Exit traverse study of mixed-flow turbines with inlet incidence variation

1997 ◽  
Vol 211 (6) ◽  
pp. 461-475 ◽  
Author(s):  
H Chen ◽  
N C Baines ◽  
M Abidat
Keyword(s):  
Flow Separation ◽  
Incidence Angle ◽  
Internal Flow ◽  
Suction Side ◽  
Exhaust Pipe ◽  
Mixed Flow ◽  
Blade Loading ◽  
Rotor Design ◽  
The One ◽  
Inlet Angle

This paper reports a traverse survey of the flow conditions at the exhaust pipe of two mixed-flow turbines. The experimental method is described and the results discussed. It shows that for both turbines, a shroud-hub flow migration might be generated within the blades at higher pressure ratios, which relieves the high blade loading at the shroud, and a flow separation from the suction side of the hub might occur at the lower pressure ratios. The turbine with ‘constant incidence angle’ rotor design suffered from greater swirl loss and a possible internal flow separation than the one with a constant blade inlet angle.

The Effect of Leading Edge Curvature on a Mixed Flow Turbine Performance Under Pulsating Flow Conditions

2009 ◽  
Author(s):  
Li Chen ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Shuyong Zhang
Keyword(s):  
Incidence Angle ◽  
Leading Edge ◽  
Simulation Models ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Turbine Performance ◽  
Unsteady Simulation ◽  
Overall Performance ◽  
Inlet Angle

Turbines used in turbochargers matched to reciprocating engines are under natural pulsating flow conditions, and the turbine which has a good performance under steady design condition normally cannot get the same performance in the whole engine actual working circle. Under the pulsating conditions, the incidence angle will change tremendously, thus leads to undesirable flowfield in the turbine. It is shown in some published literature that varying turbine blade inlet angle can achieve better performance characteristics. In this paper, leading edge curvature is introduced to an original mixed flow turbine, while steady and unsteady simulation models of the mixed flow turbine are built to investigate the aerodynamic performance of the original and modified turbine. Flowfield analysis shows that the leading edge curvature can make the flow less sensitive to the incidence change, and average instantaneous efficiency under pulsating flow conditions is improved, while a better overall performance of the turbine is achieved.

scholarly journals Numerical Simulation on the Influence of Rotating Speed on the Hydraulic Loss Characteristics of Desalination Energy Recovery Turbine

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Bing Qi ◽  
Desheng Zhang ◽  
Qi Zhang ◽  
Mengcheng Wang ◽  
Ibra Fall
Keyword(s):  
Flow Separation ◽  
Energy Recovery ◽  
Internal Flow ◽  
Leading Edge ◽  
Suction Side ◽  
Radial Pressure ◽  
Hydraulic Loss ◽  
Rotating Speed ◽  
The Impact ◽  
Loss Mechanisms

The performance of energy recovery turbine (ERT) directly determines the cost and energy consumption of reverse osmosis desalination. In order to study the performance and loss mechanisms of ERT under different conditions, the external characteristics and the losses of different components were quantitatively analyzed. The loss mechanisms of each component in the turbine were revealed through the comparative analysis of the internal flow field. The results show that the efficiency is 2.2% higher than that at the design speed when turbine runs at n = 22000 r/min. The impeller losses account for more than 67% of the total losses. The impeller loss is mainly observed at the leading edge. The vortex on the pressure side of the leading edge is caused by the impact effect, while the vortex on the suction side of the leading edge is caused by the flow separation. With the increase in the rotating speed, the loss caused by flow separation in impeller decreases obviously. The volute loss is mainly observed near the tongue, which is caused by the flow separation at the tongue. The design of the tongue is very important to the performance of the volute. The turbulent kinetic energy (TKE) and loss decrease with the increase in the rotating speed. The loss in the draft tube is mainly observed at the inlet core. With the increase in the rotating speed, the turbulence pulsation and the radial pressure fluctuation amplitude reduce. Therefore, the turbine can be operated at the design or slightly higher than the design rotating speed under the condition that both the hydraulic condition and the intensity are satisfied, which are conducive to the efficient utilization of energy.

Effect of Tip Clearance on Rotating Stall in a Mixed-Flow Pump

2019 ◽  
Author(s):  
Wei Li ◽  
Ramesh K. Agarwal ◽  
Ling Zhou ◽  
Enda Li ◽  
Leilei Ji
Keyword(s):  
Flow Separation ◽  
Internal Flow ◽  
Energy Performance ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Pump Efficiency ◽  
Mixed Flow ◽  
Performance Curves ◽  
Flow Pump

