Preliminary Investigation Into the Effects of a Compressor Rim Purge Flow on OGV/Pre-Diffuser and Combustion System Aerodynamics

2017 ◽  
Author(s):  
A. D. Walker ◽  
B. Koli ◽  
P. A. Beecroft
Keyword(s):  
Guide Vane ◽  
Preliminary Investigation ◽  
Axial Compressor ◽  
Test Facility ◽  
Combustion System ◽  
Guide Vanes ◽  
Mainstream Flow ◽  
Purge Flow ◽  
Inlet Conditions ◽  
The Impact

As aero gas turbine designs strive for ever greater efficiencies the trend is for engine overall pressure ratios to rise. Although this provides greater thermal efficiency it means that cycle temperatures also increase. Traditionally turbines have been the focus of cooling schemes to enable them to survive high temperatures. However, it is envisaged that the compressor delivery air will soon reach temperatures which mean they may require similar cooling strategies to the turbine. One such concept is akin to that of a turbine “rim purge flow” which ensures that hot, mainstream flow does not get ingested into rotor cavities. However, the main gas path in compressors is generally more aerodynamically sensitive than in turbines and introduction of a purge flow may be more penalizing. It is important to understand the impact such a flow may have on the primary gas path flow of a compressor and the downstream combustion system aerodynamics. This paper presents a preliminary investigation into the effects of a purge flow which enters the main gas path immediately upstream of the high pressure compressor outlet guide vane (OGV) row. Initial, simplified, CFD predictions clearly demonstrated the potential of the purge flow to negatively affect the OGV/pre-diffuser and alter the inlet conditions to the combustion system. Consequently, an experimental assessment was carried out using an existing fully annular, isothermal test facility which incorporated a bespoke 1.5 stage axial compressor, engine relevant outlet guide vanes, pre-diffuser and downstream combustor geometry. Using CFD to guide the process the test rig was modified to allow a metered airflow to be introduced upstream of the outlet guide vanes. Importantly the flow was directed up the face of the rotor such that it picked up a representative swirl component prior to injection into the main gas path. The experimental data confirmed the CFD results and importantly demonstrated that the degradation in the combustor inlet flow resulted in an increased combustion system loss. At the proposed purge flow rate, equal to ∼1% of the mainstream flow, these effects were small with the system loss increasing by ∼4%. However, at higher purge flow rates (up to 3%) these effects became notable and the OGV/pre-diffuser flow degraded significantly with a resultant increase in the combustion system loss of ∼13%.

scholarly journals Influence of Purge Flow Swirl at Exit to the High-Pressure Compressor on OGV/Pre-Diffuser and Combustion System Aerodynamics

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
A. Duncan Walker ◽  
Bharat Koli ◽  
Peter A. Beecroft
Keyword(s):  
Guide Vane ◽  
Secondary Flows ◽  
Test Facility ◽  
Combustion System ◽  
Flow Topology ◽  
Guide Vanes ◽  
Flow Swirl ◽  
Purge Flow ◽  
Inlet Conditions ◽  
The Impact

As aero gas turbine designs strive for ever greater efficiencies, the trend is for engine overall pressure ratios to rise. Although this provides greater thermal efficiency, it means that cycle temperatures also increase. One potential solution to managing the increasing temperatures is to employ a cooled cooling air system. In such a system, a purge flow into the main gas path downstream of the compressor will be required to prevent hot gas being ingested into the rotor drive cone cavity. However, the main gas path in compressors is aerodynamically sensitive and it is important to understand, and mitigate, the impact such a flow may have on the compressor outlet guide vanes, pre-diffuser, and the downstream combustion system aerodynamics. Initial computational fluid dynamics (CFD) predictions demonstrated the potential of the purge flow to negatively affect the outlet guide vanes and alter the inlet conditions to the combustion system. The purge flow modified the incidence onto the outlet guide vane, at the hub, such that the secondary flows increased in magnitude. An experimental assessment carried out using an existing fully annular, isothermal test facility confirmed the CFD results and importantly demonstrated that the degradation in the combustor inlet flow resulted in an increased combustion system loss. At the proposed purge flow rate, equal to ∼1% of the mainstream flow, these effects were small with the system loss increasing by ∼4%. However, at higher purge flow rates (up to 3%), these effects became notable and the outlet guide vane and pre-diffuser flow degraded significantly with a resultant increase in the combustion system loss of ∼13%. To mitigate these effects, CFD was used to examine the effect of varying the purge flow swirl fraction in order to better align the flow at the hub of the outlet guide vane. With a swirl fraction of 0.65 (x rotor speed), the secondary flows were reduced below that of the datum case (with no purge flow). Experimental data showed good agreement with the predicted flow topology and performance trends but the measured data showed smaller absolute changes. Differences in system loss were measured with savings of around 10% at the turbine feed ports for a mass flow ratio of 1% and a swirl fraction of 0.65.

