Study on the Steady and Unsteady Aerodynamic Performance of a Radial Inflow Turbine With Small Partial Admission in a Miniature ORC System

2011 ◽  
Author(s):  
Ping Li ◽  
Jianhui Chen ◽  
Di Zhang ◽  
Yonghui Xie
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotational Speed ◽  
Rankine Cycle ◽  
Maximum Efficiency ◽  
Unsteady Aerodynamic ◽  
Radial Turbine ◽  
Partial Admission ◽  
Excitation Force ◽  
Radial Inflow Turbine

There is a great deal of residual heat under 350 °C being released into environment, without being used efficiently. Compared to the Rankine cycle with water as its working substance, it is effective to utilize Organic Rankine Cycle (ORC) to recover these waste heats. In the threshold of this paper, a miniature ORC system is proposed, and maximum efficiency of the system is achieved by means of optimal working substance. Moreover, numerical simulation of the partial admission (ε = 0.267) high rotational speed radial inflow turbine, which is the key unit in the system, is fulfilled. At the operating rotational speed of 60000 rpm and the proposed thermodynamic parameters, steady and unsteady flow field in the turbine are investigated with R11 as working fluid. The detailed parameters, such as axial force of rotor, power generated and thermal efficiency of the radial turbine, are analyzed. In addition, the unsteady flow pressure is integrated around the rotor blade profile to provide the unsteady aerodynamic blade force. And subsequently frequencies of unsteady disturbances and excitation force factors are obtained by spectrum analysis, which are of key importance for blade response analysis. The generation, development and dissipation process of the secondary flows, passage vortex and leakage vortex are observed in the flow channel. The results reveal that the partial admission greatly influences the parameters distributions in the flow field and the losses of radial turbine mainly occur at the frontier of the passage in the vicinity of blade root. As is discussed in the analysis of excitation force factor, the radial turbine is safe in the operation. The results discussed in this paper are beneficial for the sequent optimization and manufacture of the miniature turbine.

Numerical and Experimental Study of Unsteady Flow Field and Vibration in Radial Inflow Turbines

1999 ◽  
Vol 122 (2) ◽  
pp. 247-254 ◽  
Author(s):  
T. Kreuz-Ihli ◽  
D. Filsinger ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Transient Flow ◽  
Laser Doppler Anemometry ◽  
Mode Shapes ◽  
Detailed Knowledge ◽  
Test Rig ◽  
Aerodynamic Forces ◽  
Unsteady Aerodynamic ◽  
Radial Inflow Turbine

The blades of turbocharger impellers are exposed to unsteady aerodynamic forces, which cause blade vibrations and may lead to failures. An indispensable requirement for a safe design of radial inflow turbines is a detailed knowledge of the exciting forces. Up to now, only a few investigations relating to unsteady aerodynamic forces in radial turbines have been presented. To give a detailed insight into the complex phenomena, a comprehensive research project was initiated at the Institut fu¨r Thermische Stro¨mungsmaschinen, at the University of Karlsruhe. A turbocharger test rig was installed in the high-pressure, high-temperature laboratory of the institute. The present paper gives a description of the test rig design and the measuring techniques. The flow field in a vaneless radial inflow turbine was analyzed using laser-Doppler anemometry. First results of unsteady flow field investigations in the turbine scroll and unsteady phase-resolved measurements of the flow field in the turbine rotor will be discussed. Moreover, results from finite element calculations analyzing frequencies and mode shapes are presented. As vibrations in turbines of turbochargers are assumed to be predominantly excited by unsteady aerodynamic forces, a method to predict the actual transient flow in a radial turbine utilizing the commercial Navier–Stokes solver TASCflow3d was developed. Results of the unsteady calculations are presented and comparisons with the measured unsteady flow field are made. As a major result, the excitation effect of the tongue region in a vaneless radial inflow turbine can be demonstrated. [S0889-504X(00)01402-1]

Numerical and Experimental Study of Unsteady Flow Field and Vibration in Radial Inflow Turbines

1999 ◽  
Author(s):  
T. Kreuz-Ihli ◽  
D. Filsinger ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Transient Flow ◽  
Laser Doppler Anemometry ◽  
Mode Shapes ◽  
Detailed Knowledge ◽  
Test Rig ◽  
Aerodynamic Forces ◽  
Unsteady Aerodynamic ◽  
Radial Inflow Turbine

