EXPERIMENTAL AND NUMERICAL INVESTIGATION ON FLOW ANGLE CHARACTERISTICS OF AN AUTOMOTIVE MIXED FLOW TURBOCHARGER TURBINE

2015 ◽  
Vol 77 (8) ◽  
Author(s):  
M. H. Padzillah ◽  
S. Rajoo ◽  
R. F. Martinez-Botas
Keyword(s):  
Flow Field ◽  
Combustion Engine ◽  
Leading Edge ◽  
Full Description ◽  
Complex Nature ◽  
Spanwise Direction ◽  
Angle Distribution ◽  
Turbine Stage ◽  
Flow Angle ◽  
Highly Efficient

To date, turbocharger remains as a key enabler towards highly efficient Internal Combustion Engine. Although the first turbocharger was patented more than 30 years ago, the design is still being improved, thus signifying its importance in modern vehicles. One of the key features that contribute to the challenges in designing highly efficient turbine is the complex nature of the flow field within the turbine stage itself. Experimental method could be used to extract parameters such as pressure and temperature traces but still unable to provide a full description of the flow field. Therefore, the use of Computational Fluid Dynamics (CFD) in resolving this issue is necessary. Out of many feature of fluid flow in turbomachinery, the flow angle at rotor inlet plays significant role in determining turbine efficiency. However, due to geometrical complexity, even at optimum averaged incidence flow angle, there still exist variations that could impair the turbine ability to produce work. This research attempts to provide insight on the complexity of flow angle distribution within the turbocharger turbine stage. To achieve this aim, a numerical model of a full stage turbocharger turbine operating at 30000rpm under its optimum condition was developed. Results indicated that even though use of guide vanes has reduced flow angle fluctuations at mid-span of the rotor inlet from ±10° to only ±1°, significant variations still exist for velocity components in spanwise direction. This in turns effected the distribution of incidence flow angle at the rotor leading edge. In the current research, variation of incidence flow angle in spanwise direction is recorded to be as high as 60°.

A Numerical Study of Secondary Flow in Axial Turbines With Application to Radial Transport of Hot Streaks

2000 ◽  
Author(s):  
Dilip Prasad ◽  
Gavin J. Hendricks
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Study ◽  
Angle Distribution ◽  
Turbine Stage ◽  
Radial Transport ◽  
Numerical Work ◽  
Flow Angle ◽  
Axial Turbines ◽  
Hot Streak

The flow field in a low-speed turbine stage with a uniform inlet total pressure is studied numerically. A circular hot streak is superposed on the vane inlet flow. In agreement with previous experimental and numerical work, it is observed that while the streak passes through the vane unaltered, significant radial transport occurs in the rotor. Furthermore, despite the unsteady nature of the flow field, the steady theory of Hawthorne (1974) is found to predict the radial transport velocity well. Making use of this theory, it is shown that the secondary vorticity in the rotor may be attributed to the effects of density stratification, the spatial variation of the vane exit flow angle and the relative eddy. It then follows that the extent of radial transport in the rotor may be influenced by altering the vane exit flow angle distribution. The present study examines one means by which this may be effected, viz., varying the vane twist across the span. It is shown that a “reverse” twist, wherein the flow angle at the vane exit is larger near the tip than it is at mid-span reduces the secondary flow (and consequently, radial transport) in the blade passage. On the other hand, “positive” twist, in which the vane exit flow angle decreases with span is found to markedly worsen the radial transport in the blade. It is to be noted that varying the vane twist is but one method to obtain the desired exit flow angle; possibilities for altering other aspects of the vane geometry also exist.

A Numerical Study of Secondary Flow in Axial Turbines With Application to Radial Transport of Hot Streaks

2000 ◽  
Vol 122 (4) ◽  
pp. 667-673 ◽  
Author(s):  
Dilip Prasad ◽  
Gavin J. Hendricks
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Study ◽  
Angle Distribution ◽  
Turbine Stage ◽  
Radial Transport ◽  
Numerical Work ◽  
Flow Angle ◽  
Axial Turbines ◽  
Hot Streak

