Effect of CO2/N2 Dilution on Premixed Methane–Air Flame Stability Under Strained Conditions

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Joseph S. Feser ◽  
Ashwani K. Gupta
Keyword(s):  
Thermal Stresses ◽  
Strain Rates ◽  
Low Oxygen ◽  
Temperature Dependent ◽  
Lower Strain ◽  
Pollutants Emission ◽  
Stable Flame ◽  
Thermal Intensity ◽  
Flame Behavior ◽  
Low Oxygen Concentration

The effects of adding N2 or CO2 as diluents to a premixed methane–air flames under strain conditions (associated with a stagnation plate) were examined for flame stand-off distance, stability, intensity, and global flame behavior at various equivalence ratios. A stagnation plate was used to simulate the flame behavior near a combustor wall that can help provide some insights into reducing thermal stresses and enhance combustor lifetime. Decrease in equivalence ratio at the same thermal intensity provided larger strain rates while maintaining a stable flame. At stoichiometric condition, a balance was provided between high strain rates and low oxygen concentration flames to mitigate the peak (maximum) flame temperatures, and the associated temperature-dependent pollutants emission, such as NOx, CO, and unburnt hydrocarbons. Higher thermal intensities provided higher strain rates; however, the addition of diluents impacted in destabilization of flame. The flame stand-off behavior occurred at lower strain rates, low thermal intensity, and increased equivalence ratios. CO2 dilution reduced flame intensity, increased flame stand-off distance and overall flame destabilization than that with N2 dilution.

Effect of low oxygen concentration on activation of inflammation by Helicobacter pylori

2021 ◽  
Vol 560 ◽  
pp. 179-185
Author(s):  
Adiza Abass ◽  
Tokuju Okano ◽  
Kotchakorn Boonyaleka ◽  
Ryo Kinoshita-Daitoku ◽  
Shoji Yamaoka ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Oxygen Concentration ◽  
Low Oxygen ◽  
Low Oxygen Concentration

scholarly journals A new boundary element algorithm for modeling and simulation of nonlinear thermal stresses in micropolar FGA composites with temperature-dependent properties

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Mohamed Abdelsabour Fahmy
Keyword(s):  
Modeling And Simulation ◽  
Boundary Element ◽  
Thermal Stresses ◽  
Computation Time ◽  
Functionally Graded ◽  
Temperature Dependent ◽  
Time Step ◽  
Kirchhoff Transformation ◽  
Nonlinear Temperature ◽  
Temperature Dependent Properties

AbstractThe main aim of this article is to develop a new boundary element method (BEM) algorithm to model and simulate the nonlinear thermal stresses problems in micropolar functionally graded anisotropic (FGA) composites with temperature-dependent properties. Some inside points are chosen to treat the nonlinear terms and domain integrals. An integral formulation which is based on the use of Kirchhoff transformation is firstly used to simplify the transient heat conduction governing equation. Then, the residual nonlinear terms are carried out within the current formulation. The domain integrals can be effectively treated by applying the Cartesian transformation method (CTM). In the proposed BEM technique, the nonlinear temperature is computed on the boundary and some inside domain integral. Then, nonlinear displacement can be calculated at each time step. With the calculated temperature and displacement distributions, we can obtain the values of nonlinear thermal stresses. The efficiency of our proposed methodology has been improved by using the communication-avoiding versions of the Arnoldi (CA-Arnoldi) preconditioner for solving the resulting linear systems arising from the BEM to reduce the iterations number and computation time. The numerical outcomes establish the influence of temperature-dependent properties on the nonlinear temperature distribution, and investigate the effect of the functionally graded parameter on the nonlinear displacements and thermal stresses, through the micropolar FGA composites with temperature-dependent properties. These numerical outcomes also confirm the validity, precision and effectiveness of the proposed modeling and simulation methodology.

scholarly journals Strain-Rate and Grain‒Size Effects in Ice

1987 ◽  
Vol 33 (115) ◽  
pp. 274-280 ◽  
Author(s):  
David M. Cole
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Transition Point ◽  
Boundary Migration ◽  
Peak Stress ◽  
Strain Rates ◽  
Thin Sections ◽  
Fine Grained ◽  
Lower Strain ◽  
Polycrystalline Ice

AbstractThis paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10−7to 10−1s−1, grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C.At strain-rates between 10−7and 10−3s−1, the stress-strain-rate relationship followed a power law with an exponent ofn= 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10−6s−1the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10−3s−1the peak stress became independent of strain-rate.The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.

