Low Load Conditions Research Articles

Novel Synthetic ‘Triangle Ester’ Lubricants: Useful Correlations for Wetting and Tribological Phenomena Over Common Engineering Substrates

The surface free energy (SFE) of engineering substrates and the surface tension (ST) of lubricants are known to influence wetting behavior at the interface of the mating mechanical components. The influence of cyclic moieties and heteroatoms in modulating wetting behavior and consequent tribological properties like friction and wear is less well elucidated. Continuing our exploration of “triangle esters” distinguished by the introduction of three-membered heteroatom rings in otherwise commonly used lubricant structures, we demonstrate that friction and wear properties for each ester over a set four different metallic engineering substrates—aluminum, brass, phosphor bronze, and stainless steel—under low load conditions can be effectively correlated with surface properties for the coefficient of friction, and with both surface properties and substrate hardness for wear parameters. The experimentally determined regression equations are used to predict these properties for a fifth substrate, gun metal. The difference in polarity fraction between the substrate and the lubricant is found to have a surprisingly significant influence on wear properties.

Experimental Study on the Performance-Influencing Factors of an Aviation Heavy-Oil Two-Stroke Direct-Injection Ignition Engine

To study the influence of control parameters under cold-start and low-load conditions on the performance of a heavy-oil, two-stroke, direct-injection, ignition engine for use in aviation, the operation of a two-stroke, direct-injection engine was studied in a bench test. The results were as follows: ① When the ambient temperature is 15 °C, the battery voltage is 12.4 V, and the peak speed of the starting motor is 1200 r/min. As the concentration factor increases, the cold-start speed increases, and the fuel consumption increases. The influence on the cold start is reduced after reaching a certain concentration. The cold-start time decreases with the increasing magnetization pulse width. The cold-start time is the shortest at an oil–gas interval of 6 ms. ② Under small-load conditions of 3000 r/min and 14% to 16% throttle, a higher ignition energy increases the engine power. Pollutant emissions are the lowest when the fuel injection is 7.5 mg and the excess air coefficient is approximately 1.1.

Wear prognosis in rolling friction of AISI SS304 steel through worn out particle analysis

An experimental investigation was undertaken to study the wear mechanism in AISI SS304 steel sample that undergoes rolling friction. Steel samples were subjected to a wide range of speed and load in order to undertake the process of wear. Worn out particles liberated from the mating surface of the samples were collected in a glass substrate and was observed in an optical microscope to know the morphology of the friction induced wear particles. The physical properties of the particles material were measured to establish a correlation between them. It is found that the worn out particles are of regular in shape at lower loading conditions but changes to irregular shape with increase in loading patterns which depicts a change from mild to severe wear mechanism. The experimental results revealed the reasons of failure initiated at constant speed and with increasing load.

Passive visual stimulation induces fatigue under conditions of high arousal elicited by auditory tasks.

Theories of cognitive fatigue disagree on whether performance decrement is caused by motivational or functional alterations. Here, drawing inspiration from the habituation and visual adaptation literature, we tested the assumption that keeping neural networks active for an extensive period of time entails consequences at the subjective and objective level-the defining characteristics of fatigue-when confounds such as motivation, boredom, and level of skill are controlled. In Experiment 1, we revealed that passive visual stimulation affected the performance of a subsequent task that was carried out in the same portion of visual space. While under conditions of low cognitive load and arousal, participants improved their performance in the stimulated quadrant; the reverse was observed under high arousal conditions. This latter performance decrement correlated also with the reported subjective level of fatigue and occurred while neural responses to the saturating stimulus remained constant, as assessed through steady-state EEG. In subsequent experiments, we replicated and further characterized this performance deterioration effect, revealing its specificity to the stimulated eye and stimulus orientation. Across the three experiments, the decrease in performance was correlated with pupil-linked arousal, suggesting its mediating effect in this phenomenon. In sum, we show that repeated stimulation of neural networks under high-arousal conditions leads to their altered functional performance, a mechanism which may play a role in the development of global cognitive fatigue. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Cascode GaN FET 기반 EV용 V2x DAB 컨버터의 경부하 효율 분석

