Unburned Hydrocarbons Research Articles

Performance and emissions characteristics of biodiesel in diesel engine

The climate and fuel supply have been problematic emphasis on alternative fuels for combustion engines. Different research studies tested various alternative fuels. In this connection, biodiesel is the most promising diesel fuel based on a literature survey. In this paper, the prospects and potential for the use of biodiesel and increasing biodieseldiesel blending are studied by a fixed compression ratio, Optimum blending and enhanced performance engine parameter and pollution control should be proposed based on experiments. Experiments for a set compression ratio (17:1) undertaken utilising biodiesel cotton seed oil (CSME) diesel blends, i.e. B0, B10, B20, B30, without full loading rates, compared to the base cases (e.g. diesel engine fuel). The parameters may evaluate the fuel consumption and thermal efficiency of the brakes, Unburned hydrocarbons, and nitrogen oxides in emission of carbon monoxide. The results concluded that, B20 (20% biodiesel and 80% diesel) is the most efficient compared to other mixtures.

A study on flexible dual-fuel and flexi combustion mode engine to mitigate NO, soot and unburned emissions

In the present study, an existing commercial light-duty automotive diesel engine is modified to a flexible dual-fuel engine (FDFE). The FDFE operates with different low and high reactivity dual fuel combinations under low temperature combustion (LTC) mode using combined multipoint fuel injection and common rail direct injection systems. The FDFE can smoothly transit between LTC and conventional diesel combustion (CDC) mode. FDFE combines SI and CI benefits and stands as a potential internal combustion engine for future hybrid electric options. In this study, the modified engine was operated in flexi fuel mode with methanol/diesel, methanol/biodiesel, methanol/dimethyl ether (DME), methanol/polyoxymethylene dimethyl ether (PODE), (methanol + Isobutanol blends)/diesel and (methanol + PODE blends)/diesel in LTC strategy at a different speed and torque conditions. This approach improved the brake thermal efficiency by 8%, decreased NO and soot emissions by more than 90% compared to CDC mode. The improvement in brake thermal efficiency reduced CO2 emissions compared to CDC mode. In the FDFE engine, combustion phasing and fuel energy input are maintained as same as in CDC mode to investigate the dual-fuel effects in LTC mode over a neat diesel mode. Experimental study with energy and exergy analysis was carried out to assess the technical suitability of the FDFE as compared to the conventional diesel engine. The results proved that without relying on the after- treatment systems and fossil fuels, it is possible to reduce the NO, soot, unburnt hydrocarbon, carbon monoxide and CO2 emissions from the diesel engine, paving the way for extending the life of the diesel engine.

RETRACTED: Exploration over combined impacts of modified piston bowl geometry and tert-butyl hydroquinone additive-included biodiesel/diesel blend on diesel engine behaviors

Nowadays, the use of biodiesel for diesel engines has been attracting researchers aiming to improve engine characteristics although the engine performance could be decreased while utilizing biodiesel. In this aspect, optimizing the piston bowl geometry is one of the useful approaches to enhance the efficiency of the biodiesel-powered diesel engine. In this study, the standard piston of an existing diesel engine was modified into two different combustion bowls, namely Symmetrical Stepped Curved-V (SSCV) and Symmetrical Spline-V (SSV), to evaluate the CI engine performance powered with mixtures of sesame-originated biodiesel, diesel fuel, and tert-butyl hydroquinone (TBHQ) additive through two-stage experiment. In the first phase, experiments were carried out on two modified piston bowls powered by diesel and S20 (20% sesame biodiesel + 80% diesel fuel). Resultantly, SSV piston revealed superior engine characteristics to SSCV piston and standard piston due to enhanced air–fuel mixing and more complete combustion of SSV piston-based engine. Indeed, SSV piston operation exhibited an 8.68% of increased brake thermal efficiency (BTE), 6.54% of curtailed brake-specific fuel consumption (BSFC), 4.76% of lowered carbon monoxide (CO), 4.84% of decreased unburnt hydrocarbon (HC), and 2.22% of lowered smoke opacity but with increased nitrogen oxide (NOx) by 14.14% in comparison to diesel. In the 2nd phase, to control the NOx emission effectively, a TBHQ additive was added to the S20 sample at different proportions (500 mg and 1000 mg) to analyze the test engine behaviors with modified piston shapes. As a result, S20 + 500 mg TBHQ at 100% load improved BTE by 5.79% and reduced BSFC by 4.36% in the case of SSV piston. Moreover, it curtailed emissions of CO, HC, NOx, and smoke opacity by 13.33%, 15.49%, 12.09%, and 9.44%, respectively, when equated with diesel. Overall, S20 + 500 mg TBHQ could be thought of as a possible alternative fuel on SSV piston as it resulted in superior performance and emission characteristics in the existing standard engine. The current study's findings could pave the way for the development of diesel engines with modified piston geometry that is more efficiently compatible with biodiesel blends and additives.

