| In recent years, the business of hydropower construction in China has been booming and so far, the total installed capacity of hydropower has already breakthrough 230 million KW living the top one in the world. With the increase of the installed capacity, the scale of the hydropower stations also increases accordingly, the structure of underground excavation cluster is more complex, those ventilation paths are interconnected, and the airflow parameters and airflow distribution influence each other in those paths, such as Baihetan hydropower station. The installed capacity of Baihetan hydropower station has reached 16 million KW, and and the scale of the underground chambers is so huge. There are 9 air intakes in the underground house of left side. The traffic hall and its extension, 2 special air inlet tunnels, one ventilation and safety tunnel are planned to be the air inlet channels. There are 5 air inlet channels whose are connected with the outdoor(The traffic hall into the power house of them still contains a side-road to be connected with the outdoor). The elevation of air intakes are different from one another, the biggest difference even reaches up to 252.75 m. Air inlet channels are connected with each other by the multi-tier drainage gallery which surrounds the underground power house, those formed a complex air inlet channel network. There are many big differences with those underground power houses which has only one air inlet channel or whose each air intake has independent air inlet channel. It shows in the following inspects:① The temperature and humidity of the airflow in seach outdoor air intake are different. The air intake of the underground power house and the outdoor air intake do not share a simple one-to-one mapping, even though the air volume of each air intake can be adjusted to the setting value in design by fans and air valves, the air inlet network still exists complex relationship of airflow distribution.② The airflow distribution of each channel of the air inlet network is affected by not only the pressure drop characteristics, but also the thermal pressure. The thermal pressure is determined by the structure of channel network and the temperature of airflow, and the temperature of airflow is determined by the air volume and the heat transfer capacity between the air flow and the channel. So the physical parameters of airflow distribution, heat transfer with the building envelop, temperature of the airflow and the distribution of thermal pressure relate to each other.③ We can get the correct air temperature and humidity of each air intake of the underground power house only by calculating with air volume, thermal pressure, heat and humidity transfer with the building envelop of the whole air inlet network, than we can determine the selection of air handling equipment and the ventilator, and the scheme of air conditioning.This paper aims at the air inlet network of underground house in Baihetan hydropower station, analyses and completes the present calculation, amends the differences of air parameters because of the differences of elevation in multiple outdoor air intake, calculates and analyses the airflow distribution and the variation of each channel for different seasons and different parameters of air intake, gets the dynamic air parameters of each air intake in underground power house, provides the basis for the further matching of air handling equipment, and it comes up with the scheme of fan matching that can meet the demand of the ventilated area in different seasons that the demand of air volume is change.This paper puts forward a method of establishing the network graph of Baihetan hydropower station which regards the designed air volume in underground house as node flows to make sure the zone who needed fresh air getting its designed air volume. In the meantime, reducing the number of unknown number of branch flow in the calculation model equations. Then this paper corrects the temperature by considering the influence of practial elevation. Developing a numberical simulation procedure with Matlab language, this paper obtains the airflow distribution and thermal distribution of day-to-day and representative days in four seasons of the ventilation network and the temperature of each inlet air part of underground workshop.This paper analyzes the characteristic of the structure of underground hydropower station’s network, through which comes up with a new concept of "nodes with zero pressure" and poposes a method of matching all kinds of fan based on setting nodes with zero pressure. In combination with the practical situation of Baihetan hydropower station, analyzes its design of ventilation process to determine the zone which could be set as node with zero pressure. Then according to the airflow path, this paper put forward the performance parameters of the fan on the basis of the results about airflow and thermal value by calculating the ventilation network model and.Considering the changing demand of air volume in each area, this paper adopts more than one fan and uses the method of frequency control of motor speed method. To satisfy the need of airflow distibution in different seasons by changing the number of fans which are running and adjusting the motor speed of fan. |
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