Pressure Release Rate Research Articles

Experimental investigation of a novel quaternary blend for CRDI engine: performance, emission, and combustion characteristics

ABSTRACT The shortage-inflation of fossil fuels and aggravation of pollution intensity have initiated the search for innovative biofuel blends. Binary and Ternary fuels are studied for a long time. The use of biodiesel/vegetable oil up to 5–20% can replace fossil fuel with little modification in engine. However, to replace fossil fuel dependence up to 30–40% with little or no modification in engines is a challenge to researcher. This can be approached to evaluate a novel biofuel mix pattern called optimum Quaternary Blend by the experimental investigation. The main objective of the present research is to replace conventional Diesel with biofuels 30–40% with innovative fuel mix and lesser NOx-soot emission. In view of this, experimentally investigated combustion, emission, and performance behavior of single cylinder Common Rail Direct Injection (CRDI) engine fueled by quaternary blends combination of diesel (60–70 vol %), vegetable oil (Cotton Seed Oil – 5 vol% fixed), biodiesel (Mahua Biodiesel 5–25 vol %), and bio-alcohol (n-butanol 10–25 vol %). Further, to compare engine characteristics with D100% and D50B50%. Engine performance measures like brake thermal efficiency, specific energy consumption, emissions, and combustion characteristics such as rate of pressure rise (RPRR), combustion duration, CA50, CA90, mean gas temperature, combustion-chamber pressure, and net heat release rate are studied. It is noted that Diesel 60%, cotton seed oil 5% with mahua biodiesel 15–20%, and n-butanol 20–15% showed superior quaternary blend among all fuels. This optimum quaternary blend QB3-QB4 showed relatively higher brake thermal efficiency 8% more at lower specific energy consumption 10 MJ/kg about 29% less compared to other blends. Also, controlled combustion with rate of pressure rise 8.6 bar/deg CA about 14% less compared to other fuels. The NOx 10% less and smoke 2% less reported by optimum quaternary blends QB3 compared to other blends. However, CO emissions are noted least with marginal penalty in HC emissions.

Development of a reduced n-heptane/toluene/tetrahydrofuran mechanism for dual-fuel engine combustion prediction

Tetrahydrofuran (THF) is being proposed as a promising alternative fuel for internal combustion engines. However, the reaction chemistry of THF for multi-dimensional engine simulations has not been well established. In this study, a reliable n-heptane/toluene/THF mechanism was developed to simulate combustion of diesel and THF dual-fuel engine. Firstly, a reduced THF reaction mechanism was obtained by employing various mechanism reduction methods. Secondly, a combined mechanism was constructed based on decoupling methodology, which contained the reduced oxidation sub-mechanisms of n-heptane, toluene and THF, a reduced C2-C3 mechanism and a detailed H2/CO/C1 mechanism. Thirdly, the reaction rate constants of selected reactions involved in the combined mechanism were optimized and the newly developed reduced tri-component mechanism consisting of 65 species among 214 reactions. Subsequently, validations of the developed mechanism were performed using the previously published experimental results of ignition delay times in shock tubes, species mole fractions in laminar premixed flames and jet-stirred reactors, and laminar flame speeds. Meanwhile, dual-fuel engine experiments were conducted and new experimental data of in-cylinder pressure and heat release rate were also used to verify the developed mechanism. The validation indicates that the n-heptane/toluene/THF mechanism of this work can be applied for predicting the combustion process of diesel and THF dual-fuel engine.

Influence of fuel injection pressure and RME on combustion, NOx emissions and soot nanoparticles characteristics in common-rail HSDI diesel engine