Abstract The non-uniform disturbance in the circumferential direction is the main cause for the occurrence of rotating stall in turbomachinery. In order to study the effect of tip clearance leakage flow on rotating stall, the mixed-flow pump models with different tip clearances are numerically simulated, and then the energy performance curves and internal flow structures are obtained and compared. The results show that the computed pump efficiency and the internal flow field of the pump from numerical simulation are in good agreement with the experimental results. A saddle region appears in the energy performance curves of the three tip clearances, and with decrease in tip clearance, the head and efficiency of the mixed-flow pump increase and the critical stall point shifts, and the stable operating range of the mixed-flow pump decreases, which indicates that the mixed-flow pump stalls easily for smaller tip clearance. Under the deep stall condition, the influence of the leakage flow in the end wall area increases gradually with decrease in clearance. For small clearance, the leakage flow moves away from the suction surface to some distance to form a number of leakage vortex strips with the mainstream flow and flows over the leading edge of the next blade and then flows downstream into different flow passages, generating backflow and secondary flow separation at the blade inlet, which seriously damages the spatial structure of the inlet flow. This results in the earlier occurrence of stall. With increase in clearance, the leakage vortex develops along the radial direction towards the middle of the flow channel and large flow separation occurs in the downstream channel, which induces deep stall. For 0.8mm clearance, the whole impeller outlet passage is almost blocked by the backflow of the guide vane inlet, and a deep stall is induced.

Effect of Tip Clearance on Rotating Stall in A Mixed-Flow Pump

2021 ◽  
pp. 1-39
Author(s):  
Wei Li ◽  
Leilei Ji ◽  
Enda Li ◽  
Ling Zhou ◽  
Ramesh Agarwal
Keyword(s):  
Flow Separation ◽  
Internal Flow ◽  
Energy Performance ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Pump Efficiency ◽  
Mixed Flow ◽  
Performance Curves ◽  
Flow Pump

Abstract The non-uniform disturbance in circumferential direction is main cause for occurrence of rotating stall in turbomachinery. In order to study the effect of tip clearance leakage flow on rotating stall, mixed-flow pump models with different tip clearances are simulated and energy performance curves and internal flow structures are obtained and compared. The results show that the computed pump efficiency and the internal flow field of the pump are in good agreement with experimental results. A saddle region appears in energy performance curves of three tip clearances and with decrease in tip clearance, the head and efficiency of mixed-flow pump increase and critical stall point shifts and stable operating range of mixed-flow pump decreases, which indicates that mixed-flow pump stalls easily for smaller tip clearance. Under deep stall condition, influence of leakage flow in end wall area increases gradually with decrease in clearance. For small clearance, the leakage flow moves away from suction surface to some distance to form number of leakage vortex strips with mainstream flow and flows over the leading edge of next blade and then flows downstream into different flow passages generating back flow and secondary flow separation at the blade inlet, which seriously damages the spatial structure of inlet flow. This results in earlier occurrence of stall. With increase in clearance, the leakage vortex develops along radial direction towards middle of flow channel and large flow separation occurs in downstream channel which induces deep stall.

Investigation of a Novel Turbine Housing to Produce a Non-Uniform Spanwise Flow Field at the Inlet to a Mixed Flow Turbine and Provide Variable Geometry Capabilities

2021 ◽  
Author(s):  
Richard Morrison ◽  
Charles Stuart ◽  
Sung In Kim ◽  
Stephen Spence ◽  
Andre Starke ◽  
...  
Keyword(s):  
Flow Separation ◽  
Incidence Angle ◽  
Operating Conditions ◽  
Variable Geometry ◽  
The Novel ◽  
Mixed Flow ◽  
Engine Operation ◽  
Turbine Performance ◽  
The Impact ◽  
Spanwise Flow

Abstract Automotive engine downsizing has placed an increased focus on the ability of the turbocharger to provide adequate boost levels across the full engine operating rage. To achieve the desired levels of turbocharger performance the turbine must be capable of operating effectively at the intended design point and also at off-design conditions. Mixed flow turbines (MFTs) provide a potential method to improve performance at off-design conditions and during transient engine operation. A unique feature of a MFT is the spanwise variation of incidence angle at the rotor leading edge. This results in additional flow separation from the blade suction surface near the hub under a wide range of operating conditions. The flow separation generates additional loss and has a detrimental impact on turbine performance. A novel design of turbine volute similar to a conventional twin-entry turbine volute was examined. The novel turbine volutes were designed to produce a spanwise variation in flow conditions at the rotor inlet. The primary objective was to reduce the incidence angle and increase the mass flow rate at the hub side of the passage relative to the shroud side, as it has previously been identified that this can be beneficial for MFT performance. A number of different volute geometries were examined by numerical analysis to determine the impact of key parameters on turbine performance. The results indicated that generating a suitable spanwise flow distribution could produce a moderate improvement in turbine efficiency at off-design operating conditions. The novel volute design also provided a means of achieving a degree of variable geometry operation to further improve off-design performance. Turbine performance was examined under the variable geometry operation and an improvement in turbine power output at low speed, off-design conditions was achieved. This was analogous to operating with a conventional pivoting vane variable geometry system and had the potential to benefit performance during transient engine operation.

