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

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

Effect of vitamin E (Tri E®) on antioxidant enzymes and DNA damage in rats following eight weeks exercise

<p>Abstract</p> <p>Background</p> <p>Exercise is beneficial to health, but during exercise the body generates reactive oxygen species (ROS) which are known to result in oxidative stress. The present study analysed the effects of vitamin E (Tri E^®) on antioxidant enzymes; superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (Cat) activity and DNA damage in rats undergoing eight weeks exercise.</p> <p>Methods</p> <p>Twenty four <it>Sprague-Dawley </it>rats (weighing 320-370 gm) were divided into four groups; a control group of sedentary rats which were given a normal diet, second group of sedentary rats with oral supplementation of 30 mg/kg/d of Tri E^®, third group comprised of exercised rats on a normal diet, and the fourth group of exercised rats with oral supplementation of 30 mg/kg/d of Tri E^®. The exercising rats were trained on a treadmill for 30 minutes per day for 8 weeks. Blood samples were taken before and after 8 weeks of the study to determine SOD, GPx, Cat activities and DNA damage.</p> <p>Results</p> <p>SOD activity decreased significantly in all the groups compared to baseline, however both exercised groups showed significant reduction in SOD activity as compared to the sedentary groups. Sedentary control groups showed significantly higher GPx and Cat activity compared to baseline and exercised groups. The supplemented groups, both exercised and non exercised groups, showed significant decrease in Cat activity as compared to their control groups with normal diet. DNA damage was significantly higher in exercising rats as compared to sedentary control. However in exercising groups, the DNA damage in supplemented group is significantly lower as compared to the non-supplemented group.</p> <p>Conclusions</p> <p>In conclusion, antioxidant enzymes activity were generally reduced in rats supplemented with Tri E^®probably due to its synergistic anti-oxidative defence, as evidenced by the decrease in DNA damage in Tri E^®supplemented exercise group.</p

Highly-resolved large eddy simulation of the nonreacting flow in an asymmetric vortex combustor

In this paper, we present a computational investigation of the nonreacting flow structure inside a novel asymmetric vortex combustor that was recently proposed by the authors. Large Eddy Simulation using the Smagorinsky-Lilly subgrid turbulence closure has been used to study such flow. A computational grid of 2.22×106 cells was used to ensure that the resolved turbulence kinetic energy is fairly more than 80% of the total turbulence kinetic energy budget. The flow was found to exhibit a central recirculation zone, and two secondary recirculation zones in the asymmetry regions. The vortex structure was found to be a completely forced vortex field. The effect of turbulence on the size and structure of the statistically averaged mean flow phenomena has been analyzed as discussed

Implementation of the eddy dissipation model of turbulent non-premixed combustion in OpenFOAM

This work discusses the implementation of eddy dissipation model in OpenFOAM CFD toolbox. The code was validated in modeling of confined non-premixed Methane jet flame. The model predictions were extensively compared against published experimental results as well as ANSYS Fluent® predictions. The differences between the implemented model in OpenFOAM and Fluent were demonstrated

Integrating a simplified P-N radiation model with edmfoam1.5: model assessment and validation

This work compliments our recently published work of implementing the eddy dissipation turbulent combustion model in OpenFOAM [1]. The major update proposed herein is linking the EdmFoam1.5 solver with radiation modeling libraries in OpenFOAM. The new solver was validated against experimental data for jet and swirling Sydney flame (SM1). Each case was modeled with/without radiation modeling. The results have a fair agreement in general. In jet flame cases, the radiation modeling has a good impact on refining the predicted results. However it has not the same great effect on the swirling flame case. A review of the EDM applications in different reacting flow problems is also presented and discussed

A flame structure approach for controlling carbon nanotube growth in flame synthesis

Flame synthesis of carbon nanotube (CNT) is still not commercialized due to the difficult control over CNT growth region in heterogeneous flame environment. In the present study, a model for flame synthesis of CNT that is capable of predicting CNT growth region is developed using a coupled computation of a computational fluid dynamics (CFD) flame model and a CNT growth rate model. The CFD results serve as input for the growth rate model to calculate CNT length and to generate flame structures that feature high CNT growth regions. Validation of the flame model, CNT growth model, and multi-scale model of flame synthesis is done with good accuracy. In the baseline case, the mixture fraction-based flame structures at various flame heights interestingly suggest a fixed range of mixture fraction of 0.46 to 0.85 within the growth region. The said finding indicates that mixture fraction governs the growth region in a diffusion flame. Almost twofold increase in the size of CNT growth region in physical space is observed when the inlet oxygen composition is increased from 25 to 35%. The increase in heat release of the rich flame at high oxygen concentration provides a wider region of high temperature for growth compared to that at low oxygen concentration

Comparison of eddy dissipation model and presumed probability density function model for temperature prediction in a non-premixed turbulent methane flame

Temperature distribution is predicted through numerical simulation of a turbulent non-premixed methane flame using the standard Eddy Dissipation Model (EDM) and a model based a presumed shape of probability density function (PDF) along with an equilibrium chemistry model. Results are validated against existing experimental data. Two models are compared to each other in terms of accuracy and their advantages and disadvantages are discussed

An investigational research of spray pattern for deflector flat spray nozzle using horizontal patternator

Valuation of the spray patterns and spray angle is necessary for producing nozzle applications such as in combustion process, agriculture, which is the experiment result in less liquid usage, and increased spray distribution accuracy. Therefore, this study investigate to analyze the spray distribution nozzle and consider the water consumption and spray angle using several type of deflector flat spray. First, the result should assist with spray patternator construction to determine water consumption. Then, measure of spray angle using Digital Single Lens Reflex Camera (DSLR) and image J software. The results provided support two fluid flow in the nozzle with increase of air pressure can reduce water consumption compared with single fluid flow. Effect of relationship between air pressures with water pressure in the nozzle producing the large spray angle compared water pressure only in the nozzle. Thus, fluid pressure in the nozzle is main parameter in developing on spray distribution. Spray pattern and spray angle are also an important consideration in nozzle selection and application

Simulation of corrected mass flow and non-adiabatic efficiency on a turbocharger

The aim of this project is to evaluate turbine's performance based on its actual condition. Holset H3B nozzles turbine geometry was used as the simulation model. Turbine's actual working condition was simulated using finite volume method (FVM). Three-dimensional Navier-Stoke equations with heat convection loss via turbine volute are solved. The parameters studied are corrected mass flow and turbine's efficiency at different heat transfer coefficients. Temperature difference within turbine's volute is the major factor that deteriorates turbine's efficiency. It is found that the higher the heat transfer coefficient, the lower turbine's efficiency will be