‏ Manipulating in fuel injection strategies and introduce renewable fuel in diesel engine can provide clean combustion and lower pollutant emissions. The effect of fuel injection pressures (FIPs) and RME on combustion characteristics, NOx emissions and soot nanoparticle emissions when rapeseed methyl esters was used have been investigated at 1500 rpm and two brake mean effective pressure of 2.5 and 5 bar. A calibrated electrostatic mobility spectrometer (EMS) was used to measure the soot nanoparticle number size distributions. The peak cylinder pressure and heat release rates were evaluated when the FIP increased for all fuels studied. The results showed that further advanced in combustion with RME, meanwhile a shorter ignition delay from the fuel was exhibited in comparison with diesel fuel combustion under various FIP. Furthermore, the values of BSFC decreased by 3.7% and 17.8% from the RME combustion at high and low engine load, respectively. The reduction in NOx emissions was obtained when FIP increased during RME combustion in comparison with ULSD under low engine load. In contrast, RME generated higher NOx by 7% and lower soot nanoparticles by 27% compared to the ULSD under high engine load. RME combustion produced lower nucleation particle numbers in comparison with those emitted from ULSD under all engine operating conditions as well as the accumulation mode particles was higher for ULSD.

A numerical approach in the investigation of the effects of diethyl ether and ethanol mixtures on combustion characteristics and NO emissions in a DI diesel engine

In this study, the effects of adding ethanol and diethyl ether to diesel fuel on combustion characteristics and NO emissions were numerically investigated. 100% diesel fuel (D100) and by volume 90% diesel+10% ethanol blend (D90E10), 80% diesel+20% ethanol blend (D80E20), 80% diesel+10% ethanol+10% diethyl ether blend (D80E10DEE10) and 85% diesel+ 10% ethanol+5% diethyl ether mixture (D85E10DEE5) was used as fuel. Analyzes were carried out using a single cylinder direct injection diesel engine at 2000 and 3000 rpm engine speed conditions. AVL FIRE software was used for numerical study. In-cylinder pressure, cumulative heat release rate, turbulent kinetic energy (TKE), NO emissions and velocity distributions in the combustion chamber were investigated for five different fuel types. As a result, the in-cylinder pressure and heat release rate of ethanol and diethyl ether blended fuels were lower than diesel fuel at both speeds. This is due to the calorific value of the fuel. It was observed that NO emissions decreased as the ethanol content in the fuel increased. For both engine speeds, the highest TKE value was obtained in D90E10 mixed fuel, and the lowest value was found in D80E10DEE10 mixture fuel. Ethanol positively affected the turbulent kinetic energy. The flow rate of ethanol was higher than diesel and diethyl ether fuel.

Experimental and numerical engine cycle setup for a dual fuel hydrogen, methane, and hythane with diesel to assess the effect of water injection and nozzle geometry

AbstractIn this study, the potential of gaseous fuels such as hydrogen, methane, and hythane in combination with diesel fuel is assessed in a closed loop thermodynamic framework. An experimental test is conducted with basic diesel fuel and then the model is configured based on the realistic one‐cylinder diesel engine to evaluate the robustness and reliability of the simulation. The model is accurate in terms of in‐cylinder pressure, temperature, and heat release rate within the 3% error band. In principle, three blend cases of diesel50%—methane50%, diesel50%—hydrogen50%, and diesel50%—hythane50% are compared with baseline neat diesel from engine performance to emissions characteristics. For hythane and hydrogen‐involved fuels, the 10% water injection effect is analyzed as well to damp the high flammability and ignition intensity of hydrogen. The findings indicate that the entropy generation in hythane and hydrogen is markedly higher than in diesel case, while water injection can slightly decrease the entropy amount. It is shown that D50H50 has more fuel consumption in higher nozzle diameter (28% at 1 mm hole diameter), while in lower nozzle size range pure diesel fuel consumption dominates. The results revealed that D50Hy40W10 is particularly effective for elevated torque at lower nozzle hole values since the steam contributes toward maximized pressure and the exerted force. The increase of the nozzle number resulted in the CO content increase in the exhaust with the burning temperature reduction.

