Rehan Zahid, Masjuki Hj. Hassan, Abdullah Alabdulkarem, Mahendra Varman, Md. Abul Kalam, Riaz Ahmad Mufti, Nurin Wahidah Mohd Zulkifli, Mubashir Gulzar, Muhammad Usman Bhutta, Mian Ashfaq Ali, Usman Abdullah and Robiah H. Yunus
There is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance…
Abstract
Purpose
There is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance parameters. Because of their favorable tribological properties, chemically modified vegetable oils such as palm trimethylolpropane ester (TMP) are one of the potential candidates for the said role. To prove the suitability of TMP for applications involving boundary-lubrication regime such as cam/tappet interface of direct acting valve train system, a logical step forward is to investigate their compatibility with conventional lubricant additives.
Design/methodology/approach
In this study, extreme pressure and tribological characteristics of TMP, formulated with glycerol mono-oleate (GMO), molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), has been investigated using four-ball wear tester and valve train test rig. For comparison, additive-free and formulated versions of polyalphaolefin (PAO) were used as reference. Moreover, various surface characterization techniques were deployed to investigate mechanisms responsible for a particular tribological behavior.
Findings
In additive-free form, TMP demonstrated better extreme pressure characteristics compared to PAO and lubricant additives which are actually optimized for conventional base-oils such as PAO, are also proved to be compatible with TMP to some extent, especially ZDDP. During cylinder head tests, additive-free TMP proved to be more effective compared to PAO in reducing friction of cam/tappet interface, but opposite behavior was seen when formulated lubricants were used. Therefore, there is a need to synthesize specialized friction modifiers, anti-wear and extreme pressure additives for TMP before using it as engine lubricant base-oil.
Originality/value
In this study, additive-free and formulated versions of bio-lubricant are tested for cam/tappet interface of direct acting valve train system of commercial passenger car diesel engine for the very test time. Another important aspect of this research was comparison of important tribological performance parameters (friction torque, wear, rotational speed of tappet) of TMP-based lubricants with conventional lubricant base oil, that is, PAO and its formulated version.
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Keywords
Rahat Gulzar, Sumeer Gul, Manoj Kumar Verma, Mushtaq Ahmad Darzi, Farzana Gulzar and Sheikh Shueb
Sharing and obtaining information over social media has enabled people to express their opinions regarding any event. Since the tweets regarding the Russia-Ukraine war were…
Abstract
Purpose
Sharing and obtaining information over social media has enabled people to express their opinions regarding any event. Since the tweets regarding the Russia-Ukraine war were extensively publicized on social media, this study aims to analyse the temporal sentiments people express through tweets related to the war.
Design/methodology/approach
Relevant hashtag related to the Russia-Ukraine war was identified, and tweets were downloaded using Twitter API, which were later migrated to Orange Data mining software. Pre-processing techniques like transformation, tokenization, and filtering were applied to the extracted tweets. VADER (Valence Aware Dictionary for Sentiment Reasoning) sentiment analysis module of Orange software was used to categorize tweets into positive, negative and neutral ones based on the tweet polarity. For ascertaining the key and co-occurring terms and phrases in tweets and also to visualize the keyword clusters, VOSviewer, a data visualization software, was made use of.
Findings
An increase in the number of tweets is witnessed in the initial days, while a decline is observed over time. Most tweets are negative in nature, followed by positive and neutral ones. It is also ascertained that tweets from verified accounts are more impactful than unverified ones. russiaukrainewar, ukraine, russia, false, war, nato, zelensky and stoprussia are the dominant co-occurring keywords. Ukraine, Russia and Putin are the top hashtags for sentiment representation. India, the USA and the UK contribute the highest tweets.
Originality/value
The study tries to explore the public sentiments expressed over Twitter related to Russia-Ukraine war.
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Keywords
Saman Rashidi, Javad Abolfazli Esfahani, Mohammad Sadegh Valipour, Masoud Bovand and Ioan Pop
The analysis of the flow field and heat transfer around a tube row or tube banks wrapped with porous layer have many related engineering applications. Examples include the reactor…
Abstract
Purpose
The analysis of the flow field and heat transfer around a tube row or tube banks wrapped with porous layer have many related engineering applications. Examples include the reactor safety analysis, combustion, compact heat exchangers, solar power collectors, high-performance insulation for buildings and many another applications. The purpose of this paper is to perform a numerical study on flows passing through two circular cylinders in side-by-side arrangement wrapped with a porous layer under the influence of a magnetic field. The authors focus the attention to the effects of magnetic field, Darcy number and pitch ratio on the mechanism of convection heat transfer and flow structures.
Design/methodology/approach
The Darcy-Brinkman-Forchheimer model for simulating the flow in porous medium along with the Maxwell equations for providing the coupling between the flow field and the magnetic field have been used. Equations with the relevant boundary conditions are numerically solved using a finite volume approach. In this study, Stuart and Darcy numbers are varied within the range of 0 < N < 3 and 1e-6 < Da < 1e-2, respectively, and Reynolds and Prandtl numbers are equal to Re=100 and Pr=0.71, respectively.
Findings
The results show that the drag coefficient decreases for N < 0.6 and increases for N > 0.6. Also, the effect of magnetic field is negligible in the gap between two cylinders because the magnetic field for two cylinders counteracts each other in these regions.
Originality/value
To the authors knowledge, in the open literature, flow passing over two circular cylinders in side-by-side arrangement wrapped with a porous layer has been rarely investigated especially under the influence of a magnetic field.