The blades of turbocharger impellers are exposed to unsteady aerodynamic forces, which cause blade vibrations and may lead to failures. An indispensable requirement for a safe design of radial inflow turbines is a detailed knowledge of the exciting forces. Up to now, only few investigations relating to unsteady aerodynamic forces in radial turbines were presented. To give a detailed insight into the complex phenomena, a comprehensive research project was initiated at the Institut für Thermische Strömungsmaschinen, at the University of Karlsruhe. A turbocharger test rig was installed in the high pressure, high temperature laboratory of the institute. The present paper gives a description of the test rig design and the measuring techniques. The flow field in a vaneless radial inflow turbine was analyzed using laser Doppler anemometry. First results of unsteady flow field investigations in the turbine scroll and unsteady phase resolved measurements of the flow field in the turbine rotor will be discussed. Moreover, results from finite element calculations analyzing frequencies and mode shapes are presented. As vibrations in turbines of turbochargers are assumed to be predominantly excited by unsteady aerodynamic forces, a method to predict the actual transient flow in a radial turbine utilizing the commercial Navier Stokes solver TASCflow3d was developed. Results of the unsteady calculations are presented and comparisons with the measured unsteady flow field are made. As a major result, the excitation effect of the tongue region in a vaneless radial inflow turbine can be demonstrated.

Unsteady Turbine Rim Sealing and Vane Trailing Edge Flow Effects

2021 ◽  
Author(s):  
Iván Monge-Concepción ◽  
Shawn Siroka ◽  
Reid A. Berdanier ◽  
Michael D. Barringer ◽  
Karen A. Thole ◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotational Speed ◽  
Large Scale ◽  
Trailing Edge ◽  
Time Resolved ◽  
Flow Rates ◽  
Large Scale Structures ◽  
Purge Flow ◽  
Scale Structures

Abstract Hot gas ingestion into the turbine rim seal cavity is an important concern for engine designers. To prevent ingestion, rim seals use high pressure purge flow but excessive use of the purge flow decreases engine thermal efficiency. A single stage test turbine operating at engine-relevant conditions with real engine hardware was used to study time-resolved pressures in the rim seal cavity across a range of sealing purge flow rates. Vane trailing edge (VTE) flow, shown previously to be ingested into the rim seal cavity, was also included to understand its effect on the unsteady flow field. Measurements from high-frequency response pressure sensors in the rim seal and vane platform were used to determine rotational speed and quantity of large-scale structures (cells). In a parallel effort, a computational model using Unsteady Reynolds-averaged Navier-Stokes (URANS) was applied to determine swirl ratio in the rim seal cavity and time-resolved rim sealing effectiveness. The experimental results confirm that at low purge flow rates, the VTE flow influences the unsteady flow field by decreasing pressure unsteadiness in the rim seal cavity. Results show an increase in purge flow increases the number of unsteady large-scale structures in the rim seal and decreases their rotational speed. However, VTE flow was shown to not significantly change the cell speed and count in the rim seal. Simulations point to the importance of the large-scale cell structures in influencing rim sealing unsteadiness, which is not captured in current rim sealing predictive models.

CFD Analysis of the Unsteady Flow in a Two-Stage Axial Turbine

2016 ◽  
Author(s):  
Yang Pan ◽  
Qi Yuan ◽  
Qian Chen ◽  
Qing Ge ◽  
Dawei Ji
Keyword(s):  
Unsteady Flow ◽  
Rotational Speed ◽  
High Speed ◽  
Stokes Equations ◽  
Great Influence ◽  
Two Stage ◽  
Lower Efficiency ◽  
Axial Turbine ◽  
Partial Admission ◽  
Mode A