A computational study to analyze the effect of equivalence ratio and hydrogen volume fraction on the ultra-lean burning of the syngas-fueled HCCI engine

This computational study investigates the equivalence ratio and hydrogen volume fraction effect on the ultra-lean burning of the syngas-fueled homogeneous charge compression ignition (HCCI) engine. In this research, low calorific syngas, composed of different compositions of H2, CO, and CO2, is used as a fuel in the HCCI engine that is operated under an overly lean air-fuel mixture. ANSYS Forte CFD package with Gri-Mech 3.0 chemical kinetics was used to analyze the in-cylinder combustion phenomena, and the simulation results were validated with experimental tests in the form of in-cylinder pressure and heat release rate at different equivalence ratios.The results indicate that changing the equivalence ratio produces a negligible change in combustion phasing, while it positively impacts the combustion and thermal efficiency of this syngas-fueled HCCI engine under lean conditions due to the high burning rate in the squish region. Moreover, an increased equivalence ratio increases MPRR due to the rich mixture combustion. The results also represent that the high-volume fraction of H2 in syngas fuel causes an advanced burning phase, improves the combustion performance of the HCCI engine at all equivalence ratio conditions, and causes slightly high NOx emissions.

Low-speed performance compensation of a turbocharged natural gas engine by intake strategy optimization

Power output at the low engine speed is limited for natural gas engines, even though the turbocharging technology is used. In this paper, the intake system of a turbocharged spark-ignition natural gas engine with 4 valves (2 intake valves and 2 exhaust valves) was optimized by considering the intake strategy effects on the engine torque output and fuel economy improvement. Firstly, a 1D numerical model with hierarchical 1D/3D approach based on GT-SUITE was developed and validated against the experimental data of engine torque and fuel consumption rate. This approach combined detailed analysis of in-cylinder flow, charge movement and combustion. Secondly, different intake strategies were designed and their effects on the intake mass flow rate and in-cylinder mass during the intake process, the swirl flow, tumble ratio and the turbulent kinetic energy during the compression process, the flame propagation and temperature distribution evolution after the spark ignition, and the pressure and heat release rate were numerically investigated. The results showed that compared with the original intake strategy, the asynchronized intake strategy (the intake valves close earlier and the intake valve lifts are reduced, while two intake valves have different intake strategy) reduces the backflow in the end of intake stroke, improves the in-cylinder swirl flow, increases the maximum heat release rate and shortens the combustion duration, and it is believed to be the optimized intake strategy. Finally, different cam profiles corresponding to the numerically designed intake strategies were applied to the bench test engine and the dyno experiments showed that the optimized intake strategy improves the torque and reduces the brake specific fuel consumption by 41.42% and 8.1% respectively at a low engine speed of 1200 rpm.

A Comprehensive Study on the Effect of Dimethyl Carbonate Oxygenate and EGR on Emission Reduction, Combustion Analysis, and Performance Enhancement of a CRDI Diesel Engine Using a Blend of Diesel and Prosopis juliflora Biodiesel

This paper examines the combined effects of ignition improvers (DMC) and EGR on the CRDI small single-cylinder diesel engine’s performance, combustion, and emissions. In this experimentation, 20% (B20) optimal mix of Prosopis juliflora oil biodiesel (PJOB) and 5 ml dimethyl carbonate (DMC) additive was used as test fuel. The fuel handling CRDI system factors such as injection pressure set at 600 bar and injection timing set to 21 (bTDC) with a compression ratio of 16 were considered for the study. For the EGR trial, 20% of the exhaust gas was recirculated under various BMEP circumstances. The test was performed with and without EGR and DMC additive conditions like (i) diesel @ 0% EGR, (ii) diesel + 5 ml DMC @ 20% EGR, (iii) B20 @ 0% EGR, and (iv) B20 + 5 ml DMC @ 20% EGR at the engine power output. The amalgamation of dimethyl carbonate (DMC) additives and EGR reduces NOx and smoke while increasing CO and HC emissions. In addition, the DMC additive and EGR improve thermal efficiency slightly. The overall clubbing of DMC additive and EGR rate indicates better performance for the selected factors than a CRDI engine with a six-hole conventional mechanical fuel injection system. The outcome of the work clearly demonstrates that both the 5 ml DMC additive and the 20% EGR rate of the B20 blend show optimum values of BTE, BSFC, and EGT of 32.93%, 0.27 kg/kw·hr, and 310.89°C, which is closer to diesel. Factors of combustion like cylinder peak pressure (CPP) and heat release rate (HRR) are 70.93 bar and 58.13 J/deg. The tailpipe exhaust of NOx and smoke is 1681 ppm and 31.30 (% vol), which is less than diesel. The HC and CO levels are 93 ppm and 0.38 (% vol), respectively, which are significantly higher than diesel fuel.

