Numerical Analysis Of Flow Field Characteristics In Initial Condensation Zone Of Supercritical H₂O/CO₂ Steam Turbine

Power is the most important secondary energy.The status of the steam turbine in the power generation industry is very important,so how to guarantee the operation safety and efficiency of the steam turbine is very important subject.For the national power industry,the improvement of efficiency is a big step forward.There is a huge contribution to the development of the economy as a whole,but the existence of the internal flow in wet steam turbine,restricting the development of economy.And the safety of the operation had the very big threat,especially when working medium containing CO₂ can accelerate the corrosion rate,in which CO₂ partial pressure,working medium temperature,mixing working medium velocity,and the concentration of CO₂ in the initial condensation zone plays an important role.In this paper,the flow field characteristics of supercritical H₂O/CO₂ steam turbine in the initial condensation zone are reviewed and analyzed.On this basis,through the Blade Gen,steam turbine low pressure supercritical H₂O/CO₂ three-dimensional entity model automatic meshing in Turbo Grid with structured grids,provided by CFX.With supercritical H₂O/CO₂turbine stage 12 to 15,the equilibrium and non-equilibrium condensation flow model of numerical simulation determine the location of the initial condensation zone,and analyze the important thermodynamic parameters distribution rule in the flow field and the mechanism of the condensation flow.In the stator blade,due to large enthalpy drop,steam expands violently and a large amount of steam condenses.In the rotor blade,the variation of various thermodynamic parameters is relatively moderate,and the condensation area of steam is relatively small.The initial condensation zone is generated at the trailing edge of the stator blade at the 12-stage,and steam crosses the saturation line until the thermal imbalance reaches the extreme,i.e.Wilson point,and the condensation core is rapidly generated.Compared with other parts of the blade,the condensation core is more easily generated at the root of the blade,because the expansion rate here is larger and the pressure here is smaller.The number of droplets is the largest at the top of the blade.Due to the effect of centrifugal force on primary droplets and the tear of main flow on secondary droplets,a large number of droplets are accumulated at the top of the blade.The increase of load will advance the location of the initial setting zone,and the presence of CO₂ may lead to acid corrosion.The non-equilibrium effect leads to the decrease of the flow capacity of steam turbine and the decrease of steam working capacity.Compared with the non-equilibrium model,the humidity in the equilibrium model is larger.During the study,the distribution rules of physical and thermal parameters,such as pressure,humidity,speed,etc.Related to CO₂ corrosion in the low-pressure section of the supercritical H₂O/CO₂ steam turbine were obtained,as well as the location of the initial setting zone,which provided a research basis for the study and analysis of the acid corrosion process in the initial condensation zone in the future.