Transient Flow Analysis And Experimental Study On The Braking System Of Hydraulic Turbine

On the basis of comprehensive summarize and analysis of the braking scheme of separator, this paper brought forward a new hydraulic braking method in which a hydraulic turbine was used to recover the energy of the drum during the shutdown process, and designed a set of hydraulic braking system used in LX660latex separator. In view of the designed hydraulic braking system, an analysis model was established to study the transient process theory, and it was pointed out that the hydraulic turbine played the key role during the shutdown process of the hydraulic braking system. The attenuation law of the system’s flow rate and the turbine’s speed during the shutdown process were obtained, and a parameter-the energy ratio was proposed, which could effectively guide the design of hydraulic braking system. Taking the hydraulic system with the core-centrifugal pump as the object of experiment study, the proposed theoretical analysis model was verified, and the results of this paper is of the application value for the development of the new separator hydraulic braking system.The main work of this paper is as the following:(1) This paper summarized the present state of research and the principle of the separator braking method, brought out a new hydraulic braking method for the shutdown process of high speed and large inertia rotor, and designed a set of hydraulic braking system used in LX-660latex separator.(2) According to the structure of the hydraulic braking system, an analysis model of the hydraulic braking system was established, and then focused on the shutdown process of the hydraulic turbine, the transient process was analyzed based on the theoretical model. The general law of the system’s flow rate attenuation and the turbine’s speed attenuation during the shutdown process of flow system were obtained, and for the special system with the rotor of large inertia, it was pointed out that the shutdown process of the large inertia system was mainly determined by the characteristic of the hydraulic turbine.(3) In order to study the influence of the hydraulic turbine characteristic on the shutdown process, taking the hydraulic system as the experiment analysis model, the experiment study of the shutdown characteristic has been done. The results of the experiment show that with the decrease of the speed and the flow rate, the gradient of the speed and the flow rate becomes smaller, and the shutdown process becomes slower. Compared with the speed attenuation, the flow rate attenuation of the shutdown process has a lag, and the lag time increases when the initial speed of the turbine reduces. The attenuation speed of the turbine speed and the system flow rate has nothing to do with the shutdown initial speed, and is related with the load inertia of the rotor. With the load inertia increasing, the speed and the flow rate attenuation becomes slower.(4) The analytical model of the hydraulic braking system was verified with the results of the experiment study of the hydraulic system. The results of the theoretical calculation and the experiment were dimensionless, and then compared.(5) The theoretical analysis results show that the shutdown effect of the large inertia system is mainly decided by the hydraulic turbine characteristic. In order to study the characteristic of the turbine intensively and analyze the influence of the turbine characteristic on the shutdown process, the CFD model of the turbine of the hydraulic braking system was established, and the SST k-co turbulence model was used to simulate the process. The different operating points of braking process were selected and simulated respectively by quasi steady and transient calculation method, and then the calculation results was contrasted.