A Review on Generation and Mitigation of Airfoil Self-Induced Noise

A review on passive acoustic control of airfoil self-noise by means of porous trailing edge is presented. Porous surfaces are defined using various terms such as porosity, permeability, resistivity, porosity constant, dimensionless permeability, flow control severity and tortuosity. The primary purpose of this review paper is to provide key findings regarding the sources and mitigation techniques of self-induced noise generated by airfoils. In addition, various parametric design concepts were presented, which are critically important for porous-airfoil design specifications. Most research focus on experimentation with some recent efforts on numerical simulations. Detail study on flow topology is required to fully understand the unsteady flow nature. In general, noise on the airfoil surface is linked to the vortex shedding, instabilities on the surface, as well as feedback mechanism. In addition, acoustic scattering can be minimized by reducing extent of the porous region from the trailing edge while increasing resistivity. Moreover, blowing might also be another means of reducing noise near the trailing edge. Ultimately, understanding the flow physics well provides a way to unveil the unknowns in self-induced airfoil noise generation, mitigation, and control.

Coal Flowability Control on Preventing Spillage on Conveyor Belt Through Modeling and Simulation for Improving its Performance

Belt conveyors are generally used in mining plant areas, both surface and underground mines. The belt conveyor is mainly applied to transport the extracted bulk material from the mining site to delivery. The effectiveness of the extraction process depends on the reliability and durability of the conveyor belt system. In addition, conveyor performance is very important specially to control material flowability to prevent spills or other operational disturbances to optimize production throughput. However, the transfer chute and settling zone can cause some problems during the transfer process, such as material spills. This problem can reduce the function and performance of the conveyor belt. This paper discusses a design model to reduce the problem of spillage in the settling zone. The model was developed by compiling the previous defecting data from the durability of the conveyor system, then analyzed using Discrete Element Method (DEM) software and compared with bulk characteristics. The initial performance of certain conveyors is only capable of serving with an average production of 76% of the designed capacity while energy is consumed at full load. By applying the DEM simulation result, the blade gate can reduce the peak angle break in the depositional zone before exiting. After the analysis is completed using DEM, the conveyor increases the average production to 95% of the designed capacity. In conclusion, controlling the maximum belt load without spillage will reduce interruption on conveyor belt operation and maintenance costs therefore increase plant reliability and availability.

Metals and Alloys Additives as Enhancer for Rocket Propulsion: A Review

A rocket's engine usually uses fuel and oxygen as propellants to increase the rocket's projection during launch. Nowadays, metallic ingredients are commonly used in the rocket’s operation to increase its performance. Metallic ingredients have a high energy density, flame temperature, and regression rate that are important factors in the propulsion process. There is a wide range of additives have been reported so far as catalysts for rocket propulsion. The studies show that the presence of metal additives improves the regression rate, specific impulse and combustion efficiency. Herein, the common energetic additives for rocket propulsion such as metal and light metals are reviewed. Besides the effect of these energetic particles on the regression behaviors of base (hybrid) fuel has been exclusively discussed. This paper also proposed a new alloy namely high entropy alloys (HEAs) as a new energetic additive that can potentially increase the performance of the rocket propellant system.

Magnetohydrodynamic Flow Past a Nonlinear Stretching or Shrinking Cylinder in Nanofluid with Viscous Dissipation and Heat Generation Effect

The Tiwari-Das model is used to investigate magnetohydrodynamic stagnation point flow and heat transfer past a nonlinear stretching or shrinking cylinder in nanofluid with viscous dissipation and heat generation using. The partial differential equations, also known as governing equations, were reduced to nonlinear ordinary differential equations using similarity transformation. MATLAB with the bvp4c solver is used for numerical computing. The controlling parameter, such as nanoparticle volume fraction, magnetic, curvature, nonlinear, radiation, and heat generation parameters, as well as Eckert and Grashof numbers, influence the skin friction coefficient, heat transfer rate, velocity, and temperature profiles. The results are presented as graphs to show the influence of the variables studied. In some circumstances of stretching and shrinking cases, dual solutions can be obtained.

