Experimental and numerical study of an internal combustion engine coolant flow distribution

Ujednačeno hlađenje svih cilindara u motoru s unutarnjim izgaranjem predstavlja trajni izazov za mnoge inženjere i istraživače. Različiti tok i brzina strujanja rashladnog sredstva na sličnim mjestima u cilindrima može rezultirati prevelikim ili preslabim hlađenjem nekih mjesta. U ovom se radu želi dobiti motor s ujednačenijim hlađenjem. U tu su svrhu najprije riješene jednadžbe protoka 1D i 3D kako bi se dobili numerički podaci o brzini, tlaku i temperaturi na različitim mjestima postojećeg motora. Tada se primijenila metoda mjerenja brzine fotogramom čestica (Particle Image Velocimetry - PIV) kako bi se na providnom poklopcu glave cilindra izrađenom od pleksiglasa provjeravale numeričke simulacije. Nakon provjere, u svrhu postizanja odgovarajućeg hlađenja, primijenile su se neke strategije kao na primjer male modifikacije na ulazu i izlazu rashladnog sredstva u motor kao i brzine protoka sredstva, a to je rezultiralo ujednačenijim hlađenjem, dakle onemogućavanjem prevelikog ili premalog hlađenja.Uniform cooling of all cylinders in an Internal Combustion Engine has been a continual challenge of many engineers and researchers. Different flow rate and velocity of coolant at similar locations of cylinders may cause some regions to be overcooled whereas some to be undercooled. In this study more uniform cooling engine is desired. To do this, at first the governing equations of the flow were solved 1D and 3D to obtain the velocity, pressure and temperature at various points of an existing engine numerically. Then Particle Image Velocimetry (PIV) method on a transparent cylinder head made of Plexiglas was used to validate the numerical simulations. After validation, in order to reach intelligent cooling, some strategies such as small modifications in the engine coolant inlet and outlet along with its flow rates were applied that resulted in more uniform cooling which in turn prevents any over and under cooling

Effects of compression ratio of bio-fueled SI engines on the thermal balance and waste heat recovery potential

In internal combustion engines, a significant share of the fuel energy is wasted via the heat losses. This study aims to understand the heat losses and analyze the potential of the waste heat recovery when biofuels are used in SI engines. A numerical model is developed for a single-cylinder, four-stroke and air-cooled SI engine to carry out the waste heat recovery analysis. To verify the numerical solution, experiments are first conducted for the gasoline engine. Biofuels including pure ethanol (E100), E15 (15% ethanol) and E85 (85% ethanol) are then studied using the validated numerical model. Furthermore, the exhaust power to heat loss ratio (Q˙ex/Q˙ht) is investigated for different compression ratios, ethanol fuel content and engine speed to understand the exhaust losses potential in terms of the heat recovery. The results indicate that heat loss to brake power ratio (Q˙ht/W˙b) increases by the increment in the compression ratio. In addition, increasing the compression ratio leads to decreasing the Q˙ex/Q˙ht ratio for all studied fuels. According to the results, there is a direct relationship between the ethanol in fuel content and Q˙ex/Q˙ht ratio. As the percentage of ethanol in fuel increases, the Q˙ex/Q˙ht ratio rises. Thus, the more the ethanol in the fuel and the less the compression ratio, the more the potential for the waste heat recovery of the IC engine. Considering both power and waste heat recovery, the most efficient fuel is E100 due to the highest brake thermal efficiency and Q˙ex/Q˙ht ratio and E85, E15 and E00 (pure gasoline) come next in the consecutive orders. At the engine speeds and compression ratios examined in this study (3000 to 5000 rpm and a CR of 8 to 11), the maximum efficiency is about 35% at 5000 rpm and the compression ratio of 11 for E100. The minimum percentage of heat loss is 21.62 happening at 5000 rpm and the compression ratio of 8 by E100. The minimum percentage of exhaust loss is 35.8% happening at 3000 rpm and the compression ratio of 11 for E00. The most Q˙ex/Q˙ht is 2.13 which is related to E100 at the minimum compression ratio of 8

