An artificial neural network approach to modelling absorbent asphalts acoustic properties

Sound-absorbing asphalts are particularly useful for reducing noise emissions from vehicular traffic. This solution is perfectly suited for urban areas, in fact the use of sound-absorbing asphalt represents a noise control measure with a negligible environmental impact. In the present work, the results of an experimental investigation on sound-absorbing asphalts were reported. First, the characteristics of the sound-absorbing asphalts used were experimentally found. Then, the measurements of the sound absorption coefficient of the asphalt specimens were investigated. In the final part, numerical simulation model with artificial neural networks of the acoustic coefficient were compared with the data obtained from the measurements. The neural network model showed good Pearson correlation coefficient values (0.894) which can be used with good accuracy to predict the sound absorption coefficient

New novel thermal insulation and sound-absorbing materials from discarded facemasks of COVID-19 pandemic

AbstractDue to the COVID-19 pandemic, people were encouraged and sometimes required to wear disposable facemasks, which then are discarded creating an environmental problem. In this study, we aim at investigating novel ideas to recycle wasted facemasks in order to lower the environmental impact. An experimental study has been carried out to investigate the possibility of using discarded masks for thermal insulation and sound absorption. The wasted masks are simulated by new masks, which stripped off the nose clips, elastic ear loops and are heated to 120 °C for one hour to kill any biological contaminants. The masks are also melted to investigate their thermal insulation and sound absorption properties. Results show that the thermal conductivity coefficients of the loose and melted masks are 0.03555 and 0.08683 W/m K, respectively, at room temperature of about 25 °C. Results show also that the sound absorption coefficient for loose masks is above 0.6 for the frequency range 600–5000 Hz. The loose facemasks are found to be thermally stable up to 295 °C, elastic ear loops at 304.7 °C, and the composite (melted) facemasks at 330.0 °C using the thermo-gravimetric analysis. Characterization of the facemask’s three-layer fibers and the composite (melted) samples is obtained using scanning electron microscopy (SEM). The three-point bending test is obtained for the composite specimens showing good values of flexural stress, flexural strain, and flexural elastic modulus. These results are promising about using such discarded masks as new thermal insulation and sound-absorbing materials for buildings replacing the synthetic or petrochemical insulation materials.</jats:p

Development and characterization of sound-absorbing materials produced from agricultural wastes in Saudi Arabia

Green materials can be a valid alternative to traditional ones as they are produced and disposed without damaging the environment. In the present paper, materials developed from agricultural wastes from Saudi Arabia are presented. The natural materials considered are: date palm tree leaves, wheat straw fibres and eucalyptus, globules leaves. The values of the sound absorption coefficients of these biodegradable natural materials are reported. The sound absorption coefficients were measured with the impedance tube in the frequency range 200 Hz - 2,000 Hz. Sound absorption coefficients resulted greater than 0.5 at frequencies above 900 Hz for almost all the samples, which indicates good sound absorption behaviour. The paper concludes with some considerations about the potential use of these materials in room acoustics

Investigation on particulate emissions and combustion characteristics of a common-rail diesel engine fueled with Moringa oleifera biodiesel-diesel blends

In this study, a study of the effects of Moringa Oil Biodiesel (MOB) biodiesel-diesel blends on the engine's performance, exhaust particulate matter, gaseous emissions and combustion characteristics was carried out in a multi-cylinder high-pressure common-rail diesel engine. The experiment involved the use of baseline diesel and several MOB blends (MOB10, MOB20, MOB30 and MOB50) as the fuel for the diesel engine. The results concluded that the engine torques and brake power produced by all of the MOB blends is smaller to the baseline diesel. However, both the MOB blends and baseline diesel produced similar brake thermal efficiency (BTE). It is noticed that the brake specific fuel consumption (BSFC) of all MOB are indicating deterioration, but showing an improvement in the brake specific energy consumption (BSEC). Besides, the peak cylinder pressure and peak HRR indicated a trend of declination with the increasing biodiesel blend ratio. Furthermore, all MOB has shown a great improvement in the emission of carbon monoxide (CO), smoke and particulate matter (PM), except nitrogen oxides (NOx). In short, Moringa oil is suitable to use as a source of biodiesel fuel in the diesel engines without any engine modification needs to be done

Impact of two-stage injection fuel quantity on engine-out responses of a common-rail diesel engine fueled with coconut oil methyl esters-diesel fuel blends

Two-stage injection with different biodiesel percentage is investigated where first and second injections were implemented with different SOI timings at various mass ratio under constant speed of 2000 rpm and 60 Nm of torque. The results reveal that maximum BTE of 32.4% and minimum BSFC of 245.5 g/kWh can be achieved simultaneously with injection mass ratio of 50:50 at advanced SOI timing using baseline diesel. A considerably lower level of NOx below 90 ppm is achievable via late SOI timing by using B20 or B50 biodiesel blends with injection mass ratio of 25:75. Specifically, the lowest NOx of 82 ppm can be achieved with smoke emission level still remains below 5% when B50 biodiesel blend and 25:75 injection mass ratio is tested. The highest reduction of 5.3% of smoke compared to diesel was achieved when B50 was used with 50:50 mass ratio at retarded SOI of 2°ATDC. It was found that simultaneous NOx and smoke reduction compared to that of fossil diesel is feasible with the application of B50 biodiesel blend and execution of retarded SOI timing and injection mass ratio of 25:75. Lastly, two-stage fuel injection is a practical strategy to simultaneously decrease NOx and smoke emissions

