In the large-bulb tubular flow turbine generator set, the turbine has the advantages of high specific speed, large unit flow, small cavitation coefficient and high efficiency. It is widely used in the development of low-head water resources. Market prospects. However, due to the limitation of low head and bulb ratio, the generator has small diameter and high electromagnetic load. Compared with the conventional hydro-generator, the heat-dissipation condition is quite bad. At the same time, the main size of the motor is relatively large, which makes the wind pressure of the whole motor. Larger, difficult to ventilate and cool. In order to solve the outstanding contradiction between the large heat loss caused by the high electromagnetic load of the bulb tubular turbine generator and the unfavorable cooling condition of the small and slender motor, this paper proposes a new mathematical model and a large bulb. The ventilation and heating problems of the hydro-generators were analyzed and calculated.
Wind path calculation model Large-bulb tubular hydro-generator adopts secondary circulation cooling method in cooling mode, that is, the loss of generator is transmitted to the cooling air through heat conduction and surface heat dissipation, and then the heat of the motor is charged by the conventional cooler. The cooling air is cooled, the heat of the motor is transferred to the cooling water of the cooler, and the cooling water that finally obtains heat transfers the heat of the motor to the river through the cooling jacket. In the hybrid ventilation system, the stator core has a radial ventilation groove, and the stator core is a non-adherent structure, and there is a ventilation passage between the stator core and the base, and the wind pressure component in the system is mainly a blower. The circulation path of the cooling air is shown in the figure, and the wind path model is shown in the figure. Due to the addition of air pressure components such as blowers in the mixed ventilation system of large-bulb tubular turbine generators, the wind pressure generated by each wind pressure component has a great influence on the ventilation cooling of the motor. This paper proposes a wind pressure containing The novel closed-loop iterative solution of the source complex wind path, the basic principle of the wind path calculation is as follows: According to the principle of air volume continuity, the algebraic sum of all the air flows flowing into any one node is equal to zero, that is, the wind pressure drop along each branch of any closed loop Algebraic sum is equal to zero of large motor technology. According to the above principle, when considering the wind pressure source in the wind path, the wind pressure component will change the distribution of each branch component and the magnitude of the wind pressure drop. It is proved that the mesh air volume is a heat path. Calculation Model This paper uses the equivalent thermal path method to calculate the temperature rise of a large bulb tubular turbine generator. The two-dimensional heat conduction process of the motor is simplified, and the two-dimensional heat flow in the thin plate is regarded as the result of the interaction of two one-dimensional heat flows subjected to the resistance in the research direction; the resistance of the synthetic heat flow in its own direction is regarded as two ones. The superposition of the resistance of the heat flow direction. In order to facilitate the calculation, it is assumed that there is no heat exchange between the stator and the rotor of the generator, and the heat sources inside the generator are evenly distributed, and the radial ventilation grooves are bounded, and the analysis is performed in stages. The stator equivalent heat path is taken as an example to illustrate the characteristics of the ventilation system: the stator core has radial ventilation grooves, so in the radial ventilation groove diagram, the bulb tubular flow turbine generator mixed ventilation system air circulation principle diagram diagram bulb flow Between the wind turbine model diagram of the hybrid turbine ventilation system, most of the core heat and coil winding heat will be carried away by the cooling air in the radial ventilation grooves on both sides of the core; the motor casing no longer has heat dissipation. The effect of the heat from the outer circumference of the core will be taken away by the cooling medium in the ventilation groove at the back of the core; the loss of the motor will be carried away by the cooling gas. According to the specific heat dissipation method of the hybrid ventilation motor, the equivalent thermal path model of each section of the generator stator is established, as shown in the figure.
Figure Bulb Tubular Turbine Generator Hybrid Ventilation Stator Equivalent Heat Path Diagram The physical meaning of the main symbols in the ventilation and temperature rise diagram of the large bulb tubular turbine generator is as follows: each heat source: expressed by loss, where is the stator Yoke loss; is the stator tooth loss; is the copper loss in each segment of the core; is the end loss or the winding loss in the ventilation groove.
Each temperature: the average temperature of the gas at the back of each segment; the average temperature of the gas in the yoke of each radial vent; the average temperature of the gas in the yoke of each radial vent; the average temperature of the air gap in each segment; The average temperature of the gas to the gully teeth; the average temperature of the gas in the teeth of each radial venting groove.
Each thermal resistance: the thermal resistance between the stator yoke and the back ventilation groove; the thermal resistance between the stator yoke and the radial ventilation groove; the heat transfer heat resistance between the yoke teeth is connected in series; the tooth portion and the air gap The thermal resistance between the stator teeth and the radial ventilation groove; the tangential insulation thermal resistance of the stator coil; the radial insulation of the stator coil and the thermal resistance of the wedge; the inner end of the stator slot coil and the ventilation groove The thermal resistance between the coils is formed by connecting the thermal resistance of the inner coil of the radial ventilation groove to the air.