The flow field in a low-speed turbine stage with a uniform inlet total pressure is studied numerically. A circular hot streak is superposed on the vane inlet flow. In agreement with previous experimental and numerical work, it is observed that while the streak passes through the vane unaltered, significant radial transport occurs in the rotor. Furthermore, despite the unsteady nature of the flow field, the steady theory of Hawthorne (1974) is found to predict the radial transport velocity well. Making use of this theory, it is shown that the secondary vorticity in the rotor may be attributed to the effects of density stratification, the spatial variation of the vane exit flow angle, and the relative eddy. It then follows that the extent of radial transport in the rotor may be influenced by altering the vane exit flow angle distribution. The present study examines one means by which this may be effected, viz., varying the vane twist across the span. It is shown that a “reverse” twist, wherein the flow angle at the vane exit is larger near the tip than it is at midspan, reduces the secondary flow (and consequently, radial transport) in the blade passage. On the other hand, “positive” twist, in which the vane exit flow angle decreases with span, is found to worsen the radial transport in the blade markedly. It is to be noted that varying the vane twist is but one method to obtain the desired exit flow angle; possibilities for altering other aspects of the vane geometry also exist. [S0889-504X(00)00104-5]

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.

Effects of Flow Injection From Outer Casing Upon Turbine Nozzle Vane Flow Field

2002 ◽  
Author(s):  
K. Funazaki ◽  
C. F. F. Favaretto ◽  
T. Tanuma
Keyword(s):  
Flow Field ◽  
Flow Injection ◽  
Three Dimensional ◽  
Leading Edge ◽  
Main Stream ◽  
Flow Angle ◽  
Aerodynamic Loss ◽  
Nozzle Vane ◽  
Design Variables ◽  
The Impact

In the present paper steady three-dimensional numerical calculations were performed in order to investigate the effects of flow injection from the outer casing upon turbine nozzle vane flow field. Several test cases were analyzed by applying different nozzle vane configurations such as the blade lean, injection slot width and distance from the leading edge. Numerical simulations were conducted considering the no injection case, 5% and 10% main stream flow injection from the outer casing. The impact of the flow injection design variables and the blade lean angle on the aerodynamic loss in terms of the energy loss coefficient and the outlet flow angle were analyzed through a parametric study.

Investigation of the Surge Behavior of a Multi-Stage Axial Compressor With a Multi-Sensor Probe

2011 ◽  
Author(s):  
P. Waniczek ◽  
P. Jeschke ◽  
H. Schoenenborn ◽  
T. Metzler
Keyword(s):  
Flow Field ◽  
Velocity Vector ◽  
Reverse Flow ◽  
Axial Compressor ◽  
Leading Edge ◽  
Field Structure ◽  
Pressure Probe ◽  
High Time Resolution ◽  
Trailing Edge ◽  
Flow Angle

The surge behavior of the first rotor of an eight-stage aero engine high pressure compressor has been investigated experimentally. For that purpose, a new multi-hole pressure probe was developed and adapted to the axial compressor test rig. Due to the high time resolution measurements (more than 45000 measuring points per surge cycle) it is possible to investigate the dynamic flow field of a surge cycle in a time-accurate manner. The results especially show the complex flow field structure at the surge inception. At the rotor leading edge the flow shows perturbations with high amplitudes and initiates the surge event, whereas the flow at the rotor trailing edge is less influenced. The inflow vector turns around the leading edge of the blade relatively slowly. During that turn around three different characteristic flow conditions have been identified. These are ‘zero rotor turning’, ‘turbine-like flow’ and ‘no flow’. ‘No flow’ means, that the absolute velocity vector reaches a flow angle where it consists of a pure tangential velocity component. That is the point where the reverse flow phase is initiated. A 180° shift of the flow direction at the rotor trailing edge is the consequence. After a quasi-steady reverse flow the acceleration of the flow starts. In total, this paper gives new and fundamental insights into the unsteady flow field phenomena during various surge cycles. Especially the transient velocity vector imparts a good idea of the flow field structure of a surging compressor.

Mixed Flow Turbines: Inlet and Exit Flow Under Steady and Pulsating Conditions

2000 ◽  
Author(s):  
N. Karamanis ◽  
R. F. Martinez-Botas ◽  
C. C. Su
Keyword(s):  
High Speed ◽  
Pulse Propagation ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Mixed Flow ◽  
Flow Measurements ◽  
Flow Angle ◽  
Isentropic Efficiency

