Restrictor-based studies of hybrid hole-entry conical journal bearings

Purpose This paper aims to describe how successfully a particular restrictor delivers its best in increasing the conical journal bearing performance. The restrictors are used in the hole-entry conical journal bearing subjected to hybrid mode. Thus, the restrictors, like constant flow valve (CFV), orifice and capillary, are studied comparatively. Design/methodology/approach Numerical simulation for the bearing results with the three restrictors are obtained by using finite element method (FEM) under the well-known modified Reynolds equation. Findings When the hole-entry conical journal bearings, with the restrictor design parameter range C¯s2 = 0.03 – 0.09, are operated, the results obtained are quite distinctive and significant. It indicates that the CFV restrictor-based conical bearing gives enhanced performance in comparison to orifice and capillary restrictors. Moreover, it suggests the performance-wise sequence of the restrictors in hybrid bearings as CFV > Orifice > Capillary. Originality/value The outcome of the research paper will give insight to help the bearing designer to choose the particular restrictor in hybrid conical bearing depending on the industrial need.

Method of calculating the total energy in suction and pressure pipelines of the main units at reclamation pumping stations

Purpose: theoretical substantiation of the method for calculating the total energy in suction and pressure pipelines of the main units at reclamation pumping stations to prevent unsteady processes and water hammer. Materials and methods: research and calculations were carried out at the pumping station “Mezhdurechye”, “Management of Stavropolmeliovodkhoz”, equipped with three main centrifugal pump units and two pressure pipelines. To calculate the total energy in the suction and pressure pipelines of the main pump, the entire pipeline network is divided into three sections: the first one is the intake, the second one is the distribution and the third one is the main pressure pipeline. For each section from 0.25 to 3.41 с²/м⁵ and the entire network 4.65 с²/м⁵, specific resistances were determined, the actual total head losses from 2.50 to 29.32 m when three units were fed into two pressure pipelines from 0.3 to 7.2 m³/s and hydraulic parameters of each unit: head (90.2 m), flow (2.67 m³/s), power (1585 kW), admissible vacuum suction head (4.2 m) at efficiency (88 %), with various operating options of the pumping station. Results: as a result of the research, the procedure for determining the total energy in the suction and pressure pipelines of the main units at reclamation pumping stations was determined, the total energy was calculated depending on the number of running pumping units: for suction pipelines from plus 0.1 to minus 1.5 m, for pressure pipelines from 75.79 to 86.34 m, which allows calculating the required hydraulic parameters of the booster pump used to close the back flow valve in the pressure pipelines of the main pump, to prevent backflow of water and water hammer before stopping the main pump. Conclusions: the above method is recommended for calculating in case of necessity the prevention of water hammer in the network by closing the back flow valve with a booster pump for reclamation stations equipped with centrifugal pumps with a maximum possible head of 120–130 m, in a complex operational option – the maximum number of pumps per one pipeline.

Analytical Study of Non-Recessed Conical Hole Entry Hybrid/Hydrostatic Journal Bearing with Constant Flow Valve Restrictor

The present work studies the analysis of a non recessed hole entry conical hybrid/hydrostatic journal bearing adjusted for constant flow valve (CFV) restriction. The paper provides effectiveness between the conical bearings with hole entry operating in hybrid and hydrostatic mode. The Reynolds formulae, for the flow of fluid through the mating surfaces of a conical journal and bearing, are numerically worked out in both the modes considering the finite element analysis (FEA) and the necessary boundary preconditions. Holes in double row are marked on conical bearing circumference to accommodate the CFV restrictors, the angular distance between two holes are 30o apart from the apex. Qualitative features of the conical journal bearing system with hole entry have been elaborated to analyze bearing performance for radial load variation Wr = 0.25-2. Numerical results obtained from the present study indicate that load carrying capacity of conical bearing, operating in hydrostatic mode, is enhanced by the maximum pressure, direct fluid film damping and direct film stiffness coefficients vis-a-vis corresponding hybrid mode.

Flow Control for a Two-Stage Proportional Valve with Hydraulic Position Feedback

The current research mainly focuses on the flow control for the two-stage proportional valve with hydraulic position feedback which is named as Valvistor valve. Essentially, the Valvistor valve is a proportional throttle valve and the flow fluctuates with the change of load pressure. The flow fluctuation severely restricts the application of the Valvistor valve. In this paper, a novel flow control method the Valvistor valve is provided to suppress the flow fluctuation and develop a high performance proportional flow valve. The mathematical model of this valve is established and linearized. Fuzzy proportional-integral-derivative (PID) controller is adopted in the closed-loop flow control system. The feedback is obtained by the flow inference with back-propagation neural network (BPNN) based on the spool displacement in the pilot stage and the pressure differential across the main orifice. The results show that inference with BPNN can obtain the flow data fast and accurately. With the flow control method, the flow can keep at the set point when the pressure differential across the main orifice changes. The flow control method is effective and the Valvistor valve changes from proportional throttle valve to proportional flow valve. For the developed proportional flow valve, the settling time of the flow is very short when the load pressure changes abruptly. The performances of hysteresis, linearity and bandwidth are in a high range. The linear mathematical model can be verified and the assumptions in the system modeling is reasonable.

Flow Analysis in a Steam Turbine Control Valve with Through-Flow Valve Chamber

The nuclear power plant also includes a secondary cycle, one of the main components of which is a steam turbine. This device processes the thermal and pressure energy of steam and converts it into mechanical energy. The heat from the reactor is conveied to the secondary cycle in the steam generator. Reliable and safe operation of the steam turbine, and thus of the entire block, is ensured by valves. Flow in a pair of control valves is considered, where the steam flows through the valve chamber past the first valve to the second valve. The experimentally determined flow characteristic of both valves is presented. Data of the distribution of pressures in selected places of these valves are presented. For the typical operating characteristics of a turbine, the course of the coefficient of total pressure distribution losses on the surface of the valves is evaluated. The pressure at the bottom of the cone is compared with the pressure on the wall of the diffuser throat. The energy loss in the valves is compared with the loss in a separate diffuser with varying degrees of expansion. There is also distinguished whether the flow is separated out of the diffuser walls or not.