Dual-fuel diesel engine run with injected pilot biodiesel-diesel fuel blend with inducted oxy-hydrogen (HHO) gas

Oxy-hydrogen gas (HHO) is a carbon-free fuel, which is produced by the water electrolysis process. It can be used as an alternative to hydrogen since the current global hydrogen production and storage may not meet the required demand for transportation applications. This research work investigates the engine behavior of a compression ignition (CI) engine operated in dual-fuel mode by inducting HHO as a primary fuel and injecting two different pilot fuels viz., diesel, and JME20 (a blend composed of 80% diesel with 20% Jatropha methyl ester) at optimized engine conditions. The results revealed that; heat release rate, brake thermal efficiency, exhaust gas temperature, and nitric oxide emission are found to be higher about 5.2%, 1.1%, 18.6%, and 19.6% respectively, while unburnt hydrocarbon, carbon monoxide, and smoke emissions are reduced by about 33.3%, 29.4%, and 18.7% respectively in Opt.JME20 + HHO operation compared to that of the baseline data at maximum load.

Experimental Investigation on the Effectiveness of Biodiesel Based Sulfur as an Additive in Ultra Low Sulfur Diesel on the Unmodified Engine

ABSTRACT Adequate lubricity and energy content play a significant role in fuel injection and performance in the diesel engine. The major challenge with ultra-low sulfur diesel (ULSD) is lower lubricity. This study aims to perform experimental analysis to investigate the wear behavior of commercial diesel with biodiesel-based sulfur (BBS) solution as an additive and examine the engine characteristics. BBS is a novel solution with higher ester and sulfur content (500 ppm). By doping this novel solution, two test fuels, BS6D1 and BS6D2 were prepared with a sulfur concentration between BS4 and BS6 commercial diesels. Compared to BS6 commercial diesel, the BS6D2 sample showed a significant reduction in mean wear scar diameter (MWSD) and coefficient of friction (COF) by 43.97% and 33%, respectively. At peak load, BS6D2 had 4.13% higher brake thermal efficiency than BS6 diesel. Due to enhanced ignition quality, the brake-specific energy consumption (BSEC) for the BS6D2 sample was found to be the lowest, i.e., 3.85% less than BS6 diesel. Furthermore, a significant reduction in exhaust pollutants for BS6D2 sample compared to BS6 diesel at maximum loads, such as smoke opacity (14.06%), unburnt hydrocarbon (8.82%), and carbon monoxide (20.45%). In conclusion, the BS6D2 sample produces the best results of all the tested fuel samples evaluated on the unmodified diesel engine.