The Constant Low Oxygen Concentration in All the Target Cells for Mouse Tail Radionecrosis

1982 ◽  
Vol 92 (1) ◽  
pp. 172 ◽  
Author(s):  
J. H. Hendry ◽  
J. V. Moore ◽  
B. W. Hodgson ◽  
J. P. Keene
Keyword(s):  
Oxygen Concentration ◽  
Target Cells ◽  
Low Oxygen ◽  
Low Oxygen Concentration

scholarly journals Simultaneous Nitrification and Denitrification in an SBR with a Modified Cycle During Reject Water Treatment

2013 ◽  
Vol 39 (1) ◽  
pp. 83-91 ◽  
Author(s):  
Katarzyna Bernat
Keyword(s):  
Batch Reactor ◽  
Anaerobic Sludge ◽  
Simultaneous Nitrification And Denitrification ◽  
Low Oxygen ◽  
Total Removal ◽  
Operational Conditions ◽  
Reject Water ◽  
Do Concentration ◽  
Nitrification And Denitrification ◽  
Low Oxygen Concentration

Abstract In this study, the dependence between volumetric exchange rate (n) in an SBR (Sequencing Batch Reactor) with a modified cycle and simultaneous nitrification and denitrification (SND) efficiency during the treatment of anaerobic sludge digester supernatant was determined. In the SBR cycle alternating three aeration phases (with limited dissolved oxygen (DO) concentration up to 0.7 mg O2/L) and two mixing phases were applied. The lengths of each aeration and mixing phases were 4 and 5.5 h, respectively. Independently of n, a total removal of ammonium was achieved. However, at n = 0.1 d-1 and n = 0.3 d-1 nitrates were the main product of nitrification, while at n = 0.5 d-1, both nitrates and nitrites occurred in the effluent. Under these operational conditions, despite low COD/N (ca. 4) ratio in the influent, denitrification in activated sludge was observed. A higher denitrification efficiency at n = 0.5 d-1 (51.3%) than at n = 0.1 d-1 (7.8%) indicated that n was a crucial factor influencing SND via nitrite and nitrate in the SBR with a low oxygen concentration in aeration phases.

Elasto-Plastic Analysis of Thermal Stress Development During VAR of Ingots

1999 ◽  
Author(s):  
M. K. Alam ◽  
K. K. Wong ◽  
S. L. Semiatin
Keyword(s):  
Thermal Stresses ◽  
Plastic Material ◽  
Material Model ◽  
Thermomechanical Properties ◽  
Vacuum Arc ◽  
Aerospace Materials ◽  
Temperature Dependent ◽  
Vacuum Arc Remelting ◽  
High Cooling Rates ◽  
Dc Arc

Abstract The vacuum arc remelting (VAR) process has been developed to melt and cast high quality aerospace materials such as titanium alloys. VAR comprises the continuous remelting of a consumable electrode by means of a dc arc under vacuum or a low partial pressure of argon. The molten metal solidifies in a water-cooled copper crucible leading to high cooling rates that often results in large thermal stresses. The development of temperature gradients and the resulting thermal stresses during the VAR processes was investigated using an elasto-plastic material model with temperature dependent thermomechanical properties. Detailed solutions were obtained by using the commercial finite element code ABAQUS.

scholarly journals Zooplankton fluctuations in Jurumirim Reservoir (São Paulo, Brazil): a three-year study

2009 ◽  
Vol 69 (1) ◽  
pp. 1-18 ◽  
Author(s):  
LP. Sartori ◽  
MG. Nogueira ◽  
R. Henry ◽  
EM. Moretto
Keyword(s):  
Water Column ◽  
Oxygen Concentration ◽  
Retention Time ◽  
Sao Paulo ◽  
Seasonal Effect ◽  
São Paulo ◽  
Low Oxygen ◽  
High Concentration ◽  
Heterogeneous Distribution ◽  
Low Oxygen Concentration

During three consecutive years, monthly samples of zooplankton were taken in the lacustrine (dam) zone of Jurumirim (São Paulo, Brazil). The seasonal effect on basic limnological features (thermal regime, oxygen distribution, phytoplankton biomass, etc.) was also examined. The influence of the seasonality on the fluctuation of the zooplankton composition and abundance was not clearly detected (low degree of recurrent patterns). Rotifers (32 taxa) were the most abundant organisms during almost the entire study period with some seasonal alternations in the maximum abundance peaks of the main taxa (Conochilus unicornis, Keratella americana, K. cochlearis and Hexarthra spp.), except for Polyarthra (mainly P. vulgaris). Only occasionally copepods were numerically dominant. Higher copepod abundance was positively associated to periods of increase in the water retention time. Among the Copepoda (10 taxa) the calanoids (mainly Notodiaptomus iheringi) were more abundant, especially in warmer periods. Conversely, cyclopoids had higher abundance in autumn and winter. The species Thermocyclops minutus and T. decipiens co-occurred, but the first attained higher abundance. Some evidence of co-existence strategies between both species are considered. Cladocera (17 taxa) was never numerically dominant and the main taxa (Bosmina spp., Ceriodaphnia spp. and Diaphanosoma spp.) occurred almost the whole study period and did not present a seasonal pattern of fluctuation. Diaphanosoma (mainly D. birgei) attained the highest abundance among cladocerans. Most organisms were always found at the surface, but they also occupy the whole water column, even in periods of stratified conditions and low oxygen concentration in the bottom layers. Among the main zooplanktonic taxa, only Hexarthra avoids deep layers. An exceptionally high concentration of Copepoda nauplii on the surface was influenced by low transparency, high concentration of phytoplankton at this layer and low oxygen concentration at the bottom. In periods of higher retention timevariability there was a more heterogeneous distribution of the zooplankton in the water column. The increase in the retention time seems also to favor the copepod development. Finally, some inter-decade changes are considered on the basis of zooplankton assemblage structure observations.

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