Unsteady Performance of a Double Entry Turbocharger Turbine With a Comparison to Steady Flow Conditions

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Colin D. Copeland ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Steady Flow ◽  
Flow Behavior ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Pulsed Flow ◽  
Performance Map ◽  
Engine Operating Condition ◽  
Double Entry ◽  
The Impact

Circumferentially divided, double entry turbocharger turbines are designed with a dividing wall parallel to the machine axis such that each entry feeds a separate 180 deg section of the nozzle circumference prior to entry into the rotor. This allows the exhaust pulses originating from the internal combustion exhaust to be preserved. Since the turbine is fed by two separate unsteady flows, the phase difference between the exhaust pulses entering the turbine rotor will produce a momentary imbalance in the flow conditions around the periphery of the turbine rotor. This research seeks to provide new insight into the impact of unsteadiness on turbine performance. The discrepancy between the pulsed flow behavior and that predicted by a typical steady flow performance map is a central issue considered in this work. In order to assess the performance deficit attributable to unequal admission, the steady flow conditions introduced in one inlet were varied with respect to the other. The results from these tests were then compared with unsteady, in-phase and out-of-phase pulsed flows most representative of the actual engine operating condition.

Unsteady Performance of a Double Entry Turbocharger Turbine With a Comparison to Steady Flow Conditions

2008 ◽  
Author(s):  
Colin D. Copeland ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Steady Flow ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Pulsed Flow ◽  
Performance Map ◽  
Unsteady Performance ◽  
Engine Operating Condition ◽  
Double Entry ◽  
The Impact

Circumferentially divided, double-entry turbocharger turbines are designed with a dividing wall parallel to the machine axis such that each entry feeds a separate 180° section of the nozzle circumference prior to entry into the rotor. This allows the exhaust pulses originating from the internal combustion exhaust to be preserved. Since the turbine is fed by two separate unsteady flows, the phase difference between the exhaust pulses entering the turbine rotor will produce a momentary imbalance in the flow conditions around the periphery of the turbine rotor. This research seeks to provide new insight into the impact of unsteadiness on turbine performance. The discrepancy between the pulsed flow behaviour and that predicted by a typical steady flow performance map is a central issue considered in this work. In order to assess the performance deficit attributable to unequal admission, the steady flow conditions introduced in one inlet were varied with respect to the other. The results from these tests were then compared to unsteady, in-phase and out-of-phase pulsed flow most representative of the actual engine operating condition.

Impact of Individual High-Pressure Turbine Rotor Purge Flows on Turbine Center Frame Aerodynamics

2017 ◽  
Author(s):  
S. Zerobin ◽  
C. Aldrian ◽  
A. Peters ◽  
F. Heitmeir ◽  
E. Göttlich
Keyword(s):  
High Pressure ◽  
Pressure Loss ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
High Pressure Turbine ◽  
Reference Case ◽  
University Of Technology ◽  
Purge Flow ◽  
Generation Mechanisms ◽  
The Impact

This paper presents an experimental study of the impact of individual high-pressure turbine purge flows on the main flow in a downstream turbine center frame duct. Measurements were carried out in a product-representative one and a half stage turbine test setup, installed in the Transonic Test Turbine Facility at Graz University of Technology. The rig allows testing at engine-relevant flow conditions, matching Mach, Reynolds, and Strouhal number at the inlet of the turbine center frame. The reference case features four purge flows differing in flow rate, pressure, and temperature, injected through the hub and tip, forward and aft cavities of the high-pressure turbine rotor. To investigate the impact of each individual cooling flow on the flow evolution in the turbine center frame, the different purge flows were switched off one-by-one while holding the other three purge flow conditions. In total, this approach led to six different test conditions when including the reference case and the case without any purge flow ejection. Detailed measurements were carried out at the turbine center frame duct inlet and outlet for all six conditions and the post-processed results show that switching off one of the rotor case purge flows leads to an improved duct performance. In contrast, the duct exit flow is dominated by high pressure loss regions if the forward rotor hub purge flow is turned off. Without the aft rotor hub purge flow, a reduction in duct pressure loss is determined. The purge flows from the rotor aft cavities are demonstrated to play a particularly important role for the turbine center frame aerodynamic performance. In summary, this paper provides a first-time assessment of the impact of four different purge flows on the flow field and loss generation mechanisms in a state-of-the-art turbine center frame configuration. The outcomes of this work indicate that a high-pressure turbine purge flow reduction generally benefits turbine center frame performance. However, the forward rotor hub purge flow actually stabilizes the flow in the turbine center frame duct and reducing this purge flow can penalize turbine center frame performance. These particular high-pressure turbine/turbine center frame interactions should be taken into account whenever high-pressure turbine purge flow reductions are pursued.

