The Experts below are selected from a list of 30 Experts worldwide ranked by ideXlab platform
I. B. Murmanskii - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the effect of pressure increasing in condensing heat-exchanger
Journal of Physics: Conference Series, 2017Co-Authors: I. B. Murmanskii, K. E. Aronson, A. Yu. Ryabchikov, Yu. M. Brodov, L. G. Gal'perin, D. V. BrezginAbstract:The effect of pressure increase was observed in steam condensation in the intermediate coolers of multiStage steam Ejector. Steam pressure increase for Ejector cooler amounts up to 1.5 kPa in the first Ejector Stage, 5 kPa in the second and 7 kPa in the third one. Pressure ratios are equal to 2.0, 1.3 and 1.1 respectively. As a rule steam velocities at the cooler inlets do not exceed 40...100 m/s and are subsonic in all regimes.The report presents a computational model that describes the effect of pressure increase in the cooler. The steam entering the heat exchanger tears the drops from the condensate film flowing down vertical tubes. At the inlet of heat exchanger the steam flow capturing condensate droplets forms a steam-water mixture in which the sound velocity is significantly reduced. If the flow rate of steam-water mixture in heat exchanger is greater than the sound velocity, there occurs a pressure shock in the wet steam.On the basis of the equations of mass, momentum and energy conservation the authors derived the expressions for calculation of steam flow dryness degree before and after the shock. The model assumes that droplet velocity is close to the velocity of the steam phase (slipping is absent); drops do not come into thermal interaction with the steam phase; liquid phase specific volume compared to the volume of steam is neglected; pressure shock is calculated taking into account the gas-dynamic flow resistance of the tube bundle. It is also assumed that the temperature of steam after the shock is equal to the saturation temperature.The calculations have shown that the rise of steam pressure and temperature in the shock results in dryness degree increase. For calculated flow parameters the velocity value before the shock is greater than the sound velocity. Thus, on the basis of generally accepted physics knowledge the computational model has been formulated for the effect of steam pressure rise in the condensing heat exchanger.
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Analysis of experimental characteristics of multiStage steam-jet electors of steam turbines
Thermal Engineering, 2017Co-Authors: K. E. Aronson, A. Yu. Ryabchikov, Yu. M. Brodov, D. V. Brezgin, N. V. Zhelonkin, I. B. MurmanskiiAbstract:A series of questions for specification of physical gas dynamics model in flow range of steam-jet unit and Ejector computation methodology, as well as functioning peculiarities of intercoolers, was formulated based on analysis of experimental characteristics of multiStage team-jet steam turbines. It was established that coefficient defining position of critical cross-section of injected flow depends on characteristics of the “sound tube” zone. Speed of injected flow within this tube may exceed that of sound, and pressure jumps in work-steam decrease at the same time. Characteristics of the “sound tube” define optimal axial sizes of the Ejector. According to measurement results, the part of steam condensing in the first-Stage coolant constitutes 70–80% of steam amount supplied into coolant and is almost independent of air content in steam. Coolant efficiency depends on steam pressure defined by operation of steam-jet unit of Ejector of the next Stage after coolant of steam-jet Stage, temperature, and condensing water flow. As a rule, steam entering content of steam-air mixture supplied to coolant is overheated with respect to saturation temperature of steam in the mixture. This should be taken into account during coolant computation. Long-term operation causes changes in roughness of walls of the Ejector’s mixing chamber. The influence of change of wall roughness on Ejector characteristic is similar to the influence of reverse pressure of the steam-jet Stage. Until some roughness value, injection coefficient of the Ejector Stage operating in superlimiting regime hardly changed. After reaching critical roughness, the Ejector switches to prelimiting operating regime.
