Herringbone Grooves Research Articles

Intensification of isobutane/1-butene alkylation process in a micromixing microreactor catalyzed by ILs/H2SO4

The products of isobutane/butene alkylation are ideal high-octane blending components of gasoline pool. Binary mixtures of acidic imidazolium ionic liquids [CnMIm][OTf] (n = 4, 6, 8) and H2SO4 were used to catalyze isobutane/butane alkylation in a microreactor integrated with staggered herringbone grooves. The mixing behaviors of acid and hydrocarbons were simulated in the microchannel configured with micromixing elements by computational fluid dynamics (CFD) simulation. [CnMIm][OTf]/H2SO4 showed better catalytic performance than H2SO4 solely. Especially the [OMIm][OTf]/H2SO4 showed excellent performance. In the designed microreactor, the alkylate with research octane number (RON) of 99.5 was obtained at 10.0°C and reaction time of 81 s with [OMIm][OTf]/H2SO4 as catalyst. The results are better than currently available research works implemented in batch reactors. The catalyst [OMIm][OTf]/H2SO4 was recycled 14 times without reducing the catalytic activity. It indicates that the composite catalysts possess excellent reutilization performance.

Parametric and comparative study on enhanced microchannel membrane-based absorber structures for compact absorption refrigeration

Novel and simple enhancement structures are proposed to improve the absorption characteristics of flat membrane-based absorbers. Firstly, a parametric study is conducted to elucidate the effect of membrane parameters on the absorption process using a two-dimensional CFD model. Results indicate that the most critical membrane parameter affecting the absorption rate is the membrane porosity compared with the membrane thickness and pore diameter. The recommended membrane porosity, pore diameter, and thickness are 0.8, 1 μm, and 60 μm, respectively. Then, a comparative study on the proposed enhancement structures is carried out. Results demonstrate that inclined groove induces solution swirling while increasing the effective heat transfer areas, and thus the absorption performance is significantly improved at lower solution pressure drops. Flow visualization shows that two counter-rotating vortices are generated inside HG (herringbone groove) and SHG (staggered herringbone grove) structures, and the longitudinal swirling flows are induced inside IG (inclined groove) and SIG (staggered inclined groove) structures. Comparisons indicate that the HG structure improves the absorption rate by 1.62 times, reducing the solution pressure drop by 19.01%. These changes from the IG structure are 1.56 and 20.77%, respectively. Therefore, the IG and HG structures are recommended.

Structural Design and Optimization of Herringbone Grooved Journal Bearings Considering Turbulent

In order to improve the performance of the traditional constant-width herringbone grooved journal bearing in a computed tomography tube under a high-temperature environment, the present study designed a convergent herringbone grooved journal bearing (HGJB) structure lubricated by liquid metal. The bearing oil film thickness and the Reynolds equation considering the influence of turbulence are established and solved by using the finite difference method in the oblique coordinate system. The performance of the two bearings was compared, and the static and dynamic performance change trends of the two bearing structures under different eccentricities were systematically studied. The results show that the convergent herringbone grooved journal bearings are superior to the constant-width herringbone grooved journal bearings in terms of bearing capacity and stiffness coefficient. At the same time, the influence of structural parameters, such as the number of grooves, helix angle, groove to ridge ratio, groove depth on the performance of the constant-width herringbone grooved journal bearings, and the convergent herringbone grooved journal bearings was studied. Finally, we conclude that the performance of the convergent herringbone grooved journal bearings is optimal when the number of grooves is 15–20, the helix angle is 30°–45°, the ratio of the groove to ridge is 1, and the groove depth is 0.02 mm –0.024 mm. This research has provided the thinking and reference basis for the design of liquid metal bearings for high-performance CT equipment.

