Browse Topic: Lubricant additives

Items (161)

Influences of Lubricant Viscosity and Metallic Content on Diesel Soot Oxidation Reactivity

2024-01-508408/23/2024

This study examined the effects of lubricant viscosity and metallic content on the oxidation reactivity of diesel particles. In the first part, the factors affecting thermogravimetric analysis (TGA) experiments was discussed and confirmed. The influences of initial soot mass, heating rate, and airflow rate on soot oxidation rate and experimental reproducibility were investigated to develop an optimized TGA method. On the basis of these experiments, an initial soot mass of 2.0 mg, airflow rate of 4.8 L/h, and heating rate of 2.5°C/h were used for all subsequent TGA tests. It could be found that the TGA experiments had high repeatability, and the differences were less than 0.1%. In the second part, a four-cylinder diesel engine was lubricated with seven kinds of lubricant with different viscosity and metallic content by the use of viscosity index improver (VII), antioxidant and corrosion inhibitor (ACI), and ashless dispersant (AD). Particle samples were subjected to TGA to test their

Meng, Hao, Yang, He, Zhang, Weili, Xing, Jianqiang, Xu, Yan, Wang, Yajun

Role of Lubricating Oil Properties in Exhaust Particle Emissions of an Off-Road Diesel Engine

2020-01-038604/14/2020

Particle number emissions from an off-road diesel engine without exhaust after-treatment were studied by using five different heavy-duty lubricating oils in the engine. The study extends understanding on how the properties of lubricating oil affect the nanoparticle emissions from an off-road diesel engine. The lubricants were selected among the performance classes of the European Automobile Manufacturers Association, at least one lubricant from each category intended for heavy-duty diesel engines. Particle size distributions were measured by the means of an engine exhaust particle sizer (EEPS), but soot emissions, gaseous emissions and the basic engine performance were also determined. During the non-road steady state cycle, the most of the differences were detected at the particle size range of 6-15 nm. In most cases, the lowest particle quantities were emitted when the highest performance category lubricant was used. Based on the results of this study, the low contents of Zn, P, and

Ovaska, Teemu, Niemi, Seppo, Sirviö, Katriina, Nilsson, Olav, Karjalainen, Panu, Rönkkö, Topi, Kulmala, Kari, Keskinen, Jorma

Characteristics of Auto-Ignition for Lubricants and Lubricant/Gasoline Based on an Innovative Single Droplet Test System

2020-01-142804/14/2020

Due to the advantages of low weight, low emissions and good fuel economy, downsized turbocharged gasoline direct injection (GDI) engines are widely-applied nowadays. However, Low-Speed Pre-Ignition (LSPI) phenomenon observed in these engines restricts their improvement of performance. Some researchers have shown that auto-ignition of lubricant in the combustion chamber has a great effect on the LSPI frequency. To study the auto-ignition characteristics of lubricant, an innovative single droplet auto-ignition test system for lubricant and its mixture is designed and developed, with better accuracy and effectiveness. The experiments are carried out by hanging lubricant droplets on the thermocouple node under active thermo-atmosphere provided by a small “Dibble burner”. The auto-ignition process of lubricant droplets is recorded by a high-speed camera. Influences of different base oil types, viscosities, calcium contents, initial droplet diameters, co-flow speeds, new oil, used oil and

Yu, Yang, Pan, Kaifeng, Deng, Jun, Hu, Zongjie, Xie, Wei, Wu, Zhijun, Li, Liguang

Comparative Study on the Effect of Different Lubricating Oil Additives on the Tribological Properties of Bearing Steel

05-13-01-000201/23/2020

The purpose of this article is to study the antifriction and anti-wear effect of GCr15 bearing steel under paraffin base oil and the base oil with two additives of T405 sulfurized olefin and nano-MoS2 and compare the synergistic lubrication effect of two different additives (MoS2 and T405) in paraffin base oil. The tribological properties of GCr15 bearing steel under different lubrication conditions were tested on a ball-on-disk tribometer. The three-dimensional profile of disk’s worn surfaces and the scanning electron microscope (SEM) micrographs of corresponding steel balls were analyzed at the same time. The wettability of lubricating oils on the surface of friction pairs and the dispersibility of MoS2 in base oil were characterized. Furthermore, the Energy Dispersive X-ray Analysis (EDAX) of the disk’s worn surfaces under the nano-MoS2 base oil were measured by the Field Emission Environmental Scanning Electron Microscope to observe the variation of chemical elements on the worn

Xia, Zhaocai, Tang, Wencheng, Li, Kaiyuan, Wang, Hao

A Comparative Tribological Performance of Lubricating Oils with Zinc Dialkyl Dithiophosphate and Zinc Oxide Nanoparticles as Additives

2019-28-017410/11/2019

The present work compares the tribological properties of ZnO (Zinc Oxide) nanoparticle based lubricant with ZDDP (zinc dialkyl dithiophosphate) based lubricant. The nanolubricant was prepared by mixing the nanoparticles in base oil followed by ultrasonification and ZDDP based lubricant was prepared by mixing ZDDP and stirring with base oil. Base oil used was mineral base oil. Both the lubricants were tested at three different temperatures, loads and roughness values. The test was carried out on AISI 52100 steel samples prepared by wire cutting and were grinded to three different levels of surface roughness. Friction and wear tests were performed using a reciprocating sliding tribo-tester at three different loads and temperatures. Taguchi orthogonal array was used to reduce the number of experiments. SEM, EDS and AFM analysis were carried out to study the surface wear phenomenon. The coefficient of friction was found to be low in the case of ZnO nanolubricant but wear was found to be

