Computational Fluid Dynamics Simulation of the Effect of Guide-vane Angles on the Performance of the Exhaust Air Energy Recovery Turbine Generator

Abstract

An exhaust air energy recovery turbine generator is designed to recover part of the energy in the discharged air from an exhaust air system. The design is a combination of H-rotor vertical axis wind turbines (installed in cross-wind position), guide-vanes and a diffuser. Its working principle was tested on a scaled model of cooling tower and simulated in a computational fluid dynamic (CFD) package. From the guide-vanes study, optimum guide-vanes arrangement is 100°, 70° and 90°. The system with optimized guidevanes arrangement produced the highest torque coefficient compared to the other configurations. The average torque coefficient of the system was increased by 24.3% with the introduction of diffuser and guide-vanes at optimized angles, i.e. from 0.029 to 0.036. From the graph of the torque coefficient versus azimuth angle, the overall positive torque zone was increased with the introduction of the guide-vanes with optimum configuration. The exhaust air energy recovery turbine generator can be another green technology that recovers waste energy from the discharged wind of an exhaust air system for urban areas.

Study On the Potentiality of Power Generation from Exhaust Air Energy Recovery Wind Turbine: A Review

“…8. Torque coefficient for the system without diffuser and guide-vanes, and the system with diffuser and guide-vanes at optimized angles [58] Then, with the presence of the VAWT, a minor difference in power consumption by the fan motor was discovered in a research by Chong et al, [51], which was 0.39% higher. It showed that, there is no significant difference in air intake speed or current consumption of the power-driven fan was observed when the turbine rotated above the cooling tower in laboratory test and the outlet air speed of an actual induced-draft cooling tower showed no substantial variations in a field test.…”

“…Henceforward, to absorb the more wind energy from the exhaust air system, two VAWTs are combined with the enclosure (which includes multiple guidance valves and two diffuser plates). Multiple air flow channels are formed between the exhaust outlet and the VAWTs by guide valves, which direct the exhaust wind in the most efficient direction on the turbine blade [56][57][58][59][60][61]. Nonetheless, a hybrid, non-destructive assessment approach is proposed to investigate the dynamic behaviour and reliability of this new design, which examines the possible causes of high vibration and corrects the vibration issue [62].…”

“…Based on Poh et al, [58], the design combination of H-rotor vertical axis wind turbines (installed in cross-wind position), guide-vanes and a diffuser were examined on a scaled cooling tower model. Computational Fluid Dynamic (CFD) package and ANSYS FLUENT 14.0 was used to conduct a numerical study of the VAWT exhaust air energy recovery turbine generator performance.…”

“…6. Discharge wind speed profile [57] According to the numerical results from Computational Fluid Dynamic (CFD) in a study by Poh et al, [58] showed the highest wind speed was more than 9 m/s at a radius of about 200 mm, while the lowest wind speed was about 2 m/s near the outer radius as displayed in Figure 7 where the measurements were conducted at 50mm from the exhaust air outlet. CFD simulations were carried out in two separate configurations of energy recovery turbine generators which are with and without diffuser guide-vanes.…”