Satish Sharma, Satish Jain, J. Sharana Basavaraja and Neeraj Sharma
Hole‐entry hybrid journal bearings are widely used in many applications owing to their favourable characteristics. Ever increasing technological developments demand much improved…
Abstract
Purpose
Hole‐entry hybrid journal bearings are widely used in many applications owing to their favourable characteristics. Ever increasing technological developments demand much improved performance from these class of bearings operating under the most stringent, exact and precise conditions. Therefore, it becomes imperative that the hole‐entry journal bearings be designed on the basis of more accurately predicted bearing characteristics data. The purpose of this paper is to describe a theoretical study to demonstrate the combined influence of the effect of pocket size at the outlet of supply holes and the journal misalignment on the performance of an orifice compensated hole‐entry hybrid journal bearing system.
Design/methodology/approach
Finite element method is used to solve the Reynolds equation governing the flow of an incompressible lubricant in the clearance space between the journal and bearing together with equation of flow through an orifice. The journal misalignment has been accounted for by defining a pair of misalignment parameters sigma and delta. The effect of pocket size at the outlet of supply holes has been accounted by defining a non‐dimensional parameter which is function of diameter of pocket and journal diameter.
Findings
The results presented in this paper indicate that the effect of journal misalignment is, in general, to cause a reduction in bearing dynamic characteristics parameters whereas the effect of pocket size is to slightly compensate this loss. Performance of a two lobe four recessed journal bearing, a proper selection of bearing offset factor along with type of restrictor (capillary or orifice) is essential.
Originality/value
This paper presents valuable data relating to hole‐entry hybrid journal bearings useful for bearing designers.
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Satish Jain, Satish Sharma, J. Sharana Basavaraja and Prashant Kushare
In recent years, researchers have focused a great deal of attention on multirecess hybrid journal bearing systems. The non‐circular journal bearings are widely used in industry on…
Abstract
Purpose
In recent years, researchers have focused a great deal of attention on multirecess hybrid journal bearing systems. The non‐circular journal bearings are widely used in industry on account of their better stability, simplicity, efficiency and low cost. The purpose of this paper is to present a theoretical investigation into the performance of a two‐lobe multirecess hybrid journal bearing system.
Design/methodology/approach
The Reynold's equation governing the lubricant flow in the clearance space between the journal and bearing together with restrictor flow equations has been solved using finite element method. The bearing static and dynamic performance characteristics have been presented for the various values of the offset factors (0.75, 1, 1.25 and 1.50) for the hybrid mode of operation of the journal bearing system compensated by capillary and orifice restrictors for the commonly used bearing operating and geometric parameters. The offset of the journal has been accounted for by defining a non‐dimensional factor called offset factor delta.
Findings
The numerically simulated results indicate that a two‐lobe four recessed hybrid journal bearing provides a better performance than the corresponding similar circular recessed journal bearing system. The study further reveals that in order to get an improved performance of a two‐lobe four recessed journal bearing, a proper selection of bearing offset factors along with type of restrictor (capillary or orifice) is essential.
Originality/value
The results presented in this paper are useful for bearing designers.
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Arvind Sahay and Varuna M. Joshi
The pandemic induced lockdown lead to supply and manufacturing disruptions that were swiftly dealt with by the Indian Pharma Industry through successful industry-government…
Abstract
The pandemic induced lockdown lead to supply and manufacturing disruptions that were swiftly dealt with by the Indian Pharma Industry through successful industry-government collaboration. By May 2020 production was back to normal and exports were higher than the same period in May 2019. The case deals with the processes that enabled this to happen, the policy responses and the changes that happened in the period from March 2020 to August 2020.
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![Indian Institute of Management Ahmedabad](/insight/static/img/indian-institute-of-management-ahmedabad-logo.png)
Keywords
Zichao Liu, Wei Pan, Changhou Lu and Yongtao Zhang
This paper aims to establish an accurate mathematical model of a piezoelectric membrane restrictor that can be applied to control the shaft’s centerline orbit.
Abstract
Purpose
This paper aims to establish an accurate mathematical model of a piezoelectric membrane restrictor that can be applied to control the shaft’s centerline orbit.
