Numerical Investigations on the Aerodynamic Performance and Endwall Cooling Characteristics of Turbine During Acceleration Process With Lagging Effects

2021 ◽  
Author(s):  
Qingfeng Cong ◽  
Zhigang Li ◽  
Jun Li
Keyword(s):  
Flow Field ◽  
Rotational Speed ◽  
Aerodynamic Performance ◽  
Acceleration Process ◽  
Two Stage ◽  
Cooling Effectiveness ◽  
Mainstream Flow ◽  
Purge Flow ◽  
Secondary Air ◽  
Endwall Cooling

Abstract In the process of turbine acceleration, due to the influence of compressor and complex secondary air system, the change process of coolant purge flow is relatively lagging behind that of mainstream flow and rotational speed. The lagging egress of coolant flow influence the aerodynamic performance and endwall cooling effectiveness of turbine acceleration process. The flow field and aerothermal performance of two-stage axial turbines combined with rim seal structures and coolant purge flow lagging effects in the turbine acceleration process was numerically investigated using Unsteady Reynolds-Averaged Navier-Stokes (URANS) via SST turbulence model. The effects of lagging coolant purge flow across the rim seal on the turbine aerodynamics and endwall cooling effectiveness were analyzed. The obtained results show that the turbine aerodynamic efficiency obtains the maximum value when the coolant purge flow lagging time equals to half the acceleration time at the same rotational speed after the end of lagging times. The total-to-total efficiency for the second stage is more sensitive to lagging times. The turbine output power is almost un-changed due to combination of additional work capacity and aerodynamic loss with the introduction of coolant. The turbine endwalls have the maximum averaged cooling effectiveness in the turbine acceleration process without consideration of the coolant purge flow lagging time. And endwall cooling effectiveness decreases with the increase of coolant purge flow lagging time at the same rotational speed and mainstream flow conditions. The detailed flow field of two-stage turbine considering interaction between the coolant purge flow and mainstream was also discussed. The present work provides the reference for the match design between the turbine mainstream flow and secondary air flow system.

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.

Unsteady Turbine Rim Sealing and Vane Trailing Edge Flow Effects

2021 ◽  
Author(s):  
Iván Monge-Concepción ◽  
Shawn Siroka ◽  
Reid A. Berdanier ◽  
Michael D. Barringer ◽  
Karen A. Thole ◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotational Speed ◽  
Large Scale ◽  
Trailing Edge ◽  
Time Resolved ◽  
Flow Rates ◽  
Large Scale Structures ◽  
Purge Flow ◽  
Scale Structures

Abstract Hot gas ingestion into the turbine rim seal cavity is an important concern for engine designers. To prevent ingestion, rim seals use high pressure purge flow but excessive use of the purge flow decreases engine thermal efficiency. A single stage test turbine operating at engine-relevant conditions with real engine hardware was used to study time-resolved pressures in the rim seal cavity across a range of sealing purge flow rates. Vane trailing edge (VTE) flow, shown previously to be ingested into the rim seal cavity, was also included to understand its effect on the unsteady flow field. Measurements from high-frequency response pressure sensors in the rim seal and vane platform were used to determine rotational speed and quantity of large-scale structures (cells). In a parallel effort, a computational model using Unsteady Reynolds-averaged Navier-Stokes (URANS) was applied to determine swirl ratio in the rim seal cavity and time-resolved rim sealing effectiveness. The experimental results confirm that at low purge flow rates, the VTE flow influences the unsteady flow field by decreasing pressure unsteadiness in the rim seal cavity. Results show an increase in purge flow increases the number of unsteady large-scale structures in the rim seal and decreases their rotational speed. However, VTE flow was shown to not significantly change the cell speed and count in the rim seal. Simulations point to the importance of the large-scale cell structures in influencing rim sealing unsteadiness, which is not captured in current rim sealing predictive models.

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

2002 ◽  
Author(s):  
S. Girgis ◽  
E. Vlasic ◽  
J.-P. Lavoie ◽  
S. H. Moustapha
Keyword(s):  
Turbine Stage ◽  
Cfd Simulations ◽  
Secondary Air Injection ◽  
Flow Test ◽  
Mainstream Flow ◽  
Purge Flow ◽  
Simulated Test ◽  
Transonic Turbine ◽  
Secondary Air ◽  
Stage Efficiency

This paper presents results of rig testing of a transonic, single stage turbine with various modifications made to the injection of secondary air into the mainstream. Results show that significant improvements in stage efficiency can be realized by optimizing the injection of upstream disk purge and rotor upstream shroud leakage flow into the mainstream flow. Results of CFD simulations of the rotor upstream disk purge flow test conditions and closely simulated test geometry agree well with test data.