High-Voltage Pulse Generators for Electroporation Applications: A Systematic Review

In recent years, the use of electroporation process has attracted much attention, due to its application in various industrial and medical fields. Electroporation is a microbiology technique which creates tiny holes in the cell membrane by the applied electric field. The electroporation process needs high-voltage pulses to provide the required electric field. To generate high-voltage pulses, a pulse generator device must be used. High-voltage pulse generators can be mainly divided into two major groups: Classical pulse generators and power electronics-based pulse generators. As their name suggests, the first group is associated with the primary and elementary pulse generators like Marx generators, and the second group is associated with the pulse generators that have been updated with the advancement of power electronics like Modular Multilevel Converters. These two major groups are also divided into several subgroups which are reviewed in detail in this paper. This study reviews the literature presented in the field of pulse power and pulse generators proper for the electroporation process and addresses their strengths and weaknesses. Several tables are provided to highlight and discuss the characteristics of each subgroup. Finally, a comparative study among different groups of pulse generators is performed which is followed by a classification performance analysis

A smart load-speed sensitive cooling map to have a high- performance thermal management system in an internal combustion engine

Considering the fact that electrification is increasingly used in internal combustion engines, this paper aims at presenting a smart speed-load sensitive cooling map for better thermal management. For this purpose, first, thermal boundary conditions for the engine cooling passage were obtained by thermodynamic and combustion simulation. Next, the temperature distribution of the cooling passage walls was determined using conjugate heat transfer method. Then, the effect of engine load on wall temperature distribution was investigated, and it was observed that in the conventional mode where the cooling flow is only affected by the engine speed, the engine is faced with over-cooling and under-cooling. Therefore, the optimum flow for cooling the engine was achieved in such a way that the engine is hot enough and kept free from damage, while the engine has a more uniform temperature distribution. These calculations were performed by considering the boiling phenomenon. The results showed using the cooling map leads to a significant reduction in coolant flow, which in turn reduces the power consumption of the water pump and size of the radiator. Moreover, fuel consumption, hydrocarbon emission production, and the needed power of the coolant pump are enhanced by 2.1, 8.6, and 44.3%, respectively.Irankhodro Powertrain Company (IPCo)http://www.elsevier.com/locate/energy2022-04-22hj2021Mechanical and Aeronautical Engineerin

Caractérisation du potentiel de dégradation de matières organiques naturelle (litière) et anthropique (HAP) par les communautés microbiennes issue du milieu littoral méditerranéen

