, Jatropha, Pongamia, and Azadirachta indica). The injection pressure is varied from 200 to 230 bar and the injection timing is varied from 23 to 29° bTDC at an increment of 10 bar and 2° bTDC, respectively, and the results were compared with diesel. From this study, the results showed that the brake thermal efficiency (BTE) was increased by 2.4% with an increase in injection pressure and 1.5% with an increase in the injection timing for the maximum load, but lesser than diesel. Furthermore, a reduction of 5.08% of brake specific fuel consumption (BSFC) has been noticed for the rise in IP and IT with loads but higher than diesel. The reduction was 34.17%, 53.85%, and 29.7% and 29.17%, 53.85%, and 21.95% of hydrocarbons (HC), carbon monoxide (CO), and smoke emissions, respectively, at 230 bar injection pressure and at 27° bTDC injection timing. Also, a significant increase in nitrogen oxides (NO_x) and carbon dioxide (CO₂) emissions at the maximum load was observed by increasing the injection pressure and injection timing.     

Performance analysis of bioethanol (Water Hyacinth) on diesel engine

The increasing consumption and excessive extraction of conventional fuels is the matter of serious concern. Nowadays, world is looking for alternative sources of fuel which can partially replace conventional fuel dependence. The current investigation intends to provide evaluation of bio-ethanol preparation from Water Hyacinth (WH) and its influence on diesel engine performance under various operating conditions. This study explores the extraction of glucose from WH (Eichhornia crassipes) pretreated with sulfuric acid (H₂SO₄) for production of bio-ethanol. For the production of bio-ethanol different concentrations of H₂SO₄ acid hydrolysate (1%, 2%, 4%, 6%, 8%, and 10%) were prepared which was then followed by fermentation with cellulose fermenting yeasts. From results, it was observed that 4% H₂SO₄ acid hydrolysis produces higher concentrations of ethanol than other concentrations. Bio-ethanol extracted from WH was blended with diesel in different proportions (5%, 10%, 15%, 20%, and 25%) v/v and performance and emissions were experimentally investigated on single cylinder diesel engine under various load conditions. Experimental results show that 5 BED [5% bio-ethanol (WH + 95%diesel v/v) and 10BED (10% bio-ethanol (WH + 90%diesel v/v)] produces higher brake power, brake thermal efficiency and brake mean effective pressure with improved exhaust emission profiles than any other blend.     

Effective application of ethanol in diesel engines

This work aimed to prove the effects of adding different proportions of ethanol with diesel (DE) and ethanol–water mixture with diesel (DEW) in a single-cylinder diesel engine on the performance, emissions, and combustion parameters. The blends were stabilized by tetra methyl ammonium bromide (TMAB) as the additive. The study was conducted at two operating conditions initially on a normal diesel engine and in the second case the engine piston, valves, and cylinder head coated with zirconia (ZrO₂) alumina (Al₂O₃). The results showed that the addition of 10% ethanol with diesel performed almost equivalent to neat diesel with 29.2% BTE and a 17.7% decrease in smoke and an 11.4% increase in NOx emission at peak load compared to that of the base fuel. Modified engines with thermal barrier coating (TBC) performed superior to normal engines with 4% and 5.5% increase in BTE, respectively, for DE- and DEW-type fuels with reduced exhaust emissions. A 5% addition of water with diesel–ethanol blends favors a higher proportion of ethanol to be employed in diesel engines.     

Effects of thermal barrier coating on the performance and combustion characteristics of a diesel engine fueled with biodiesel produced from waste frying cottonseed oil and ultra-low sulfur diesel

In this study, the top surfaces of piston and valves of a four-strokes and direct-injection diesel engine have been coated—with no change in the compression ratio—with a 100 μm of NiCrAl lining layer via plasma spray method and this layer has later been coated with main coating material with a mixture of 88% of ZrO₂, 4% of MgO and 8% of Al₂O₃ (400 μm). Then, after the engine-coating process, ultra-low sulfur diesel (ULSD) as base fuels and its blend with used frying cottonseed oil derived biodiesel in proportion of 20%, volumetrically, have been tested in the coated engine and data of combustion and performance characteristics on full load and at different speeds have been noted. The results, which were compared with those obtained by uncoated-engine operation, showed that thermal efficiency increased, and engine noise reduced. Cylinder gas pressure values obtained from the diesel engine which has been coated with thermal barriers have been found to be somewhat higher than those of the uncoated-engine. Also, maximum pressure values measured in both engines and under the same experimental conditions through the use of test fuel have been obtained after TDC. Moreover, heat release rate and heat release have occurred earlier in the coated-engine. NOx emissions were increased while CO and HC emissions were remained almost the same with a little bit decrease.     

