Recent Patents on Mechanical Engineering - Volume 12, Issue 3, 2019

Background: WEDM (Wire Electrical Discharge Machining) is widely used to machine difficult-to-machine materials, such as high-strength and high-brittle materials. The research on tension control device of the wire electrode is mainly to improve the machining precision and surface quality of WEDM. Objective: To meet the growing demand for processing of difficult-to-machine materials, such as highstrength and high-brittle materials, the machining precision and surface quality of WEDM are improved continuously. Methods: This paper reviews various representative patents related to the tension control device of wire electrode in WEDM. Results: Through retracing the characteristics of different types of the tension control device of wire electrode in WEDM, the main problems existing in the current development are concluded and analyzed. The development trend of patents on the tension control device of wire electrode in WEDM is discussed. Conclusion: The optimization and development of the tension control device of wire electrode in WEDM are beneficial to improve the machining precision and surface quality of WEDM. More related patents on the tension control device of wire electrode in WEDM will be invented.

Background: Mechanical parts in processing and manufacturing process will produce burr, scratches and other surface quality problems, which have adverse effects on the precision, use, reprocessing location, operation safety and appearance quality of the parts, so it is necessary to grind the workpiece surface. Objective: Based on the recent development in the field of magnetic grinding and related patent research, it can provide reliable help to solve the problem of finishing the surface of parts with complex shapes and small volumes. Methods: This paper reviewed some patents and research advances related to magnetic abrasive finishing, and the advantages and disadvantages of the magnetic grinding machine in the finishing process were summarized. The outstanding grinding effect of the new vibration assisted magnetic grinder was introduced. Results: The working characteristics of various magnetic grinding machines were summarized, and the development trend of magnetic grinding and finishing was prospected. Conclusion: Magnetic abrasive finishing has good flexibility, strong self-sharpening, wide applicable scope, high processing efficiency, simple processing equipment and low cost. It can control the grinding efficiency and grinding precision. The machining efficiency and quality of magnetic grinding can be improved with the appropriate amplitude of vibration assist, and the surface quality can be improved significantly.

Background: Starting from a wax model of the mold, which is later discarded, investment casting is used to make almost finished metal cast parts. The term "investment casting" is derived from the use of a ceramic liquid mixture (slurry), in which the model is repeatedly immersed (invested) to form, layer by layer, the shell which has to be filled with molten metal. The liquid of the slurry tends to evaporate so that the viscosity of the former increases and a correction is needed. Objective: The study aimed to investigate the simplest way to measure slurry viscosity and automatically correct it. Methods: Numerical and experimental tests have been implemented to correctly assess the proposed method. An integrated system for the automatic correction of slurry viscosity is realised which comprises: a reservoir of slurry including means for mixing it; a transducer which continuously measures the slurry viscosity; a pump that gradually feeds the diluent into the slurry to keep its viscosity constant; and a device, governed by the continuous viscosity measurement, that operates the pump. Results: It has been proved that the developed system is able to integrate the slurry viscosity continuous measurement with gradual addition of diluent into the slurry, so as to have a fully automated operation that can make corrections, whenever necessary, on the basis of the transducer output. Conclusion: The developed system works properly by keeping the slurry viscosity within a fixed range. A patent has been recently deposited to protect the integrated system for the automatic correction of slurry viscosity.

Background: The unique structural characteristics of the metal foams, such as low density, large surface area, ability to increase turbulence, and increased heat transfer efficiency, are the advantages associated with thermal applications such as electronics cooling, refrigeration air conditioning, etc. The porous metal foam structures are extensively used to enhance heat transfer. Objective: This paper discusses the numerical simulations of a vertical channel filled with metal foam and wire mesh. The fluid flow and heat transfer phenomena of a wire mesh are compared with two different types of metal foams. Metal foams are made of aluminium and copper while the wire mesh is made of brass. The porosity of the metallic porous structures varies from 0.85 to 0.95. Methods: A Darcy extended Forchheirmer model is considered for solving fluid flow through the porous media while the heat transfer through the porous media is predicted using local thermal non-equilibrium model. Results: Initially, the results obtained using the proposed numerical procedures are compared with experimental results available in the literature. The numerical simulations suggest that the pressure drop increases as the velocity of the fluid increases and decreases as the porosity increases. The heat transfer coefficient and Nusselt number are determined for both the metal foams and the wire mesh. Conclusion: The Nusselt number obtained for wire mesh shows almost 90% of the copper metal foam in the same porosity range. The numerical results suggest that the brass wire mesh porous medium can also be used for enhancement of heat transfer. In this article, patents have been discussed.

Background: The application of centrifugal pumps is found in domestic and petrochemical industries. Industrial centrifugal pumps are designed and tested using water as working fluid before supplied to industries, as water is commonly available. However, centrifugal pumps are used in industries for various applications, which involve the handling of fluids other than water- like saline-water, crude oil, gasoline, etc. Consequently, hydraulic performance of the pump differs from the designed and tested values and pump performance becomes unpredictable. Cavitation characteristics of the pump handling different fluids other than water are also changed and many a time, cavitation starts prematurely. As a result, the operating cost of pump is increased. Objective: A CFD based computational analysis of a single-stage, single-entry industrial centrifugal pump having double-volute casing is carried out to compare the performance and cavitation characteristics for various working fluids, namely water, saline water with varying salinity, gasolene and crude oil. Methods: Multiple Reference Frame method (MRF) available in Reynolds-Averaged Navier-Stokes (RANS) equations based CFD solver Ansys-CFX is used in the present study. CFD simulation is carried out for five flow rates with Standard k- turbulence model. Rayleigh-Plesset equation describing the growth of a single vapor bubble in a liquid is used for predicting the cavitation flow behaviour. Results: Minimum static pressure is computed at the suction side of saline water as compared to the other working fluids studied here. Hydraulic efficiency of crude oil is found to be the lowest as compared to other fluids. Supercavitation (excessive formation of vapor bubbles and sudden drop in head up to 3%) starts early for saline water with 40g/kg salinity. Conclusion: The results show little variation in pump efficiency when water and saline water are used as working fluids. However, cavitation characteristics differ considerably with the working fluids. Recent patents filed/published in this area revealed that efforts are needed to develop effective cavitationresistant centrifugal impellers and pumps.