Les écosystèmes méditerranéens littoraux sont soumis à divers stress environnementaux naturels (stress hydrique et halin) et anthropiques susceptibles de s'intensifier dans les prochaines décennies. Dans ce contexte, le fonctionnement des communautés microbiennes - encore très peu étudiés dans de tels milieux - était important à préciser. L'effet du stress halin sur la transformation de la matière organique dans la litière de pin d'Alep issues des calanques de Marseille a été estimé ainsi que le potentiel de biodégradation d'un polluant chronique, l'anthracène, un Hydrocarbures Aromatiques Polycycliques. Différents approches in situ, ex situ et in vitro ont été utilisées en associant différentes méthodes afin de mesurer l'état fonctionnel du milieu (activités enzymatiques, respirométrie basale), la diversité fonctionnelle microbienne (Catabolic Level Physiological Profile), la biomasse microbienne et l'évolution chimique de la matière organique (RMN du solide du 13C). En mésocosmes, les laccases, induites par la présence d'anthracène, ont contribué à son oxydation et ont été séquencées par LC/MS/MS afin de déterminer les espèces fongiques à l'origine de leur synthèse. Les résultats montrent que certaines activités enzymatiques du cycle du carbone sont peu affectées par la salinité et l'apport d'anthracène. Toutefois la diversité fonctionnelle des communautés autochtones de litière de pin d'Alep issues de ces environnements est modifiée à une échelle micro-locale par l'effet marin. Par ailleurs les réponses fonctionnelles face à l'apport d'anthracène des communautés microbiennes de litières de pin d'Alep en zone continentale sont différentes de celles des zones littoralesMediterranean coastal ecosystems are subjected to various natural and anthropogenic environmental pressures which are supposed to be enhanced because of climatic changes. Little is known about microbial community functioning in such ecosystems. Our site of study is located in the Calanques of Marseille, a hot spot of biodiversity. The effect of salinity (via sea spray exposure) on microbial communities and their ability to transform organic matter in an Aleppo pine litter have been studied as well as the potential of autochthonous microorganisms to transform anthracene used as a polycyclic aromatic hydrocarbon model. To do so, different approaches (in situ, ex situ and in vitro experimental design) were used and we combined various methods such as enzyme activities (laccase, cellulase, phosphatase, lipase), CLPP (Biolog ECO and FF plates), respirometry (basal and induced) and litter chemical characterization (solid-state 13C NMR). Laccases were induced by anthracene in mesocosms and oxidized this compound (with anthraquinone as an intermediate). These enzymes were sequenced by LC/MS/MS to determine the fungal strains responsible for their production. We also found that enzyme activities were not strongly influenced by salinity or anthracene inputs. On the other hand, functional diversity was structured at a small-spatial scale. Moreover, functional responses of microbial communities from inland areas strongly differ from those of coastal areas regarding anthracene inputs since no laccase induction was observed in inland litter

A modified method based on arsenomolybdate complex to quantify cellulase activities : application to litters

In this study a simplified methodology adapted from that of Somogyi-Nelson is described in order to quantify cellulase activities in natural environments such as litters. We recommend (i) reducing drastically Na2SO4 amounts (from 90 to 4g) to improve solubility and (ii) reading absorbance at 870 nm since the highest values for the reduced arsenomolybdate complex were obtained for this wavelength

How do microlocal environmental variations affect microbial activities of a Pinus halepensis litter in a Mediterranean coastal area?

International audienceMediterranean coastal ecosystems suffer many different types of natural and anthropogenic environmental pressure. Microbial communities, major conductors of organic matter decomposition are also subject to these environmental constraints. In this study, our aim was to understand how microbial activities vary at a small spatio-temporal scale in a Mediterranean coastal environment. Microbial activities were monitored in a Pinus halepensis litter collected from two areas, one close to (10 m) and one far from (300 m) the French Mediterranean coast. Litters were transferred from one area to the other using litterbags and studied via different microbial indicators after 2, 5 and 13 months. Microbial Basal Respiration, qCO2, certain enzyme activities (laccase, cellulase, β-glucosidase and acid phosphatase) and functional diversity via Biolog microplates were assayed in litterbags left in the area of origin as well as in litterbags transferred from one area to the other. Results highlight that microbial activities differ significantly in this short spatial scale over time. The influence of microlocal conditions more intensified for litters situated close to the sea, especially during summer seems to have a stressful effect on microbial communities, leading to less efficient functional activities. However, microbial activities were more strongly influenced by temporal variations linked to seasonality than by location

Study of lead-induced neurotoxicity in cholinergic cells differentiated from bone marrow-derived mesenchymal stem cells

