scholarly journals The influence of secondary flow structures in a turbocharger turbine housing in steady state and pulsating flow conditions

2016 ◽  
Author(s):  
S. P. Lee ◽  
M. L. Jupp ◽  
A. K. Nickson
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Pulsating Flow ◽  
Flow Structures ◽  
Flow Conditions ◽  
Turbine Housing

Optimization of a Radial Turbine for Pulsating Flows

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Zheng Liu ◽  
Colin Copeland
Keyword(s):  
Steady State ◽  
Cone Angle ◽  
Exhaust System ◽  
Maximum Energy ◽  
Pulsating Flow ◽  
Energy Output ◽  
Small Scale ◽  
Maximum Deviation ◽  
Flow Conditions ◽  
Blade Shape

Abstract A turbocharger turbine is exposed to pulsating flow conditions when it is connected to an engine exhaust system due to the opening and closing of the exhaust valves. However, many radial turbines are designed and tested under steady-state conditions without taking into account these unsteady exhaust flows. In order to seek the optimal aerodynamic design of a radial flow turbine (RFT) under pulsating flow conditions, the present research utilizes a numerical simulation approach to optimize the blade shape of a small-scale mixed flow turbine (MFT) under 50 Hz pulses. This corresponds to a four-stroke, three-cylinder engine rotating at 2000 rpm. In order to understand how a less computationally intensive, steady-state optimization compares, the blade shape was also optimized using the peak power point of the pulse. Three turbine features were modified during the optimization process, including blade cone angle, blade axial location, and blade camber angles. The optimization was carried out using a computational fluid dynamics (CFD)–genetic algorithm (GA) coupled approach, targeting at maximizing both energy-weighted efficiency and energy output during a predefined pulse period. To ensure that the new design maintains a similar matching to the engine, the maximum deviation of turbine swallowing capacity is controlled to within ±5% of the baseline for all new blade designs. The design that achieves the maximum pulse cycle-averaged efficiency was produced from unsteady optimization, with a performance benefit of 0.66%. The unsteady optimization also produced a blade shape that delivers the maximum energy output, with an improvement of 5.42%.

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.

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.

Influence of Degree of Reaction on Turbine Performance for Pulsating Flow Conditions

2014 ◽  
Author(s):  
Harald Roclawski ◽  
Marc Gugau ◽  
Florian Langecker ◽  
Martin Böhle
Keyword(s):  
Steady State ◽  
Hysteresis Loop ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Load Step ◽  
Turbine Wheel ◽  
Engine Load ◽  
Flow Capacity ◽  
Turbine Performance ◽  
Degree Of Reaction

This paper presents a study on the influence of the degree of reaction (DoR) on turbine performance under highly pulsating inflow. A reference test turbine wheel is designed and scaled to three different wheel diameters while an identical flow capacity of all three turbines is provided by adjusting the volute size. Hence, the three turbines differ by their DoR, inertia and efficiency characteristic. The investigation is done completely numerically using highly validated models. Naturally, the pulsating flow character of a 4-cylinder gasoline engine requires unsteady CFD. In addition steady-state turbine maps were calculated beforehand as a reference base. The results of the steady state calculation show that for the combination of the bigger turbine wheel with the smaller turbine volute the peak efficiency is smaller but is shifted towards higher pressure ratios respectively to lower blade speed ratios. This is fundamentally beneficial for turbines in automotive turbochargers for gasoline engines characterized by highly pulsating flow conditions, in particular at lower engine speeds. For the transient flow calculations with pulsating turbine inflow, the hysteresis loop and the turbine power generation was investigated. It is shown that the smallest volute compared to the biggest one causes a more contracted hysteresis loop combined with increased power output within one pulse cycle. In order to include the influence of moment of inertia, the turbines with varying DoR but same flow capacity were analytically compared with a 1D code simulating engine load step operation. Thus, the paper shows the effect of turbine DoR on both, steady-state turbine performance under pulsating inflow and the capability for optimum engine load step operation.

