Numerical Study of Unsteady Flow Phenomena in a Partial Admission Axial Steam Turbine

Abstract

This paper presents a numerical investigation of unsteady flow phenomena in a two-stage partial admission axial steam turbine. Results from unsteady three-dimensional computations are analyzed and compared with the available experimental data. Partial admission in the present study is introduced into the model by blocking only one segmental arc of the inlet guide vanes. Blocking only one segment (which corresponds to the experimental setup) makes the model unsymmetrical; therefore it is necessary to model the whole annulus of the turbine. The first stage rotor blades experience large static pressure change on their surface while passing the blocked channel. The effect of blockage on the rotor blades’ surface pressure can be seen few passages around the blocked channel. Strong changes of the blades’ surface pressure impose large unsteady forces on the blades of first stage rotor row. The circumferential static pressure plots at different cross sections along the domain indicate how the non-uniformity propagates in the domain. A peak pressure drop is seen at the cross section downstream of the first stage stator row. At further downstream cross sections, the static pressure becomes more evenly distributed. Entropy generation is higher behind the blockage due to the strong mixing and other loss mechanisms involved with partial admission. Analysis of the entropy plots at different cross sections indicates that the peak entropy moves in a tangential direction while traveling to the downstream stages. Comparisons of the unsteady three-dimensional numerical results and the experimental measurement data show good agreement in tendency. However some differences are seen in the absolute values especially behind the blockage.

Research on the Aerodynamic Performance and Collaborative Optimization Design of the Full-Scale Compact Inlet Chamber of a Nuclear-Powered Steam Turbine

“…(1) Non-uniform intake imposes bending and radial moments on the rotor, which may result in rotor vibrations [6][7][8] and even faults [9], thus affecting bearing safety [10]; (2) Non-uniform intake causes mixed loss in the cascade channel [11][12][13][14] or blast loss [15,16], and a mismatch between the chamber outlet airflow angle and the geometric angle of the first stage static cascade causes shock loss [17]; (3) Non-uniform intake causes an increase in the amplitude of airflow excitation forces on the first-stage dynamic and static lobes [18] and complex excitation force frequencies [5,13,[19][20][21][22].…”

Catastrophe Performance Analysis of Steam-Flow-Excited Vibration in the Governing Stage of Large Steam Turbines With Partial Admission

“…Sakai established a partial admission quasi-three-dimensional numerical model of steam turbine, and analyzed the influence of inlet steam's position on the turbine's efficiency [20]. Hushmandi presented a three-dimensional numerical model of steam turbine with asymmetric inlet steam, and found that the static pressure in the governing stage in circumferential direction change significantly in the case of partial admission, which resulted in a great instability force on rotor and blades [21]. In addition, Jeffrey calculated the amount of seal leakage, rotor dynamic coefficients as well as the steam exciting force by using a three-dimensional model [22,23].…”

Simulation of entropy generation during the evolution of rotating stall in a two-stage variable-pitch axial fan

“…According to Wlassow et al, 2 entropy generation is mainly caused by turbulent dissipation and facilitates identifying reduced efficiency in cases of cooling because, as an additional entropy production, the cooling flow mixes with the mainstream. The influence of the stator-rotor hub gap sealing flow was studied by Reid et al 3 Hushmandi et al 4 conducted numerical research on unsteady flow in a two-stage partial admission axial steam turbine and analysed entropy generation at different cross sections, which indicate that while travelling to the downstream stages, the peak entropy moves in a tangential direction. Mansour et al 5 reported unsteady entropy measurements in an axial turbine.…”