SENSITIVITY OF STRENGTH, RIGID AND DYNAMIC CHARACTERISTICS OF THE CONSOLE ROTOR TO VARIATION OF DESIGN PARAMETERS

The analysis sensitivity of strength, rigid and dynamic characteristics of the console rotor to variation of design parameters in paper describes The speed of rotation of the shaft, the material of the impeller vary. The dependences of radial and axial displacements on the angular velocities of rotation and the modulus of elasticity of the impeller material are established. For objects of the type of rotary systems with a cantilever arrangement of the impeller, not one, but a set of criteria has been introduced into consideration, which should be taken into account in the research of this type of objects. The tendencies of change of the first and second critical rotational speeds from the modulus of elasticity, rotor rotational frequencies and density of the impeller material are also determined. On this basis, recommendations have been developed for determining the design parameters of the rotor part of the air blower with a cantilevered impeller. Keywords: air blower; critical rotation speed; natural vibration frequency; rotary system; stress-strain state

The theoretical model for determinig critical rotation speed flexible coupling type SEGE

It this article was studied a flexible coupling with a rubber elastic element. In exploitation period under one direction load, half of all cylinders are working. All of cylinders are made along with a carrying ring. The elastic elements are subjected to compression. On the non-loaded cylinders, a centrifugal force acts to cause their radial displacement. By the slow rubber relaxation of not loaded cylinders, in the case of reverse and impact load it is danger of can be pinched between the metal claws of semi couplings. Radial displacement and critical rotation speeds were determined, for non-loaded cylinders, in the time which is derived pinching the rubber elastic element.

Spin rates and spin evolution of O components in WR+O binaries

Context. Despite 50 yr of extensive binary research, we must conclude that the Roche lobe overflow/mass transfer process that governs close binary evolution is still poorly understood. Aims. It is the scope of the present paper to lift the edge of the veil by studying the spin-up and spin-down processes of the O-type components of WR+O binaries. Methods. We critically analyzed the available observational data of rotation speeds of the O-type components in WR+O binaries. By combining a binary evolutionary code and a formalism that describes the effects of tides in massive stars with an envelope in radiative equilibrium, we computed the corresponding rotational velocities during the Roche lobe overflow of the progenitor binaries. Results. In all the WR+O binaries studied, we find that the O-type stars were affected by accretion of matter during Roche lobe overflow (RLOF) of the progenitor. This means that common envelope evolution, which excludes any accretion onto the secondary O star, has not played an important role in explaining WR+O binaries. Moreover, although it is very likely that the O-type star progenitors were spun up by mass transfer, many ended the RLOF (and mass transfer) phase with a rotational velocity that is significantly smaller than the critical rotation speed. This may indicate that during the mass transfer phase there is a spin-down process that is of the same order, although significantly less, than that of the spin-up process. We propose a Spruit–Tayler type dynamo spin-down suggested in the past to explain the rotation speeds of the mass gainers in long-period Algols.

A Novel Safety Brake System Based on Magneto-Rheological Fluids

This paper presents a novel Magentorheological (MR) brake with permanent magnets. The proposed MR brake can generate a braking torque at a critical rotation speed without an external power source, sensors, or controllers, making it simple and cost-effective device. The brake system consists of a rotary disk, permanent magnets, springs and MR fluid. Permanent magnets are attached to the rotary disk via springs, and they move outward through grooves with two different gap distances along the radial direction of the stator due to centrifugal force. Thus, the position of the magnets is dependent on the spin speed, and it can determine the magnetic fields applied to MR fluids. Proper design of the stator geometry gives the system unique torque characteristics. To show the performance of an MR brake system, the electromagnetic characteristics of the system are analyzed, and the torques generated by the brake are calculated using the result of the electromagnetic analysis. After the simulation study, a prototype brake system is constructed and its performance is experimentally evaluated. The results demonstrate the feasibility of the proposed MR brake as a speed regulator in rotating systems.

Stationary Rotation of the Partially Liquid-Filled Unbalanced Rotor under External Friction Force Action

Rotor rotation with liquid layer on the chamber wall under viscoelastic action of the shaft within a planar model is examined in the article. The solution to the problem of determining the deflection of a rotating shaft with liquid filled chamber is given, which is important when designing an automatic balancing device. The issue of the cooperative motion of a solid body and liquid is considered in mathematical research. The set task is performed by applying D'Alembert's principle. The modeling results indicate that an increase in liquid’s mass in a rotor decreases its critical rotation speed; at the same time, the external friction accelerates the system’s self-centering. The developed mathematical models enable us to select the design parameters of a liquid-type autobalancer which operates within the set range of rotor’s angular velocity.

Critical Rotation Speed Calculation and Application Development of Multi-Stage Centrifugal Pumps for Mining

Multi-stage centrifugal pumps for mining are widely used in mining and smelting industry. The operational environment in coal mine sewage is very harsh, so pump shaft and bearing failure happens frequently. In order to avoid disaster damage caused by failure of the pump shaft due to resonance, it is quite necessary and urgent to calculate critical rotation speed of the pump shaft. A calculation program of critical rotation speed for multi-stage centrifugal pumps for mining was developed using the secondary development tool of Object ARX, to give the computational method of the pump shaft load and static deflection and to achieve calculation of the critical speed, and which avoided the disadvantage of the traditional method. The practical application indicates that the program of critical rotation speed is convenient, intuitive and calculation accurate. It not only improves the work efficiency, but also reduces the labor intensity, so the program will have a good application prospect.

Strength Calculation Software Development and Finite Element Analysis of Pump Shaft

With the wide applications to the fields of petrochemical, military, metallurgy and mining, pumps have to subject to more and more serious working conditions. In order to avoid disaster damage caused by failure of the shaft, it is quite necessary to calculate and examine the shaft strength. A kind of two-dimensional software was developed using the secondary development tool of Object ARX, to achieve the shaft strength calculation accurately and conveniently, and which avoided the disadvantage of the traditional method. The calculation methods of shaft critical rotation speed and the static bending displacement were proposed. Theoretical analysis and calculations on the strength, rigidity, vibration and other aspects of pump shaft were conducted under shut-off condition and best efficiency point using ANSYS APDL software of static, dynamic and transient modal analysis method. The quality of pump shaft was analyzed through the comparisons of numerical results, and further more the accuracy of two-dimensional development software was validated. The practical application indicates that the shaft parts strength calculation software can improve the quality and efficiency, reduce wastage during the pump shaft design. These research achievements will also have a great application prospect.

Results from a recent stellar rotation census of B stars

In an analysis of the rotational properties of more than 1100 B stars (~660 cluster and ~500 field B stars), we determine the projected rotational velocity (V sin i), effective temperature, gravity, mass, and critical rotation speed for each star. The new data provide us a solid observational base to explore many hot topics in this area: Why do field B stars rotate slower than cluster B stars? How fast do B stars rotate when they are just born? How fast can B stars rotate before they become Be stars? How does the rotation rate of B stars change with time? Does the evolutionary change in rotation velocity lead to the Be phenomenon? Here we report the results of our efforts in searching for answers to these questions based on the latest B star census.