Amit Chauhan

Simulation studies on static thermal behaviour of true elliptical and orthogonally displaced non-circular journal bearing

Purpose The current trend of modern industry is to use machineries which rotate at high speed along with the capability of carrying heavy rotor loads. This paper aims at static thermal analysis of two different profiles of non-circular journal bearings – a true elliptical bearing and orthogonal bearing. Design/methodology/approach The Reynolds equation has been solved through finite difference method to compute the oil film pressure. Parabolic temperature profile approximation technique has been used to solve the energy equation and thus used for computation of various bearing performance characteristics such as thermo-hydrodynamic oil film pressure, temperature, load capacity, Sommerfeld number and power loss characteristics across the bearing. The effect of ellipticity ratio on the bearing performance characteristics has also been obtained for both the elliptical and vertical offset bearing using three different commercially available grades of oil (Hydrol 32, 68 and 100). Findings It has been observed that the thermo-hydrodynamic pressure and temperature rise of the oil film is less in orthogonal bearing as compared to the true elliptical bearing for same operating conditions. The effect of ellipticity ratio of non-circularity on bearing performance parameters have been observed to be less in case of elliptical bearing as compared to orthogonal bearing. It has been concluded that though the rise in oil film temperature is high for true elliptical bearing, but still it should be preferred over orthogonal profile under study, as it has comparably good load-carrying capacity. Originality/value The performance parametric analysis will help the designers to select such kind of non-circular journal bearing for various applications.

Design of AVR and ALFC for single area power system including damping control

This paper presents the combined control for single area power system including automatic voltage control by using automatic voltage regulator (AVR) and automatic frequency control by using automatic load frequency control (ALFC). The paper shows the coupling effects between the two loops, which are studied by extending the linearised ALFC system to incorporate the excitation system. A proportional integral gain controller is included in the AVR loop and conventional integral controller in ALFC loop so that system responses become better in terms of peak deviations and settling time. Damper winding is included in the AVR loop which is present on the rotor of the synchronous generator. Simulation studies reveal that the response of the system becomes better in terms of peak deviations (overshoots and undershoots) and settling time when damper winding is included in the system.

Development of aluminum composites using Red mud as reinforcement- A review

Aluminum composites are widely used materials amongst the different category of metal matrix composite materials available. Metal matrix composites are the materials in which reinforcements are added to improve their properties. The main problem associated with the Metal Matrix Composites is their higher cost of reinforcement. To overcome this obstacle, a need arises to look for low cost reinforcements such as Red mud, Fly ash, and graphite etc. which may result in better properties of the developed composite. Further, the use of red mud as a reinforcement material will consume a waste product which otherwise can cause disposal problem and environmental hazards.

Thermal Studies of Non-Circular Journal Bearing Profiles: Offset-Halves and Elliptical

© 2012 Chauhan and Sehgal, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Thermal Studies of Non-Circular Journal Bearing Profiles: Offset-Halves and Elliptical

Classification of Non-circular Journal Bearings

The chapter presents the reasons towards the development of non-circular journal-bearing profiles and classification of such profiles. The chapter also presents the basic mechanism of operation on which non-circular journal bearing works. In the last section of the chapter, the different regime of lubrication which may occur in various types of bearing has also been presented.

Experimental study for performance evaluation of steadily loaded true elliptical and orthogonally displaced non-circular journal bearing profiles

Purpose The non-circular journal bearings may be used over circular journal bearings because of their superior thermal stability. The paper aims at experimental study of thermal performance of two different true elliptical and orthogonally displaced non-circular journal bearing profiles. Design/methodology/approach The experiments have been conducted on a specially designed test rig which simultaneously evaluates oil film pressure and temperature along the circumference of non-circular journal bearing. The tests are conducted for the designed true elliptical and orthogonally displaced journal bearing at three different rotational speeds of 2,000, 3,000 and 4,000 rpm under the influence of steadily applied load varied from 0.5 to 2.0 kN. The data collected during experimentation have been used to evaluate thermal performance parameters such as maximum pressure, flow rate and effective temperature of the bearings under study. Findings It has been observed experimentally that two lobes of pressure and temperature have been obtained for both the elliptical and orthogonally displaced journal bearing. The negative pressure zone (cavitation area) has been observed to be reduced along the circumference for both the journal bearings which results in less thermal degradation of an oil as compared to circular journal bearing. The oil film pressure and temperature increases with the increase in radial load of both the bearings. The maximum temperature rise of oil film is more in case of elliptical bearing as compared to the orthogonally displaced bearing. Originality/value The experimental data presented in this paper will help the designers to select such kind of non-circular journal bearing for various applications. The designed bearings have resulted in reduced cavitation zone and two positive pressure lobes have been observed which may result in application of such bearings as an alternate for circular journal bearing.

Experimental evaluation of lubricating oil film pressure and temperarture of elliptical non-circular journal bearing profile

The elliptical non-circular journal profile bearings provides more thermal stability than the circular journal bearings. The present study evaluates the thermal performance parameters such as oil film pressure and temperature experimentally along the circumference of an elliptical journal bearing. The tests have been conducted on the specially designed Journal Bearing Test Rig which is capable of measuring both pressure and temperature simultaneously at nine different locations along the central periphery of the elliptical journal bearing. The experimental data is measured at a constant journal speed=2000 rpm and with a variable radial load ranging from 500 N to 2000 N in steps of 500 N is applied on the bearing. The lubricant used for the experimentation is HYDROL 32. The results shows that both oil film pressure and the temperature increases with the increase in applied radial load on the bearing at the constant speed. Experimentally, two positive pressure loops have been found along the elliptical circumference of the bearing which accounts for better thermal stability as it reduces the cavitation zone inside the bearing.

Parametric study of hybrid Savonius-Darrieus turbine

The current work presents the study to predict the pressure and velocity field distributions for a hybrid two-bucket Savonius rotor and three blade egg-beater type Darrieus rotor vertical axis wind turbine using Fluent in ANSYS 15.0. Two cases of overlap conditions for the Savonius rotor i.e. 10.7% and 20.5% have been considered in this study. The Savonius rotor height is assumed approximately equivalent to rotor diameter and NACA 0012 airfoil cross-section has been considered for Darrieus rotor. Contours of relative velocity and static pressure have been obtained from simulation study and it has been observed that the high performance of the hybrid rotor can be attributed to the high relative speed observed in proximity of Darrieus rotor.

Role of Offset Factor in Offset-Halves Bearing

The present paper aims at presenting the influence of offset factor on the thermal characteristics of offset-halves journal bearing profiles. To study the effect of offset factor, an attempt has been made to the solve the Reynolds’s equation and energy equation using finite difference method on the performance characteristics such as oil-film temperatures, thermal pressures, load carrying capacity, power loss, and Sommerfeld’s number of offset-halves journal bearing. To carry the numerical solution of Energy equation, the author has used Parabolic Temperature Profile Approximation technique in order to achieve faster computation. It has been observed that at constant radial clearance, a decrease in oil-film temperature, thermal pressure, load carrying capacity and an increase in Sommerfeld’s number obtained with an increase in offset factor. During the study, it has been concluded that the offset factor significantly affects the performance parameters of the bearing under study and may be kept equal to around 0.4 to get the desired thermal characteristics.