In this paper, the light-load efficiency of cascode gallium nitride (GaN) FET-based V2x dual active bridge (DAB) converters for electric vehicles(EVs) is analyzed. High efficiency and high power density are required when an on-board charger(OBC) is used in EVs. To this and a zero voltage switching (ZVS) topology, such as that observed in DAB converters, is widely applied. As for the converter requiring current enough to achieve the ZVS condition of the efficiency characteristics vary depending on whether ZVS operated or not. Therefore, in this study, the efficiency in the hard switching section is improved by applying a cascode GaN FET to a DAB converter. The ZVS characteristic is analyzed by considering the parasitic output capacitance of the switching device. Compared to the Si device, the cascode GaN FET with low parasitic output capacitance realizes ZVS under a lower load condition. To verify this, a load test is performed by applying it to a 3-kW DAB converter. The experimental results confirm that ZVS is achieved when the cascode GaN FET is applied. Moreover, a shorter dead time can be applied owing to excellent dv/dt and di/dt characteristics, which improves the overall efficiency. In conclusion, the use of GaN FET in DAB converters can improve efficiency at light loads.

Experimental study of droplet combustion and diesel engine characteristics for Azolla biodiesel

ABSTRACT This study pertains to studying the feasibility of the third-generation biodiesel obtained from one of the algae species known as Azolla microphylla by exploring their fundamental droplet combustion behavior and diesel engine characteristics. Firstly, the droplet evolution and burn rate are investigated for diesel, Azolla100, and Azolla50 (50% biodiesel +50% diesel) based on the experimental study of suspended droplet combustion. The diesel droplet showed steady combustion with linear regression for the decrease in droplet surface with time throughout its lifetime, while the Azolla100 and Azolla50 droplets showed a linear trend initially, and after a certain point, they resulted in a non-linear trend as a result of disruptive burning. The evaporation and burn rate was found to be higher for Azolla100 and Azolla50 than diesel during the steady burning period and thereafter it decreased with increasing Azolla concentration. The time evolution of droplet combustion images indicated that with increasing biodiesel concentration, the combustion duration was decreased due to secondary droplet ejections and microexplosion, and the residue burning duration was increased. The microexplosion increased the rate of combustion, however, droplet ejection resulted in incomplete combustion. Secondly, the engine experiments were performed for Azolla50 at different fuel injection pressures. The results showed that in-cylinder pressure and Brake thermal efficiency (BTE) for Azolla50 at 300 bar injection pressure were lower than diesel due to limitations with the physical properties of biodiesel. In order to improve the engine characteristics of Azolla50, this study increased the fuel injection pressure to 900 bar. As a result, the BTE for Azolla50 at 900 bar injection pressure is improved by 9.2% and 10.2% at low and full load conditions, respectively, compared to Azolla50 at 300 bar injection pressure. Overall, the spray-driven combustion for Azolla50 is limited by the physical properties of the biodiesel, which affects the mixture formation. On the other hand, the microexplosion and droplet ejection observed with the biodiesel during the combustion study would favor the combustion by improving the atomization and mixing process.

Experimental study on combustion characteristics of a fischer‐tropsch diesel/methanol reactivity controlled compression ignition mode engine

AbstractF‐T diesel is an alternative fuel with a high cetane number (CN) for internal combustion engines. Methanol has a low CN and contains oxygen. F‐T diesel and methanol are potential fuels for the reactivity controlled compression ignition (RCCI) engines. In a single‐cylinder 186FA compression‐ignition engine with a combination of methanol inlet pipe injection and F‐T diesel in‐cylinder injection, the combustion characteristics of the F‐T diesel/methanol RCCI mode engine are investigated. The results show that as methanol premixed ratio (MPR) increases, the ignition delay (ID) is prolonged at low load conditions, the maximum in‐cylinder pressure (Pmax) and indicated thermal efficiency (ITE) a decreased. When the MPR increases from 0% to 60%, the ID is extended by 1.7°CA, the Pmax decreases by 8.1%, and the ITE decreases by 1.1%. At high load conditions, MPR rises from 0% to 60%, combustion duration (CD) is shortened by 2.4°CA, Pmax is increased by 8.3%, and the ITE is increased by 1.7%. The fuel injection advance angle (IAA) of F‐T diesel significantly influences the combustion process of the RCCI engine. As the IAA increases, the ID is shortened at high loads, and the Pmax and the ITE are increased. When the MPR is 60% and the IAA is 14°CA, the ITE of the engine is increased by 2.04%, and the equivalent indicated fuel consumption rate(be) is reduced by 5.68% compared with the engine fueled with F‐T diesel under high loads.

