Rib Groove Research Articles

A new spinning-extrusion forming technology for the inner-ribbed component

To solve the problem that the rib filling height is low in the traditional spinning forming (TSF) of ribbed component, a new spinning-extrusion forming technology (SEF) was proposed. A convenient device was built to conduct the SEF experiment, whose results show that the new SEF can greatly increase the rib filling height by 53% compared with the TSF. Moreover, the improvement mechanism and prediction model of rib filling height in the SEF were investigated. It is found that the rib filling in SEF is mainly dependent on two deformation stages: tension-shear deformation, which makes the material accumulate and bulge above the rib groove; compression-shear deformation, which makes the accumulated material fill into the rib groove. The final rib filling height is linear dependent on the material bulge amount in the tension-shear deformation stage. And, the improvement of rib filling by SEF lies in it can enhance the duration and deformation amount of tension-shear deformation stage, thus improve the material bulge amount in contrast to the TSF. On these bases, taking the material bulge region in SEF as object, slab method was used to analyze its deformation mechanics and establish the differential mechanical equilibrium equations; Thamasett method was adapted to calculate the spinning force; synthetically, the material bulge amount was theoretically calculated. Then, combing the linear relation between the material bulge amount and rib filling height, the model for prediction of rib filling height in the SEF was developed. The predicted rib filling heights under various processing parameters indicate that the rib filling height can be improved by increasing the extrusion force, thickness reduction rate, feed ratio and roller attack angle in the SEF.

Effects of Circumferential and Longitudinal Ribs and Grooves in Swirl Cooling on Characteristics of Pressure Drop and Heat Transfer

The impact of roughened swirl cooling chamber walls on heat transfer and fluid flow characteristics is explored in this study. This study compares ten roughened wall shapes against a smooth wall in a swirl cooling chamber. The roughened wall shapes are circumferential and longitudinal with and without cuts. The circumferential cases consist of four cases. The first case, designated as a circumferential groove (CG), contains eight grooves along the surface. The second case, designated as a circumferential groove cut (CGC), has eight cut grooves along the surface. The third case is called a circumferential rib (CR), and the fourth case is called a circumferential rib cut (CRC), and it has eight ribs without and with surface cuts. While the longitudinal cases consist of six cases. The first four cases, which have six longitudinal grooves and ribs with and without cuts, are longitudinal groove (LG), longitudinal groove cut (LGC), longitudinal rib (LR), and longitudinal rib cut (LRGC). The final two longitudinal cases, longitudinal rib groove (LRG) and Longitudinal rib and groove cut (LRGC), have hybrid grooves and ribs without and with surface cuts. Bulk temperature averaged circumferential heat transfer ratio, friction factor, global thermal performance factor, and turbulent kinetic energy are among the variables that were examined. Simulations are performed using CFD codes. These examined parameters are contrasted with results from previous studies. The findings demonstrate that heat transfer is boosted by roughly 2.7, 2.6, and 2.5 times higher in cases with LG, CG, and CGC, respectively, than in the smooth case. The use of rough walls in the swirl cooling chamber boosts the global thermal performance factor; the LG case has a 2.8 times higher global thermal performance factor than a smooth case. In comparison with alternative internal cooling technologies, a grooved wall, as shown in the LG case, has the best heat transfer characteristics.

Study on the ultrasonic-assisted spinning of thin-walled cylindrical parts with longitudinal and transverse ribs

