FLOW FIELD ANALYSIS OF AN AUTOMOTIVE MIXED FLOW TURBOCHARGER TURBINE

2015 ◽  
Vol 77 (8) ◽  
Author(s):  
M. H. Padzillah ◽  
S. Rajoo ◽  
R. F. Martinez-Botas
Keyword(s):  
Optimum Condition ◽  
Flow Field ◽  
Internal Combustion Engines ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Tip Clearance ◽  
Field Analysis ◽  
Turbine Stage ◽  
Mixed Flow ◽  
Geometrical Properties

Traditionally, the turbocharger has been an essential tool to boost the engine power especially the diesel engine. However, in recent years it is seen as an enabling technology for engine downsizing of all internal combustion engines. The use of mixed flow turbine as replacement for radial turbine in an automotive turbocharger has been proven to deliver better efficiency at high loading conditions. Furthermore, the use vanes that match the geometrical properties at the turbine leading edge could further increase its performance. However, improvement on the overall turbocharger performance is currently limited due to lack of understanding on the flow feature within the turbine stage. Therefore, the use of validated Computational Fluid Dynamics (CFD) in resolving this issue is necessary. This research attempts to provide description of flow field within the turbocharger turbine stage by plotting velocity and pressure contours at different planes. To achieve this aim, a numerical model of a full stage turbocharger turbine operating at 30000rpm under its optimum condition (pressure ratio of 1.3) is developed and validated. Results indicated strong tip-clearance flow downstream of the turbine mid-chord. Evidence of flow separations at the turbine leading edge are also seen despite turbine operating at its optimum condition.

Aerodynamic Design and Optimization of Pipe Diffuser for a High-Loading Centrifugal Compressor

2017 ◽  
Author(s):  
Xi Yang ◽  
Dong-hai Jin ◽  
Xing-min Gui
Keyword(s):  
Flow Field ◽  
Design Method ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Simulation Software ◽  
Field Analysis ◽  
Superior Performance ◽  
Critical Cross Section ◽  
Isentropic Efficiency ◽  
Vane Diffuser

Pipe diffuser draws more attentions these years as the stage pressure ratio and loads grow, since it is known that the pipe diffuser has a superior performance to the traditional vane diffuser as the diffuser inlet flow field is transonic or supersonic. Generally speaking, when the pressure ratio is high enough to give rise to the emergence of a critical cross-section, it would usually be in the diffuser, closing to the leading edge other than in the impeller. Therefore, the diffuser would have a significant impact on stage choke margin and its performance while be difficult to design and to match the impeller with satisfaction. To address the problem, a preliminary geometry design method for pipe diffuser is presented in this paper. In this paper, the performance and flow field analysis are based on numerical simulation carried out by Numeca, a commercial simulation software. For verified the calculated results′ reliability and grid independence, corresponding calculations and comparisons are conducted and discussed. Then, the performance of stage with pipe diffuser is compared with the stage with vane diffuser. Next, the specific effects of incidence on the performance and flow field are analyzed and discussed respectively. At last, an optimized aerodynamic structure of pipe diffuser is presented. As shown in the CFD results, the stage peak isentropic efficiency can reach up to 83.65% with the stage total pressure ratio slightly increased from 6.50 to 6.78, which means 4.29% of isentropic efficiency was raised by substituting the pipe diffuser for the vane diffuser.

Aerodynamic Analysis of an Innovative Low Pressure Vane Placed in a S-Shape Duct

2010 ◽  
Author(s):  
S. Lavagnoli ◽  
T. Yasa ◽  
G. Paniagua ◽  
S. Duni ◽  
L. Castillon
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Pressure Ratio ◽  
Complex Structure ◽  
Leading Edge ◽  
Strong Impact ◽  
Turbine Stage ◽  
Mean Pressure ◽  
Spectrum Distribution ◽  
The One

In this paper the aerodynamics of an innovative multisplitter LP stator downstream of a high-pressure turbine stage is presented. The stator row, located inside a swan necked diffuser, is composed of 16 large structural vanes and 48 small airfoils. The experimental characterization of the steady and unsteady flow field was carried out in a compression tube rig under engine representative conditions. The one-and-a-half turbine stage was tested at three operating regimes by varying the pressure ratio and the rotational speed. Time-averaged and time-accurate surface pressure measurements are used to investigate the aerodynamic performance of the stator and the complex interaction mechanisms with the HP turbine stage. Results show that the strut blade has a strong impact on the steady and unsteady flow field of the small vanes depending on the vane circumferential position. The time-mean pressure distributions around the airfoils show that the strut influence is significant only in the leading edge region. At off-design condition (higher rotor speed) a wide separated region is present on the strut pressure side and it affects the flow field of the adjacent vanes. A complex behavior of the unsteady surface pressures was observed. Up to four pressure peaks are identified in the time-periodic signals. The frequency analysis also shows a complex structure. The spectrum distribution depends on the vane position. The contribution of the harmonics is often larger than the fundamental frequency. The forces acting on the LP stator vanes are calculated. The results show that higher forces act on the small vanes but largest fluctuations are experienced by the strut. The load on the whole stator decreases 30% as the turbine pressure ratio is reduced by approx. 35%.

