PRESSURE DISTRIBUTION ON THE BLADE SURFACE OF AN AUTOMOTIVE MIXED FLOW TURBOCHARGER TURBINE UNDER PULSATING FLOW CONDITIONS

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
M.H. Padzillah ◽  
S. Rajoo ◽  
R.F. Martinez-Botas
Keyword(s):  
Weight Ratio ◽  
Pulsating Flow ◽  
World Population ◽  
Transportation Industry ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Blade Loading ◽  
Torque Generation ◽  
Computational Fluid Dynamics Cfd ◽  
Stroke Engine

The increment of the contribution to CO2 release by transportation industry as other sectors are decarbonizing is evident. As number of world population continue to increase, the task of developing highly downsized high power-to-weight ratio engines are critical. Over more than a hundred years of invention, turbocharger remains a key technology that enable highly boosted efficient engine. Despite its actual operating environment which is pulsating flow, the turbocharger turbine that is available to date is still designed and assessed under the assumption of steady flow conditions. This is attributable to the lack of understanding on the insight of the flow field effect towards the torque generation of the turbine blade under pulsating flow conditions. This paper presents an effort towards investigating the influence of pulsating flow on the blade loading and its differences from steady state conditions through the use of Computational Fluid Dynamics (CFD). For this purpose, a lean-vaned mixed-flow turbine with rotational speed of 30000 rpm at 20 Hz flow frequency, which represent turbine operation for 3-cylinder 4-stroke engine operating at 800 rpm has been used. Results presented in terms of spanwise location of the blade indicated different behavior at each location. Close to the hub, there are strong flow separation that hinders torque generation is seen while at mid-span more torque is generated under unsteady flow as compared to its steady counterpart. Moreover, close to the shroud, the pressure difference between steady and pulsating flow is almost identical

scholarly journals COMPARISON OF FLOW FIELD BETWEEN STEADY AND UNSTEADY FLOW OF AN AUTOMOTIVE MIXED FLOW TURBOCHARGER TURBINE

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
M.H. Padzillah ◽  
S. Rajoo ◽  
R.F. Martinez-Botas
Keyword(s):  
Flow Field ◽  
Weight Ratio ◽  
Pulsating Flow ◽  
Transportation Industry ◽  
Mixed Flow ◽  
Irregular Pattern ◽  
Pressure Increment ◽  
Integral Element ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Blockage

Global decarbonizing efforts in transportation industry have forced the automotive manufacturers to opt for highly downsized high power-to-weight ratio engines. Since its invention, turbocharger remains as integral element in order to achieve this target. However, although it has been proven that a turbocharger turbine works in highly pulsatile environment, it is still designed under steady state assumption. This is due to the lack of understanding on the nature of pulsating flow field within the turbocharger turbine stage. This paper presents an effort to visualize the pulsating flow feature using experimentally validated Computational Fluid Dynamics (CFD) simulations. For this purpose, a lean-vaned mixed-flow turbine with rotational speed of 30000 rpm at 20 Hz flow frequency, which represent turbine operation for 3-cylinder 4-stroke engine operating at 800 rpm has been used. Results indicated that the introduction of pulsating flow has resulted in more irregular pattern of flow field as compared to steady flow operation. It has also been indicated that the flow behaves very differently between pressure increment and decrement instances. During the pressure decrement instance, flow blockage in terms of low pressure region occupies most of the turbine passage as the flow exit the turbine. 

The Effect of Leading Edge Curvature on a Mixed Flow Turbine Performance Under Pulsating Flow Conditions

2009 ◽  
Author(s):  
Li Chen ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Shuyong Zhang
Keyword(s):  
Incidence Angle ◽  
Leading Edge ◽  
Simulation Models ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Turbine Performance ◽  
Unsteady Simulation ◽  
Overall Performance ◽  
Inlet Angle

Turbines used in turbochargers matched to reciprocating engines are under natural pulsating flow conditions, and the turbine which has a good performance under steady design condition normally cannot get the same performance in the whole engine actual working circle. Under the pulsating conditions, the incidence angle will change tremendously, thus leads to undesirable flowfield in the turbine. It is shown in some published literature that varying turbine blade inlet angle can achieve better performance characteristics. In this paper, leading edge curvature is introduced to an original mixed flow turbine, while steady and unsteady simulation models of the mixed flow turbine are built to investigate the aerodynamic performance of the original and modified turbine. Flowfield analysis shows that the leading edge curvature can make the flow less sensitive to the incidence change, and average instantaneous efficiency under pulsating flow conditions is improved, while a better overall performance of the turbine is achieved.