Payyappalli Mana, Anil, Bimal Shah, Archit, Kothari, Karan

The Effect of Pressure, Temperature and Additives on Droplet Ignition of Lubricant Oil and Its Surrogate

2018-01-167309/10/2018

Numerous studies have attributed pre-ignition events in turbocharged spark ignited engines to the auto-ignition of lubricant oil-fuel mixture droplets. These droplets result from the interaction of the directly injected fuel spray on the lubricant oil film on the cylinder walls, causing fuel splashing to pull oil off the walls, forming droplets. The dilution of the oil by the fuel also changes lubricant oil droplet properties. Therefore, it is important to understand lubricating oils, with and without fuel dilution, as a possible ignition source in pre-ignition and super knock events. In this work, a constant volume (4 L) combustion chamber (CVCC) that allows the introduction of a single droplet of lubricating oil has been built. It is capable of operation at elevated pressures and temperatures. To simulate the droplet-induced pre-ignition event, a droplet injection system was incorporated into the vessel. The oil droplet was suspended on the junction of a thermocouple where the

Maharjan, Sumit, Qahtani, Yasser, Roberts, William, Elbaz, Ayman

Combined Fuel and Lubricant Effects on Low Speed Pre-Ignition

2018-01-166909/10/2018

Many studies on low speed pre-ignition have been published to investigate the impact of fuel properties and of lubricant properties. Fuels with high aromatic content or higher distillation temperatures have been shown to increase LSPI activity. The results have also shown that oil additives such as calcium sulfonate tend to increase the occurrence of LSPI while others such as magnesium sulfonate tend to decrease the occurrence. Very few studies have varied the fuel and oil properties at the same time. This approach is useful in isolating only the impact of the oil or the fuel, but both fluids impact the LSPI behavior of the engine simultaneously. To understand how the lubricant and fuel impacts on LSPI interact, a series of LSPI tests were performed with a matrix which combined fuels and lubricants with a range of LSPI activity. This study was intended to determine if a low activity lubricant could suppress the increased LSPI from a high activity fuel, and vice versa. The results

Kocsis, Michael Clifford, Briggs, Thomas, Anderson, Garrett

Numerical Analysis on the Potential of Reducing DPF Size Using Low Ash Lubricant Oil

2018-01-176009/10/2018

Diesel particulate filter (DPF) is necessary for diesel engines to meet the increasingly stringent emission regulations. Many studies have demonstrated that the lubricant derived ash has a significant effect on DPF pressure drop and engine fuel economy, and this effect becomes more and more severe with the increasing of operating hours of the DPF because the ash accumulated in the DPF cannot be removed by regeneration. It is reported that most of the DPFs operated with more ash than soot in the filter for more than three quarters of the time during its lifetime [1]. In order to mitigate this problem, the original engine manufacturers (OEM) tend to use an oversized DPF for the engine. However, it will increase the costs of the DPF and reduce the compactness of the engine aftertreatment system. With the development of the lubricant additives technology, some OEMs and lubricant oil manufacturers are concerning that if there is any possibility to reduce DPF size using low ash lubricant oil

Zhang, Jun, Qi, Jinzhu, Shuai, Shi-Jin, Wang, Lei, Liu, Shiyu, Wang, Guoyang, Liu, Fan, Brown, Jason

Auto-ignition Characteristics of Lubricant Droplets under Hot Co-Flow Atmosphere

2018-01-180709/10/2018

It has been revealed by researches that lubricant properties have a great effect on the low-speed pre-ignition (LSPI) frequency in downsizing turbocharged direct-injection engines which are developed for better fuel economy. Droplets of lubricant or lubricant-gasoline mixture are considered to be the potential pre-ignition sources. Those droplets fly into the combustion chamber and ignite the gasoline-air mixture. To study lubricant droplets fundamentally, a novel set of droplet auto-ignition system is designed based on a Dibble Burner for this experiment. Influences of metallic additive contents, viscosities, lubricant diluted with gasoline and waste lubricant on the ignition delay of droplets are investigated by testing 12 groups of lubricants or lubricant-gasoline mixture. The equivalent diameter of each droplet generated by micro-syringes is around 2.1 mm. The co-flow temperature varies from 1123 K to 1223 K, and the experiments are carried out at atmospheric pressure. The auto

Pan, Kaifeng, Deng, Jun, Chen, Yongquan, Zhang, Erbao, Xie, Wei, Qin, Qiushi, Qu, Zongju, Li, Liguang

An Experimental Investigation of Tribological Performance of a Lubricant Using Different Nano Additives

2018-01-083304/03/2018

A novel solution to anti wear-additives is to add relatively small amounts of effective Nano Additives to the main content of lubricants. Such supplement would offer an enhancement to their tribological and thermal properties as wear resistance and friction surface temperature. In this work, different types of Nano additives are used to investigate their effect on the tribological properties of a certain lubricant (TOTAL FLUIDE AT42). Three main Nano additive materials were used with two different concentration for each; Gamma aluminum oxide (Alumina Al2O3), Copper Oxide (CuO) and one-dimensional carbon Nano tubes (CNT). A pin on disc equipment fitted out with circulated lubricant system was operated for 140 hours with normal lubricant, and for 140 hours for each case of the three Nano additives, with a total working time of 980 hours. Weight loss of the pin, friction surface temperature and friction force were measured every 20 working hours. Results showed that there is an