Influence of Coolant Density on Turbine Blade Platform Film-Cooling

2012 ◽  
Vol 4 (2) ◽  
Author(s):  
Diganta P. Narzary ◽  
Kuo-Chun Liu ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Flow Rate ◽  
Turbulence Intensity ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Mainstream Flow ◽  
Purge Flow

Detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform of a five-blade linear cascade. The parameters chosen were freestream turbulence intensity, upstream stator-rotor purge flow rate, discrete-hole film-cooling blowing ratio, and coolant-to-mainstream density ratio. The measurement technique adopted was temperature sensitive paint (TSP) technique. Two turbulence intensities of 4.2% and 10.5%; three purge flows between the range of 0.25% and 0.75% of mainstream flow rate; three blowing ratios between 1.0 and 1.8; and three density ratios between 1.1 and 2.2 were investigated. Purge flow was supplied via a typical double-toothed stator-rotor seal, whereas the discrete-hole film-cooling was accomplished via two rows of cylindrical holes arranged along the length of the platform. The inlet and the exit Mach numbers were 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 7.5 * 105 based on the exit velocity and chord length of the blade. Results indicated that platform film-cooling effectiveness decreased with turbulence intensity, increased with purge flow rate and density ratio, and possessed an optimum blowing ratio value.

Effect of Upstream Wake With Vortex on Turbine Blade Platform Film Cooling With Simulated Stator-Rotor Purge Flow

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Lesley M. Wright ◽  
Sarah A. Blake ◽  
Dong-Ho Rhee ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Labyrinth Seal ◽  
Delta Wings ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Passage Vortex ◽  
Mainstream Flow ◽  
Purge Flow

Detailed film cooling effectiveness distributions were experimentally obtained on a turbine blade platform within a linear cascade. The film cooling effectiveness distributions were obtained on the platform with upstream disturbances used to simulate the passing vanes. Cylindrical rods, placed upstream of the blades, simulated the wake created by the trailing edge of the stator vanes. The rods were placed at four locations to show how the film cooling effectiveness was affected relative to the vane location. In addition, delta wings were placed upstream of the blades to model the effect of the passage vortex (generated in the vane passage) on the platform film cooling effectiveness. The delta wings create a vortex similar to the passage vortex as it exits the upstream vane passage. The film cooling effectiveness was measured with the delta wings placed at four location, to investigate the effect of the passing vanes. Finally, the delta wings were coupled with the cylindrical rods to examine the combined effect of the upstream wake and passage vortex on the platform film cooling effectiveness. The detailed film cooling effectiveness distributions were obtained using pressure sensitive paint in the five blade linear cascade. An advanced labyrinth seal was placed upstream of the blades to simulate purge flow from a stator-rotor seal. The coolant flow rate varied from 0.5% to 2.0% of the mainstream flow, while the Reynolds number of the mainstream flow remained constant at 3.1×105 (based on the inlet velocity and chord length of the blade). The film cooling effectiveness was not significantly affected with the upstream rod. However, the vortex generated by the delta wings had a profound impact on the film cooling effectiveness. The vortex created more turbulent mixing within the blade passage, and the result is reduced film cooling effectiveness through the entire passage. When the vane induced secondary flow is included, the need for additional platform cooling becomes very obvious.

Upstream Vortex Effects on Turbine Blade Platform Film Cooling With Typical Stator-Rotor Purge Flow

2007 ◽  
Author(s):  
Zhihong Gao ◽  
Diganta Narzary ◽  
Shantanu Mhetras ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Delta Wing ◽  
Delta Wings ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pressure Sensitive ◽  
Passage Vortex ◽  
Mainstream Flow ◽  
Purge Flow

