The Effect of Secondary Air Injection on the Performance of a Transonic Turbine Stage

Girgis, Sami; Vlasic, E. P.; Lavoie, Jonathan; Moustapha, S. H.

doi:10.1115/gt2002-30340

Cited by 10 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…By means of this loss breakdown method, the space location has distinguished viscous shear loss and blockage effects described before, and the proportion of the three losses for IR ¼ 0.9% is 61.09% for the viscous shear loss, 19.05% for the vortex interaction between the rotor hub passage vortex and egress flow, and 19.86% for the blockage effect. This proportion agrees well with the results that the viscous shear gives rise to more than half the total losses, 9,12 while the loss from the vortex interaction is close to that from the blockage effect. 12 The losses caused by the blockage effect for the stator and rotor under different rim seal flow rates are listed in Table 4.…”

Section: Loss Mechanismssupporting

confidence: 91%

“…However, the influence of the rim seal flow on the mainstream involves complex factors, such as rim seal flow blockage, viscous shear between the rim seal flow and mainstream and vortex interaction between the rim seal flow and hub passage vortex. [9][10] Among these factors, the blockage effect resulting from the rim seal flow is one of the most significant flow phenomena and has not been investigated in detail. Schuepbach et al 11 found that the pressure in front of the ejection increased as a consequence of the introduced blockage when the ejection left the rim seal with the experimental and computational method.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Numerical investigation of the blockage effect caused by rim seal flow

Fan

Wang

2020

Proceedings of the Institution of Mechanical Engineers, Part G:

View full text Add to dashboard Cite

Blockage effect caused by the rim seal flow is one of the most important sources of loss in the interaction between the turbine rim seal flow and mainstream and has not been investigated in detail. To research the blockage effect, numerical simulations were presented for different rim seal flow rates. The pressure distribution was investigated and losses resulting from the blockage effect were analyzed. In addition, the influences of swirl ratio, inclination angle, and width were revealed. Results show that the blockage effect originates from the pushing and compression of egress flow to the mainstream and results in local pressure increase. The egress flow mainly blocks the mainstream downstream of the stator suction side and above the egress flow. Furthermore, the blockage effect strengthens with the increase of rim seal flow rate and weakens with the increase of swirl ratio. The effect of inclination angle and width on the blockage effect could be neglected. With the increase of rim seal flow rate, the blockage on the stator suction side causes the secondary losses to be reduced and the increasing expansion in the rotor passage leads to more losses at the tip and surface. A loss isolation method that defines the space region of loss in the rotor domain is established and proven to be effective. On an average, relative to the design condition, the overall loss introduced by the blockage effect increases by about 89.44% per 1% increase in the rim seal flow rate.

show abstract

Section: Loss Mechanismssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Numerical investigation of the blockage effect caused by rim seal flow

Fan

Wang

2020

Proceedings of the Institution of Mechanical Engineers, Part G:

View full text Add to dashboard Cite

show abstract

“…As a consequence, the total anergy produced along the domain increases with an increased purge flow rate (see Fig. 15 c) which is compliant with studies dealing with the influence of purge flow rate on the losses generated in turbines [11,31,33] .…”

Section: Influence Of Purge Flow Rate On Viscous Anergy Productionsupporting

confidence: 84%

Description of the flow in a linear cascade with an upstream cavity part 2: Assessing the loss generated using an exergy formulation (draft)

et al. 2020

View full text Add to dashboard Cite

Purge air is injected in cavities at hub of axial turbines to prevent hot mainstream gas ingestion into interstage gaps. This process induces additional losses for the turbine due to an interaction between purge and mainstream flow. To deal with this issue, this paper is devoted to the study of a low speed linear cascade with an upstream cavity at a Reynolds number representative of a low-pressure turbine using RANS and LES with inlet turbulence injection. Different rim seal geometries and purge flow rates are studied. Details about numerical methods and comparison with experiments can be found in a companion paper. The analysis here focuses on the loss generation based on the description of the flow and influence of the turbulence introduced in the companion paper. The measure of loss is based on an exergy analysis (i.e. energy in the purpose to generate work) that extends a more common measure of loss in gas turbines, entropy. The loss analysis is led for a baseline case by splitting the simulation domain in the contributions related to the boundary layers over the wetted surfaces and the remaining domain (i.e. the complementary of boundary layers domains) where secondary flows and related loss are likely to occur. The analysis shows the strong contribution of the blade suction side boundary layer, secondary vortices in the passage and wake at the trailing edge on the loss generation. The study of different pur ge flow rates shows increased secondary vortices energy and subsequent loss for higher purge flow rates. The rim seal geometry with axial overlapping promotes a delayed development of secondary vortices in the passage compared to simple axial gap promoting lower levels of loss.

show abstract

Effect of the Hub Endwall Cavity Flow on the Flow-Field of a Transonic High-Pressure Turbine

Paniagua

Dénos

Almeida

2004

Journal of Turbomachinery

View full text Add to dashboard Cite

In high-pressure turbines, a small amount of cold flow is ejected at the hub from the cavity that exists between the stator and the rotor disk. This prevents the ingestion of hot gases into the wheel-space cavity, thus avoiding possible damage. This paper analyzes the interaction between the hub-endwall cavity flow and the mainstream in a high-pressure transonic turbine stage. Several cooling flow ratios are investigated under engine representative conditions. Both time-averaged and time-resolved data are presented. The experimental data is successfully compared with the results of a three-dimensional steady Navier-Stokes computation. Despite the small amount of gas ejected, the hub-endwall cavity flow has a significant influence on the mainstream flow. The Navier-Stokes predictions show how the ejected cold flow is entrained by the rotor hub vortex. The time-resolved static pressure field around the rotor is greatly affected when traversing the non-uniform vane exit flow field. When the cavity flow rate is increased, the unsteady forces on the rotor airfoil are reduced. This is linked to the decrease of vane exit Mach number caused by the blockage of the ejected flow.

show abstract

The Effect of Secondary Air Injection on the Performance of a Transonic Turbine Stage

Cited by 10 publications

References 0 publications

Numerical investigation of the blockage effect caused by rim seal flow

Numerical investigation of the blockage effect caused by rim seal flow

Description of the flow in a linear cascade with an upstream cavity part 2: Assessing the loss generated using an exergy formulation (draft)

Effect of the Hub Endwall Cavity Flow on the Flow-Field of a Transonic High-Pressure Turbine

Contact Info

Product

Resources

About