Adaptive centrifuge vibration damping module for biofuel production

The present study considers the problem of obtaining promising renewable energy sources, in particular biofuel. Biomass is the main fuel for green energy accounting for two-thirds of renewable energy. Industry further development depends on improvement of used equipment and technologies. Biofuel usually contains significant amounts of harmful impurities that need to be isolated. The paper deals with the problems of centrifuge operation for the biofuel production. In particular, the most significant operation problem is the residual rotor imbalance which causes torsional oscillations that negatively affect the biodiesel production process and centrifuge reliability. A new technology for damping torsional vibrations of centrifugal device rotating system is described as well as adaptive module device for its implementation is developed. The module main feature is vibrations adaptive level of the rotor elements interaction with external environment. Computer simulation of the module operation process in ANSYS Fluent program was carried out. Data on the module efficiency depending on various factors in the dynamics of its work are obtained. The most effective device configuration is determined.

Active vibration control for GyroWheel based on sliding mode observer and adaptive feedforward compensator

This article proposes an active vibration control method for the GyroWheel to ensure the attitude stability precision of the spacecraft. The method includes sliding mode disturbance observer and adaptive feedforward compensator. First, considering the disturbance torque caused by rotor imbalance, the dynamic equation adopting complex coefficients is derived with synchronous disturbances. To reduce the influence of model parameter perturbation, a finite time sliding mode observer is designed to estimate the rotor imbalance owing to its robustness. An integrator for the switching term is introduced in the sliding manifold, which attenuates the chattering phenomenon. Then, the observed unbalanced torque is utilized to generate the reference compensation tilting angle, which is fedforward to the command value to offset the synchronous frequency current. A variable step size seeking algorithm is adopted to tune the feedforward compensator gain adaptively. Finally, both numerical simulations and experiments have verified the effectiveness of the active vibration control scheme, achieving clean vibration torque.

Mathematical modeling of imbalance and dynamics of a disc-shaped rotor

It is shown, that the existing methods and means for modeling the dynamics of a rotor on a balancing machine are unsuitable for the implementation of dynamic balancing of disk-shaped rotors, which ensures their highest quality balance. New models of imbalance and dynamics are proposed, which provide reliable and accurate identification of the characteristics of the imbalance of such rotors using a developed and practically tested technique. These models serve as a theoretical basis for the creation of a new computer technology for dynamic balancing of disk-shaped rotors. Keywords: disc-shaped rotor, imbalance, dynamics, modeling, dynamic balancing. [email protected]

Analytical study of auto-balancing within the framework of the flat model of a rotor and an auto-balancer with a single cargo

This paper reports the analytically established conditions for the onset of auto-balancing for the case of a flat rotor model on isotropic elastic-viscous supports and an auto-balancer with a single load. The rotor is statically unbalanced, the rotation axis is vertical. The auto-balancer has a single cargo – a pendulum, a ball, or a roller. The balancing capacity of the cargo is equal to the rotor imbalance. The physical-mathematical model of the system is described. The differential equations of motion are recorded in dimensionless form relative to the coordinate system that rotates synchronously with the rotor. The so-called main movement has been found; in it, the cargo synchronously rotates with the rotor and balances it. The differential equations of motion are linearized in the neighborhood of the main movement. A characteristic equation has been constructed. It helped investigate the stability of the main movement (an auto-balancing mode) for the cases of the absence and presence of resistance forces in the system. It was established that in the absence of resistance forces in the system: – the rotor has three characteristic rotational speeds, and the first always coincides with the resonance frequency; – auto-balancing occurs when the rotor rotates at speeds between the first and second ones, and above the third characteristic speed; – the value of the second and third characteristic speeds is significantly influenced by the ratio of weight to the mass of the system; – the second and third characteristic speeds monotonously increase with an increase in the ratio of cargo weight to the mass of the system. Resistance forces significantly affect both the values of the second and third characteristic speeds and the conditions of their existence. Small resistance forces do not change the quality behavior of the system. With high resistance forces, the number of characteristic speeds decreases to one. The paper reports the results applicable to an auto-balancer with many cargoes when it balances the imbalance that equals the balancing capacity of the auto-balancer

Eccentricity in Induction Machines—A Useful Tool for Assessing Its Level

In the condition monitoring of induction machines operating in various industry sectors, the assessment of eccentricity is as important as the assessment of the condition of windings, bearings, mechanical vibrations or noise. The reasons for the eccentricity can be various; for example, rotor imbalance, damage or wear of the bearings, improper alignment of the rotor and the load machine and finally, assembly errors after overhaul. Disregard of this phenomenon during routine tests may result in the development of vibrations transmitted to the stator windings, faster wear of the bearings and even, in extreme cases, rubbing of the rotor against the stator surface and damage to the windings and local overheating of the machine core. On the basis of years of experience in the diagnosis of large induction machines operating in various industries, the article deals with the problem of developing reliable indicators for assessing the levels of commonly accepted types of eccentricity. Starting from field calculations and analyzing various cases of eccentricity, the methodology for determining the indicators for evaluation from the stator current spectrum is shown. The changes in the values of these indices for various cases of simultaneous occurrence of static and dynamic eccentricity are shown. The calculation results were verified in the laboratory. Also shown are three interesting cases from diagnostic practice in the evaluation of high-power machines in the industry. It has been shown that the proposed indicators are useful and enable an accurate diagnosis of levels of eccentricity.

Rotor imbalance detection and quantification in wind turbines via vibration analysis

Rotor imbalance is a common fault in wind turbines, which may enhance radial loads that induce faults on the main bearing and gearbox. It usually results from the asymmetry of the air dynamics caused by blade crack, icing, etc. A simple and effective method on rotor imbalance detection and quantification is presented using the vibration signal collected from the accelerometer monitoring the wind turbine drive train. A vibration model describing the rotor imbalance under blade crack is proposed. The complex morlet wavelet transform is applied to the detection of the rotational frequency of rotor hub which represents the rotor hub. A health indicator that can quantify the degree of the rotor imbalance is designed. The proposed methods have successfully detected and quantified the rotor imbalance caused by blade crack in an on-site wind turbine.

Selecting the criterion for diagnosing imbalance of electric mining shovel rotors

The limit state criteria for a mining shovel mechanical equipment that contains the faults of a rotor imbalance-type are studied in the article. On the bases of a statistical analysis of mining shovel failures, it is demonstrated that rotor imbalance is a prevailing reason for their accident-caused failures. On the bases of three-year monitoring of supporting elements vibrating activity the vibratory norms for electrical mining shovel rotors that take into account their service condition are substantiated.