Numerical modelling and analysis of combustion in DI and PFI CNG engines - A study under different EGR dilution and Hydrogen doping conditions.

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CFD modelling of natural gas combustion in IC engines under different EGR dilution and H2-doping conditions

The present paper provides a contribution to the CFD modelling of reacting flows in IC engines fueled with natural gas. Despite the fact that natural gas has been widely investigated into in the last decades, the literature still lacks reliable models and correlations to be exploited so as to efficiently support the design of internal combustion engines. The paper deals with the development of an accurate CFD model, capable of capturing the effects of the engine working conditions and mixture compositions on the combustion process. The CFD model is based on the Extended Coherent Flame Model combustion model coupled to a laminar flame speed one through a user subroutine, which replaces the commonly adopted empirical correlations. The flame speed values have been derived from the application of a reaction mechanism for natural gas-air-residual gases mixtures. In the second part of the paper, the model is validated and applied to the investigation of the dependence of the combustion quality on the fuel doping with hydrogen as well as on the mixture dilution with EGR. As a matter of fact, the attractiveness of the mixture dilution with EGR relies on the potential in containing engine-out NOx emissions as well as in reducing the pumping losses, thus further abating fuel consumption at part loads. Finally, the effects of fuel blending with H2 on the EGR tolerance is discussed in the paper

A comparative study for antinociceptive potential of vitamin D3 with diclofenac in animal models

Background: Calcitriol is one of the active forms of vitamin D. It not only acts on calcium metabolism but might have a role in treating various disorders also through vitamin D receptors that are present in many tissues besides intestine and bone. This study was conducted to compare antinociceptive activity of Calcitriol with Diclofenac and Morphine in animal models.Methods: In this study, healthy Swiss albino mice were taken after permission from IAEC. Mice were divided into six groups as one control- treated with normal saline, two standards - treated with diclofenac and treated with morphine while three tests - treated with Calcitriol in dose of 15µg /kg/mice, 30µg/kg/mice and 60µg/kg/mice respectively. Comparison of antinociception was done using Tail pinch and writhing method.Results: Tail pinch and Writhing methods were used for comparison of antinociceptive activity. In tail pinch model, Calcitriol showed some analgesia at 30 and 60μg/Kg doses, which was more than control but not comparable with the standard Morphine. In writhing method, test doses of Calcitriol (15 and 30μg/Kg) failed to show analgesic efficacy in inflammatory pain but test dose of 60μg/Kg showed some analgesic activity which was not comparable with standard Diclofenac.Conclusions: Antinociception was exhibited at higher doses of Calcitriol by tail pinch method while in writhing method analgesic activity was shown with only 60 μg/Kg dose of Calcitriol. The results obtained from this study needs to be further evaluated by planning extensive animal experimentation

An experimental study to evaluate and compare the analgesic activity of calcitriol with morphine in albino mice at a tertiary care teaching hospital in Maharashtra, India

Background: Vitamin D plays vital role in physiological functions in humans through its active form Calcitriol (Vitamin D3). Vitamin D receptors are found in most tissues, attributing to its classic and non-classic actions. Calcitriol exerts important regulatory effects on the molecular pathways involved in inflammation and pain. The present study is done for experimental evaluation of analgesic action of Calcitriol using pain models in albino mice.Methods: In this prospective, experimental study, healthy Swiss albino mice were taken after permission from IAEC. Mice were divided into five groups as Control- treated with normal saline, Standard- treated with morphine and Test groups- treated with Calcitriol in dose of 15 µg /kg/mice, 30 µg /kg/mice and 60 µg/kg/mice respectively. Evaluation of analgesic activity was done using Hot plate and Tail flick analgesiometer.Results: All the 3 test doses of Calcitriol although showed prolongation of reaction time in Hot plate method up to 60 mins but the analgesic activity was not significant in comparison with the standard Morphine. With Tail flick method Calcitriol failed to show any analgesic efficacy at 15-30 μg/Kg but showed some analgesia at 60 μg/Kg which was more than control but not at all comparable with the standard Morphine for thermal pain.Conclusions: The analgesic activity of Calcitriol was exhibited at higher doses. This property needs to be further evaluated by planning extensive animal experimentation using different animal models

Experimental and Numerical Analysis of Diluted Combustion in a Direct Injection CNG Engine Featuring Post- Euro-VI Fuel Consumption Targets