Exhaust Gas Emissions of Homogeneous Gasoline-Methanol-(Ethanol) Blends

In recent years, one of the most logical efforts made to reduce the dependence on fossil energy sources is the use of a gasoline-methanol fuel blend. However, the problem in using a gasoline-methanol blend as fuel is that the methanol will eventually separate itself from the gasoline unless they are properly blended together, this is because methanol has a polar hydroxyl group called monohydric that binds water vapor together, causing the mixture to separate. Previous research showed that adding a small amount of ethanol to the gasoline-methanol blend makes it a homogeneous blend. Therefore, this research aims to identify the exhaust emissions of the homogenous gasoline-methanol-(ethanol) blend. For each blended fraction was tested on a single-cylinder four-stroke engine. The emission test is carried out in two stages which include the gasoline mode, and the alcohol mode. These two measurement modes undergo a validation process to correct the differences in the measurement results of the gasoline-methanol-ethanol blends. The test results show that increasing the methanol fraction in the gasoline-methanol-(ethanol) fuel blend results in reduced emission of carbon monoxide and unburnt hydrocarbon because methanol has a high enthalpy of evaporation, which increases both volumetric efficiency and complete combustion. In addition, the increase in the methanol fraction in the gasoline-methanol-(ethanol) blend showed a higher increase in carbon dioxide emissions. This is because methanol and ethanol have a much lower energy content than gasoline. Therefore, its energy production per unit time requires more fuel molecules.

Ethanol biofuel production and characteristics optimization from wheat straw hydrolysate: Performance and emission study of DI-diesel engine fueled with diesel/biodiesel/ethanol blends

Bioethanol has been classified as the most widely utilized biofuel globally because it helps greatly decrease crude oil consumption and pollution. In this study, bioethanol production improved by 3.6-fold after optimization conditions for commercial Saccharomyces cerevisiae on hydrolysate obtained from enzymatic saccharification of Aspergillus niger to 1% NaOH pretreated wheat straw. 26.0% bioethanol was obtained after 96 h at 30 °C using 10% (W/V) inoculum size of Saccharomyces cerevisiae at pH 5.0 and 2% molasses additives under static condition. After optimization, bioethanol was produced on a large scale, and distillation was carried out, then bioethanol was characterized using Gas chromatography (GC) analysis and 1H NMR. On large-scale production, 1 kg NaOH pretreated wheat straw was fermented with Aspergillus niger to produce 10 L of hydrolysate that concentrated to 4 L using a rotary evaporator. After concentration, reducing sugar became 35.08 mg/ml, then 2% molasses were added, and the final sugar concentration became 41.7 mg/ml. Finally, reducing sugar was fermented by Saccharomyces cerevesiae to produce 1 L of bioethanol. In addition, the obtained bioethanol was blended by the commercial diesel#1/WCO biodiesel commixture with 10% and 20% by volume. The blends of 50%diesel/50%biodiesel, 10% bioethanol/45%diesel/45%biodiesel, and 20%bio ethanol/40%diesel/40%biodiesel were tested as new fuel blends in a single cylinder air-cooled direct injection diesel engine. The engine performance and emission have been recorded at different engine loads and fixed speeds of 1500 rpm. The obtained results reveal that the engine BTE has been enhanced where the engine NOx was reduced if 10% of bioethanol has been added. While increasing bioethanol to 20% by volume base increases the combustion of unburned hydrocarbon and CO emission.

Effect of Low-Cost Perovskite Based Lean NOx Trap to Reduce the NOx Emission for CRDI Engine

Lean NOx trap (LNT) is an after-treatment technology that targets NOx emissions from an IC Engine and reduces it by using fuel as the reductant. The main mechanisms involved in this process are (i) oxidation of NO into NO2, (ii) Entrapment of NO2 over an alkali Earth metal in the form of nitrates, and (iii) Regeneration and reduction of NO2. The oxidation and reduction reactions are usually performed over rare Platinum Group Metals (PGM). The alternate cycling of operation modes helps in the regeneration and reduction stage due to the presence of unburnt hydrocarbons and carbon monoxides. These HC and CO generated during profitable operation can reduce agents similar to ammonia in SCR (Selective Catalytic Reduction). In the case of LNT, the fuel-injected for reduction imposes a penalty on the system. Cobalt-based perovskites with the chemical formula “ACoO3” (where “A” denotes Ba, Sr, etc.) show excellent absorption and reduction tendencies towards NOx and are highly suited for LNT as they have higher NO oxidation capacity. This research experimented with two different coating procedures (with and without binder) with three other perovskite catalysts–BaCoO3, SrCoO3, and Ba0.5Sr0.5CoO3. Both the coatings were tested for their adherence, and it revealed that the binder-less layer had only 4% coating loss after 2 hrs of sonication. BaCoO3 showed higher NOx absorption due to the higher electropositive nature of barium. The peak conversion efficiency attained in this experiment was 84% at a catalyst temperature of 350°C and 40% load condition.