Akl, Sayed Y., Abdel-Rehim, Ahmed A., Elsoudy, Sherif

Long Life Engine Oil in China

2017-01-235210/08/2017

Fuel economy, Emission regulation and extended oil drain intervals (ODI) are the three key driving forces for engine oil development. More and more attentions have been focused on long ODI diesel engine oil both from the domestic OEMs and oil suppliers, and the ODI was being periodically improved from a normal mileage of about 1×104 kilometers to 6/8/10×104 km or even 12×104 km just within several years on China market. Lots and lots of factors may affect the oil life including oil properties, engine technologies, after-treatment devices and engine working conditions and so on. While from the oil side, the main factors contribute to the oil drain intervals may be the oil nitration and oxidation, soot contamination, base number deterioration and sludge accumulation and etc. There are two strategies to extend the oil longevity applied currently. One is the use of slow-release lubricant additives filters, in which the additives are incorporated into the oil filters, which slowly release

Liu, Gongde, Wang, Li, Zhang, Runxiang, Yang, Chao, Shao, Tengfei

Steric Effects on Tribochemical Reactivity in Detergent-Containing Lubricants under Nanoconfinement

2017-01-234710/08/2017

Modern formulation in a wide variety of lubricants including engine oils and transmission fluids is designed to control friction through film-forming tribochemical reactions induced by the functional additives mixtures. Although many cases on the synergistic or antagonistic effects of additives on friction have been reported, their mechanisms are poorly understood. This study focused on the influences of metallic detergents on tribochemical reactions. We examined the mechanical properties of detergent-containing lubricants confined at a single-asperity contact and their contributions to tribochemical phenomena. We found that detergents enlarged the confinement space required for generating repulsive force and shear resistance. This means that these detergents provide steric effects under nanoconfinement at interfacial contacts. These detergents reduced friction synergistically with molybdenum dithiocarbamate (MoDTC), which is a widely used friction modifier additive that forms a

Tamura, Kazushi, Sunahara, Kenji, Ishikawa, Motoharu, Mizukami, Masashi, Kurihara, Kazue

Effects of Lubricant Additives on Auto-Ignition under a Hot Co-Flow Atmosphere

2017-01-223110/08/2017

Pre-ignition may lead to an extreme knock (super-knock or mega-knock) which will impose a severe negative influence on the engine performance and service life, thus limiting the development of downsizing gasoline direct injection (GDI) engine. More and more studies reveal that the auto-ignition of lubricants is the potential source for pre-ignition. However, pre-ignition is complicated to study on the engine test bench. In this paper, a convenient test method is applied to investigate the influence of lubricants metal-additives on pre-ignition. 8 groups of lubricants are injected into a hot co-flow atmosphere which generated by a burner. A single-hole nozzle injector with a diameter of 0.2 mm at 20 MPa injection pressure is utilized for lubricants' injection and spray atomization. The ignition delays of lubricants with different additives of calcium, ZDDP (Zinc Dialkyl Dithiophosphates) and magnesium content under the hot co-flow atmosphere are recorded with a high-speed camera. The

Chen, Yongquan, Li, Liguang, Zhang, Qing, Deng, Jun, Xie, Wei, Zhang, Erbao, Tong, Sunyu

Extensional Rheology: New Dimension of Characterizing Automotive Fluids

2017-01-036403/28/2017

This paper describes the basic principles of extensional rheometry, and the successful application to a variety of automotive fluids, including gear lubricants, paints, and forming lubricants. These fluids are used under very complex flow fields containing strong extensional (elongational) components. While exact derivation of extensional viscosities involves sophisticated theories, the measurement of liquid filament break-up time can provide fruitful information. Gear lubes showed different break-up time according to the kinematic viscosities. Addition of viscosity modifier (acrylic copolymer) significantly increased the breakup time, whereas surfactants had little effect. Clearcoat paint sample increased the breakup time, perhaps due to the deterioration. The waxy stamping lubricant showed remarkable change in the extensional properties as the temperature is raised. The extensional data obtained showed the promise of the technique to understand the performance of these fluids in

Ohtani, Hiroko, Ellwood, Kevin, Pereira, Gustavo, Chinen, Thiago, Selvasekar, Siddharthan

Experimental Investigation on the Influence of Engine Oil Additives on Silicone Rubber

2017-01-087703/28/2017

In developing engine oils, it is crucial to consider their compatibility with the rubbers used for seals. Among the different seal rubbers, silicone rubber is particularly susceptible to attack by acids and bases, which means it would be more likely to be affected by certain engine oil additives. In this study, the effects of some major additives, namely detergents, zinc dialkyl-dithiophopshate (ZDDP) and molybdenum dithiocarbamate (MoDTC), on silicone rubber were investigated. Silicone rubber test specimens were immersed in sample oils containing these additives for a prescribed period at 150°C, then the physical properties of the test specimens were measured to compare the effects of the different additives. It was found that ZDDPs dramatically reduce the tensile strength of silicone rubber, with primary ZDDP having a greater effect than secondary ZDDP. Analyses of the test specimens by means of Fourier Transform Infrared Spectroscopy (FT-IR) revealed that the silicone rubbers had

Yoshimura, Kenichi, Kunieda, Kenichi, Suzuki, Nozomu, Kusuhara, Shintaro, Matsuki, Shingo, Shitara, Yuji

HARD, SLICK AND READY TO ROLL

17AUTP03_0303/01/2017

A tough, self-renewing catalyst coating developed at Argonne National Laboratory provides unprecedented friction and wear protection for vehicle powertrains, the inventors claim. Powertrain system engineers know that of the energy consumed in transportation, 10% to 15% is lost due to parasitics in engines and drivelines. Researchers at Argonne National Laboratory have developed a new breed of nanocomposite coatings, which are made of the nitrides of transition metals and metal catalysts. These coatings provide a catalytically active, hard, and slick surface on metal components. They could have a major impact on improving the efficiency of automotive engines and gearboxes. Transportation vehicles account for about 19% of annual world energy consumption and approximately 23% of total greenhouse gas emissions. With the global vehicle parc steadily growing, these numbers will likewise swell and present serious challenges for a sustainable mobility future. The new nanocomposite coatings

Erdemir, Ali

Optimizing engine oil warm-up strategies for ‘real-world’ driving

16AUTP11_0611/01/2016

Optimizing engines for the new era of ‘real-world’ driving cycles will require new lubrication strategies-fast warm-up being a particular area of focus. A recent U.K. government survey showed that the average car journey time has fallen to only 22 minutes and average distance to 12 km (7.5 m), most of it in urban areas. And such extreme duty cycles are increasingly typical in other global regions. They emphasize rapid warm-up for reducing emissions and fuel consumption, faster cabin heating and reduced maintenance. But the contribution to warm-up time due to heating the oil within the engine is often under-estimated, experts note.