Experimental assessment on characteristics of premixed charge compression ignition engine fueled with multi-walled carbon nanotube-included Tamanu methyl ester

The premixed charge compression ignition (PCCI) engine is developed to develop combustion at low temperatures to enhance engine efficiency and decrease exhaust emissions. This study was performed to compare the performance and emission characteristics of the PCCI mode-based engine operated with induction of ethanol in the inlet manifold and direct injection of multi-walled carbon nanotube (MWCNT)-blended Tamanu methyl ester (TME) at various proportions such as 10, 40, 70, and 100 ppm in comparison with the conventional CI engine fueled with diesel and TME. It was found that adding 100 ppm of MWCNT could provide significant improvements in the performance and emission characteristics of the PCCI engine because of its superior atomization, catalytic behavior, and high surface-to-volume ratio. As a result of comparison with conventional CI engine, brake thermal efficiency and brake-specific fuel consumption of PCCI engine running on MWCNT-blended TME was reduced by 4.12% and increased by 4.28%, respectively. Besides, emissions of hydrocarbon, carbon monoxide, nitrogen oxide, and smoke were reduced by 3.3%, 3.27%, 75%, and 45%, respectively. For combustion analysis, the CI engine has a higher in-cylinder pressure and heat release rate than the PCCI mode, which could be due to the PCCI mode's lower combustion and lean charge mixture. ICP and HRR of PCCI engines running on MWCNT-blended TME were reduced by 7.5% and 3.8%, respectively. In general, this current study reveals a significant reduction in pollutant emissions and an increase in engine performance by using a combined strategy between MWCNT-blended TME and low-temperature combustion mode like PCCI, which was previously unexplored.

RETRACTED: Optimization of variable compression ratio diesel engine fueled with Zinc oxide nanoparticles and biodiesel emulsion using response surface methodology

In the current work, the optimization of engine parameters like compression ratio and ZnO nano-particles along with diesel-biodiesel emulsion have been explored to improve the performance, combustion, and emissions of diesel engines. The novelty of current work is no studies on optimization of engine input variables such as compression ratio, biodiesel volume fraction, water percentage, and nanoparticle concentration. The engine's input parameters were chosen to be compression ratio, biodiesel-blend ratio, water percentage, and ZnO nanoparticle concentration for optimization using response surface methodology. In accordance with Central Composite Rotating Design matrix, the experiments on the diesel engine were carried out, while multi-objective optimization was also carried out for the optimum engine responses. The optimum output engine responses of brake thermal efficiency, brake specific energy consumption, carbon monoxide, unburnt hydrocarbons, oxides of nitrogen, in-cylinder pressure, and heat release rate were 30.75%, 13.92 MJ/kW.hr, 0.057%, 34.68 ppm, 717.28 ppm, 57.61 bar, and 51.26 J/°A, respectively. At optimal running conditions, it yielded a composite desirability of 0.8594. Furthermore, optimized engine parameters received 18.84 of compression ratio, 18.98% of biodiesel blend ratio, 5.71% of water emulsion, and 90.9 ppm ZnO nanoparticles concentration. Confirmation experiments were carried out to validate optimization results by engine input parameters to optimal values and found satisfactory. After the optimization engine output responses are evaluated experimentally, the acceptable range of error (<5%) was reported.