scholarly journals Aeroloads and Secondary Flows in a Transonic Mixed Flow Turbine Stage

1992 ◽  
Author(s):  
K. R. Kirtley ◽  
T. A. Beach ◽  
Cass Rogo
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Leading Edge ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Design System ◽  
Turbine Stage ◽  
Mixed Flow ◽  
Nozzle Vane ◽  
Highly Loaded

A numerical simulation of a transonic mixed flow turbine stage has been carried out using an average passage Navier-Stokes analysis. The mixed flow turbine stage considered here consists of a transonic nozzle vane and a highly loaded rotor. The simulation was run at the design pressure ratio and is assessed by comparing results with those of an established throughflow design system. The three-dimensional aerodynamic loads are studied as well as the development and migration of secondary flows and their contribution to the total pressure loss. The numerical results indicate that strong passage vortices develop in the nozzle vane, mix out quickly, and have little impact on the rotor flow. The rotor is highly loaded near the leading edge. Within the rotor passage, strong spanwise flows and other secondary flows exist along with the tip leakage vortex. The rotor exit loss distribution is similar in character to that found in radial inflow turbines. The secondary flows and non-uniform work extraction also tend to significantly redistribute a non-uniform inlet total temperature profile by the exit of the stage.

Aeroloads and Secondary Flows in a Transonic Mixed-Flow Turbine Stage

1993 ◽  
Vol 115 (3) ◽  
pp. 590-600 ◽  
Author(s):  
K. R. Kirtley ◽  
T. A. Beach ◽  
C. Rogo
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Leading Edge ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Design System ◽  
Turbine Stage ◽  
Mixed Flow ◽  
Nozzle Vane ◽  
Highly Loaded

A numerical simulation of a transonic mixed-flow turbine stage has been carried out using an average passage Navier–Stokes analysis. The mixed-flow turbine stage considered here consists of a transonic nozzle vane and a highly loaded rotor. The simulation was run at the design pressure ratio and is assessed by comparing results with those of an established throughflow design system. The three-dimensional aerodynamic loads are studied as well as the development and migration of secondary flows and their contribution to the total pressure loss. The numerical results indicate that strong passage vortices develop in the nozzle vane, mix out quickly, and have little impact on the rotor flow. The rotor is highly loaded near the leading edge. Within the rotor passage, strong spanwise flows and other secondary flows exist along with the tip leakage vortex. The rotor exit loss distribution is similar in character to that found in radial inflow turbines. The secondary flows and nonuniform work extraction also tend to redistribute a nonuniform inlet total temperature profile significantly by the exit of the stage.

scholarly journals EFFECT OF TIP CLEARANCE ON THE FLOW FIELD OF THE MIXED FLOW TURBOCHARGER TURBINE

2017 ◽  
Vol 79 (7-3) ◽  
Author(s):  
M. S. Kamarudin ◽  
M. Zulkeflee ◽  
M. H. Padzillah
Keyword(s):  
Flow Field ◽  
Combustion Engine ◽  
Velocity Ratio ◽  
Leading Edge ◽  
Tip Clearance ◽  
Optimum Operating ◽  
Low Velocity ◽  
Mixed Flow ◽  
Optimum Operating Condition ◽  
Design Speed