K. Y. Ekşi - One of the best experts on this subject based on the ideXlab platform.
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Ultra-luminous X-ray sources as super-critical propellers
The Astrophysical Journal, 2019Co-Authors: K. Y. EkşiAbstract:We study the evolution of newborn neutron stars in high-mass X-ray binaries interacting with a wind-fed super-Eddington disk. The inner disk is regularized to a radiation-dominated quasi-spherical configuration for which we calculate the inner radius of the disk, the total luminosity of the system and the torque acting on the neutron star accordingly, following the evolution of the system through the Ejector and early propeller Stages. We find that the systems with $B \gtrsim 10^{13}$ G pass through a short ($\sim 20\,{\rm yr}$) Ejector Stage appearing as supernova impostors followed by a propeller Stage lasting $\sim 10^3\,{\rm yr}$. In the super-critical propeller Stage the system is still bright ($L\sim 10^{40}\,{\rm erg\, s^{-1}}$) due to the spindown power and therefore appears as an ultra-luminous X-ray source (ULX). The system evolves into pulsating ULX (PULX) when the neutron star spins down to a period ($P\sim 1$ s) allowing for accretion onto its surface to commence. Systems with lower magnetic fields, $B \sim 10^{11}$ G, pass through a long ($10^5\,{\rm yr}$) super-critical propeller Stage with luminosities similar to those of the ultra-luminous super-soft sources (ULS), $L \lesssim 10^{40}\,{\rm erg\, s^{-1}}$. The equilibrium periods of these systems in the accretion Stage is about $10\,{\rm ms}$, which is much smaller than the typical period range of PULX observed to date. Such systems could have a larger population, but their pulsations would be elusive due to the smaller size of the magnetosphere. Our results suggest that the ULS and some nonpulsating ULX are rapidly spinning and highly magnetized young neutron stars at the super-critical propeller Stage.
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Ultraluminous X-ray sources as supercritical propellers.
arXiv: High Energy Astrophysical Phenomena, 2017Co-Authors: M. Hakan Erkut, K. Y. Ekşi, M. Ali AlparAbstract:We study the evolution of newborn neutron stars in high-mass X-ray binaries interacting with a wind-fed super-Eddington disk. The inner disk is regularized to a radiation-dominated quasi-spherical configuration for which we calculate the inner radius of the disk, the total luminosity of the system and the torque acting on the neutron star accordingly, following the evolution of the system through the Ejector and early propeller Stages. We find that the systems with $B \gtrsim 10^{13}$ G pass through a short ($\sim 20$ year) Ejector Stage appearing as supernova impostors followed by a propeller Stage lasting $\sim 10^3$ years. In the super-critical propeller Stage the system is still bright ($L\sim 10^{40}$ erg s$^{-1}$) due to the spin-down power and therefore appears as an ultra-luminous X-ray source (ULX). The system evolves into pulsating ULX (PULX) when the neutron star spins down to a period ($P\sim 1$ s) allowing for accretion onto its surface to commence. Systems with lower magnetic fields, $B \sim 10^{11}$ G, pass through a long ($10^5$ years) super-critical propeller Stage with luminosities similar to those of the ultra-luminous super-soft sources (ULS), $L \lesssim 10^{40}$ erg s$^{-1}$. The equilibrium periods of these systems in the accretion Stage is about 10~ms, which is much smaller than the typical period range of PULX observed to date. Such systems could have a larger population, but their pulsations would be elusive due to the smaller size of the magnetosphere. Our results suggest that the ULS and some non-pulsating ULX are rapidly spinning and highly magnetized young neutron stars at the supercritical propeller Stage.
K. E. Aronson - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the effect of pressure increasing in condensing heat-exchanger
Journal of Physics: Conference Series, 2017Co-Authors: I. B. Murmanskii, K. E. Aronson, A. Yu. Ryabchikov, Yu. M. Brodov, L. G. Gal'perin, D. V. BrezginAbstract:The effect of pressure increase was observed in steam condensation in the intermediate coolers of multiStage steam Ejector. Steam pressure increase for Ejector cooler amounts up to 1.5 kPa in the first Ejector Stage, 5 kPa in the second and 7 kPa in the third one. Pressure ratios are equal to 2.0, 1.3 and 1.1 respectively. As a rule steam velocities at the cooler inlets do not exceed 40...100 m/s and are subsonic in all regimes.The report presents a computational model that describes the effect of pressure increase in the cooler. The steam entering the heat exchanger tears the drops from the condensate film flowing down vertical tubes. At the inlet of heat exchanger the steam flow capturing condensate droplets forms a steam-water mixture in which the sound velocity is significantly reduced. If the flow rate of steam-water mixture in heat exchanger is greater than the sound velocity, there occurs a pressure shock in the wet steam.On the basis of the equations of mass, momentum and energy conservation the authors derived the expressions for calculation of steam flow dryness degree before and after the shock. The model assumes that droplet velocity is close to the velocity of the steam phase (slipping is absent); drops do not come into thermal interaction with the steam phase; liquid phase specific volume compared to the volume of steam is neglected; pressure shock is calculated taking into account the gas-dynamic flow resistance of the tube bundle. It is also assumed that the temperature of steam after the shock is equal to the saturation temperature.The calculations have shown that the rise of steam pressure and temperature in the shock results in dryness degree increase. For calculated flow parameters the velocity value before the shock is greater than the sound velocity. Thus, on the basis of generally accepted physics knowledge the computational model has been formulated for the effect of steam pressure rise in the condensing heat exchanger.