Current studies have shown that the application of composite energy fields in the plastic forming process can help reduce the forming load and promote material flow. In this paper, a new method of ultrasonic-assisted spinning integral forming for thin-walled cylindrical parts with outer ribs was proposed, which could not only improve the manufacturing efficiency of ribbed cylindrical parts, but also further improve the forming height of outer ribs. A simulation model of ultrasonic-assisted spinning for thin-walled cylindrical parts with longitudinal and transverse outer ribs was established, the influence of ultrasonic amplitude on the forming accuracy of longitudinal and transverse outer ribs was obtained, and the mechanism of ultrasonic vibration improving the forming accuracy of ribs was revealed. On this basis, ultrasonic-assisted spinning equipment was built to verify the feasibility of this process. The results showed that with the increase of ultrasonic amplitude, the forming height of longitudinal and transverse outer ribs gradually increases, and the effect of raising the forming height of transverse ribs is higher than that of longitudinal ribs. In addition, as the ultrasonic amplitude increases, the uniformity of the forming morphology of the outer rib is not obviously improved. The spinning of the outer rib is mainly realized by the material in the form of integral filling into the groove. The ultrasonic vibration improves the material flow properties, and promotes the filling of the material into the rib groove, thereby increasing the spinning forming height of the outer ribs. The forming height of the outer rib was measured with or without ultrasonic vibration. When the rolling reduction is 1 mm, the average forming height of the outer ribs is increased by 50% compared with that without ultrasound, which provides a new research idea for the integral forming of the spinning of thin-walled cylindrical parts with longitudinal and transverse ribs.

Application of shaped tube as preform to eliminate the forming defects of ribbed tube in multi-pass drawing

Thin-walled ribbed tube with small-diameter is a newly designed structure, which is used in nuclear fuel cladding. Due to the high precision requirements of nuclear industry applications, the integral forming and precision forming of ribbed tube are the focus of research. However, the forming defects — rib grooves often fail to achieve the precision forming of ribbed tube. Therefore, the two-pass drawing process is designed to realize the integral forming of ribbed tube and the forming mechanism of ribbed tube is analyzed. Further, the effect of round tube as billet on the forming accuracy of ribbed tube is studied. The results show that the rib groove defects are caused by local large deformation and excessive metal flow, which can not be completely eliminated only by changing the billet size of round tube. Based on this, three kinds of shaped tubes as preforms instead of round billet are proposed for eliminating the rib groove defects to realize the precision forming of ribbed tube. The effects of different preform schemes on the forming accuracy, drawing force and stress distribution of ribbed tube are compared and discussed. By selecting the optimal preform scheme and applying it to multi-pass drawing, the completely defect-free ribbed tube is obtained. At the same time, after adopting the appropriate billet size, the rib filling fullness of the tube is further improved and closer to the target size. Moreover, the microstructure of ribbed tube after multi-pass drawing are observed. The martensite and deformation twins appeared due to work hardening and the grain size refinement degree of different positions are different due to different deformation degree.

Influence of grooved rib tip structure on tip loss and heat transfer in a gas turbine blade

This study focuses on the effects of three groove tip structures (full rib groove tip, partial rib tip on the suction side, and partial rib tip on the pressure side) on tip leakage flow, aerodynamic characteristics of a cascade, and heat transfer in a gas turbine blade. The groove’s width B = 1.6 mm, while the tip clearance is τ = 1.2 mm. Results of the flow parameters, fluid flow, and heat transfer in the recessed channel are discussed. The results show that all ribbed tips obtain more uniform outlet flow angle distribution and higher aerodynamic performance than the plane tips. The total aerodynamic pressure loss of the ribbed tips on the pressure side is the same as that of complete ribbed tips. The evolution mechanisms are different, although both can improve the turbine efficiency. Although the partial rib tip on the pressure side weakens the mixing of the channel vortex and leakage vortex near the trailing edge and has the best control effect on the leakage vortex, the lack of the suction side rib will make it easier for the low-energy fluid to flow into the gap from the front of the suction side, which is not conducive to reducing the leakage flow inside the gap; the full rib tip not only minimizes the tip relative leakage flow and leakage loss but also increases the channel vortex loss. With the complex vortex system in the groove and the rib blocking effect at the leakage outlet, the suction-side rib tip becomes the tip structure with the best leakage flow control effect under the same clearance, but the leakage vortex loss is the highest.