Investigation of Flow Separation Characteristics in a Pump as Turbines Impeller Under the Best Efficiency Point Condition

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Tong Lin ◽  
Xiaojun Li ◽  
Zuchao Zhu ◽  
Renhua Xie ◽  
Yanpi Lin
Keyword(s):  
Flow Separation ◽  
Topological Structure ◽  
Static Pressure ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Surface Friction ◽  
Suction Side ◽  
Peak Position ◽  
Transient Pressure ◽  
Point Condition

Abstract The impeller, which is the main energy conversion component of a pump as turbine (PAT), is designed for pumping mode, and its internal flow characteristics are quite complicated even at the best efficiency point (BEP) of the turbine mode. This study aims to investigate the flow separation characteristics in a PAT impeller under the BEP condition by numerical method. The hydraulic performance and transient pressure characteristics of PAT predicted numerically were verified through experimentation. The surface friction lines and flow topological structure were applied to diagnose the flow separation at the surface of the blade. The relationship between flow topological structure and vortex in the impeller and static pressure at the blade were analyzed. Analysis results show that the backflow and open flow separation are observed significantly in the leading region and near the shroud of the trailing region of suction side. The passage vortex always appears near the spiral node. The saddle point and spiral node correspond to the peak position of adverse pressure and the lowest position between two peak values of the static pressure of the blade, respectively. The inflow conditions of blade and shape of the trailing edge significantly influence the flow separations in the impeller.

Numerical Investigation of Effects of Incidence Angle on Aerodynamic Performance of Ultra-Highly Loaded Turbine Cascade

2006 ◽  
Author(s):  
Hoshio Tsujita ◽  
Shimpei Mizuki ◽  
Atsumasa Yamamoto
Keyword(s):  
Numerical Investigation ◽  
Gas Turbines ◽  
Incidence Angle ◽  
Internal Flow ◽  
Secondary Flows ◽  
Turbine Cascade ◽  
Degree Relative ◽  
Flow Angle ◽  
Blade Loading ◽  
Highly Loaded

An increase in turbine blade loading is a useful means to improve the performance characteristics of gas turbines. This paper describes the results of numerical investigation for the internal flow within a low speed linear ultra highly loaded turbine cascade (UHLTC) at the off design condition. The present UHLTC has the design inlet flow, angle of 80 degree and the blade turning angle of 160 degree. The computations were made for the incidence angles from −30.0 to +7.5 degree relative to the design incidence. The two dimensional computations were carried out for eight incidence angles in order to reveal the effects of incidence on the profile loss of UHLTC. Subsequently, the three dimensional computations were performed for the several incidence angles to clarify the sensitivity of secondary flow and the associated loss generation mechanisms to the change of incidence angle. The influences of incidence variation on the blade loading were also examined. The computed results showed that the loss generation and the strength and the structure of secondary flows were much sensitive to the increase of incidence angle from the design incidence. On the other hand, the decrease of the incidence from the design one did not give the strong effect for the loss generation and the blade loading.

Comparison of Steady and Unsteady Flows in a Transonic Radial Vaned Diffuser

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
E. Benichou ◽  
I. Trébinjac
Keyword(s):  
Centrifugal Compressor ◽  
Flow Separation ◽  
Suction Side ◽  
Vaned Diffuser ◽  
Diffuser Flow ◽  
Transonic Centrifugal Compressor ◽  
Compressor Surge ◽  
Overall Performance ◽  
The One ◽  
Suction Slot

Boundary layer suction can be effective in delaying compressor surge, if the surge is triggered by flow separation on the shroud- or hub-casing. This work aims at positioning a suction slot in a radial vaned diffuser, which is thought to be the limiting component in a centrifugal compressor, such as the one considered here. The location of the slot is determined based on the results of both steady and unsteady flow simulations of a transonic centrifugal compressor of a turboshaft. Although the overall performance of the compressor is well-described by steady RANS, large discrepancies are observed between the steady and unsteady simulations of the diffuser flow, discrepancies imply different flow-separation scenarios. Steady results show more low-momentum fluid near the hub, whereas it is concentrated near the shroud in the unsteady simulations, hence no valid physical conclusions can be expected from the steady simulations. Analysis of the instantaneous skin-friction distribution from the unsteady simulations reveals that the separation is fixed and leads to a slot location on the shroud casing, near the diffuser main-vane suction side, so that it covers the range of separation saddle positions as the operating point is changed.

scholarly journals The Effects of Blade Loading in Radial and Mixed Flow Turbines

1992 ◽  
Author(s):  
H. Chen ◽  
M. Abidat ◽  
N. C. Baines ◽  
M. R. Firth
Keyword(s):  
Good Accuracy ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Test Results ◽  
Turbine Cascade ◽  
Paper Test ◽  
Mixed Flow ◽  
Blade Loading ◽  
Blade Number ◽  
Radial Turbines

Understanding of the effects of blade loading and blade number in radial and mixed flow turbines is often based on analogies with axial turbine cascade tests or centrifugal compressors rather than direct measurement. In this paper test results from a series of similar mixed flow turbines are described. The turbine rotors differ only in blade number or inlet incidence variation. The results comprise performance data and hub and shroud pressure measurements, from which it is possible to deduce parameters such as incidence angle with good accuracy. In addition, predictions of blade loading using three-dimensional computations are shown. The results are correlated against a loading coefficient and a slip factor, both derived for the general case of a mixed flow turbine. The influence of these parameters on the performance of the tested turbines, and for comparison of other radial turbines, is shown.

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