The present paper is concerned with part of the work performed by Renault, IFPEN and Politecnico di Torino within a research project founded by the European Commission. The project has been focused on the development of a dedicated CNG engine featuring a 25% decrease in fuel consumption with respect to an equivalent Diesel engine with the same performance targets. To that end, different technologies were implemented and optimized in the engine, namely, direct injection, variable valve timing, LP EGR with advanced turbocharging, and diluted combustion. With specific reference to diluted combustion, it is rather well established for gasoline engines whereas it still poses several critical issues for CNG ones, mainly due to the lower exhaust temperatures. Moreover, dilution is accompanied by a decrease in the laminar burning speed of the unburned mixture and this generally leads to a detriment in combustion efficiency and stability. The optimization of in-cylinder turbulence plays a fundamental role in compensating this trend. The present paper is specifically focused on the characterization of the diluted combustion in the direct injection engine. The results of an experimental activity have been presented, aimed at characterizing the in-cylinder combustion process and the exhaust temperatures at 2000 rpm and variable load, both without dilution and with 20% of external EGR. At the same time, a 3-D numerical model for the in-cylinder turbulence and combustion simulation has been developed in Converge. The model embeds a user-specified laminar-flame speed submodel, which was derived from a 1-D combustion simulation model with detailed chemistry. The model has been calibrated against experimental data and then used to characterize the heat release dependence on the dilution. The experimental activity has evidenced the potential of EGR to increase the engine efficiency, by allowing to increase the boost level at full load and by reducing pumping losses at partial load. As far as the maximum allowed EGR rate is concerned, the CFD activity showed that the limit can be detected on the basis of a threshold value of the MFB0-50 interval. At 2000 rpm and medium load the maximum EGR rate ranged around 35% and showed an increasing trend versus load. It also demonstrated a decreasing trend against the engine speed

Combustion Characterization in a Diffusive Gas Turbine Burner for Hydrogen-Compliant Applications

The target of net-zero emissions set by the 2015 Paris Agreement has strongly commissioned the energy production sector to promote decarbonization, renewable sources exploitation, and systems efficiency. In this framework, the utilization of hydrogen as a long-term energy carrier has great potential. This paper is concerned with the combustion characterization in a non-premixed gas turbine burner, originally designed for natural gas, when it is fed with NG-H2 blends featuring hydrogen content from 0 to 50% in volume. The final aim is to retrofit a 40 MW gas turbine. Starting from the operational data of the engine, a CFD model of the steady-state combustion process has been developed, with reference to the base load NG conditions, by reducing the fuel mass-flow rate by up to 17% to target the baseline turbine inlet temperature. When the fuel is blended with hydrogen, for a given temperature at turbine inlet, an increase in the peak temperature up to 800 K is obtained, if no countermeasures are taken. Furthermore, the flame results are more intense and closer to the injector in the case of hydrogen blending. The results of this work hint at the necessity of carefully analyzing the possible NOx compensation strategies, as well as the increased thermal stresses on the injector

Zone of influence for particle number concentrations at signalised traffic intersections

Abstract Estimation of zone of influences (ZoI) at signalised traffic intersections (TI) is important to accurately model particle number concentrations (PNCs) and their exposure to public at emission hotspot locations. However, estimates of ZoI for PNCs at different types of TIs are barely known. We carried out mobile measurements inside the car cabin with windows fully open for size–resolved PNCs in the 5–560 nm range on a 6 km long busy round route that had 10 TIs. These included four–way TIs without built–up area (TI4w-nb), four–way TIs with built–up area (TI4w-wb), three–way TIs without built–up area (TI3w-nb) and three–way TIs with built–up area (TI3w-wb). Mobile measurements were made with a fast response differential mobility spectrometer (DMS50). Driving speed and position of the car were recorded every second using a global positioning system (GPS). Positive matrix factorisation (PMF) modelling was applied on the data to quantify the contribution of PNCs released during deceleration, creep–idling, acceleration and cruising to total PNCs at the TIs. The objectives were to address the following questions: (i) how does ZoI vary at different types of TIs in stop– and go–driving conditions?, (ii) what is the effect of different driving conditions on ZoI of a TI?, (iii) how realistically can the PNC profiles be generalised within a ZoI of a TI?, and (iv) what is the share of emissions during different driving conditions towards the total PNCs at a TI? Average length of ZoI in longitudinal direction and along the road was found to be the highest (148 m; 89 to −59 m from the centre of a TI) at a TI3w-wb, followed by TI4w-nb (129 m; 79 to −42 m), TI3w-nb (86 m; 71 to −15 m) and TI4w-wb (79 m; 46 to −33 m) in stop– and go–driving conditions. During multiple stopping driving conditions when a vehicle stops at a TI more than once in a signal cycle due to oversaturation of vehicles, average length of ZoI increased by 55, 22 and 21% at TI4w-nb, TI3w-nb and TI3w-wb, respectively, compared with stop– and go–driving conditions. Within average length of ZoI in stop– and go– driving conditions, PNCs followed a three degree polynomial form at all TIs. Dimensional analysis suggested that coefficients of polynomial equations at both four–way and three–way TIs were mainly influenced by delay time, wind speed and particle number flux. The PMF analysis suggested that deceleration contributed the most to total PNCs at all TIs, except TI4w-wb. Findings of this study are a step forward to understand the contribution of different driving conditions towards the total PNCs and their exposure at the TIs