Design/methodology/approach
The methodology uses three coupled equations to establish a mathematical model of the piezoelectric membrane restrictor – Reynolds equation, the membrane deformation equation and the flow rate equation. A data identification method is used to propose the flow rate formulas for the piezoelectric membrane restrictor.
Findings
It has been found that the structural parameters, the membrane center deformation and the inlet and outlet pressures of the piezoelectric membrane restrictor have an effect on the static performance of the restrictor. The identified flow rate result of the piezoelectric membrane restrictor is consistent with the models.
Originality/value
The paper provides an accurate mathematical model of the piezoelectric membrane restrictor which can also be applied to other membrane restrictors.
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Satish C. Sharma, Vikas M. Phalle and S.C. Jain
Noncircular journal bearings are used in industry because of their simplicity, efficiency and low cost. During the life time of a machine, these are required to be operated over a…
Abstract
Purpose
Noncircular journal bearings are used in industry because of their simplicity, efficiency and low cost. During the life time of a machine, these are required to be operated over a number of years and are submitted to several stops and starts. As a result, the bush becomes progressively worn out and the bearing performance changes. The purpose of this paper is to study theoretically the influence of wear on the performance of a non‐circular 2‐lobe four‐pocket multirecess hybrid journal bearing system.
Design/methodology/approach
The Reynolds equation governing the flow of lubricant in the clearance space of a non‐circular 2‐lobe multirecess worn hybrid journal bearing system has been solved using FEM along with appropriate boundary conditions. The defects caused by wear are centered on the load line and range from 10 per cent to 50 per cent of the bearing radial clearance.
Findings
The numerically simulated results based on a Newtonian lubricant and the steady state flow field system have been presented in terms of maximum fluid film pressure, minimum fluid film thickness, lubricant flow rate, direct fluid film stiffness and damping coefficients and stability threshold speed margin. The paper demonstrates that, for the bearing configurations studied, the bearing behavior is clearly affected by wear. The numerically simulated results indicate that for an offset factor of δ=1.2, the value of h¯min reduces by 21.21 per cent at δ¯w=0.5.
Originality/value
The presented results have valuable data in case of 2‐lobe four pocket hybrid journal bearing compensated with constant flow valve restrictor. The paper outcomes are sure to be of interest for researchers and useful for bearing designers.
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Samirasadat Samadi and Mohammad Saeed Taslimi
This study aims to review the features and challenges of the flood relief chain, identifies administrative measures during and after the flood occurrence and prioritizes them…
Abstract
Purpose
This study aims to review the features and challenges of the flood relief chain, identifies administrative measures during and after the flood occurrence and prioritizes them using two machine learning (ML) and analytic hierarchy process (AHP) methods. This paper aims to provide a prioritization program based on flood conditions that optimize flood management and improves society’s resilience against flood occurrence.
Design/methodology/approach
The collected database in this paper has been trained by using ML algorithms, including support vector machine (SVM), Naive Bayes (NB) and k-nearest neighbors (kNN), to create a prioritization program. Furthermore, the administrative measures in two phases of during and after the flood are prioritized by using the AHP method and questionnaires completed by experts and relief workers in flood management.
Findings
Among the ML algorithms, the SVM method was selected with 91.37% accuracy. The prioritization program provided by the model, which distinguishes it from other existing models, considers five conditions of the flood occurrence to prioritize actions (season, population affected, area affected, damage to houses and human lives lost). Therefore, the model presents a specific plan for each flood with different occurrence conditions.
Research limitations/implications
The main limitation is the lack of a comprehensive data set to determine the effect of all flood conditions on the prioritization program and the relief activities that have been done in previous flood disasters.
Originality/value
The originality of this paper is the use of ML methods to prioritize administrative measures during and after the flood and presents a prioritization program based on each flood’s conditions. Therefore, through this program, the authority and society can control the adverse impacts of flood more effectively and help to reduce human and financial losses as much as possible.