An Advanced Single-Stage Turbine Facility for Investigating Non-Axisymmetric Contoured Endwalls in the Presence of Purge Flow

2019 ◽  
Author(s):  
Robin R. Jones ◽  
Oliver J. Pountney ◽  
Bjorn L. Cleton ◽  
Liam E. Wood ◽  
B. Deneys J. Schreiner ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Static Pressure ◽  
Optical Measurement ◽  
Guide Vane ◽  
Single Stage ◽  
Test Facility ◽  
Pressure Distributions ◽  
Mainstream Flow ◽  
Purge Flow ◽  
Nozzle Guide

Abstract In modern gas turbines, endwall contouring (EWC) is employed to modify the static pressure field downstream of the vanes and minimise the growth of secondary flow structures developed in the blade passage. Purge flow (or egress) from the upstream rim-seal interferes with the mainstream flow, adding to the loss generated in the rotor. Despite this, EWC is typically designed without consideration of mainstream-egress interactions. The performance gains offered by EWC can be reduced, or in the limit eliminated, when purge air is considered. In addition, EWC can result in a reduction in sealing effectiveness across the rim seal. Consequently, industry is pursuing a combined design approach that encompasses the rim-seal, seal-clearance profile and EWC on the rotor endwall. This paper presents the design of, and preliminary results from a new single-stage axial turbine facility developed to investigate the fundamental fluid dynamics of egress-mainstream flow interactions. To the authors’ knowledge this is the only test facility in the world capable of investigating the interaction effects between cavity flows, rim seals and EWC. The design of optical measurement capabilities for future studies, employing volumetric velocimetry and planar laser induced fluorescence are also presented. The fluid-dynamically scaled rig operates at benign pressures and temperatures suited to these techniques and is modular. The facility enables expedient interchange of EWC (integrated into the rotor bling), blade-fillet and rim-seals geometries. The measurements presented in this paper include: gas concentration effectiveness and swirl measurements on the stator wall and in the wheel-space core; pressure distributions around the nozzle guide vanes at three different spanwise locations; pitchwise static pressure distributions downstream of the nozzle guide vane at four axial locations on the stator platform.

Impact of a Cooled Cooling Air Installation on the External Aerodynamics of a Gas Turbine Combustion System

2015 ◽  
Author(s):  
A. D. Walker ◽  
L. Guo
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Leading Edge ◽  
Outer Wall ◽  
Area Ratio ◽  
Test Facility ◽  
Combustion System ◽  
External Aerodynamics ◽  
Cooling Air ◽  
The Impact

