Research On The Ventilation Resistance Characteristics Of Outlet Shaftin Baihetan Hydropower Station

Superior performance of water resources and the current serious energy shortage,make the hydropower station occupy a very important position in China’s energyconstruction. The ventilation, air conditioning and smoke control systems in theunderground hydropower station，which were constituted by transportation hole, plant,bus hole, main transformer hole, outlet channel, into the wind tunnel, tunnel row andspecially laid send exhaust piping system. Ventilation, air conditioning and smokecontrol systems are crucial to generate environmental and operate safely in theunderground power station.As an important part of the underground hydropower station ventilation system, theadvantages and disadvantages of ventilation of the outlet well will directly affect theair temperature, relative humidity, the normal operation of concentration of harmfulgases, hydroelectric plant’s ventilation and mechanical equipment. When outlet welluses mechanical ventilation fan, the proper selection and rational use of the fan aresignificant for protection of electrical and mechanical equipment for normal, safe andefficient operation, duty and physical health as well as energy saving equipment.Therefore, it is necessary to make detailed analysis of the ventilation flow resistancecharacteristics of the outlet well.This article is one of the National Natural ScienceFoundation of surface projects (51178482)"Deep Underground Station ThermalEnvironment and Energy Regulation formation mechanism," the study content.There is a layer of steel grille every certain distance, it has enough intensity tomake it convenient for the staff to maintain and overhaul the devices in the outlet shaft.As the unique channel in the underground hydropower station, there is no formula tocalculate the air flow resistance of the outlet shaft. So it can only be obtained by meansof model tests.The results of model tests are true and reliable, but they also take timeand money. In this paper, it will make a combination method of experimental andnumerical simulation model, research and analysis the flow resistance characteristics inthe underground hydropower station outlet shaft, summarize certain rules to guide theconstruction of similar projects in the future.First, based on a similar theory and model test principal, a similar model test of theoutlet shaft was designed. Through a similar model test, a equivalent of the frictionFactor λe in the outlet shaft came out, and then the ventilation flow resistance of the qualifying well could be calculated. Comparing the CFD numerical simulation andmodel test results, the feasibility and reliability of the CFD numerical simulationmethod for the study of shaft ventilation could be verified. Next, with this method,research and analysis the sectional shape, structure and effective ventilation coefficientof the grille, the space between the grid, which can affect the outlet shaft ventilationflow resistance characteristics.Below are the research and analysis obtained:①The impact of the sectional shape of the ventilation shaft on flow resistancecharacteristics small is small;②Steel grille aperture density must be kept within a certain range, the impact ofthe grid structure on the outlet shaft flow resistance characteristics can be negligible.③In the shaft,when the space between the grid is fixed, with the increasing of theeffective ventilation grille coefficient, the equivalent of the Friction Factor outlet shaftwill be gradually reduced. When the effective ventilation coefficient of the grille is lessthan0.76, it has a greater impact on the outlet shaft. With the increasing of coefficient,there will be a sharp decline of the equivalent of the friction factor. When the effectiveventilation coefficient of grille is greater than0.76, with the increasing of coefficient,the equivalent of the friction factor will vary gently, tend to be a fixed value.④Since the grid is a partial member, when the space between the grid is small, theinteraction between the partial elements affect each other, resulting in an enhance of thedisturbance of the flow and a larger flow resistance of the outlet shaft. As the spacebetween the grid increases, the influence between the grid will gradually weaken, theflow resistance of outlet shaft will tend to be a fixed value.The results above show that the equivalent of the friction factor of outlet shaftdepends primarily on the effective ventilation coefficient of the pitch between the grilleand grille. In order to make it easy for selection of the ventilation system design andpower equipment in future similar projects, when effective ventilation coefficient of thegrille is0.6-0.9, the space between grille pitches is1de-4de, use CFD numericalsimulation methods to get outgoing shaft equivalent of the Friction Factor. According tothe simulation results to plot a graph, similar projects can take it as a reference in thefuture.The article also get the ventilation flow resistance of outlet well based onequivalent studies along the way and get access to relevant information. And furtherdiscuss the different seasons, as the difference between indoor and outdoor air density and the size of the outlet hot import and export elevation wells formed to provideguidance for proper ventilation engineering design to match the power of the device.