Numerical investigation on sealing performance of non-contact finger seal with herringbone groove surface topography

Since the last decade, the non-contact finger seal (NCFS) has attracted an increasing number of researchers due to its inherent flexibility and non-contact features, which can significantly improve the service life and reduce the leakage rate of the finger seals. In this paper, to enhance the NCFS sealing performance, lifting pads with twenty (20) different herringbone groove surface topographies are proposed based on the uniform design method. Numerical analysis is carried out based on the two-way fluid-structure interaction (FSI) method to better mimic the actual working conditions. The analysis of results using statistical tools reveals that the herringbone groove topographies placed on the bottom surface of low-pressure lifting pads can significantly improve the load-carrying capacity and sealing performance. In addition, the correlation analysis of the sealing performance and geometric parameters of the herringbone groove demonstrate that reducing the groove width or increasing the groove internal angle can improve the lifting and leakage capacities. Finally, the optimal herringbone groove and general structure (no groove) are comparatively analysed under variable working conditions, and the results show that the former has much better sealing performance.

Cover Picture: Materials and Corrosion. 10/2021

Cover:The influence of an embossing process on the microstructure and corrosion behavior of Al—1.1 wt%Mn strips used in the manufacturing of high‐frequency welded microfin tubes was studied. The optical and electron microscopic images, X‐ray tomography and FIB cross‐sectional analysis on the cover page present an overall view of deformation asymmetry caused by embossing and its influence on different corrosion behaviors at each side of the corroded embossed fins.More detailed information can be found in: Giorgio Giovanni Battista Zaffaroni, Visweswara Chakravarthy Gudla, Simone Laganá, Carsten Gundlach, Bjorn Olsson, Rouhollah Yazdi, Jan Halvor Nordlien, Rajan Ambat, Microstructure—Dependent Corrosion of Herringbone Grooved Embossed Al‐1.1 wt%Mn Strips for Heat Exchanger Tubes, Materials and Corrosion 2021, 72, 1582.

Leakage-free optimization of micro herringbone grooved journal bearings with a virtual node method

PurposeThis study aims to develop a new method to treat the numerical singularity at the critical nodes of two skew coordinates, and optimize the leakage of micro herringbone grooved journal bearings (MHGJBs) with this method.Design/methodology/approachA side leakage numerical algorithm is proposed by using the skew meshes with a virtual node (SMVN) method to evaluate the effects of groove angle, bank/groove ratio, groove depth and groove number on load capacity, friction and side leakage of MHGJB.FindingsThe SMVN method is effective in treating the numerical singularity at the critical nodes of two skew coordinates. Besides, a group of optimized parameters of micro herringbone groove is obtained which can not only minimize the side leakage but also improve the load capacity and friction force.Originality/valueA virtual node method was proposed, which can significantly improve the calculation accuracy in the side leakage model.

More efficient wind turbine blade design inspired by owl wings and feathers

Incorporating the cross-section airfoils of an owl’s wing, coupled with the herringbone groove structure of an owl’s feature, leads to better aerodynamic performance.

Investigation on aerodynamic performance of wind turbine blades coupled with airfoil and herringbone groove structure

The advantage of wind energy is significant to the improvement of energy structure. This paper is mainly to demonstrate a bionic design for wind turbine blades inspired by the airfoil of owl wing and the herringbone groove structure of owl feathers. The blade of A 200 W horizontal axis wind turbine is taken as prototype blade. The design of bionic airfoil blade is based on 50% and 70% cross section airfoils of owl wing, which is combined with the parameters of the prototype blade. The design of bionic coupling blade is based on bionic airfoil blade, which is coupled with the herringbone groove structure. Numerical simulation is utilized to study the aerodynamic performance of all blades. These simulations utilize an incompressible Reynolds-averaged Navier–Stokes solver and shear stress transport k–ω turbulent model at different tip speed ratios (TSRs). Results show that the power coefficient (Cp) of bionic airfoil blades is higher than that of prototype blade in the TSR of 6–9; the Cp of bionic coupling blades is higher than that of bionic airfoil blades in the TSR of 6–10. The larger curvature of leading edge of blades leads to larger flow velocity, which leads to the smaller pressure on the leeward surface. The herringbone groove structure enhances the flow attachment by generating vortices, which reduces the pressure on the leeward surface of bionic coupling blades. Compared with the prototype blade and bionic airfoil blade, the pressure difference between the windward surface and the leeward surface of the bionic coupling blade is larger.

