Effects of Purge Flow Configuration on Sealing Effectiveness in a Rotor-Stator Cavity

2017 ◽  
Author(s):  
Kenneth Clark ◽  
Michael Barringer ◽  
David Johnson ◽  
Karen Thole ◽  
Eric Grover ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Cavity Model ◽  
Flow Rates ◽  
Turbine Engine ◽  
Flow Configuration ◽  
Hot Gas ◽  
Purge Flow ◽  
Secondary Air ◽  
Critical Components ◽  
Flow Tracer

Secondary air is bled from the compressor in a gas turbine engine to cool turbine components and seal the cavities between stages. Unsealed cavities can lead to hot gas ingestion, which can degrade critical components or, in extreme cases, can be catastrophic to engines. For this study, a 1.5 stage turbine with an engine-realistic rim seal was operated at an engine-relevant axial Reynolds number, rotational Reynolds number, and Mach number. Purge flow was introduced into the inter-stage cavity through distinct purge holes for two different configurations. This paper compares the two configurations over a range of purge flow rates. Sealing effectiveness measurements, deduced from the use of CO2 as a flow tracer, indicated that the sealing characteristics were improved by increasing the number of uniformly distributed purge holes and improved by increasing levels of purge flow. For the larger number of purge holes, a fully sealed cavity was possible while for the smaller number of purge holes, a fully sealed cavity was not possible. For this representative cavity model, sealing effectiveness measurements were compared with a well-accepted orifice model derived from simplified cavity models. Sealing effectiveness levels at some locations within the cavity were well-predicted by the orifice model, but due to the complexity of the realistic rim seal and the purge flow delivery, the effectiveness levels at other locations were not well-predicted.

Effects of Purge Flow Configuration on Sealing Effectiveness in a Rotor–Stator Cavity

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Kenneth Clark ◽  
Michael Barringer ◽  
David Johnson ◽  
Karen Thole ◽  
Eric Grover ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Cavity Model ◽  
Flow Rates ◽  
Turbine Engine ◽  
Flow Configuration ◽  
Hot Gas ◽  
Purge Flow ◽  
Secondary Air ◽  
Critical Components ◽  
Flow Tracer

Secondary air is bled from the compressor in a gas turbine engine to cool turbine components and seal the cavities between stages. Unsealed cavities can lead to hot gas ingestion, which can degrade critical components or, in extreme cases, can be catastrophic to engines. For this study, a 1.5 stage turbine with an engine-realistic rim seal was operated at an engine-relevant axial Reynolds number, rotational Reynolds number, and Mach number. Purge flow was introduced into the interstage cavity through distinct purge holes for two different configurations. This paper compares the two configurations over a range of purge flow rates. Sealing effectiveness measurements, deduced from the use of CO2 as a flow tracer, indicated that the sealing characteristics were improved by increasing the number of uniformly distributed purge holes and improved by increasing levels of purge flow. For the larger number of purge holes, a fully sealed cavity was possible, while for the smaller number of purge holes, a fully sealed cavity was not possible. For this representative cavity model, sealing effectiveness measurements were compared with a well-accepted orifice model derived from simplified cavity models. Sealing effectiveness levels at some locations within the cavity were well-predicted by the orifice model, but due to the complexity of the realistic rim seal and the purge flow delivery, the effectiveness levels at other locations were not well-predicted.

Effects of Purge Jet Momentum on Sealing Effectiveness

2016 ◽  
Author(s):  
Kenneth Clark ◽  
Michael Barringer ◽  
Karen Thole ◽  
Carey Clum ◽  
Paul Hiester ◽  
...  
Keyword(s):  
Flow Rate ◽  
Momentum Flux ◽  
Reynolds Numbers ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Swirl Velocity ◽  
Purge Flow ◽  
Secondary Air ◽  
Flow Tracer ◽  
Mach And Reynolds Numbers

Driven by the need for higher cycle efficiencies, overall pressure ratios for gas turbine engines continue to be pushed higher thereby resulting in increasing gas temperatures. Secondary air, bled from the compressor, is used to cool turbine components and seal the cavities between stages from the hot main gas path. This paper compares a range of purge flows and two different purge hole configurations for introducing the purge flow into the rim cavities. In addition, the mate face gap leakage between vanes is investigated. For this particular study, stationary vanes at engine relevant Mach and Reynolds numbers were used with a static rim seal and rim cavity to remove rotational effects and isolate gas path effects. Sealing effectiveness measurements, deduced from the use of CO2 as a flow tracer, indicate that the effectiveness levels on the stator and rotor side of the cavity depend on the mass and momentum flux ratios of the purge jets relative to the swirl velocity. For a given purge flow rate, fewer purge holes resulted in better sealing than the case with a larger number of holes.