Investigation the effect of adding graphene oxide into diesel/higher alcohols blends on a diesel engine performance

ABSTRACT

This article aims to study the influence of the addition of graphene oxide nanoparticles (GO) to diesel/higher alcohols blends on the combustion, emission, and exergy parameters of a CI engine under various engine loads. The higher alcohols mainly n-butanol, n-heptanol, and n-octanol are blended with diesel at a volume fraction of 50%. Then, the 25 and 50 mg/L concentrations of GO are dispersed into diesel/higher alcohols blends using an ultrasonicator. The GO structures are examined using TEM, TGA, XRD and FTIR. The findings show that there is a reduction in p_max. and HRR when adding higher alcohols with diesel fuel. Regarding engine emission, there is a significant improvement in emissions formation with adding higher alcohols. The addition of GO into diesel/higher alcohols blends improves the brake thermal efficiency by 15%. Moreover, the p_max. and HRR are both enhanced by 4%. The CO, UHC and smoke formation are reduced considerably by 40%, 50 and 20%, respectively, while NO_x level is increased by 30% with adding GO. Finally, adding high percentages of n-butanol, n-heptanol, and n-octanol with diesel fuel with the presence of GO has the potential to achieve ultra-low CO, UHC, and smoke formation meanwhile keeping high thermal efficiency level.     

Combustion,emission, and phase stability features of a diesel engine fueled by Jatropha/ethanol blends and n-butanol as co-solvent

ABSTRACT

The main challenge of utilizing ethanol in diesel engines in blending mode is the phase separation issue. Therefore, an attempt has been performed to enhance the stability feature of ethanol/Jatropha biodiesel (JME) blends by using n-butanol as co-solvent. The 10% by volume of n-butanol is added to the mixtures of 10% and 20% ethanol and 70% and 80% JME, which is denoted as JME10Bu10E and JME10Bu20E, respectively. The phase stability of the evaluated fuels is examined employing visual approach and Thermogravimetric analysis. These methods confirm that there is no phase separation for more than 2 months under ambient conditions. Then, the combustion and emission features are investigated utilizing a diesel engine run with different loads and constant speed. The findings demonstrate that the p_max. and HRR are increased by adding ethanol. The ignition delay is extended with the addition of ethanol while the combustion period is almost the same. The bsfc is decreased by adding ethanol compared to JME fuel. The CO, UHC, and NO_x formations are reduced markedly by 40%, 40%, and 40%, respectively, with adding ethanol. Finally, using n-butanol and JME as co-solvents with ethanol supports the growth of renewable energy in the CI engine.     

Comparison of jatropha and karanja biofuels on their combustion characteristics

Biofuel blends produced from Jatropha (Jatropha curcas) and Karanja (Pongamia pinnata) oil were evaluated for their combustion properties. Two kinds of blends (regular diesel with Jatropha and Karanja oil) were prepared at 20% volume to the diesel and tested as alternative fuels in single cylinder (vertical), water-cooled, direct injection diesel engine at the rated speed of 1500 rpm. The performance of the engine in terms of thermal efficiency at full load for diesel was 30%. For Jatropha and Karanja biodiesel blends, the thermal efficiencies were 29.0% and 28.6%, respectively. The maximum cylinder pressure and ignition delay for biodiesel fuel blends are very close to that of regular diesel. Prolonged combustion was observed for Karanja oil blend in comparison to Jatropha oil blend. The combustion pattern also reveals the slow burning characteristics of vegetable oils and this study indicates that the blended biofuels have combustion characteristics that are similar to regular diesel fuels.     

