EXPERIMENTAL AND NUMERICAL RESEARCH ON FLOW IN THE LAST STAGE OF 1090MW STEAM TURBINE

The paper deals with experimental and numerical research in the last stage of real 1090MW steam turbine with the last steel blade length 1220mm placed in nuclear power station. The last stage was equipped with twelve static pressure taps. It was also possible to probe in two planes - before and behind the last stage using pneumatic or optical probes. A number of last stage flow parameters were determined at the root and tip wall for nominal turbine output. Among those parameters are static pressures, Mach and Reynolds numbers, last stage reactions and steam wetness. All the directly measured and evaluated flow parameters are taken from locally measured points and that is why even 3D CFD calculation of the whole system - last stage, diffuser and exhaust hood was implemented. Measured and calculated parameters are compared. Especially static pressures are in very good agreement; the only steam wetness has bigger difference due to different measurement position. Locally measured values are enough to estimate the flow behavior of the last stage. On the other hand, the CFD simulations with well determined boundary conditions, meshes and geometry and is effective tool to simulate even very complicated flow structures in the last stage and exhaust hood

EXPERIMENTAL AND NUMERICAL RESEARCH ON FLOW IN THE LAST STAGE OF 1090MW STEAM TURBINE

The paper deals with experimental and numerical research in the last stage of real 1090MW steam turbine with the last steel blade length 1220mm placed in nuclear power station. The last stage was equipped with twelve static pressure taps. It was also possible to probe in two planes - before and behind the last stage using pneumatic or optical probes. A number of last stage flow parameters were determined at the root and tip wall for nominal turbine output. Among those parameters are static pressures, Mach and Reynolds numbers, last stage reactions and steam wetness. All the directly measured and evaluated flow parameters are taken from locally measured points and that is why even 3D CFD calculation of the whole system - last stage, diffuser and exhaust hood was implemented. Measured and calculated parameters are compared. Especially static pressures are in very good agreement; the only steam wetness has bigger difference due to different measurement position. Locally measured values are enough to estimate the flow behavior of the last stage. On the other hand, the CFD simulations with well determined boundary conditions, meshes and geometry and is effective tool to simulate even very complicated flow structures in the last stage and exhaust hood

Proudění vodní páry v posledním stupni a nízkotlakém tělese parní turbíny

Práce se zabývá prouděním v tzv. studeném konci parních turbín, tedy v posledním nízkotlakém (NT) stupni turbíny a v navazujícím výstupním tělese a v nástavbě. Práce je řešena zejména jako experimentální. Experimenty byly prováděny na turbíně o nominálním výkonu 1090 MW. Nejedná se tedy o experiment na modelovém zařízení, ale přímo o experimenty na díle, kde není žádná pochybnost mezi modelováním vztahu model dílo. Na druhou stranu při experimentu na díle vzniká celá řada dalších otazníků, týkajících se zejména chování neměřených nebo neměřitelných parametrů proudu páry. Konkrétně může jít o chování odběrových regeneračních potrubí a o odsávání části média dutými rozváděcími lopatkami. Měřením byly určeny a identifikovány zdroje tlakových ztrát ve výstupním tělese, které významným způsobem ovlivňují chování posledního stupně. Byly zjištěny důležité parametry posledního stupně, jako je rozložení průtoků a účinností po výšce lopatky. Byly určeny integrální hodnoty účinností posledního stupně s vlivem a bez vlivu výstupní složky rychlosti, dále účinnost NT průtočné části, průtočné části + difuzoru, tělesa i nástavby. Byl učiněn pokus o určení odsávaného množství vodní páry dutými lopatkami posledního statorového kola. Na základě měření pak byly kalibrovány CFD metody, pomocí kterých se povedlo s vysokou mírou shody s experimentem určit rozložení proudových parametrů po délce proudové cesty. Na základě měření byla navržena nová konstrukce výstupního NT tělesa, nyní již rutinně využívána při návrhu a konstrukci parních turbín. Tato konstrukce byla přepočítána pomocí již nakalibrovaných CFD metod a byly zjištěny velmi uspokojivé výsledky z pohledu tlakových ztrát. Předkládaná práce tedy přináší ucelený komplex vědeckých údajů v tomto pořadí: 1. Experimentální měření komponenty parní turbíny 2. Analýza naměřených dat a identifikace problémového uzlu 3. CFD výpočet experimentálně měřené části turbíny a kalibrace CFD metod 4. Návrh nového typu NT těles s ohledem na minimalizaci energetických ztrát 5. CFD výpočty nového typu NT těles a analýza datThe paper deals with flow at the so called cold end steam turbines which means in last low pressure (LP) stage and in the following exhaust hood and in the condenser neck. The work is done especially as experimental. Experiments were carried out directly in the real steam turbine with nominal output of 1090 MW. These are thus not experiments on model devices, but directly on the plant where there is no doubt about the relationship between model reality. On the other hand experimenting on work can raise many potential questions, concerning mainly the behaviour of unmeasured or unmeasurable flow parameters at the cold end of the turbine. This is specifically the behaviour of heat extractions and exhaustion of the medium by the hollow stator blades. Measurements identified and specified the sources of pressure losses in the exhaust hood which considerably influence the last stage behaviour. Important last stage parameters were detected, such as flow distribution and efficiency on the blade length. Integral values were defined of last stage efficiencies with and without the influence of velocity outlet component, then the efficiency of LP flow path, flow path + the diffuser, exhaust hood and condenser neck. An attempt was made to define the exhausted amount of water steam through the hollow blades of the last stator wheel. Based on measurements the CFD methods were calibrated that helped, with a high level agreement with the experiment, to define the distribution of flow parameters along the flow passage. Based on measurements a new construction of the outer LP exhaust hood was designed that is now routinely used for design and construction of steam turbines. This construction was recalculated using the already calibrated CFD methods and very satisfactory results were found from the viewpoint of pressure losses. The presented paper thus provides an integrated complex of scientific data in the following order: 1. Experimental measurements of steam turbine components. 2. Measured data analysis and problem knot identification. 3. CFD calculation of an experimentally measured turbine part and CFD method calibration. 4. Design of the new type of LP exhaust casings considering minimization of energy losses. 5. CFD calculations of the new type LP exhaust hoods and data analysi

