R. S. Amano

Computational Analysis of Self-Healing in a Polymer Matrix With Microvascular Networks

For the last decade, many researchers have been working to develop self-healing materials, and have obtained good results in the field of polymers, these components with microencapsulated healing agent have exhibited noticeable mechanical performance and regenerative property The research described in this paper applies the concept of self healing to simulate self healing polymer matrix composites, with the aid of models developed by the authors for the manufacturing processes and self-healing behavior. The development of self-healing is a novel idea that has not been totally explored in great detail yet. The concept of self-healing described in this paper consists of simulation of a healing agent dicyclopentadiene (DCPD) inside of a microvascular network within a polymer matrix coating with catalyst forming a self-healing composite (SHC). When this SHC is damaged or cracked, the healing agent by capillary action will flow inside of the microvascular network; when the liquid enter in contact with the catalyst will form a polymer structure and sealing the crack. The study consists of theoretical analysis and Computational Fluid Dynamics of a self-healing polymer. The objective of the study reported here was to find the influence and efficiency of the microvascular network in healing a polymer matrix. To check this effect a computational model was created to simulate the healing treatment, thus a crack was created on the matrix surface piercing the microvascular network filled with healing agent and the method to simulate healing behavior of the composite allows assessment of the effects of the autonomously repairing repeated damage events.Copyright

Development of a Low Flow Coefficient Single Stage Centrifugal Compressor

A low flow coefficient unshrouded centrifugal compressor would give up clearance in relation to the span of the blades, because centrifugal compressors produce a sufficiently large pressure rise in fewer stages. This problem is more acute for a low flow high-pressure ratio impeller. The large tip clearance would cause flow separations, and as a result it would drop both the efficiency and surge margin. Thus a design of a high efficiency and wide operation range for a low flow coefficient centrifugal compressor is a great challenge. This paper describes a new development of high efficiency and large surge margin low flow coefficient (0.145) centrifugal compressor. A viscous turbomachinery optimal design method developed by the authors for axial flow machine was further extended and used in this centrifugal compressor design. The new compressor has three main parts: impeller, a low solidity diffuser, and volute. The tip clearance is under special consideration in this design to allow impeller insensitiveness to the clearance. A three-dimensional low solidity diffuser design method is proposed and applied to this design. This design is successful in extending the low solidarity diffusers to high-pressure ratio compressor. It is demonstrated that the design is a great success. The design performance range of the total to static efficiency of the compressor is about 85% and stability range is over 35%. The experimental results show that the test results are in good agreement with the design.

EXPERIMENT AND COMPUTATIONAL ANALYSIS OF SELF-HEALING IN AN ALUMINUM ALLOY

The development of self-healing metals is a novel idea that has not been explored in great detail yet. The concept of self-healing described in this paper consists of incorporating a low temperature melting alloy imbedded within a higher temperature alloy to create a self healing composite (SHC). When the SHC is damaged or cracked, heat may be applied to the affected area whereupon the low melting alloy will melt and flow into the crack healing the damage and sealing the crack. This study consists of theoretical analysis and design of self-healing in aluminum alloy matrix. The experimental and Computational Fluid Dynamics of a self-healing were designed by the authors, the design consists in an aluminum alloy matrix reinforced with microtubes of alumina (Al2O3) that are filled with a low melting point solder alloy. The objective of the study reported here was to find the influence and efficiency of a low melting solder alloy in healing an aluminum matrix. To check this effect a crack was created in the metal surface, piercing the microtube(s) filled with solder, and then the SHC was heated above the melting point of the solder alloy to melt and examine the flow of molten solder alloy into the crack. NOMENCLATURE

