Flow Pattern Evolution and Energy Decomposition of Flows at Different Operating Conditions in a Hydrodynamic Torque Converter

2016 ◽  
Author(s):  
Wei Wei ◽  
Mingxing Huang ◽  
Yu Li ◽  
Qingdong Yan
Keyword(s):  
Vortex Structure ◽  
Velocity Vector ◽  
Power Transmission ◽  
Flow Behavior ◽  
Internal Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Energy Decomposition ◽  
Complex Flow

Power loss and flow blockage in turbomachinery such as hydrodynamic torque converter are usually caused by jet flow, second flow and flow separation. In this paper, the velocity vector and the pressure distribution of the internal flow field in hydrodynamic torque converter were reduced by the method of the Proper Orthogonal Decomposition (POD) to find the main flow structures and the energy decomposition in the passages of pump, turbine and stator. In order to find their evolutionary processes and energy decompositions, oil flow visualizations were conducted at different speed ratios from 0 to 0.8, including stall condition and design operating condition. The results showed that the first few modes containing the majority of energy could provide enough accuracy to predict flow behavior and flow structure in flow passages. Especially when the energy percentage of the first mode was majority, its vortex structures could be recognized easily. But the flow patterns of other modes were different from each other and they made the flow more turbulent and complex, which increases the energy loss in the process of power transmission. Besides that, the change of pressure gradient had a direct influence to velocity vector. The results also indicated that the observed fluid pattern of vortex structure became extensive while the influence of secondary flow decreased in the flow passage of pump with the increase of speed ratio. But the situation is just reversed in turbine, that is, the vortex disappeared gradually and the irregular turbulent flow appeared as the increase of speed ratio. In stator, the vortex structure emerged gradually when the speed ratio increased. So the method of snapshots is a very useful way to analyze the complex flow flied in depth and to predict the trend of development.

scholarly journals Laser Velocimeter Measurements in the Turbine of an Automotive Torque Converter: Part I — Average Measurements

1995 ◽  
Author(s):  
Klaus Bran ◽  
Ronald D. Flack
Keyword(s):  
Velocity Vector ◽  
Average Velocity ◽  
Incidence Angle ◽  
Torque Converter ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Flow Angle ◽  
Pump Speed ◽  
Turbine Pump ◽  
Mass Flows

The three-dimensional average velocity field in an automotive torque converter turbine was examined. Two significantly different operating conditions of the torque converter were tested: the 0.065 and 0.800 turbine/pump speed ratio. Velocities were measured using a one-directional, frequency shifted laser velocimeter. The instantaneous angular positions of the torque converter turbine and pump were recorded using digital shaft encoders. Shaft encoder information and velocities were correlated to generate average velocity blade-to-blade profiles and velocity vector plots. Measurements were taken in the inlet, quarter, mid, and exit planes of the turbine. From the experimental velocity measurements, mass flows, turbine output torque, average vorticities, viscous dissipation, inlet incidence flow angles, and exit flow angles were calculated. Average mass flows were 23.4 kg/s and 14.7 kg/s for the 0.065 and 0.800 speed ratios, respectively. Velocity vector plots for both turbine/pump speed ratios showed the flow field in the turbine quarter and mid planes to be highly non-uniform with separation regions and reversed flows at the core-suction corner. For the conditions tested, the turbine inlet flow was seen to have a high relative incidence angle, while the relative turbine exit flow angle was close to the blade angle.

Laser Velocimeter Measurements in the Turbine of an Automotive Torque Converter: Part I—Average Measurements

1997 ◽  
Vol 119 (3) ◽  
pp. 646-654 ◽  
Author(s):  
K. Brun ◽  
R. D. Flack
Keyword(s):  
Velocity Vector ◽  
Average Velocity ◽  
Incidence Angle ◽  
Torque Converter ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Flow Angle ◽  
Pump Speed ◽  
Turbine Pump ◽  
Mass Flows

