The effect of volute surface roughness on the performance of automotive turbocharger turbines

Abstract The roughness level of the turbine housing’s internal surfaces can affect the total pressure loss, and hence the efficiency, of turbine stages for automotive turbochargers significantly. The actual surface roughness achieved in the housing hardware depends on the manufacturing process. Improving the volute surface quality will in most cases be more expensive. The potential benefits in turbine efficiency therefore have to be balanced with the additional costs. In the present article, the aerodynamic effects due to changes of volute surface roughness are assessed. Pressure loss measurements in simple pipes are conducted in order to calibrate a computational fluid dynamics (CFD) sand grain roughness model against measured roughness values. Two test cases involving flow simulations of the complete turbine stage are presented in order to validate the calibrated model and to show that Reynolds-averaged Navier Stokes (RANS) CFD simulations are generally able to predict the effects of surface roughness on the turbine performance. The results of the test cases show a significant reduction in turbine efficiency with increased volute roughness levels. As expected, the sensitivity of efficiency due to changes in surface roughness of the volute is largest in areas of high near-wall velocity, i.e., at the volute exducer and in the small volute cross-sections close to the tongue.

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Modular Turbulence Modeling Applied to an Engine Intake

Journal of Turbomachinery ◽

10.1115/1.4025232 ◽

2013 ◽

Vol 136 (5) ◽

Cited By ~ 8

Author(s):

Ugochukwu R. Oriji ◽

Paul G. Tucker

Keyword(s):

Surface Roughness ◽

Turbulence Modeling ◽

Fluid Dynamic ◽

Navier Stokes ◽

Test Cases ◽

Laminar Separation ◽

Streamline Curvature ◽

Favorable Pressure Gradient ◽

Flow Features ◽

The One

The one equation Spalart–Allmaras (SA) turbulence model in an extended modular form is presented. It is employed for the prediction of crosswind flow around the lip of a 90 deg sector of an intake with and without surface roughness. The flow features around the lip are complex. There exists a region of high streamline curvature. For this, the Richardson number would suggest complete degeneration to laminar flow. Also, there are regions of high favorable pressure gradient (FPG) sufficient to laminarize a turbulent boundary layer (BL). This is all terminated by a shock and followed by a laminar separation. Under these severe conditions, the SA model is insensitive to capturing the effects of laminarization and the reenergization of eddy viscosity. The latter promotes the momentum transfer and correct reattachment prior to the fan face. Through distinct modules, the SA model has been modified to account for the effect of laminarization and separation induced transition. The modules have been implemented in the Rolls-Royce HYDRA computational fluid dynamic (CFD) solver. They have been validated over a number of experimental test cases involving laminarization and also surface roughness. The validated modules are finally applied in unsteady Reynolds-averaged Navier–Stokes (URANS) mode to flow around an engine intake and comparisons made with measurements. Encouraging agreement is found and hence advances made towards a more reliable intake design framework.

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Prediction of Surface Roughness and Incidence Effects on Turbine Performance

Volume 3B: General ◽

10.1115/93-gt-280 ◽

1993 ◽

Cited By ~ 1

Author(s):

R. J. Boyle

Keyword(s):

Surface Roughness ◽

Flow Analysis ◽

Three Dimensional ◽

Navier Stokes ◽

Three Dimensional Flow ◽

Dimensional Flow ◽

Turbine Efficiency ◽

Turbine Performance ◽

Wide Range ◽

Loss Models

The use of a Navier-Stokes analysis to predict the change in turbine efficiency resulting from changes in blade surface roughness or incidence flow angles is discussed. The results of a midspan Navier-Stokes analysis are combined with those from a quasi-three-dimensional flow analysis code to predict turbine performance. A quasi-three-dimensional flow analysis code was used to determine turbine performance over a range of incidence flow angles. This analysis was done for a number of incidence loss models. The change in loss due to changes in incidence flows computed from the Navier-Stokes analysis is compared with the results obtained using the empirical loss models. The Navier-Stokes analysis was also used to determine the effects of surface roughness using a mixing length turbulence model, which incorporated the roughness height. The validity of the approach used was verified by comparisons with experimental data for a turbine with both smooth and rough blades tested over a wide range of blade incidence flow angles.

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Prediction of Surface Roughness and Incidence Effects on Turbine Performance

Journal of Turbomachinery ◽

10.1115/1.2929468 ◽

1994 ◽

Vol 116 (4) ◽

pp. 745-751 ◽

Cited By ~ 23

Author(s):

R. J. Boyle

Keyword(s):

Surface Roughness ◽

Flow Analysis ◽

Three Dimensional ◽

Navier Stokes ◽

Three Dimensional Flow ◽

Dimensional Flow ◽

Turbine Efficiency ◽

Turbine Performance ◽

Wide Range ◽

Loss Models

The use of a Navier–Stokes analysis to predict the change in turbine efficiency resulting from changes in blade surface roughness or incidence flow angles is discussed. The results of a midspan Navier–Stokes analysis are combined with those from a quasi-three-dimensional flow analysis code to predict turbine performance. A quasi-three-dimensional flow analysis code was used to determine turbine performance over a range of incidence flow angles. This analysis was done for a number of incidence loss models. The change in loss due to changes in incidence flow computed from the Navier–Stokes analysis is compared with the results obtained using the empirical loss models. The Navier–Stokes analysis was also used to determine the effects of surface roughness using a mixing length turbulence model, which incorporated the roughness height. The validity of the approach used was verified by comparisons with experimental data for a turbine with both smooth and rough blades tested over a wide range of blade incidence flow angles.

