Wet Steam Research Articles

Wave structure and flow amplitude-frequency characteristics in the turbine nozzle lattice in the presence of phase transition

This paper is devoted to the wave structure of a flow at its near- and supersonic velocities in a flat turbine cascade of profiles in the zone of phase transitions. The main task was investigation of the mechanics of interaction of the condensation jump with the adiabatic jumps of packing in a change of the initial condition of the flow. The obtained results are necessary for verification of the calculation models of the moisture-steam flow in the elements of lotic parts of the steam turbines. The experimental tests were made on a stand of the wet steam contour (WSC-2) in the Moscow Power Engineering Institute (MPEI, National Research University) at various initial states of steam in a wide range of Mach numbers. In the investigation of the wave structure, use was made of an instrument based on the Schlieren-method principle. The amplitude-frequency characteristics of the flow was found by measurement of static pressure pulsations by means of the piezo resistive sensors established on a bandage plate along the bevel cut of the cascade. It is shown that appearance of phase transitions in the bevel cut of the nozzle turbine cascade leads to a change in the wave structure of the flow. In case of condensation jump, the system of adiabatic jumps in the bevel cut of the cascade becomes nonstationary, and the amplitude-frequency characteristics of static pressure pulsations are restructured. In this, a change in the frequency pulsations of pressure and amplitude takes place. It is noted that, at near-sonic speeds of the flow and the state of saturation at the input, the low-frequency pulsations of static pressure appear that lead to periodic disappearance of the condensation jump and of the adiabatic jump. As a result, in this mode, the flow discharge variations take place.

Appearance and overall acceptability of fresh-cut cantaloupe pieces from whole melon treated with wet steam process

Minimally processed fresh-cut fruits have a limited shelf-life because of deterioration caused by spoilage microflora and changes in physiological processes. Whole melons was inoculated with 107 CFU/ml of Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes to achieve 4.8, 4.5 and 4.1 log CFU/cm2, respectively on melon surfaces. The inoculated melons were treated with a wet steam processing unit for 180 s before fresh-cut preparation. Microbial safety was studied and the overall appearance and acceptability of the fresh-cut pieces were investigated by trained panelists. There were no visual signs of physical damage on all treated cantaloupe surfaces immediately after treatments and during storage. All fresh-cut pieces from treated cantaloupes were negative for bacterial pathogens while aerobic mesophilic bacteria were recovered. Appearance and overall acceptability of fresh-cut pieces from treated melons during 6 days at 5 °C were not significantly (p < 0.05) different from control pieces prepared from fresh melons but were significantly (p < 0.05) different from untreated pieces from day 0 under the same storage conditions for 14 days. The results of this study suggests that wet steam treatment of cantaloupes rind surfaces designated for fresh-cut preparation will enhance the microbial safety of fresh-cut pieces, and the overall acceptability of cut pieces.

Unsteady Flow Field and Coarse Droplet Measurements in the Last Stage of a Low-Pressure Steam Turbine With Supersonic Airfoils Near the Blade Tip

The largest share of electricity production worldwide belongs to steam turbines. However, the increase of renewable energy production has led steam turbines to operate under part load conditions and increase in size. As a consequence, long rotor blades will generate a relative supersonic flow field at the inlet of the last rotor. This paper presents a unique experiment work that focuses at the top 30% of stator exit in the last stage of an low pressure (LP) steam turbine test facility with coarse droplets and high wetness mass fraction under different operating conditions. The measurements were performed with two novel fast response probes: a fast response probe for three-dimensional flow field wet steam measurements and an optical backscatter probe for coarse water droplet measurements ranging from 30 μm up to 110 μm in diameter. This study has shown that the attached bow shock at the rotor leading edge is the main source of interblade row interactions between the stator and rotor of the last stage. In addition, the measurements showed that coarse droplets are present in the entire stator pitch with larger droplets located at the vicinity of the stator's suction side. Unsteady droplet measurements showed that the coarse water droplets are modulated with the downstream rotor blade-passing period. This set of time-resolved data will be used for in-house computational fluid dynamics (CFD) code development and validation.

