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.

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

2020 ◽  
Author(s):  
José Ramón Serrano ◽  
Francisco José Arnau Martínez ◽  
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 radial inflow dual-volute turbines, their characteristic maps and fully predictive modelling using 1D gas dynamic codes are not well established yet. The complexity of the 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 a 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. Here, also described are two innovative 0D mean-line models 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 admission conditions using as inputs: the mass flow ratio between branches; the total temperature ratio between branches; the blade to jet speed ratio in each branch 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.

3-D Time Domain Unsteady Computation of Rotating Instability in Steam Turbine Last Stage

2012 ◽  
Author(s):  
L. Y. Zhang ◽  
L. He ◽  
H. Stüer
Keyword(s):  
Mass Flow ◽  
Large Scale ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Steam Turbines ◽  
Flow Conditions ◽  
Frequency Pattern ◽  
Last Stage ◽  
Rotating Instability

The rotating instability phenomenon in a last stage of steam turbines at low mass flow conditions has been previously identified experimentally. Recently, the rotating instability has also been numerically studied in a whole annulus domain on 2D blade sections. In the present work, 3D simulations of unsteady flows are carried out on two model steam turbines over a range of mass flow conditions. The pressure-ratio volume-flow characteristics in rotor row tip region under different flow conditions are well captured in the computations in comparison with the experiment. The effect of blade scaling is examined to identify the influence of changing blade counts for a circumferential domain reduction, showing relatively small effects on the overall performance characteristics. The present 3D unsteady solutions on a reduced multi-passage domain have been able to predict a rotating instability in the rotor blade tip region, in accord with the corresponding experiment. Further Fourier analysis is carried out to examine the frequency pattern and spatial modal features. The 3D flow behavior is highlighted by comparison between the 3D and 2D calculations. The present results seem to suggest that the rotating instability onset in the rotor tip region is largely independent of the large scale flow separation in the downstream diffusor.

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.

Effect of a volute on the unsteady flow in the vane diffuser of a centrifugal compressor

2016 ◽  
Vol 230 (8) ◽  
pp. 773-791 ◽  
Author(s):  
Gong W Qi ◽  
X Hong Zhang
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
High Mass ◽  
Flow Conditions ◽  
Asymmetric Component ◽  
Unsteady Loading ◽  
Vane Diffuser

A volute is the only circumferential asymmetric component in a centrifugal compressor, and thus, it should account for the circumferential asymmetry of the flow in a vane diffuser. This study performs a transient numerical analysis to investigate the effect of a volute on the flow in the vane diffuser of a centrifugal compressor under three operating conditions (near-stall, middle, and high mass flow). We compare numerical and experimental performance of the compressor, including polytropic efficiency, total pressure ratio, and unsteady pressure on a diffuser vane. The numerical scheme is proven valid owing to the fact that the numerical and experimental results considerably agree well with each other. Under middle and high mass flow conditions, the time-averaged static pressure recovery and the total pressure loss coefficients for all the diffuser passages indicate that the performance of the passages near and upstream of the volute tongue is affected negatively by the volute, whereas that of the passages downstream of the volute tongue is less affected. Under near-stall condition, the performance of all the passages is disturbed, and the diffuser passage marked as DP 3 demonstrates the worst performance. Investigation on the time-averaged aerodynamic forces, loading, and pressure on the vanes yields results that are consistent with those of the investigation on the performance of the passages. The harmonics with 0.5 fb and fb, which are included in the unsteady loading and pressure on the pressure and suction sides of the vanes, are dominant, where fb is the impeller main and splitter blades passing frequency. Their amplitude values increase as mass flow deviates from the middle mass flow condition. Under middle and high mass flow conditions, the harmonic with 0.5 fb is affected more negatively because of the larger amplitude on the vanes near and upstream of the volute tongue than those downstream, whereas the harmonic with fb is less affected by the volute. Under the near-stall condition, the transient vorticity fields along with the harmonics of 0.5 fb and fb are investigated to evaluate the performance of the diffuser passages. DP 3, which is located at approximately 90° downstream of the volute tongue, suffers the strongest flow deterioration and is inferred to stall first. Further researches for designing more matching diffuser/volute combination will be performed by referring this study.

scholarly journals Evolution of mass flow and total temperature pulsations in flat-plate and swept-wing boundary layers at Mach 2 and 2.5