Birch, Stuart

Research on the Effect of Lubricant Oil and Fuel Properties on LSPI Occurrence in Boosted S. I. Engines

2016-01-229210/17/2016

The effects of lubricant oil and fuel properties on low speed pre-ignition (LSPI) occurrence in boosted S.I. engines were experimentally evaluated with multi-cylinder engine and de-correlated oil and fuel matrices. Further, the auto-ignitability of fuel spray droplets and evaporated homogeneous fuel/oil mixtures were evaluated in a combustion bomb and pressure differential scanning calorimetry (PDSC) tests to analyze the fundamental ignition process. The work investigated the effect of engine conditions, fuel volatility and various lubricant additives on LSPI occurrence. The results support the validity of aspects of the LSPI mechanism hypothesis based on the phenomenon of droplets of lubricant oil/fuel mixture (caused by adhesion of fuel spray on the liner wall) flying into the chamber and autoigniting before spark ignition. Combustion bomb experiments confirmed that lubricant oil sprays have higher auto-ignitability than gasoline fuel components, and no particular effects of

Kassai, Masaharu, Torii, Ken, Shiraishi, Taisuke, Noda, Toru, Goh, Tor Kit, Wilbrand, Karsten, Wakefield, Shaun, Healy, Adam, Doyle, David, Cracknell, Roger, Shibuya, Masahiko

Physicochemical Mechanisms for Fluoroelastomer Seal Failures

2016-01-227210/17/2016

Elastomer compatibility is an important property of lubricants. When seals degrade oil leakages may occur, which is a cause of concern for original equipment manufacturers (OEMs) because of warranty claims. Leakage is also a concern for environmental reasons. Most often, the mechanical properties and fitting of the oil seals is identified as the source of failure, but there are cases where the interaction between the lubricant and the seal material can be implicated. The performance of seal materials in tensile testing is a required method that must be passed in order to qualify lubricant additive packages. We conducted an extensive study of the interactions between these elastomeric materials and lubricant additive components, and their behavior over time. The physicochemical mechanisms that occur to cause seal failures will be discussed.

Bennett, Carl, Bell, Jason, Guevremont, Jeffrey

Advanced Lubrication - Enabling and Protecting Turbocharged, Direct Injection Gasoline Engines for Optimum Efficiency

2016-01-227510/17/2016

There has been a global technology convergence by engine manufacturers as they strive to meet or exceed the ever-increasing fuel economy mandates that are intended to mitigate the trend in global warming associated with CO2 emissions. While turbocharging and direct-injection gasoline technologies are not new, when combined they create the opportunity for substantial increase in power output at lower engine speeds. Higher output at lower engine speeds is inherently more efficient, and this leads engine designers in the direction of overall smaller engines. Lubricants optimized for older engines may not have the expected level of durability with more operating time being spent at higher specific output levels. Additionally, a phenomenon that is called low-speed pre-ignition has become more prevalent with these engines. While more pre-ignition may be expected with highly-boosted engines, an especially destructive version of this has been found to be related to some of the essential

Yang, Kongsheng, Fletcher, Kristin A., Styer, Jeremy P., Lam, William Y., Guinther, Gregory H.

Acid Neutralization and Engine Hardware Corrosion Protection through Heavy-Duty Diesel Lubricant Additive Chemistry

2016-01-231810/17/2016

One of the primary functions of modern heavy duty diesel (HDD) lubricants is to protect the engine against corrosion, which is typically accomplished by additives providing alkaline material, commonly represented as total base number (TBN). The majority of the TBN in HDD lubricants comes from ash-containing over-based detergents, with various metallic base and soap chemistries. In this publication, we discuss several overbased detergents and their efficacy in acid neutralization, as well as the resulting impact on corrosion protection. The performance differences are compared in a number of stationary API CJ-4 and CK-4 HDD engine screener tests. Furthermore, these results are confirmed with field trial data, including a comparison of CJ-4 oils with the upcoming API FA-4/CK-4 oils. The selection of overbased detergent type provides varying levels of acid neutralization and corrosion protection. Within a constrained sulfated-ash environment, TBN can be maximized via the use of magnesium

Lin, Wangkan, Diggs, Nancy, Frampton, Catherine

Engine Oil Additive Impacts on Low Speed Pre-Ignition

2016-01-227710/17/2016

Low speed pre-ignition (LSPI) is an undesirable combustion phenomenon that limits the fuel economy, drivability, emissions and durability performance of modern turbocharged engines. Because of the potential to catastrophically damage an engine after only a single pre-ignition event, the ability to reduce LSPI frequency has grown in importance over the last several years. This is evident in the significant increase in industry publications. It became apparent that certain engine oil components impact the frequency of LSPI events when evaluated in engine tests, notably calcium detergent, molybdenum and phosphorus. However, a close examination of the impact of other formulation additives is lacking. A systematic evaluation of the impact of the detergent package, including single-metal and bimetal detergent systems, ashless and ash-containing additives has been undertaken using a GM 2.0L Ecotec engine installed on a conventional engine dynamometer test stand. Consistent with previous

Fletcher, Kristin A., Dingwell, Lisa, Yang, Kongsheng, Lam, William Y., Styer, Jeremy P.