Efficiency calculation on 10 MW experimental steam turbine

The paper deals with defining flow path efficiency of an experimental steam turbine by using measurement of flow, torque, pressures and temperatures. The configuration of the steam turbine flow path is briefly described. Measuring points and devices are defined. The paper indicates the advantages as well as disadvantages of flow path efficiency measurement using enthalpy and torque on the shaft. The efficiency evaluation by the help pressure and temperature measurement is influenced by flow parameter distribution and can provide different values of flow path efficiency. The efficiency determination by using of torque and mass flow measurement is more accurate and it is recommended for using. The disadvantage is relatively very complicated and expensive measuring system

Experimental steam turbine T10MW cold end cooling by water spraying

The paper deals with steam flow in experimental turbine T10MW, located in Škoda laboratory. The flow was examined for low or negative outputs of the turbine, i.e. for the so called last stages ventilation. The flow path of the turbine was in the Boiler Feed Pump Turbine (BFPT) version. It had all together 4 stages out of which two were last stages with the outlet to the condenser. In the area of each of the two outlets cooling nozzles were located with water for cooling the outlet steam flow and the area of last blades root cross-sections. Cooling of these areas is necessary due to the compression heat that occurs in the off design (ventilation) regimes. Various proportional amounts of cooling water and flowing steam were tested experimentally in constant pressure behind both last stages. Due to the fact that the flow path and the exhaust hood were fitted with many static pressure taps, thermometers and with the possibility of probing the temperature field along the outlet cross-section height, a number of results were achieved. These were mainly the turbine outputs, steam flows through the blades and cooling nozzles, determination of saturation limits in individual places at the outlet as well as temperature differences measured by the probe and stable thermometers. It was found out that the amount of cooling water was oversized for blade roots cooling, while the flow at the tip was cooled only minimally. The results are beneficial both in terms of further research of steam turbines in low regimes because this is how most newly produced machines are operated and for the designers of these machines