Research on the influence of ultrasonic on the inner rib’s surface morphology of ribbed cylindrical parts in flow spinning process

• Ultrasonic-assisted flow spinning platform is established. • Ultrasonic reduces the deformation and friction resistance. • Application of ultrasonic benefits the material flow in spinning. • Rib tip surface morphology is more uniform with ultrasonic. • Quality of the inner longitudinal ribs is enhanced with ultrasonic. Thin-walled shell with inner ribs is the main load bearing structure for aerospace products, which decides the products overall performance. Flow spinning process is an effective method to realize the integrated manufacturing of thin-walled shells with inner ribs. However, this process still has defects of insufficient filling at the rib groove and fracture at the rib root. A novel process is proposed to fabricate the thin-walled shell with inner ribs by introducing ultrasonic energy into flow spinning process based on the softening effect and friction-reducing effect of the ultrasonic energy. This paper focuses on the forming quality of the inner longitudinal ribs. The longitudinal ribs are designed along the axial direction of the cylindrical parts. The rheological characteristics of material forming with ultrasonic is studied and the local cumulative deformation law of the inner rib material at the rib groove is revealed. The ultrasonic-assisted flow spinning platform was established and ultrasonic energy was introduced in the radial direction of the initial cylindrical parts. The experiment results with different ultrasonic amplitudes showed that the rib tip’s surface morphology and rib height were improved with ultrasonic. The finite element models were established to analyze the deformation characteristics of the inner ribs. The constitutive equation was established to reflect the material flowing property with ultrasonic. The simulation results showed that the material flowed into the groove more at the screw-in end and flowed out more at the screw-out end with ultrasonic. This flow state reduced the material accumulation phenomenon at the screw-out end. The tip’s surface morphology of inner longitudinal ribs were more uniform with ultrasonic. The displacement vectors of the nodes at rib groove were also extracted to explore the flow difference. Additionally, the rib height increased with ultrasonic. In conclusion, it is productive to apply ultrasonic into the ribbed cylindrical parts flow spinning process to enhance the forming quality of the inner longitudinal ribs.

Deformation mechanism of ZK61 magnesium alloy cylindrical parts with longitudinal inner ribs during hot backward flow forming

• Isothermal uniaxial compression was proposed as the physical simulation test of hot backward flow forming (HBFF) of thin-walled cylindrical parts with longitudinal inner ribs (CPLIRs). • 3D hot processing maps (HPMs) during HBFF of the Mg alloy were constructed as a function of temperature, strain rate and strain. • Finite Element simulation and 3D HPMs were integrated to analyze the formability of hot spin-forming. • Typical defects during HBFF of Mg alloy CPLIRs were identified, and forming quality can be qualified by the proposed evaluation indexes. Thin-walled cylindrical parts with longitudinal inner ribs (CPLIRs) made of magnesium alloys are one of the most promising lightweight components. Flow forming is an effective technology to realize the integrated manufacturing of thin-walled CPLIRs. However, due to the complicated material flow and narrow temperature window, defects like insufficient filling at the rib groove and concavity of the back of rib occur easily during hot backward flow forming (HBFF) of ZK61 alloy thin-walled CPLIRs. The isothermal uniaxial compression test was proposed as the physical simulation test of the HBFF of thin-walled CPLIRs, and a novel method for analyzing the formability of hot spin-forming was proposed on the basis of the combination of 3D hot processing maps (HPMs) and finite element (FE) simulation. The process experiment and FE simulation integrated with 3D HPMs were conducted to investigate the deformation characteristic and material flow, and formation mechanism of defects was revealed. Further, the influence of process parameters on the power dissipation efficiency of spun workpiece was discussed. The results show that safe deformation of the alloy is concentrated at a narrow region with high temperature and low strain rate; the large tangential flow at the cylindrical wall and radial flow at the inner rib contributed to the filling of rib groove; unsaturated inner rib and concavity of the outer wall at the back of rib are typical defects; the ZK61 alloy CPLIRs exhibits good formability under reasonable process parameters, which is beneficial for obtaining qualified forming quality and uniform recrystallized microstructure.

Experimental and CFD Analysis of Two-Phase Forced Convection Flow in Channels of Various Rib Shapes

This paper investigates numerically and experimentally heat transfer forced convective two-phase flow (i.e. air and water) over a rectangular ribbed channel with a vertical orientation. Three distinct rib–groove shapes have been examined. Ribs - groove shapes are; Triangle, Trapezoid, and Semi-Trapezoid ribs-groove. The present study has been performed with continuous heat flux through range of water and air superficial inlet velocity values between 0.105 – 0.316m/s, and 0.263 – 1.320 m/s, respectively. Continuity, momentum and energy calculations have been formulated using the Finite Volume Approach (FVM). Results indicate that the triangle rib-groove has the high heat transfer coefficient and lower temperature difference than other cases against a different number of Reynolds. The experimental data has been compared to numerical results for ribs –grooved channel with deviation of about 1.0% - 7.5%. The channel fitted with triangle ribs shows the highest heat transfer, which is about 59% higher than the smooth channel; 56% for trapezoidal rib, and 44% for channel fitted by semi-trapezoidal rib. Finally, the triangle rib-groove gives a better heat transfer improvement value in comparison with trapezoidal and semi trapezoidal rib-groove channel at constant pumping power.

