The impact of porous media heterogeneity on non-Darcy flow behaviour from pore-scale simulation

The effect of pore-scale heterogeneity on non-Darcy flow behaviour is investigated by means of direct flow simulations on 3-D images of a beadpack, Bentheimer sandstone and Estaillades carbonate. The critical Reynolds number indicating the cessation of the creeping Darcy flow regime in Estaillades carbonate is two orders of magnitude smaller than in Bentheimer sandstone, and is three orders of magnitude smaller than in the beadpack. It is inferred from the examination of flow field features that the emergence of steady eddies in pore space of Estaillades at elevated fluid velocities accounts for the early transition away from the Darcy flow regime. The non-Darcy coefficient β, the onset of non-Darcy flow, and the Darcy permeability for all samples are obtained and compared to available experimental data demonstrating the predictive capability of our approach. X-ray imaging along with direct pore-scale simulation of flow provides a viable alternative to experiments and empirical correlations for predicting non-Darcy flow parameters such as the β factor, and the onset of non-Darcy flow

Preparation and Characterization of Bao.6fe2o3 Bonded Magnet with Particle Size Variation

Bonded magnets BaO.6Fe2O3 with various grain size i.e. 74, 105, 150, 300, 425, 600 and 850 μm have been synthesized. Composition of BaO.6Fe2O3 and epoxy was fixed i.e. 97 : 3 in weight percent. Turbidity and true density test associated its correlation by grain size. The result shows that turbidity SD BaO.6Fe2O3 and the square root of average particle diameter have linear relationship. True density value of BaO.6Fe2O3 around 5.2-5.6 g/cm3. This magnet powder molded cilindrical, magnetized, burned and then measured its physcal properties. Correlation between density and grain size is inversely proportional. The maximum density is 3.12 g/cm3 for BaO.6Fe2O3 until size 74 μm. At the same size have hardness brinell maximum 26 HB and inductance remance (Br) maximum 1.23 kG. The results of this study show that the smaller the particle size does not directly increase the magnetic field strength generated. This phenomenon needs to be seen again by linking themicro-structure correlation, homogeneity, and the improvement of the printing process with a strong magnetic field

Preparation and Characterization of Bao.6fe2o3 Bonded Magnet with Particle Size Variation

Bonded magnets BaO.6Fe2O3 with various grain size i.e. 74, 105, 150, 300, 425, 600 and 850 μm have been synthesized. Composition of BaO.6Fe2O3 and epoxy was fixed i.e. 97 : 3 in weight percent. Turbidity and true density test associated its correlation by grain size. The result shows that turbidity SD BaO.6Fe2O3 and the square root of average particle diameter have linear relationship. True density value of BaO.6Fe2O3 around 5.2-5.6 g/cm3. This magnet powder molded cilindrical, magnetized, burned and then measured its physcal properties. Correlation between density and grain size is inversely proportional. The maximum density is 3.12 g/cm3 for BaO.6Fe2O3 until size 74 μm. At the same size have hardness brinell maximum 26 HB and inductance remance (Br) maximum 1.23 kG. The results of this study show that the smaller the particle size does not directly increase the magnetic field strength generated. This phenomenon needs to be seen again by linking themicro-structure correlation, homogeneity, and the improvement of the printing process with a strong magnetic field

Phase Analysis and Magnetic Properties of Bafe12o19/nd2fe14b Composite by Mechanical Milling Product