Experimental study of gliding arc plasma-assisted combustion in a blast furnace gas fuel model combustor: Flame structures, extinction limits and combustion stability

As an essential by-product of the iron and steel enterprises, blast furnace gas fuel is used as an alternative fuel for gas turbine combustion to increase economic effect. However, the less combustible components and low heat value of BFG fuel make the combustion in combustor very challenging. In this paper, a gliding arc plasma was employed to assist the blast furnace gas /air combustion with different equivalence ratio. Flame chemiluminescence, the pressure and heat release rate pulsation were recorded simultaneously for showing the flame characteristics of blast furnace gas. The experimental result demonstrates that there are six flame structures in the combustion process of blast furnace gas fuel: A stable flame with short U-shaped (SS-Flame), a vertical oscillating flame (VO-Flame), a stable flame with long U-shaped (SL-Flame), a special gourd-shaped flame (SG-Flame), a lifted flame (L-Flame) and a continuous extinct flame (CE-Flame). According to characteristics of flame structures before flameout, all cases can be divided into three types of extinction modes: I: Direct extinction, II: Oscillation extinction, III: Lifted extinction. The equivalence ratio of extinction limits at the low volume flow rate of air is more likely to be extended by gliding arc plasma than those at the high volume flow rate of air. The pressure and heat release rate pulsation experiment result shows that the violent oscillation of the heat release can be one of the prediction indexes of the flameout of blast furnace gas fuel. In all cases, the pressure pulsation of blast furnace gas fuel combustion is ± 10 Pa, and there is no obvious dominant frequency of heat release pulsation. The amplitude of heat release rate decreases from 0.04 V to 0.01 V with gliding arc plasma addition at φ = 0.7 (E-1 case). Meanwhile, the flame structure of blast furnace gas fuel changes from VO-Flame to SS- Flame due to the gliding arc anchoring the flame root.

Effect of cetane coupled with various engine conditions on diesel engine combustion and emission

Tests to study the effect of five different cetane number (CN) diesel fuels (CN of 51, 53.9, 55.3, 57.4, and 59.3) coupled to multiple operating conditions (multiple speeds and loads) on diesel engine performance in a single diesel engine. The results showed that at 25% load, the onset of combustion heat release was delayed with decreasing CN, and the in-cylinder pressure and heat release rate increased. However, the CN = 53.9 fuel chain alkane content was the highest, which led to the early onset of combustion; as the load continued to grow, the effect of CN on the beginning of heat release combustion became smaller. The values of brake specific fuel consumption (BSFC) and brake thermal efficiency (BTE) depend on the calorific value and CN of the fuel. The lower CN results in higher NOx, HC, and CO emissions, especially at low load conditions, where CN changes on emissions are more pronounced. As the load increases, the peak number concentration and total mass of particulate matter (PM) show a trend of increasing and then decreasing. The peak number concentration corresponds to the particle size-shifting toward the small particle size. The engine load change on PM emission is more significant than speed change.

Combustion analysis of higher order alcohols blended gasoline in a spark ignition engine using endoscopic visualization technique

The experimental study was carried out on the port fuel injection system installed spark-ignition engine fuelled by 1.5%, 3%, and 5% higher order alcohol such as 1-hexanol and 2-heptanol blended gasoline. In this study, the endoscopic combustion visualization technique was employed to compare and analyze the changes observed in the spatial flame characteristics between the alcohol blends and sole gasoline. The Correlated Colour Temperature (CCT) method was used to predict the flame temperature distribution from the captured flame images. Also, the effect of blending alcohols on engine combustion, performance, and emission characteristics was studied. The endoscopic results revealed that the flame spread region with respect to different CA positions increases with the alcohol blending ratio in the sole gasoline at the early and middle stages of the combustion. Further, the engine characteristics study revealed that 5% hexanol and heptanol blends gave a brake thermal efficiency of 25.8% and 25.7%, respectively, which were higher than sole gasoline, having 24.8% at full load. In addition, it was observed that the early start of combustion (SoC) and a faster burn rate associated with alcohol blends raise the cylinder pressure and heat release rates (HRRs) and thereby result in higher peak pressure and HRR with slight advancement in the CA position. At 8 kW, the CO and HC emission of 5% 1-hexanol and 2-heptanol blends was decreased by about 10.3% and 13.7%, and 9.5% and 8%, respectively, and NO emission decreased slightly with a rise in alcohol concentration in the mix when compared to gasoline.

Performance and environmental impact assessment of diesel engine operating on high viscous punnai oil-diesel blends.

