Hydrodynamic Torque Converter Research Articles

Research on the thermal flow characteristics of viscosity oil in hydrodynamic torque converter

The increase in power density of hydrodynamic torque converters (HTCs) leads to a sharp rise in temperature within flow channels, affecting the reliability. In order to accurately predict the thermal effect and temperature distribution characteristics of the HTC internal viscosity oil, a multi-physics computational fluid dynamics (CFD) model is proposed. A specialized test bench was established, and the macro and internal flow temperature data were obtained. HTCs with different working conditions and wheel sets were studied. The results indicate that CFD model considering energy equation can accurately predict the overall hydrodynamic performance and the flow field temperature characteristics under different rotating conditions. The prediction error of the overall temperature rise is within 4.92%, and the flow field temperature prediction error of the stator is under 14.3%. The hydraulic characteristics is improved by 6.02%. The analysis of internal flow and energy exchange characteristics indicates the thermal effects and temperature distribution mechanisms caused by energy loss in the flow field within the HTC. The study provides an effective computational model for the prediction and control of the heat generation of the HTC and enhances the depth of research on the flow mechanism of inhomogeneous flow fields caused by thermal effects.

Research on the New Hydrostatic Transmission System of Wheel Loaders Based on Fuzzy Sliding Mode Control

To improve the control performance and energy efficiency of the hydrostatic transmission (HST) system of wheel loaders, this study proposes a novel variable structure dual-motor hydrostatic transmission system, accompanied by a multivariable control strategy based on fuzzy sliding mode control. By constructing a simulation model of the transmission system, the performance of the novel transmission system is verified, and the control effects of common control strategies are compared. The simulation results show that the proposed control strategy and system have good matching and can adapt to disturbances actively. Field experiment results show that the proposed solution can achieve smooth automatic shifting of wheel loaders, while effectively adjusting system pressure, flow, and power. Compared with the traditional hydrodynamic torque converter loader transmission system, its transmission efficiency is effectively increased by 30%, and the efficiency is increased by 8% compared with the traditional hydrostatic transmission system This achievement is of great significance for improving the working efficiency of wheel loaders and reducing energy consumption. The future research focus is to further improve the multivariable control strategy, achieve intelligent operation, and improve the efficiency and reliability of the transmission system.

Development of a rational model range of hydrodynamic torque transformers based on their key parameters: method

Introduction (problem statement and relevance). The existing methods for development of a model range of hydrodynamic or hydraulic torque converters do not consider characteristics of devices operating together with such converters. Consideration of characteristics of internal combustion engines and gearboxes will allow development of a more rational model range of hydrodynamic torque converters.The purpose of the study is to develop a method for building a model range of hydrodynamic torque converters taking into account characteristics of devices operating together with such converters.Methodology and research methods. Based on the analysis of parameters characterizing a hydrodynamic torque converter and of the existing model ranges, key parameters have been selected. To select estimated figures and parameters, mathematical statistics elements have been used.Scientific novelty and results. The method has been developed that allows keeping and using advantages of the known methods and eliminating a number of their disadvantages. The advantage of the proposed method consists in consideration of characteristics of internal combustion engines and gearboxes assumed to be used, which will allow, using the optimization process, definition of rational key parameters of hydrodynamic torque converter models. Based on the proposed method, a computer application program has been developed for estimation of rationality of key parameters of hydrodynamic torque converters of a model range.Practical significance. It makes sense to use the proposed method when developing model ranges of hydrodynamic torque converters.

Optimal Synthesis of Hydrodynamic Torque Converters for Special-Purpose Vehicles

Optimal Synthesis of Hydrodynamic Torque Converters for Special-Purpose Vehicles

A Torque Conversion Solution to the Powertrain of Mobile Machine and Its Control Strategy

The demand for reducing fuel consumption and emission of mobile machines is increasing since they consume large amount of energy and generate huge exhaust each year. The wheel loader is a representative mobile machine and large wheel loader typically employs a hydrodynamic torque converter and an automatic transmission in the powertrain. The torque converter provides large torque amplification at low vehicle speed, however generates large amount of heat inside. This brings a challenge during frequent vehicle start and stop. In this study, an alternative torque conversion solution to the powertrain of mobile machine with a power split hydraulic transmission is proposed, where the hydraulic transmission is a substitute for the torque converter. It eliminates overheating problem by dissipating the heat inside through its outlet. The mathematical models of the proposed powertrain including the wheel drive and working function are developed. An engine-speed-based system optimization is conducted and a rule-based control strategy based on optimization results is developed. The engine operations and engine fuel consumptions with optimization-based and rule-based control strategies are compared using three different loading cycles (57 s, 30 s, 90 s). The results show the effectiveness of proposed powertrain solution and its control strategy.