Effects of Purge Jet Momentum on Sealing Effectiveness

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Kenneth Clark ◽  
Michael Barringer ◽  
Karen Thole ◽  
Carey Clum ◽  
Paul Hiester ◽  
...  
Keyword(s):  
Flow Rate ◽  
Momentum Flux ◽  
Reynolds Numbers ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Swirl Velocity ◽  
Purge Flow ◽  
Secondary Air ◽  
Flow Tracer ◽  
Mach And Reynolds Numbers

Driven by the need for higher cycle efficiencies, overall pressure ratios for gas turbine engines continue to be pushed higher thereby resulting in increasing gas temperatures. Secondary air, bled from the compressor, is used to cool turbine components and seal the cavities between stages from the hot main gas path. This paper compares a range of purge flows and two different purge hole configurations for introducing the purge flow into the rim cavities. In addition, the mate face gap leakage between vanes is investigated. For this particular study, stationary vanes at engine-relevant Mach and Reynolds numbers were used with a static rim seal and rim cavity to remove rotational effects and isolate gas path effects. Sealing effectiveness measurements, deduced from the use of CO2 as a flow tracer, indicate that the effectiveness levels on the stator and rotor side of the cavity depend on the mass and momentum flux ratios of the purge jets relative to the swirl velocity. For a given purge flow rate, fewer purge holes resulted in better sealing than the case with a larger number of holes.

Simplified Ingestion Model Assessment for 1D Gas Turbine Engine Secondary Flow Network

2017 ◽  
Author(s):  
Ashish Negi ◽  
A. V. Mirzamoghadam ◽  
Sushilkumar Thamke ◽  
Balakrishnan Thangavel
Keyword(s):  
Gas Turbine ◽  
Pressure Profile ◽  
Gas Turbine Engine ◽  
Model Assessment ◽  
Rotating Disc ◽  
Turbine Engine ◽  
Hot Gas ◽  
Secondary Air ◽  
Upper Rim ◽  
Circumferential Pressure

Modeling of hot gas ingestion in a gas turbine engine is critical because its accuracy directly affects performance as well as turbine durability. In this paper, ASU ingestion test rig data accompanied by its published ingress/egress discharge coefficients (Cdi and Cde , formulation) are used to propose a simplified 1D ingestion model embedded in the secondary air system software (Network). The proposed externally induced ingress model includes separate boundary nodes with equal static pressure in the annulus hub, and distinct circumferential pressure variation in the form of normalized annulus pressure at the hub (P1 – P1avg)/(P1max – P1min). The corresponding Cdi and Cde for the engine conditions are scaled based on rig-to-engine non-dimensional minimum purge, Cwmin where engine Cwmin uses the actual (P1 – P1avg)/(P1max – P1min) derived from previously published CFD data along with the effective rim-seal overlap clearance. The vane pitch integrated driving pressure difference at the hub for the ingestion used in the orifice model comes from an embedded saw-tooth assumption on the circumferential pressure profile. Recirculation of ingested hot gas from the upper rim cavity to the lower wheel space is considered by comparing the supplied purge flow to the rotating disc entrainment requirement. The proposed model is compared with another model based on constant Cdi / Cde ratio of 0.14 published by the University of Bath. Engine test data from a previously published engine configuration is used to assess the appropriate model for engine. The probability of failure in violating the lower rim cavity sealing effectiveness limit based on analysis of variation (AOV) was conducted under both formulations and the results are presented.

Correlating Cavity Sealing Effectiveness to Time-Resolved Rim Seal Events in the Presence of Vane Trailing Edge Flow

2021 ◽  
Author(s):  
Shawn Siroka ◽  
Iván Monge-Concepción ◽  
Reid A. Berdanier ◽  
Michael D. Barringer ◽  
Karen A. Thole ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Maximum Amplitude ◽  
Flow Instabilities ◽  
Time Varying ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Time Resolved ◽  
Flow Rates ◽  
Hot Gas ◽  
Purge Flow

Abstract The cavity region between the rotor and stator relies on hardware seals and purge flow to discourage hot gas path air from being ingested into the unprotected wheel space. However, ingestion can occur due to a combination of disk pumping, periodic vane-blade interactions, and three-dimensional seal geometry effects. These mechanisms create flow instabilities that are detrimental to cavity seal performance under certain conditions. In this paper, a one-stage turbine operating at engine representative conditions was utilized to study the effect of steady and time-resolved under-platform cavity temperatures and pressures across a range of coolant flow rates in the presence of vane trailing edge (VTE) flow. This study correlates time-resolved pressure with time-resolved temperature to identify primary frequencies driving ingestion. At certain flow rates, the time-resolved pressures are out of phase with the temperatures, indicating ingestion. These same flow rates were found to correlate to an inflection region in the cooling effectiveness curve where the maximum amplitude of the time-varying behavior coincides with the cooling effectiveness inflection point. Using a time-accurate computational model, simulations near this inflection region illustrate ingestion of high-swirl VTE flow into the cavity region which creates a buffer in the rim seal between swirled main gas path flow and axially injected purge coolant helping to suppress the amplitude of time-resolved behavior.

