Abstract: A case study is conducted on a utility tunnel project of the Beijing New Airport Expressway, and the ventilation laws and effects of power cabin are systematically examined using numerical simulations and field experiments. Then, by changing the ventilation mode, the position of the vents, and the layout of the cable, the ventilation effects are studied and compared under three types six working conditions, including the mechanical air intake and natural air emission, the vent set on the top and both sides of the tunnel, and the exchange position of the 10 kV and 110 kV cables. The results show the following: (1) Under the existing normal ventilation conditions, the air flow at the air inlet is chaotic. At the same time, the air flow at the air inlet changes the direction of movement twice, resulting in a large energy loss. As a result, the energy that can be used to drive the air in the utility tunnel is reduced, the ventilation effect is reduced, and energy is wasted. (2) When the vents(fans) are arranged on both sides of the power cabin, the initial wind speed is consistent with the ventilation direction, which avoids energy loss and effectively improves the ventilation effect. According to the research, the average wind speed of the middle section is increased by 0.31 m/s, the amplitude is 39.6 %, the temperature is reduced by 1.6 ℃, up to 6.1 %, and the pressure loss is reduced by 13.7 Pa, up to 30.4 %, which greatly improves the ventilation effect of the power cabin. (3) With the ventilation vents(fans) arranged on the top, after optimizing the cable layout, the surface temperature of the 10 kV cable is reduced by 3.21 ℃, the surface temperature of the 110 kV cable is increased by 1.68 ℃, and the average temperature of the longitudinal section is reduced by 0.365 ℃. After the adjustment of the cable layout, it is beneficial to reduce the temperature in the cabin and the pressure loss.

Key words: electric power tunnel, ventilation pattern, numerical simulation, ventilation optimization