Electrical Conductivity of New and Used Automatic Transmission Fluids

2016-01-220510/17/2016

Hybrid drivetrain hardware combines an electric motor and a transmission, gear box, or hydraulic unit. With many hybrid electric vehicle (HEV) hardware designs the transmission fluid is in contact with the electric motor. Some OEMs and tier suppliers have concerns about the electrical properties of automatic transmission fluids (ATFs). Lubrizol has conducted a fundamental research project to better understand the electrical conductivity of ATFs. In this paper, we will present conductivity data as a function of temperature for a range of commercially available ATFs. All fluids had conductivities ranging from 0.9 to 8x10-9 S/cm at 100 °C and can be considered insulators with the ability to dissipate static charge. Next we will deconstruct one ATF to show the relative impact of the various classes of lubricant additives. We find that more polar additives have a larger effect on conductivity on a normalized (per weight %) basis. Finally, we will show conductivity data for ATFs taken from

McFadden, Chris, Hughes, Kevin, Raser, Lydia, Newcomb, Timothy

Characteristics of Lubricants on Auto-ignition under Controllable Active Thermo-Atmosphere

2016-01-088904/05/2016

Downsizing gasoline direct injection engine with turbo boost technology is the main trend for gasoline engine. However, with engine downsizing and ever increasing of power output, a new abnormal phenomenon, known as pre-ignition or super knock, occurs in turbocharged engines. Pre-ignition will cause very high in-cylinder pressure and high oscillations. In some circumstances, one cycle of severe pre-ignition may damage the piston or spark plug, which has a severe influence on engine performance and service life. So pre-ignition has raised lots of attention in both industry and academic society. More and more studies reveal that the auto-ignition of lubricants is the potential source for pre-ignition. The auto-ignition characteristics of different lubricants are studied. This paper focuses on the ignition delay of different lubricants in Controllable Active Thermo-Atmosphere (CATA) combustion system. In this study, many tests were conducted in the CATA combustion system .The result of

Fan, Chuang, Tong, Sunyu, Xu, Xiaohong, Li, Jing, He, Xiao Yu, Deng, Jun, Li, Liguang

Methods for Rating the Viscosity-Temperature Behavior of Polymer-Containing Lubricants

2015-01-204809/01/2015

The Viscosity Index (VI, ASTM D2270) has a long and widespread history as a rating scale for the viscosity-temperature behavior of lubricants. However, the method has serious technical deficiencies which can lead to misleading conclusions. We have examined alternatives to the VI scale in an effort to more accurately characterize the viscometric behavior of modern lubricants, which are formulated with highly refined base oils and advanced polymers. We have found that the VI method can actually mask improved viscosity-temperature behavior for certain highly additized polymer-containing lubricants. We examine two different methods, the Roelands Slope Index and the Proportional VI, as an alternative to VI. It is important for lubricant developers and consumers to be aware of the limitations of the VI scale in describing the viscometric qualities of modern, high performance lubricants.

Zakarian, Jack, Webb, Michael E., Hunter, Brett

Oxidation Stability Study of Biobased Lubricant Basestocks

2015-01-204609/01/2015

One of the concerns for biolubricants is the improvement of their oxidation resistance. In this paper the oxidative behavior of seven different types of biobased lubricants basestocks is examined. The aim was to study their relative oxidation stability and also to investigate their response to various antioxidants. The renewable lubricants were treated with four antioxidant additives at a concentration of 0.5% wt. and a comparative assessments of the latters' effectiveness in suppressing the oxidation rate was carried out. Alterations in the acid value were examined as well as relative changes of the oxidized samples by FTIR spectroscopy. The oxidation stability was assessed by employing a Rapid Small Scale Oxidation Test (RSSOT) apparatus according to the accelerated oxidation stability standard method ASTM D7545/EN16091. RSSOT is a relatively new method and thus the behaviour of biobased lubricants and antioxidant agents in this accelerated method has not been thoroughly examined.

Dodos, George S., Anastopoulos, George, Zannikos, Fanourios E., Lois, Evripidis

Effects on Tribology Performance of a Reducing Additive for Automobile Lubricant

2015-01-204709/01/2015

We developed a unique reducing additive composed primarily of polyolester, diester, and vegetable oil-based ester compounds in order to switch from boundary to fluid lubrication and improve tribology performance, and chemically and experimentally investigated its effects on tribology performance. To confirm the lubrication effects of this reducing additive, we added it to oil and chemically investigated the cleaning and dissolving of the ultra-fine particle layer of contaminants, etc., adhering to lubrication pathways and sliding surfaces, and performed commercialization testing using actual vehicles. We found that this additive washed away and dissolved sludge, varnish, and other contaminants from lubricated surfaces, improving their lubrication properties and their tribology performance by reducing abrasion and friction.

Satonaga, Noriaki, Watanabe, Takashi

Investigation and Improvement of LSPI Phenomena and Study of Combustion Strategy in Highly Boosted SI Combustion in Low Speed Range

2015-01-075604/14/2015

LSPI is an important issue to enable and enhance the effect of downsizing in SI engines. Experimental work was carried out by using 4 cylinder turbocharged gasoline engine, attaching the extra supercharger to get a higher boost pressure. Many parameters of driving condition, engine specification and lubricants were studied and some of them were extracted as the major items which affect the possibility of LSPI. Coolant temperature and Calcium (Ca) additive to lubricant had strong effect on the frequency of LSPI. Combustion strategy of strong miller cycle and LPEGR were also studied and compared in very high BMEP condition. Finally IMEPg of 3MPa at 1500rpm was achieved by using a single cylinder test engine equipped with 2-stage mechanically supercharged intake system.

