Flame propagation and burning rates of methane-air mixtures using schlieren photography

Different methodology have been shown to produce different results for Markstein length and laminar burning velocity of methane-air mixture. This study attempts to determine the aforesaid parameters using the newly developed closed vessel combustion chamber with Schlieren photography. Markstein length and burning rate of methane-air mixture was determined under the initial pressure of 1 atm, temperature range of 298-302K and equivalence ratio range of 0.7-1.3. Experiments were performed in a centrally ignited 29.16L cylindrical constant volume combustion chamber. Ignition energy was set at 25mJ for each experiment. The images of spherically expanding flame were recorded using Schlieren photography technique at a speed of 2000 frame per second. Analysis of the flame area yield flame radii from which the flame speed and stretch rate could be obtained. These parameters would allow the determination of Markstein length and burning rate of the flame. Results show that Markstein length magnitude increases proportionally with equivalence ratio with a magnitude ranging from 0.125cm to 0.245cm. Maximum burning rate occurs at equivalence ratio of 1.1 with a magnitude of 0.366 m/s. Flame of each equivalence ratio also exhibits fluctuation arising from acoustic disturbance. This disturbance becomes more apparent at higher equivalence ratio

Flameless combustion of propane-air mixture in a laboratory scale burner

In this work, the operational and emission of the laboratory scale burner under the flameless combustion regime using propane is examined. The combustor is equipped with parallel jet burner systems with controlled gas fuel and oxidizer. The combustor consists of several ports that are used to measure temperature variation and analyze gas emission. The atmospheric air was heated by flowing it inside the chamber until the air temperature increased to approximately the auto ignition temperature of the fuel. The furnace under investigation has successfully produced temperature uniformity ratios that are one order of magnitude less than such of the visible flame mode. It is observed that, flameless combustion can be achieved by using propane as a fuel. The value of NOX emission during flameless combustion was reduced of about 70% in average compared to the conventional flame at certain range of equivalence ratio

Numerical evaluation of thermo-hydraulic performance in fin-and-tube compact heat exchangers with different tube cross-sections

This study examined numericallythe Thermal-hydrodynamic properties of airflow in the fin-and-tube compact heat exchangers (FTCHEs) with considering different shapes of tubes in lowReynoldsnumbers. The influence of applying flat, oval and circular tube adjustments on the thermal and hydraulic characteristics of air flow were analyzed on the in-line tube arrangements. Establishing standard conditions, the study compared different geometries based on circular tubes of 10.459 mm diameter tubes with 25.4 mm longitudinal pitches and 25.4 mm transverse pitches. The other geometries of tubes were assumed in a stable and constant state preparing the same heat transfer surface area per unit volume as that of the nominal case. The results showed that the FTCHE with flat tubes gives the best area goodness factor (j/f) with in a certainrange of Reynoldsnumbers. In addition, FTCHE with flat tubes shown the best thermo-hydraulic performance and a significant augmentation of up to 10.83% and 35.63% in the average area goodness factor achieved accompanied by a decrease in the average friction factor of 17.02% and 43.41% in the flat tube case compared to the oval and circle tube shapes, respectively. It is concluded that the average area goodness factorfor the oval tube is about 25.04% higher than that of the circular tube, while the average friction factor for the oval tube is about 26.9% lower than that of the circular tube. This means that the flat tube has a better-combined thermal-hydraulic performance than the oval and circle tube

Influence of modified air on combustion characteristics in meso-scale vortex combustor

The need to supply power for miniaturized mechanical devices opens exciting new opportunities for combustion, especially in the field of micro-power generation. Because of the need for power supply devices with high-specific energy (small-size, low weight, long duration) and power. Meso/micro scale combustion has been considered as a potential solution for many small-volumes and energy demanding systems, such as power supplies for portable device. In this study the structure of turbulent diffusion flames in a meso scale combustor with different oxygen concentration has been investigated using a new design of vortex combustor. Methane gas was used as a fuel. Numerical investigations have been performed on the temperature distribution, swirl number, heat loss, and emitter efficiency in vortex combustion. The results have been obtained for various O2 concentrations in the air as oxidizer. The results shows that thermal flame behaves depend strongly on the oxygen content in the oxidizer. When the oxygen concentration increases from 15% to 30%, the flame temperature of the meso-combustion rises in all cases. Emitter efficiency is very high in the meso-combustor with high O2 concentration in oxidizer

Sublingual sufentanil for postoperative pain relief: First clinical experiences

Background: The sublingual sufentanil tablet system (SSTS) is a novel hand-held patientcontrolled analgesia device developed for treatment of moderate-to-severe postoperative pain. Here we present the first results of its clinical use. Methods: Adult patients undergoing major surgery in five hospitals in the Netherlands received the SSTS for postoperative pain relief as part of multimodal pain management that further included paracetamol and a nonsteroidal anti-inflammatory drug (NSAID). The following variables were collected: postoperative pain scores using the 11-point numerical rating score (NRS) at rest, number of tablets used, occurrence of nausea, and patient satisfaction scores. Results: We included 280 patients in the study; the majority underwent laparoscopic abdominal (49%) or orthopedic (knee replacement) surgery (34%). The median NRS was 3.5 (interquartile range 2.3–4.0) on the day of surgery, 3.3 (2.3–4.0) on the first postoperative day, and 2.8 (2.0–4.0) on the second postoperative day; pain scores did not differ between surgery types. Mean number of tablets used was 19 (range 0–86). Nausea occurred in 34% of patients, more often in women (45% vs 19%). Overall satisfaction was high in 73% of patients. Satisfaction was correlated with pain relief (p < 0.001) and inversely correlated with occurrence of nausea (p=0.01). Discussion: In this data set obtained under real-life conditions we show that the SSTS effectively managed postoperative pain in abdominal and orthopedic surgeries. Future studies should determine patient populations that benefit most from the SSTS, assess the added values versus intravenous patient-controlled analgesia, and determine the pharmacoeconomics of the system