Numerical Simulation of a New Flow Field Design with Rib Grooves for a Proton Exchange Membrane Fuel Cell with a Serpentine Flow Field

The cathode flow field design of a proton exchange membrane (PEM) fuel cell is essential to fuel cell performance, which directly affects the uniformity of reactant distribution and the ability to remove water. In this paper, the single serpentine flow field design on the cathode side is optimized to reach a high performance by controlling the rib groove rate (the ratio of the number of grooved ribs to the number of total ribs). The rib groove starts from the inlet side and then evenly distributes over the ribs. Four rib groove rates are selected in this study, namely, 0, 1/3, 2/3, and 1. A three-dimensional PEM fuel cell model is used to analyze the output performance of the fuel cell. The results indicate that the rib groove design has a significant effect on the distribution of oxygen at the cathode side, the density of the membrane current, the concentration of water vapor under the rib, and the fuel cell output performance. The output performance of the fuel cell improves with the increased rib groove rate. However, when the rib groove rate is greater than 2/3, its impact on the overall performance of the fuel cell begins to slow down. The PEM fuel cells exhibit the best output performance when the rib groove rate is 1.

Research on the thermal stress characteristics of self-cooled brake discs of belt conveyors

Equipped with rib groove structure, the self-cooled brakes disc enjoys an excellent heat dispersion and are applied in the belt conveyors with good effect. According to Hooke’s Law, the steady-state thermo-mechanical coupling expression of the brake disc under two-dimensional conditions is deduced, and the solving method of the displacement differential equation is given. Based on the ABAQUS, thermo-mechanical coupling finite element model for self-cooled disc brakes is established and for the structure and load characteristics of the brake discs, three different azimuth paths are defined and the transient thermal stress variations under different paths are obtained. Through the thermal cycling tests of self-cooling brake disc samples at 300 °C, 400 °C, and 500 °C under the condition of heat and water-cooling for 800 times respectively and analyzing the metallographic structure with electron probe microscope, the results have showed that a large amount of graphitized tissue can be precipitated under the high circulating temperature and heating cracks can induced.

Heat transfer enhancement of turbulent nanofluid flow over various types of internally corrugated channels

A numerical study is carried out to investigate the effects of different geometrical parameters and various nanofluids on the thermal performance of rib–grooved channels under uniform heat flux. The continuity, momentum and energy equations are solved by using the finite volume method (FVM). Three different rib–groove shapes are studied (rectangular, semi-circular and trapezoidal). Four different types of nanoparticles, Al2O3, CuO, SiO2 and ZnO with different volume fractions in the range of 1% to 4% and different nanoparticle diameters in the range of 20nm to 60nm, are dispersed in the base fluids such as water, glycerin and ethylene glycol. The Reynolds number varies from 5000 to 25,000. To optimize the shape of rib–groove channels different rib–groove heights from 0.1Dh (4mm) to 0.2Dh (8mm) and rib–groove pitch from 5e (20mm) to 7e (56mm) are examined. Simulation results reveal that the semi-circular rib–groove with height of 0.2Dh (8mm) and pitch equals to 6e (48mm) has the highest Nusselt number. The nanofluid containing SiO2 has the highest Nusselt number compared with other types. The Nusselt number rises as volume fraction increases, and it declines as the nanoparticle diameter increases. The glycerin–SiO2 nanofluid has the best heat transfer compared to other base fluids. It is also observed that in the case of using nanofluid by changing parameters such as nanoparticle diameter, volume fraction and base fluids the skin friction factor has no significant changes.