Optimum Tilt Angle of Flow Guide in Steam Turbine Exhaust Hood Considering the Effect of Last Stage Flow Field

Heat transfer and vacuum in condenser are influenced by the aerodynamic performance of steam turbine exhaust hood. The current research on exhaust hood is mainly focused on analyzing flow loss and optimal design of its structure without consideration of the wet steam condensing flow and the exhaust hood coupled with the front and rear parts. To better understand the aerodynamic performance influenced by the tilt angle of flow guide inside a diffuser, taking a 600 MW steam turbine as an example, a numerical simulator CFX is adopted to solve compressible three-dimensional (3D) Reynolds time-averaged N-S equations and standard k-e turbulence model. And the exhaust hood flow field influenced by different tilt angles of flow guide is investigated with consideration of the wet steam condensing flow and the exhaust hood coupled with the last stage blades and the condenser throat. The result shows that the total pressure loss coefficient and the static pressure recovery coefficient of exhaust hood change regularly and monotonously with the gradual increase of tilt angle of flow guide. When the tilt angle of flow guide is within the range of 30° to 40°, the static pressure recovery coefficient is in the range of 15.27% to 17.03% and the total pressure loss coefficient drops to approximately 51%, the aerodynamic performance of exhaust hood is significantly improved. And the effective enthalpy drop in steam turbine increases by 0.228% to 0.274%. It is feasible to obtain a reasonable title angle of flow guide by the method of coupling the last stage and the condenser throat to exhaust hood in combination of the wet steam model, which provides a practical guidance to flow guide transformation and optimal design in exhaust hood.

Mechanisms of Water Droplets Deposition on Turbine Blade Surfaces and Erosion Wear Effects

Failure of turbine blades leads to various exploitation problems, efficiency decrease and economical losses, at all. A detailed research on aerodynamic features, in various exploitation conditions and regimes, and on reasons for failures, is a prerequisite to the obviated technical problems and increased reliability of turbine aggregates. Water droplets erosion is known as a very complex and crucial phenomena. It couples the effects of wet steam expansion, together with condensation (evaporation), presence of second phase with the impact of water droplets over blade surfaces, erosion effects and fatigue mechanisms. The present research deals with a logical sequence for numerical simulations and research on erosion mechanisms in a low pressure stage of К-1000-6 /1500 steam turbine, working at a Nuclear Power Plant. Attention is paid to the impact of droplets’ diameter on blade surfaces, their aerodynamic behavior and efficiency of energy conversion through turbine channels. Particular trajectories of water droplets, reasons for occurrence of erosion wear, over certain parts of the streamlined surfaces, are established and discussed. An approach to acquire incidence time to erosion appearance is implemented. Research methodology and obtained results are applicable to determine erosion effects on streamed complex surfaces, to replace expensive measurements campaigns, introduce approaches to decrease wetness in last stages of condensation turbines and prolong the reliability of blades operated in wet steam conditions

Flow-Induced Acoustic Resonance in a Closed Side Branch Under a Low-Pressure Wet Steam Flow

Flow-Induced Acoustic Resonance in a Closed Side Branch Under a Low-Pressure Wet Steam Flow

Simultaneous measurements of fine and coarse droplets of wet steam in a 330 MW steam turbine by using imaging method

In order to fully comprehend the properties of fine and coarse droplets of wet steam flow in the steam turbine, the simultaneous imaging measurements method for fine and coarse droplets of wet steam was proposed based on RGB three wavelength bands light extinction and single frame single exposure principles. The innovative probe based on that method, which consisted of a telecentric lens and a color camera, was developed. The algorithm of RGB three wavelength bands light extinction was proposed for measuring the size distribution and wetness of fine droplets. And an imaging method based on single frame single exposure was used for the measurement of size, velocity, flow direction, and amount concentration of coarse water. The probe was applied to measure the wet steam in downstream of the last stage of a 330 MW steam turbine. The measured size and wetness of the fine droplets are in the range of 0.7–0.9 µm and between 6% and 9%, respectively. The maximum velocity and diameter of the coarse water droplet could reach 225.7 m/s and about 200 µm, respectively. Furthermore, several kinds of special forms coarse droplets images were obtained. And the characteristic and forming reasons of these coarse droplets were preliminarily discussed for the further experimental study.