Multi-Objective Optimization Design for a Novel Parametrized Torque Converter Based on an Integrated CFD Cascade Design System

Advanced cascade design theories and methods are crucial to the rapid development of torque converters. Therefore, the study proposed a new parametric design method for a hydrodynamic torque converter cascade. The method is embodied by using a cubic non-uniform rational B-splines (NURBS) open curve and closed curve, respectively, to carry out the parametric design of the unit blade camberline and unit blade thickness distribution, and the curvature of the designed blade curve is continuous. Then, the author developed batch and script files in the Isight platform for a fully automated integrated design of the hydrodynamic torque converter, including cascade parametric modeling, meshing, computational fluid dynamics (CFD) simulation, post-processing, and optimization design. A three-dimensional cascade integrated optimization design system of the hydrodynamic torque converter is established with CFD technology as the bottom layer design, a control file as the middle layer, and an optimization algorithm as the top layer drive. Finally, multi-objective optimization was carried out for the key cascade parameters (camberline peak height). Compared with the original blade, the optimized NURBS blade increased by 7.207% in high-efficiency region width (Gη), and the optimized blade increased by 2.673% in peak efficiency (ηmax) to meet the actual engineering requirements. The new parametric design method of the blade shape and the integrated optimization design system of a three-dimensional cascade of torque converter proposed in this paper significantly reduces the design costs and shortens the design cycle of the torque converter, which will provide a valuable reference for engineers of turbomachinery.

Design Approach and Mechanism Analysis for Cavitation-Tolerant Torque Converter Blades

As the development of hydrodynamic torque converters (HTCs) points toward increasing the pump input power and pump rotation speed, the negative effects of cavitation are worsening. Most studies focus on suppressing fluid machinery cavitation to attenuate the negative effects of cavitation, such as noise, vibration, and blade damage. Therefore, we proposed two stator cavitation suppression slotting methods to suppress stator cavitation in HTCs: (1) slotting both sides of the pressure and suction sides and (2) slotting one side of the suction side. The key design parameters are analyzed, including the slot width and slot position of the stator blade. Findings show that a wider slot enlarges the mass flow rate ventilation through the slot, thus reducing the cavitation risk but decreasing the hydrodynamic performance. The most effective slot position for the second proposed method (slotting one side of the suction side) is between S0.15 (stator suction side dimensionless distance 0.15 location) and S0.6 (stator blade suction side); here, the stator cavitation can be suppressed completely. The capacity factor (Tbg) and torque ratio (K) are decreased by 6.81% and 3.23%, respectively, under the stalling speed ratio, whereas the stator cavitation almost completely disappears. Therefore, the new method of slotting one side of the stator suction side completely suppresses the stator cavitation and significantly shortens the cavitation duration. The new method of slotting one side of the blade suction side can serve as a reference for turbomachinery design.

Modeling, calculation, and analysis of torsional vibration characteristics of the hydrodynamic transmission system in engineering vehicle

According to the typical working conditions of a loader and considering the complexity of the working conditions, the hydrodynamic transmission powertrain system was modeled in this study. Because the hydrodynamic torque converter is a flexible fluid transmission component in the transmission system, this study proposes and establishes equivalent variable damping and equivalent variable stiffness models of the hydrodynamic torque converter. Based on this, a torsional vibration simulation model of the loader with variable damping and stiffness is proposed, and the frequencies and amplitudes of the torsional resonance modes of the transmission system varying with engine speed and hydrodynamic torque converter speed ratio are obtained. It is determined that the variable stiffness of the hydrodynamic torque converter has little effect on the natural frequency of the vehicle, and taking variable damping and stiffness as input, the natural frequency and resonance points of the transmission system can be calculated more accurately. The simulation modeling and calculation approach are experimentally verified, and the simulation results are valid and closer to the real resonance.

3D Cavitation Shedding Dynamics: Cavitation Flow-Fluid Vortex Formation Interaction in a Hydrodynamic Torque Converter

Recent experiments have shown interactions between the cavitation and fluid vortex formation in a hydrodynamic torque converter. This study aimed to clarify the unsteady cavitation trigger mechanism and flow-induced vibration caused by turbulence–cavitation interactions. The mass transfer cavitation model and modified Reynolds-averaged Navier–Stokes k–ω model were used with a local density correction for turbulent eddy viscosity to investigate the cavitation structure in a hydrodynamic torque converter under various operating conditions. The model results were then validated against test data. The multi-block structured gridding technique was used to develop an orthogonally structured grid of a three-dimensional full-flow passage as an alternative analysis method for the cavitation flow. The results indicated that the re-entrant jet is the main cause of the shedding cavitation and breaking O-type cavitation. The re-entrant jet is driven by the reverse pressure gradient to move upstream towards the stator nose, and it lifts and splits the attached cavitation, which periodically induces shedding cavitation. When the cavitation was considered, the prediction error of the capacity constant was reduced from 13.23% to <5%. This work provides an insight into the cavitation–vortex interactions in a hydrodynamic torque converter, which can be used to improve the prediction accuracy of the hydrodynamic performance.