Impact of Varying High- and Low-Pressure Turbine Purge Flows on a Turbine Center Frame and Low-Pressure Turbine System

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
P. Z. Sterzinger ◽  
S. Zerobin ◽  
F. Merli ◽  
L. Wiesinger ◽  
A. Peters ◽  
...  
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Flow Structures ◽  
Flow Conditions ◽  
High Pressure Turbine ◽  
Inlet Flow ◽  
Low Pressure Turbine ◽  
The Impact ◽  
Inflow Conditions

Abstract This paper presents the experimental and numerical evaluation and comparison of the different flow fields downstream of a turbine center frame duct and a low-pressure turbine (LPT) stage, generated by varying the inlet flow conditions to the turbine center frame (TCF) duct. The measurements were carried out in an engine-representative two-stage two-spool test turbine facility at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. The rig consists of a high-pressure turbine (HPT) and a LPT turbine stage, connected via a TCF with non-turning struts. Four individual high-pressure turbine purge flowrates and two low-pressure turbine purge flowrates were varied to achieve different engine-relevant TCF and LPT inlet flow conditions. The experimental data were acquired by means of five-hole-probe (5HP) area traverses upstream and downstream of the TCF and downstream of the LPT. A steady Reynolds-averaged Navier–Stokes (RANS) simulation taking all purge flows in account was used for comparison, and additional insights are gained from a numerical variation of the HPT and LPT purge flowrates. The focus of this study is on the impact of the variations in TCF inlet conditions on the secondary flow generation through the TCF duct and the carryover effects on the exit flow field and performance of the LPT stage. Existing work is limited by either investigating multistage LPT configurations with generally very few measurements behind the first stage or by not including relevant HPT secondary flow structures in setting up the LPT inflow conditions. This work addresses both of these shortcomings and presents new insight into the TCF and LPT aerodynamic behavior at varying the HPT and LPT purge flows. The results demonstrate the importance of the HPT flow structures and their evolution through the TCF duct for setting up the LPT inflow conditions and ultimately for assessing the performance of the first LPT stage.

Impact of Varying High- and Low-Pressure Turbine Purge Flows on a Turbine Center Frame and Low-Pressure Turbine System

2019 ◽  
Author(s):  
P. Z. Sterzinger ◽  
S. Zerobin ◽  
F. Merli ◽  
L. Wiesinger ◽  
A. Peters ◽  
...  
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Flow Structures ◽  
Turbine Stage ◽  
Flow Conditions ◽  
Flow Rates ◽  
Low Pressure Turbine ◽  
Purge Flow ◽  
Inflow Conditions

Abstract This paper presents the experimental and numerical evaluation and comparison of the different flow fields downstream of a turbine center frame duct and a low-pressure turbine stage, generated by varying the inlet flow conditions to the turbine center frame duct. The measurements were carried out in an engine-representative two-stage two-spool test turbine facility at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. The rig consists of a high-pressure (HPT) and a low-pressure (LPT) turbine stage, connected via a turbine center frame (TCF) with non-turning struts. Four individual high-pressure turbine purge flow rates and two low-pressure turbine purge flow rates were varied to achieve different engine-relevant TCF and LPT inlet flow conditions. The experimental data was acquired by means of five-hole-probe area traverses upstream and downstream of the TCF, and downstream of the LPT. A steady RANS simulation taking all purge flows in account was used for comparison and additional insight are gained from a numerical variation of the HPT and LPT purge flow rates. The focus of this study is on the impact of the variations in TCF inlet conditions on the secondary flow generation through the TCF duct and the carry-over effects on the exit flow field and performance of the LPT stage. Existing work is limited by either investigating multi-stage LPT configurations with generally very few measurements behind the first stage or by not including relevant HPT secondary flow structures in setting up the LPT inflow conditions. This work addresses both of these shortcomings and presents new insight into the TCF and LPT aerodynamic behavior at varying the HPT and LPT purge flows. The results demonstrate the importance of the HPT flow structures and their evolution through the TCF duct for setting up the LPT inflow conditions, and ultimately for assessing the performance of the first LPT stage.

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

2009 ◽  
Author(s):  
Colin D. Copeland ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Steady State ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Experimental Performance ◽  
Turbine Performance ◽  
Partial Admission ◽  
Dimensional Parameters ◽  
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, non-dimensional parameters in order to allow a point-by-point comparison with the instantaneous unsteady operation. As an average, the quasi-steady assumption generally under-predicted 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.

Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Brahmaji Vasantharao
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Life Prediction ◽  
Creep Damage ◽  
Back Pressure ◽  
System Level ◽  
Cyclic Life ◽  
Power Turbine ◽  
The Impact

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine. This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach. Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks. Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives. The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.

Sign in / Sign up

Export Citation Format

Share Document