Dynamic Analysis of the Lubrication in a Wet Clutch of a Hydromechanical Variable Transmission

Bassi, Andrea; Milani, Massimo; Montorsi, Luca; Terzi, Stefano

doi:10.4271/2016-01-8099

Cited by 8 publications

(3 citation statements)

References 13 publications

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“…While the first type is very well investigated in the literature as the single most important flow component between rotating discs, the superposition of the squeeze-flow on the previous one is not fully studied yet. Indicatively, in relative studies, the axial (closing) velocity is not considered and the modeling implies fluid supply to the system from an external flow source located at the inner radius [3][4][5]11,13,17]. This model takes into account the gap closing velocity, which however does not lead to an exactly equivalent formulation with respect to the literature due to the fact that the axial velocity of the top disc is a product of an actuation force variable with time and highlights many of the undesirable characteristics of wet clutches (i.e., fluctuations in position due to high fluid inertia as small fluid volume is concentrated and activated via a hydraulic actuator).…”

Section: Geometry Modifications and Basic Parametersmentioning

confidence: 99%

Nondimensional Characterization of the Operational Envelope of a Wet Friction Clutch

et al. 2020

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In recent years, multidisc wet friction clutches are used in demanding powertrains of automatic and dual clutch transmissions targeting high efficiency and smoothness during gearshift. However, the developed flow pattern between the clutch discs is significantly complex and the Computational Fluid Dynamics (CFD) methods employed are quite demanding in terms of computational cost. To deal with this issue semi-analytical solutions were derived, which are limited, however, to specific problems, in order to obtain handy expressions, while also providing insight to the wet clutch physics. Nevertheless, this lack of global validity is counterbalanced by the fact that the governing equations become analytically solvable at specific operational conditions with satisfactory accuracy, provided that the simplifications rendering the truncated terms inactive hold true. In this work, a quantitative way of determining the relative weight of each term of the Navier-Stokes (NS) equations set is presented, based on the post-processing of CFD results using the Buckingham “π-theorem”. The sets of nondimensional numbers created were used to describe and model the physics of the wet clutch.

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Section: Geometry Modifications and Basic Parametersmentioning

confidence: 99%

Nondimensional Characterization of the Operational Envelope of a Wet Friction Clutch

et al. 2020

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“…More accurate studies were realized considering twophase models ( [10], [11], [12], [13], [7]) of the oil/air mixture, implementing the Volume of Fluid method mainly. Then, most of the current studies focus mainly on single discs analysis or single steel-disc coupling ( [14], [15], [16], [17], [18]), where the influence of the different geometric pattern was demonstrated to be a fundamental parameter ( [19], [20], [21]) , while few exist that investigated more elaborated geometries ( [22], [23], [24]). With the studies operated on the clutches is possible in the end to use all this methodologies to study the braking systems, that as written before is a specular system working under similar physic conditions, but with the main mechanism that is inverse, so the engaging between the elements that leads to the deceleration of te system until its rest.…”

Section: Introductionmentioning

confidence: 99%

Detailed CFD transient heat transfer modelling in a brake friction system

Orlandi

Milani²,

Montorsi³

2022

J. Phys.: Conf. Ser.

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In a brake system the contact between the friction grooves of the discs and the steel elements leads to a consistent heat dissipation that is excised by the oil thermal vector in its flowing along the grooves channels. These are very complicated physical system were many variables may be taken in consideration, first of all the extensive integration of the different time scheduling actions that take place and that characterizes the translation of the interacting bodies and the correspondent deceleration, and also the heat dissipation derived from this contact. The simulations of similar physical system may result in too expensive computational efforts leading to very complicated simulations that need to take in account an extensive coupling between many physics, first of all the solid/liquid heat transfer and then the turbulence and the bi-phase models for the oil/air mixture that serves as thermal refrigerator vector in the braking system. Herein a simplified 3D model that focuses only on a discs / piston coupling is presented were the braking action is simulated in a simplified way modelling the velocity of rotation of the elements and the dissipated heat during the braking cycle. Focusing on the grooves channels the oil flows and thermal averaged flows are presented and detail contours are used to characterise a single brake event.

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“…This is usually performed by applying the necessary CFD analysis to solve the governing flow equations. The numerical treatment of the flow dynamics problem is very common and effective and leads to the conclusion of case-spesific results about the effect of a MATEC Web of Conferences 287, 01018 (2019) https://doi.org/10.1051/matecconf/201928701018 Power Transmissions 2019 variety of design parameters on the reponse of the clutch [1][2][3][4]. On the other hand, the incorporation of such methods in the modelling of complete power transmission systems involving wet multidisc clutches [5], [6] (such us the well-known double clutch ATs) makes the total simulation proccess of the power-train consuming in terms of time and recourses.…”

Section: Introductionmentioning

confidence: 99%

Fast modelling and simulation of the dynamic behaviour of a wet multidisc clutch during the engagement phase

et al. 2019

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In recent years multidisc wet friction clutches are of great importance to manufacturers of automatic transmissions (ATs) for the automotive industry, particularly since the introduction of double-clutched ATs. Their main advantage compared to their dryfriction counterparts is that they ensure smooth engagement, high reliability and long service life. Their progressive engagement due to the developed Couette flow between the discs enables them to be used both as clutches and as brakes in order to control power flow in simultaneously engaged geared shafts in the AT. Due to the coupled nature between the mechanical and the fluid dynamics regimes governing their operation, these systems are highly complex to be treated analytically and instead numerical approaches have proven to provide better results. However, the numerical treatment of such problems provides only case-specific results, which cannot be generalised and are not able to provide a general insight in the complex dynamics of the device. Furthermore the computational cost and the associated modelling and simulation effort during the design phase is high, making the incorporation of such methods in iterative design processes and algorithms counterproductive. In this paper the modelling of the dynamic behaviour of a wet multidisc clutch during the engagement phase is performed, via the combination of analytical and numerical methods and conclusions are drawn about the effect of the main geometric, kinematic and dynamic design parameters on the clutch's response. The dynamic modelling is performed by applying the principle of linear and angular momentum on each disc. The effect of the fluid film is taken into account through the solution of the governing Navier-Stokes equations via CFD analysis or by the use of semianalytical solutions with high accuracy, where applicable. Therefore both the developed pressure field and the torque of the fluid film are calculated efficiently and used in the simulation of the system. The flow is assumed to be laminar and the discs rigid and flat.

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Dynamic Analysis of the Lubrication in a Wet Clutch of a Hydromechanical Variable Transmission

Cited by 8 publications

References 13 publications

Nondimensional Characterization of the Operational Envelope of a Wet Friction Clutch

Nondimensional Characterization of the Operational Envelope of a Wet Friction Clutch

Detailed CFD transient heat transfer modelling in a brake friction system

Fast modelling and simulation of the dynamic behaviour of a wet multidisc clutch during the engagement phase

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