Pilot study on renovation, modernization and uprating of agricultural dependent power plant

Hydro energy is one of the most valuable, rich, pliable inexhaustible energy resources in the world. Furtherance to the India’s commitment and pledge at Conference of the Parties (COP) 26 at Glasgow in 2021 calls to cut emissions to net zero by 2070, reduce the carbon emission by one billion tonnes by 2030 and improve the share of renewables in the energy mix to 50 % among others. Scientists and researchers needs to play a major role in achieving net zero emission to reduce the climate change impacts. In India, the share of hydro power is 34.1 % among the overall renewable energy of 150 GW. Hence, hydro power is an important area for Renovation, Modernization and Uprating (RMU) of the existing hydro capacities and it leads to limiting considerable carbon emission to an extent. This research paper focuses on storage reservoir where irrigation to hydro power water transfer is important. A balance of power generation and irrigation is at the highest priority attaining optimum social benefits. The reaction turbines are operated at high flow and low/medium head conditions for agricultural dependant power plant with consideration to Irrigation, drinking, flora and fauna. The restrictions imposed on the reaction turbines while operation under low load and low flow conditions leads to cavitation. The operation conditions under low flow and low load of reaction turbines may lead to noise, vibration and directed to major catastrophic failure of turbines. The likely outcome of same leads to considerable loss of energy generation. In addition to the above, a typical hydro power plant consumes 0.3 to 0.5 % of maximum power capacity as an internal load for lighting and other auxiliary systems. This paper emphasizes in utilizing the unused energy potential during the low and high water releases from irrigation dependent hydro power plant on renovation, modernization and uprating (RMU) of existing hydropower station. An irrigation dependent hydropower plant Dhom (2X1 MW), MAHAGENCO, Satara, Maharastra has been considered for study in order to use the available energy potential optimally. The improvement of capacity factor from 0.315 to 0.46 and additional power generation of 300 kW creates the opportunity to apply RMU in existing hydropower plant successfully.

It's the little “stings”: Racial microaggressions against Asian American customers in retail and their effects

Racial discrimination frequently occurs in the retail context. Yet, research has neglected to investigate the experiences and effects of racial microaggressions against Asian Americans in retail. To close this gap, the researchers opted for a mixed-method design combining one-on-one semi-structured interviews and online experiments. The findings in Study 1 show that Asian American customers face more racial microaggressions that are low in racial loading than are high. In Studies 2 and 3, the results indicate that participants in the high racial loading conditions feel higher degrees of anger and shame than those in the low racial loading conditions. Moreover, participants in the high racial loading conditions show lower repatronage intentions and higher word-of-mouth intentions than those in the low racial loading conditions. Also, anger has a stronger association with behavioral intentions than shame. This research adopts the attributional ambiguity theory to understand the psychological processes and effects of racial loading in microaggressions.

Exploring the potential of third-generation microalgae bio-alcohol and biodiesel in arresting particulate smoke emissions and greenhouse gases using CART.