Aerodynamic Comparison of Straight Edge and Swept Edge Wind Turbine Blade

= oncoming wind speed � = density of air A = swept area of rotor Pmax = maximum power that can be extracted from wind T = thrust force L = lift force Va = apparent wind speed Cl = coefficient of wind � = angle of twist R = radius of rotor r = local radius C = chord length � = tip speed ratio B = number of blades I. Abstract Recently there has been an increase in the demand for the utilization of clean renewable energy sources. This is a direct result of the volatility in oil prices and an increased awareness of human induced climate change. Wind energy has been shown to be one of the most promising sources of renewable energy. With current technology, the low cost of wind energy is competitive with more conventional sources of energy such as coal. Most blades available for commercial grade wind turbines incorporate a straight span wise profile and airfoil shaped cross sections. These blades are found to be very efficient at lower wind speeds in comparison to the potential energy that can be extracted. However as the oncoming wind speed increases the efficiency of the blades decreases as they approaches a stall point. This paper explores the possibility of increasing the efficiency of the blades at higher wind speeds while maintaining efficiency at the lower wind speeds. The design intends to maintain efficiency at lower wind speeds by selecting the appropriate orientation and size of the airfoil cross sections based on a low oncoming wind speed and given constant rotation rate. The blades will be made more efficient at higher wind speeds by implementing a swept blade profile. The torque generated from a blade using only the first optimization technique is compared to that generated from a blade using both techniques as well as that generated by NTK500/41 turbine using LM19.1 blades. Performance will be investigated using the CFD solver FLUENT.

CFD Analysis of Wind Turbine Blade With Winglets

This study is aimed at investigating the aerodynamic performance of the wind turbine blade with winglets and compares its performance in terms of the power generated with a regular straight blade without winglet. Adding a winglet to the wind turbine blade improves the power production without increasing the projected rotor area. A parameter study is carried out where two of the key parameters which describe a winglet design namely the cant angle and the winglet height are varied. The winglet is bent towards the pressure (upstream) side. Pro/ENGINEER is used to generate a straight wind turbine blade which is then modified in SPACECLAIM to attach a winglet to it. Single blade analysis approach is chosen to carry out the computation, as this involves less computational time and low cost. Results show that adding a winglet to a straight blade increases its power output by 2% to 20%. In addition, winglet which has a cant angle of 45° performs better, generating more power than the winglet which is perpendicular to the blade (cant angle 90°). Also, the power generation increases with the increase in the winglet height. Amongst the four winglet designs discussed, the design W4 with cant angle of 45° and winglet height of 4% rotor radius performs the best resulting in 20% improvement in the power generation when added to a straight blade.Copyright

Numerical Investigation and Experimental Lab Setting-Up for Analysis of Gas Turbine Combustor Dilution Process

A gas turbine combustor dilution process is modeled numerically using both 2-D and 3-D approaches, then an experimental set-up was designed and built for validation using standard air ducts. The combustor model is used to test various air cooling strategies with the goal of uniformly diluting combustion gas before it enters the turbine section. The high temperature combustion gas (simulated as hot air) is cooled by introducing a lower temperature secondary air flow through perforated plates. First a 2-D simulation was conducted to compare between introducing the dilution air from smaller but large number of holes or larger but smaller number of holes. It was found that the larger holes are more effective especially when pressure drop is taken into consideration. Then a 3-D simulation was run with larger holes for different configurations and the experimental set up was constructed accordingly. The temperature profile at the exit of the dilution section is considered the criteria for testing the uniformity of temperature after the dilution process, and it will be measured in the experimental work.This paper presents a brief discussion on the importance of cooling combustion exit gas uniformly before it enters the turbine section. With this in mind, a testing concept is derived in order to gauge methods of improving this cooling. Detailed design specifications and initial conclusions are also outlined. Initial conclusions have yielded a desired primary airflow of 6 m/s (19.7 ft/s) and primary duct diameter of 0.4 m (16 in). With this information it was determined that the flow rate required by the fan is 1.727 m3/s (3660 CFM).Copyright

