Hongbin Mu, Qingdong Yan and Wei Wei
Traditional prediction of braking characteristics of vehicular hydrodynamic retarders is commonly conducted based on braking characteristics model of closed working chamber…
Abstract
Purpose
Traditional prediction of braking characteristics of vehicular hydrodynamic retarders is commonly conducted based on braking characteristics model of closed working chamber, namely, closed working chamber model (CWCM). In CWCM, inlet and outlet oil pressures and braking torque are considered to be independent of inlet and outlet flow rates. However, inlet and outlet flow rates can affect internal and external braking characteristics under actual working conditions. This study aims to establish a more accurate braking characteristics model of a hydrodynamic retarder under full oil-charging condition, and then the influence of varying inlet and outlet flow rates on oil pressures and braking torque is investigated in this paper.
Design/methodology/approach
A full flow passage of working chamber in a hydrodynamic retarder with inlet and outlets was established, and the reliability of numerical model was analyzed and validated. Pressure rise was introduced to describe the variation of inlet and outlet oil pressures. Then, on the basis of the validation, the CWCM was proposed at different rotor rotational speeds. The inlet and outlet oil pressures and braking torque were numerically computed at different inlet and outlet flow rates with Full Factorial Design experimental method. The results obtained were involved into establishing the braking characteristics model of open working chamber, namely, open working chamber model (OWCM), combined with Radial basis function approximation model. The OWCM with different inlet and outlet flow rates was analyzed and compared with CWCM.
Findings
The results show that inlet and outlet flow rates have obvious influence on the variation of inlet and outlet oil pressures in OWCM compared with CWCM. The outlet A pressure rise significantly changes with the inlet and outlet A flow rates, while the pressure rise of outlet B is mainly affected by the outlet B flow rate.
Originality/value
This paper presents an OWCM of hydrodynamic retarders under full oil-charging condition. The model takes into account the impact of oil inflowing and outflowing from the working chamber, which can provide a more accurate prediction of braking characteristics of hydrodynamic retarders.
Details
Keywords
Hongbin Mu, Wei Wei, Alexandrina Untaroiu and Qingdong Yan
Traditional three-dimensional numerical methods require a long time for transient computational fluid dynamics simulation on oil-filling process of hydrodynamic braking. The…
Abstract
Purpose
Traditional three-dimensional numerical methods require a long time for transient computational fluid dynamics simulation on oil-filling process of hydrodynamic braking. The purpose of this paper is to investigate reconstruction and prediction methods for the pressure field on blade surfaces to explore an accurate and rapid numerical method to solve transient internal flow in a hydrodynamic retarder.
Design/methodology/approach
Dynamic braking performance for the oil-filling process was simulated and validated using experimental results. With the proper orthogonal decomposition (POD) method, the dominant modes of transient pressure distribution on blades were extracted using their spatio-temporal structural features from the knowledge of computed flow data. Pressure field on blades was reconstructed. Based on the approximate model (AM), transient pressure field on blades was predicted in combination with POD. The causes of reconstruction and prediction error were, respectively, analyzed.
Findings
Results show that reconstruction with only a few dominant POD modes could represent all flow samples with high accuracy. POD method demonstrates an efficient simplification for accurate prediction of the instantaneous variation of pressure field in a hydrodynamic retarder, especially at the stage of high oil-filling rate.
Originality/value
The paper presents a novel numerical method, which combines POD and AM approaches for rapid and accurate prediction of braking characteristics during the oil-filling period, based on the knowledge of computed flow data.
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Xiaobing Fan, Bingli Pan, Hongyu Liu, Shuang Zhao, Xiaofan Ding, Haoyu Gao, Bing Han and Hongbin Liu
This paper aims to prepare an oil-impregnated porous polytetrafluoroethylene (PTFE) composite with advanced tribological properties using citric acid as a novel pore-forming agent.
Abstract
Purpose
This paper aims to prepare an oil-impregnated porous polytetrafluoroethylene (PTFE) composite with advanced tribological properties using citric acid as a novel pore-forming agent.
Design/methodology/approach
Citric acid (CA) was used to form pores in PTFE, and then oil-impregnated PTFE composites were prepared. The pore-forming efficiency of CA was evaluated. The possible mechanism of lubrication was proposed according to the tribological properties.
Findings
The results show CA is an efficient pore-forming agent and completely removed, and the porosity of the PTFE increases with the increase of the CA content. The oil-impregnated porous PTFE exhibits an excellent tribological performance, an increased wear resistance of 77.29% was realized in comparison with neat PTFE.
Originality/value
This study enhances understanding of the lubrication mechanism of oil-impregnated porous polymers and guides for their tribological applications.
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Keywords
Xuening Fei, Yuanyuan Li, Shuai Li, Lingyun Cao, Dajie Xing, Bingyang Cheng, Meitong Li and Hongbin Zhao
This study aims to realize the multipurpose use of inorganic materials in adsorption treatment of pigment wastewater and preparation of core-modified Color Index Pigment Red 57:1…
Abstract
Purpose
This study aims to realize the multipurpose use of inorganic materials in adsorption treatment of pigment wastewater and preparation of core-modified Color Index Pigment Red 57:1 (C.I. Pigment Red 57:1, PR 57:1).
Design/methodology/approach
In this paper, the inorganic materials (sepiolite and SiO2·nH2O) were used in both PR 57:1 production wastewater treatment and its core-modification. The inorganic material firstly adsorbed 3-hydroxy-2-naphthoic acid (bon acid) in the pigment wastewater to reduce chemical oxygen demand. Then, the inorganic material adsorbed with bon acid was reused to prepare core-modified PR 57:1.
Findings
In the pigment wastewater adsorption experiment, it was found that under pH = 3, the adsorption percentage of bon acid by inorganic material can reached up to 46.00%. The pigment characterization results showed that the core-modified PR 57:1 had a core-shell structure. Under UV light irradiation for 1 h, the core-modified PR 57:1 prepared with sepiolite and SiO2·nH2O showed total color difference ΔE value of 1.43 and 2.05, respectively, which was lower than that of unmodified PR 57:1 (ΔE = 2.89). In addition, the transmittance of pigment water suspension test results showed that the core-modified PR 57:1 showed better water dispersibility.
Originality/value
This paper attempts to develop a synergistic strategy based on the multipurpose use of inorganic materials in adsorption treatment of pigment wastewater and preparation of core-modified PR 57:1.