Comparison of the emission factors of air pollutants from gasoline, CNG, LPG and diesel fueled vehicles at idle speed

The emission factor (EF) is a parameter used to assess vehicle emissions. Many studies have reported EFs for vehicles in driving conditions. However, the idling emissions should not be neglected in characterizing actual vehicle emissions in congested large cities, where idling is very common on the road. Whereas, EF data for idling vehicles have scarcely been reported in the literature, let alone comparison of different fuels. In this study, the EFs of passenger cars burning four types of fuels - gasoline, compressed natural gas (CNG), diesel, and liquefied petroleum gas (LPG) were measured and compared. The emissions data for CO, CO2, unburned hydrocarbon (HC), and NO were recorded to calculate fuel-based EFs in units of g pollutants/kg fuel burned. EFs for CO, HC, and NO were compared for the four fuels. Diesel vehicles had the highest EF for CO, with an average value of 35.12 ± 21.37 g/kg fuel, due to low concentration of CO2 in lean operation compared to CO emission. CNG vehicles had the highest EF for HC, with an average value of 28.15 ± 11.97 g/kg fuel, due to high concentration of unburned methane gas due to slow CNG flame speed whereas diesel vehicles again had the highest EF for NO due to high temperature and pressure and freezing of NO decomposition reaction, with an average value of 12.07 ± 5.37 g/kg fuel. Further comparison was conducted to analyze the effects of two additional variables on EF: engine displacement volume and model/brand year. Only the gasoline-fueled vehicles showed an increase in EFs (for CO, HC and NO) with the vehicle age according to the model year. However, no clear correlation was observed for CNG, LPG, and diesel-fueled vehicles. Finally, the EF results were compared with those reported in the literature, which have been measured in various countries under both idling and non-idling conditions. Because the idling EFs were not substantially smaller than those under moving conditions, and vehicles spend substantial time idling in large cities, idling emissions should not be ignored in the emission inventories for large cities.

Numerical Study on the Effects of Pilot Diesel Quantity Coupling EGR in a High Pressure Direct Injected Natural Gas Engine

ABSTRACT The natural gas high pressure direct injection (HPDI) engines have attracted attention due to their high combustion stability and thermal efficiency comparable to diesel. However, the nitrogen oxides (NOx) emissions from HPDI engines remain high. In this study, the coupling effects of the exhaust gas recirculation (EGR) and pilot diesel quantity were investigated on a four stroke HPDI engine by simulation. Three pilot diesel quantities and four EGR rates were involved, and the combustion and emission characteristics of the engine were compared and discussed. The results show that with increasing EGR rate, the maximum combustion pressure (Pmax) decreases with different pilot diesel quantity, and the crank angle corresponding to the maximum combustion pressure (CPmax), the crank angle corresponding to the maximum heat release rate (CHRRmax) and the crank angle corresponding to the 50% cumulative heat release (CA50) are all pushed back. NOx emissions decrease gradually with the increase of EGR rate, but soot, unburned hydrocarbon (HC) and carbon monoxide (CO) emissions and methane escape all increase and the indicated thermal efficiency (ITE) decreases. The traditional “trade-off” relationship between NOx and soot emissions still exists on HPDI engine and becomes more obvious as the quantity of pilot diesel increases. NOx and soot emissions can be well balanced at moderate EGR rate. Increasing the quantity of pilot diesel can partially offset the hysteresis effect of EGR on the combustion process. And when the EGR rate is controlled within 30%, increasing the quantity of pilot diesel is beneficial to reduce HC and CO emissions and methane escape. By increasing the quantity of pilot diesel coupled with a moderate level of EGR rate, it is possible to significantly reduce NOx emissions while maintaining the ITE, methane escape and unburned diesel, HC and CO emissions at the same level as without EGR. But soot emissions will increase substantially.