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Analysis of experimental characteristics of multiStage steam-jet electors of steam turbines
Thermal Engineering, 2017Co-Authors: K. E. Aronson, A. Yu. Ryabchikov, Yu. M. Brodov, D. V. Brezgin, N. V. Zhelonkin, I. B. MurmanskiiAbstract:A series of questions for specification of physical gas dynamics model in flow range of steam-jet unit and Ejector computation methodology, as well as functioning peculiarities of intercoolers, was formulated based on analysis of experimental characteristics of multiStage team-jet steam turbines. It was established that coefficient defining position of critical cross-section of injected flow depends on characteristics of the “sound tube” zone. Speed of injected flow within this tube may exceed that of sound, and pressure jumps in work-steam decrease at the same time. Characteristics of the “sound tube” define optimal axial sizes of the Ejector. According to measurement results, the part of steam condensing in the first-Stage coolant constitutes 70–80% of steam amount supplied into coolant and is almost independent of air content in steam. Coolant efficiency depends on steam pressure defined by operation of steam-jet unit of Ejector of the next Stage after coolant of steam-jet Stage, temperature, and condensing water flow. As a rule, steam entering content of steam-air mixture supplied to coolant is overheated with respect to saturation temperature of steam in the mixture. This should be taken into account during coolant computation. Long-term operation causes changes in roughness of walls of the Ejector’s mixing chamber. The influence of change of wall roughness on Ejector characteristic is similar to the influence of reverse pressure of the steam-jet Stage. Until some roughness value, injection coefficient of the Ejector Stage operating in superlimiting regime hardly changed. After reaching critical roughness, the Ejector switches to prelimiting operating regime.
D. V. Brezgin - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the effect of pressure increasing in condensing heat-exchanger
Journal of Physics: Conference Series, 2017Co-Authors: I. B. Murmanskii, K. E. Aronson, A. Yu. Ryabchikov, Yu. M. Brodov, L. G. Gal'perin, D. V. BrezginAbstract:The effect of pressure increase was observed in steam condensation in the intermediate coolers of multiStage steam Ejector. Steam pressure increase for Ejector cooler amounts up to 1.5 kPa in the first Ejector Stage, 5 kPa in the second and 7 kPa in the third one. Pressure ratios are equal to 2.0, 1.3 and 1.1 respectively. As a rule steam velocities at the cooler inlets do not exceed 40...100 m/s and are subsonic in all regimes.The report presents a computational model that describes the effect of pressure increase in the cooler. The steam entering the heat exchanger tears the drops from the condensate film flowing down vertical tubes. At the inlet of heat exchanger the steam flow capturing condensate droplets forms a steam-water mixture in which the sound velocity is significantly reduced. If the flow rate of steam-water mixture in heat exchanger is greater than the sound velocity, there occurs a pressure shock in the wet steam.On the basis of the equations of mass, momentum and energy conservation the authors derived the expressions for calculation of steam flow dryness degree before and after the shock. The model assumes that droplet velocity is close to the velocity of the steam phase (slipping is absent); drops do not come into thermal interaction with the steam phase; liquid phase specific volume compared to the volume of steam is neglected; pressure shock is calculated taking into account the gas-dynamic flow resistance of the tube bundle. It is also assumed that the temperature of steam after the shock is equal to the saturation temperature.The calculations have shown that the rise of steam pressure and temperature in the shock results in dryness degree increase. For calculated flow parameters the velocity value before the shock is greater than the sound velocity. Thus, on the basis of generally accepted physics knowledge the computational model has been formulated for the effect of steam pressure rise in the condensing heat exchanger.
