COMPARISON OF EXPERIMENTAL, 3D AND 1D MODEL FOR A MIXED-FLOW TURBINE UNDER PULSATING FLOW CONDITIONS

2015 ◽  
Vol 77 (8) ◽  
Author(s):  
Meng Soon Chiong ◽  
Muhamad Hasbullah Padzillah ◽  
Srithar Rajoo ◽  
Alessandro Romagnoli ◽  
Aaron W. Costall ◽  
...  
Keyword(s):  
3D Models ◽  
Cfd Model ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Pulse Flow ◽  
Power Characteristics ◽  
Engine Model ◽  
Single Entry ◽  
1D Model ◽  
Swallowing Capacity

The pulse flow performance of a turbocharger turbine is known to be different than its corresponding steady flow performance. This often leads to less-than-satisfactory 1D engine model prediction. In this study, the effectiveness of a 1D pulse flow turbine model is assessed against experimental data with the aid of 3D CFD model. The turbine under study is a single-entry variable geometry mixed-flow turbine. The result shows highly comparable pulse flow swallowing capacity and actual power characteristics between 1D and 3D models. The over-prediction in 1D actual power magnitude is found to be due to the simplification of combining nozzle and rotor stage pressure loss together.

Unsteady Performance Prediction of a Single Entry Mixed Flow Turbine Using 1-D Gas Dynamic Code Extended With Meanline Model

2012 ◽  
Author(s):  
Meng Soon Chiong ◽  
Srithar Rajoo ◽  
Alessandro Romagnoli ◽  
Ricardo Martinez-Botas
Keyword(s):  
Performance Prediction ◽  
Computational Models ◽  
Power Prediction ◽  
Mixed Flow ◽  
Pulse Flow ◽  
Turbine Performance ◽  
Gas Dynamic ◽  
Wide Range ◽  
Single Entry ◽  
Turbine Model

Turbochargers are widely regarded as one of the most promising enabling technology for engine downsizing, in the aim to achieve better specific fuel consumption, thermal efficiency and most importantly carbon reduction. The increasing demand for higher quality engine-turbocharger matching, leads to the development of computational models capable of predicting the unsteady behaviour of a turbocharger turbine when subjected to pulsating inlet flow. Due to the wide range of engine loads and speed variations, an automotive turbocharger turbine model must be able to render all the frequency range of a typical exhaust pulse flow. A purely one-dimensional (1-D) turbine model is capable of good unsteady swallowing capacity prediction, provided it is accurately validated. However, the unsteady turbine power evaluation still heavily relies on the quasi-steady assumption. On the other hand, meanline model is capable of resolving the turbine work output but it is limited to steady state flow due to its zero dimensional nature. This paper explores an alternative methodology to realize turbine unsteady power prediction in 1-D by integrating these two independent modelling methods. A single entry mixed-flow turbine is first modelled using 1-D gas dynamic method to solve the unsteady flow propagation in turbine volute while the instantaneous turbine power is subsequently evaluated using a mean-line model. The key in the effectiveness of this methodology relies on the synchronization of the flow information with different time-scales. In addition to the turbine performance parameters, the common level of unsteadiness was also compared based on the Strouhal number evaluations. Comparison of the quasi-steady assumption using the experiment results was made in order to further understand the strength and weaknesses of corresponding method in unsteady turbine performance prediction. The outcomes of the simulation showed a good agreement in the shape and trend profile for the instantaneous turbine power. Meanwhile the predicted cycle-averaged value indicates a positive potential of the current turbine model to be expanded to a whole engine simulation after few minor improvements.

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.

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.

scholarly journals 3D spectroscopic analysis of helium-line white dwarfs

2020 ◽  
Author(s):  
Elena Cukanovaite ◽  
Pier-Emmanuel Tremblay ◽  
Pierre Bergeron ◽  
Bernd Freytag ◽  
Hans-Günter Ludwig ◽  
...  
Keyword(s):  
Effective Temperature ◽  
White Dwarfs ◽  
Energy Transport ◽  
3D Models ◽  
Spectroscopic Technique ◽  
Surface Gravity ◽  
Atmospheric Models ◽  
Physical Treatment ◽  
Spectroscopic Parameters ◽  
1D Model

Abstract In this paper, we present corrections to the spectroscopic parameters of DB and DBA white dwarfs with −10.0 ≤ log (H/He) ≤−2.0, 7.5 ≤ log g ≤9.0 and 12 000 K ≲ Teff ≲ 34 000 K, based on 282 3D atmospheric models calculated with the CO5BOLD radiation-hydrodynamics code. These corrections arise due to a better physical treatment of convective energy transport in 3D models when compared to the previously available 1D model atmospheres. By applying the corrections to an existing SDSS sample of DB and DBA white dwarfs, we find significant corrections both for effective temperature and surface gravity. The 3D log g corrections are most significant for Teff ≲ 18, 000 K, reaching up to −0.20 dex at log g = 8.0. However, in this low effective temperature range, the surface gravity determined from the spectroscopic technique, can also be significantly affected by the treatment of the neutral van der Waals line broadening of helium and by non-ideal effects due to the perturbation of helium by neutral atoms. Thus, by removing uncertainties due to 1D convection, our work showcases the need for improved description of microphysics for DB and DBA model atmospheres. Overall, we find that our 3D spectroscopic parameters for the SDSS sample are generally in agreement with Gaia DR2 absolute fluxes within 1-3σ for individual white dwarfs. By comparing our results to DA white dwarfs, we determine that the precision and accuracy of DB/DBA atmospheric models are similar. For ease of user application of the correction functions, we provide an example Python code.