2020 ◽  
Vol 1677 ◽  
pp. 012033
Author(s):  
A A Yatskikh ◽  
A D Kosinov ◽  
N V Semionov ◽  
Y G Ermolaev ◽  
A V Panina ◽  
...  
Keyword(s):  
Flat Plate ◽  
Boundary Layers ◽  
Mass Flow ◽  
Swept Wing ◽  
Temperature Pulsations ◽  
Total Temperature

scholarly journals Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Blanke ◽  
Markus Hagenkamp ◽  
Bernd Döring ◽  
Joachim Göttsche ◽  
Vitali Reger ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Circular Ring ◽  
Flow Conditions ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

Turbocharger-Design Effects on Gasoline-Engine Performance

2005 ◽  
Vol 127 (3) ◽  
pp. 525-530 ◽  
Author(s):  
Theodosios Korakianitis ◽  
T. Sadoi
Keyword(s):  
Steady Flow ◽  
Mass Flow ◽  
Gasoline Engine ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Final Choice ◽  
Design Point ◽  
Theoretical Considerations ◽  
Flow Experiments

Specification of a turbocharger for a given engine involves matching the turbocharger performance characteristics with those of the piston engine. Theoretical considerations of matching turbocharger pressure ratio and mass flow with engine mass flow and power permits designers to approach a series of potential turbochargers suitable for the engine. Ultimately, the final choice among several candidate turbochargers is made by tests. In this paper two types of steady-flow experiments are used to match three different turbochargers to an automotive turbocharged-intercooled gasoline engine. The first set of tests measures the steady-flow performance of the compressors and turbines of the three turbochargers. The second set of tests measures the steady-flow design-point and off-design-point engine performance with each turbocharger. The test results show the design-point and off-design-point performance of the overall thermodynamic cycle, and this is used to identify which turbocharger is suitable for different types of engine duties.

Performance of Strongly Bowed Stators in a Four-Stage High-Speed Compressor

2004 ◽  
Vol 126 (3) ◽  
pp. 333-338 ◽  
Author(s):  
Axel Fischer ◽  
Walter Riess ◽  
Joerg R. Seume
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Maximum Pressure ◽  
Controlled Diffusion ◽  
Stage 4 ◽  
The University

The FVV sponsored project “Bow Blading” (cf. acknowledgments) at the Turbomachinery Laboratory of the University of Hannover addresses the effect of strongly bowed stator vanes on the flow field in a four-stage high-speed axial compressor with controlled diffusion airfoil (CDA) blading. The compressor is equipped with more strongly bowed vanes than have previously been reported in the literature. The performance map of the present compressor is being investigated experimentally and numerically. The results show that the pressure ratio and the efficiency at the design point and at the choke limit are reduced by the increase in friction losses on the surface of the bowed vanes, whose surface area is greater than that of the reference (CDA) vanes. The mass flow at the choke limit decreases for the same reason. Because of the change in the radial distribution of axial velocity, pressure rise shifts from stage 3 to stage 4 between the choke limit and maximum pressure ratio. Beyond the point of maximum pressure ratio, this effect is not distinguishable from the reduction of separation by the bow of the vanes. Experimental results show that in cases of high aerodynamic loading, i.e., between maximum pressure ratio and the stall limit, separation is reduced in the bowed stator vanes so that the stagnation pressure ratio and efficiency are increased by the change to bowed stators. It is shown that the reduction of separation with bowed vanes leads to a increase of static pressure rise towards lower mass flow so that the present bow bladed compressor achieves higher static pressure ratios at the stall limit.

Mathematical Analysis for Off-Design Performance of Cryogenic Turboexpander

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Subrata K. Ghosh ◽  
R. K. Sahoo ◽  
Sunil K. Sarangi
Keyword(s):  
Pressure Ratio ◽  
Expansion Ratio ◽  
Flow Conditions ◽  
Flow Properties ◽  
Dimensional Solution ◽  
One Dimensional ◽  
Design Performance ◽  
Fluid Properties ◽  
The Mean ◽  
Inlet Conditions

A study has been conducted to determine the off-design performance of cryogenic turboexpander. A theoretical model to predict the losses in the components of the turboexpander along the fluid flow path has been developed. The model uses a one-dimensional solution of flow conditions through the turbine along the mean streamline. In this analysis, the changes of fluid and flow properties between different components of turboexpander have been considered. Overall, turbine geometry, pressure ratio, and mass flow rate are input information. The output includes performance and velocity diagram parameters for any number of given speeds over a range of turbine pressure ratio. The procedure allows any arbitrary combination of fluid species, inlet conditions, and expansion ratio since the fluid properties are properly taken care of in the relevant equations. The computational process is illustrated with an example.

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