Due to the rise in vehicular emissions, the rapid deterioration of the atmospheric air quality is a cause for concern in a global scale. In this context, the objective of this study is to explore the effect of post-injection parameters on a continuous active regeneration trap (CART) to mitigate harmful greenhouse gases (GHG) and particulate smoke emissions (PSE) using diesel fuel reformulated by long-chain microalgae bio-alcohol and low-density microalgae biodiesel. Furthermore, the efficiency of the CART unit is analyzed based on its ability to mitigate the harmful emissions without sacrificing the engine performance characteristics. From the study, it was observed that the maximum de-smoke efficiency of 67.85% is observed at a post-injection timing (PIT) of 20°CA aTDC at a post-injection mass (PIM) of 4mg for low load condition while operating on microalgae biodiesel. While operating on microalgae bio-alcohol, the maximum de-smoke CART efficiency was observed as 67.25% and 55.78% for low and medium load conditions at a PIT and PIM of 20°CA aTDC and 2mg while operating on the microalgae bio-alcohol. Likewise, the maximum de-HC CART efficiency was obtained at a PIT and PIM of 10°CA aTDC and 1mg with a reduction of about 75% and 73.8% for medium and high load conditions. A slight reduction in oxides of nitrogen with the complete elimination of carbon monoxide emissions is observed after CART treatment for both the fuels.

Elucidating NO coupling effects on ignition of toluene reference fuels by chemical functional group analysis

Derived cetane number (DCN), Research and Motor Octane Numbers (RON and MON) have been fundamentally analyzed using Quantitative Structure-Property Relationship (QSPR) regression models with key chemical functional groups. Both RON and MON exhibit strong sensitivities to the abundances of (CH2)n and benzyl-type groups but lack sensitivity to the CH3 group, most dominant in real gasolines. Residual and EGR gases contain NOx known to synergize with fuel autoignition chemistry. Two TRF mixtures having high and low aromatic content but sharing the same RON and MON values were used to evaluate NOx coupling effects. DCN measurements with NO addition were found to be strongly correlated with the abundance of the (CH2)n group. Similar experiments of 200 ppm NO in a Rapid Compression Machine show promotion (inhibition) of ignition for the high (low) aromatic TRF fuel. Kinetic modeling attributes the promotion to the NONO2 interconversion reactions, NO + HO2 = NO2 + OH, CH3 + NO2 = CH3O + NO and NO2 + H = NO + OH. The inhibitive effect relates specifically to low temperature kinetics and high NO loading conditions, leading to the formation of meta-stable species (e.g. CH3 + NO2 (+M) = CH3NO2 (+M)) that decelerate the rate of conversion of HO2 to more reactive OH radicals. The coupling of NO with real gasolines depends on chemical composition and temperature conditions not only encompassed by RON and MON criteria, but by the chemical functional group characteristics. The relevance of this finding to the significance of preferential vaporization of multi-component gasolines on low-speed pre-ignition (LSPI) is discussed. Within the context of chemical functional group distributions of five distillation cuts of a marketed ethanol-free gasoline determined by NMR spectroscopy, the analyses identify considerable variations of key functionalities with fuel distillation properties, indicating chemical kinetic autoignition behaviors that are dependent on preferential vaporization.

Effect of diesel and propanol blends on regulated pollutants and polycyclic aromatic hydrocarbons under lean combustion conditions

AbstractAlcohols such as n‐propanol and diesel fuel can be mixed to increase the rate of bioalcohol utilization while reducing harmful pollutants. Examination of exhaust emissions from diesel engines, in terms of both regulated pollutants and unregulated polycyclic aromatic hydrocarbons (PAHs), is very important to the environment, public health, and engine durability. For this purpose, in this study, diesel blends with various n‐propanol concentrations (5%, 20%, and 35% by volume) were evaluated in a diesel engine. Regulated emissions were measured using a standard 5‐gas analyzer and polycyclic aromatic hydrocarbons were detected and quantified using gas chromatography–mass spectrometry (GC–MS). The effect of blended fuels on PAH formation (total PAHs, PAH distribution, and PAH toxicity) was examined in detail and compared with baseline diesel. Nitrogen oxide (NOx) emissions were reduced by 18.30% with higher n‐propanol concentrations. The addition of n‐propanol to diesel decreased total PAHs by as much as 71.20%. The fuel blend with a 20% n‐propanol concentration stood out with a maximum reduction of 91.23% in the toxicity of PAHs. In addition, n‐propanol led to a substantial decrease in the distribution of high ring aromatic compounds. Overall, it was demonstrated that n‐propanol is an effective additive to not only reduce the total PAH emissions and toxicity but also heavier PAHs which are more carcinogenic and cause a greater risk of the wetstacking issues for engines under cold operating or low load conditions.