Partial admission, which has the advantage of avoiding large losses while the turbine at low load operations, is widely used in regulating the power of turbomachinery. However, partial admission causes prominent unsteady flow, additional exciting forces and extra losses. Thus, it has great significance to investigate the characteristics of partial admission turbines. In this paper, efficiency and unsteady flow performance of a small two-stage subsonic axial turbine with partial admission are analyzed. Firstly, a 3-D model with four discontinuous equally-distributed nozzle blocks was built, and the computational grid, which only consisted of hexahedral mesh, was generated. Reynolds Averaged Navier-Stokes equations were solved by commercial software ANSYS-CFX and the RNG k-ε turbulence model was adopted. Secondly, to investigate the influence of admission modes, two partial admission modes (A-two diagonal valve opening; B-two adjacent valves opening) were analyzed separately and compared with the full admission situation (Mode C). Finally, the turbine performances in Mode A and B at other speeds (75% and 110% of rated speed) were analyzed and pressure distributions at three different heights (10%, 50% and 90% of the blade height) were investigated in detail. The results indicated that partial admission could cause extra mixture losses and lead to lower efficiency. Among these kinds of modes, full admission (Mode C) performed best in efficiency, and Mode B performed better than Mode A under partial admission conditions. Furthermore, strong non-uniformity was found in circumferential direction and large pressure drop occurred at the gap between two admission blocks due to expansion effects. The computational results also showed that the flow parameter fluctuations attenuated evidently in the downstream stages and the pressure vibration mainly occurred after nozzle stages. Strong vortices and backflow can be noticed at the pressure side of the active nozzle boxes. Additionally, the rotational speed has a great influence on the performance of turbine. Higher rotational speed led to bigger efficiency and smoother pressure distribution. And the alteration trend becomes slow at high speed.

Numerical Solutions for Unsteady Subsonic Vortical Flows Around Loaded Cascades

1993 ◽  
Vol 115 (4) ◽  
pp. 810-816 ◽  
Author(s):  
J. Fang ◽  
H. M. Atassi
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Frequency Range ◽  
Mean Flow ◽  
Vortical Flows ◽  
Unsteady Aerodynamic ◽  
Reduced Frequency ◽  
The Mean

A frequency domain linearized unsteady aerodynamic analysis is presented for three-dimensional unsteady vortical flows around a cascade of loaded airfoils. The analysis fully accounts for the distortion of the impinging vortical disturbances by the mean flow. The entire unsteady flow field is calculated in response to upstream three-dimensional harmonic disturbances. Numerical results are presented for two standard cascade configurations representing turbine and compressor bladings for a reduced frequency range from 0.1 to 5. Results show that the upstream gust conditions and blade sweep strongly affect the unsteady blade response.

The Effect of Partial Admission on Multistage Radial Inflow Industrial Steam Turbine

2009 ◽  
Author(s):  
Yijin Li ◽  
Qun Zheng ◽  
Lanxin Sun
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Steam Turbine ◽  
Three Dimensional ◽  
Flow Patterns ◽  
Navier Stokes ◽  
Radial Turbine ◽  
Partial Admission ◽  
Aerodynamic Performances ◽  
Turbine Impeller

Aerodynamic performances of a partial admission multistage radial inflow turbine are investigated with numerical simulation. A three-dimensional unsteady Reynolds-averaged Navier–Stokes solver closed by Baldwin-Lomax model is applied for the computations. The flow field features of the first stages with partial admission are analyzed and discussed. Detailed flow patterns of the partial admission radial turbine impeller are presented here in this paper.

Meanline Modeling of Radial Inflow Turbine With Twin-Entry Scroll

2012 ◽  
Author(s):  
Carl F. Fredriksson ◽  
Xuwen Qiu ◽  
Nick C. Baines ◽  
Markus Müller ◽  
Nils Brinkert ◽  
...  
Keyword(s):  
Model Prediction ◽  
Good Accuracy ◽  
Cfd Analysis ◽  
Test Results ◽  
Analysis And Design ◽  
Radial Turbine ◽  
Partial Admission ◽  
Radial Inflow Turbine ◽  
Inlet Conditions ◽  
Accuracy Of Prediction

Twin entry turbines are widely used in turbocharging as a means of using the exhaust pulse energy of multi-cylinder engines. For modern engines where high levels of EGR are required, an asymmetric twin-entry turbine has been shown to have considerable advantages. Such turbines require a more developed approach to analysis and design than usual. A meanline model for a radial inflow turbine with twin-entry scroll has been developed. Different total pressures and total temperatures may be specified at each entry. Each volute passage is solved separately from the inlet to the splitter location, where the static pressures of both passages are assumed to be the same. From the volute splitter to the rotor inlet, the two streams mix into one uniform flow following conservation laws of continuity, momentum and energy. Experiments have been conducted on a test stand with a radial turbine with an asymmetric twin-entry scroll, where the inlet conditions can be varied independently for each entry. The test results are compared with the model prediction. A good accuracy of prediction is achieved with a realistic set of modeling coefficients. In the future, insights gained from test data and CFD analysis will be used to develop further the volute mixing model and include explicit partial admission losses in the rotor.