Morikawa, Koji, Moriyoshi, Yasuo, Kuboyama, Tatsuya, Imai, Yasuo, Yamada, Toshio, Hatamura, Koichi

A Study on the Effect of Zn- and Mo-Based Engine Oil Additives on Abnormal SI Engine Combustion using In-Cylinder Combustion Visualization

2014-32-009611/11/2014

Spontaneous low-speed pre-ignition, strong knock and other abnormal combustion events that occur in supercharged direct-injection engines are viewed as serious issues. The effects of the engine oil and the components of engine oil additives have been pointed out as one cause of such abnormal combustion. However, the mechanisms involved have yet to be elucidated, and it is unclear how the individual components of engine oil additives influence autoignition. This study investigated the effect on autoignition of boundary lubricant additives that are mixed into the engine oil for the purpose of forming a lubricant film on metal surfaces. A high-speed camera was used to photograph and visualize combustion through an optical access window provided in the combustion chamber of the four-stroke naturally aspirated side-valve test engine. Spectroscopic measurements were also made simultaneously to investigate the characteristics of abnormal combustion in detail. We mixed Zinc additive into

Hayakawa, Norikuni, Miura, Kenta, Miyasaka, Tomomi, Ishino, Takashi, Iijima, Akira, Shoji, Hideo, Tamura, Kazushi, Utaka, Toshimasa, Kamano, Hideki

Tribological Properties of Automotive Lubricant SAE 20W-40 Containing Nano-Al ₂ O ₃ particles

2014-01-278110/13/2014

The need for advanced lubricants is increasing rapidly due to the current wide range of operational usage, i.e., high loads and speeds of motion between friction pairs, broader temperature range, and the overall requirements for increased reliability and service life of machinery. It is essentially important to develop specialized anti-friction and anti-wear materials that will help in preventing wear and decreasing friction, thereby saving fuel and electricity. Simultaneously, such materials are also expected to reduce vibration, noise and maintenance of machine parts. Thus, the research into extending the service life of such materials continues to be imperative. Nanoparticles (NPs) present a novel approach in this regard, as they can be used in lubricants in between two mating contact surfaces as a third body. When compared with the widely used conventional micro-particles for tribological applications, NPs have unique features owing primarily to their much higher specific surface

Mohan, Nishant, Sharma, Mayank, Singh, Ramesh, Kumar, Naveen

Minimizing Diesel Particulate Filter Incombustibles by Using Ultra Low Ash - Zero Phosphorus Oil

2014-01-279810/13/2014

Due to engine oil consumption, over 90% of the incombustibles in the diesel particulate filters (DPF) are derived from organometallic lubricant additives. These components are derived from calcium and magnesium detergents, zinc dithiophosphates (ZnDTP) and metal-containing oxidation inhibitors. They do not regenerate as they are non-volatile metals and salts. Consequently, the DPF has to be removed from the vehicle for cleaning. Ashless oil could eliminate the need for cleaning. This study initially focused on development of an ashless oil, but eventually concluded that this oil could not meet the valve-train wear requirements of the API CJ-4, SN/ACEA E9 oil categories. However, a zero-phosphorus oil with no ZnDTP and an extremely low sulfated ash of 0.4% demonstrated that it could meet critical engine tests in API CJ-4/ACEA/SN. The above oil, which has been optimized at 0.3% sulfated ash, has proven field performance in Cummins ISX with DPF using ultra low sulfur diesel (ULSD). This

McGeehan, James A., Van Dam, Wim, Nelson, Ken, Boffa, Alex, Carabell, Kevin, Walker, Andrew, Caserta, Jon, Conway, Raymond

Effects of Combustion Parameters and Lubricating Oil on Particulate Matter Emissions from a Turbo-Charged GDI Engine Fueled with Methanol/Gasoline Blends

2014-01-284110/13/2014

The aim of this research is to experimentally investigate the effects of combustion parameters [ignition timings, injection timings, excess air ratio (λ)] and lubricating oil on particulate matter (PM) emissions from a 2.0 L turbo-charged gasoline direct injection (T-GDI) engine fueled with gasoline (octane number = 97), methanol/gasoline blends and pure methanol. The results of this paper show that the PM number concentration mostly presents a typical bimodal distribution in figures. The particle number concentration mainly concentrates in the nucleation mode. With the increase of methanol volume fraction in the blended fuel, the PM emissions decrease significantly. Furthermore, there are few particles when the engine fueled with pure methanol. As advancing ignition timing, the total PM number rises by over about 200%. Under the pre-ignition condition, the higher in-cylinder temperature may also accelerate the formation of the nucleation mode particles. As advancing injection timing

Qin, Jing, Li, Xiang, Pei, Yiqiang

Frictional Characteristics of Crystalline Calcium Sulfonate Detergent in Engine Oil by Mini-Traction Machine

2014-01-278910/13/2014

Harsh emission control regulation restricted the sulfated ash, sulfur and phosphorus (SAPS) level in passenger car motor oil (PCMO), thus lubricant industry need to find new additive to partially or wholly replace Zinc dialkyldithiophosphate (ZDDP), which has been used as an antioxidant and anti-wear agent for several decades. Overbased crystalline calcium sulfonate (CCS) detergent comprises calcite calcium carbonate and this structure might be useful to improve the anti-wear property of engine oil in severe lubrication condition, especially for PCMO with lower SAPS level. Frictional characteristics were studied between overbased amorphous calcium sulfonate (ACS) detergent and CCS and their interactions with dispersant and ZDDP by Mini-Traction Machine, which is often used to measure the Stribeck Curve of lubricant. In poly alpha-olefin base oil, both the two detergents showed lower traction coefficient in boundary lubrication (BL) regime, and higher traction coefficient in mixed