The trend for higher overall pressure ratios means that turbine entry temperatures are continually increasing. Furthermore, the development of lean, low-emission combustion systems reduces the availability of cooling air and is accompanied by new problems at the combustor/turbine interface. For example, the exit temperature traverse differs from that found in traditional rich-burn combustors with increased swirl and a much flatter profile. Effectively cooling the turbine components is becoming increasingly difficult. One solution is to employ cooled cooling air (CCA) where some of the compressor efflux is diverted for additional cooling in a heat exchanger located in the by-pass duct. An example CCA system is presented which includes an off-take within the dump cavity and the addition of radial struts within the pre-diffuser through which the cooled air is returned to the engine core. This paper addresses the impact this CCA system has on the combustion system external aerodynamics. This included the development of a fully annular, isothermal test facility which incorporated a bespoke 1.5 stage axial compressor, engine relevant outlet guide vanes, pre-diffuser and combustor geometry. A datum aerodynamic performance was established for a non-CCA configuration with a clean, un-strutted pre-diffuser. Results for this baseline CCA system demonstrated that inclusion of a bleed in the dump cavity had limited effect on the overall flow field. However, the inclusion of struts within the pre-diffuser caused a reduction in area ratio and a notable increase in system loss. Consequently an alternative pre-diffuser was designed (using CFD) with the aim of increasing the area ratio back to that of the un-strutted datum. A so-called hybrid diffuser was designed in which the CCA bleed was moved to the pre-diffuser outer wall. The bleed was then used to re-energize the boundary layer, preventing flow separation, enabling the area ratio to be increased close to the datum value. The mechanisms of the hybrid diffuser are complex; the geometry of the off-take and its location with respect to the OGV and strut leading edge were seen to be critical. Experimental evaluation of the final design demonstrated the effective operation the hybrid diffuser with the result that the system loss returned to a level close to that of the datum. Only small differences were seen in the overall flow field.

Experimental Investigations and Numerical Validation of an Outlet Guide Vane With an Engine Mount Recess

2008 ◽  
Author(s):  
Johan Hja¨rne ◽  
Valery Chernoray ◽  
Jonas Larsson
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Test Facility ◽  
Experimental Investigations ◽  
Flow Angle ◽  
Sst Model ◽  
Engine Mount ◽  
Inlet Conditions ◽  
Secondary Flow Field

This paper presents experiments and CFD calculations of a Low Pressure Turbine/Outlet Guide Vane (LPT/OGV) equipped with an engine mount recess (a bump) tested in the Chalmers linear LPT/OGV cascade. The investigated characteristics include performance for the design point in terms of total pressure loss and turning as well as a detailed description of the downstream development of the secondary flow field. The numerical simulations are performed for the same inlet conditions as in the test-facility with engine-like properties in terms of Reynolds number, boundary-layer thickness and inlet flow angle. The objective is to validate how accurately and reliably the secondary flow field and losses can be predicted for an LPT/OGV equipped with a bump. Three different turbulent models as implemented in FLUENT, the k-ε realizable model, the kω-SST model and the RSM are validated against detailed measurements. From these results it can be concluded that the kω-SST model predicts both the secondary flow field and the losses most accurately.

Wet Gas Impeller Test Facility

2010 ◽  
Author(s):  
Trond G. Gru¨ner ◽  
Lars E. Bakken
Keyword(s):  
Oil And Gas ◽  
Fluid Dynamic ◽  
Open Loop ◽  
Gas Production ◽  
Test Facility ◽  
Atmospheric Conditions ◽  
Oil And Gas Production ◽  
Wet Gas ◽  
Inlet Conditions ◽  
The Impact

The development of wet gas compressors will enable increased oil and gas production rates and enhanced profitable operation by subsea well-stream boosting. A more fundamental knowledge of the impact of liquid is essential with regard to the understanding of thermodynamic and fluid dynamic compressor behavior. An open-loop impeller test facility was designed to investigate the wet gas performance, aerodynamic stability, and operation range. The facility was made adaptable for different impeller and diffuser geometries. In this paper, the wet gas test facility and experimental work concerning the impact of wet gas on a representative full-scale industrial impeller are presented. The centrifugal compressor performance was examined at high gas volume fractions and atmospheric inlet conditions. Air and water were used as experimental fluids. Dry and wet gas performance was experimentally verified and analyzed. The results were in accordance with previous test data and indicated a stringent influence of the liquid phase. Air/water tests at atmospheric conditions were capable of reproducing the general performance trend of hydrocarbon wet gas compressor tests at high pressure.