The three-dimensional average velocity field in an automotive torque converter turbine was examined. Two significantly different operating conditions of the torque converter were tested: the 0.065 and 0.800 turbine/pump speed ratio. Velocities were measured using a one-directional, frequency-shifted laser velocimeter. The instantaneous angular positions of the torque converter turbine and pump were recorded using digital shaft encoders. Shaft encoder information and velocities were correlated to generate average velocity blade-to-blade profiles and velocity vector plots. Measurements were taken in the inlet, quarter, mid, and exit planes of the turbine. From the experimental velocity measurements, mass flows, turbine output torque, average vorticities, viscous dissipation, inlet incidence flow angles, and exit flow angles were calculated. Average mass flows were 23.4 kg/s and 14.7 kg/s for the 0.065 and 0.800 speed ratios, respectively. Velocity vector plots for both turbine/pump speed ratios showed the flow field in the turbine quarter and midplanes to be highly nonuniform with separation regions and reversed flows at the core-suction corner. For the conditions tested, the turbine inlet flow was seen to have a high relative incidence angle, while the relative turbine exit flow angle was close to the blade angle.

Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach

2005 ◽  
Vol 127 (1) ◽  
pp. 136-144 ◽  
Author(s):  
Yahya Dogu
Keyword(s):  
Porous Medium ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Force Balance ◽  
Complex Flow ◽  
Blow Down ◽  
Permeability Coefficients ◽  
Backing Plate ◽  
Brush Seal

The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis, and bristle flutter. In this study, an axisymmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data: leakage, axial pressure on the rotor surface, and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for the fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while the fence height region is free to spread and bend in the axial direction. It is found that flow resistance for the upper region should be 20% higher than the fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.

Analysis of the internal flow behavior on S-shaped region of a Francis pump turbine on turbine mode

2016 ◽  
Vol 33 (2) ◽  
Author(s):  
Yexiang Xiao ◽  
Wei Zhu ◽  
Zhengwei Wang ◽  
jin zhang ◽  
Chongji Zeng ◽  
...  
Keyword(s):  
Design Methodology ◽  
Flow Characteristic ◽  
Stokes Equations ◽  
Flow Behavior ◽  
Internal Flow ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Unit Discharge ◽  
Pump Turbine ◽  
Runner Blade

Purpose Numerically analyzed the flow characteristic and explored the hydrodynamic mechanism of the S-shaped region formation of a Francis pump-turbine. Design/methodology/approach Three-dimensional steady and unsteady simulations were performed for a number of operating conditions at the optimal guide vanes opening. The steady Reynolds averaged Navier-Stokes equations with the SST turbulence model were solved to model the internal flow within the entire flow passage. The predicted discharge-speed curve agrees well with the model test at generating mode. This paper compared the hydrodynamic characteristics of for off-design cases in S-shaped region with the optimal operating case, and more analysis focuses particularly on very low positive and negative discharge cases with the same unit speed. Findings At runaway case towards smaller discharge, the relative circumferential velocity becomes stronger in the vaneless, which generates the “water ring” and blocks the flow between guide vane and runner. The runner inlet attack angle becomes larger, and the runner blade passages nearly filled with flow separation and vortexes. The deterioration of runner blade flow leads to the dramatic decrease of runner torque, which tends to reduce the runner rotation speed. In this situation, the internal flow can’t maintain the larger rotating speed at very low positive discharge cases, so the unit discharge-speed curves bend to S-shaped near runaway case. Originality/value The analysis method of four off-design cases on S-shaped region with the comparison of optimal operation case and the calculated attack angles are adopted to explore the mechanism of S characteristic. The flow characteristic and quantitative analysis all explain the bending of the unit discharge-speed curves.

scholarly journals Effect of internal leakage on torque converter characteristics

2020 ◽  
Vol 12 (9) ◽  
pp. 168781402095996
Author(s):  
Xiong Pan ◽  
Chen Xinyuan ◽  
Sun Hongjun ◽  
Zhong Jiping ◽  
Zhen Chenping
Keyword(s):  
Energy Loss ◽  
Pressure Pulsation ◽  
Internal Flow ◽  
Torque Converter ◽  
Main Flow ◽  
Speed Ratio ◽  
Leakage Flow ◽  
Flow State ◽  
Simulation Accuracy ◽  
Leakage Area