Factorial analysis of diesel engine performance using different types of biofuels

In this study, several bio-source-fuels like fresh and waste vegetable oil and waste animal fat were tested at different injector pressures (120, 140, 190, 210 bar) in a direct-injection, naturally aspirated, single-cylinder diesel engine with a design injection pressure of 190 bar. Using 2k factorial analysis, the effect of injection pressure (Pi) and fuel type on three engine parameters, namely, combustion efficiency (etac), mass fuel consumption (mf), and engine speed (N) was examined. It was found that Pi and fuel type significantly affected both etac and mf while they had a slight effect on engine speed. Moreover, with diesel and biodiesels, the etac increased to a maximum at 190 bar but declined at the higher Pi value. In contrast, higher Pi had a favorable effect on etac over the whole Pi range with all the other more viscous fuels tested. In addition, the mass fuel consumption consistently decreased with an increase in Pi for all the fuels including the baseline diesel fuel, with which the engine consistently attained higher etac and higher rpm compared to all the other fuels tested.     

Performance evaluation of Nahar oil–diesel blends in a single cylinder direct injection diesel engine

This study attempts to use plentiful available high oil content (67% of Nahar seed kernel) non-edible feedstock as a source for powering diesel engine. Various performance and emission characteristics of prepared Nahar oil–diesel blends (5%, 10%, 20%, 30%, and 40%) are analyzed in a single cylinder direct injection diesel engine at different load spectrum, in order to judge the optimum blend, which can be efficiently used in a diesel engine. 10% blending of Nahar oil with diesel fuel has shown a reduction in hydrocarbon and carbon monoxide emission by 8.64% and 8.34%, respectively. With the increase in blend concentration, the nitrogen oxide emission decreased considerably and smoke emission increased slightly. Further pressure crank angle and heat release rate analysis of 10% blending of Nahar oil with diesel confirms its smooth combustion inside the engine combustion chamber.     

Characterization of a limestone in a batch fluidized bed reactor for sulfur retention under oxy-fuel operating conditions

CO₂ and SO₂ are some of the main polluting gases emitted into atmosphere in combustion processes using fossil fuel for energy production. The former is one of the major contributors to build-up the greenhouse effect implicated in global climate change and the latter produces acid rain. Oxy-fuel combustion is a technology, which consists in burning the fuel with a mix of pure O₂ and recirculated CO₂. With this technology the CO₂ concentration in the flue gas may be enriched up to 95%, becoming possible an easy CO₂ recovery. In addition, oxy-fuel combustion in fluidized beds allows in situ desulfurization of combustion gases by supplying calcium based sorbent.In this work, the effect of the principal operation variables affecting the sulfation reaction rate in fluidized bed reactors (temperature, CO₂ partial pressure, SO₂ concentration and particle size) under typical oxy-fuel combustion conditions have been analyzed in a batch fluidized bed reactor using a limestone as sorbent. It has been observed that sulfur retention can be carried out by direct sulfation of the CaCO₃ or by sulfation of the CaO (indirect sulfation) formed by CaCO₃ calcination. Direct sulfation and indirect sulfation operating conditions depended on the temperature and CO₂ partial pressure. The rate of direct sulfation rose with temperature and the rate of indirect sulfation for long reaction times decreased with temperature. An increase in the CO₂ partial pressure had a negative influence on the sulfation conversion reached by the limestone due to a higher temperature was needed to work in conditions of indirect sulfation. Thus, it is expected that the optimum temperature for sulfur retention in oxy-fuel combustion in fluidized bed reactors be about 925–950 °C. Sulfation reaction rate rose with decreasing sorbent particle size and increasing SO₂ concentration.     

Impact of various blends of Mimusops elengi methyl esters on performance and emission characteristics of a diesel engine

The basic objective of the research work was to study the effect of various blends of Mimusops elangi methyl ester (MEME) on engine performance, combustion, and emission characteristics of a single-cylinder direct-injection compression ignition engine, running at constant speed. The raw oil was extracted from Mimusops elangi seeds through mechanical crusher. The neat MEME was obtained through transesterification process and mixed with diesel in versatile proportions of 10% of MEME (10% MEME–90% Diesel), 20% of MEME(20% MEME–80% Diesel), 30% of MEME(30% MEME–70% Diesel), 40% of MEME(40% MEME–60% Diesel), and 100% MEME on a volume basis. Their properties were validated based on ASTM standards. Experimental investigation revealed that the 20% blend resulted in 4.18%, 5.12% more prominent performance characteristics of brake thermal efficiency, brake specific energy consumption, and superior emission diminution of 5.26% of HC, 16.6% of CO, 6.2% of smoke when compared with base diesel fuel, despite marginal penalty of 5.26% of carbon dioxide and 4.8% of oxides of nitrogen emission at full load condition. Characteristics of combustion parameters like pressure inside the cylinder and rate of the heat released were superior for 20% blend of MEME at the peak load condition.     

