A. E. Zaryankin

Pressure pulsations in the turbine steam-admission path and their influence on the vibration state of the turbine control valves

Data on pressure pulsations in the valve box, downstream of the diffuser seat, and in the subsequent steam line are presented for the case of using external valves, and it is shown that the level of pulsations depends essentially on the geometrical characteristics of the steam admission path.

Prospects of using two-tier low-pressure cylinders in steam-turbine power units

Possible ways for increasing the throughput capacity of the low-pressure cylinders of the condensing steam turbines are discussed. It is shown that the use of two-tier low-pressure cylinders allows the flowrate of steam through them to be increased by 65–70% without the need of increasing the length of last-stage blades.

Control valves and cascades for the first stages of turbines with ultrasupercritical steam parameters

This paper considers the problems that will unavoidably be encountered in the creation of new-generation turbines operated at ultrasupercritical initial steam parameters, namely, the development of new control and shutoff valves, the reduction of end energy losses in blade cascades and steam leaks in high-pressure cylinders (HPCs), the elimination of effect produced by regenerative steam bleedoffs on the afterextraction stage, the cooling of a blade cascade, etc. Some possible solutions are given for the two first of the listed problems. The conclusion about the need for the transition to new-generation control valves in the development of new advanced steam turbines with ultrasupercritical initial steam parameters has been made. From the viewpoint of their design, the considered new-generation valves differ from the known contemporary constructions by a shaped axially symmetric confusor channel and perforated zones on the streamlined spool surface and the inlet diffuser saddle part. The analysis of the vibration behavior of new-generation valves has demonstrated a decrease in the dynamic loads acting on their stems. To reduce the end energy losses in nozzle or blade cascades with small aspect ratios, it is proposed to use finned shrouds in the interblade channels. The cross section of fins has a triangular profile, and their height must be comparable with the thickness of the boundary layer in the outlet cross section of a cascade and, provisionally, be smaller than 8% of the cascade chord.

The effect the aperture angle of flat diffusers has on their vibration state and ways for reducing this vibration

We describe the results obtained from a comprehensive study of flat diffusers during which the level of pressure pulsations in their flow paths, the static and dynamic loads exerted on the diffuser walls, and the acoustic radiation levels were determined at different aperture angles of these walls.

Ways for reducing dynamic loads exerted on the walls of pipelines used in power installations

Methods for suppressing disturbances introduced into flow by valves are considered together with possible ways for reducing vibration of arbitrarily shaped pipelines and channels excited by pressure pulsations in moving medium.

A Throttle Control Valve for Steam Turbines Operating with Large Volumetric Flowrates of Working Fluids

A new design of a throttle control valve for steam turbines with throttle steam admission and large volumetric steam flowrates is considered. The difficulty associated with using these valves is that increasing the seat dimensions of spools entails a drastic decrease in the relative valve chest free volume for steam passage. This, in turn, results not only in higher hydraulic losses in the steam admission system but also in a higher nonuniformity of steam flow in the flow paths of such valves. Both these factors facilitate generation of very high pulsations of pressure in the valve’s entire flow path, which gives rise to high levels of acoustic emission and dynamic loads acting on all components of the valve, thus degrading its vibration reliability. Along with the proposed valve design, the article considers the design version of standard balanced control valves installed in large-capacity Russian steam turbines. It is shown that the passage of large volumetric steam flowrates through standard valves entails a significant reduction in the free valve chest volume for passing steam. This results in a growth of local steam velocities inside the chest and in a more pronounced negative influence of the chest shape on the valve flowrate and vibration performance. This situation can be improved by using one of the following two ways: to make the chamber with a significantly larger structural volume (which entails a larger cost of making the chamber) or to radically change the valve design. The article considers the second approach to solving the problem. In the proposed design version, the entire valve balancing system is shifted to the valve chest upper part, and the guide bonnet is made with large lateral ports ensuring free passage of steam to the diffuser seat. To achieve a more uniform circumferential field of velocities in the valve flow path, its cup is made with two perforation belts, the holes of which are connected to a common damping chamber, and the chamber itself is connected via a hollow cylinder with the axial force relief system.

The boundary layer separation from streamlined surfaces and new ways of its prevention in diffusers

This work provides a detailed analysis of all force conditions acting in the limits of the boundary layer on the moving fluid and gas media, and shows that a value of the transverse gradient of a shear stress δτ/δy, directly on the streamlined surface, is a main condition determining the possibility of attached flow along the streamlined surface in divergent zones. From an analysis of all the forces and their development in the converging flow, an effective way of prevention of the flow separation from streamlined surfaces of the cone-type, ring-type and axial-radial diffusers was developed that provides the flow stabilization in the wide-angle diffusers and multiple reduction of the dynamic load level acting on the walls of the mentioned devices. Results of the CFD-modeling and experimental investigations for flat asymmetric and wide-angle conical diffusers are presented in this paper.

Reduction methods of secondary flow losses in stator blades: numerical and experimental study

This paper examines the perspective design solutions for the secondary flows intensity reduction in the root and peripheral areas of the vane cascade. Increase of the aerodynamic efficiency is achieved by the special finning of internal shroud surface of the vane passage with curvilinear fins having a small height. A study was conducted to analyze the different types of finning on the basis of three-dimensional simulation (CFD). It considers variations with different number, height and shape of used curvilinear fins. In the process of optimization, the best case, which allows to reduce the secondary flow losses by 10-15 %, was obtained. Experimental studies of two vane cascade models were carried out on the aerodynamic test bench. First model was a vane base-type; second model was based on the optimal geometry obtained according to the results of three-dimensional simulation. Experimental studies make possible to confirm the proposed solution efficiency.

Superpowerful combined cycle power units with one gas turbine

This paper deals with different ways to increase the unit capacity of combined cycle power plants (CCPP) with an in-line equipment layout using a single gas turbine. The transition to a double flow gas turbine using a low-speed low pressure compressor connected with a low-speed steam turbine is a revolutionary way to solve the above problem. The double-shaft compressor is commonly designed with two additional internal bearings and is offered as a solution. The first stages of such a compressor (low pressure compressor (LPC)) connect with the steam turbine, but the second high-pressure group of stages (high-pressure compressor (HPC)) is driven by the gas turbine. So the gas turbine unites a start-up at the base of the HPC. The low pressure compressor and steam turbine can be designed with low revolution speed, which considerably increases air flow through the compressor and leads to an increase in the combined cycle power plant’s power capacity.

Thermodynamical aspects of the passage to hybrid nuclear power plants

This paper deals with a method of efficiency and power capacity for nuclear power plants, with the increase of pressurized water reactors at the expense of the passage to hybrid technologies. The essence of such a passage lies within two types of fuel applications and is realized by outer (in the case of a nuclear steam generating unit) steam superheater usage, which consumes fossil or hydrogen fuel.