Enhancement heat transfer characteristics in the channel with Trapezoidal rib–groove using nanofluids

Numerical study of heat transfer due to turbulent flow of nanofluids through rib–groove channel have been investigated. The continuity, momentum and energy equations are solved by the finite volume method (FVM). Four different rib–groove shapes have been examined. Four different types of nanoparticles, Al2O3, CuO, SiO2, and ZnO with different volumes fractions in the range of 1–4% and different nanoparticle diameter in the range of 25–70nm, have been also studied. The computations are performed under constant temperature over a range of Reynolds number (Re) 10,000–40,000. Results indicate that the Trapezoidal with increasing height in the flow direction rib–trapezoidal groove has the best heat transfer rate and high Nusselt number. It is also found that the SiO2 – nanofluid has the highest value of Nusselt number in comparison with the other type of nanofluids. The Nusselt number increases as the volume fraction increases and it decreases as the nanoparticle diameter increases. The present study shows that these Trapezoidal rib–groove using nanofluids have the potential to dramatically increase heat transfer characteristics and thus can be good candidates for the development of efficient heat exchanger device.

Characteristics Analysis of Tire Hydroplaning Flow and Tread Design Influence Study

Tire hydroplaning has become a direct inducement of wet-weather road accidents. The model of hydroplaning of the deformed rib tire with load was built with the help of CFD (Computational Fluid Dynamics) technology. The three-dimensional SST coupled with the Volume of Fluid (VOF) model was applied to numerically simulate the air-water two phase flow with free surface in tire hydroplaning. Based on the model of hydroplaning, the design of tire pattern rib and lateral grooves on tire hydroplaning were analyzed. Analysis shows that tire has a high pressure induced by water impact in the front of footprint; water flow is inclined to tire sidewall. For the rib grooves, the depth of rib groove has a largest effect, followed by the rib groove width, finally the distance between the two rib grooves; for the lateral grooves, the structure factors sequence is :lateral grooves number> width> angle.

Heat transfer and fluid flow analysis of artificially roughened ducts having rib and groove roughness

Artificially roughness is one of the well known methods of enhancing heat transfer from the heat transfer surface in the form of repeated ribs, grooves or combination of ribs and groove (compound turbulators). The artificial roughness produced on the heat transferring surface is used in cooling of gas turbine blades, nuclear reactor, solar air heating systems etc. Solar air heaters have wide applications in low to moderate temperature range, namely, drying of foods, agricultural crops, seasoning of wood and space heating etc. Solar air heaters have low value of convective heat transfer coefficient between the working fluid (air) and the heat transferring surface, due to the formation of thin laminar viscous sub-layer on its surface. The heat transfer from the surface can be increased by breaking this laminar viscous sub layer. Hence, in the present work compound turbulators in the form of integral wedge shaped ribs with grooves are used on the heat transfer surface, to study its effect on the heat transfer coefficient (Nusselt number) and friction factor in the range of Reynolds number 3,000–18,000. The roughness produced on the absorber plate forms the wetted side of upper broad wall of the rectangular duct of solar air heater. The relative groove position (g/p) was varied from 0.4 to 0.8 and the wedge angle (Φ) was varied from 10° to 25°, relative roughness pitch (p/e) and relative roughness height (e/D) was maintained as 8.0 and 0.033 respectively. The aspect ratio of the rectangular duct was maintained as 8. The Nusselt number and friction factor of the artificially roughened ducts were determined experimentally and the corresponding values were compared with that of smooth surface duct. It is observed that wedge-groove roughened surface shows more enhancement in heat transfer compared to only rib roughened surface arrangement. The investigation revealed that Nusselt number increases 1.5–3 times, while the friction factor increases two to three folds that of the smooth surface duct in the range of operating parameters. It is also observed that in rib–groove roughness arrangement with relative groove position of 0.65 shows the maximum enhancement in the heat transfer compared to the other rib-groove roughness arrangements. Statistical correlations for the Nusselt number and friction factor have been developed by the regression method in terms of the operating and roughness parameters. A program was also developed in MATLAB for the calculation of thermal efficiency and thermal effectiveness. It was observed that the thermal efficiency is more for wedge angle of 15° and relative groove position of 0.65 and its value ranges from 42 to 73 %. The uncertainties in the measurements due to various instruments for the Reynolds number, Nusselt number, and friction factor have been estimated as ±3.8, ±4.54 and ±7.6 % respectively in the range of investigation made.