The synthesis and characterization of BaFe12O19/Nd2Fe14B composite by use mechanical milling has been performed. The result of refinement of X-ray diffractions showed that the sample consist of two phases namely BaFe12O19 and Nd2Fe14B phase with fraction mass were 79.89 and 20.11 wt%, respectively. The BaFe12O19 system magnetic materials have been formed with the crystal structure of hexagonal (space group P 63/m m c), lattice parameter are a = 5.9033(5) Å, b = 5. 9033(5) Å and c = 23.239(2) Å, α = β = 90o and γ = 120o, V = 701.3(1) Å3 and ρ = 5.7172 g.cm-3. The Nd2Fe14B system magnetic materials have been formed with the crystal structure of tetragonal (space group P 42/m n m), lattice parameter are a = 8.865(8) Å, b = 8.865(8) Å and c = 12.269(1) Å, α = β = γ = 90o, V = 964.3(1) Å3 and ρ = 7.7508 g.cm-3. The magnetic properties result of Nd2Fe14B shown that the sample has the coercive field and remanence magnetization are 7984 Oe and 5250 Gauss, respectively. The BaFe12O19 are 1625 Oe and 1190 Gauss, respectively. And the BaFe12O19- Nd2Fe14B composite increase to become 2650 Oe and 1580 Gauss, respectively. We conclude that the process of mixing between BaFe12O19 and Nd2Fe14B is not affect the change of each phase. The BaFe12O19 particle can be use as the shielding of the Nd2Fe14B particle from it's the corrosion properties. The BaFe12O19 magnetic material has a stable structure at room temperature, so that this structure was not easy of change after mix with the Nd2Fe14B particles

Validation of Wind Power Plant Dynamic Models: Preprint

This paper discusses the process of wind model validation against field measurements

PENURUNAN KADAR BOD LIMBAH CAIR SECARA PROSES BIOLOGI DENGAN TIPE ROTATING BIOLOGICAL CONTACTORS (RBCs)

Generally liquid waste from house hold and industries contain of BOD, COD, and TSS at the highly sufficient concentration. Handling the problems of liquid waste pollution, the development of biologic liquid waste treatment installations was needed. Rotating Biological Contactors (RBCs) was one of the liquid waste treatment process that include in biologic treatment by an aerobic way. The research has been done by analyzing the characteristics of liquid waste which contains BOD so that RBCs was required. It was hoped that by having done the treatment, BOD can be reduced in order to fill the standard of liquid waste quality of PT. Sarasa Nugraha Tbk in Karanganyar. The purposes of the research were to know the suitable RBCs’ dimension with the capability in reducing BOD, to know the ability of “ijuk” as media for the growing of aerobic bacteria, and to know the efficiency of RBCs. The research used an RBCs installation on laboratory scale with six variations of time such as 1 hour, 2 hour, 4 hour, 6 hour, 24 hour, and 48 hour for samples analyzing. The input of liquid waste contained 2006 mg/l of BOD. After the treatment had been done with the six variations of time, BOD decreased chronologically – 1816mg/l of BOD in 1 hour, 1624 mg/l of BOD in 2 hours, 148 mg/l of BOD in 4 hours, 1023 mg/l of BOD in 6 hours, 941 mg/l of BOD in 24 hour, and 933 mg/l of BOD in 48 hours. It can be concluded that RBCs can reduced the BOD concentration in the liquid waste of PT. Sarasa Nugraha Tbk in Karanganyar. We can also knew that ‘ijuk’ was an effective media for the growing of bacteria that was indicated with the high decreasing of BOD. Keywords: Rotating Biological Contactors, BOD, aerobic treatment

A conservative control strategy for variable-speed stall-regulated wind turbines

Simulation models of a variable-speed, fixed-pitch wind turbine were investigated to evaluate the feasibility of constraining rotor speed and power output without the benefit of active aerodynamic control devices. A strategy was postulated to control rotational speed by specifying the demanded generator torque. By controlling rotor speed in relation to wind speed, the aerodynamic power extracted by the blades from the wind was manipulated. Specifically, the blades were caused to stall in high winds. In low and moderate winds, the demanded generator torque and the resulting rotor speed were controlled to cause the wind turbine to operate near maximum efficiency. Using the developed models, simulations were conducted of operation in turbulent winds. Results indicated that rotor speed and power output were well regulated. Preliminary investigations of system dynamics showed that, compared to fixed-speed operation, variable-speed operation caused cyclic loading amplitude to be reduced for the turbine blades and low-speed shaft and slightly increased for the tower loads. This result suggests a favorable impact on fatigue life from implementation of the proposed control strategy

Method of Equivalencing for a Large Wind Power Plant with Multiple Turbine Representation: Preprint

This paper focuses on our effort to develop an equivalent representation of a Wind Power Plant collector system for power system planning studies