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Analysis of experimental characteristics of multiStage steam-jet electors of steam turbines
Thermal Engineering, 2017Co-Authors: K. E. Aronson, A. Yu. Ryabchikov, Yu. M. Brodov, D. V. Brezgin, N. V. Zhelonkin, I. B. MurmanskiiAbstract:A series of questions for specification of physical gas dynamics model in flow range of steam-jet unit and Ejector computation methodology, as well as functioning peculiarities of intercoolers, was formulated based on analysis of experimental characteristics of multiStage team-jet steam turbines. It was established that coefficient defining position of critical cross-section of injected flow depends on characteristics of the “sound tube” zone. Speed of injected flow within this tube may exceed that of sound, and pressure jumps in work-steam decrease at the same time. Characteristics of the “sound tube” define optimal axial sizes of the Ejector. According to measurement results, the part of steam condensing in the first-Stage coolant constitutes 70–80% of steam amount supplied into coolant and is almost independent of air content in steam. Coolant efficiency depends on steam pressure defined by operation of steam-jet unit of Ejector of the next Stage after coolant of steam-jet Stage, temperature, and condensing water flow. As a rule, steam entering content of steam-air mixture supplied to coolant is overheated with respect to saturation temperature of steam in the mixture. This should be taken into account during coolant computation. Long-term operation causes changes in roughness of walls of the Ejector’s mixing chamber. The influence of change of wall roughness on Ejector characteristic is similar to the influence of reverse pressure of the steam-jet Stage. Until some roughness value, injection coefficient of the Ejector Stage operating in superlimiting regime hardly changed. After reaching critical roughness, the Ejector switches to prelimiting operating regime.
Yu. M. Brodov - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the effect of pressure increasing in condensing heat-exchanger
Journal of Physics: Conference Series, 2017Co-Authors: I. B. Murmanskii, K. E. Aronson, A. Yu. Ryabchikov, Yu. M. Brodov, L. G. Gal'perin, D. V. BrezginAbstract:The effect of pressure increase was observed in steam condensation in the intermediate coolers of multiStage steam Ejector. Steam pressure increase for Ejector cooler amounts up to 1.5 kPa in the first Ejector Stage, 5 kPa in the second and 7 kPa in the third one. Pressure ratios are equal to 2.0, 1.3 and 1.1 respectively. As a rule steam velocities at the cooler inlets do not exceed 40...100 m/s and are subsonic in all regimes.The report presents a computational model that describes the effect of pressure increase in the cooler. The steam entering the heat exchanger tears the drops from the condensate film flowing down vertical tubes. At the inlet of heat exchanger the steam flow capturing condensate droplets forms a steam-water mixture in which the sound velocity is significantly reduced. If the flow rate of steam-water mixture in heat exchanger is greater than the sound velocity, there occurs a pressure shock in the wet steam.On the basis of the equations of mass, momentum and energy conservation the authors derived the expressions for calculation of steam flow dryness degree before and after the shock. The model assumes that droplet velocity is close to the velocity of the steam phase (slipping is absent); drops do not come into thermal interaction with the steam phase; liquid phase specific volume compared to the volume of steam is neglected; pressure shock is calculated taking into account the gas-dynamic flow resistance of the tube bundle. It is also assumed that the temperature of steam after the shock is equal to the saturation temperature.The calculations have shown that the rise of steam pressure and temperature in the shock results in dryness degree increase. For calculated flow parameters the velocity value before the shock is greater than the sound velocity. Thus, on the basis of generally accepted physics knowledge the computational model has been formulated for the effect of steam pressure rise in the condensing heat exchanger.
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Analysis of experimental characteristics of multiStage steam-jet electors of steam turbines
Thermal Engineering, 2017Co-Authors: K. E. Aronson, A. Yu. Ryabchikov, Yu. M. Brodov, D. V. Brezgin, N. V. Zhelonkin, I. B. MurmanskiiAbstract:A series of questions for specification of physical gas dynamics model in flow range of steam-jet unit and Ejector computation methodology, as well as functioning peculiarities of intercoolers, was formulated based on analysis of experimental characteristics of multiStage team-jet steam turbines. It was established that coefficient defining position of critical cross-section of injected flow depends on characteristics of the “sound tube” zone. Speed of injected flow within this tube may exceed that of sound, and pressure jumps in work-steam decrease at the same time. Characteristics of the “sound tube” define optimal axial sizes of the Ejector. According to measurement results, the part of steam condensing in the first-Stage coolant constitutes 70–80% of steam amount supplied into coolant and is almost independent of air content in steam. Coolant efficiency depends on steam pressure defined by operation of steam-jet unit of Ejector of the next Stage after coolant of steam-jet Stage, temperature, and condensing water flow. As a rule, steam entering content of steam-air mixture supplied to coolant is overheated with respect to saturation temperature of steam in the mixture. This should be taken into account during coolant computation. Long-term operation causes changes in roughness of walls of the Ejector’s mixing chamber. The influence of change of wall roughness on Ejector characteristic is similar to the influence of reverse pressure of the steam-jet Stage. Until some roughness value, injection coefficient of the Ejector Stage operating in superlimiting regime hardly changed. After reaching critical roughness, the Ejector switches to prelimiting operating regime.