To understand the effect of internal leakage on the torque field and characteristics of a torque converter (TC), a transient analysis was performed on the internal flow of a TC and the pressure pulsation characteristics of monitoring points in the convection channel. It was found that dividing the leakage area of the TC into a separate watershed improved simulation accuracy by 4%. When there was a leakage area, there were distinct collision, mixing, and assimilation stages between the leakage flow and the main flow. These phenomena caused energy loss that was highest at low speed ratios. However, the leakage flow always accounted for 12% of the main flow regardless of the speed ratio. At the same time, the leakage flow had a larger influence on pressure pulsation inside the TC and especially the low frequency band was more substantial. This shows that the leakage area has a large influence on the TC performance, energy loss, and flow state. Analysis of the leakage area showed that reducing the leakage area helps to improve powertrain performance and fuel economy.

scholarly journals Measurements of Strain on 310 mm Torque Converter Turbine Blades

2004 ◽  
Vol 10 (1) ◽  
pp. 55-63
Author(s):  
P. O. Sweger ◽  
C. L. Anderson ◽  
J. R. Blough
Keyword(s):  
Turbine Blade ◽  
Turbine Blades ◽  
Torque Converter ◽  
Operating Conditions ◽  
Surface Strain ◽  
Speed Ratio ◽  
Constant Input ◽  
Wide Range ◽  
Blade Tip ◽  
Input Torque

An automotive torque converter was tested in order to determine the effect of converter operating condition and turbine blade design on turbine blade strain in the region of the inlet core tab restraint. The converter was operated over a wide range of speed ratios (0 to 0.95) at constant input torque and a stall condition for two input torques. Foil-type strain gages in combination with wireless microwave telemetry were used to measure surface strain on the turbine blade. Strain measurements were made on two turbine blade designs.The steady component of strain over the range of speed ratios suggests the effect of both torque loading and centrifugal loading on the turbine blade tip. The unsteady strain was greatest at stall condition and diminished as speed ratio increased. Greater input torque at stall condition resulted in both greater steady strain and greater unsteady strain. The spectral distribution of strain over the range of tested speed ratios displayed an increase in low-frequency broadband fluctuations near stall condition. A blade-periodic event is observed which correlates to the pump-blade passing frequency relative to the turbine rotating frame. Reducing the blade-tip surface area and increasing the inlet-tab root radius reduced the range of steady strain and magnitude of unsteady strain imposed near the inlet core tab restraint over the range of operating conditions.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1996 ◽  
Vol 118 (4) ◽  
pp. 835-843 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stator at several operating conditions. The flow field is found to be highly three dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier–Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

Laser Velocimeter Measurements in the Turbine of an Automotive Torque Converter: Part II — Unsteady Measurements

1995 ◽  
Author(s):  
Klaus Bran ◽  
Ronald D. Flack
Keyword(s):  
Velocity Field ◽  
Angular Position ◽  
Torque Converter ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Velocity Data ◽  
Velocity Fluctuations ◽  
Blade Passage ◽  
Turbine Pump ◽  
Output Torque

The unsteady velocity field found in the turbine of an automotive torque converter was measured using laser velocimetry. Velocities in the inlet, quarter, mid, and exit planes of the turbine were investigated at two significantly different operating conditions: turbine/pump rotational speed ratios of 0.065, and 0.800. A data organization method was developed to visualize the three-dimensional, periodic unsteady velocity field in the rotating frame. For this method, the acquired data is assumed to be periodic at synchronous and blade interaction frequencies. Two shaft encoders were employed to obtain the instantaneous angular position of the torque converter pump and turbine at the instant of laser velocimeter data acquisition. By proper “registration” of the velocity data, visualizing the transient interaction effects between the turbine, pump, and stator was possible. Results showed strong cyclic velocity fluctuations in the turbine inlet plane as a function of the relative turbine-pump position. These fluctuations are due to the passing of upstream pump blades by the slower rotating turbine blades. Typical fluctuations in the through flow velocity were 3.6 m/s. Quarter and mid plane velocity fluctuations were seen to be lower; typical values were 1.5 m/s and 0.8 m/s, respectively. The flow field in the turbine exit plane was seen to be relatively steady with negligible fluctuations of less than 0.03 m/s. From the velocity data, the fluctuations of turbine performance parameters such as flow inlet angles, root-mean-square unsteadiness, and output torque per blade passage were calculated. Incidence angles were seen to vary by 3° and 6° for the 0.800 and 0.065 speed ratios, respectively, while the exit angles remained steady. The turbine output torque per blade passage fluctuated by 0.05 Nm for the 0.800 speed ratio and 0.13 Nm for the 0.065 speed ratio.

