Steam Flow Research Articles

Study on flow characteristics of leakage in the last stage inner blade tip clearance of steam turbine

Internal steam leakage in steam turbines from the high-pressure side to the low-pressure side through clearances causes loss, resulting in reduced efficiency and potentially compromising the safe operation of the turbine. Therefore, a comprehensive understanding of the flow characteristics of leakage through blade tip clearances is crucial to improve the efficiency of steam turbines. In this paper, the last stage blades of the low-pressure cylinder of a certain 600 MW ultra-supercritical steam turbine unit were studied. A wet steam flow model and a turbulence model were established, and the flow characteristics of the last stage under different inlet parameters, outlet parameters, and tip clearance sizes were analyzed. The results showed that an increase in the clearance size affects the inlet and outlet steam angles of the rotor blades, with significant changes occurring near the blade tip. The main flow velocity inside the rotor blade channel fluctuates violently starting from the 70% axial position. The high entropy region is located near the exit flow region of the rotor blade, with its range expanding as the clearance size increases. The entropy change is significant at 60% blade height and above, with more intense changes occurring in the blade tip area. The relative leakage amount and efficiency change uniformly with clearance variation. Generally, for every 0.1% increase in clearance height, the relative leakage amount increases by ∼0.31%–0.42%, and the stage efficiency decreases by 0.34%–0.44%. The results of this study can provide a theoretical basis and guidance for improving the flow efficiency of steam turbines.

Research on dehumidification optimization of steam turbine wet steam stage hollow stator cascade heating

The secondary water droplets in the steam turbine wet steam stage are easy to cause water erosion damage to the rotor cascade, and there is a large speed slip between the main steam flow and the secondary water droplets, which will seriously affect the safe and stable operation and reduce the efficiency of the steam turbine. Secondary water droplets are formed when the water film deposited on the stator blade surface falls off at the trailing edge. Therefore, controlling the formation of a water film on the stator blade surface plays an important role in improving the efficiency and safety of the steam turbine wet steam stage. Based on the current research situation at home and abroad, taking the Dykas cascade as the research object, it is found that the covering area of dry steam film on blade surface expands with the increase of temperature and flow of hot steam inlet. With the increase of hot steam back-pressure, the wetness of blade surface increases. When the average heat flux on the blade surface reaches 5000W/m2, there will be no water film falling off the blade surface. By orthogonal test, the expression between the average heat flux on the blade surface, the inlet temperature, the flow rate and the back-pressure was obtained. The research results can provide reference for the parameter design of steam turbine hollow stator heating dehumidification.

Mathematical procedure for predicting tube metal temperature in the radiant superheaters of a tangentially and front fired utility boilers

The superheaters can be indicated as one of the most critical components of the utility boilers experiencing highest temperatures. The local overheating of the heat exchangers material is a significant operational issue. The current and future market conditions implicate new unfavourable regimes of boiler operating conditions bringing the need for prediction capability of tube wall temperature in either design or retrofit process. There is a need to obtain a realistic metal temperature distribution based on uneven heat flux absorbed and complex steam flow. The current paper demonstrates a computational methodology of predicting tube metal temperature of radiant superheaters platens. It couples a full scale 3-D boiler simulations based on CFD technique on the combustion side with an in-house 1-D heated pipe flow model of the steam side. The methodology was applied to two different boilers with different firing strategy (front fired and tangentially fired) to demonstrate the model flexibility. The model is capable of identifying the exact location of specific platen in which the metal maximum temperature occurs. A validation study was conducted by utilising the available measurements. The computations are in qualitative and quantitative agreement with measurement. The modelling approach can be easily extended to boilers utilising all types of fuels as well as heat recovery steam generators.