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Study of Transmissivity of a Fracture Under Shearing

Volume 2: Development and Applications in Computational Fluid Dynamics; Industrial and Environmental Applications of Fluid Mechanics; Fluid Measurement and Instrumentation; Cavitation and Phase Change ◽

10.1115/fedsm2018-83348 ◽

2018 ◽

Author(s):

Amir A. Mofakham ◽

Goodarz Ahmadi ◽

Matthew Stadelman ◽

Kevin Shanley ◽

Dustin Crandall

Keyword(s):

Surface Roughness ◽

Rock Fracture ◽

Marcellus Shale ◽

Ct Scans ◽

Navier Stokes ◽

Fast Method ◽

Flow Rates ◽

Pressure Drops ◽

Fracture Pressure ◽

Cubic Law

A Marcellus shale rock fracture was subjected to four shearing steps and at the end of each shearing step CT (computed tomography) scans with resolution of 26.8 μm were obtained. The CT images were used to generate full aperture maps of the fracture configuration at the end of each shearing phase. The pressure drops along the fracture were also measured for different water flow rates through the fracture. The aperture map of the fracture was used to generate the geometry of the fracture for use in numerical simulations. The water flows and pressure drops in the fracture were simulated with different computational methods that included the full Navier-Stokes simulation, Modified Local Cubic Law (MLCL), and Improved Cubic Law (ICL) methods. Full 3-D Navier-Stokes simulation is the most accurate computational approach which was done with use of the ANSYS-Fluent software for each shear step and different flow rates. The MLCL is a 2-D relatively fast method which is commonly used for prediction of transmissivity of fractures. ICL is a 1-D method proposed in this study in which the effects of surface roughness and tortuosity were included in calculation of the effective aperture height of fractures. To provide an understanding of the accuracy of each of these models their predictions were compared with each other and with the experimental data. Also, to examine the effects of resolution of CT scans and the surface roughness on prediction of fractures transmissivity, similar simulations were performed on average aperture maps. Here the fracture of the full resolution data was averaged over 10 × 10 pixels. Comparing the results of the average aperture maps with those of the full maps showed that the lower resolution of CT scans led to underestimation of the fracture pressure drop due to missing the small features of the fracture surfaces and smoothing out their roughness.

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Two Algorithms for Solving Coupled Particle Dynamics and Flow Field Equations in Two-Phase Flows

ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels: Parts A and B ◽

10.1115/fedsm-icnmm2010-30443 ◽

2010 ◽

Author(s):

R. Kamali ◽

S. A. Shekoohi

Keyword(s):

Flow Field ◽

Particle Dynamics ◽

Fluid Particle ◽

Navier Stokes ◽

Test Cases ◽

Particle Interactions ◽

Field Equations ◽

Two Phase ◽

Coupled Equations ◽

Solution Accuracy

Two methods for solving coupled particle dynamics and flow field equations simultaneously by considering fluid-particle interactions to simulate two-phase flow are presented and compared. In many conditions, such as magnetic micro mixers and shooting high velocity particles in fluid, the fluid-particle interactions can not be neglected. In these cases it is necessary to consider fluid-particle interactions and solve the related coupled equations simultaneously. To solve these equations, suitable algorithms should be used to improve convergence speed and solution accuracy. In this paper two algorithms for solving coupled incompressible Navier-Stokes and particle dynamics equations are proposed and their efficiencies are compared by using them in a computer program. The main criterion that is used for comparison is the time they need to converge for a specific accuracy. In the first algorithm the particle dynamics and flow field equations are solved simultaneously but separately. In the second algorithm in each iteration for solving flow field equations, the particle dynamics equation is also solved. Results for some test cases are presented and compared. According to the results the second algorithm is faster than the first one especially when there is a strong coupling between phases.