An Experimental and Modelling Strategy for Obtaining Complete Characteristic Maps of Dual-Volute Radial Inflow Turbines

2021 ◽  
Author(s):  
Jose R. Serrano ◽  
Francisco J. Arnau ◽  
Luis Miguel García-Cuevas ◽  
Vishnu Samala ◽  
Stephane Guilain ◽  
...  
Keyword(s):  
Mass Flow ◽  
Simple Procedure ◽  
Pressure Ratio ◽  
Predictive Modelling ◽  
Speed Ratio ◽  
Flow Conditions ◽  
Engine Exhaust ◽  
Additional Degree ◽  
Single Entry ◽  
Total Temperature

Abstract Despite the importance of turbocharged engines with dual-volute turbines, their characteristic maps and fully predictive modelling using 1D gas dynamic codes are not well established yet. The complexity of unsteady flow and the unequal admission of these turbines, when operating with pulses of engine exhaust gas, makes them a challenging system. This is mainly due to the unequal flow admission, which generates an additional degree of freedom with respect to well-known single entry vanned or vaneless turbines. This paper has as the main novelty a simple procedure for characterizing experimentally and elaborating characteristic maps of these turbines with unequal flow conditions. This method of analysis allows for easy interpolation within the proposed characteristic maps or conceiving simple models for calculating and extrapolating full performance parameters of dual-volute turbines. Two innovative 0D mean-line models are described that require a minimum quantity of experimental data for calibrating both: the mass flow parameter model and the isentropic efficiency model. Both models are predictive either in partial or unequal flow conditions using as inputs: the mass flow ratio and the total temperature ratio between branches; the blade speed ratio and the pressure ratio in each branch. These six inputs are generally instantaneously provided by 1D gas-dynamics codes. Therefore, the novelty of the model is its ability to be used in a quasi-steady way for dual volute turbines performance prediction. This can be done instantaneously when turbines are calculated operating at turbocharged engines under pulsating and unequal flow conditions.

Validation of a Mixed Flow Turbofan Performance Model in the Sub-Idle Operating Range

2003 ◽  
Author(s):  
Claus Riegler ◽  
Michael Bauer ◽  
Holger Schulte
Keyword(s):  
Steady State ◽  
Engine Performance ◽  
Performance Model ◽  
Maximum Power ◽  
Development Programs ◽  
Mixed Flow ◽  
Typical Application ◽  
Operating Range ◽  
Engine Model ◽  
Lighting Conditions

During turbofan development programs the evaluation of steady-state and transient engine performance is usually achieved by applying full thermodynamic engine models at least in the operating range between idle and maximum power conditions, but more recently also in the sub-idle operating range, e.g. for steady-state windmilling behavior and for starting, relight and shut down scenarios. The paper describes the setup, and in more detail the validation, of a full thermodynamic engine model for a two-spool mixed flow afterburner turbofan which is capable to run from maximum power down to zero speed and zero flow conditions in steady-state and transient mode. The validation is performed by using the model-based performance analysis procedure called ANSYN even in windmilling operation. Once the steady-state sub-idle model is validated the extension to transient sub-idle capability is achieved by simply adding the effects of rotor moment of inertia of the spools, while heat soakage effects are rather negligible without heat release in the burner. Especially lighting conditions in the burner are produced by such a validated sub-idle model inherently due to reliable data calculated at the burner entry station. The variety of applications of a validated full thermodynamic engine model is large. The performance data delivered is highly reliable and very consistent because the full operating range of the engine is covered with one model, and by appropriate means of speeding up the calculation even real-time capability may be achieved. In the paper synthesized data for an engine dry crank is compared to real engine test data as one typical application.

Droplet dynamics in mixed flow conditions: Effect of shear/elongation balance and viscosity ratio

2010 ◽  
Vol 54 (6) ◽  
pp. 1285-1306 ◽  
Author(s):  
Elia Boonen ◽  
Peter Van Puyvelde ◽  
Paula Moldenaers
Keyword(s):  
Viscosity Ratio ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Droplet Dynamics

Breakdown of Tip Leakage Vortices in Compressors at Flow Conditions Close to Stall

1997 ◽  
Author(s):  
Stefan Schlechtriem ◽  
Michael Lötzerich
Keyword(s):  
Vortex Breakdown ◽  
Stability Limit ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Stall Inception ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Flow Compressor ◽  
The Stability ◽  
Operating Points

The breakdown of tip leakage vortices at operating points close to the stability limit of transonic compressor rotors has been detected. The aerodynamic phenomenon is considered to have a major impact on stall inception. Computations have been carried out and a detailed visualization of the phenomenon is given. In addition the connection of vortex breakdown to rotating instabilities and stall is discussed. Furthermore the tip flow field of the axial rotor is compared to the results for a centrifugal and a mixed flow compressor operating at similar tip speeds.

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