Abrasive jet machining for the microprofile control patterning of herringbone grooves

Fluid bearings have features of high speed and high rotation accuracy, and therefore, they are used in spindle motors of hard disk drives, cooling fans of central processing units, and other devices. Further, these bearings have microherringbone grooves on the shaft or sleeve inner surface that help generate dynamic pressure in the lubricant fluid around the shaft. Although the depth of the groove is constant, dynamic pressure can be increased by decreasing the depth from both ends to the central corner of each groove on a micron scale. This study aims to verify the effect of sloped herringbone grooves using computational fluid dynamics (CFD) analysis and to develop a new microfabrication method for manufacturing microsloped herringbone grooves on the shaft surface using abrasive jet machining. The generated dynamic pressure is analyzed using CFD; the results indicated that the sloped herringbone grooves result in an increase in the dynamic pressure at the groove tips and cause a decrease in the fluctuations in dynamic pressure in the circumferential direction.

Unstable tilting motion of flexibly supported gas bearing bushings

This paper presents measurements of the motion amplitudes from flexibly supported Herringbone Grooved Journal Bearing bushings. Measurements taken in four locations on the flexibly supported bearing bushing enable the distinction between the radial and the tilting motion, which allowed to identify an unstable bearing bushing tilting mode. The bushing tilting motion instability can be attributed to the cross-coupled tilting impedance of the gas bearing and its occurrence is characterized by the appearance of a sub-synchronous vibration at the speed of instability onset. The comparison between experimentally obtained data and the prediction of a two degrees of freedom dynamic model that includes the flexible support characteristics, the bushing transverse inertia as well as the gas bearing tilting impedance suggests an excellent agreement on both the Eigenfrequency and the rotor speed of instability onset. Furthermore, the effect of the flexible support tilting stiffness and bearing bushing transverse moment of inertia on the critical bushing tilting speed and onset of tilting instability has been investigated, which led to a design guideline to avoid the onset of an unstable bush tilting mode. In addition, experimental data gathered after the introduction of damping in the flexible support of the bearing bushing suggests a significant increase of the onset speed of the unstable bearing bushing tilting mode.

Study on static characteristics of water-lubricated textured herringbone grooved journal bearings based on laminar cavitating flow lubrication model

This paper aims to investigate static characteristics of water-lubricated textured herringbone groove journal bearing under laminar cavitating flow. A theoretical model for the bearing was established based on two-phase flow and population balance equation. Field distribution and static characteristics of the bearing are analysed. The result shows the friction torque of the bearing is reduced due to the texture effect; And the frictional torque is reduced with the increasing of texture area ratio and height. The load carrying capacity of the bearing is increased, while the friction torque are slightly affected by the cavitation effect. The existence of texture increases the bubble number density in the bearing-lubrication process.

Optimization of Herringbone Grooved Thrust Air Bearings for Maximum Load Capacity

Abstract Many studies in herringbone grooved thrust bearings are focused on searching for the optimal groove parameters to improve the load capacity, but none of them adopt different grooves in different sections. In this study, a novel optimization method of herringbone grooved thrust air bearings is proposed for maximum load capacity by seeking the optimal groove parameters in each section of the bearing independently. An example of an optimized thrust air bearing is presented, and its performance is compared with a non-optimized bearing and a conventionally optimized bearing without dividing grooves into sections. The resultant herringbone grooves are found to have different parameters in the inner and outer sections, which is uncommon in existing grooves. Numerical results show that the novel bearing has a higher load capacity than the non-optimized reference bearing and conventionally optimized bearing. The study shows that the new design can increase load capacity by 30.77%, verified by experiments.