Background: It is established that the vibration response of submerged structures is quite different than that calculated in vacuum. Therefore, the study of vibration characteristics of submerged plate structures is important for safety and its designing purpose. Objective: To investigate the fundamental frequency of partially cracked Functionally Graded (FG) submerged plate based on analytical approach. Methods: The governing differential equation of the cracked-submerged plate is derived based on Kirchhoff’s thin classical plate theory in conjunction with the potential flow theory. The line spring model is used to incorporate the effect of crack in the form of additional bending whereas the effect of fluid medium is incorporated in form fluids forces associated with inertial effects of its surrounding fluids. The Bernoulli’s equation and velocity potential function are used to define the fluid forces acting on plate surface. Results: An approximate solution for governing equation of coupled fluid-plate system is obtained by using the Galerkin’s method. For validation of the present results, they are compared with the existing results of the previous published work, which are in good agreements. New results for natural frequencies as affected by gradient index, crack length, level of submergence and immersed depth of plate are presented for Simply Supported (SSSS) boundary condition. Conclusion: It has been concluded that the presence of crack and fluidic medium significantly affect the natural frequencies of the plate. It is observed that the increase in the length of crack and level of submergence decreases the fundamental frequency. In this paper, few patents have been discussed.

Background: Angular contact ball bearing is an important component of many high-speed rotating mechanical systems. Oil-air lubrication makes it possible for angular contact ball bearing to operate at high speed. So the lubrication state of angular contact ball bearing directly affects the performance of the mechanical systems. However, as bearing rotation speed increases, the temperature rise is still the dominant limiting factor for improving the performance and service life of angular contact ball bearings. Therefore, it is very necessary to predict the temperature rise of angular contact ball bearings lubricated with oil-air. Objective: The purpose of this study is to provide an overview of temperature calculation of bearing from many studies and patents, and propose a new prediction method for temperature rise of angular contact ball bearing. Methods: Based on the artificial neural network and genetic algorithm, a new prediction methodology for bearings temperature rise was proposed which capitalizes on the notion that the temperature rise of oil-air lubricated angular contact ball bearing is generally coupling. The influence factors of temperature rise in high-speed angular contact ball bearings were analyzed through grey relational analysis, and the key influence factors are determined. Combined with Genetic Algorithm (GA), the Artificial Neural Network (ANN) model based on these key influence factors was built up, two groups of experimental data were used to train and validate the ANN model. Results: Compared with the ANN model, the ANN-GA model has shorter training time, higher accuracy and better stability, the output of ANN-GA model shows a good agreement with the experimental data, above 92% of bearing temperature rise under varying conditions can be predicted using the ANNGA model. Conclusion: A new method was proposed to predict the temperature rise of oil-air lubricated angular contact ball bearings based on the artificial neural network and genetic algorithm. The results show that the prediction model has good accuracy, stability and robustness.

Background: The impulse for the propulsion of a rocket engine is obtained from the combustion of propellant mixture inside the combustion chamber and as the plume exhausts through a convergent- divergent nozzle. At stoichiometric ratio, the temperature inside the combustion chamber can be as high as 3500K. Thus, effective cooling of the thrust chamber becomes an essential criterion while designing a rocket engine. Objective: A new cooling method of thrust chambers was introduced by Chiaverni, which is termed as Vortex Combustion Cold-Wall Chamber (VCCW). The patent works on cyclone separators and confined vortex flow mechanism for providing high propellant mixing with improved degree of turbulence inside the combustion chamber, providing the required notion for studies on VCCW. The flow inside a VCCW has a complex structure characterised by axial pressure losses, swirl velocities, centrifugal force, flow reversal and strong turbulence. In order to study the flow phenomenon, both the experimental and numerical investigations are carried out. Methods: In this study, non-reactive flow analysis was conducted with real propellants like gaseous oxygen and hydrogen. The test was conducted to analyse the influence of mixture ratio and injection pressure of the propellants on the chamber pressure in a vortex combustion chamber. A vortex combustor was designed in which the oxidiser injected tangentially at the aft end near the nozzle spiraled up to the top plate and formed an inner core inside the chamber. The fuel was injected radially from injectors provided near the top plate and the propellants were mixed in the inner core. This resulted in enhanced mixing and increased residence time for the fuel. More information on the flow behaviour has been obtained by numerical analysis in Fluent. The test also investigated the sensitivity of the tangential injection pressure on the chamber pressure development. Results: All the test cases showed an increase in chamber pressure with the mixture ratio and injection pressure of the propellants. The maximum chamber pressure was found to be 3.8 bar at PC1 and 2.7 bar at PC2 when oxidiser to fuel ratio was 6.87. There was a reduction in chamber pressure of 1.1 bar and 0.7 bar at PC1 and PC2, respectively, in both the cases when hydrogen was injected. A small variation in the pressure of the propellant injected tangentially made a pronounced effect on the chamber pressure and hence vortex combustion chamber was found to be very sensitive to the tangential injection pressure. Conclusion: VCCW mechanism has been to be found to be very effective for keeping the chamber surface within the permissible limit and also reducing the payload of the space vehicle.