The Influence of Variable Gas Properties on Turbomachinery CFD

2005 ◽  
Author(s):  
John D. Northall
Keyword(s):  
Current Model ◽  
Navier Stokes ◽  
Large Temperature ◽  
Specific Heats ◽  
Cfd Models ◽  
Multi Stage ◽  
Polynomial Curve ◽  
Radial Profiles ◽  
Cooling Air ◽  
Gas Properties

This paper describes the inclusion of variable gas properties within a Reynolds average Navier-Stokes solver for turbomachinery and its application to multi-stage turbines. Most current turbomachinery CFD models the gas as perfect with constant specific heats. However, the specific heat at constant pressure, CP, can vary significantly. This is most marked in the turbine where large variations of temperature are combined with variations in the fuel air ratio. In the current model CP is computed as a function of the local temperature and fuel air ratio using polynomial curve fits to represent the real gas behaviour. The importance of variable gas properties is assessed by analysing a multi-stage turbine typical of the core stages of a modern aero-engine. This calculation includes large temperature variations due to radial profiles at inlet, the addition of cooling air and work extraction through the machine. The calculation also includes local variations in fuel-air ratio resulting from the inlet profile and the dilution of the mixture by the addition of coolant air. A range of gas models is evaluated. The addition of variable gas properties is shown to have no significant effect on the convergence of the algorithm, and the extra computational costs are modest. The models are compared with emphasis on the parameters of importance in turbine design, such as capacity, work and efficiency.

The Influence of Variable Gas Properties on Turbomachinery Computational Fluid Dynamics

2005 ◽  
Vol 128 (4) ◽  
pp. 632-638 ◽  
Author(s):  
John D. Northall
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Current Model ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Large Temperature ◽  
Specific Heats ◽  
Cfd Models ◽  
Radial Profiles ◽  
Gas Properties

This paper describes the inclusion of variable gas properties within a Reynolds average Navier-Stokes solver for turbomachinery and its application to multistage turbines. Most current turbomachinery computational fluid dynamics (CFD) models the gas as perfect with constant specific heats. However, the specific heat at constant pressure CP can vary significantly. This is most marked in the turbine where large variations of temperature are combined with variations in the fuel air ratio. In the current model CP is computed as a function of the local temperature and fuel air ratio using polynomial curve fits to represent the real gas behavior. The importance of variable gas properties is assessed by analyzing a multistage turbine typical of the core stages of a modern aeroengine. This calculation includes large temperature variations due to radial profiles at inlet, the addition of cooling air, and work extraction through the machine. The calculation also includes local variations in fuel air ratio resulting from the inlet profile and the dilution of the mixture by the addition of coolant air. A range of gas models is evaluated. The addition of variable gas properties is shown to have no significant effect on the convergence of the algorithm, and the extra computational costs are modest. The models are compared with emphasis on the parameters of importance in turbine design, such as capacity, work, and efficiency. Overall the effect on turbine performance prediction of including variable gas properties in three-dimensional CFD is found to be small.

Modeling of Compressor Drum Cavities With Radial Inflow

2016 ◽  
Author(s):  
D. Amirante ◽  
Z. Sun ◽  
J. W. Chew ◽  
N. J. Hills ◽  
N. R. Atkins
Keyword(s):  
Thermal Stratification ◽  
Turbulence Modeling ◽  
Navier Stokes ◽  
Inflow Rate ◽  
Cfd Models ◽  
Flow And Heat Transfer ◽  
Rotating Discs ◽  
Computational Fluid Dynamics Cfd ◽  
Inlet Conditions ◽  
Cooling Air

Reynolds-Averaged Navier-Stokes (RANS) computations have been conducted to investigate the flow and heat transfer between two co-rotating discs with an axial throughflow of cooling air and a radial bleed introduced from the shroud. The computational fluid dynamics (CFD) models have been coupled with a thermal model of the test rig, and the predicted metal temperature compared with the thermocouple data. CFD solutions are shown to vary from a buoyancy driven regime to a forced convection regime, depending on the radial inflow rate prescribed at the shroud. At a high radial inflow rate, the computations show an excellent agreement with the measured temperatures through a transient rig condition. At a low radial inflow rate, the cavity flow is destabilized by the thermal stratification. Good qualitative agreement with the measurements is shown, although a significant over-prediction of disc temperatures is observed. This is associated with under prediction of the penetration of the axial throughflow into the cavity. The mismatch could be the result of strong sensitivity to the prescribed inlet conditions, in addition to possible shortcomings in the turbulence modeling.

