Influence of the Flatness Ratio of an Automotive Torque Converter on Hydrodynamic Performance

Ejiri, Eiji; Kubo, Masaaki

doi:10.1115/1.2823513

Cited by 18 publications

(9 citation statements)

References 13 publications

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“…A number of researchers have studied the flat torque converter employing both analytical and experimental methods. Ejiri et al [11] manufactured and tested four torque converters with different flatness ratios. The experimental results show that the overall performance deteriorates when the flatness ratio is reduced to less than about 0.2.…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis and Improvement of Flat Torque Converters Using DOE Method

Chen

Zhu

2018

Chin. J. Mech. Eng.

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Automotive torque converters have recently been designed with an increasingly narrower profile for the purpose of achieving a smaller axial size and reducing weight. Design of experiment (DOE) and computational fluid dynamics (CFD) techniques are applied to improve the performance of a flat torque converter. Four torque converters with different flatness ratios (0.204, 0.186, 0.172, and 0.158) are designed and simulated first to investigate the effects of flatness ratio on their overall performance, including efficiency, torque ratio, and impeller torque factor. The simulation results show that the overall performance tends to deteriorate as the flatness ratio decreases. Then a parametric study covering six geometric parameters, namely, inlet and outlet angles of impeller, turbine, and stator is carried out. The results demonstrate that the inlet and outlet angles play an important role in determining the performance characteristics of a torque converter. Furthermore, the relative importance of the six design parameters is investigated using DOE method for each response (stall torque ratio and peak efficiency). The turbine outlet angle is found to exert the greatest influence on both responses. After DOE analysis, an optimized design for the flat torque converter geometry is obtained. Compared to the conventional product, the width of the optimized flat torque converter torus is reduced by about 20% while the values of stall torque ratio and peak efficiency are only decreased by 0.4% and 1.7%, respectively. The proposed new optimization strategy based on DOE method together with desirability function approach can be used for performance enhancement in the design process of flat torque converters.

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Section: Introductionmentioning

confidence: 99%

Performance Analysis and Improvement of Flat Torque Converters Using DOE Method

Chen

Zhu

2018

Chin. J. Mech. Eng.

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“…As the design of the torque converter tends toward flatter aspect ratios, the fluid motion may further aggravate blade loading and cracking. Ejiri and Kubo (1999) found that measured efficiency and torque capacity deteriorate with flatter designs. Corresponding numerical analysis indicated that a more pronounced jet-wake flow occurs at the pump exit with the flatter converter design, while efficiency loss at the pump inlet is attributed to an increased shock loss.…”

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confidence: 96%

Measurements of Strain on 310 mm Torque Converter Turbine Blades

Sweger¹,

Anderson²,

Blough³

2004

The International Journal of Rotating Machinery

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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. Foiltype 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 passingfrequency 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.The automotive torque converter transfers rotational energy from an engine to a transmission through a viscous and incompressible working fluid. The three primary elements of a converter are the pump, turbine and stator. Each element is composed of a number of blades shaped such that they redirect the flow of oil passing though them, resulting in a change in angular momentum of the working fluid. While the converter is designed to perform optimally at a particular condition, it must function satisfactorily over a diverse range of conditions including idle, stall, near couple, and overspeed.Several previous studies have been conducted to better understand the nature of oil flow within the torque converter, with the primary concern being converter efficiency and performance. Dong et al. (1998) used a miniature high-frequency-response five-hole probe to find that the flow pattern at the pump exit is complex. The flow structure was described as having four main regions: the free-steam, the pump blade wake, the core-suction corner separation, and the intense mixing region. Additionally, a strong secondary flow was observed along with unsteadiness dominated by the pump blade passing frequency. Brun and Flack (1997a) used laser velocimetry to demonstrate a strong jet-wake region which propagates across the turbine inlet plane at the pump-turbine interaction frequency. Throughflow velocity unsteadiness and incidence angle unsteadiness, due to pumpturbine blade interaction, was found to be greater at a high speedratio (SR = 0.8) compared to near-stall (SR = 0.065). This is possible when the flow enters the turbine at approximately 45 • from the no...

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“…Others have performed studies of the flow fields in torque converters, including Browarzik (1994), Ejiri and Kubo (1998), Marathe and Lakshminarayana (1997), and Watanabe and colleagues (1997). Efforts at the University of Virginia have used nonintrusive laser velocimetry to map out the detailed flow fields discussed by, for example, Brun and Flack (1994) and Whitehead (1995).…”

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confidence: 97%

Flow Characteristics at the Pump-Turbine Interface of a Torque Converter at Extreme Speed Ratios

Habsieger¹,

Flack²

2003

The International Journal of Rotating Machinery

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The average velocity field at the pump-turbine interface in a scaled version of a truck torque converter was studied. Seven different turbine-to-pump rotational-speed ratios were examined, ranging from near stall (0.065) to overspeed (1.050) so as to determine the effect of the speed ratio on the flow field and on the mass flow rate. Laser velocimetry was used to measure the flow velocity through the pump's exit and the turbine's inlet plane. At the pump's exit, as the speed ratio increases, the high velocities move to the pressure-shell corner and then to both the core-suction and the pressureshell corners. Concentrated velocity gradients are largest at the lowest speed ratio, but areas of velocity gradients are largest near the coupling point. Near the coupling point, the flow field is most nonuniform, which yields a highly periodic flow into the turbine inlet. Above the coupling point, the high velocity remains in the pressure-shell corner but separation is seen to develop at the highest speed ratio. At the turbine's inlet, reverse flow is seen at low speed ratios and is an indicator of flow leakage through the core. Velocity gradients are very large at low speed ratios. As the speed ratio increases to the coupling point, the high velocities remain on the shell side. Above the coupling point, the high-velocity flow migrates from the shell side to the core side. The mass flow rate decreases significantly and nonlinearly with the increase of the speed ratio, but for speed ratios greater than 1.000, the negative slope decreases.Torque converters are commonly used in cars, buses, locomotives, and construction equipment as a mean of smooth torque transmission between the engine and the automatic transmission and to provide torque amplification during start-up conditions. The typical torque converter is a recirculating hydrodynamic, mixed-flow turbomachine (containing both radial and axial flow) with three independent blade cascade elements that govern the internal flow field. These three elements are the pump, which energizes the working fluid and which is connected to the engine; the turbine, which extracts the energy from the flow and translates it into output torque; and the stator which, ideally, redirects the turbine's exit flow back into the pump with a zero flow incidence at a specific design speed ratio. The pump and turbine are rotating at different angular speeds while the stator is either locked or allowed to float freely. Because of the significant curvature of the flow path and the high interaction among these three elements, the internal flow field is highly three-dimensional.The flow field, the torque, and the efficiency curves are normally determined only from the zero speed ratio (turbine has stopped) to the coupling point (turbine torque and pump torque are equal), which typically occurs at a speed ratio of 0.85 to 0.90. Performance characteristics are normally required only in the range from stall to cruise. A torque converter, however, can be operated at high positive speed ratios beyond the cru...

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Influence of the Flatness Ratio of an Automotive Torque Converter on Hydrodynamic Performance

Cited by 18 publications

References 13 publications

Performance Analysis and Improvement of Flat Torque Converters Using DOE Method

Performance Analysis and Improvement of Flat Torque Converters Using DOE Method

Measurements of Strain on 310 mm Torque Converter Turbine Blades

Flow Characteristics at the Pump-Turbine Interface of a Torque Converter at Extreme Speed Ratios

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