Numerical analysis of the oscillation frequency of the shock wave and the evaporation level on the Mach disc in the IMP PAN nozzle

In the present paper, we have focused on the phenomena occurring in the supersonic part of the de Laval nozzle, characterised by oscillation of the shock wave in steam flow. The effect of shock oscillation was observed by using the Topler optical system in the IMP PAN experiment carried out on a symmetrical planar de Laval nozzle. Having observed the shock fluctuation in wet steam flow, according to Puzyrewski's observations, we analysed the oscillation frequency in the IMP PAN nozzle depending on the pressure conditions. Additionally, we analysed the evaporation level of condensate droplets during passage through the Mach disc depending on the inlet conditions. The model of a single continuum wet steam model with a special microstructure growing up during phase transitions was validated on an experiment carried out by Dykas et al. in 2013 on the half arc nozzle. The present work includes simulations results of oscillation frequency of the shock wave and the evaporation level of the liquid phase on the Mach disc.

Control of the probe influence on the flow field in LP steam turbine

For measuring the fine droplets properties in the wet steam expanding in the steam turbines the light extinction probes are usually used. The paper presents CFD modelling of the extinction probe influence on the wet steam flow field at the measurement position. The aim is to get a basic information about the influence of the flow field deviation on the measured data, in other words, of necessity to correct the measured data. The basic modelling procedure is described, as well as the supposed simplifications and the factor considering the change in the steam density in the measuring slot of the probe. The model is based on the experimental data that were achieved during the developmental measurements in the steam turbine 1090 MW in the power station Temelin. The experimental measurement was done in the cooperation with the Doosan Skoda Power s.r.o.

Numerical investigation of condensing flow of low pressure steam turbine at different flow rate conditions

The numerical investigation on the wet steam flow in the last two stages of a 1000 MW fossil-fired low pressure steam turbine is presented in this paper. The non-equilibrium model via the classical nucleation theory is employed to simulate the condensing flow of the wet steam. The characteristics of the flow filed from design condition to low volume flow condition are calculated and the static performance of last stage moving blade is also obtained. The development of the backflow phenomenon is clearly captured through the analysis of the velocity triangle.

超音波流量計を用いた蒸気流量計測における蒸気湿り度の影響

In industrial fields, as the steam is commonly utilized for heat supply, drying process and so on, it is important to be aware of the steam flow rate in the view point of energy management. However, the steam utilized in the factory is usually wet steam condition. Though it is well known that the wetness affects the flowmeter reading, it is difficult to clarify the effects of the wetness in the steam flow quantitatively in actual plants and factories, and thus far, there has been no established method for estimating the error caused by the wetness of steam flow. In this paper, the difference of ultrasonic flowmeter reading due to wetness of the wet steam flow was clarified experimentally. Ultrasonic flowmeter reading in the wet steam flow was compared with Coriolis flow meter installed after heat exchanger in the steam apparatus. As a result, we clarified the flow rate difference of those two flowmeters was increased with increasing wetness, and the ultrasonic flowmeter reading was almost the same as the value of steam phase flow rate in the wet steam flow. We also proposed the correction method of the ultrasonic flowmeter reading by using density correction in the flow rate formula of the ultrasonic flowmeter. And finally, we clarified the uncertainty of the measured flowrates and their differences were less than 1.0%.

Wet Expansion Steam Cycles for Offshore Industry

Wet Expansion Steam Cycles for Offshore Industry

クランプオン型超音波流量計による湿り蒸気流量の計測

クランプオン型超音波流量計による湿り蒸気流量の計測

A REVIEW ON - SOLAR CONCENTRATORS, PERFORMANCE OF SOLAR COLLECTORS & ENERGY STORAGE

Parabolic trough concentrators are one type of concentrators which reflects the sunlight on the receiver (Line type) and gives us wet steam for water. It can be tried with any type of fluid. Presently solar collectors are used for residential and commercial use. These solar collectors require high maintenance and high installation cost, solar concentrators help us in these disadvantages. This review paper concentrates on solar concentrators and various fluids that can be used in receiver. It also focuses on surface shape measurement of solar concentrator in solar thermal power application. In order to capture maximum amount of solar energy it is required to orient the concentrator as per the position of the sun i.e. tracking is required .However some of the concentrators do not track and are referred as fixed concentrators. The objective of the project is to track the receiver instead of solar concentrator.