Cao, Congrui, Liu, Gongde, Zhang, Runxiang, She, Haibo, Tao, Qiangqiang

Tribological Characteristics of Yttria Stabilized Zirconia Nanolubricants

2014-01-279010/13/2014

Nanolubricants are suspensions of nanoparticles in base fluids, a new challenge for thermal sciences provided by nanotechnology. The objective of this work is to analyze the thermal and tribological properties of yttria stabilized zirconia (YSZ) nanolubricants. Nanosized YSZ particles were prepared by milling YSZ (10μm) in a planetary ball mill equipped with vials using tungsten carbide balls. After 40 hrs, milled YSZ nanoparticles of sizes ranging from 70-90nm were obtained. The nanoparticles were characterized by Energy Dispersive X-ray analysis (EDXA), Scanning Electron microscope (SEM), Transmission Electron Microscope, Thermo Gravimetric-Differential Scanning Calorimeter and non contact 3D surface profilometer and the images of the same were obtained. The heat transfer properties of automotive engine lubricants were determined by utilization of measured thermal conductivity, viscosity index, density, flash point, fire point and pour point, which revealed that lubricants with

Ganapathy Pandian, Sakthinathan

Radio Frequency Diesel Particulate Filter Soot and Ash Level Sensors: Enabling Adaptive Controls for Heavy-Duty Diesel Applications

2014-01-234909/30/2014

Diesel Particulate Filters (DPF) are a key component in many on- and off-road aftertreatment systems to meet increasingly stringent particle emissions limits. Efficient thermal management and regeneration control is critical for reliable and cost-effective operation of the combined engine and aftertreatment system. Conventional DPF control systems predominantly rely on a combination of filter pressure drop measurements and predictive models to indirectly estimate the soot loading state of the filter. Over time, the build-up of incombustible ash, primarily derived from metal-containing lubricant additives, accumulates in the filter to levels far exceeding the DPF's soot storage limit. The combined effects of soot and ash build-up dynamically impact the filter's pressure drop response, service life, and fuel consumption, and must be accurately accounted for in order to optimize engine and aftertreatment system performance. This work applied a radio frequency (RF) sensor to directly

Sappok, Alexander, Bromberg, Leslie

Impact of Lubricant Composition on Low-speed Pre-Ignition

2014-01-121304/01/2014

One of the limits on the maximum fuel efficiency benefit to be gained from turbocharged, downsized gasoline engines is the occurrence of pre-ignitions at low engine speed. These pre-ignitions may lead to high pressures and extreme knock (megaknock or superknock) which can cause severe engine damage. Though the mechanism leading to megaknock is not completely resolved, pre-ignitions are thought to arise from local autoignition of areas in the cylinder which are rich in low ignition delay “contaminants” such as engine oil and/or heavy ends of gasoline. These contaminants are introduced to the combustion chamber at various points in the engine cycle (e.g. entering from the top land crevice during blow-down or washed from the cylinder walls during DI wall impingement). This paper presents results from tests in which model “contaminants”, consisting of engine lubricant base stocks, base stocks mixed with fuel and base stocks mixed with one or more additives were injected directly into a

Welling, Orian, Collings, Nick, Williams, John, Moss, James

Effect of Accelerated Aging Rate on the Capture of Fuel-Borne Metal Impurities by Emissions Control Devices

2014-01-150004/01/2014

Small impurities in the fuel can have a significant impact on the emissions control system performance over the lifetime of the vehicle. Of particular interest in recent studies has been the impact of sodium, potassium, and calcium that can be introduced either through fuel constituents, such as biodiesel, or as lubricant additives. In a collaboration between the National Renewable Energy Laboratory and the Oak Ridge National Laboratory, a series of accelerated aging studies have been performed to understand the potential impact of these metals on the emissions control system. This paper explores the effect of the rate of accelerated aging on the capture of fuel-borne metal impurities in the emission control devices and the subsequent impact on performance. Aging was accelerated by doping the fuel with high levels of the metals of interest. Three separate evaluations were performed, each with a different rate of accelerated aging. The aged emissions control systems were evaluated

Williams, Aaron, McCormick, Robert, Lance, Michael, Xie, Chao, Toops, Todd, Brezny, Rasto

Direct Measurements of Soot/Ash Affinity in the Diesel Particulate Filter by Atomic Force Microscopy and Implications for Ash Accumulation and DPF Degradation

2014-01-148604/01/2014

Inorganic engine lubricant additives, which have various specific, necessary functions such as anti-wear, leave the combustion chamber bound to soot particles (approximately ≤1% by mass) as ash [13], and accumulate in aftertreatment components. The diesel particulate filter (DPF) is especially susceptible to ash-related issues due to its wall-flow architecture which physically traps most of the soot and ash emissions. Accumulated lubricant-derived ash results in numerous problems including increased filter pressure drop and decreased catalytic functionality. While much progress has been made to understand the macroscopic details and effects of ash accumulation on DPF performance, this study explores the nano- and micron-scale forces which impact particle adhesion and mobility within the particulate filter. Several recent studies have revealed several important mechanisms influencing the nature of the soot and ash deposits, which if manipulated, could yield means of actively minimizing

Kamp, Carl Justin, Sappok, Alexander, Wang, Yujun, Bryk, William, Rubin, Avery, Wong, Victor