Process simulation of cassava cellulosic ethanol production with low to medium-pressure steam heat integration

Energy demand tends to increase by 80% in 2050 due to the rapid growth of the global population. However, the energy resources rapidly decrease for responding to the global need. Many previous researchers suggest the ideas for solving this situation and the most interesting solution is the heat integration which intends to produce cost-effective energy with minimal impact on the environment. Energy integration thus should be noticeable for the industry process to minimize the loss along the industrial process. The ethanol production process is interested in this study because it can add value to agricultural products like cassava which is an industrial crop in several countries and produces ethanol products that can decrease the usage of gasoline. Here, the heat integration model was developed for the ethanol production process by using low to medium-pressure steam. For the simulation model, the ethanol production process used the cellulose content as the main inlet component to be easy for applicable corresponding to feed casava cellulosic substances. The process contained three sections including enzymatic hydrolysis, simultaneous saccharification fermentation (SSF), and fractional distillation. The quality and quantity of low to medium-pressure steam were investigated for maintaining the operation of the enzymatic hydrolysis reactor by varying steam pressure between 1–2 atm and steam temperature between 100–105 °C. The results achieved the methodology to find optimum conditions by the ratio between steam flow rate and product quantity. The best case could reduce 6.49% of the excessive usage of low to medium-pressure steam which pointed out the way to use the energy efficiently.

On the issue of creating the optimal last stage of powerful steam turbines of nuclear power plants

THE PURPOSE. To estimate the most effective length of the working blade of the last stage of a powerful wet-steam turbine in terms of obtaining its maximum efficiency and to optimize the parameters of this stage in the design mode. For this stage, perform multi-mode optimization to select the main characteristics of the stage operating with maximum efficiency according to a given model daily load schedule.METHODS. When solving this problem, the method of calculating the axisymmetric flow of steam in the flow part of the turbine stage as an inviscid single-phase working fluid relative to a stationary guide device and rotating with an angular velocity ω of the impeller used, and the losses energy calculated according to the axisymmetric method of the MPEI.RESULTS. The article describes the relevance of the topic, discusses the features of the use of the author's software in solving the tasks. The characteristics of the stages with different lengths of the working blades presented and the results of their calculation in the nominal mode are given. A model daily schedule selected for a nuclear power plant turbine operating in the central region of Russia. The results of calculations of variable modes of the last stage of the turbine operating according to this daily schedule presented.CONCLUSION. The choice of the maximum length of the working blade is limited not only by its strength characteristics, but also by the increase in wave losses in the gratings due to an increase in the optimal available heat drop, or rather the associated increase in supersonic speeds near the meridional contours. So for a high-speed turbine To-1200-6,8/50 the maximum efficiency of the last stage is achieved at a length of 1400 mm, both when the turbine is configured with both three two-flow LPC and four. Selection of the main characteristics of these stages, such as the available heat drop, the degree of reactivity, etc. it should be made taking into account the variable operating modes of the turbine on the basis of the forecast of daily schedules of loads of turbine units. When using a typical daily load schedule, the average internal relative efficiency in the range of operating modes according to this schedule is higher by 0.6 % when choosing a 10% increased available heat drop compared to the optimal one in the design mode.

Simulation and optimization of a conical type swirl-vane separator in nuclear SG

Swirl-vane separator is used as primary separator in nuclear SG for liquid droplet separation from steam flow. In order to improve the separator performance, in present paper, based on the commercial CFD software STARCCM+ and Euler-Euler two-fluid model, three-dimensional simulation and optimization of a conical swirl-vane separator are performed to study the flow filed and separation performance of this new designed separator. According to the results, a low-pressure and low-velocity wake region is formed at the swirler outlet and its shape narrows first and then enlarges along the flow direction due to the reduced flow channel of the conical barrel. The steam axial velocity exhibits a “M” type distribution while the tangential velocity displays a “V” type distribution in the radial direction. The steam radial velocity is about an order lower than the other two velocity components. The static pressure decreases sharply in the swirler, demiser and diffuser part, which is the main energy loss in the separator. On the whole, the structure of conical barrel and drain holes are very important for liquid separation. Within a certain range, a smaller hole diameter, a larger axial location of drain holes and a smaller conical angle can improve the separation efficiency of the swirl vanes, but also increases the pressure loss of the conical barrel section.