Experimental investigation of the effect of the design parameters of pressboard in mineral oil on creepage discharge propagation

One of the vital causes of the failure of oil transformers is considered as the creepage discharge propagation on pressboard. The authors performed an experimental investigation under an AC step test voltage to analyse the effects of the structure, distance and gluing direction of pressboard on creepage propagation. Flat, ribbed and grooved test specimens were prepared. Further, breakdown experiments were conducted for two gluing directions, parallel and vertical with respect to the electric field. For parallel gluing, the average breakdown voltage (V BD) of the ribbed and grooved types was 1.2–1.33 times that of the flat type. For vertical gluing, the V BD of the flat type was 1.28–1.66 times that of the same type with parallel gluing, whereas the values for the ribbed and grooved types were 1.02–1.11 times the corresponding values for parallel gluing. The rib height and groove depth do not seem to contribute greatly to the breakdown strength because most of the flashover propagation appeared not on the pressboard's surface but at the glued interface. The results of this preliminary investigation may be useful for improving the dielectric creepage strength of solid insulation systems using pressboard as radial spacers, and high-voltage winding lead support parts.

Thermal and hydraulic characteristics of turbulent nanofluids flow in a rib–groove channel

Thermal and hydraulic characteristics of turbulent nanofluids flow in a rib–groove channel are numerically investigated. The continuity, momentum and energy equations were solved by means of a finite volume method (FVM). The top and bottom walls of the channel are heated at a constant temperature. Nine different rib–groove shapes are considered in this study, which are three different rib shapes with three different groove shapes including rectangular, triangular and trapezoidal and they are interchanged with each other. Four different types of nanoparticles Al2O3, CuO, SiO2, and ZnO with different volume fractions in the range of 1% to 4% and different nanoparticle diameters in the range of 25nm to 80nm, are dispersed in different base fluids (water, glycerin, engine oil) are used. In this study, several parameters such as different Reynolds numbers in the range of 5000<Re<20000, and different rib–groove aspect ratios in the range of 0.5≤AR≤4 are also examined to identify their effects on the heat transfer and fluid flow characteristics. The results indicate that the rectangular rib–triangular groove has the highest Nusselt number among other rib–groove shapes. The SiO2 nanofluid has the highest Nusselt number compared with other nanofluid types. The Nusselt number increased as the nanoparticle volume fraction, Reynolds number and aspect ratio increased; however, it decreased as the nanoparticle diameter increased. It is found that the glycerin–SiO2 shows the best heat transfer enhancement compared with other tested base fluids.

Finite Element Analysis of Lossless Propagation in Surface Plasmon Polariton Waveguides With Nanoscale Spot-Sizes

We present simulation results on the propagation characteristics of active plasmonic waveguides at 1.55 mum wavelength based on semiconductors as the active gain media. Three waveguide structures were investigated: metal rib, metal-semiconductor-metal (MSM), and triangular metal groove. In all three structures, we observed strong plasmon mode confinement with nanoscale spot-sizes and corresponding simulated gain values compatible with existing semiconductor technology. We show the effect of systematic modification of waveguide geometry on the required gain for achieving lossless propagation in all the three plasmonic waveguide structures. We demonstrate that lossless propagation with subwavelength spot sizes well below the diffraction limit of light can be obtained by controlling the geometrical parameters of the proposed waveguides.

Second law optimization of a solar air heater having chamfered rib–groove roughness on absorber plate

Artificially roughened solar air heaters perform better than the plane ones under the same operating conditions. However, artificial roughness leads to even more fluid pressure thereby increasing the pumping power. The entropy generation in the duct of solar air heater having repeated transverse chamfered rib–groove roughness on one broad wall is studied numerically. Roughness parameters, viz., relative roughness pitch P/ e, relative roughness height e/ D h relative groove position g/ P, chamfer angle φ and flow Reynolds number Re have a combined effect on the heat transfer as well as fluid friction. The entropy generation is minimized and reasonably optimized designs of roughness are found.