The increasing demand for energy consumption because of the growing population and environmental concerns has motivated the researchers to ponder about alternative fuel that could replace diesel fuel. A new fuel should be cheaply available, clean, efficient, and environmentally friendly. In this paper, the engine operated with neat punnai oil blends with diesel was investigated at various engine load conditions, keeping neat punnai oil and diesel as base fuels. The performance indicators such as brake specific energy consumption (BSEC), brake thermal efficiency (BTE), and exhaust gas temperature (EGT); emission indicators such as carbon monoxide (CO), oxides of nitrogen (NOx), and smoke opacity; and combustion parameters like cylinder pressure and heat release rate were examined. The brake thermal efficiency of diesel is 29.2%, whereas it was lower for neat punnai oil and its blends at peak load conditions. Concerning the environmental aspect, oxides of nitrogen emission showed a decreasing trend with higher smoke emissions for Punnai oil blends. Detailed combustion analysis showed that on smaller concentrations of punnai oil in the fuel blend, the duration of combustion has improved significantly. However, for efficiency and emissions, the P20 (20% punnai oil and 80% diesel) blend performs similar to that of diesel compared to all other blending combinations. When compared with diesel, the P20 blend shows an improvement in BSEC by 26.37%. It also performs closer in HC emission, a marginal increase in smoke opacity of 4% with reduced NOx and CO2 emission of 7.9% and 4.65% respectively. Power loss was noticed when neat punnai oil and higher blends were used due to the high density and low calorific value of punnai oil blends which leads to injecting more fuel for the same pump stroke.

Theoretical investigation the effect of Low-Temperature reformed products of gasoline on engine combustion and emission at variable loads

Gasoline was reformed by an external fuel reforming system at the reforming temperature from 488 K to 638 K. And the numerical simulation study was carried out using CONVERGE to study the effects of reformed products at different reforming temperatures on engine combustion and emission performance with different loads. The results showed that the reforming temperature has a great influence on the composition of the reformed products. With the increase of reforming temperature, gasoline gradually generated CH4, C2H4, CH3CHO and other species, accompanied by CO, CO2 and other products. The addition of reformed products advanced the combustion phase, reduced the cylinder pressure and combustion heat release rate, and affected the combustion state in the cylinder. Meanwhile, the addition of reformed products would reduce the emission of exhaust gas under medium and high load conditions, but the emissions would increase under low load condition. Therefore, reasonable selection of low-temperature reformed products could make the engine achieve clean and efficient combustion under different load conditions.

Artificial neural networks model for predicting the behavior of different injection pressure characteristics powered by blend of biofuel‐nano emulsion

AbstractThis investigation deals with the usage of graphene oxide (GO) nanoparticles with orange peel biodiesel in a conventional CI engine. The different fuel blends used for this experiment are biodiesel 10% + diesel 80% + ethanol 5% + surfactant 5% + GO 50 ppm (B10), biodiesel 20% + diesel 70% + ethanol 5% + surfactant 5% + GO 50 ppm (B20), biodiesel 50% + diesel 40% + ethanol 5% + surfactant 5% + GO 50 ppm (B50) and B100. The addition of ethanol has dual benefits for improving the vaporization of fuel blends and reduction of oxides of nitrogen (NOx) emission. Span80 and Tween80 were chosen as surfactants based on hydrophilic‐lipophilic balance numbers. It is useful for improving the homogeneity of immiscible fuel blends. From this study, the injection pressure (IP) was varied from 180, 200 to 220 bar for better atomization characteristics of nano additive biodiesel blend. The experimental results indicated that an increase in the percentages of biodiesel beyond 20% in the blend, NOx increases, and hydrocarbon (HC) and carbon dioxide (CO) emissions were found to be decreased. It is also observed that the highest brake thermal efficiency (BTE) was found for fuel 20 at the IP of 220 bar. The addition of nano additive has a great influence on fuel droplets and reduction of NOx emission levels. B20 blend was found to higher cylinder pressure and heat release rate when compared to other nano additive blends. Finally, indicated that the nano additive B20 blend is a better alternative to conventional fuel in unmodified CI engines. The RMSE value for the BTE, brake‐specific energy consumption (BSEC), CO, HC, NOx, and smoke is obtained to be 0.036, 0.0216, 0.044, 0.041, 0.0446, and 0.0435, respectively. The mean absolute percentage error value for the BTE, BSEC, CO, HC, NOx, and smoke is obtained to be 1.12, 0.84, 3.04, 4.12, 1.71, and 0.97, respectively.

