An Experimental Study on Partial Admission in a Two-Stage Axial Air Test Turbine With Numerical Comparisons

Fridh, Jens; Bunkute, Birute; Fakhrai, Reza; Fransson, Torsten

doi:10.1115/gt2004-53774

Cited by 14 publications

(8 citation statements)

References 6 publications

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“…The inhomogeneous flow attenuation and structure in 4stage turbine was shown by experimental measure and reported by Bohn [8]. Fridh et al [9] conducted experimental research in partial admission air turbine and the comparison with 2-D compressible model demonstrated the importance of radial components.…”

Section: Introductionmentioning

confidence: 90%

Unsteady flow and load in 50% partial admission control stage with different admitting arc distributions

2016

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Full 3-D unsteady numerical investigation on an axial air turbine in 50% partial admission is conducted. The partial admission turbines are under different unsteady loading and unloading process, as well as flow parameters, respectively. The loss coefficient and static pressure distributions at the key position are presented in detail to analyze the non-uniformity originated from partial admission. The results show that the non-uniformity decreases along flow direction and the efficiency of control stage also decreases but with the uniformity improved downstream of the rotors with increasing admitting numbers in equal partial admission degree. The reasons for efficiency decreasing are reasonably explained with windage and sector end losses presented by static entropy distributions. The periodic changes of unsteady forces in amplitude and direction are also compared and transformed in the frequency domain by fast Fourer transform method. The largest circumferential exciting force factor which is remarkably larger than the corresponding axial exciting force factor decreases by 13.2% with the increase of admitting arc number. Compared with the common distribution of two symmetric admitting arcs, the maximum exciting force factor of triangle admitting arc distribution drops 11.3% with the mere efficiency decrease of 1.32%. The multiple admitting arc turbines are more conducive to be applied to submarines which concerns more about exciting force other than efficiency. Efficiency and unsteady forces are both worth being taken into consideration in the practical applications.

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Section: Introductionmentioning

confidence: 90%

Unsteady flow and load in 50% partial admission control stage with different admitting arc distributions

2016

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“…Centrifuging of the fluid in the nonadmitted part of the rotor wheel causes an additional form of loss, known as the windage loss. [1][2][3]10,11 Therefore, it is generally known that the efficiency of a partially admitted stage is lower than that of a fully admitted one.…”

Section: Introductionmentioning

confidence: 99%

“…To improve the efficiency of partial admission turbines, several experimental and theoretical studies have been performed to enhance the physical understanding of the nonuniform flow field and the losses involved in the partial admission turbine. 10 Ohlsson 4 addressed the partial admission of an axial flow impulse turbine by a theoretical approach. The results showed that the maximum efficiency of the partial admission turbine occurred at lower velocity ratio.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic performance analysis and optimization of a turbine duct with low degree of partial admission

Sui

Zhao

Sun

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part G:

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A partial admission turbine duct with outlet-to-inlet area ratio greater than unity can increase the admission degree of the downstream turbine stage and, thus improve the performance of a multistage turbine with a low partial admission degree. However, the upstream flow structures of ducts, such as secondary flow, especially the circumferential nonuniformities originating from the effect of the partial admission, make the flow in ducts complex. The complexity of the flow has a negative impact on the performance of ducts. In the present investigation, numerical study of the flow behavior within ducts is done to evaluate the effect of the partial admission on the performance of the ducts. The study is carried out with regard to two cases, i.e. which are with the same duct geometry but are at different working conditions to highlight the impact of partial admission on the performance of ducts. Case 1 is used as baseline. It is designed based on circumferential mass-averaged flow conditions at ducts inlet. It causes the circumferential nonuniformities originating from the partial admission to have no impact on the performance of case 1. Case 2, which considers partial admission, is compared with case 1 to know the impact of the partial admission on the performance of ducts, and to give guidelines to design a duct for the partial admission turbines. Since the duct inlet conditions is a result of the interaction between partial admission turbine and duct, a straightforward way to consider the effect of the partial admission is to simulate the flows in ducts and upstream turbines contemporaneously. Comparative results indicate that the mixing of main flow in the admitted channel and the windage fluid from the unadmitted channel occurs at the duct inlet close to the duct circumferential wall. The adverse pressure gradient of case 2 in that region becomes larger than that of case 1. As a result, the flow separates at that region deteriorating the performance of ducts. Based on the simulation results of the previous cases, case 2's circumferential wall surface, which is along the gas swirling direction is shrunk to accelerate the flow and, thereby, overcome the adverse pressure gradient imposed by the effect of the partial admission. The results show that the separation is restrained and the decrease in total pressure loss is 52.9%.

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“…The rotor passages entering and leaving the jets, originate from flow through certain segments of the first stator rows, would induce additional entropy increases. Fridh et al (2004) experimentally measured the aerodynamic and efficiency of the two stage axial turbine with low reaction steam turbine blades at different partial admission degrees, as well as 2D numerical simulations. The total-to-static turbine efficiency drops and the efficiency peak appears at lower velocity ratios for lower partial admission degrees mostly due to the pumping losses increases with the increased velocity ratios according to their experimental data.…”

Section: Introductionmentioning

confidence: 99%

Unsteady Aerodynamics and Forces Characteristics of Dual Row Control Stage with Partial Admission Condition

Wen

et al. 2017

European Conference on Turbomachinery Fluid Dynamics and Hermodynamics

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Unsteady aerodynamic performance and forces on the rotor blades of dual row control stage with partial admission condition were numerically investigated using three-dimensional unsteady Reynolds-Averaged Navier-Stokes (URANS) and The rotor blades were subject to large unsteady and periodic forces while traveling along the circumferential direction. The magnitude and direction of the unsteady forces on the rotor blades were significantly influenced by the rotor blades entering or leaving the admission arcs. The spectrum analysis of the excitation forces on the rotor blades show that the high amplitudes caused by partial admission were at low multiples of rotational frequency.

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An Experimental Study on Partial Admission in a Two-Stage Axial Air Test Turbine With Numerical Comparisons

Cited by 14 publications

References 6 publications

Unsteady flow and load in 50% partial admission control stage with different admitting arc distributions

Unsteady flow and load in 50% partial admission control stage with different admitting arc distributions

Aerodynamic performance analysis and optimization of a turbine duct with low degree of partial admission

Unsteady Aerodynamics and Forces Characteristics of Dual Row Control Stage with Partial Admission Condition

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