The combined effect of acetone and ZnO with diesel–biodiesel blends on the performance, combustion and emission characteristics of diesel engine

ABSTRACT In this experimental study, the performance, combustion and emission analysis of the combined effect of acetone and Zinc Oxide (ZnO) dispersed diesel–biodiesel (B20) blends were done in four-stroke, single-cylinder and water-cooled diesel engine. ZnO was synthesized by the solvothermal method using cow urine as a solvent and reducing agent. The synthesized ZnO was characterized by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The biodiesel was produced from waste cooking oil through a trans-esterification process. The synthesized ZnO was dispersed in 10, 20 and 30 ppm with diesel–biodiesel blend along with 10% of acetone to form B20A10Zn10, B20A10Zn20 and B20A10Zn30 test fuels. The experimental results show that adding acetone and ZnO with diesel–biodiesel blend tends to promising physiochemical properties of the test fuels and produced better results in performance and emission. The test fuel, B20A10Zn30, gave a better outcome than all other fuels and recorded a 0.4% increase in Brake Thermal Efficiency (BTE), while there was an 8% increase in Brake Specific Fuel Consumption (BSFC). Compared to diesel, the emissions, such as Carbon Monoxide (CO), Unburned Hydrocarbon (UHC), Oxides of Nitrogen (NOx), and smoke, were 7.97%, 20%, 1.8% and 1.49% lower than the conventional diesel.

Effects of fuel injection on the combustion and emission performance of a trapped vortex combustor

An experimental study was conducted at atmospheric pressure at 473 K to investigate the effects of fuel injection strategy on the combustion and emission characteristics of a trapped vortex combustor. In the test, the combustor was fueled by a simple pressure-swirl atomizer and novel atomizer to realize a normal circular spray pattern and fan spray pattern, respectively. The combustion and emission characteristics of the combustor were fully examined under a variety of Mach numbers and fuel-to-air ratios. The effects were directly explored in terms of combustion efficiency, pattern factor, and pollutant emissions. The results indicated that the combustion and emission characteristics of the combustor are highly dependent on the fuel injection strategy. When compared to the simple pressure-swirl atomizer, the novel atomizer realized evident advantages in terms of combustion efficiency, pattern factor, and pollutant emissions of carbon monoxide and unburned hydrocarbons under a wide range of operating conditions. This is mainly attributed to the suitable spray pattern and smaller droplet size realized by the novel atomizer.

Evaluation of performance, emissions and combustion attributes of CI engine using palmyra biodiesel blend with distinct compression ratios, EGR rates and nano-particles

This paper presents the use of palmyra oil biodiesel as a prospective renewable alternate fuel for diesel engines. An experimental study has been conducted with an intention to enhance the engine characteristics of Palmyra oil methyl ester (POME) blended diesel by the approach of varying the compression ratio, different EGR rates along the amalgamation of Nano additives in the fuel. The Palmyra oil methyl ester (POME) blends of 10%, 20% and 30% are preliminarily examined, the POME20 blend exhibited better performance compared to other blends and factored as a preferable blend. Hence the investigation has been proceeded using POME20 at different loads. From the experimental results it was observed that brake thermal efficiency was enhanced by 2.72% and BSFC was lowered by 7.8% and reduction in exhaust emissions like carbon monoxide, unburnt hydrocarbons and smoke opacity by 17.64%, 13.8% and 3.5% respectively were found at CR20:1 when related to CR18:1, but, NOx emissions were found to be increased. While the added 6% and 12% of EGR to POME20-CR20 results showed a reduction in the NOx emission compared to diesel. Though the 12% EGR has shown a greater reduction in NOx its performance has greatly deteriorated than the 6% EGR. However, the result of amalgamating the fuel with alumina and ceria nanoparticles has given encouraging BSFC results, compared to diesel fuel POME20 at CR20 and 6% of EGR added with 100 ppm of Al2O3 and CeO2 nanoparticles was less than 15.15% and 6.06%. Overall it can be highlighted that with an aid of combined engine design (CR), control (EGR rate) and fuel reformulation approach the efficient utilization of POME biodiesel blended diesel fuel in the CI engines has been facilitated.