The developing brain is susceptible to the neurotoxic effects of lead. Exposure to lead has main effects on the cholinergic system and causes reduction of cholinergic neuron function during brain development. Disruption of the cholinergic system by chemicals, which play important roles during brain development, causes of neurodevelopmental toxicity. Differentiation of stem cells to neural cells is recently considered a promising tool for neurodevelopmental toxicity studies. This study evaluated the toxicity of lead acetate exposure during the differentiation of bone marrow-derived mesenchyme stem cells (bone marrow stem cells, BMSCs) to cholinergic neurons. Following institutional animal care review board approval, BMSCs were obtained from adult rats. The differentiating protocol included two stages that were pre-induction with beta-mercaptoethanol (BME) for 24 h and differentiation to cholinergic neurons with nerve growth factor (NGF) over 5 days. The cells were exposed to different lead acetate concentrations (0.1-100 mu m) during three stages, including undifferentiated, pre-induction, and neuronal differentiation stages; cell viability was measured by MTT assay. Lead exposure (0.01-100 mu g/ml) had no cytotoxic effect on BMSCs but could significantly reduce cell viability at 50 and 100 mu m concentrations during pre-induction and neuronal differentiation stages. MAP2 and choline acetyltransferase (ChAT) protein expression were investigated by immunocytochemistry. Although cells treated with 100 mu m lead concentration expressed MAP2 protein in the differentiation stages, they had no neuronal cell morphology. The ChAT expression was negative in cells treated with lead. The present study showed that differentiated neuronal BMSCs are sensitive to lead toxicity during differentiation, and it is suggested that these cells be used to study neurodevelopmental toxicity

The importance of water availability in the reaction equilibrium of hydrolases in forest litters from a Mediterranean area: a study on lipases

International audienceWater is one of the main variables affecting the carbon cycle (carbon storage or assimilation) in soils or litters from the Mediterranean area, though in most studies it has been considered via soil moisture measurements only. Here, we investigated the effect of water availability as characterized by water activity, a w , on the equilibrium of enzyme reactions (hydrolysis/synthesis) for litters from three species characteristic of the Mediterranean area (Quercus pubescens L, Q. ilex L. and Pinus halepensis L.). Lipases were used as models and an organic phase was used as the reaction medium to adjust water amount. We found that the activities of hydrolysis/transesterification increased with a w , showing that both can occur at the same a w in litter. Furthermore, these lipase activities in litter decreased for a w close to 1, which has been described with purified lipases in organic media, indicating potential enzyme aggregation. Variations in a w with moisture were studied with sorption isotherms, which were found to be similar (isotherm type 2) for all the studied litters. Water activity is a crucial indicator for soils under hydric stress at small water contents, which should be considered for describing more precisely enzyme functioning and giving valuable information about carbon dynamics in soils or litters

Effects of anthracene on microbial activities and organic matter decomposition in a Pinus halepensis litter from a Mediterranean coastal area

Due to increasing atmospheric pollution, it has become highly important to investigate how anthropic chronic contaminations may affect ecosystem functioning. To explore the effect of polycyclic aromatic hydrocarbons (PAHs) on indigenous microbial activities, anthracene was used as a model PAH in a mesocosm experiment with Pinus halepensis litter from the Massif of Marseilleveyre (Marseille, France). The effects of anthracene on microbial activities were followed after 1- and 3- month incubations by: Catabolic Level Physiological Profile (CLPP) using ECO and FF plates and four enzyme activities (cellulase. beta-glucosidase, acid phosphatase and lipase), Moreover the chemical variations in organic matter were evaluated by solid-state C-13 NMR and C/N ratio. These experiments revealed an increase in cellulase, beta-glucosidase and phosphatase activities and a decrease in lipase activities after a 3-month incubation in the presence of anthracene. Principal Component Analysis (PCA) from CLPP showed that bacterial catabolic diversity is more influenced than that of fungal communities by anthracene. Correlation between both chemical and biological indicators revealed that the increase in lignocellulolytic enzymes (cellulase, laccase and beta-glucosidase) was significantly correlated to the decrease in phenolic compounds. In addition, aromaticity ratio also decreased in the presence of anthracene suggesting that transformation of the recalcitrant part of organic matter was enhanced. Our results highlight the difference in sensitivity of bacterial and fungal communities to PAHs, the later especially active while exposed to high concentrations of pollutant. This suggests that microbial communities inhabiting P. halepensis litters in Mediterranean coastal areas may resist to chronic pollution involving PAH