Investigation Of Dual-Pump Fiber Optical Parametric Amplifier Performance Driven by Energy Transfer Between Four-Wave Mixing Process

Fiber optical parametric amplifier (FOPA) is operated based on energy transfer from pump waves to signal wave and at the end of the fiber, an idler wave is generated. This process is called four-wave mixing (FWM). Even though effects of higher-order dispersion coefficients, fiber length, fiber nonlinearity, fiber attenuation, pump powers, pump wavelength separation and distance of central pump wavelength with ZDW on gain profiles have been examined by previous researchers, but on different fiber or numerically studied using the Optisys system, analytical model or different amplitude equations. Thus, in this study, the above-mentioned parameters on the gain performance of dual pump fiber optical parametric amplifier (FOPA) using highly nonlinear shifted fiber (HNL-DSF) as a medium will be numerically investigated using ode45 function in Matlab. The gain at a certain wavelength can be obtained by solving 4 coupled amplitude equations with fiber loss and pump depletion that govern the four-wave mixing (FWM) process of pumps, signal and idler waves. Simulations results indicate positive gives poor or no gain, meanwhile, an addition of to negative widens the bandwidth, but there is no significant effect with the addition of . Besides, an increase of fiber length, nonlinearity and pump powers improve gain performance, but an increase of fiber loss decays the gain amplitude. Increment of pump separation will enhance flatness of gain at wavelength far from central wavelength but results in an increase of gain reduction at the central wavelength. Lastly, must be positive, not too small and not bigger than 1.125nm to get a high, broader and lesser ripples gain.

Fluid and Structure Analysis of Wind Turbine Blade with Winglet

One of the succeeded methods to enhance the performance of horizontal axis wind turbine (HAWT) is an attaching a winglet to the blades tip. The current paper study the effect of four key parameters that are used to describe the winglet on the performance of wind turbine which are winglet height H%R, cant angle θ, twist angle β, and taper ratio Λ. A five design cases for each geometric parameters were numerically investigated using computational fluid dynamics (CFD) by ANSYS18.1 software, which totally give a twenty different response. A validation of present computational model with reference experimental results successfully carried out with maximum inconsistency of 3%. A mathematical correlation was established from the CFD results and being used in predicting the turbine power for the different winglet geometric parameters. From CFD and mathematical correlation response, the effect of H and θ were greater than β and Λ on the turbine power. The epoxy E-glass unidirectional material was selected for current study to investigate the effect of winglet on blade structure. The power increases by 2% to 30% due to adding winglet to a wind turbine blade. The maximum power increment corresponds to the design case of W6 with H= 8%R, =30°, β = 3°, and Λ = 0.8. Form the structural analysis the addition of winglet changes the stress distribution over the blade, increasing stresses at the blade root, and achieved the transfer of the maximum deformation from the blade tip to the winglet tip.

Experimental Investigation on Filtration and Cooling Effect of Kitchen Hood Ventilation System from Water-Mist Recirculation Spray: Water-Mist Spray Cycle