Investigation of the mixed flow turbine performance under inlet pulsating flow conditions

2012 ◽  
Vol 340 (3) ◽  
pp. 165-176 ◽  
Author(s):  
Mohammed Hamel ◽  
Miloud Abidat ◽  
Sid Ali Litim
Keyword(s):  
Pulsating Flow ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Turbine Performance

Analysis of a Tilted Turbine Housing Volute Design Under Pulsating Inlet Conditions

2017 ◽  
Author(s):  
Samuel P. Lee ◽  
Martyn L. Jupp ◽  
Ambrose K. Nickson ◽  
John M. Allport
Keyword(s):  
Steady State ◽  
Incidence Angle ◽  
Leading Edge ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Low Velocity ◽  
Mixed Flow ◽  
Turbine Wheel ◽  
Housing Design ◽  
Inlet Conditions

Radial inflow turbines are widely used in the automotive turbocharger industry due to the greater amount of work that can be extracted per stage and their ease of manufacture compared with equivalent axial designs [1]. The current industry trend towards downsized engines for lower emissions has driven research to focus on improving turbine technologies for greater aero-thermal efficiency. Consequently, mixed flow turbines have recently received significant interest due to a number of potential performance benefits over their radial counterparts, including reduced inertia and improved performance at low velocity ratios. This paper investigates the performance of a tilted volute design compared with that of a radial design, under steady state and pulsating flow conditions. The tilted volute design was introduced in an attempt to improve inlet flow conditions of a mixed flow turbine wheel and hence improve performance. The investigation is entirely computational and the approach used was carefully validated against gas stand test results. The results of the study show that under steady state conditions the tilted volute design resulted in stage efficiency improvements of up to 1.64%. Under pulsating flow conditions, the tilted housing design resulted in a reduction in incidence angle and a maximum cycle averaged rotor efficiency improvement of 1.49% while the stage efficiencies resulted in a 1.23% increase. To assess the loss mechanisms within the rotor, the entropy flux generation through the blade passage was calculated. The tilted housing design resulted in reductions in leading edge suction and shroud surface separation resulting in the improved efficiency as observed.

Performance of a Mixed Flow Turbocharger Turbine Under Pulsating Flow Conditions

1995 ◽  
Author(s):  
C. Arcoumanis ◽  
I. Hakeem ◽  
L. Khezzar ◽  
R. F. Martinez-Botas ◽  
N. C. Baines
Keyword(s):  
High Efficiency ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Engine Exhaust ◽  
High Pressure Ratio ◽  
Design Speed ◽  
Swallowing Capacity

The performance of a high pressure ratio (P.R.=2.9) mixed flow turbine for an automotive turbocharger has been investigated and the results revealed its better performance relative to a radial-inflow geometry under both steady and pulsating flow conditions. The advantages offered by the constant blade angle rotor allow better turbocharger-engine matching and maximization of the energy extracted from the pulsating engine exhaust gases. In particular, the mixed inlet blade geometry resulted in high efficiency at high expansion ratios where the engine-exhaust pulse energy is maximum. The efficiency characteristics of the mixed flow turbine under steady conditions were found to be fairly uniform when plotted against the velocity ratio, with a peak efficiency at the design speed of 0.75. The unsteady performance as indicated by the mass-averaged total-to-static efficiency and the swallowing capacity exhibited a departure from the quasi-steady assumption which is analysed and discussed.

Analysis and Validation of a Unified Slip Factor Model for Impellers at Design and Off-Design Conditions

2010 ◽  
Author(s):  
Xuwen Qiu ◽  
David Japikse ◽  
Jinhui Zhao ◽  
Mark R. Anderson
Keyword(s):  
Test Data ◽  
Slip Velocity ◽  
Factor Model ◽  
Flow Coefficient ◽  
Slip Model ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Blade Loading ◽  
New Model ◽  
Slip Factor

This paper presents a unified slip model for axial, radial, and mixed-flow impellers. The core assumption of the model is that the flow deviation or slip velocity at impeller exit is mainly originated from the blade loading near the discharge of an impeller and its subsequent relative eddy in the impeller passage. The blade loading is estimated and then used to derive the slip velocity using Stodola’s assumption. The final form of the slip factor model can be successfully related to Carter’s rule [1] for axial impellers and Stodola’s [2] slip model for radial impellers, making the case for this model to be applicable to axial, radial, and mixed-flow impellers. Unlike conventional slip factor models for radial impellers, the new slip model suggests that the flow coefficient at the impeller exit is an important variable for the slip factor when there is significant blade turning at the impeller discharge. This explains the interesting off-design trends for slip factor observed from experiments, such as the rise of the slip factor with flow coefficient in the Eckardt A impeller [3]. Extensive validation results for this new model are presented in this paper. Several cases are studied in detail to demonstrate how this new model can capture the slip factor variation at the off-design conditions. Furthermore, a large number of test data from more than 90 different compressors, pumps, and blowers were collected. Most cases are radial impellers, but a few axial impellers are also included. The test data and model predictions of the slip factor are compared at both design and off-design flow conditions. In total, over 1,650 different flow conditions are evaluated. The unified model shows a clear advantage over the traditional slip factor correlations, such as the Busemann-Wiesner model [4], when off-design conditions are considered.