Turbocharger is a device comprising mainly of a turbine and a compressor. The demand of turbocharger in the automotive industry increases as it significantly enhances the output power of an Internal Combustion Engine and reduces emission. The use of mixed flow turbine to replace the conventional radial turbine gives better impact since the turbine transient response increases and operates more efficiently at low velocity ratio. The flow behaviour inside the turbine affects the torque generation by the turbine. It is necessary for the turbine to have a specified clearance between the rotor tip and the casing of the turbomachine. This undoubtedly will contribute to clearance loss and mixing of leaked flow which produce disturbance to the exhaust flow. In order to investigate this effect, the validated Computational Fluid Dynamics method is chosen in order to replicate the flow field inside the mixed flow turbine. The simulation is carried out at the optimum operating condition which is at turbine total-to-static efficiency of 79% with inlet mass flow rate of 0.5kg/s. The flow inside the passage is plotted into pressure and velocity contours which are compared at 50% (30000rpm) and 80% (48000rpm) of the turbine design speed. The comparison between having 0% (no leakage) and 3% shroud tip clearance are then compared. Through the analysis, it is suggested that clearance leakage and flow separation cause disruption to the desirable uniform flow inside the turbine passage. The presence of Coriolis effect that resists the clearance leakage flow only at near leading edge of the rotor is observed. Furthermore, a low pressure region is perceived at rotor hub which absent in the radial flow turbine. These factors eventually reduce the performances of the actual turbine.

Numerical Investigations on Aerodynamic Design Criteria for Low Speed Mixed Flow Compressor

2021 ◽  
Author(s):  
Hemant Kumar ◽  
Chetan S. Mistry
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Cone Angle ◽  
Tip Clearance ◽  
Working Fluid ◽  
Mixed Flow ◽  
Low Speed ◽  
Flow Compressor

Abstract A surge in the small jet engine market due to aero-propulsion purposes generates a requirement to develop compact and robust high-performance compressors. Mixed flow compressors can provide a comparatively higher pressure ratio compared to axial compressors and have less frontal area than centrifugal compressors. Rapid progress in manufacturing and computational capabilities has resulted in the successful design of mixed flow compressors in recent decades. In the present study, the mixed flow compressor was designed to operate at 3,000 rpm with a small total-to-total pressure ratio of 1.03 and a mass flow rate = 1.98 kg/s to carry at low-speed testing for university-level research. Meanline design for the compressor with air as working fluid was done. The blade geometry was developed using commercial Ansys® Bladegen module. The flow domain mesh was generated by the TurboGrid module. Ansys CFX was used as a solver and post-processing tool for the present numerical study. The present work describes the detailed design procedure, overall performance, and flow field features of a low-speed mixed-flow compressor with the special requirement of axial flow exit. The parametric analysis was carried out on splitter blade placement, wrap angle (10°, 20°, 30°, and 50°), and exit cone angle (30°, 40°, 50°, 60°, and 65°), at constant tip clearance and keeping the other parameters constant to observe their effect on performance and flow structure. The use of splitter blades smoothen the flow structure along both stream-wise and span-wise direction, which minimizes flow the separation issue and thereby helping in extending the overall operating range. Comparing the flow field characteristic and performance of each parametric variable, the optimum range of design values is exhibited. The numerical observation and analysis done on parametric variations in this paper can be used for the design of such a future low-speed mixed flow compressor for different performance expectations and installation requirements.

Influence of different blade numbers on the performance of “saddle zone” in a mixed flow pump

2021 ◽  
pp. 095765092110460
Author(s):  
Leilei Ji ◽  
Wei Li ◽  
Weidong Shi ◽  
Fei Tian ◽  
Shuo Li ◽  
...  
Keyword(s):  
Flow Field ◽  
Leading Edge ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Impeller Blade ◽  
Flow Angle ◽  
Tip Leakage ◽  
Vorticity Transport ◽  
Flow Pump

In order to study the effect of different numbers of impeller blades on the performance of mixed-flow pump “saddle zone”, the external characteristic test and numerical simulation of mixed-flow pumps with three different impeller blade numbers were carried out. Based on high-precision numerical prediction, the internal flow field and tip leakage flow field of mixed flow pump under design conditions and stall conditions are investigated. By studying the vorticity transport in the stall flow field, the specific location of the high loss area inside the mixed flow pump impeller with different numbers of blades is located. The research results show that the increase in the number of impeller blades improve the pump head and efficiency under design conditions. Compared to the 4-blade impeller, the head and efficiency of the 5-blade impeller are increased by 5.4% and 21.9% respectively. However, the increase in the number of blades also leads to the widening of the “saddle area” of the mixed-flow pump, which leads to the early occurrence of stall and increases the instability of the mixed-flow pump. As the mixed-flow pump enters the stall condition, the inlet of the mixed-flow pump has a spiral swirl structure near the end wall for different blade numbers, but the depth and range of the swirling flow are different due to the change in the number of blades. At the same time, the change in the number of blades also makes the flow angle at 75% span change significantly, but the flow angle at 95% span is not much different because the tip leakage flow recirculates at the leading edge. Through the analysis of the vorticity transport results in the impeller with different numbers of blades, it is found that the reasons for the increase in the values of the vorticity transport in the stall condition are mainly impacted by the swirl flow at the impeller inlet, the tip leakage flow at the leading edge and the increased unsteady flow structures.