Influence of Stator Blade Geometry on Torque Converter Cavitation

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Cheng Liu ◽  
Wei Wei ◽  
Qingdong Yan ◽  
Brian K. Weaver ◽  
Houston G. Wood
Keyword(s):  
High Speed ◽  
Torque Converter ◽  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Speed Ratio ◽  
Capacity Loss ◽  
Wide Range ◽  
Stator Blade ◽  
Torque Converters ◽  
Blade Geometry

Cavitation in torque converters may cause degradation in hydrodynamic performance, severe noise, or even blade damage. Researches have highlighted that the stator is most susceptible to the occurrence of cavitation due to the combination of high flow velocities and high incidence angles. The objective of this study is to therefore investigate the effects of cavitation on hydrodynamic performance as well as the influence of stator blade geometry on cavitation. A steady-state homogeneous computational fluid dynamics (CFD) model was developed and validated against test data. It was found that cavitation brought severe capacity constant degradation under low-speed ratio (SR) operating conditions and vanished in high-speed ratio operating conditions. A design of experiments (DOE) study was performed to investigate the influence of stator design variables on cavitation over various operating conditions, and it was found that stator blade geometry had a significant effect on cavitation behavior. The results show that stator blade count and leaning angle are important variables in terms of capacity constant loss, torque ratio (TR) variance, and duration of cavitation. Large leaning angles are recommended due to their ability to increase the cavitation number in torque converters over a wide range of SRs, leading to less stall capacity loss as well as a shorter duration of cavitation. A reduced stator blade count is also suggested due to a reduced TR loss and capacity loss at stall.

Understanding the Flow Behavior in a Low Hub-Tip Ratio, High Aspect Ratio Contra-Rotating Axial Fan Stage

2012 ◽  
Author(s):  
Chetan S. Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
Total Pressure ◽  
Numerical Study ◽  
Flow Behavior ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Axial Fan ◽  
Stall Margin

This paper discusses the results of a parametric study of a pair of contra-rotating axial fan rotors. The rotors were designed to deliver a mass flow of 6 kg/s at 2400 rpm. The blades were designed with a low hub-tip ratio of 0.35 and an aspect ratio of 3.0. Numerical and experimental studies were carried out on these contra-rotating rotors operating at a Reynolds number of 1.25 × 105 (based on blade chord). The axial spacing between the rotors was varied between 50 to 120 % of the chord of rotor 1. The performance of the rotors was evaluated at each of these spacing at design and off-design speeds. The results from the numerical study (using ANSYS CFX) were validated using experimental data. In spite of certain limitations of CFD under certain operating conditions, it was observed that the results agreed well with those from the experiments. The performance of the fan was evaluated based on the variations of total pressure, velocity components and flow angles at design and off-design operating conditions. The measurement of total pressure, flow angles etc. are taken upstream of the first rotor, between the two rotors and downstream of the second rotor. It was observed that the aerodynamics of the flow through a contra rotating stage is significantly influenced by the axial spacing between the rotors and the speed ratio of the rotors. With increasing speed ratios, the strong suction generated by the second rotor, improves the stage pressure rise and the stall margin. Lower axial spacing on the other hand, changes the flow incidence to the second rotor and thereby improves the overall performance of the stage. The performance is investigated at different speed ratios of the rotors at varying axial spacing.

Sign in / Sign up

Export Citation Format

Share Document