Optimization of operating parameters for diesel engine fuelled with bio-oil derived from cottonseed pyrolysis

In this study, the cottonseed as a potential renewable source for producing surrogate bio-fuel is elaborated. Indeed, this study included two stages, in which the extraction of the bio-oil from cottonseed through the intermediate pyrolysis process in a fixed-bed reactor was presented in the first stage. Furthermore, produced bio-oil has shown their physicochemical properties suitable for engine application. In the second stage, the analysis of performance (including brake thermal efficiency, brake-specific fuel consumption) and emission characteristics (including nitrogen oxides, carbon dioxide, unburnt hydrocarbon, carbon monoxide, and smoke opacity) of a water-cooled, 4-stroke, 1-cylinder diesel engine fueled with blends of bio-oil/diesel fuel in the case of changing compression ratio and engine load were carried out. More importantly, the response surface method technique was applied to optimize the operational parameters of the test engine. In conclusion, the validation experiments were performed to ensure the reliability of the obtained optimized results, indicating that the test engine operated with 5% bio-oil blended with 95% diesel fuel, a compression ratio of 18:1, and at 50% of engine load could offer the best performance and emission characteristics with a desirability factor of 0.617 and an error < 5% for the validated parameters.

Impact of compression ratio on combustion, performance and exhaust emissions of diesel engine fueled with Undi methyl ester-diesel and Undi ethyl ester-diesel blends

The current study emphasizes on the influence of nonedible, easily accessible Undi ester blended diesel in single-cylinder, four-stroke, naturally aspirated, direct-injection variable compression ratio diesel engine. All tests were accomplished by varying volumetric proportions of Undi methyl ester (UME) and Undi ethyl ester by 10%, 20%, 30%, 40%, and 50% and compression ratio (CR) from 16:1–20:1. The Undi esters consolidation to diesel, especially enhances brake thermal efficiency (BTE) and decreases brake specific energy consumption (BSEC) of the engine. In comparison with Diesel, ester fuel blends produce lower unburnt hydrocarbons (UHC), carbon monoxide (CO), and particulate matter (PM) emissions with the cost of higher oxides of nitrogen (NOX). With the increase in compression ratio from 16 to 20. All Undi ethyl ester diesel blends have on an average of 1.44% slightly improved brake thermal efficiency, 1.41% lower brake specific fuel consumption and it emits comparatively on an average 7.90% lesser carbon monoxide, 7.21% lower unburnt hydrocarbon, 0.59% lower particulate matter and 1.94% higher oxides of nitrogen emission than UME diesel blends with an increment in CR from 16 to 20. In addition, ester blends showed higher maximum In-cylinder pressure and heat release rate than commercial diesel. Undi ethyl ester blends show 0.82%, 1.08% on an average higher maximum In-cylinder pressure and heat release rate than UME Diesel blends when CR increased from 16 to 20. Undi ester Diesel blends are found to be utmost substitute to commercial diesel fuel in all features such as combustion, performance and emissions characteristics.

Vegetable oils as effective additives and replacements of diesel fuel in agriculture machinery engines

The article presents the results of experimental studies of possible partial replacement of traditional diesel fuel by biofuel. The term biofuel refers to a mixture of diesel fuel with vegetable oils such as palm or peanut oils. The optimal supply of vegetable oils is determining under conditions of preservation or deterioration of diesel engine performance in the range of 5 … 8%. The experiments suppose a diesel engine operation without any interfering within design or regulation of the diesel engine and its fuel equipment. Hydrogen peroxide or kerosene is used to improve the physicochemical properties of vegetable oils. It has been found that under these constraints, the optimal supply of palm oil is 20%. In case of peanut oil, experimentally found that its volume part in biofuel can be increased up to 40%. To provide an equal density and viscosity of the biofuel and the base diesel fuel 30% of diesel fuel were replaced by kerosene. In the range of low and medium engine loads, an emission of main toxic components of nitrogen oxides NOx, emission of solid carbon particles with exhaust gas C, carbon oxides changes insignificantly, and even decreases. The concentration of unburned hydrocarbons is significantly reduced. At engine loads above 50% for peanut oil and 75% for palm oil biofuels, presumably due to worse mixture formation, there is a sharp decrease in nitrogen oxide emissions and an increase in carbon monoxide concentrations.