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Abdallah Chanane and Hamza Houassine
Although, numerous optimization algorithms have been devoted to construct an electrical ladder network model (ELNM), they suffer from some frail points such as insufficient…
Abstract
Purpose
Although, numerous optimization algorithms have been devoted to construct an electrical ladder network model (ELNM), they suffer from some frail points such as insufficient accuracy as well as the majority of them are unconstrained, which result in optimal solutions that violate certain security operational constraints. For this purpose, this paper aims to propose a flexible-constraint coyote optimization algorithm; the novelty lies in these points: penalty function is introduced in the objective function to discard any unfeasible solution, an advanced constraint handling technique and empirical relationship between the physical estimated parameters and their natural frequencies.
Design/methodology/approach
Frequency response analysis (FRA) is very significant for transformer winding diagnosis. Interpreting results of a transformer winding FRA is quite challenging. This paper proposes a new methodology to synthesize a nearly unique ELNM physically and electrically coupled for power transformer winding, basing on K-means and metaheuristic algorithm. To this end, the K-means method is used to cluster the setting of control variables, including the self-mutual inductances/capacitances, and the resistances parameters. Afterward, metaheuristic algorithm is applied to determine the cluster centers with high precision and efficiency.
Findings
FRA is performed on a power transformer winding model. Basing on the proposed methodology, the prior knowledge in selecting the initial guess and search space is avoided and the global solution is ensured. The performance of the abovementioned methodology is compared using evaluation expressions to verify its feasibility and accuracy.
Originality/value
The proposed method could be generalized for diagnosis of faults in power transformer winding.
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Nathi Ram and Satish C. Sharma
The present work aimed to study analytically the influence of wear on the performance of a capillary-compensated hole-entry hybrid misaligned journal bearing system operating in a…
Abstract
Purpose
The present work aimed to study analytically the influence of wear on the performance of a capillary-compensated hole-entry hybrid misaligned journal bearing system operating in a turbulent regime. The numerically simulated results are presented for the chosen values of restrictor design parameter, Reynolds numbers, wear depth and misalignment parameters.
Design/methodology/approach
The wear caused on the bearing surface due to start/stop operations is modeled using the Dufrane’s abrasive wear model. The modified Reynolds equation based on Constantinescu’s lubrication theory is solved using finite element method together with capillary restrictor flow equation.
Findings
It is found that the value of minimum fluid-film thickness increases significantly for a constant value of restrictor design parameter when unworn aligned bearing operates in turbulent regime vis-à-vis laminar regime. Further, it has also been observed that when a worn bearing operates in laminar/turbulent regimes, the reduction in the value of minimum fluid-film thickness is more due to journal misalignment as compared to the aligned bearing operates in laminar regime.
Originality/value
The present work is original concerning the performance of worn hole-entry hybrid misaligned journal bearing system operating in turbulent regime. The results are expected to be quite useful for the bearing designer.
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Rajesh Kumar, Satish Kumar and Deepa Mudgal
The purpose of this paper is to investigate the erosion performance of high velocity oxy fuel- (HVOF) sprayed Al2O3–Cr2O3 composite coatings under silt slurry conditions.
Abstract
Purpose
The purpose of this paper is to investigate the erosion performance of high velocity oxy fuel- (HVOF) sprayed Al2O3–Cr2O3 composite coatings under silt slurry conditions.
Design/methodology/approach
The requisite HVOF composite coatings has been deposited on the stainless steel substrate (SS-304). The slurry erosion pot tester of make Ducom was used for conducting the silt slurry erosion tests on the required substrates. The comprehensive experiments were conducted at different particle size of silt in the range 212–250, 150–212, 53–106 µm, and the concentration of the silt ranged from 10%–40% by weight. The rotational speed of the pot tester has been varied between 500 and 1,500 revolutions per minute, and the test duration has been kept to 4 h.
Findings
The erosion wear resistance of the uncoated SS-304 has been greatly enhanced by the application of HVOF-sprayed Al2O3–Cr2O3 composite coatings. The addition of CeO2 has a significant impact in reducing the erosive wear caused by silt slurry. The composite coating powder composition of 65%Cr2O3 + 34.5%Al2O3 + 0.5%CeO2 has shown the highest erosion resistance.
Practical implications
The developed coatings have the potential to be used for hydro turbines as subjected to silt slurry conditions.
Originality/value
The erosion wear experiments are conducted comprehensively for coated and uncoated samples and the scanning electron micrographs supports the findings.