Experimental Investigation for Influence of Static Pressure on Pressure Fluctuation of Acoustic Resonance under Wet Steam Flow

Experimental Investigation for Influence of Static Pressure on Pressure Fluctuation of Acoustic Resonance under Wet Steam Flow

An Improved Steam Injection Model with the Consideration of Steam Override

The great difference in density between steam and liquid during wet steam injection always results in steam override, that is, steam gathers on the top of the pay zone. In this article, the equation for steam override coefficient was firstly established based on van Lookeren’s steam override theory and then radius of steam zone and hot fluid zone were derived according to a more realistic temperature distribution and an energy balance in the pay zone. On this basis, the equation for the reservoir heat efficiency with the consideration of steam override was developed. Next, predicted results of the new model were compared with these of another analytical model and CMG STARS (a mature commercial reservoir numerical simulator) to verify the accuracy of the new mathematical model. Finally, based on the validated model, we analyzed the effects of injection rate, steam quality and reservoir thickness on the reservoir heat efficiency. The results show that the new model can be simplified to the classic model (Marx-Langenheim model) under the condition of the steam override being not taken into account, which means the Marx-Langenheim model is corresponding to a special case of this new model. The new model is much closer to the actual situation compared to the Marx-Langenheim model because of considering steam override. Moreover, with the help of the new model, it is found that the reservoir heat efficiency is not much affected by injection rate and steam quality but significantly influenced by reservoir thickness, and to ensure that the reservoir can be heated effectively, the reservoir thickness should not be too small.

A Unified CFD Based Approach to a Variety of Condensation Processes in a Viscous Turbulent Wet Steam Flow

A family of quasi linear mathematical models is presented and calculations made for viscous turbulent wet steam flow with a variety of condensation phenomena. These models can be applied to the analysis of equilibrium condensation, homogeneous (spontaneous) condensation, heterogeneous condensation on extraneous particles, and condensation of charged dispersed phase moving in an electrostatic field. The unified model is represented by coupled systems of gas dynamic equations for viscous turbulent two-phase flow, kinetic and electro-kinetic equations tracing out combined processes of size and charge growth, and electromagnetic field equations described an electric field with an account of self-induced in-part by a moving electrical cluster. The numerical procedure is time marching, monotone, implicit, of second order accuracy by space and time coordinates, and exhibits high resolution shock capturing ability. Viscous flow field calculations made with this procedure reveal significant influence on condensation by the shear boundary layers and wakes. Distributions of cooling rate, droplet radius and parameters of the bulk flow are predicted. Verification of the codes against known experimental data is presented.

Numerical simulation of gas flow and droplet motion in a wave-plate eliminator of the separator-steam-generator system in the waste-heat-utilisation complex

This paper studied the droplet transport and deposition in the turbulent flow inside a wave-plate eliminator of the waste-heat utilisation complex (WHUC). The Lagrangian discrete particle approach was used to simulate the process of liquid separation from wet steam flow. Two different models for droplet-eddy interaction were tested using data from the available literature. The tested numerical model was used to predict the WHUC performance.

Моделирование кинематики и сепарации полидисперсных капельных потоков в вертикальных циклонах с боковым подводом влажного пара или воздуха

Моделирование кинематики и сепарации полидисперсных капельных потоков в вертикальных циклонах с боковым подводом влажного пара или воздуха

Parametric Analysis of Steam Flashing in a Power Plant Using Waste Heat of Cement Factory

Abstract Currently India is producing 350 million tons of cement and so there is a more potential to generate the power through waste heat recovery. A case study has been conducted at a cement factory, Telangana, India with cogeneration plant having flashing technology. The high pressure water is flashed into wet steam at two pressure levels (high pressure flashing and low pressure flashing) to increase the power generation. The hot water from the flashing chamber is used for the regeneration of the cycle and the steam is supplied to the turbine at the relevant location. In the current work, the optimum values for the high pressure flashing and the lower pressure flashing are searched and developed for the maximum heat recovery and also higher output from cogeneration plant. The identified key operational parameters are steam generating pressure, limit to high pressure flashing, limit to low pressure flashing and flash mass ratio.