Investigation on the Aerodynamic Performance of High-Pressure Cylinders under the Mode of Regulating Steam Supply with an Intermedium-Pressure Adjustment Valve

In order to investigate the operational performance of the high-pressure (HP) cylinder towards a 300 MW boiler unit, the three-dimensional calculation method was applied to simulate the aerodynamic flow characteristics of the last five stage cylinder blades, including limiting streamline, isentropic efficiency along the blade height, and relative work amounts. Simulation results show that with the back pressure controlled at 3.4 MPa and the inlet steam flow decreasing to a certain extent, the flow state of the last three stage blades begins to deteriorate. When the back pressure continues to drop, the flow state becomes unstable at the blade root and the blade tip on the suction surface of the rotor blade, while the flow state is stable on the pressure surface of the rotor blade and the surface of the stationary blade. If the flow rate decreases, the flow separation area on the suction surface of the moving blade decreases, and the flow performance can be improved. With the decrease in the boiler load, the total-total isentropic efficiency for the last three stage blades of the HP cylinder gradually decreases. In addition, the isentropic efficiency at the blade root and blade tip is lower than that for the blade body, which is closely related to the flow separation phenomenon of the last three stages of moving blades at the root and tip. In the working condition of the intermedium-pressure adjustment valve, since the temperature variation is within a limited range, operational safety can be guaranteed under the design blade frequency and strength. This paper provides the upper and lower limits of the exhaust gas pressure for the HP cylinder under the intermedium-pressure adjustment valve participation mode concerning various working conditions as well as corresponding constraints. This is conducive to guiding the design and safe operation of the intermedium-pressure adjustment valve. Through adjusting the intermedium-pressure adjustment valve, a specific supply capacity of the unit can also be satisfied at the lower load, which is beneficial to the deep peak regulation of the unit.

An Optimization Method of Steam Turbine Load Resilient Adjustment by Characterizing Dynamic Changes in Superheated Steam Energy

Improving the dynamic regulation ability of thermal power units is effective for realizing flexible scheduling in modern power systems. At present, the unit regulation capacity is usually reflected by the load adjustment of the main steam pressure and flow tracking ability, through the calculation of the given and real-time deviation to complete the load, and by pressure adjustment. However, although the calculation involved in this method is easy and the results are intuitive, overshoot and lag can easily occur. The main reason for this is that the process from boiler combustion to turbine works has strong hysteresis and inertia, and the feedback signal of the pressure and flow rate cannot dynamically reflect the change in boiler combustion and steam energy. According to the heat transfer process of the unit, the main steam temperature can directly reflect the energy transfer in the furnace combustion process and then reflect the changing trend of steam energy. Analyzing the changing characteristics of the temperature, pressure, and flow of superheated steam under rapid load regulations makes it possible to calculate the instantaneous energy storage value of the main steam before the regulating valve, and this value was inserted into the coordinate system as a new feedforward signal. Finally, a simulation model was established by using the actual running data of the unit. A simulation experiment under variable working conditions demonstrated that this method could improve the dynamic adjustment of the unit to load and pressure and help the power grid absorb renewable energy.

Lessons learned from hydrothermal to hot dry rock exploration and production

In this paper, we investigate geothermal exploration and production in 189 hydrothermal projects and 42 hot dry rock projects around the world. The hydrothermal fields for a working hydrothermal system to generate electricity should have the elements of heat source, water-saturated porous or fractured reservoir, caprock, heat transfer pathway, and good heat preservation condition and geothermal power energy intensity of 10–20 MW per km2 within at least 5 km2 area in tectonically active region. The hot water or steam flow rate in this hydrothermal system is normally larger than 40 L/s with temperature of 150 °C or above. The power generated from enhanced geothermal system (EGS) in hot dry rock projects are generally less than 2 MW because the flow rate in most cases is much less than 40 L/s even with the hydraulic fractures using the modern stimulation technology learned from the oil and gas industry. The natural fracture in the subsurface is generally beneficial to the hydraulic fracturing and heat recovery in the hot dry rock. Moreover, the hydraulic fracture parameters, injection rate and well spacing, drilling strategy should be properly designed to avoid the short-circuit between injector and producer and low heat productivity. In the future, CO2 enhanced geothermal recovery associated with CO2 sequestration in the high temperature oil, gas, and geothermal fields maybe a good choice. On the other hand, both near-real-time seismic monitoring to limit the pumping rate and the closed-loop of the Eavor-Loop style system without hydraulic fracture can contribute greatly to heat recovery of hot dry rocks and mitigate the risks of the hydraulic fracturing induced earthquake. Furthermore, the hybrid solar and geothermal system performs better than the stand-alone geothermal system.