Numerical Study of Deterministic Fluxes in Compressor Passages

2018 ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Navier Stokes ◽  
Design Stage ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Multi Stage ◽  
Radial Profiles ◽  
Stage Matching ◽  
Unsteady Effects

Computational Fluid Dynamics (CFD) has been widely adopted at the compressor design process, but it remains a challenge to predict the flow details, performance and stage matching for multi-stage, high-speed machines accurately. The Reynolds Averaged Navier-Stokes (RANS) simulation with mixing plane for bladerow coupling is still the workhorse in the industry and the unsteady bladerow interaction is discarded. This paper examines these discarded unsteady effects via deterministic fluxes using semi-analytical and URANS calculations. The study starts from a planar duct under periodic perturbations. The study shows that under large perturbations, the mixing plane produces dubious mixed-out variables, e.g. whirl angle. The performance of the mixing plane can be considerably improved by including deterministic fluxes into the mixing plane formulation. This demonstrates the effect of deterministic fluxes at the bladerow interface. Furthermore the front stages of a 19-blade row compressor are investigated and URANS solutions are compared with RANS solutions. The magnitude of divergence of Reynolds stresses and deterministic stresses are compared. The effect of deterministic fluxes are demonstrated on whirl angle and radial profiles of total pressure and so on. The enhanced spanwise mixing due to deterministic fluxes are also observed. The effect of deterministic fluxes are confirmed via the non-linear harmonic method which includes the deterministic fluxes in the mean flow and the study of multistage compressor shows that unsteady effects, which are quantified by deterministic fluxes, are indispensable to have credible predictions of the flow details and performance of compressor even at its design stage.

Continuous adjoint aerodynamic optimization design for multi-stage gas turbine with cooling air

2017 ◽  
Vol 89 (3) ◽  
pp. 444-456
Author(s):  
Lei Chen ◽  
Jiang Chen
Keyword(s):  
Gas Turbine ◽  
Optimization Design ◽  
Adjoint Method ◽  
Air Injection ◽  
Aerodynamic Optimization ◽  
Content Type ◽  
Multi Stage ◽  
Surface Code ◽  
Cooling Air ◽  
Continuous Adjoint

Purpose This paper aims to conduct the optimization of the multi-stage gas turbine with the effect of the cooling air injection based on the adjoint method. Design/methodology/approach Continuous adjoint method is combined with the S2 surface code. Findings The optimization of the stagger angles, stacking lines and the passage can improve the attack angles and restrain the development of the boundary, reducing the secondary flow loss caused by the cooling air injection. Practical implications The aerodynamic performance of the gas turbine can be improved via the optimization of blade and passage based on the adjoint method. Originality/value The results of the first study on the adjoint method applied to the S2 surface through flow calculation including the cooling air effect are presented.

scholarly journals Multi-stage nozzle-shape optimization for pulsed hydrogen–air detonation combustor

2017 ◽  
Vol 9 (2) ◽  
pp. 168781401769095 ◽  
Author(s):  
Francesco Ornano ◽  
James Braun ◽  
Bayindir Huseyin Saracoglu ◽  
Guillermo Paniagua
Keyword(s):  
Steady Flow ◽  
Combustion Process ◽  
Differential Evolution Algorithm ◽  
Three Dimensions ◽  
Sudden Expansion ◽  
Navier Stokes ◽  
Optimization Strategy ◽  
Detonation Products ◽  
Multi Stage ◽  
Reynolds Averaged Navier Stokes

Thermal engines based on pressure gain combustion offer new opportunities to generate thrust with enhanced efficiency and relatively simple machinery. The sudden expansion of detonation products from a single-opening tube yields thrust, although this is suboptimal. In this article, we present the complete design optimization strategy for nozzles exposed to detonation pulses, combining unsteady Reynolds-averaged Navier–Stokes solvers with the accurate modeling of the combustion process. The parameterized shape of the nozzle is optimized using a differential evolution algorithm to maximize the force at the nozzle exhaust. The design of experiments begins with a first optimization considering steady-flow conditions, subsequently followed by a refined optimization for transient supersonic flow pulse. Finally, the optimized nozzle performance is assessed in three dimensions with unsteady Reynolds-averaged Navier–Stokes capturing the deflagration-to-detonation transition of a stoichiometric, premixed hydrogen–air mixture. The optimized nozzle can deliver 80% more thrust than a standard detonation tube and about 2% more than the optimized results assuming steady-flow operation. This study proposes a new multi-fidelity approach to optimize the design of nozzles exposed to transient operation, instead of the traditional methods proposed for steady-flow operation.