Detailed film cooling effectiveness distributions were experimentally obtained on a turbine blade platform within a five-blade linear cascade. A typical labyrinth-like seal was placed upstream of the cascade blades to simulate purge flow from a stator-rotor gap. Delta wings were periodically placed upstream of the blades to model the effect of the passage vortex generated in the vane passage on the downstream blade platform film cooling effectiveness. Typical vane passage vortex was simulated by two delta wings with height of 10% and 20% of the blade span, respectively. The strength of vane passage vortex was also modeled by varying the attack angle of mainstream to the delta wing. The film cooling effectiveness was measured with the delta wings placed at four phase locations, to investigate the effect of the passing vanes. The detailed film cooling effectiveness distributions on the platform were obtained using pressure sensitive paint (PSP) technique. The coolant mass flow rate varied from 0.25% to 1.0% of the mainstream flow. The freestream Reynolds number, based on the axial chord length and the exit velocity, was 750,000. The Mach numbers at the inlet and the exit were 0.27 and 0.44, respectively. The vortex generated by the delta wings had a profound impact on the platform film cooling effectiveness. The upstream vortex created more turbulent mixing within the blade passage and resulted in reduced film cooling effectiveness on the blade platform.

Effect of Upstream Wake With Vortex on Turbine Blade Platform Film Cooling With Simulated Stator-Rotor Purge Flow

2007 ◽  
Author(s):  
Lesley M. Wright ◽  
Sarah A. Blake ◽  
Dong-Ho Rhee ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Labyrinth Seal ◽  
Delta Wings ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Passage Vortex ◽  
Mainstream Flow ◽  
Purge Flow

Detailed film cooling effectiveness distributions were experimentally obtained on a turbine blade platform within a linear cascade. The film cooling effectiveness distributions were obtained on the platform with upstream disturbances used to simulate the passing vanes. Cylindrical rods, placed upstream of the blades, simulated the wake created by the trailing edge of the stator vanes. The rods were placed at 4 locations to show how the film cooling effectiveness was affected relative to the vane location. In addition, delta wings were placed upstream of the blades to model the effect of the passage vortex (generated in the vane passage) on the platform film cooling effectiveness. The delta wings create a vortex similar to the passage vortex as it exits the upstream vane passage. The film cooling effectiveness was measured with the delta wings placed at 4 locations, to investigate the effect of the passing vanes. Finally, the delta wings were coupled with the cylindrical rods to examine the combined effect of the upstream wake and passage vortex on the platform film cooling effectiveness. The detailed film cooling effectiveness distributions were obtained using pressure sensitive paint (PSP) in the five blade linear cascade. An advanced labyrinth seal was placed upstream of the blades to simulate purge flow from a statorrotor seal. The coolant flow rate varied from 0.5% to 2.0% of the mainstream flow, while the Reynolds number of the mainstream flow remained constant at 3.1*105 (based on the inlet velocity and chord length of the blade). The film cooling effectiveness was not significantly affected with the upstream rod. However, the vortex generated by the delta wings had a profound impact on the film cooling effectiveness. The vortex created more turbulent mixing within the blade passage, and the result is reduced film cooling effectiveness through the entire passage. When the vane induced secondary flow is included, the need for additional platform cooling becomes very obvious.

Film Cooling Effectiveness Distributions on a Turbine Blade Cascade Platform With Stator-Rotor Purge and Discrete Film Hole Flows

2006 ◽  
Author(s):  
Lesley M. Wright ◽  
Sarah A. Blake ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Flow Rate ◽  
Film Cooling ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Wide Range ◽  
Mainstream Flow ◽  
Purge Flow

An experimental investigation has been completed to obtain detailed film cooling effectiveness distributions on a cooled turbine blade platform within a linear cascade. The platform has a labyrinth-like seal upstream of the blades to model a realistic stator-rotor seal configuration. Additional coolant is supplied to the downstream half of the platform via discrete film cooling holes. The coolant flow rate through the upstream seal varies from 0.5% to 2.0% of the mainstream flow, while the blowing ratio of the coolant through the discrete holes varies from 0.5 to 2.0 (based on the mainstream velocity at the exit of the cascade). Detailed film cooling effectiveness distributions are obtained using the pressure sensitive paint (PSP) technique under a wide range of coolant flow conditions and various freestream turbulence levels (0.75% or 13.4%). The PSP technique clearly shows how adversely the coolant is affected by the passage induced flow. With only purge flow from the upstream seal, the coolant flow rate must exceed 1.5% of the mainstream flow in order to adequately cover the entire passage. However, if discrete film holes are used on the downstream half of the passage, the platform can be protected while using less coolant (i.e. the seal flow rate can be reduced).