Impact of fatty acid composition and physicochemical properties of Jatropha and Alexandrian laurel biodiesel blends: An analysis of performance and emission characteristics

This experimental investigation deals with the effects of fatty acid methyl ester (FAME) composition and the physicochemical properties of biodiesel on engine performance and emissions. FAME compositions have a considerable influence on the physical and chemical properties of biodiesel, such as density, viscosity, heating value, cetane number (CN), oxidation stability, and cold flow properties. The performance and emissions of a four-cylinder turbocharged diesel engine were studied under varying speeds and full load condition. For this investigation, 10% and 20% blends of Jatropha (Jatropha curcas), Alexandrian laurel (Calophyllum inophyllum), and palm biodiesels (JB, ALB, and PB, respectively) were used, and the results were compared with that of the B5 fuel (95% diesel and 5% palm biodiesel). The content of saturated fatty acid (methyl palmitate) for ALB and JB was found to be 23.3% and 20.4% higher respectively than that for PB. In total, PB showed 19.8% higher saturation than JB, while ALB showed 7.3% higher saturation than JB because of their higher content of longer chain saturated fatty acid (methyl stearate). The CNs of all three biodiesels increased with the increase of carbon chain length and saturation level, whereas iodine value and saponification value decreased with the increase of saturation level. An average of 2.8% and 4.5% brake power reduction were observed in the case of 10% and 20% biodiesel blends respectively. Brake specific fuel consumption increased in the range of 6%–20% compared with B5 fuel, whereas carbon monoxide and hydrocarbon emissions decreased significantly. Nitrogen oxide emissions increased in the range of 9%–23% for the 10% and 20% biodiesel blends with respect to B5 fuel

Influences of ignition improver additive on ternary (diesel-biodiesel-higher alcohol) blends thermal stability and diesel engine performance

Pentanol is a long chain alcohol produced from renewable sources and considered as a promising biofuel as a blending component with diesel or biodiesel blends. However, the lower cetane number of alcohols is a limitation, and it is important to increase the overall cetane number of biodiesel fuel blends for efficient combustion and lower emission. In this consideration, ignition improver additive 2-ethylhexyl nitrate (EHN) were used at a proportion of 1000 and 2000 ppm to diesel-biodiesel-pentanol blends. Experiments were conducted in a single cylinder; water-cooled DI diesel engine operated at full throttle and varying speed condition. The thermal stability of the modified ternary fuel blends was evaluated through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis, and the physic-chemical properties of the fuel as well as engine characteristics were studied and compared. The addition of EHN to ternary fuel blends enhanced the cetane number significantly without any significant adverse effect on the other properties. TGA and DSC analysis reported about the improvement of thermal characteristics of the modified blends. It was found that, implementing ignition improver make the diesel-biodiesel-alcohol blends more thermally stable. Also, the brake specific fuel consumption (BSFC), nitric oxides (NO) and smoke emission reduced remarkably with the addition of EHN. Introducing EHN to diesel-biodiesel-alcohol blends increased the cetane number, shorten the ignition delay by increasing the diffusion rate and improve combustion. Hence, the NO and BSFC reduced while, carbon monoxide (CO) and hydrocarbon (HC) emissions increased slightly

Effect of two-stage injection dwell angle on engine combustion and performance characteristics of a common-rail diesel engine fueled with coconut oil methyl esters-diesel fuel blends

Diesel engine is widely used as prime mover due to its high thermal efficiency. Usage of renewable biodiesel in diesel engine is also widely studied due to its potential in reducing emission and as a replacement of conventional diesel. Biodiesel performance could be improved by blending it with petroleum diesel besides introducing appropriate injection strategies. In this experiment, the effect of percentage of biodiesel blends and injection strategies such as variations in start of injection (SOI) timing and dwell angle on diesel engine performance were investigated. The test engine used is four-stroke turbocharged direct injection diesel engine. Results show that exhaust emissions, engine performance and combustion characteristics are substantially affected by biodiesel blending ratio and SOI timing but slightly influenced by two-stage injection dwell angle. Biodiesel blends percentage could be raised to improve NOx and smoke emissions. Even though SOI performed at a later timing could reduce NOx emission, smoke emission increased. Dwell angle between two successive injections could be prolonged to lower the effect of the increase in smoke emission. It could also be inferred that by setting a proper SOI timing and dwell angle under two-stage injection scheme when suitable biodiesel blend is used, the engine performance could be optimized