Effect of blade tip grooving on the performance of an axial fan at different tip clearances in the absence and presence of inlet guide vanes

2019 ◽  
Vol 234 (1) ◽  
pp. 72-84
Author(s):  
Masoud Kharati-Koopaee ◽  
Hossein Moallemi
Keyword(s):  
Numerical Study ◽  
Guide Vane ◽  
Pressure Coefficient ◽  
Tip Clearance ◽  
Axial Fan ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Blade Tip ◽  
Torque Coefficient ◽  
The Impact

This research aims at the numerical study of the blade tip grooving effect on the performance of a ducted axial fan at different tip clearances in the absence and presence of inlet guide vanes. To do this, significant parameters of the fan (i.e. pressure and torque coefficients as well as fan efficiency) comprising single- and double-grooved tips are evaluated and compared with those of the original fan. Validation of the considered numerical model is performed through comparison of the numerical findings with experimental results of a single-stage ducted fan, which comprises a set of 37 guide vane and 24-blade rotor rotating at the speed of 3600 r/min. Results reveal that grooving the blade tip causes the fan parameters to increase and higher fan parameters could be attained adopting single-grooved tip. It is shown that employing grooved blades causes the sensitivity of fan parameters to the change in the tip clearance to diminish. Results exhibit that the impact of grooving the blade on the reduction of sensitivity of fan parameters to the change in the tip clearance for the single-grooved tip in the absence of guide vanes is more remarkable than the other cases and in this case, as the tip clearance increases from the lower to the upper considered value, the decreased percentages in pressure coefficient, torque coefficient, and fan efficiency are 29.8%, 8.9%, and 22.8%, respectively. Numerical findings show that the influence of grooving the blade on the fan parameters in the presence of guide vanes is lower than that without guide vanes and in the presence of guide vanes, the highest average increase percentages in pressure coefficient, torque coefficient, and fan efficiency relative to those of the original fan, which is observed in the single grooved tip, are 3.1%, 1.4%, and 1.7%, respectively.

Variable Inlet Guide Vane Losses and Their Effect on Downstream Impeller and Diffuser in Wet Gas Flow

2017 ◽  
Author(s):  
Levi André B. Vigdal ◽  
Lars E. Bakken
Keyword(s):  
Gas Flow ◽  
Oil And Gas ◽  
Guide Vane ◽  
Gas Production ◽  
Test Facility ◽  
Innovative Technology ◽  
Inlet Guide Vane ◽  
Oil And Gas Production ◽  
Wet Gas ◽  
The Impact

Adopting the innovative technology found in a compressor able to compress a mixture of natural gas and condensate has great potential for meeting future challenges in subsea oil and gas production. Benefits include reduced size, complexity and cost, enhanced well output, longer producing life and increased profits, which in turn offer opportunities for exploiting smaller oil and gas discoveries or extending the commercial life of existing fields. Introducing liquid into a centrifugal compressor creates several thermodynamic and fluid-mechanical challenges. The paper reviews some of the drive mechanisms involved in wet gas compression and views them in the context of the test results presented. An inlet guide vane (IGV) assembly has been installed in a test facility for wet gas compressors and the effect of wet gas on IGV performance documented. The impact of changes in IGV performance on impeller and diffuser has also been documented. The results have been discussed and correction methods compared.

Effect of Simulated Combustor Temperature Nonuniformity on HP Vane and Endwall Heat Transfer: An Experimental and Computational Investigation

2010 ◽  
Author(s):  
Imran Qureshi ◽  
Arrigo Beretta ◽  
Thomas Povey
Keyword(s):  
Heat Transfer ◽  
Guide Vane ◽  
Research Programme ◽  
Test Facility ◽  
Inlet Temperature ◽  
Computational Investigation ◽  
Nozzle Guide Vane ◽  
Inlet Conditions ◽  
Nozzle Guide ◽  
Computational Predictions