Verdant vehicles via viscoelasticity

The combustion of hydrocarbon (HC) fuels in internal combustion (IC) engines is modified by the presence of a few parts per million of megadalton molecular weight elastomers. The viscoelasticity imparted provides: reduced fuel vaporization, lesser back pressure, larger average droplet sizes, and lower combustion chamber temperatures. These effects result in: a reduction of emissions of HC, CO and NO_x of more than 70%, a substantial decrease in the number of particulates from diesel engines, a drop in combustion temperatures of more than 30vv°C, increases in engine power of more than 10%, an improved fuel octane rating, and economies of fuel consumption of more than 20%. The results are magnified during transitions, especially in the lower gears, used more often in urban traffic, where normal fuels emit more pollutants. These effects have a positive public health impact due to reductions in ozone, acid rain, particulates and partially oxidized HC.     

Performance evaluation and emission characteristics of biodiesel-ignition enhancer blends propelled in a research diesel engine

This study details the effect of the Di-Methyl-Ether(DME) as a cetane improver on neat cashew nut shell biodiesel (CBD100) to assess the emission and performance engine characteristics. Four fuels, namely, diesel, biodiesel (Cashew nut shell Methyl Ester), a blend of CBD100-10% and 20% by volume of DME (CBD90DME10and CBD80DME20) are prepared and tested on a stationary research diesel engine. The experimental parameters for CBD80DME20 showed a 1.6% increase in thermal efficiency thereby reducing 4.1% of fuel consumption than the neat biodiesel at peak conditions. Experimental result exposed that 20% of DME reduces 3.4% CO, 4.2% HC and 8.8% NOx and 8.4% smoke emissions of CBD100. Based on the outcome of this work, it is clear that CBD80DME20 shall be employed as a substitute fuel for diesel engine.

Abbreviations: CI: Compression ignition; CBD100: Cashew nut shell Bio-diesel; DME: Di-methyl ether; CO: Carbon monoxide; BTE: Brake thermal efficiency; BSFC: Brake specific fuel consumption; CBD100: 100% Biodiesel; CBD90DME10: 90% biodiesel + 10% di-methyl-ether; CBD80DME20: 80% biodiesel + 20% di-methyl-ether; HC: Hydrocarbon; NO_x: Oxides of nitrogen.     

Heat dissipation characteristic in the intake grille and radiator of a fuel cell vehicle

ABSTRACT

In this study, a three-dimension (3D) computational model was proposed to investigate the flow and heat transfer characteristics of the intake grilles of two different fuel cell vehicles. The models of the intake grilles were constructed according to the actual sizes of two vehicles, namely, Roewe 950 and Toyota Mirai, considering the heat dissipation unit to simplify the heat transfer model of the vehicle. The results showed that relative to Roewe 950, Mirai intake air flow rate was approximately 10% higher, the heat transfer capacity was approximately 7% higher, and the intake grille area was larger. The coolant outlet temperature of Mirai was lower than that of Roewe 950, which was beneficial for the long term and stable operation of a fuel cell. This comparative study provided guidance for the intake grille and radiator design of fuel cell vehicles. The only difference between fuel cell vehicles on the market and conventional vehicles was that in the former, the internal combustion engine was replaced with a fuel cell stack, which had insufficient heat transfer capacity because of the reducing temperature difference. Increasing the intake grille area and the heat exchange capacity of the radiator were the key issues for the development of fuel cell vehicles. In this study, an optimal window opening angle of the radiator fin of 23° provided a maximal heat transfer coefficient.     