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Experimental and Numerical Investigation of Preferential Flow in Fractured Network with Clogging Process

Mathematical Problems in Engineering ◽

10.1155/2014/879189 ◽

2014 ◽

Vol 2014 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Xiaobing Chen ◽

Jian Zhao ◽

Li Chen

Keyword(s):

Velocity Field ◽

Cross Sections ◽

Preferential Flow ◽

Pressure Head ◽

Fracture Network ◽

Navier Stokes ◽

Single Fracture ◽

Navier Stokes Equation ◽

Physical Experiments ◽

Fractured Network

In this study, physical experiments and numerical simulations are combined to provide a detailed understanding of flow dynamics in fracture network. Hydraulic parameters such as pressure head, velocity field, Reynolds number on certain monitoring cross points, and total flux rate are examined under various clogging conditions. Applying the COMSOL Multiphysics code to solve the Navier-Stokes equation instead of Reynolds equation and using the measured data to validate the model, the fluid flow in the horizontal 2D cross-sections of the fracture network was simulated. Results show that local clogging leads to a significant reshaping of the flow velocity field and a reduction of the transport capacity of the entire system. The flow rate distribution is highly influenced by the fractures connected to the dominant flow channels, although local disturbances in velocity field are unlikely to spread over the whole network. Also, modeling results indicate that water flow in a fracture network, compared with that in a single fracture, is likely to transit into turbulence earlier under the same hydraulic gradient due to the influence of fracture intersections.

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3D modelling of the flow distribution in the delta of Lake Øyeren, Norway

Hydrology Research ◽

10.2166/nh.2010.018 ◽

2010 ◽

Vol 41 (2) ◽

pp. 92-103 ◽

Cited By ~ 2

Author(s):

Peggy Zinke ◽

Nils Reidar Bøe Olsen ◽

Jim Bogen ◽

Nils Rüther

Keyword(s):

Water Level ◽

Cross Sections ◽

Stokes Equations ◽

Morphological Changes ◽

Flow Distribution ◽

Field Measurements ◽

Navier Stokes ◽

Error Sources ◽

Navier Stokes Equations ◽

Water Level Measurements

A 3D numerical model was used to compute the discharge distribution in the channel branches of Lake Øyeren's delta in Norway. The model solved the Navier–Stokes equations with the k–ɛ turbulence model on a 3D unstructured grid. The bathymetry dataset for the modelling had to be combined from different data sources. The results for three different flow situations in 1996 and 1997 showed a relative accuracy of the computed discharges within the range of 0 to±20% compared with field measurements taken by an ADCP at 13 cross sections of the distributary channels. The factors introducing the most error in the computed results are believed to be uncertainties concerning the bathymetry. A comparison between the computational results of the older morphology data from 1985–1990 and the model morphology from 1995–2004 indicated that morphological changes in this period had already had consequences for the flow distribution in some channels. Other important error sources were the inevitable use of averaged water level gradients because of unavailable water level measurements within the delta.

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Numerical Simulation of Clocking Effect on Wake Transportation and Interaction in a 1.5-Stage Axial Turbine

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2010-22783 ◽

2010 ◽

Cited By ~ 1

Author(s):

Wei Li ◽

Hua Ouyang ◽

Zhao-hui Du

Keyword(s):

Stokes Equations ◽

Three Dimensional ◽

Leading Edge ◽

Navier Stokes ◽

Maximum Efficiency ◽

Suction Surface ◽

Navier Stokes Equations ◽

Pressure Surface ◽

Turbine Efficiency ◽

Small Influence

To give insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has a very small influence on the turbine efficiency in this investigation. The efficiency difference between the maximum and minimum configuration is nearly 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passed through the mid-channel in the 2nd stator.

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Accumulation studies at specific sampling areas of the active floodplain in the Upper-Tisza region

Landscape & Environment ◽

10.21120/le/11/1/2 ◽

2017 ◽

Vol 11 (1) ◽

pp. 14-22

Author(s):

Gábor Molnár ◽

Andor Scholtz ◽

Róbert Vass

Keyword(s):

Surface Roughness ◽

Cross Sections ◽

Accumulation Rate ◽

Base Point ◽

Accumulation Rates ◽

Areal Distribution ◽

River Bed ◽

Rate Of Accumulation

In this paper the rate of accumulation was studied along four VO floodplain cross sections of the UpperTisza region between 1974 and 2014. VO floodplain cross sections are based on a mapping base-point grid (established in 1890), and they are located a few kilometers from each other. Furthermore, the roughness changes of different surface types, crossed by the VO floodplain cross-sections, were also determined between 1965 and 2015. The accumulation studies were extended to include the accumulation rates of the cut off meanders located along and/or close to the VO cross-sections. The roughness values increased in all four floodplain VO cross-sections since 1965; in two of them it reached or approximated 100 %. The average accumulation along the VO cross-sections was between 28 and 47 cm (0.73–1.23 cm/year) during the 38-year period. However, its areal distribution showed large differences. The highest values (169–309 cm, i.e. 4.44–8.13 cm/year) were found at the lowest points of the cut off meanders and swales in every case. The accumulation rate of the examined three cut off meanders near the floodplain cross-sections (140 and 1570 meters from the river bed) was lower (0.84–2.5 cm/year), but the study period was significantly longer (154 and 161 years, respectively). Comparing the values of the two periods, it is obvious that the accumulation of the active floodplain accelerates, presumably due to the significant increase of surface roughness.

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