Experimental investigation on diesel ignited dual fuel homogeneous charge compression ignition engine for the selection of suitable alcohol based fuel

Homogeneous charge compression ignition (HCCI) engine has fuel flexibility and can reduce NOX and soot emissions. The present work aims to investigate the dual-fuel mode HCCI engine (DF–HCCI–E) performance and exhaust emissions for different fuel types, namely, Methanol, Ethanol, Propanol, and Butanol. The CI Engine is converted into a DF-HCCI engine by attaching the carburetor to the inlet manifold for experimentation. Royal Enfield bullet 500 cc, Mikarb type carburetor was attached outside the engine cylinder to prepare the homogenous air-fuel mixture. Alcohol-based fuel (low reactivity) was supplied through the carburetor at the suction stroke time. Diesel (high reactivity fuel) was injected to start the combustion at the end of the compression stroke. It is observed that the P100+D DF–HCCI–E is suitable for low and high load conditions, while B100+D DF–HCCI–E is suitable for mid-load conditions. Results showes that Methanol has the highest cooling potential and lowest NOX emission compared to the rest of the fuels. And also, B100+D DF–HCCI–E reduced the highest smoke opacity for all load conditions compared to the rest of the ABF. Simple Additive Weighting (SAW) optimization was carried out, and it is concluded that P100+D has the best cumulative performance for low and high load conditions and M100+D has the poorest cumulative performance for all load conditions.

Optical study of oxygen enrichment on methane combustion characteristics under high compression-ratio conditions

Natural gas is a promising fuel for IC engines with low carbon emissions, whereas its poor lean combustion performance at low load and low engine power output at high load remain a challenge for automobile manufacturers. Oxygen-enriched combustion can provide more opportunities for collisions between fuel and oxygen molecules; thus, methane combustion performance can be improved. In this work, using a high-compression-ratio optical engine, the effects of oxygen enrichment on methane combustion were comprehensively investigated, addressing the similarities and differences between high load and low load conditions. High-speed direct photography and simultaneous pressure were performed to capture detailed combustion evolutions. The results show that high oxygen concentration can greatly increase methane flame propagation speed under high energy density condition (high load). As a result, advanced combustion phase and high peak pressure are obtained by more concentrated heat release, which in turn are indicators for improvised thermal efficiencies. Under low energy density condition (low load), oxygen enrichment mainly acts as a promoter of the initial flame formation, which in turn are indicators for improvised combustion stability. A detailed comparison of flame characteristics confirms the different effects of oxygen enrichment on methane combustion under different energy density conditions. Besides, oxygen enrichment can significantly promote initial flame formation with a higher rate and lower cyclic variation, and a low degree of oxygen enrichment can also have a great effect. The current study shall give insights into the strategies for oxygen enrichment on methane engines’ performance at different loads.

Reliability increase of resonance induction heating units during the fault conditions

Purpose. To develop an automatic protection system against fault operation conditions for the resonant inverter of the induction heating unit due to absence of load. Methodology. Resonant inverter load transfer function analysis using the first harmonic approximation, calculation of control parameters using numerical methods, computer simulation of induction heating unit. Experimental studies based on a smelter with microprocessor control in order to check the adequacy of the proposed model and protection system. Findings. A computer model of the induction heating unit is presented, the adequacy of which was verified by the experimental results of the induction melting unit. By using this model, circuit protection circuit of the resonant inverter against low load conditions is developed, which is based on the shift of the inverter operating frequency due to the introduction of an additional shift of the phase difference between current and voltage in the feedback loop. The methodology for calculating this phase shift was created using the load transfer function of the inverter (‘capacitor bank-inductor-part’ system) and numerical methods for solving equations. The above calculation method can be used for resonant inverters of any configuration and topology. According to the computer simulation of the induction heating unit operation during fault, the developed system limits the voltage amplitude within the safe operating region of the inverter reactive elements, while in normal operating conditions the protection system does not affect the operation of the unit. The protection system successfully keeps the amplitude of current and voltage in the oscillating circuit within safe limits during low loads. The created system is simple enough for its quick implementation in existing digitally controlled units and has high speed. Originality. Methodology to create voltage limiting system for resonant inverters of any configuration with frequency control has been developed. Practical value. Developed protection system allows to reduce induction heating process interruption by the user. Moreover, protection system increases fault tolerance of induction heating units. Structure of proposed protection system simplifies the modernization of existing units and the development of new models using such system.