Uncovering Hidden Dynamics of Natural Photonic Structures Using Holographic Imaging

In this method, the potential of optics and holography to uncover hidden details of a natural system's dynamical response at the nanoscale is exploited. In the first part, the optical and holographic studies of natural photonic structures are presented as well as conditions for the appearance of the photophoretic effect, namely, the displacement or deformation of a nanostructure due to a light-induced thermal gradient, at the nanoscale. This effect is revealed by real-time digital holographic interferometry monitoring the deformation of scales covering the wings of insects induced by temperature. The link between geometry and nanocorrugation that leads to the emergence of the photophoretic effect is experimentally demonstrated and confirmed. In the second part, it is shown how holography can be potentially used to uncover hidden details in the chemical system with nonlinear dynamics, such as the phase transition phenomenon that occurs in complex oscillatory Briggs-Rauscher (BR) reaction. The presented potential of holography at the nanoscale could open enormous possibilities for controlling and molding the photophoretic effect and pattern formation for various applications such as particle trapping and levitation, including the movement of unburnt hydrocarbons in the atmosphere and separation of different aerosols, decomposition of microplastics and fractionation of particles in general, and assessment of temperature and thermal conductivity of micron-size fuel particles.

Spray and engine performance of cerium oxide nanopowder and carbon nanotubes modified alternative fuel

This work aims to experimentally investigate and demonstrate the impacts of using Cerium Oxide (CeO2) and multi-wall carbon nanotube (CNT) blended with the alternative fuel, which is gas-to-liquid fuel (GTL) in this study, compared to diesel fuel (DF) on engine performance and study the macroscopic spray characteristics through a Constant Volume Vessel (CVV). Results demonstrate Cerium Oxide nanopowder and carbon nanotubes have very limited impacts on the average cone angle of gas-to-liquid fuel and diesel fuel. Cerium Oxide nanopowder and carbon nanotubes can individually reduce spray penetration during injection under a small ambient pressure when blended with diesel fuel, whilst the effect on gas-to-liquid fuel is less significant because the smaller density and lighter compositions of gas-to-liquid fuel promote its breakup process. In the post-injection period, carbon nanotubes increases the spray penetration of gas-to-liquid fuel, because gas-to-liquid fuel molecules are smaller than diesel fuel. Consequently, more gas-to-liquid fuel molecules stay inside the carbon nanotubes, which can only evaporate through two ends, and thus results in an overall reduced evaporation rate. Moreover, experiments also demonstrate that the average cone angle is independent of rail pressure, but it can be reduced by decreasing ambient pressure and increasing ambient temperature. During injection, both ambient pressure and rail pressure can influence the spray penetration, whilst after the end of injection, only ambient temperature has an effect on it. The engine experiment indicates that Cerium Oxide nanopowder can reduce nitrogen oxides, unburnt hydrocarbons and particulate number emissions simultaneously for both diesel fuel and gas-to-liquid fuel due to its catalysis at high-temperature conditions, whilst carbon nanotubes has a weaker effect on reducing nitrogen oxides and particulate number for gas-to-liquid fuel than diesel fuel.

A Review of Current Understanding of the Underlying Physics Governing the Interaction, Ignition and Combustion Dynamics of Multiple-Injections in Diesel Engines