Engine Performance and Emission Characteristics of Plastic Oil Produced from Waste Polyethylene and Its Blends with Diesel Fuel

The overall objective of this study was to explore the utility of waste plastics as a potential source of diesel fuel. An experimental study was conducted to evaluate the use of various blends of plastic oil produced from waste polyethylene (WPE) with diesel fuel (D). WPE was degraded thermally and catalytically using sodium aluminum silicate as a catalyst. The oil collected at optimum conditions (414°C–480°C range and 1 h reaction time) was fractionated at different temperatures and fuel properties of the fractions were measured. Plastic oil was blended with diesel fuel at the volumetric ratios of 5%, 10%, 15%, 20%, and 100%. Fuel properties of blends are found comparable with those of diesel fuel within the EN 590 Diesel Fuel standard and they can also be used as fuel in compression ignition engines without any modification. Engine performance and exhaust emission studies of 5% WPE-D (WPE5) blend were performed. Experimental results showed that carbon monoxide (CO) emission is decreased by 20.63%, carbon dioxide (CO₂) emission is increased by 3.34%, and oxides of nitrogen (NO_x) emission is increased by 9.17% with WPE-D (WPE5) blend compared to diesel fuel.     

Electrochemical NOx reduction and oxidation of HC and PM emissions from biodiesel fuelled diesel engines using electrochemically activated cell

NOx emission is produced during combustion of fuels at high temperature. Excessive release of NOx causes several effects on living organisms and environment. In this work, the efforts to reduce NOx emission by developing electrochemically activated cells (EACs) for a diesel engine fuelled with diesel and biodiesel fuel are discussed. EAC technique is vital after treatment technology attempted in this work to simultaneous control of NOx, HC, and PM emissions. In this method, two types of EACs were developed. The CuO–YSZ electrolyte and CuO–YSZ electrolyte with BaO coating were developed and tested with diesel and biodiesel exhaust. Compared with diesel fuel, use of biodiesel fuel increased NOx emission by 11% and PM emission was slightly reduced with biodiesel, which was due to the presence of fuel bond oxygen content in biodiesel. The investigation has demonstrated low-temperature activation of the EACs at 250–350°C which was due to the addition of CuO to YSZ. In this work, maximum NOx reduction was achieved for CuO–YSZ cells with BaO NOx storage and the simultaneous control of HC and PM emission also was observed in this technique. NOx reduction by EAC is a vital technique and can be retrofitted with any diesel engine for emission reduction.     

Experimental investigation of performance and emission characteristics of diesel engine using Jatropha biodiesel with alumina nanoparticles

Biodiesels have come up as a very strong alternative for diesel fuel. Biodiesels such as Jatropha Oil Methyl Ester (JOME) are comparable in performance with that of the diesel engine. The thermal efficiency of engines fuelled with biodiesels was found lower than conventional diesel fuel but due to the bio-origin, the emission characteristics are much better. However, biodiesel increases the NOx emissions as these are rich in oxygen, hence nanoparticles are used in this experiment to curb the high temperatures and reduce the NOx formation. The experiment on naturally aspired diesel engine was conducted with four prepared test fuels other than neat diesel and neat biodiesel. The 50 and 150 of alumina nanoparticles were added separately to the pure diesel and pure Jatropha biodiesel to form the nano emulsions using ultrasonicator. The properties of nanoemulsion were evaluated using dynamic light scattering technique using zetasizer. The performance and emission characteristics of multi-cylinder diesel engine with these nanoemulsions were compared with that of neat fuels. The results showed that using nanoparticles with diesel and biodiesel can contribute in a more efficient, economical, and eco-friendly engine operation.     

Industrial waste to energy by circulating fluidized bed combustion

Industrial waste is a good resource from the viewpoint of efficient waste management. The vital need for energy utilization and environmental protection mean it is of interest to develop circulating fluidized bed combustion (CFBC) to burn solid wastes with low pollutant emissions. The paper presents some explanatory studies on waste-to-energy in a pilot scale CFCB facility. A series of combustion/incineration tests have been carried out for the industrial wastes: petroleum coke, waste tire and sludge cakes with various moisture contents. It seems that the CFBC has feed flexibility without modifying heat transfer equipments for energy recovery. In addition, the results of experimental tests demonstrate that gas emissions from waste incineration in CFBC can be well controlled under local regulation limits.At normal operation temperature in CFBC (approx. 800°C), the heat transfer coefficient between bulk bed and bed wall is on the order of 10² W/m^2° C, which is useful to estimate the energy recovery of waste combustion by CFBC. A practical and simple guide is proposed to estimate the energy recovery from waste combustion by CFBC, and to find maximum allowable moisture content of waste if there is to be any energy recovery without auxiliary fuel.