Plastic collapse analysis in multiaxially loaded defective pipe specimens at different temperatures

A comprehensive numerical investigation is carried out using a newly developed constitutive model to describe failure at low temperatures in multiaxially loaded cracked pipes made of 316L stainless steel. The kinetic phase transformation and the temperature-dependent fracture criterion are implemented to accurately capture the mechanical response at different temperature levels. Although experimental observations of these simulations were not available, their results were quite consistent with some already published results obtained on similar materials and loading conditions at room temperature. The results indicate that the existing multiaxial plastic collapse failure criterion, including shearing, still provides a fail-safe design margin for low temperature loading conditions, including internal pressure. Moreover, martensite kinetic phase transformation plays an important role, especially during straining at low temperatures.

Social threat and safety learning in individuals with adverse childhood experiences: electrocortical evidence on face processing, recognition, and working memory

ABSTRACT Background: Adverse childhood experiences (ACEs) are often associated with stress and anxiety-related disorders in adulthood, and learning and memory deficits have been suggested as a potential link between ACEs and psychopathology. Objective: In this preregistered study, the impact of social threat learning on the processing, encoding, and recognition of unknown faces as well as their contextual settings was measured by recognition performance and event-related brain potentials. Method: Sixty-four individuals with ACEs encoded neutral faces within threatening or safe context conditions. During recognition, participants had to decide whether a face was new or had been previously presented in what context (item-source memory), looking at old and new faces. For visual working memory, participants had to detect changes in low and high load conditions during contextual threat or safety. Results: Results showed a successful induction of threat expectation in persons with ACEs. In terms of face and source recognition, overall recognition of safe and new faces was better compared to threatening face-compounds, with more socially anxious individuals having an advantage in remembering threatening faces. For working memory, an effect of task load was found on performance, irrespective of threat or safety context. Regarding electrocortical activity, an old/new recognition effect and threat-selective processing of face–context information was observed during both encoding and recognition. Moreover, neural activity associated with change detection was found for faces in a threatening context, but only at high task load, suggesting reduced capacity for faces in potentially harmful situations when cognitive resources are limited. Conclusion: While individuals with ACE showed intact social threat and safety learning overall, threat-selective face processing was observed for item/source memory, and a threatening context required more processing resources for visual working memory. Further research is needed to investigate the psychophysiological processes involved in functional and dysfunctional memory systems and their importance as vulnerability factors for stress-related disorders.

Investigation of the effects of passive pre-chamber nozzle pattern and ignition system on engine performance and emissions

The impact of passive pre-chamber (PC) internal volume, nozzle hole pattern (i.e. with and without a central axial nozzle), and PC igniter plug type on performance and emissions was investigated in an optically accessible, single-cylinder, gasoline research engine. The two PC igniter plugs investigated were a conventional inductive coil spark plug and a nanosecond repetitively pulsed (NRP) plasma discharge system previously demonstrated to accelerate early flame propagation. The baseline PC design featured a funnel shaped internal volume with a PC tip that contained six radial nozzles and a larger central axial nozzle. Two additional PC tip geometries were evaluated where either the baseline internal volume was increased or the axial nozzle was removed and the radial nozzle diameters were increased. A sweep of charge equivalence ratios ( ϕ) from nearly stoichiometric to the lean limit was performed for a fixed engine speed (1300 revolutions per minute), and engine load (3.5 bar gross indicated mean effective pressure). Time-resolved PC and main chamber (MC) pressure data as well as MC emissions data were collected to analyze engine performance and emissions characteristics. Combustion in the MC was further investigated using high-speed excited methylidyne radical (CH*) chemiluminescence imaging. Collected results highlighted that while all PC tips and ignition systems exhibited similar performance and emissions down to ϕ = 0.8, relevant differences in thermal efficiency and emissions for leaner charge mixtures were observed, with the results highly dependent on the nozzle pattern and ignition system. Major deviations were correlated to preferential de-pressurization of the PC through the axial nozzle for lean conditions that was not observed for mixture conditions closer to stoichiometric. Results show that a combination of radial and axial nozzle patterns in the PC extended lean-stability limits at the low-load condition evaluated. Further benefits were observed with the use of NRP ignition systems due to faster combustion within the PC volume provided that the volume was sufficiently large.