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;This work is a comprehensive technical review of existing literature and a synthesis of current understanding of the governing physics behind the interaction of multiple fuel injections, ignition, and combustion behavior of multiple-injections in diesel engines. Multiple-injection is a widely adopted operating strategy applied in modern compression-ignition engines, which involves various combinations of small pre-injections and post-injections of fuel before and after the main injection and splitting the main injection into multiple smaller injections. This strategy has been conclusively shown to improve fuel economy in diesel engines while achieving simultaneous NO&lt;sub&gt;X&lt;/sub&gt;, soot, and combustion noise reduction - in addition to a reduction in the emissions of unburned hydrocarbons (UHC) and CO by preventing fuel wetting and flame quenching at the piston wall. Despite the widespread adoption and an extensive literature documenting the effects of multiple-injection strategies in engines, little is known about the complex interplay between the underlying flow physics and combustion chemistry involved in such flows, which ultimately governs the ignition and subsequent combustion processes thereby dictating the effectiveness of this strategy. In this work, we provide a comprehensive overview of the literature on the interaction between the jets in a multiple-injection event, the resulting mixture, and finally the ignition and combustion dynamics as a function of engine operational parameters including injection duration and dwell. The understanding of the underlying processes is facilitated by a new conceptual model of multiple-injection physics. We conclude by identifying the major remaining research questions that need to be addressed to refine and help achieve a design-level understanding to optimize advanced multiple-injection strategies that can lead to higher engine efficiency and lower emissions.&lt;/div&gt;&lt;/div&gt;

Strategies for Reduced Engine-Out HC, CO, and NOx Emissions in Diesel-Natural Gas and POMDME-Natural Gas Dual-Fuel Engine

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Dual-fuel engines employ precisely metered amounts of a high reactivity fuel (HRF) such as diesel at high injection pressures to burn a low reactivity fuel (LRF) such as natural gas, which is typically fumigated into the intake manifold. Dual fuel engines have demonstrated the ability to achieve extremely low engine-out oxides of nitrogen (NOx) emissions compared to conventional diesel combustion at the expense of unburned hydrocarbon (HC) and carbon monoxide (CO) emissions. At low engine loads, due to low in-cylinder temperatures, oxidation of HC and CO is very challenging. This results in both compromised combustion and fuel conversion efficiencies. The experimental campaign discussed in this paper involved a set of six engine control parameters that were strategically varied to find the best possible efficiency-emissions trade-offs for both diesel- and poly-oxy methylene dimethyl ether (POMDME)-natural gas dual fuel combustion on the University of Alabama single-cylinder research engine (SCRE) based on a PACCAR MX-11 heavy-duty engine platform. The control parameters investigated include: ((1)) Start of Injection (SOI1) of HRF, ((2)) percentage energy substitution (PES) of LRF, ((3)) introduction of the second HRF injection (SOI2), ((4)) split ratio, i.e., ratio of the duration of the first injection to the duration of the second injection, ((5)) rail pressure, and (6) intake pressure. At a fixed gross indicated mean effective pressure (IMEPg) of 5 bar (representative of typical low load operation) and an engine speed of 1339 rpm (“B speed” of the SCRE), SOI1 was varied to determine the lowest engine-out NOx point. Using that SOI1 as baseline and not-to-exceed (NTE) limits of: ((1)) Indicated specific NOx &amp;lt; 1 g/kWh, ((2)) maximum pressure rise rate (MPRR) &amp;lt; 10 bar/deg, and ((3)) coefficient of variation (COV) of IMEPg &amp;lt; 10%, the rest of the five control parameters were systematically varied. Based on HC and CO vs NOx emissions trade-offs, the best PES, SOI2, and split ratio were determined to achieve the lowest possible HC emissions. Subsequently, rail pressure sweeps showed minimal impact on performance and emissions between 500 bar and 1500 bar. Finally, reducing the intake pressure significantly reduced CO emissions to achieve the best overall set of operating parameters. Compared to the baseline diesel-natural gas case, HC and CO were reduced by ~88% and ~82%, respectively, in addition to ~21% improvement in the indicated fuel conversion efficiency. Whereas for POMDME-natural gas dual fuel combustion, HC and CO were reduced by ~85% and ~92%, respectively, in addition to ~20% improvement in the indicated fuel conversion efficiency. Furthermore, due to the high oxygen content of POMDME (47% m/m), engine-out soot emissions were reduced to zero measurable filter smoke number (FSN) for all conditions investigated.&lt;/div&gt;&lt;/div&gt;