Time-Averaged and Time-Accurate Aerodynamic Effects of Forward Rotor Cavity Purge Flow for a High-Pressure Turbine: Part I—Analytical and Experimental Comparisons

2012 ◽  
Author(s):  
Brian R. Green ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Flow Path ◽  
Field Analysis ◽  
High Pressure Turbine ◽  
Purge Flow

The effect of rotor purge flow on the unsteady aerodynamics of a high-pressure turbine stage operating at design corrected conditions has been investigated both experimentally and computationally. The experimental configuration consisted of a single-stage high-pressure turbine with a modern film-cooling configuration on the vane airfoil as well as the inner and outer end-wall surfaces. Purge flow was introduced into the cavity located between the high-pressure vane and the high-pressure disk. The high-pressure blades and the downstream low-pressure turbine nozzle row were not cooled. All hardware featured an aerodynamic design typical of a commercial high-pressure ratio turbine, and the flow path geometry was representative of the actual engine hardware. In addition to instrumentation in the main flow path, the stationary and rotating seals of the purge flow cavity were instrumented with high frequency response, flush-mounted pressure transducers and miniature thermocouples to measure flow field parameters above and below the angel wing. Predictions of the time-dependent flow field in the turbine flow path were obtained using FINE/Turbo, a three-dimensional, Reynolds-Averaged Navier-Stokes CFD code that had the capability to perform both steady and unsteady analysis. The steady and unsteady flow fields throughout the turbine were predicted using a three blade-row computational model that incorporated the purge flow cavity between the high-pressure vane and disk. The predictions were performed in an effort to mimic the design process with no adjustment of boundary conditions to better match the experimental data. The time-accurate predictions were generated using the harmonic method. Part I of this paper concentrates on the comparison of the time-averaged and time-accurate predictions with measurements in and around the purge flow cavity. The degree of agreement between the measured and predicted parameters is described in detail, providing confidence in the predictions for flow field analysis that will be provided in Part II.

Effects of Stator Wakes and Spanwise Nonuniform Inlet Conditions on the Rotor Flow of an Axial Turbine Stage

1993 ◽  
Vol 115 (1) ◽  
pp. 128-136 ◽  
Author(s):  
J. Zeschky ◽  
H. E. Gallus
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Hot Wire ◽  
Turbine Stage ◽  
Static Pressure Distribution ◽  
Inlet Conditions ◽  
Experimental Values ◽  
Rotor Flow

Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data include the static pressure distribution on the rotor blade passage surfaces and radial-circumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution. The paper presents the formation of the tip clearance vortex and the passage vortices, which are strongly influenced by the spanwise nonuniform stator outlet flow. Taking the experimental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed.

Influences of Tip Leakage Flows Discharged From Main and Splitter Blades on Flow Field in Transonic Centrifugal Compressor Stage

2018 ◽  
Author(s):  
Masanao Kaneko ◽  
Hoshio Tsujita
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Leading Edge ◽  
Tip Clearance ◽  
Blade Loading ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Transonic Centrifugal Compressor ◽  
Tip Leakage Flows

A transonic centrifugal compressor impeller is generally composed of the main and the splitter blades which are different in chord length. As a result, the tip leakage flows from the main and the splitter blades interact with each other and then complicate the flow field in the compressor. In this study, in order to clarify the individual influences of these leakage flows on the flow field in the transonic centrifugal compressor stage at near-choke to near-stall condition, the flows in the compressor at four conditions prescribed by the presence and the absence of the tip clearances were analyzed numerically. The computed results clarified the following noticeable phenomena. The tip clearance of the main blade induces the tip leakage vortex from the leading edge of the main blade. This vortex decreases the blade loading of the main blade to the negative value by the increase of the flow acceleration along the suction surface of the splitter blade, and consequently induces the tip leakage vortex caused by the negative blade loading of the main blade at any operating points. These phenomena decline the impeller efficiency. On the other hand, the tip clearance of the splitter blade decreases the afore mentioned acceleration by the formation of the tip leakage vortex from the leading edge of the splitter blade and the decrease of the incidence angle for the splitter blade caused by the suction of the flow into the tip clearance. These phenomena reduce the loss generated by the negative blade loading of the main blade and consequently reduce the decline of the impeller efficiency. Moreover, the tip clearances enlarge the flow separation around the diffuser inlet and then decline the diffuser performance independently of the operating points.

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