Influence of Disc Spacing Distance on the Aerodynamic Performance and Flow Field of Tesla Turbines

2016 ◽  
Author(s):  
Wenjiao Qi ◽  
Qinghua Deng ◽  
Zhenping Feng ◽  
Qi Yuan
Keyword(s):  
Flow Field ◽  
Rotational Speed ◽  
Tangential Velocity ◽  
Aerodynamic Performance ◽  
Velocity Difference ◽  
Ekman Number ◽  
Optimal Value ◽  
Spacing Distance ◽  
Optimal Values

This paper aims at proposing a feasible method to determine an appropriate disc spacing distance in the design of Tesla turbines. Therefore, a typical Tesla turbine with seven different disc spacing distances was calculated numerically at different rotational speeds to investigate the influence of disc spacing distance on the aerodynamic performance and flow field of Tesla turbines and further to put forward the method. The results show that the isentropic efficiency of Tesla turbines peaks when the disc spacing distance gets its optimal value, and it decreases quickly as the disc spacing distance decreases from its optimal value. What’s more, the dimensionless parameter Ekman number is applied to determine an appropriate disc spacing distance in the design of Tesla turbines. There’s an optimal value of the Ekman number that Tesla turbines obtain its best performance, and it is influenced by the rotational speed. Meanwhile, the optimal value of the dimensionless rotor inlet tangential velocity difference which decides the rotational speed is also affected by the disc spacing distance. Thus, the determination of the optimal values of the dimensionless rotor inlet tangential velocity difference and the Ekman number is a cyclic iterative process to make them at their optimal values or in their optimal ranges respectively.

Influence of Purge Temperature Variation on the Performance of Turbine Center Frames

2020 ◽  
Author(s):  
Patrick Jagerhofer ◽  
Andreas Peters ◽  
Emil Göttlich ◽  
Wolfgang Sanz ◽  
Federica Farisco
Keyword(s):  
Flow Field ◽  
Engine Performance ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Navier Stokes ◽  
Flow Temperature ◽  
Reference Case ◽  
Turbofan Engines ◽  
Purge Flow ◽  
Aero Engines

Abstract High-bypass ratio turbofan engines are commonly employed in aircrafts. Their usage is essential to guarantee low specific fuel consumption, reduced CO2 emissions and low noise levels. Such modern aero-engines benefit from high efficiencies by operating at turbine inlet temperatures in excess of the melting point of the turbine components. To enable this, compressor air is supplied to the turbine for cooling and purging purposes. The re-introduction of the cooling air back into the mainstream flow is known to alter the flow field and to affect the aerodynamic performance of the turbine components. A component especially susceptible to the interaction between the mainstream and purge flow is the Turbine Center Frame, located between high-pressure turbine (HP) and low-pressure (LP) turbine. For ever higher bypass ratios, this turbine transition ducts need to be designed with axial lengths as short as possible and larger radial offsets to avoid engine weight penalties while at the same time maintaining aerodynamic performance. More detailed experience in the field of intermediate turbine ducts is needed to identify further opportunities to improve turbofan engine performance, including an in-depth understanding of the interaction between mainstream and purge flows. This paper presents a Computational Fluid Dynamics (CFD) study of the effect of the purge flow temperature, and hence density, on the aerodynamic performance of an engine representative Turbine Center Frame (TCF). Several steady-state Reynolds-averaged Navier–Stokes (RANS) simulations were conducted for varying purge flow temperatures using an in-house code called LINARS. Time-averaged five-hole-probe measurements acquired in the Transonic Test Turbine Facility (TTTF) at Graz University of Technology were used as inlet boundary conditions to impose an engine-relevant flow field. The results obtained from two reduced and two increased purge flow temperature conditions were compared to a reference case. The reference case results showed agreement with static wall pressure measurements, hence validating the simulation. Changing the purge flow temperature significantly affected the main flow locally as well as overall. The position and size of vortices in the TCF were changed under the presence of hotter or cooler purge flows. Additionally, a flow separation on the outer duct wall observed in the baseline case was suppressed in the cold-purged flow case. The cold-purged TCF showed a 28.8% lower total pressure loss than the hot-purged one. This indicates that a more aggressive TCF design may be feasible in a cold-purged operation.

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