The performance and detailed flow characteristics of a high pressure ratio mixed flow turbine has been investigated under steady and pulsating flow conditions. The rotor has been designed to have a nominal constant incidence (based on free vortex flow in the volute) and it is for use in an automotive high speed diesel turbocharger. The results indicated a departure from the quasi-steady analysis commonly used in turbocharger turbine design. The pulsations from the engine have been followed through the inlet pipe and around the volute; the pulse has been shown to propagate close to the speed of sound and not according to the bulk flow velocity as stated by some researchers. The flow entering and exiting the blades has been quantified by a laser Doppler velocimetry system. The measurements were performed at a plane 3.0 mm ahead of the rotor leading edge and 9.5 mm behind the rotor trailing edge. The turbine test conditions corresponded to the peak efficiency point at 29,400 and 41,300 rpm. The results were resolved in a blade-to-blade sense to examine in greater detail the nature of the flow at turbocharger representative conditions. A correlation between the combined effects of incidence and exit flow angle with the isentropic efficiency has been shown. The unsteady flow characteristics have been investigated at two flow pulse frequencies, corresponding to internal combustion engine speeds of 1600 and 2400 rpm. Four measurement planes have been investigated: one in the pipe feeding the volute, two in the volute (40° and 130° downstream of the tongue) and one at the exit of the turbine. The pulse propagation at these planes has been investigated; the effect of the different planes on the evaluation of the unsteady isentropic efficiency is shown to be significant. Overall, the unsteady performance efficiency results indicated a significant departure from the corresponding steady performance, in accordance with the inlet and exit flow measurements.

Influence of Stator-Rotor Interaction on the Aerothermal Performance of Recess Blade Tips

2008 ◽  
Author(s):  
Bob Mischo ◽  
Andre´ Burdet ◽  
Reza S. Abhari
Keyword(s):  
Nusselt Number ◽  
Steady State ◽  
Flow Field ◽  
Heat Load ◽  
Design Procedure ◽  
Leading Edge ◽  
Cavity Flow ◽  
Turbine Stage ◽  
Beneficial Effects ◽  
Time Average

This paper investigates the influence of stator-rotor interaction on the stage performance of three blade tip geometries. A reference flat tip is used to assess two different recess blade geometries. The study is made in the context of the realistic turbine stage configuration provided by the ETHZ 1.5 stage LISA turbine research facility. This numerical investigation describes the details of unsteady recess cavity flow structure and confirms the beneficial effects of the improved recess geometry over the flat tip and the nominal recess design both in terms of stage efficiency and tip heat load. The tip flow field obtained from the improved recess design combines the advantages of a nominal recess design (aerodynamic sealing) and the flat tip configuration. The turbine stage capacity is almost unchanged between the flat tip and the improved recess tip cases, which simplifies the design procedure when using the improved recess design. Overall heat load in the improved recess case is reduced by 26% compared to the flat tip and by 12% compared to the nominal recess. A key finding of this study is the difference in effects of the upstream stator wake on the recess cavity flow. Where cavity flow in the nominal design is only moderately influenced, the improved recess cavity flow shows enhanced flow unsteadiness. The tip Nusselt number from a purely steady state prediction in the nominal recess case is nearly identical to the time-average prediction. The improved design shows a 6% difference between steady state and time average tip Nusselt number. This is due to the strong influence of the wake passing on the recess cavity flow. In fact, the wake enhances a small flow difference at the leading edge of the recess cavity between the nominal and improved recess cavities, which results in a completely different flow field further downstream in the recess cavity.

Effect of Inlet Swirl on the Model Leading Edge of Turbine Vane

2013 ◽  
Author(s):  
Hong Yin ◽  
Yanmin Qin ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Leading Edge ◽  
Operating Conditions ◽  
Test Model ◽  
Angle Distribution ◽  
Middle Section ◽  
Flow Angle ◽  
Stagnation Line ◽  
Film Cooling Effectiveness

Lean premixed combustion technology has been widely adopted in heavy duty and industrial gas turbine combustor. To enhance mixing and stabilize the flame, the large recirculation zone is built up by introducing strong swirling flow, which causes non-uniform flow field and has effect on the first stage vane, especially the leading edge. This paper investigates the effect of swirling flow on the downstream vane film cooling. Test rig consists of a swirler nozzle (swirl number equals 0.45) and a model leading edge with three rows of film cooling holes. Five-hole probe and pressure sensitive paint measurements were carried out. The operating conditions range includes three blowing ratios, two density ratios of cooling flow and two distances between the swirler and the model leading edge. Numerical simulations were also conducted and compared with the accumulated experimental data. Results show that the stagnation line of the model leading edge under swirling inlet flow condition is obviously altered compared with uniform inflow. Dividing the test model into three sections, film cooling effectiveness distribution has distinct characteristics in each section. Both ends of the model are mainly influenced by the flow direction. However the middle section performs differently since the vortex core impingement directly disturbs the film cooling ejection. Furthermore, detailed computational analysis reveals the swirling flow character and that the combined effect of total pressure and flow angle distribution dominates the film cooling of middle section.

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%.

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.

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