Subduction and Hydrogen Release: The Case of Bolivian Altiplano

Natural hydrogen is known to be generated in the crust by water/rock interactions, especially the oxidation of iron-rich rock or radiolysis. However, other sources, especially deeper ones, exist. In the context of subduction, the dehydration of the slab, the destabilization of the NH4, and the hydration of the mantle wedge above the subducting lithosphere may generate H2. We present here a compilation of the known gases in the central part of the Pacific subduction and the results of a first field acquisition dedicated to H2 measurements in Bolivia between La Paz and South Lipez. Various zones have been studied: the emerging thrust faults of the western borders of the Eastern Cordillera, the Sajama area that corresponds to the western volcanic zone near the Chile border northward from the Uyuni Salar, and finally, the Altiplano-Puna Volcanic Complex in South Lipez. Soil gas measurement within and around the Salar itself was not fully conclusive. North of the Uyuni Salar, the gases are very rich in CO2, enriched in N2 and poor in H2. On the opposite, southward, all the samples contain some H2; the major gas is nitrogen, which may overpass 90% after air correction, and the CO2 content is very limited. On the western border of the Cordillera, the δC13 isotope varies between −5 and −13‰, and it is not surprisingly compatible with volcanic gas, as well as with asthenospheric CO2. The methane content is close to 0, and only a few points reach 1%. The isotopes (−1‰) indicate an abiotic origin, and it is thus related to deep H2 presence. The high steam flow in the geothermal area of South Lipez combined with the H2 content in the water results in at least 1 ton of H2 currently released per day from each well and may deserve an evaluation of its economic value. The nitrogen content, as in other subduction or paleo-subduction areas, questions the slab alteration.

Refrigerant overheating in the compression circuit air heat pump

The authors considered the processes of phase transformation of the working fluid in the compression unit of the freon circuit in the section “thermal expansion valve (TEV) - evaporator - compressor”. By adjusting the expansion valve under the conditions of the bubble mode of boiling of the refrigerant, the evaporation process takes place, accompanied by the achievement of a certain excess of steam temperature. Determination of rheological parameters (droplet size, vapor viscosity, refrigerant droplet vaporization rate) is necessary so that when moving from the throttle valve (TEV) to the compressor inlet, they have time to go into the vapor phase or return to the mass of boiling liquid. The article presents the results of an analytical calculation of the parameters of the kinetics of evaporation of Freon droplets as they move in a steam flow. The results of such an analysis make it possible to formulate requirements for the optimal droplet size in the created vapor-liquid mixture in order to ensure their maximum evaporation and the required thermal efficiency of the AHP as a whole. The established patterns of evaporation of refrigerant droplets can be used to select the design and operation of the AHP.

Separation near the bushing of the flow in the outlet nozzle of the steam turbine at the low-flow rate modes

The paper considers the movement of steam flow from the working wheel of the last stage with a large fanning to the outlet nozzle of a steam turbine, considering the conditions for the formation of the separation near the bushing in a wide range of mode changes. An assessment was made of the initiation and development of the separation near the bushing in the space of the outlet nozzle of the steam turbine. To analyze the formation of the movement of the working medium in the free space of the outlet nozzle, an axisymmetric flow model is used, which is described by the equation of the hyperboloid of rotation.