GLI1 regulates a novel neuropilin-2/alpha6beta1 integrin based autocrine pathway that contributes to breast cancer initiation

The characterization of cells with tumour initiating potential is significant for advancing our understanding of cancer and improving therapy. Aggressive, triple-negative breast cancers (TNBCs) are enriched for tumour-initiating cells (TICs). We investigated that hypothesis that VEGF receptors expressed on TNBC cells mediate autocrine signalling that contributes to tumour initiation. We discovered the VEGF receptor neuropilin-2 (NRP2) is expressed preferentially on TICs, involved in the genesis of TNBCs and necessary for tumour initiation. The mechanism by which NRP2 signalling promotes tumour initiation involves stimulation of the alpha6beta1 integrin, focal adhesion kinase-mediated activation of Ras/MEK signalling and consequent expression of the Hedgehog effector GLI1. GLI1 also induces BMI-1, a key stem cell factor, and it enhances NRP2 expression and the function of alpha6beta1, establishing an autocrine loop. NRP2 can be targeted in vivo to retard tumour initiation. These findings reveal a novel autocrine pathway involving VEGF/NRP2, alpha6beta1 and GLI1 that contributes to the initiation of TNBC. They also support the feasibility of NRP2-based therapy for the treatment of TNBC that targets and impedes the function of TICs. of EMBO

Vertical and horizontal variability in airborne nanoparticles and their exposure around signalised traffic intersections

We measured size–resolved PNCs in the 5–560 nm range at two different types (4– and 3–way) of TIs in Guildford (Surrey, UK) at fixed sites (~1.5 m above the road level), sequentially at 4 different heights (1, 1.5, 2.5 and 4.7 m), and along the road at five different distances (10, 20, 30, 45 and 60 m). The aims were to: (i) assess the differences in PNCs measured at studied TIs, (ii) identify the best fit probability distribution curves for the PNCs, (iii) determine vertical and horizontal decay profiles of PNCs, (iv) estimate particle number emission factors (PNEFs) under congested and free–flow traffic conditions, and (v) quantify the pedestrian exposure in terms of respiratory deposition dose (RDD) rates at the TIs. Daily averaged particle number distributions at TIs reflected the effect of fresh emissions with peaks at 5.6, 10 and 56nm. Despite the relatively high traffic volume at 3–way TI, average PNCs at 4–way TI were about twice as high as at 3–way TI, indicating less favourable dispersion conditions. Generalised extreme value distribution fitted well to PNC data at both TIs. Vertical PNC profiles followed an exponential decay, which was much sharper at 4–way TI than at 3–way TI, suggesting ~60% less exposure for people at first floor (4.7 m) to those at ground floor around 4-way TI. Vertical profiles indicated much sharper (~132–times larger) decay than in horizontal direction, due to close vicinity of road vehicles during the along-road measurements. Over an order of magnitude higher PNEFs were found during congested, compared with free–flow, conditions due to frequent changes in traffic speed. Average RDD rate at 4–way TI during congested conditions were up to 14–times higher than those at 3–way TI (1.20×1011 h˗1). Findings of this study are a step forward to understand exposure at and around the TIs