Design of Wind Turbine Blade with Thick Airfoils and Flatback and its Aerodynamic Characteristic
large-scaled blade has posed many problems related to design and production. After introducing the features of blade with thick airfoils and flatback, based on relevant parameters of Huaren 100 kW wind turbine, the paper designed blade with thick airfoils and flatback, introduced blade parameter design, and analyzed the aerodynamic performance of blades using GH bladed software, obtaining the relationship between power output of wind turbine with blade tip speed ratio Cp. Furthermore, it analyzed the aerodynamic performance of original design blades, modified blades and Huaren 100 kW blades, and assessed the aerodynamic performance of modified blade.
Effect of Air-Ducted Blade Design on Horizontal Axis Wind Turbine Performance
Wind turbines without pitch control are more preferable from economical point of view but aerodynamic stall affects them more and after a critical wind speed local boundary layer separation occurs. Consequently, their power production is relatively low. In this study, air ducts added on the blade and using the airflow from them the kinetic energy of the low-momentum fluid behind the surface was increased and delay of separation of the boundary layer from the surface was examined The Response Surface Optimization method was utilized in order to get the best possible design under the constraints and targets arranged for the parameters termed the diameter, slope, number and angle of attack of the air ducts. By using computational fluid dynamics analysis, optimum parameter values were obtained and air-ducted and air-duct free blade designs were compared. An improvement in power coefficient between 3.4–4.4% depending on wind speed was achieved with the new design. Due to increase in viscous forces, more power from the rotor obtained by opening air ducts up to a critical number. However, the results showed that after the critical number of air duct addition of more duct on the blade reduced the power coefficient.
Contractor Failure: Analysis
The possibility exists for any construction contractor to fail to filfill the contract requirements associated with a facility. Contractor failure occurs when a contractor is unable to perform his/her contractual duties, thus requiring the facility owner to invoke the contract's nonperformance clause. This paper provides aggregate contractor business failure statistics and outlines potential causes for failure. A framework to identify and quantify the associated costs is also introduced. Several case studies are presented to examine the cause and cost of failure and the means by which the facilities were completed. Alternatives available for project completion when contractor failure occurs are discussed. Recommendations to identify and monitor contractors at high risk for failure are outlined as well. This paper provides facility owners with a greater awareness of the possibility of contractor failure, how to quantify costs of contractor failure, and avoidance techniques.