Design and application of a self-pumping microfluidic staggered herringbone mixer

The rapid mixing of reagents is critical to a wide range of chemical and biological reactions but is difficult to implement in microfluidic devices, particularly in capillary action/passive pumping devices or in point-of-need environments. Here, we develop a self-pumping asymmetric staggered herringbone mixer made from only laser-ablated glass and tape. This lab-on-a-chip platform is capable of rapid flow (0.14 mL min−1, 1 cm s−1) and fast mixing (< 10 s) without external forces or pumps and is amenable to the flow of non-aqueous solvents. Furthermore, the degree of mixing and flow rates are easily tunable through the length and depth of the herringbone grooves, and the thickness of the double-sided tape that defines the channel height, respectively. The device utility is demonstrated for chemical and biological assays through the reaction of Ni(II) and DMG in ethanol/water and the enzymatic reaction of o-dianisidine with peroxidase, respectively.

An Experimental Study of In-Tube Condensation and Evaporation Using Enhanced Heat Transfer (EHT) Tubes

A study was carried out to determine in-tube evaporation and condensation performance of enhanced heat transfer tubes (EHT) using R410A, with the results being compared to a plain tube. The test tubes considered in the evaluation include: plain, herringbone (HB) and spiral (HX) microgrooves, herringbone dimple (HB/D), and hydrophobic herringbone (HB/HY). Experiments to evaluate the condensation were conducted at a saturation of 318 K, and at 279 K for evaporation. Mass flux (G) ranged between 40 to 230 kg m−2s−1. Condensed vapor mass decreased from 0.8 to 0.2; and the mass of vaporized vapor increases from 0.2 to 0.8; heat flux increased with G. Inlet and outlet two-phase flow patterns at 200 kg m−2s−1 were recorded and analyzed. Enhanced tube heat transfer condensation performance (compared to a plain tube) increased in the range from 40% to 73%. The largest heat transfer increase is produced by the herringbone–dimple tube (HB/D). In addition to providing drainage, the herringbone groove also helps to lift the accumulated condensate to wet the surrounding wall. Evaporation thermal performance of the enhanced tubes are from 4% to 46% larger than that of smooth tube with the best performance being in the hydrophobic herringbone tube (HB/HY). This enhancement can be attributed to an increase in the number of nucleation sites and a larger heat transfer surface area. Evaporation and condensation correlations for heat transfer in smooth tubes is discussed and compared.

Analysis of condensation and evaporation heat transfer inside 3-D enhanced tubes

An experimental investigation was conducted to evaluate heat transfer performance of several enhanced surface tubes during in-tube evaporation and condensation of R410A; results were then compared to the results of a smooth tube. Tubes considered in this evaluation included: smooth; herringbone and helix micro-grooves; herringbone-dimple and hydrophobic; all the tubes evaluated have the same external diameter of 12.7 mm. Experimental condensation and evaporation results were acquired at saturation temperatures of 318 K and 279 K, respectively. The mass velocities varied in the range of 40–230 kg m−2 s−1; vapor quality decreased from 0.8 to 0.2 for condensation and 0.2 to 0.8 for evaporation. Moreover, heat fluxes increased with mass velocity. Condensation heat transfer coefficients (HTCs) are enhanced by 40%–73%, with the dimpled herringbone-finned tube (EHT-HB/D) exhibiting the highest HTC among five tested tubes. The herringbone grooves can help lift the accumulated condensate along the circumference in addition to producing the drainage effects; dimples produce condensate turbulence and the droplet entrainment. For the evaporation, hydrophobic herringbone tube (EHT-HB/HY) provides the best thermal performance; its HTCs are 4%–46% larger than those of the smooth tube. This enhancement may be attributed to the expanded heat transfer area and the increased nucleation sites.

Temperature rise of journal bearing of the high-speed circular arc gear pump

A “circular arc–involute–circular arc” circular arc gear pump was developed based on a gear meshing principle and coordinate transformation as well as an accurate calculation model of the radial force. The dependence of the radial force on the meshing angle was investigated. The temperature rise of journal bearings in the pump was evaluated for bearings with and without herringbone grooves. Furthermore, the influence of the rotational speed and outlet pressure on this rise was assessed. The results revealed using herringbone groove on the inner wall of bearing was effective in reducing the temperature increase. Therefore, the use of grooves represents a suitable method of reducing the temperature rise in the journal bearings of a high-speed gear pump.