A Method of Map Extrapolation for Unequal and Partial Admission in a Double Entry Turbine

2013 ◽  
Author(s):  
Peter Newton ◽  
Alessandro Romagnoli ◽  
Ricardo Martinez-Botas ◽  
Colin Copeland ◽  
Martin Seiler
Keyword(s):  
Velocity Ratio ◽  
Test Stand ◽  
Turbine Wheel ◽  
Turbine Performance ◽  
Admission Data ◽  
Partial Admission ◽  
Single Entry ◽  
Data Points ◽  
Double Entry ◽  
The Impact

This paper presents a method for prediction of the unequal admission performance of a double entry turbine based on the full admission turbine maps and a minimal number of unequal admission points. The double entry turbine has two separate inlet ports which feed a single turbine wheel: this arrangement can be beneficial in a turbocharger application; however the additional entry does add complexity in producing a complete turbine map which includes unequal admission behaviour. When a double entry turbine is operated under full admission conditions, with both entries feeding the turbine equally, this will act effectively as a single entry device and the turbine performance can be represented by a standard turbine map. In reality a multiple entry turbine will spend the majority of time operating under varying degrees of unequal admission, with each entry feeding the turbine different amounts; the extent of this inequality can have a considerable impact on turbine performance. In order to produce a full map which extends from full admission through to the partial admission case (where one inlet has no flow) a large number of unequal admission data points are required. The paper starts by discussing previous attempts to describe the partial and unequal admission performance of a double entry turbine. The full unequal admission performance is then presented for a nozzled, double entry turbine. The impact of unequal admission on turbine performance is demonstrated. Under some conditions of operation, the turbine efficiency may be less than half that of the equivalent full admission case based on the average turbine velocity ratio. A method of using the steady, equal admission maps, with a limited number of unequal admission data points, to predict the full unequal admission behaviour is presented. A good agreement is found when the map extension method is validated against the full unequal admission turbine performance measured on a test stand. In the prediction of efficiency a mean error of approximately 0.39% is found between the test stand data and the proposed extrapolation method, with a standard deviation of 2.79%. A better agreement is generally found at conditions of higher power.

Investigation on the flow characteristics of a VNT turbine under pulsating flow conditions

2017 ◽  
Vol 233 (2) ◽  
pp. 396-412 ◽  
Author(s):  
Mingxu Qi ◽  
Xinguo Lei ◽  
Zhen Wang ◽  
Chaochen Ma
Keyword(s):  
Shock Wave ◽  
Rotor Blade ◽  
Strong Influence ◽  
Flow Characteristics ◽  
Turbine Rotor ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Turbine Inlet ◽  
Excitation Force

The turbines used in turbochargers naturally experience unsteadiness caused by inlet pulsating flow conditions and stator–rotor interaction. The unsteadiness has an influence on turbine performance. Meanwhile, under certain small-nozzle opening conditions, strong shock waves can be generated. The synergistic effect of turbine inlet pulsation and shock waves has a significant influence on the turbine performance, rotor blade loading as well as the excitation force exerted on the turbine rotor, which is responsible for turbine rotor high cycle fatigue. In order to understand the influence of pulsating flows on turbine performance and the shock wave characteristic at nozzle trailing edge as well as the incidence angle characteristic of the rotor blade, unsteady numerical simulations were performed to investigate the effect of pulsating flow conditions on the performance, flow characteristics in frequency domain and shock wave behavior in a variable nozzle turbine. The results indicate that the turbine inlet pressure pulsation has strong influence on the turbine performances. Meanwhile, the turbine inlet pulsation flow has a strong influence on the intensity of the shock wave and clearance leakage flow in the nozzle, which causes significant flow losses in the turbine. In addition, at the turbine rotor inlet, the unsteadiness caused by the turbine inlet pulsation varies significantly along the circumferential direction and spanwise. Up to two-thirds of the unsteadiness caused by the turbine inlet pulsation dissipates before entering the rotor due to the flow dissipation and mixing process along the nozzle streamwise. The excitation force exerted on the rotor blade leading edge caused by the turbine inlet pulsation is about the same level as that caused by the stator–rotor interaction.