Calculation and analysis of thermal flow field in hydrodynamic torque converter with a new developed stress-blended eddy simulation

Purpose The flow phenomenon of particle image velocimetry has revealed the transition process of the complex multi-scale vortex between the boundary layer and mainstream region. Nonetheless, present computational fluid dynamics methods inadequately distinguish the discernable flows in detail. A multi-physical field coupling model, which was applied in rotor-stator fluid machinery (Umavathi, 2015; Syawitri et al., 2020), was put forward to ensure the identification of multi-scale vortexes and the improvement of performance prediction in torque converter. Design/methodology/approach A newly-developed multi-physical field simulation framework that coupled the scale-resolving simulation method with a dynamic modified viscosity coefficient was proposed to comparatively investigate the influence of energy exchange on thermal and flow characteristics and the description of the flow field in detail. Findings Regardless of whether quantitative or qualitative, its description ability on turbulence statistics, pressure-streamline, vortex structure and eddy viscosity ratio were visually experimentally and numerically analyzed. The results revealed that the modification of transmission medium viscous can identify flows more exactly between the viscous sublayer and outer boundary layer. Compared with RANS and large eddy simulation, a stress-blended eddy simulation model with a dynamic modified viscosity coefficient, which was further used to achieve blending on the stress level, can effectively solve the calculating problem of the transition region between the near-wall boundary layer and mainstream region. Research limitations/implications This indeed provides an excellent description of the transient flow field and vortex structure in different physical flow states. Furthermore, the experimental data has proven that the maximum error of the external performance prediction was less than 4%. Originality/value An improved model was applied to simulate and analyze the flow mechanism through the evolution of vortex structures in a working chamber, to deepen the designer with a fundamental understanding on how to reduce flow losses and flow non-uniformity in manufacturing.

Multi-objective optimization of the cascade parameters of a torque converter based on CFD and a genetic algorithm

It is hard to simultaneously improve the peak efficiency (η *) and the width of the high-efficiency region ( Gη) for a hydrodynamic torque converter. A combination of comprehensive CFD simulation and multi-objective optimization was pretested. The elaborate CFD simulation calculation included a reasonable mesh layout, a robust algorithm and a correct turbulence model, whose results were also experimentally verified. In our study, the Kriging surrogate model was first used to construct a nonlinear relationship between the inlet and outlet angle and the economic performance index of the hydrodynamic torque converter. To ensure that the accuracy of the surrogate model meet the requirements, we also used 10 sets of sample points to verify the accuracy of our surrogate model. The accuracy is found to meet the requirements, which shows that the accuracy of the constructed surrogate model is relatively high. We choose to apply the second-generation non-dominant sorting genetic algorithm (NSGA-II) to solve our problem. After solving the Pareto frontier solution set, we obtain a set of global optimal solutions on the Pareto frontier solution set. The optimization results show that the η * is increased by 2.49% and that the Gη is increased by 14.23%. We extracted the flow field structure near the turbine region, characterized the difference between original and optimal model from the flow field perspective, and demonstrated the accuracy of our optimization results. Finally, we used CFD to verify our optimization results, further illustrating the accuracy of the optimization results prediction. Literature research indicates that a large amount of experiments to optimize the η * and the Gη of the hydrodynamic torque converter will bring huge trial cost and time cost. We conclude from our research that the proposed calculation method can solve such problems well.

КИНЕМАТИКА МНОГОСТУПЕНЧАТЫХ СОГЛАСУЮЩИХ РЕДУКТОРОВ ДЛЯ ГИДРОТРАНСФОРМАТОРОВ

The study offers a design solution for online capacity adjustment of hydrodynamic torque converter powertrains. It is proposed to install a step-less speed drive or multistage matching gearbox between the engine and the torque converter to adjust the powertrain properties on the move depending on the current operating conditions. We propose the matching device arrange-ments. The solutions can be used in buses, trucks, tractors, diesel locomotives, etc. that operate in a wide range of external loads.

Experimental Study of Comfortableness during Hydrodynamic Torque Converter Lockup in a Construction Machinery

The comfortableness during hydrodynamic torque converter lockup in a construction machinery is investigated in this study. A motor grader is chosen as a typical construction machinery. Standard ramps are used to simulate stable working load. It is found that at conditions of flat road, the hydrodynamic torque converter locks at coupling condition, resulting in small acceleration fluctuation, little vibration dose value (VDV), and comfortable process. At ramp conditions, the hydrodynamic torque converter uses a traditional lockup strategy, which is possible to extend lockup status to higher load range. However, before the lockup process, the speed and torque differences between impeller and turbine wheels are larger. During the lockup process, the large speed difference leads to high engine inertia energy releasing rate. The large torque difference leads to high demanded engine torque change, which extends the engine adjustment ability and causes torque fluctuation. With a joint effect, three obvious acceleration fluctuations are observed, the VDVs become larger, and the lockup process becomes uncomfortable. As load increases, the comfortableness intends to get worse.