Dynamic force coefficients identification on air-lubricated herringbone grooved journal bearing

Abstract The Narrow Groove Theory (NGT) is commonly used to simulate and design grooved gas bearing. However, measurements of dynamic force coefficients of Herringbone Grooved Journal Bearings (HGJBs) is missing, hence the validation historic NGT has never been performed, despite its importance. A test rig was built in order to identify stiffness and damping coefficients of HGJBs of a rotor perturbed by piezo-electric shakers. Results indicate that the NGT captures the qualitative behavior of HGJB well but tends to overestimate the stiffness and damping coefficients by 23 and 29% respectively. Gravity led to a eccentricity ratio in excess of 15% without significant effect. The direct damping coefficient was found to be mildly non-linear with the excitation amplitude.

Effects of herringbone grooves on aerodynamic journal bearings based on finite element method

Aerodynamic journal bearings are commonly used in high speed machines, which have weaknesses of low steady-state performance specifications. It is of great significance to study the effects of herringbone grooves on the characteristics of aerodynamic journal bearings. This paper investigates effects of herringbone grooves on functions of aerodynamic journal bearings by numerically solving the Reynolds equation based on improved finite element method. The obtained results show that the herringbone grooved aerodynamic journal bearings have a critical speed and they should run at a speed of greater than the critical speed. Ultra-high speeds and low eccentricity ratios are the suitable working conditions of the herringbone grooved aerodynamic journal bearings. The performance of aerodynamic journal bearings is enhanced with advancing groove numbers, and an optimal groove depth is existed with respect to the herringbone grooved aerodynamic journal bearing.

A Simulation Study on the Behavior of Magnetorheological Fluid on Herringbone-Grooved Hybrid Slot-Entry Bearing

In recent years, extensive use of smart lubricants has been made in order to control the tribological performance of fluid film bearings. The grooved surfaces of the journal bearing greatly influence the performance of bearings. In the present work, various geometric shapes of herringbone grooves (rectangular, triangular, and parabolic) with groove angles (30° and 60°) have been considered to numerically simulate the performance of slot-entry bearings. The work reported in this article deals with the numerical simulation of magnetorheological (MR) fluid–lubricated slot-entry herringbone-grooved hybrid journal bearings. Dave equation, a constitutive relation of the Bingham model, was employed to simulate the flow behavior of MR fluid. Using the finite element method (FEM), the governing Reynolds equation for a hybrid slot-entry bearing model was solved. The result shows that the use of a herringbone-grooved surface and application of MR fluid in a slot-entry bearing offers better stability and higher fluid film stiffness and minimizes frictional torque.

Investigation on influences of herringbone grooves for the aerostatic journal bearings applied to ultra-high-speed spindles

Aerostatic bearings are the core parts of ultra-high-speed spindles with maximum running speed greater than 100,000 r/min. In this paper, the influences of herringbone grooves on the performance of aerostatic journal bearings are studied to design spindles with the features of higher precision and higher speed. Parametric studies and sensitivity analyses are executed in terms of the improved finite element method, which is specially developed to solve the compressible Reynolds equation for herringbone grooved air bearings. The calculated results indicate that herringbone grooves significantly improve the performance of aerostatic journal bearings under the conditions of ultra-high speeds and low supply pressures. Groove parameters are nonlinear dependent, and groove depth and length are the dominant influential factors for the load capacity at speed of 200,000 r/min. Experiments are designed and conducted to verify the improved finite element method, which show that the improved finite element method can be used to analyze the influences of herringbone grooves on aerostatic journal bearings and also manifest that suitable herringbone groove geometrical parameters can obviously decrease spindle radial runouts at ultra-high speeds.