Effects of Pulsating Flow Conditions on Mixed Flow Turbine Performance

2011 ◽  
Author(s):  
Li Chen ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Lei Xie ◽  
Shuyong Zhang
Keyword(s):  
Combustion Engine ◽  
Flow Fields ◽  
Pulsating Flow ◽  
Phase Lag ◽  
Pulsation Frequency ◽  
Flow Conditions ◽  
Operating Characteristics ◽  
Mixed Flow ◽  
Turbine Performance ◽  
Steady Performance

Turbines work under actual pulsating flow conditions due to the operating characteristics of a reciprocating internal combustion engine. The pulsating flow conditions affect the flow fields in a turbine, and lead to obvious difference between actual and steady performance. A three-dimensional numerical investigation into mixed flow turbine under different kinds of pulsating flow conditions was conducted, in order to get an inner sight of the unsteady impact. The effects of the pulsation frequency and amplitude on the turbine performance were analyzed. The results show that the period average performance of the turbine under pulsating conditions is lower than the steady performance under the mean pulsating conditions. The actual power output varies little with the pulsation frequency changing, while the phase lag increases as the pulsation frequency increases. The unsteady characteristics become more obvious when the pulsation amplitude increases. Under the pulsating flow conditions, of which amplitude is 0.8, the period average efficiency is 4.11 percent lower than the steady efficiency. The flow fields fluctuate seriously under this high pulsating flow conditions. The occurrence and vanishing of the votex are dynamic procedures, and hysteresis effect is observed in the unsteady flow.

Analysis and Validation of a Unified Slip Factor Model for Impellers at Design and Off-Design Conditions

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Xuwen Qiu ◽  
David Japikse ◽  
Jinhui Zhao ◽  
Mark R. Anderson
Keyword(s):  
Test Data ◽  
Slip Velocity ◽  
Factor Model ◽  
Flow Coefficient ◽  
Slip Model ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Blade Loading ◽  
New Model ◽  
Slip Factor

This paper presents a unified slip model for axial, radial, and mixed-flow impellers. The core assumption of the model is that the flow deviation or the slip velocity at the impeller exit is mainly originated from the blade loading near the discharge of an impeller and its subsequent relative eddy in the impeller passage. The blade loading is estimated and then used to derive the slip velocity using Stodola’s assumption. The final form of the slip factor model can be successfully related to Carter’s rule for axial impellers and Stodola’s slip model for radial impellers, making the case for this model applicable to axial, radial, and mixed-flow impellers. Unlike conventional slip factor models for radial impellers, the new slip model suggests that the flow coefficient at the impeller exit is an important variable for the slip factor when there is significant blade turning at the impeller discharge. This explains the interesting off-design trends for slip factor observed from experiments, such as the rise of the slip factor with flow coefficient in the Eckardt A impeller. Extensive validation results for this new model are presented in this paper. Several cases are studied in detail to demonstrate how this new model can capture the slip factor variation at the off-design conditions. Furthermore, a large number of test data from more than 90 different compressors, pumps, and blowers were collected. Most cases are radial impellers, but a few axial impellers are also included. The test data and model predictions of the slip factor are compared at both design and off-design flow conditions. In total, over 1650 different flow conditions are evaluated. The unified model shows a clear advantage over the traditional slip factor correlations, such as the Busemann–Wiesner model, when off-design conditions are considered.

Loss and Flow Path Studies on Centrifugal Compressors—Part II

1970 ◽  
Vol 92 (3) ◽  
pp. 287-300 ◽  
Author(s):  
O. E. Balje´
Keyword(s):  
Boundary Layer ◽  
High Efficiency ◽  
Flow Path ◽  
Flow Conditions ◽  
Centrifugal Compressors ◽  
Mixed Flow ◽  
Path Design ◽  
Balanced Flow ◽  
Efficiency Data ◽  
Rotor Flow

The flow conditions in a mixed flow rotor are investigated for a “pressure balanced” flow path design. Boundary layer arguments are applied to calculate the losses in the rotor as well as in the subsequent diffuser section. The resulting efficiency data imply a comparatively high efficiency potential for mixed flow compressors with multiple cascaded components, designed on the premise of a “pressure balanced” rotor flow path.

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