Study on the Influence of the Tube Bundle Arrangement on the Performance of Condenser in Nuclear Power Plant

Nuclear power generation technology is obviously a safe and economical way of generating power in modern society. As the low temperature heat source, the condenser of the nuclear power technology condenses the steam into condensate water and then establishes a certain degree of vacuum at the exhaust port of the turbine. The operation of condenser is critical to the nuclear power generation technology. In this paper, the influences of the arrangement of tube bundles on the condenser of nuclear power generation technology were investigated. Three types of condensers, including the church window type, the centripetal type, and the UT type, were analyzed using Ansys Fluent software. The steam flow velocity distribution, air concentration distribution, temperature distribution, and heat transfer coefficient distribution were studied. Under specific design conditions, the flow velocity in the church window type was large, the exhaust air concentration was small, the maximum flow rate distribution was relatively reasonable, and the air concentration distribution was more concentrated. The performances of the centripetal type and the UT type were slightly worse, and the steam condensation was less. In contrast, the condensation of the church window type was large, the relative performance was high, and the heat transfer performance was better.

Modeling condensing flows of humid air in transonic nozzles

The ability to accurately model condensing flows is crucial for understanding such flows in many applications. Condensing flows of pure steam have been studied extensively in the past, and several droplet growth models have been derived. The rationale for the choice of growth models for condensation in humid air is less established. Furthermore, only a few validation cases for condensation in such flows exist. This paper aims to identify existing limitations of common droplet growth laws. The Hertz—Knudsen model is compared to heat-transfer-based models by Gyarmathy and Young, using an Euler—Lagrange approach in Ansys Fluent. For this, an adaption for Young’s growth law is introduced, allowing its application in condensation of different gas mixtures. The numerical model has been validated and applied to flows in nozzles and turbines in previous publications. The accuracy of the droplet growth models is investigated in transonic nozzle test cases. A case with pure steam and a case with humid air at two different humidity values are considered. Finally, the influence of humidity, Knudsen number, and droplet radius on the growth rate of each model is shown analytically. Flows at lower humidity values with longer condensation zones are shown to benefit from the higher sensitivity of the Hertz—Knudsen model to the mass fraction of water vapor in the flow. Heat-transfer-based models tend to overestimate condensation in such flows. However, the ability to empirically adapt the growth model by Young and its applicability in different Knudsen numbers results in good agreement with validation data over a wide range of cases.

Experimental Analysis of Steam Generator Tube Rupture in CIRCE Facility for MYRRHA Configuration

One of the main safety issues of Generation IV (Gen IV) heavy liquid-metal fast reactors is the postulated steam generator tube rupture (SGTR) accident. This event is characterized by primary and secondary coolant interaction, referred to in the literature as a coolant-coolant interaction event having a nonzero probability to occur. This accident scenario could affect the safety of a pool-type reactor, as a consequence of water secondary coolant flashing into the primary coolant liquid metal. The SGTR event needs to be experimentally characterized to evaluate the pressure waves effect, tube rupture propagation (domino effect), oxide precipitation and slug and plug formation, cover gas pressurization of the reactor, and steam flow paths through the pool and eventually the core, entailing the risk of positive reactivity insertion (due to positive local void coefficient). The design phase of the Gen IV MYRRHA plant has dealt with postulated SGTR safety issues in the framework of the MAXSIMA project, which is supported by the European Commission. A relevant contribution to this research activity was provided by the Italian Agency for New Technologies, Energy and Sustainable Economic Development Research Center Brasimone, where a new test section has been designed, assembled, instrumented, and implemented in the large-scale integral-effects pool facility CIRCE for investigating the SGTR event in a relevant configuration for the heat removal system of MYRRHA. This research reactor is not oriented to steam production for running a turbogenerator (no electric production), thus the heat removal system is referred to as the primary heat exchanger (PHX) and not as a steam generator. Four full-scale portions (four bundles of 31 tubes) of the MYRRHA PHX were adopted to carry out four independent SGTR experiments. Water flowed upward in the central tube of the bundle and two rupture positions were investigated at the lower and upper levels, named the bottom and middle scenarios, respectively. After the rupture, water was injected at 16 bar and 200°C into lead bismuth eutectic alloy at 350°C. The experimental results showed a remarkable repeatability and were presented in terms of (1) CIRCE vessel pressurization up to 2.7 and 4 bar absolute for the middle and bottom scenarios, respectively; (2) vapor flow paths through the bundle and its cooling effect up to 120°C and 140°C for the middle and bottom tests, respectively; and (3) strain measurements on tubes and bundle shells up to 2800 μm/m. The integrity of the tubes surrounding the ruptured one and the effectiveness of implemented safety device (rupture disks) pressure relief were significant engineering feedback for MYRRHA designers. The acquired high-quality data also constitute a database increase for future code verification and validation and possible new model development. The performed experimental analysis provided the awareness that a suitable design of a depressurization system (e.g., rupture disks) could allow for addressing postulated SGTR events in the MYRRHA configuration with confidence and safety.