Transition to Turbulence Downstream of a Stenosis for Whole Blood and a Newtonian Analog Under Steady Flow Conditions

2021 ◽  
Author(s):  
Rayanne Pinto Costa ◽  
Blaise Simplice Talla Nwotchouang ◽  
Junyao Yao ◽  
Dipankar Biswas ◽  
David Casey ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Steady Flow ◽  
Whole Blood ◽  
Critical Reynolds Number ◽  
Blood Rheology ◽  
Transition To Turbulence ◽  
Flow Conditions ◽  
Shear Rates ◽  
The Impact

Abstract Blood, a multiphase fluid comprised of plasma, blood cells, and platelets, is known to exhibit a shear-thinning behavior at low shear rates and near-Newtonian behavior at higher shear rates. However, less is known about the impact of its multiphase nature on the transition to turbulence. In this study, we experimentally determined the critical Reynolds number at which the flow began to transition to turbulence downstream of an eccentric stenosis for whole porcine blood and a Newtonian blood analog (water-glycerin mixture). Velocity profiles for both fluids were measured under steady-state flow conditions using an ultrasound Doppler probe placed 12 diameters downstream of an eccentric stenosis. Velocity was recorded at 21 locations along the diameter at 11 different flow rates. Normalized turbulent kinetic energy was used to determine the critical Reynolds number for each fluid. Blood rheology was measured before and after each experiment. Tests were conducted on five samples of each fluid inside a temperature-controlled in-vitro flow system. The viscosity at shear rate 1000 s 1 was used to define the Reynolds number for each fluid. The mean critical Reynolds numbers for blood and water-glycerin were 470 ± 27.5 and 395 ± 10, respectively, indicating a ~19% delay in transition to turbulence for whole blood compared to the Newtonian fluid. This finding is consistent with a previous report for steady flow in a straight pipe, suggesting some aspect of blood rheology may serve to suppress, or at least delay, the onset of turbulence in vivo.

Comparison Between Steady and Unsteady Double-Entry Turbine Performance Using the Quasi-Steady Assumption

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
Colin D. Copeland ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Steady State ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Experimental Performance ◽  
State Data ◽  
Turbine Performance ◽  
Partial Admission ◽  
Unsteady Operation ◽  
Unsteady Performance ◽  
Double Entry

The experimental performance evaluation of a circumferentially divided, double-entry turbocharger turbine is presented in this paper with the aim of understanding the influence of pulsating flow. By maintaining a constant speed but varying the frequency of the pulses, the influence of frequency was shown to play an important role in the performance of the turbine. A trend of decreasing cycle-averaged efficiency at lower frequencies was measured. One of the principal objectives was to assess the degree to which the unsteady performance differs from the quasi-steady assumption. In order to make the steady-unsteady comparison for a multiple entry turbine, a wide set of steady equal and unequal admission flow conditions were tested. The steady-state data was then interpolated as a function of three, nondimensional parameters in order to allow a point-by-point comparison with the instantaneous unsteady operation. As an average, the quasi-steady assumption generally underpredicted the mass flow and efficiency loss through the turbine, albeit the differences were reduced as the frequency increased. Out-of-phase pulsations produced unsteady operating orbits that corresponded to a significant steady-state, partial admission loss, and this was reflected as a drop in the quasi-steady efficiency. However, these differences between quasi-steady in-phase and out-of-phase predictions were not replicated in the measured results, suggesting that the unequal admission loss is not as significant in pulsating flow as it is in steady flow.

Hemolysis During Membrane Plasma Separation With Pulsed Flow Filtration Enhancement

1994 ◽  
Vol 116 (4) ◽  
pp. 514-520 ◽  
Author(s):  
Jane L. Philp ◽  
Michel Y. Jaffrin ◽  
Luhui Ding
Keyword(s):  
Blood Flow ◽  
Steady Flow ◽  
Hemoglobin Concentration ◽  
Transmembrane Pressure ◽  
Flow Conditions ◽  
Membrane Area ◽  
Shear Rates ◽  
Pulsed Flow ◽  
Plasma Filtration ◽  
Wall Shear

The use of pulsed blood flow in membrane plasmapheresis permits enhancement of plasma filtration yet may result in high levels of hemolysis due to large increases in instantaneous transmembrane pressure (TMP). This work investigates the occurrence of hemolysis as a function of TMP and wall shear rates (γw) for both steady and pulsed blood flow conditions. Two types of hollow fiber filters with identical polypropylene membranes but different lengths and membrane areas (0.1 and 0.25 m2) were tested. Fresh citrated bovine blood was circulated through the fibers at various blood flowrates and TMP in a single pass circuit using a pulsation generator, made of a single roller peristaltic pump. The free hemoglobin concentration of the plasma, Hbm, was measured from permeate samples collected at each set of TMP and γw conditions. It was found that the net hemolysis generated by the filtration was proportional to the membrane area. This justified the introduction of an hemolysis index, IH, equal to the plasma hemoglobin per unit membrane area. The boundary for the occurrence of hemolysis was thus defined by setting IH = 30 mg/ dl.m2. For both steady and pulsed flow conditions the hemolysis boundaries were found to be straight lines in the TMP-γw plane. They were identical for the two filters under steady flow but different for pulsed flow. At the same time mean wall shear rates hemolysis occurred at a lower time mean TMP under pulsed flow conditions than under steady flow conditions.