This paper presents experimental measurements and computational predictions of surface and endwall heat transfer for a high-pressure (HP) nozzle guide vane (NGV) operating as part of a full HP turbine stage in an annular rotating turbine facility, with and without inlet temperature distortion (hot-streaks). A detailed aerodynamic survey of the vane surface is also presented. The test turbine was the unshrouded MT1 turbine, installed in the Turbine Test Facility (previously called Isentropic Light Piston Facility) at QinetiQ, Farnborough UK. This is a short duration facility, which simulates engine representative M, Re, non-dimensional speed and gas-to-wall temperature ratio at the turbine inlet. The facility has recently been upgraded to incorporate an advanced second-generation combustor simulator, capable of simulating well-defined, aggressive temperature profiles in both the radial and circumferential directions. This work forms part of the pan-European research programme, TATEF II. Measurements of HP vane and endwall heat transfer obtained with inlet temperature distortion are compared with results for uniform inlet conditions. Steady and unsteady CFD predictions have also been conducted on vane and endwall surfaces, using the Rolls-Royce CFD code HYDRA to complement the analysis of experimental results. The heat transfer measurements presented in this paper are the first of their kind in the respect that the temperature distortion is representative of an extreme cycle point measured in the engine situation, and was simulated with good periodicity and with well defined boundary conditions in the test turbine.

Numerical Study on the Effect of Seal Leakage Flow on Low Pressure Axial Compressor Performance

2013 ◽  
Author(s):  
Balazs Farkas ◽  
Nicolas Van de Wyer ◽  
Jean-Francois Brouckaert
Keyword(s):  
Numerical Study ◽  
Axial Compressor ◽  
Test Facility ◽  
Leakage Flow ◽  
Stability Range ◽  
Compressor Rotor ◽  
Numerical Predictions ◽  
Aero Engines ◽  
The Stability ◽  
The Impact

This paper presents the extended numerical studies of a one and a half stage axial compressor designed for the LP compressor of a contra-rotating fan engine architecture. The essence of this architecture is given by the fact that the LP compressor rotor is mounted on the same shaft as the second fan stage which results in a lower rotational speed and therefore a much higher loading than in conventional high bypass-ratio aero-engines. The compressor itself was designed at VKI and subsequently tested in the closed loop test facility (VKI-R4) which allowed to compare numerical predictions with experimental data. In this study, particular interest was given to investigate the effect of the seal-leakage flow around the stator hub platform on the performance. To study the effect of the seal-leakage flow three different seal cavity configurations with different seal-tooth gaps sizes were simulated in comparison with no-cavity configuration. This set of investigations allowed to assess the different models by comparison with the results obtained experimentally. This comparison was made on the global performance of the stage, including the impact on the stability range, as well as on the flow field itself in particular in the rotor and stator exit planes. The computations were performed by using the Numeca developed code FINE™/Turbo with steady RANS solver.

scholarly journals Unsteady phenomena at the combustor-turbine interface

2021 ◽  
Vol 5 ◽  
pp. 202-215
Author(s):  
Faisal Shaikh ◽  
Budimir Rosic
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
High Speed ◽  
Guide Vane ◽  
Secondary Flows ◽  
Test Facility ◽  
Unsteady Heat Transfer ◽  
Guide Vanes ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

The combustor-turbine interface in a gas turbine is characterised by complex, highly unsteady flows. In a combined experimental and large eddy simulation (LES) study including realistic combustor geometry, the standard model of secondary flows in the nozzle guide vanes (NGV) is found to be oversimplified. A swirl core is created in the combustion chamber which convects into the first vane passages. Four main consequences of this are identified: variation in vane loading; unsteady heat transfer on vane surfaces; unsteadiness at the leading edge horseshoe vortex, and variation in the position of the passage vortex. These phenomena occur at relatively low frequencies, from 50–300 Hz. It seems likely that these unsteady phenomena result in non-optimal film cooling, and that by reducing unsteadiness designs with greater cooling efficiency could be achieved. Measurements were performed in a high speed test facility modelling a large industrial gas turbine with can combustors, including nozzle guide vanes and combustion chambers. Vane surfaces and endwalls of a nozzle guide vane were instrumented with 384 high speed thin film heat flux gauges, to measure unsteady heat transfer. The high resolution of measurements was such to allow direct visualisation in time of large scale turbulent structures over the endwalls and vane surfaces. A matching LES simulation was carried out in a domain matching experimental conditions including upstream swirl generators and transition duct. Data reduction allowed time-varying LES data to be recorded for several cycles of the unsteady phenomena observed. The combination of LES and experimental data allows physical explanation and visualisation of flow events.

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