Analysis of Desalination Performance with a Thermal Vapor Compression System

Multi-effect distillation with thermal vapor compression (MED-TVC) is a highly energy-efficient desalination technology that can provide a reliable and sustainable source of high-quality water, particularly in areas with limited energy infrastructure and water resources. In this study, a numerical model based on exergoeconomic approach is developed to analyze the economic performance of a MED-TVC system for seawater desalination. A parallel/cross feed configuration is considered because of its high energy efficiency. In addition, a parametric study is performed to evaluate the effects of some operational parameters on the total water price, such as the top brine temperature, seawater temperature, motive steam flow rate, and number of effects. The obtained results indicate that the total water price is in the range of 1.73 USD/m3 for a distilled water production of 55.20 kg/s. Furthermore, the exergy destructions in the effects account for 45.8% of the total exergy destruction. The MED effects are also identified to be the most relevant component from an exergoeconomic viewpoint. Careful attention should be paid to these components. Of the total cost associated with the effects, 75.1% is due to its high thermodynamic inefficiency. Finally, the parametric study indicates that adjusting the top brine temperature, the cooling seawater temperature, the motive steam flow rate, and the number of effects has a significant impact on the TWP, which varies between 1.42 USD/m3 and 2.85 USD/m3.

Failure of an ASTM A213 T12 steel tube of a circulating fluidized bed boiler

During a maintenance shutdown, a localized bulging was observed in a section of the outermost tube of the superheater, an ASTM A213 grade T12 (UNS K11562), Cr-0.5Mo ferritic steel. The objective of this work was to investigate the failure of the steel tube, part of a L-shape superheater of a CFB boiler. The investigation was performed through microstructural characterization, chemical analysis, thermodynamic calculations, hardness measurements, tensile and creep tests, measurements of the oxide scale thickness on selected regions of the failed tube for determination of the remaining life assessment. It was concluded that the failure was due to a conjunction of long time overheating and creep. A welding defect (root dropout) caused an alteration of the steam flow and, therefore, impaired the proper heat transfer between the tube and the steam. In addition, the uneven flow of the flue gas induced a heterogeneous heat distribution along the tube length, particularly in the area facing the flue gas, evidenced by the erosion marks. The high local temperature resulted in intense oxidation, decarburization and degradation of the microstructure. As a consequence, the steel strength was reduced, with consequent bulging and failure. These points were reinforced by the results of the RUL assessment, where the value was negative at the referred region, meaning the end of its operational life.