1995 ASME Gas Turbine Award Paper: Development and Application of a Multistage Navier–Stokes Solver: Part I—Multistage Modeling Using Bodyforces and Deterministic Stresses

1998 ◽  
Vol 120 (2) ◽  
pp. 205-214 ◽  
Author(s):  
C. M. Rhie ◽  
A. J. Gleixner ◽  
D. A. Spear ◽  
C. J. Fischberg ◽  
R. M. Zacharias
Keyword(s):  
Stokes Equations ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Design Procedure ◽  
Potential Interaction ◽  
Theoretical Development ◽  
Navier Stokes ◽  
Radial Profiles ◽  
Compressor Performance ◽  
High Level

A multistage compressor performance analysis method based on the three-dimensional Reynolds-averaged Navier-Stokes equations is presented in this paper. This method is an average passage approach where deterministic stresses are used to ensure continuous physical properties across interface planes. The average unsteady effects due to neighboring blades and/or vanes are approximated using deterministic stresses along with the application of bodyforces. Bodyforces are used to account for the “potential” interaction between closely coupled (staged) rows. Deterministic stresses account for the “average” wake blockage and mixing effects both axially and radially. The attempt here is to implement an approximate technique for incorporating periodic unsteady flow physics that provides for a robust multistage design procedure incorporating reasonable computational efficiency. The present paper gives the theoretical development of the stress/bodyforce models incorporated in the code, and demonstrates the usefulness of these models in practical compressor applications. Compressor performance prediction capability is then established through a rigorous code/model validation effort using the power of networked workstations. The numerical results are compared with experimental data in terms of one-dimensional performance parameters such as total pressure ratio and circumferentially averaged radial profiles deemed critical to compressor design. This methodology allows the designer to design from hub to tip with a high level of confidence in the procedure.

scholarly journals Flow and windage due to bolts on a rotating disc

2016 ◽  
Vol 231 (15) ◽  
pp. 2925-2941
Author(s):  
Sulfickerali Noor Mohamed ◽  
John Chew ◽  
Nick Hills
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Time Dependent ◽  
Navier Stokes ◽  
Rotating Disc ◽  
Rotating Machine ◽  
Flow Features ◽  
Rotor Surface ◽  
Dynamics Simulations ◽  
Cooling Air

The cooling air in a rotating machine is subject to windage as it passes over the rotor surface, particularly for cases where nonaxisymmetric features such as boltheads are encountered. The ability to accurately predict windage can help reduce the quantity of cooling air required, resulting in increased efficiency. Previous work has shown that the steady computational fluid dynamics solutions can give reasonable predictions for the effects of bolts on disc moment for a rotor–stator cavity with throughflow but flow velocities and disc temperature are not well predicted. Large fluctuations in velocities have been observed experimentally in some cases. Time-dependent computational fluid dynamics simulations reported here bring to light the unsteady nature of the flow. Unsteady Reynolds-averaged Navier–Stokes calculations for 120° and 360° models of the rotor–stator cavity with 9 and 18 bolts were performed in order to better understand the flow physics. Although the rotor–stator cavity with bolts is geometrically steady in the rotating frame of reference, it was found that the bolts generate unsteadiness which creates time-dependent rotating flow features within the cavity. At low throughflow conditions, the unsteady flow significantly increases the average disc temperature.