scholarly journals Design Parameter Influence on Losses and Downstream Flow Field Uniformity in Supersonic ORC Radial-Inflow Turbine Stators

2021 ◽  
Vol 6 (3) ◽  
pp. 38
Author(s):  
Alessandro Cappiello ◽  
Raffaele Tuccillo
Keyword(s):  
Flow Field ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Design Guidelines ◽  
Design Parameters ◽  
Minimum Length ◽  
Field Uniformity ◽  
Radial Inflow Turbine ◽  
Downstream Flow ◽  
Organic Fluids

The design of organic Rankine cycle (ORC) turbines often requires dealing with transonic flows due to the cycle efficiency requirements and the matching of the temperature profiles with heat sources and sinks, as well as the nature of organic fluids, often featuring high molecular weight. Consequently, the use of convergent–divergent turbine stators has been widely established as a solution in the published literature for use in both axial- and radial-inflow machines. With respect to the latter layout in particular, the available design guidelines are still limited. The present work shows the results of an investigation into a series of ORC radial-inflow convergent–divergent nozzles that differ with respect to the vane count and the designed metal angle of the outlet. These stators were designed by fitting the divergent portion of a sharp-edged minimum-length nozzle, designed by means of the method of characteristics (MoC) adapted to dense gases, into a radial-inflow turbine stator. The geometries were analysed by means of steady-state RANS CFD calculations, and the results were used to assess the influence of the design parameters on the nozzle losses and downstream flow field uniformity, showing that conflicting trends exist between optimum stator efficiency and optimum downstream flow field uniformity.

Investigation of the Unsteady Rotor Aerodynamics in a Transonic Turbine Stage

2000 ◽  
Vol 123 (1) ◽  
pp. 81-89 ◽  
Author(s):  
R. De´nos ◽  
T. Arts ◽  
G. Paniagua ◽  
V. Michelassi ◽  
F. Martelli
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Unsteady Flow ◽  
Rotational Speed ◽  
Pressure Field ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Turbine Stage ◽  
Rotor Aerodynamics ◽  
Transonic Turbine

The paper focuses on the unsteady pressure field measured around the rotor midspan profile of the VKI Brite transonic turbine stage. The understanding of the complex unsteady flow field is supported by a quasi-three-dimensional unsteady Navier–Stokes computation using a k-ω turbulence model and a modified version of the Abu-Ghannam and Shaw correlation for the onset of transition. The agreement between computational and experimental results is satisfactory. They both reveal the dominance of the vane shock in the interaction. For this reason, it is difficult to identify the influence of vane-wake ingestion in the rotor passage from the experimental data. However, the computations allow us to draw some useful conclusions in this respect. The effect of the variation of the rotational speed, the stator–rotor spacing, and the stator trailing edge coolant flow ejection is investigated and the unsteady blade force pattern is analyzed.

Investigation of the Unsteady Rotor Aerodynamics in a Transonic Turbine Stage

2000 ◽  
Author(s):  
R. Dénos ◽  
T. Arts ◽  
G. Paniagua ◽  
V. Michelassi ◽  
F. Martelli
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Unsteady Flow ◽  
Turbulence Model ◽  
Rotational Speed ◽  
Pressure Field ◽  
Navier Stokes ◽  
Turbine Stage ◽  
Rotor Aerodynamics ◽  
Transonic Turbine

The paper focuses on the unsteady pressure field measured around the rotor mid-span profile of the VKI Brite transonic turbine stage. The understanding of the complex unsteady flow field is supported by a quasi-3D unsteady Navier-Stokes computation using a k-? turbulence model and a modified version of the Abu-Ghannam and Shaw correlation for the onset of transition. The agreement between computational and experimental results is satisfactory. They both reveal the dominance of the vane-shock in the interaction. For this reason, it is difficult to identify the influence of vane-wake ingestion in the rotor passage from the experimental data. However, the computations allow to draw some useful conclusions in this respect. The effect of the variation of the rotational speed, the stator-rotor spacing and the stator trailing edge coolant flow ejection is investigated and the unsteady blade force pattern is analyzed.

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