A Water-mist spray system in several heavy-duty kitchen hood canopies is installed to efficiently control the high heat loads and grease emissions produced from the cooking process and for safety purposes. The main purpose of this study is to reduce water consumption by introducing the water-mist recirculation system to replace the current method water-mist system since it is working as water loss. A standard ASTM 2519 and UL 1046 full-scaled experiment is developed in the laboratory. An existing Halton Europe/Asian water-mist operating system is adopted in this study. Twelve (12) cycles (at 24 hours of water-mist activation) have been studied to determine the maximum water-mist activation cycle. The data are collected at two (2) hours water-mist activation at every water-mist recirculation cycle. The water-mist spray fluids viscosity is 0.7 cP from fresh water until the 4th cycle (8 hours water-mist spray) and increase 14.29% (0.8 cP) at the 5th cycle to the 12th cycle. On average, the difference in gas emissions percentage for CO concentration between fresh water until the 4th cycle is 10.81 – 18.92% while the CO2 concentration is 12.33 – 18.22%. On average, the difference in cooling effects percentage for ducting temperature between fresh water until the 4th cycle is 5.55% while the hood temperature is 2.33%. From the study, the water-mist recirculation system could save up to 611,667 litres per year and 466,798.5 litres per year water for all U.S, European, and Asian kitchen hood designs per hood length. By adopting the new water-mist recirculation system to the current water-mist kitchen hood, the water operational cost for water successfully reduced to RM 4,889.63 per year and RM 6,977.86 per year for U.S design and European or Asian design per hood length respectively. The water-mist recirculation system has great potential to improve the current water-mist system for the commercial kitchen hood.

Rheological Properties of TiO2/POE Nanolubricant for Automotive Air-Conditioning System

The enhancement of nanolubricant rheological properties can improve the performance of automotive air-conditioning systems. The rheological properties of the TiO2/POE nanolubricant were investigated in this study at 0.01 to 0.1% volume concentrations and temperatures ranging from 0 to 100°C. TiO2 nanoparticles were dispersed in the base lubricant of Polyol-ester (POE RL68H) lubricant in two steps. The dynamic viscosity was measured with an Anton-Paar Rotational Rheometer. According to the findings, the TiO2/POE nanolubricant behaved as Newtonian fluids at all volume concentrations and temperatures. The dynamic viscosity increment of nanolubricants up to 1.75% only occurred for 0.1% volume concentration and temperature of 90 to 100°C. Meanwhile, when compared to POE lubricant, nanolubricants with volume concentrations of 0.01 and 0.05% showed a decrement trend in dynamic viscosity of up to 1.8%. Finally, the TiO2/POE nanolubricant improved the rheological properties of the POE lubricant for use in automotive air-conditioning systems.

Numerical Study on Aerodynamic Performance of S809 Wind Turbine

Wind energy has emerged as one of the cleanest and sustainable sources of energy and is a potential resource for meeting the future’s electricity demand. Evaluating the aerodynamic performance of the turbine blade in complex environmental conditions is vital for designing and developing energy-efficient wind turbines. This work aims to undertake aerodynamic analysis of a Horizontal Axis Wind Turbine i.e. NREL Phase IV. Computational fluid dynamics (CFD) models are presented using ANSYS-CFX software. Blade geometries were tested at different wind speeds ranging from 5 m/s to 30 m/s. The power output and pressure coefficients obtained from numerical simulations are compared with experimental data published on wind turbine.

Optimization of Reaction Typed Water Turbine in Very Low Head Water Resources for Pico Hydro

The purpose of this research is to investigate the dominant parameters that influence the optimum performance of reaction typed turbine at very low water head. The concepts of conservation of mass, momentum and energy are utilised to explore performance characteristics using a graphical technique. Parametric analysis of the governing equation and experimental results were performed to show that the turbine diameter and nozzle exit area has a dynamic response to mass flow rate, angular speed, output power and efficiency. Depending on the nozzle diameter of (0.01 m, 0.006 m, and 0.008 m) and turbine pipe size with (diameter of 0.025 m and 0.015 m), six versions of prototype turbine Z-blade turbine were produced. All the turbines have been tested at 100 kPa static water pressures and below. According to a variety of experimental data for all types of turbines, the turbine diameter and nozzle exit area have a substantial impact on turbine performance, especially at high water heads. Despite differences in turbine length and nozzle exit area, more than 90 % of the pattern curves for rotational speed, water flow rate, and mechanical power were identical. Overall, the Z-blade turbine Type B outperforms, resulting in higher turbine efficiency at low head and low flow water condition.