Conditional moment closure modelling of soot formation in turbulent, non-premixed methane and propane flames

Presented are results obtained from the incorporation of a semi-empirical soot model into a first-order conditional moment closure (CMC) approach to modelling turbulent, non-premixed methane–air and propane–air flames. Soot formation is determined via the solution of two transport equations for soot mass fraction and particle number density, with acetylene and benzene employed as the incipient species responsible for soot nucleation, and the concentrations of these calculated using a detailed gas-phase kinetic scheme involving 70 species. The study focuses on the influence of differential diffusion of soot particles on soot volume fraction predictions. The results of calculations are compared with experimental data for atmospheric and 3 atm methane flames, and propane flames with air preheated to 323 K and 773 K. Overall, the study demonstrates that the model, when used in conjunction with a representation of differential diffusion effects, is capable of accurately predicting soot formation in the turbulent non-premixed flames considered

Analysis of Turbulence Models Performance for the Predictions of Flow Yield, Efficiency, and Pressure Drop of a Gas-solid Cyclone Separator

This paper presents the results obtained from the application of computational fluid dynamics (CFD) to modelling the flow field of a Lapple cyclone and to optimizing the cyclone based upon its geometrical parameters. A pre-processor software GAMBIT was employed to set up the configuration, discretisation, and boundary conditions of the cyclone. The characteristics of the cyclone being studied was 0.2 m in diameter, receiving a gas flow rate of 0.1 m3/s with a particle mass loading of 0.01 kg/m3. A commercial CFD code FLUENT 6.2.16 was employed to simulate the flow field and particle dynamics in the cyclone. The objective of this research was to investigate the performance of a number of turbulence models on the prediction of the flow field, collection efficiency and pressure drop in the Lapple cyclone. A number of five turbulence models under Reynolds Averaged Navier Stokes (RANS) category, including Spallart-Allmaras, standard k-ε model, RNG k-ε model, standard k-ω model, and Reynolds Stress Model (RSM) were examined in the simulation of the flow field and particle dynamics inside the cyclone. A validation of all calculation was performed by comparing the predicted results in terms of axial and tangential velocities, efficiency and pressure drop against experimental data of a Lapple cyclone taken from literature. The results of the investigation show that out of five turbulence models being tested, the RSM presented the best predicted results. The predictions of axial and tangential velocities as well as cyclone efficiency by this model are in excellent agreement with the experimental data. Although the pressure drop in the cyclone is under-predicted, the RSM predictions are far better than those of other model. Other turbulence models are over-predicted and under-predicted the axial and tangential velocity, respectively. With respect to efficiency and pressure drop of the cyclone, other models are capable of following the trend of the experimental data but they failed to agree with the experimental values. These results suggest that the RSM is the most suitable turbulence model to represent the flow field and particle dynamics inside a cyclone gas-solid separator

Efektivitas Perendaman Daging Sapi Dalam Ekstrak Pegagan (Centelia Asiatica L.)

Meat preservation generally carries put by refrigeration, heating and adding chemical preservation materials. Purpose of the· preservation is to keep meat quality, because meat is one of high nutrient food materials. The content of nutrient in meat is good media for the growth of bacteria, and then they can decrease meat quality. Hence; it needs some treatments, one of them is a natural preservation such as extract of Centella asiatica L. that content salt minerals and bacterial compound, and it can block and remove bacteria.The purpose of this research is to determine influence extract of Centella asiatica 1. with different concentrations to water content, pH, and total bacterial colony, and sensorial value (color, texture, and aroma) of beef. This research uses a Complete Random Design that consists of four treatments with three repeat. The treatments are adding extract of Centella asiatica L. for 0 ml, 10 ml, 20 ml, 30 m1. Submersion of beef within the extract of Centella asiatica L. takes about 30 minutes. Resulted variables data statically processed by using various analysis. If the differences happen among the treatments, then must be perform following test by using Duncan Multiple Range Test (DMRT). Theresult of this research show that the beef submersions with adding 30 ml of extract of Centella asiatica L. is most effective in decreasing water content of beef to 61.32%, pH to 5.17, total bacterial colony to 5:1 x 105 CFU / gram and color change to undesirable brownish red. But it\u27s not influential to texture and aroma. Beef have in a row pattern, approximately soft and nice look, fresh blood aroma

Analysis of Y Chromosome Microdeletion in Indonesian Males

The aim of this study is to find out Y chromosome microdeletion in Indonesian azoospermic men. This study used the PCR method with five STS to locate deletion on three different subregions (AZFa, AZFb, and AZFc) of azoospermic men and one STS to amplify SRY gen which act as an internal control. In this study we detected two of 35 (5,7%) azoospermic men had microdeletion Yq. One had microdeletion on subregion AZFa (sY84) and AZFb (RBMY1) and the other one on subregion AZFc (sY254 and sY255). Therefore microdeletion of the Y chromosome in Indonesian azoospermic men excist. Examination of microdeletion of Y chromosomes in azoospermic men is important if they are going to participate in the Intra Cytoplasmic Infection Program to avoid genetic disorders of their descendants

Response Surface Methodology Approach to the Optimization of Cyclone Separator Geometry for Maximum Collection Efficiency

A Response surface methodology coupled with a Box-Behnken design experiment has been utilized to optimize geometry parameters of a cyclone as a gas-solid separator in an effort to obtain a maximum particle collection efficiency. Independent variables being optimized include seven geometry parameters of inlet height (a/D), inlet width (b/D), vortex finder height (S/D), vortex finder diameter (De/D), total cyclone height (Ht/D), cylinder height (h/D), and cone tip diameter (Bc/D). A number of 62 treatments were performed following Box-Behnken experimental design of seven factors and three levels (-1, 0 and +1). The response variable, the cyclone collection efficiency, was calculated in accordance with the Muschelknautz model using a spreadsheet software. The relationship between the response variable and independent variables was mathematically expressed according to a quadratic polynomial equation calculated with the aid of Design Expert software.  The results of the research showed that among seven variables being investigated, there are only five cyclone geometry parameters which significantly affected the cyclone collection efficiency, including inlet height (a/D), inlet width (b/D), vortex finder height (S/D), vortex finder diameter (De/D) and total cyclone height (Ht/D).  The optimization was then conducted to include these five variables that significantly affected the collection efficiency and neglected the remaining other two variables.  The optimization computation was run in the Design Expert statistical software by setting a maximum possible value for the collection efficiency. The maximum collection efficiency of 91.244% was obtained when the independent variables of inlet height a/D=0.8, inlet width b/D=0.38, vortex finder height S/D=0.69, vortex finder diameter De/D=0.575 and total cyclone height Ht/D=3.12.  Validation of this statistical finding was tested again and compared with the result of Muschelknautz model calculation to give a significantly small error of 0.82%