Finite element temperature field calculation model This paper uses the finite element method to analyze and calculate the three-dimensional temperature field of the large-bulb tubular turbine generator. When the motor is in steady state operation, the internal three-dimensional heat conduction equation is: where: for temperature, the heat conduction in the direction is the heat source density. /01. If the boundary surface of the heating element consists of two parts, and the upper boundary conditions are: where: the temperature given is the temperature of the surrounding medium; the heat dissipation coefficient of the surface. /01. The conditional variational problem corresponding to the above mixed boundary value problem is that the discretization process can be used to solve the conditional variation problem of the above three-dimensional temperature field as a linear algebraic equation.
The calculation example of the Hongyan substation bulb tubular hydro-generator capacity is 8. The unit is subject to more restrictions on the ventilation and temperature rise of the motor due to the limitation of the bulb ratio and structural size, mainly reflected in how to distribute the air volume. Reasonable and uniform temperature distribution. To this end, based on the relevant design data provided by the manufacturer, the three kinds of mathematical models introduced above are used to comprehensively analyze and calculate the ventilation and temperature rise of the bulb tubular turbine generator of Hongyan Substation.
The rated voltage of the generator is the rated current is the rated power factor lag, and the closed circuit of the air cooler is forced to cool and the air is cooled. In the design, the stator core radial ventilation groove of the generator is considered to adopt two structural design schemes: equidistant segmentation and unequal pitch segmentation. The schematic diagrams are shown in the figure and figure respectively. In this paper, two different ventilation structures are calculated and compared, and the main calculation results are analyzed as follows.
The influence of the equidistant section and the unequal section on the ventilation of the stator core is calculated by the wind path. The results show that when the stator core is equidistantly distributed, the cooling air volume distribution of each section of the air gap is more uniform; After the segments are not equidistantly distributed, the distribution of cooling air in each section of the air gap is less distributed by the air gap in each section of the downstream end, and more is distributed in the air gap of each section of the upstream end. Since the downstream end of the bulb tubular turbine generator is the inlet end of the cooling air, the cooling air temperature is low, the cooling effect is good, and no more air volume is required; and the upstream end is the outlet end of the cooling air, the cooling air temperature is high, and the cooling is performed. The effect is poor, in order to ensure a certain heat dissipation effect, it requires more air volume. Therefore, the calculation results are consistent with the theoretical analysis. In fact, this uneven distribution improves the ventilation and cooling effect of the bulb tubular generator with a long core.
The stator core adopts the equidistant section and the unequal section to affect the heat generation. The equivalent heat path method is adopted, and the stator core radial ventilation groove adopts two structures of equidistant and unequal distance, in rated working condition and super The fever is compared and calculated under the working condition. The simulation results show that the stator core segments that are not equidistant are beneficial to the ventilation cooling of the generator. Under the same working conditions, the unequal stator core segment is used, and the temperature of each part of the stator and rotor is lower than that of the equidistant core segment. Therefore, after the main dimensions of the generator, the number of core segments and the loss are determined, it is preferable to adopt a stator core segment structure that is not equidistant. The figure shows the axial distribution curve of the temperature of the inner winding of the two different stator core structures. The table shows the calculation results of the rotor temperature.
Finite element analysis and calculation of three-dimensional temperature field According to the calculation result of equivalent heat path method, the stator motor winding inner motor technology diagram stator core radial ventilation groove equidistant distribution diagram stator core radial ventilation groove unequal distance distribution map Comparison of the temperature of the inner winding of the different stator core structure along the axial curve. Comparison of the rotor temperature calculation results of the project isometric equivalence core condition super-rising condition unequal distance core rated condition super-condition rotor winding temperature pole piece surface temperature damping strip The hottest section of temperature and temperature, using the finite element method to analyze and calculate the three-dimensional temperature field, further study the temperature distribution of each part of each section, using the unequal core structure, the three-dimensional mesh of the rotor is shown in the figure, as shown in the figure, the stator and rotor The maximum temperature calculation results are shown in the table.
The finite element method is used to calculate the maximum temperature of the stator rotor. The rated condition of the stator is over-condition. The maximum temperature of the stator winding. The maximum temperature of the stator core. The highest temperature of the rotor. The maximum temperature of the rotor and the maximum temperature of the rotor. The maximum temperature of the rotor damping bar. The problem of ventilation and heating of hydro-generators is difficult. In this paper, a complete set of analysis and calculation methods is proposed from the three directions of wind path, heat path and finite element three-dimensional temperature field, and the three-dimensional mesh section of rotor. The proposed mathematical model is verified by a numerical example. Through analysis and comparison, the simulation results are consistent with the theoretical analysis, which further indicates that the analysis and calculation methods have certain engineering practical value.
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