Proudění vodní páry v posledním stupni a nízkotlakém tělese parní turbíny

Práce se zabývá prouděním v tzv. studeném konci parních turbín, tedy v posledním nízkotlakém (NT) stupni turbíny a v navazujícím výstupním tělese a v nástavbě. Práce je řešena zejména jako experimentální. Experimenty byly prováděny na turbíně o nominálním výkonu 1090 MW. Nejedná se tedy o experiment na modelovém zařízení, ale přímo o experimenty na díle, kde není žádná pochybnost mezi modelováním vztahu model dílo. Na druhou stranu při experimentu na díle vzniká celá řada dalších otazníků, týkajících se zejména chování neměřených nebo neměřitelných parametrů proudu páry. Konkrétně může jít o chování odběrových regeneračních potrubí a o odsávání části média dutými rozváděcími lopatkami. Měřením byly určeny a identifikovány zdroje tlakových ztrát ve výstupním tělese, které významným způsobem ovlivňují chování posledního stupně. Byly zjištěny důležité parametry posledního stupně, jako je rozložení průtoků a účinností po výšce lopatky. Byly určeny integrální hodnoty účinností posledního stupně s vlivem a bez vlivu výstupní složky rychlosti, dále účinnost NT průtočné části, průtočné části + difuzoru, tělesa i nástavby. Byl učiněn pokus o určení odsávaného množství vodní páry dutými lopatkami posledního statorového kola. Na základě měření pak byly kalibrovány CFD metody, pomocí kterých se povedlo s vysokou mírou shody s experimentem určit rozložení proudových parametrů po délce proudové cesty. Na základě měření byla navržena nová konstrukce výstupního NT tělesa, nyní již rutinně využívána při návrhu a konstrukci parních turbín. Tato konstrukce byla přepočítána pomocí již nakalibrovaných CFD metod a byly zjištěny velmi uspokojivé výsledky z pohledu tlakových ztrát. Předkládaná práce tedy přináší ucelený komplex vědeckých údajů v tomto pořadí: 1. Experimentální měření komponenty parní turbíny 2. Analýza naměřených dat a identifikace problémového uzlu 3. CFD výpočet experimentálně měřené části turbíny a kalibrace CFD metod 4. Návrh nového typu NT těles s ohledem na minimalizaci energetických ztrát 5. CFD výpočty nového typu NT těles a analýza datThe paper deals with flow at the so called cold end steam turbines which means in last low pressure (LP) stage and in the following exhaust hood and in the condenser neck. The work is done especially as experimental. Experiments were carried out directly in the real steam turbine with nominal output of 1090 MW. These are thus not experiments on model devices, but directly on the plant where there is no doubt about the relationship between model reality. On the other hand experimenting on work can raise many potential questions, concerning mainly the behaviour of unmeasured or unmeasurable flow parameters at the cold end of the turbine. This is specifically the behaviour of heat extractions and exhaustion of the medium by the hollow stator blades. Measurements identified and specified the sources of pressure losses in the exhaust hood which considerably influence the last stage behaviour. Important last stage parameters were detected, such as flow distribution and efficiency on the blade length. Integral values were defined of last stage efficiencies with and without the influence of velocity outlet component, then the efficiency of LP flow path, flow path + the diffuser, exhaust hood and condenser neck. An attempt was made to define the exhausted amount of water steam through the hollow blades of the last stator wheel. Based on measurements the CFD methods were calibrated that helped, with a high level agreement with the experiment, to define the distribution of flow parameters along the flow passage. Based on measurements a new construction of the outer LP exhaust hood was designed that is now routinely used for design and construction of steam turbines. This construction was recalculated using the already calibrated CFD methods and very satisfactory results were found from the viewpoint of pressure losses. The presented paper thus provides an integrated complex of scientific data in the following order: 1. Experimental measurements of steam turbine components. 2. Measured data analysis and problem knot identification. 3. CFD calculation of an experimentally measured turbine part and CFD method calibration. 4. Design of the new type of LP exhaust casings considering minimization of energy losses. 5. CFD calculations of the new type LP exhaust hoods and data analysi

Analysis of geometric errors of throat sizes of last stage blades in a mid-size steam turbine

Steam turbine technology with enhanced flexibility will continue to participate in electric power supply mixes. Last stage blades secure the reliability of a steam turbine and require high precision manufacturing and assembly. This case study presents a statistical analysis of geometric errors of the throat sizes of the last stage blades in a mid-size steam turbine. A 3D optical scanner is employed to capture detailed geometries of rotor blades and a half of assembled nozzle diaphragm. Unrolled cylinder cross-sections are used to evaluate 2D geometrical features such as blade throats and areas at three different diameters, and the results are compared to intended designs. In addition, linear correlations between the throat size and blade pitch, area and trailing edge thickness are established, and blade throat position shifts are quantified. Such a comprehensive study is presented for the first time, and some useful conclusions can be retrieved from this case study

Effect of manufacturing processes on blade throat size and position in a steam turbine diaphragm

Despite a sustainable energy future, steam turbines are requisite for the reliability and security of the electric power supply in many countries. Accurate and precise manufacturing of the steam path is crucial to turbine efficiency. Before entering the rotor blades, the steam must be correctly guided using stationary blading in a diaphragm. Steam turbine diaphragms are complicated components to manufacture, and welding is the most common fabrication method. A case study presented in this paper employs data from a 3D optical scanner for a geometric deviation analysis of the upper half of the diaphragm at two production steps, after complete welding and after final machining. Unrolled cylinder cross-sections at different diameters are used to evaluate the blade throat sizes and positions compared to the nominal geometry. The results indicate significant geometric changes between the two fabrication steps, and several suggestions are put forward for targeted future work

Numerical and Analytical Calculation of Flow During Steam Blowing

In the paper results are described of numerical simulations of the flow during the steam blowing between the boiler drum and the outlet to the atmosphere. Numerical flow simulations are compared to the analytical approach that best describes the flow during the blowing, i.e. the Fanno flow. The proposed methodology of analytical calculation can be, with a reasonable deviation from reality, used in control of velocity and flow in the pipe outlet cross-section

Wet steam flow in 1100 MW turbine

The paper deals with the wet steam flow in a steam turbine operating in a nuclear power plant. Using a pneumatic and an optical probe, the static pressure, steam velocity, steam wetness and the fine water droplets diameter spectra were measured before and beyond the last turbine low-pressure stage. The results of the experiment serve to understand better the wet steam flow and map its liquid phase in this area. The wet steam data is also used to modify the condensation model used in computational fluid dynamics simulations. The condensation model, i.e. the nucleation rate and the growth rate of the droplets, is adjusted so that results of the numerical simulations are in a good agreement with the experimental results. A 3D computational fluid dynamics simulations was performed for the lowpressure part of the turbine considering non-equilibrium steam condensation. In the post-processing of the of the numerical calculation result, the thermodynamic wetness loss was evaluated and analysed. Loss analysis was performed for the turbine outputs of 600, 800, and 1100 MW, respectively