Preparation of polyethylene glycol brush grafted from the surface of nitrile butadiene rubber with excellent tribological performance under aqueous lubrication

The water-lubricated bearing will be in a state of poor lubrication when marine stern shafts operate under low speed and heavy load conditions, which could cause severe wear and vibration, endangering the stealth performance of underwater vehicles. In this study, the grafting of polyethylene glycol brush was carried out on the surface of nitrile butadiene rubber (PEG-g-sNBR) by “grafting from” method. Fourier-transform-infrared-spectroscopy, nuclear-magnetic-resonance, and scanning-electron- microscope results demonstrated that the PEG-g-sNBR brush was successfully synthesized, and the reactive site was found. Using a tribological test machine with a high-precision vibration acceleration sensor, the tribological behaviors of PEG-g-sNBR were studied under aqueous lubrication. The results showed that the coefficient of friction of PEG-g-sNBR was reduced by 73.4% at 100 rpm compared to pure NBR, its microscopic wear and vibrational energy were also lower than pure NBR. Moreover, the lubrication states were revealed by friction, wear, together with the complexity of friction-induced vibration signal time series, and a lubricating film was formed on the friction surface of PEG-g-sNBR at lower rotational speed. In addition, the PEG-g-sNBR could work stably for 12 h at 300 rpm, and still maintain good tribological performance.

Effect of mixed nonionic surfactants on microemulsion phase boundary, fuel property, and engine performance of biofuels

Microemulsion biofuels can become one of alternative biodiesels using suitable nonionic surfactants and cosurfactant to emulsify vegetable oil and ethanol with the appropriate formulae. Without the further chemical improvement, the low volatility and high viscosity because of triglycerides in vegetable oil can cause a serious problem in engine operation. This work proposed a systematic investigation of microemulsion biofuel prepared from rice bran oil and ethanol using mixed nonionic surfactant systems (Dehydol LS7, Tween 80, and Span 80) as surfactant (S) and 1-octanol as a cosurfactant (C) at molar ratio of 1:30. Microemulsion phase behaviors can be examined through the ternary phase diagram of rice bran oil, ethanol, and S:C. It was observed that Dehydol LS 7 was poor in solubilization of rice bran oil and ethanol because of their preference in hydrophilic compounds rather than lipophilic compounds. Introduction of Tween 80 or Span 80 into the biofuels using Dehydol LS 7 enhanced the solubilization of these systems as the extent of single-phase boundary was significantly enlarged because of the hydrophilic–lipophilic balance of the mixture and chemical structure of surfactants. The fuel properties of microemulsion biofuel were investigated through kinematic viscosity, specific gravity, flash point, cloud point, pour point, and higher heating value. It was found that mixed surfactant also improved some fuel properties due to additional surfactants contain many oxygenated functional groups, however, some parameters were slightly substandard. The combustion characteristics and exhaust emission were investigated in CI diesel engine. It was observed that the in-cylinder pressure was lower under the combustion of microemulsion fuel mainly due to the high latent heat of vaporization of alcohols. The start of combustion was more retarded with the addition of Span 80, especially at low load condition. It was observed that the significant reduction in nitrogen oxides was achieved with the combustion of microemulsion fuel while unburnt hydrocarbon emissions were higher compared to diesel fuel. The obtained experimental data showed that microemulsion biofuels can be a promising alternative biodiesel although the individual usage in engine was slightly less efficient than commercial diesel fuel.