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.

Modelling fire smoke dynamics in a stairwell of high-rise building: Effect of ambient pressure

In a high-rise building fire, vertical shafts are the main paths for hot smoke to spread to multiple floors, posing a significant fire hazard. In this work, the large eddy simulation (LES) was applied to simulate smoke dynamics in a full-scale stairwell and study the influence of ambient pressure and heat release rate (HRR). The results have shown that the air mass flow rate into the stairwell decreases as ambient pressure drops on account of the lower air velocity and density and increases with HRR because of the stronger stack effect and increased smoke production. An equation incorporating ambient pressure and HRR is proposed for predicting the air mass flow rate. The temperature of hot smoke near the fire source increases with the reduced ambient pressure, while on the floors away from the fire source, the temperature decreases due to the higher temperature attenuation at a lower pressure. In addition, an empirical model is put forward for predicting the rising time of the smoke plume considering ambient pressure. The results could increase the basic understanding of smoke movement mechanisms and contribute to engineering applications of smoke control in high-rise building fires under reduced ambient pressure conditions.

Experimental Investigation of Combustion Characteristics of a Spark Ignition Engine Fueled with Methanol-Gasoline Blends (M15 and M85)

Combustion characteristics of a 2.8 kW, constant speed, spark ignition engine fuelled with methanol-gasoline blends (M15 and M85) were studied. It was observed that the maximum in-cylinder pressure and maximum heat release rate with M85 were almost like gasoline while these values were significantly lower with M15. The flame development duration was 30.5% and 5.5% shorter at lower and higher load respectively with M85 as compared to gasoline. In addition to this, the flame propagation duration was shorter by 37% and 14.28% at lower and higher load with M85. Similar results were obtained with M15 blend. The crank angle for fifty percent mass burnt fraction was near to the top dead centre of engine with both the blends as compared to gasoline. The methanol-gasoline fuelled spark ignition engine’s important combustion characteristics including heat release rate, cumulative heat release, combustion duration, flame development, propagation and laminar flame velocity are analysed in detail.

Investigation on combustion, performance and emission characteristics of a diesel engine fueled with diesel/alcohol/n-butanol blended fuels

In this paper, the effects of diesel/methanol, diesel/ethanol, diesel/n-butanol, diesel/methanol/n-butanol, and diesel/ethanol/n-butanol blended fuels with different alcohol substitution ratios (ASR) on the combustion, performance, and emission characteristics of a diesel engine were studied and compared. Firstly, a three-dimensional computational fluid dynamics (CFD) model was established and verified by the experiment results at 2000 rpm and 25%, 50%, 75%, and 100% loads. In addition, an improved chemical kinetic mechanism, including 81 species and 358 reactions, was used to simulate the combustion process. The combustion, performance, and emission characteristics were investigated. The results showed that compared with pure diesel, the cylinder pressure, cylinder temperature, and heat release rate (HRR) were significantly increased with the increase of ASR, the ignition delay was increased and the combustion duration was decreased. Among them, 80% diesel + 10% methanol + 10% n-butanol (D80M10B10) blended fuel was the most beneficial to improving cylinder pressure, prolonging ignition delay, and shortening combustion duration. Compared with diesel, the peak cylinder pressure, peak cylinder temperature, and peak HRR of D80M10B10 were increased by 2.86%, 2.68%, and 215.26% respectively. In addition, the addition of alcohol fuels decreased soot, HC, and CO emissions. However, NOx emission increased. Comprehensive diesel combustion, performance, and emission characteristics, the best blending ratio was D80M10B10 blended fuel.