The wind-lens technology attracts extensive attention due to its promising performance. A numerical study was carried out to investigate the effects of diffuser flange inclination angle (phi) and the diffuser flange depth inside the exit of the diffuser (h(i)/D-rotor) on the wind-lens turbine system performance. Besides, the effect of wind speed is taken into consideration. phi is changed through the range of 15 degrees to 15 degrees with a step of 5 degrees in both forward and backward directions. Also, h(i)/D-rotor is changed through the range of 0-0.06 with a step of 0.02 and wind speed of (8 and 10 m/s). A CFD model was developed and solved by using ANSYS FLUENT 16.2. Such model was validated by using previous published experimental results with good agreement and maximum deviation of 2.4%. It was found that the percentage increase of C-p at different values of phi was increased by augmenting of lambda. Thus, it is emphasized that the maximum percentage increase of C-p of 28% was obtained at lambda of 5.6 and phi of 10 degrees. Moreover, a theoretical correction of C-p was performed to achieve that the actual power coefficient C-pact never exceeds Betz limit. (C) 2018 Elsevier Ltd. All rights reserved.