Numerical Study of Deterministic Fluxes in Compressor Passages

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Navier Stokes ◽  
Design Stage ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Radial Profiles ◽  
And Performance ◽  
Stage Matching ◽  
Unsteady Effects

Computational fluid dynamics (CFD) has been widely adopted in the compressor design process, but it remains a challenge to predict the flow details, performance, and stage matching for multistage, high-speed machines accurately. The Reynolds Averaged Navier-Stokes (RANS) simulation with mixing plane for bladerow coupling is still the workhorse in the industry and the unsteady bladerow interaction is discarded. This paper examines these discarded unsteady effects via deterministic fluxes using semi-analytical and unsteady RANS (URANS) calculations. The study starts from a planar duct under periodic perturbations. The study shows that under large perturbations, the mixing plane produces dubious values of flow quantities (e.g., whirl angle). The performance of the mixing plane can be considerably improved by including deterministic fluxes into the mixing plane formulation. This demonstrates the effect of deterministic fluxes at the bladerow interface. Furthermore, the front stages of a 19-blade row compressor are investigated and URANS solutions are compared with RANS mixing plane solutions. The magnitudes of divergence of Reynolds stresses (RS) and deterministic stresses (DS) are compared. The effect of deterministic fluxes is demonstrated on whirl angle and radial profiles of total pressure and so on. The enhanced spanwise mixing due to deterministic fluxes is also observed. The effect of deterministic fluxes is confirmed via the nonlinear harmonic (NLH) method which includes the deterministic fluxes in the mean flow, and the study of multistage compressor shows that unsteady effects, which are quantified by deterministic fluxes, are indispensable to have credible predictions of the flow details and performance of compressor even at its design stage.

Novel Performance Prediction of a Transonic 4.5 Stage Compressor

2012 ◽  
Author(s):  
Andreas Schmitz ◽  
Marcel Aulich ◽  
Dirk Schönweitz ◽  
Eberhard Nicke
Keyword(s):  
Performance Prediction ◽  
Three Dimensions ◽  
Navier Stokes ◽  
3D Flow ◽  
3D Design ◽  
New Approach ◽  
Multi Stage ◽  
Compressor Design ◽  
Basic Parameters ◽  
Flow Effects

Computing capacities have grown exponentially in recent years and 3D-Navier-Stokes methods were developed widely. However it is still not feasible to design a multi-stage compressor directly in three dimensions. Instead, compressor design starts with 1D-design. In accordance with this approach, basic parameters such as the number of stages and stage pressure ratios are determined. In the following 2D-design, the geometry of the flow channel and the main parameters of the blade geometries can be determined. Afterwards in the 3D-design, unsteady and 3D-flow-effects are considered and the design optimized accordingly. Therefore, it is virtually impossible to correct conceptual faults in the 3D-design phase. Thus a robust and reliable 2D-Throughflow-solver including a performance prediction for modern airfoil geometries is necessary. So far there is no efficient methodology known which predicts the performance for all kinds of airfoil geometries, as it would be necessary in a 2D-Throughflow optimization process. In [1, 2] a novel methodology was presented, which is able to predict the performance for a large number of airfoil geometries accurately. This method is based on a large airfoil database which is used to train a surrogate model for airfoil performance prediction. The scope of this work is to validate and to document the progress of this new approach. In Schmitz et al. [1] it was validated on rotor 1 of the 4.5 stage transonic test compressor DLR-RIG250 of the Institute of Propulsion Technology. In this work all 4.5 stages were calculated at different speedlines and different vane positions. The results of the S2-solver are compared to experimental data and 3D-CFD calculations, obtained using the DLR in-house solver TRACE.

scholarly journals A Rapid Approximate Method of Determining Axial-Flow Turbine Disk and Blade Temperatures

1967 ◽  
Author(s):  
F. M. Simpson
Keyword(s):  
Numerical Solution ◽  
Approximate Method ◽  
Temperature Profile ◽  
Computer Programming ◽  
Journal Bearing ◽  
Axial Flow ◽  
Turbine Disk ◽  
Multi Stage ◽  
Hand Calculation ◽  
Cooling Air

A method of determining the temperature profile of a single-stage axial-flow turbine disk with uncooled blades is presented. The blade temperature is also estimated. Information required for the solution is: the gas properties and velocity entering the rotor, the blade and disk geometry, the blade fastening geometry, and the disk-to-shaft attachment geometry. Impingement disk cooling may be used. The temperature of the shaft at a point near the journal bearing mutt be assumed, but it is shown that this assumption is not critical. A stepwise numerical solution, suitable for either hand calculation or computer programming, is employed. The method may be extended to multi-stage turbines. A typical example is given and the effect of changing the radius of injection of the disk cooling air is shown.

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