Evaluation of Magnetic Resonance Velocimetry for Steady Flow

1990 ◽  
Vol 112 (4) ◽  
pp. 464-472 ◽  
Author(s):  
D. N. Ku ◽  
C. L. Biancheri ◽  
R. I. Pettigrew ◽  
J. W. Peifer ◽  
C. P. Markou ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Steady Flow ◽  
Laser Doppler Anemometry ◽  
Flow Behavior ◽  
Velocity Profiles ◽  
Secondary Flows ◽  
Whole Body ◽  
Straight Tube ◽  
Flow Conditions ◽  
Wide Range

Whole body magnetic resonance (MR) imaging has recently become an important diagnostic tool for cardiovascular diseases. The technique of magnetic resonance phase velocity encoding allows the quantitative measurement of velocity for an arbitrary component direction. A study was initiated to determine the ability and accuracy of MR velocimetry to measure a wide range of flow conditions including flow separation, three-dimensional secondary flow, high velocity gradients, and turbulence. A steady flow system pumped water doped with manganese chloride through a variety of test sections. Images were produced using gradient echo sequences on test sections including a straight tube, a curved tube, a smoothly converging-diverging nozzle, and an orifice. Magnetic resonance measurements of laminar and turbulent flows were depicted as cross-sectional velocity profiles. MR velocity measurements revealed such flow behavior as spatially varying velocity, recirculation and secondary flows over a wide range of conditions. Comparisons made with published experimental laser Doppler anemometry measurements and theoretical calculations for similar flow conditions revealed excellent accuracy and precision levels. The successful measurement of velocity profiles for a variety of flow conditions and geometries indicate that magnetic resonance imaging is an accurate, non-contacting velocimeter.

scholarly journals Numerical and physical modeling of water flow over the ogee weir of the new Niedów barrage

2016 ◽  
Vol 64 (1) ◽  
pp. 67-74 ◽  
Author(s):  
Oscar Herrera-Granados ◽  
Stanisław W. Kostecki
Keyword(s):  
Experimental Data ◽  
Numerical Modeling ◽  
Steady Flow ◽  
Water Flow ◽  
Physical Modeling ◽  
Numerical Models ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Flow Conditions ◽  
Low Head

Abstract In this paper, two- and three-dimensional numerical modeling is applied in order to simulate water flow behavior over the new Niedów barrage in South Poland. The draining capacity of one of the flood alleviation structures (ogee weir) for exploitation and catastrophic conditions was estimated. In addition, the output of the numerical models is compared with experimental data. The experiments demonstrated that the draining capacity of the barrage alleviation scheme is sufficiently designed for catastrophic scenarios if water is flowing under steady flow conditions. Nevertheless, the new cofferdam, which is part of the temporal reconstruction works, is affecting the draining capacity of the whole low-head barrage project.

A Method of Map Extrapolation for Unequal and Partial Admission in a Double Entry Turbine

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Peter Newton ◽  
Alessandro Romagnoli ◽  
Ricardo Martinez-Botas ◽  
Colin Copeland ◽  
Martin Seiler
Keyword(s):  
Velocity Ratio ◽  
Test Stand ◽  
Turbine Wheel ◽  
Turbine Performance ◽  
Admission Data ◽  
Partial Admission ◽  
Single Entry ◽  
Data Points ◽  
Double Entry ◽  
The Impact

This paper presents a method for prediction of the unequal admission performance of a double entry turbine based on the full admission turbine maps and a minimal number of unequal admission points. The double entry turbine has two separate inlet ports which feed a single turbine wheel: this arrangement can be beneficial in a turbocharger application; however the additional entry does add complexity in producing a complete turbine map which includes unequal admission behavior. When a double entry turbine is operated under full admission conditions, with both entries feeding the turbine equally, this will act effectively as a single entry device and the turbine performance can be represented by a standard turbine map. In reality a multiple entry turbine will spend the majority of time operating under varying degrees of unequal admission, with each entry feeding the turbine different amounts; the extent of this inequality can have a considerable impact on turbine performance. In order to produce a full map which extends from full admission through to the partial admission case (where one inlet has no flow) a large number of unequal admission data points are required. The paper starts by discussing previous attempts to describe the partial and unequal admission performance of a double entry turbine. The full unequal admission performance is then presented for a nozzled, double entry turbine. The impact of unequal admission on turbine performance is demonstrated. Under some conditions of operation, the turbine efficiency may be less than half that of the equivalent full admission case based on the average turbine velocity ratio. A method of using the steady, equal admission maps, with a limited number of unequal admission data points, to predict the full unequal admission behavior is presented. A good agreement is found when the map extension method is validated against the full unequal admission turbine performance measured on a test stand. In the prediction of efficiency a mean error of approximately 0.39% is found between the test stand data and the proposed extrapolation method, with a standard deviation of 2.79%. A better agreement is generally found at conditions of higher power.

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