Design and Analysis of Wind Turbine Blades: Winglet, Tubercle, and Slotted

Energy is the heart of today’s civilization and the demand seems to be increasing with our growing population. Alternative energy solutions are the future of energy, whereas the fossil-based fuels are finite and deemed to become extinct. The design of the wind turbine blade is the main governing factor that affects power generation from the wind turbine. Different airfoils, angle of twist and blade dimensions are the parameters that control the efficiency of the wind turbine. This study is aimed at investigating the aerodynamic performance of the wind turbine blade. In the present paper, we discuss innovative blade designs using the NACA 4412 airfoil, comparing them with a straight swept blade. The wake region was measured in the lab with a straight blade. All the results with different designs of blades were compared for their performance. A complete three-dimensional computational analysis was carried out to compare the power generation in each case for different wind speeds. It was found from the numerical analysis that the slotted blade yielded the most power generation among the other blade designs.Copyright

Wind Turbine Blade Design and Analysis With Tubercle Technology

The objective of this project is to construct a CAD model for tubercle wind turbine. Once the model is developed a complete CFD analysis of the flow pattern around the wind turbine will be carried out. The main objective of the study is to analyze and compare the performance of the tubercle wind turbine with the usual wind turbine. The power developed by both the turbine blades can be compared to support the use of tubercle. The tubercles are very effective for increasing the lift without stalling. The main objective of this project is to study the aerodynamic advantages of tubercle turbine blade. The effort will be to compare the obtained results with the straight blade of the same airfoil. This will provide insight into the advantages of using the tubercle blade. This technology being new the study is done numerically to study the overall effect of the tubercle.Copyright

Computational Study of Gas Turbine Blade Cooling Channel

It has been a common practice to use cooling passages in gas turbine blade in order to keep the blade temperatures within the operating range. Insufficiently cooled blades are subject to oxidation, to cause creep rupture, and even to cause melting of the material. To design better cooling passages, better understanding of the flow patterns within the complicated flow channels is essential. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. Power output and the efficiency of turbine are completely related to gas firing temperature from chamber. The increment of gas firing temperature is limited by the blade material properties. Advancements in the cooling technology resulted in high firing temperatures with acceptable material temperatures. To better design the cooling channels and to improve the heat transfer, many researchers are studying the flow patterns inside the cooling channels both experimentally and computationally. In this paper, the authors present the performance of three turbulence models using TEACH software code in comparison with the experimental values. To test the performance, a square duct with rectangular ribs oriented at 90° and 45° degree and placed at regular intervals. The channel also has bleed holes. The normalized Nusselt number obtained from simulation are validated with that of experiment. The Reynolds number is set at 10,000 for both the simulation and experiment. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. The three-dimensional turbulent flows and heat transfer are numerically studied by using several different turbulence models, such as non-linear low-Reynolds number k-omega and Reynolds Stress (RSM) models. In k-omega model the cubic terms are included to represent the effects of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. The finite volume difference method incorporated with the higher-order bounded interpolation scheme has been employed in the present study. The outcome of this study will help determine the best suitable turbulence model for future studies.Copyright

On the Development of Turbomachine Blade Aerodynamic Design System

A turbomachine blade aerodynamic design process is proposed to design turbomachine blades. The design system, including a global optimization of through flow for whole machine and a local optimization of the airfoil design and airfoil section, stacks up. The airfoil generator code employs Bezier polynomial curves to produce smooth airfoil shapes. A meanline program combined with an optimizer was used to perform the global optimization. In the airfoil section design, for fast calculations of the airfoil pressure distributions a discrete vortex method is developed. A novel Navier-Stokes (N-S) solver is developed for further examination of the airfoil performance for final section design. The N-S code is used to obtain the blade-to-blade quasi-three-dimensional, turbulent, and viscous flow characteristics. The time-dependent N-S equations are discretized and integrated in a coupled manner based on a finite-volume formulation, as well as a flux-difference splitting. The flux-difference splitting method enables us to compute with a rapid convergence. The present N-S code can handle computations of both subsonic and supersonic flows and can be connected to an external optimizer code with the airfoil generator. After optimized airfoil was designed, a three-dimensional code was used for final tuning of the design.