Prilog analitičkom izračunavanju performansi motornog vozila sa ugrađenim hidrauličkim transformatorom obrtnog momenta

Hydrodynamic torque converters (hereinafter referred to as HDTC) are becoming increasingly widespread in motor vehicles. The internal combustion engine (ICE) and the HDTC system can be viewed as one aggregate the output characteristics of which are uniquely defined by the characteristics of the engine and the corresponding HDTC. Namely, the engine and the hydro-converter can be considered as one system, with a precisely defined output torque and output angular velocity. This creates a possibility that the drive force can be calculated as if it is a mechanical transmission, in which the output torque of the hydro-converter is the input into the planetary gears train (if any). Harmonizing the joint work of the ICE-HDTC is a complex process. An attempt has been made in this paper to make a model of the aforementioned system in order to harmonize more easily the characteristics of the combined operation of the internal combustion engine and the HDTC. .

Pressure Measurement and Analysis of Stator Blade Surface of Hydrodynamic Torque Converter

Pressure Measurement and Analysis of Stator Blade Surface of Hydrodynamic Torque Converter

Split power hydro-mechanical transmission with power circulation

ABSTRACTThis paper presents a novel hydrodynamic-mechanical split power transmission (US patent application No. 15695671, and PL patent application No. P.422664) with an exceptionally large torque ratio and torque ratio growth rate, and a potentially wide range of (continuous and naturally automatic) torque ratio variation. The transmission features a strong positive feedback between rotors of the impeller and turbine, and makes a systematic use of power circulation (which is present in all transmissions using a hydrodynamic torque converter). The transmission is particularly suitable for vehicles and working machines operating in a start–stop mode and those subjected to heavy, fast-changing external loads, like city buses, wheel and track loaders, dozers, farm tractors, and small earth-moving machines, and most of all for emergency, military, and sports vehicles, where good acceleration is of the highest priority.

Large eddy simulation for improvement of performance estimation and turbulent flow analysis in a hydrodynamic torque converter

ABSTRACTComputational fluid dynamics (CFD) has been widely applied as an effective tool for optimizing products and reducing production cycles in many industrial fields; consequently, engineers are constantly pursuing higher accuracy in the performance predictions of CFD methods. In this paper, an analysis for the flow field of a hydrodynamic torque converter (TC) is conducted to evaluate CFD applications in detail. In the past, Reynolds-averaged Navier–Stokes (RANS) simulations have always played a dominant role in the numerical modeling of TCs because of their efficient calculation speed. However, most RANS models are unable to capture the complicated transient flows whose performance estimation errors are generally greater than 10%. Therefore, large eddy simulation (LES) with various sub-grid scale (SGS) models are applied in order to explore feasible methods for improving numerical accuracy and capturing the detailed transient flow phenomena. The effectiveness of the LES method is verified by comparing the numerical results with experimental data. Although the grid resolution is not fine enough due to the limitations of the high-performance computer (HPC) used, LES with dynamic kinetic energy transport (KET) models were still able to obtain an excellent description of both the near-wall flow and the main-stream flow via quantitative and qualitative analyses. The maximum error in the capacity factor (CF) is remarkably reduced to 4.4%. It is therefore beyond doubt that applying LES methods using coarser grid resolutions can still guarantee higher prediction accuracy through the reasonable selection of SGS models, which can effectively reduce the computing capacity requirements and contribute to the design process of TCs.

Scale-resolving Simulation of Thermal Flow and Accurate Performance Prediction in Hydrodynamic Torque Converter

Scale-resolving Simulation of Thermal Flow and Accurate Performance Prediction in Hydrodynamic Torque Converter

CFD investigating medium-temperature influences on performance prediction and structure stress calculation in a hydrodynamic torque converter

ABSTRACTWhen computational fluid dynamics was applied in a hydrodynamic torque converter, the influences of medium temperature were always ignored. Those influences were investigated in this study. The variable viscosities and constant viscosity were carried out by a comparative study. The unsteady flow fields showed the variable viscosities results were more reasonable, whereas the constant viscosity overestimated the viscous force and leaded to inaccuracy in performance prediction. The experimental data proved that variable viscosities achieved a highly accuracy, and the performance prediction inaccuracy was 1–4%. Through the comparative analysis of the equivalent stress and deformation computed from thermal-fluid–structure interaction and fluid–structure interaction, the thermal stress from medium-temperature influence should be considered during the design of a torque converter.

Flow simulation in hydrodynamic torque converter

Flow simulation in hydrodynamic torque converter