Effects of Selected Gas Stream Parameters and Coolant Properties on Liquid Film Cooling

1964 ◽  
Vol 86 (2) ◽  
pp. 271-278 ◽  
Author(s):  
C. F. Warner ◽  
D. L. Emmons
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Liquid Film ◽  
Film Cooling ◽  
Boundary Layer Theory ◽  
Simple Analysis ◽  
Flow Rates ◽  
Hot Gas ◽  
Pipe Flows ◽  
Temperature Distributions

Experimental determinations were made of the effects of changes in the temperature, pressure, and Reynolds number of a hot gas stream upon the required flow rate of a single liquid (water) used for film cooling different lengths (4, 5, 6, 7, and 8 in.) of a cylindrical rocket motor combustion chamber. Experiments were also conducted with other coolants, such as anhydrous ammonia, ethyl alcohol, and Freon-113 for determining the effects of the physical properties of those liquids on the required film-coolant flow rates for a single condition of gas stream temperature, pressure, and Reynolds number. Determinations were also made of the heat flux and wall temperature distributions downstream from the terminus of the liquid film; that is, in the region where there is considerable vaporized film coolant in the vicinity of the chamber wall. The experimental results are correlated by means of a simple analysis based on turbulent boundary-layer theory applicable in pipe flows.

scholarly journals Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Blanke ◽  
Markus Hagenkamp ◽  
Bernd Döring ◽  
Joachim Göttsche ◽  
Vitali Reger ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Circular Ring ◽  
Flow Conditions ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

Liquid Jet Impingement Cooling of a Rotating Disk

1986 ◽  
Vol 108 (3) ◽  
pp. 540-546 ◽  
Author(s):  
H. J. Carper ◽  
J. J. Saavedra ◽  
T. Suwanprateep
Keyword(s):  
Reynolds Number ◽  
Average Nusselt Number ◽  
Convective Heat Transfer Coefficient ◽  
Jet Impingement ◽  
Rotating Disk ◽  
Liquid Jet ◽  
Flow Rates ◽  
Impingement Cooling ◽  
Angular Velocities ◽  
Jet Nozzle

Results are presented from an experimental study conducted to determine the average convective heat transfer coefficient for the side of a rotating disk, with an approximately uniform surface temperature, cooled by a single liquid jet of oil impinging normal to the surface. Tests were conducted over a range of jet flow rates, jet temperatures, jet radial positions, and disk angular velocities with various combinations of three jet nozzle and disk diameters. Correlations are presented that relate the average Nusselt number to rotational Reynolds number, jet Reynolds number, jet Prandtl number, and dimensionless jet radial position.

Second Law Analysis of Spray Evaporation

1990 ◽  
Vol 112 (2) ◽  
pp. 130-135 ◽  
Author(s):  
S. K. Som ◽  
A. K. Mitra ◽  
S. P. Sengupta
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Entropy Generation ◽  
Exergy Analysis ◽  
Droplet Evaporation ◽  
Second Law ◽  
Hot Gas ◽  
Second Law Analysis ◽  
Initial Drop ◽  
Parallel Stream

A second law analysis has been developed for an evaporative atomized spray in a uniform parallel stream of hot gas. Using a discrete droplet evaporation model, an equation for entropy balance of a drop has been formulated to determine numerically the entropy generation histories of the evaporative spray. For the exergy analysis of the process, the rate of heat transfer and that of associated irreversibilities for complete evaporation of the spray have been calculated. A second law efficiency (ηII), defined as the ratio of the total exergy transferred to the sum of the total exergy transferred and exergy destroyed, is finally evaluated for various values of pertinent input parameters, namely, the initial Reynolds number (Rei = 2ρgVixi/μg) and the ratio of ambient to initial drop temperature (Θ∞′/Θi′).

Experimental Investigation of Turbine Stage Flow Field and Performance at Varying Cavity Purge Rates and Operating Speeds

2016 ◽  
Author(s):  
Johan Dahlqvist ◽  
Jens Fridh
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
High Speed ◽  
Control Volume ◽  
Spatial Average ◽  
Turbine Stage ◽  
Wide Range ◽  
Annulus Flow ◽  
Purge Flow ◽  
Secondary Air

The aspect of hub cavity purge has been investigated in a high-pressure axial low-reaction turbine stage. The cavity purge is an important part of the secondary air system, used to isolate the hot main annulus flow from cavities below the hub level. A full-scale cold-flow experimental rig featuring a rotating stage was used in the investigation, quantifying main annulus flow field impact with respect to purge flow rate as it was injected upstream of the rotor. Five operating speeds were investigated of which three with respect to purge flow, namely a high loading case, the peak efficiency, and a high speed case. At each of these operating speeds, the amount of purge flow was varied across a very wide range of ejection rates. Observing the effect of the purge rate on measurement plane averaged parameters, a minor outlet swirl decrease is seen with increasing purge flow for each of the operating speeds while the Mach number is constant. The prominent effect due to purge is seen in the efficiency, showing a similar linear sensitivity to purge for the investigated speeds. An attempt is made to predict the efficiency loss with control volume analysis and entropy production. While spatial average values of swirl and Mach number are essentially unaffected by purge injection, important spanwise variations are observed and highlighted. The secondary flow structure is strengthened in the hub region, leading to a generally increased over-turning and lowered flow velocity. Meanwhile, the added volume flow through the rotor leads to higher outlet flow velocities visible in the tip region, and an associated decreased turning. A radial efficiency distribution is utilized, showing increased impact with increasing rotor speed.

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