Functional and Biogenetical Heterogeneity of the Inner Membrane of Rat-Liver Mitochondria

Rat liver mitochondria were fragmented by a combined technique of swelling, shrinking, and sonication. Fragments of inner membrane were separated by density gradient centrifugation. They differed in several respects: electronmicroscopic appearance, phospholipid and cytochrome contents, electrophoretic behaviour of proteins and enzymatic activities. Three types of inner membrane fractions were isolated. The first type is characterized by a high activity of metal chelatase, low activities of succinate-cytochrome c reductase and of glycerolphosphate dehydrogenase, as well as by a high phospholipid content and low contents of cytochromes aa3 and b. The second type displays maximal activities of glycerolphosphate dehydrogenase and metal chelatase, but contains relatively little cytochromes and has low succinate-cytochrome c reductase activity. The third type exhibits highest succinate-cytochrome c reductase activity, a high metal chelatase activity and highest cytochrome contents. However, this fraction was low in both glycerolphosphate dehydrogenase activity and phospholipid content. This fraction was also richest in the following enzyme activities: cytochrome oxidase, oligomycin-sensitive ATPase, proline oxidase, 3-hydroxybutyrate dehydrogenase and rotenone-sensitive NADH-cytochrome c reductase. Amino acid incorporation in vitro and in vivo in the presence of cycloheximide occurs predominantly into inner membrane fractions from the second type. These data suggest that the inner membrane is composed of differently organized parts, and that polypeptides synthesized by mitochondrial ribosomes are integrated into specific parts of the inner membrane

Extracts of Feijoa Inhibit Toll-Like Receptor 2 Signaling and Activate Autophagy Implicating a Role in Dietary Control of IBD

Inflammatory bowel disease (IBD) is a heterogeneous chronic inflammatory disease affecting the gut with limited treatment success for its sufferers. This suggests the need for better understanding of the different subtypes of the disease as well as nutritional interventions to compliment current treatments. In this study we assess the ability of a hydrophilic feijoa fraction (F3) to modulate autophagy a process known to regulate inflammation, via TLR2 using IBD cell lines

Hopping in hypogravity-A rationale for a plyometric exercise countermeasure in planetary exploration missions

© 2019 Weber et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Moon and Mars are considered to be future targets for human space explorations. The gravity level on the Moon and Mars amount to 16% and 38%, respectively, of Earth's gravity. Mechanical loading during the anticipated habitual activities in these hypogravity environments will most likely not be sufficient to maintain physiological integrity of astronauts unless additional exercise countermeasures are performed. Current microgravity exercise countermeasures appear to attenuate but not prevent 'space deconditioning'. However, plyometric exercises (hopping and whole body vibration) have shown promise in recent analogue bed rest studies and may be options for space exploration missions where resources will be limited compared to the ISS. This paper therefore tests the hypothesis that plyometric hop exercise in hypogravity can generate sufficient mechanical stimuli to prevent musculoskeletal deconditioning. It has been suggested that hypogravity-induced reductions in peak ground reaction force (peak vertical GRF) can be offset by increases in hopping height. Therefore, this study investigated the effects of simulated hypogravity (0.16G, 0.27G, 0.38G, and 0.7G) upon sub-maximal plyometric hopping on the Verticalised Treadmill Facility, simulating different hypogravity levels. Results show that peak vertical GRF are negatively related to simulated gravity level, but positively to hopping height. Contact times decreased with increasing gravity level but were not influenced through hopping height. In contrast, flight time increased with decreasing gravity levels and increasing hopping height (P < 0.001). The present data suggest that the anticipated hypogravity-related reductions of musculoskeletal forces during normal walking can be compensated by performing hops and therefore support the idea of plyometric hopping as a robust and resourceful exercise countermeasure in hypogravity. As maximal hop height was constrained on the VTF further research is needed to determine whether similar relationships are evident during maximal hops and other forms of jumping

Is telomere length socially patterned? Evidence from the West of Scotland Twenty-07 study

Lower socioeconomic status (SES) is strongly associated with an increased risk of morbidity and premature mortality, but it is not known if the same is true for telomere length, a marker often used to assess biological ageing. The West of Scotland Twenty-07 Study was used to investigate this and consists of three cohorts aged approximately 35 (N = 775), 55 (N = 866) and 75 years (N = 544) at the time of telomere length measurement. Four sets of measurements of SES were investigated: those collected contemporaneously with telomere length assessment, educational markers, SES in childhood and SES over the preceding twenty years. We found mixed evidence for an association between SES and telomere length. In 35-year-olds, many of the education and childhood SES measures were associated with telomere length, i.e. those in poorer circumstances had shorter telomeres, as was intergenerational social mobility, but not accumulated disadvantage. A crude estimate showed that, at the same chronological age, social renters, for example, were nine years (biologically) older than home owners. No consistent associations were apparent in those aged 55 or 75. There is evidence of an association between SES and telomere length, but only in younger adults and most strongly using education and childhood SES measures. These results may reflect that childhood is a sensitive period for telomere attrition. The cohort differences are possibly the result of survival bias suppressing the SES-telomere association; cohort effects with regard different experiences of SES; or telomere possibly being a less effective marker of biological ageing at older ages