Comparisons between Hydro and Steam Distillation Processes to Extract Prunella Vulgaris Volatile Compounds, and their Anti-oxidative Activities

Objective The aim is to verify our earlier suggestion which accounted for the dynamics of volatile compounds extraction from the herb Prunella vulgaris (PV) using steam distillation. Then, the anti-oxidative property of PV is explored.
 Methods Because we suggested earlier that the inefficient extraction using steam distillation was due to the obstruction of a mass of herb in the steam flow path, we used hydro distillation which tried to eliminate this obstacle. We used GC-MS to characterize the volatile compounds extracted, and thus compare the extraction efficiency. Then, treating the cancer cells from the SCC154 cell-line with the distillate, the cancer cell cytotoxicity was assessed using the colorimetric test reagent, the Cell Counting Kit-8. To assess the anti-oxidative activity of the PV distillate, Folin-Ciocalteu reagent was used.
 Results We successfully showed that the removal of the obstacle, formed by the mass of herb in the steam flow path, enhanced the efficiency of volatile compound extraction. Also, we showed that the PV distillate did not exhibit anti-oxidative activity.
 Conclusions Hydro distillation is a more efficient method than steam distillation to extract volatile compounds from the PV herb. However, mild heating did not provide sufficient energy to the convection of the boiling water to move the floating herb; the obstacle still existed and limited the efficiency of extraction also. For another issue of the antioxidant effect of the volatile compounds from PV, it was studied using the Folin-Ciocalteu reagent. It showed that the PV volatile compounds did not possess antioxidant property.
 Keywords: Prunella vulgaris, Xia Ku Cao, Chinese Medicine, steam distillation, hydro distillation, anti-oxidative effect

Experimental research on aerosol scrubbing characteristics under steam-air mixture submerged jet condition

The occurrence of severe accidents in nuclear power plants may lead to the leakage of radioactive aerosol. And the scrubbing efficiency of aerosol contained in the air-steam mixture submerged jet is important for assessing the radioactivity in the containment during a severe accident. Several experiments were carried out to analyze the effect of inlet pressure, aerosol diameter, submergence, and steam fraction on the scrubbing efficiency of aerosol in the jet regime. Then, the scrubbing effects of steam and different flow regimes under submerged jet conditions were investigated by comparing the experimental results. The scrubbing efficiency increased with the increase of the aerosol diameter in the air jet regime while the most penetrating region of the aerosol in the steam-air mixture jet regime is 0.2–0.4 μm. When the gas flow characteristic is subcritical flow, as the inlet pressure increases, the scrubbing efficiency increases rapidly. When the critical flow is reached, the inertial effect was the dominant factor in aerosol scrubbing due to the sufficient gas velocity, the scrubbing efficiency under different steam fractions is close to 100%. The scrubbing efficiency increases with the increase of the steam fraction, which may be caused by the increase of the temperature gradient field under subcritical flow conditions. Additionally, the increase the submergence can increase the residence time and improve the scrubbing efficiency. However, due to the decrease of the gas velocity during the gas floating, the scrubbing efficiency in the flow region of the same height is gradually decreasing.

Anisotropic Vibration Characteristics Analysis of Steam Turbine Rotor Influenced by Steam Flow Excited Force Coupling Thermal and Dynamic Loads

Abstract In order to reveal the influence of thermal and dynamic loads coupling on the vibration characteristic of steam turbine rotor, the high-pressure cylinder anisotropic rotor of a 1000-MW ultra-supercritical steam turbine was modeled by the lumped mass method. The steam flow excited force of the front eight stages obtained through the numerical simulation before and after the coupling was converted to the equivalent gas bearing and added on the rotor, and the influence of steam flow excited force on rotor vibration characteristics was obtained by the Riccati transfer matrix method. The results show that, considering the thermal and dynamic loads, the two ends of the ellipse trajectory are smaller and the middle is larger. Before and after coupling thermal and dynamic loads, the azimuth of ellipse trajectory increases with the increase of load and nodes. The greater the load, the greater the changing range of azimuth. As the load increases, the first-order natural speed of the rotor increases and the second-order natural speed decreases, but the natural speed after the coupling is noticeably lower than that before the coupling. The changing scope of the first-order amplitude shrinks with the load increasing. The first-order logarithmic decrement rate can be increased under the relatively higher load by coupling thermal and dynamic loads, but the stability margin of rotor is insufficient, which causes the instability.