Methodology to Compare Effectiveness of Lubricating Additives in a Polymeric Matrix

2014-01-103404/01/2014

A majority of the plastics manufacturing operations are dependent on the formability of the molten thermoplastics. Ability of the material to flow at a set temperature influences the formability and the overall polymer melt process. Lubricating additive technologies are being developed to engineer the melt flow performance of the resin, promoting the compounding and molding process such as to reduce torque on the motor, reduced shear degradations, enhance uniform filling of hard-to-fill section, promoting thin wall molding, and influence the overall cycle time. Various lubricants are used in formulations to supplement superior flow and metal release with minimal effect on mechanical properties. This paper discusses the methodology to characterize the effectiveness of melt flow additives through comparing two different processing aids in Polybutylene terephthalate (PBT) polyester filled and unfilled matrix and imply differences in processing. The learning from findings in this paper can

Shrivastava, Anshuman, Scheel, Mark, Strama, Julie

Effect of Low Viscosity Passenger Car Motor Oils on Fuel Economy Engine Tests

2013-01-260610/14/2013

The fuel economy performance of passenger car vehicles has been an area of keen focus due to recent environmental regulations. Various efforts such as the development of new engine technologies have been undertaken to improve the fuel economy performance of these vehicles. Engine oils have also been targeted to contribute to better fuel efficiency. This has been done by introducing new lubricant additive technologies and low viscosity grade oils. In the latter case, passenger car motor oils are about to enter into a new generation in which the lower viscosity grade SAE 16 has been approved and discussion has started on the specification of viscosity grades lower than SAE 16, although SAE 0W-20 viscosity grade is the lowest in the SAE J300 specification during last decade. Nevertheless, additive technology is also important, as we previously reported that simple reduction of viscosity grade is not a solution to improve fuel economy performance in the Sequence VID test. In this paper

Ushioda, Nobuo, Miller, Trevor W., Sims, Carrie B., Parsons, Gary, Sztenderowicz, Mark

Demonstration of Fuel Economy Benefit of Friction Modifier Additives via Fuel-to-Lubricant Transfer in Euro-5 Gasoline Fleet

2013-01-261110/14/2013

Improved fuel economy is a key measure of performance in the automotive industry, driven both by market demand and increasingly stringent government emissions regulations. In this climate, targeting even small benefits to fuel consumption (FC) can have a large impact when considering fleet average CO2 emissions. Lubricant properties over the course of an oil drain interval (ODI) directly influence long-term fuel consumption. Furthermore, viscosity control gasoline additives have been shown to provide FC benefit via fuel-to-lubricant transfer. This study investigated whether consistently fueling with gasoline containing friction modifier (FM) additives could provide a long-term fuel consumption benefit via a lubricant transfer mechanism. A robust fleet trial method was employed to quantify fuel consumption benefits of two friction modifier additive packages relative to a baseline deposit control additive (DCA) package in a 95 RON, E5 fuel. FC was measured for 32 market relevant vehicles

Remmert, Sarah M., Felix-Moore, Alison, Nattrass, Steven R., Buttery, Ian, Ziman, Pauline, Smith, Sue J.

Assessment of Low Temperature Viscosity Performance in Modern Engine Oils

2013-01-256510/14/2013

Control of oil viscosity increase at low temperature, which derives from the wax crystallization behaviors of various formulation components, is a critical performance criterion in modern engine oil lubricants. Failure to manage viscosity increase will result in high oil viscosity and poor oil pumpability under cold start conditions, and eventually may lead to catastrophic damage to the engine. The importance of oil low temperature rheology gained further attention when the ILSAC GF-4 specification implemented an aged oil low temperature viscosity limit to guarantee performance retention during operation. This requirement continues in ILSAC GF-5 and is regarded as one of the key benchmarks of modern passenger car engine oils. Pour point depressants (PPDs) are polymeric additives that help alleviate viscosity increase under tcold climate conditions through interaction and control of wax crystallization growth. With increasingly diverse base stock supplies and quality standards

Wang, Jen Lung

Sensitivity Analysis of Ash Packing and Distribution in Diesel Particulate Filters to Transient Changes in Exhaust Conditions

2012-01-109304/16/2012

Current CJ-4 lubricant specifications place chemical limits on diesel engine oil formulations to minimize the accumulation of lubricant-derived ash in diesel particulate filters (DPF). While lubricant additive chemistry plays a strong role in determining the amount and type of ash accumulated in the DPF, a number of additional factors play important roles as well. Relative to soot particles, whose residence time in the DPF is short-lived, ash particles remain in the filter for a significant fraction of the filter's useful life. While it is well-known that the properties (packing density, porosity, permeability) of soot deposits are primarily controlled by the local exhaust conditions at the time of particle deposition in the DPF, the cumulative operating history of the filter plays a much stronger role in controlling the properties and distribution of the accumulated ash. Results of this work indicate that short-duration, transient, high temperature events can have a profound impact on

Sappok, Alexander, Kamp, Carl, Wong, Victor

Management of Lubricant Fuel Economy Performance over Time through Fuel Additives

2012-01-127004/16/2012

Government regulations and market demands continue to emphasize conservation of fossil fuels in the transportation industry. As a consequence, any incremental improvement in fuel economy (FE) is of great importance in the automotive sector. For instance, lower viscosity lubricants have been shown to improve FE but the longevity of such improvement is compromised by viscosity increases often observed as a lubricant ages during an oil drain interval (ODI). To address this issue, an option to manage lubricant viscometrics via fuel is proposed. In order to investigate such mitigation of viscosity increase during an ODI, and potentially the delivery of an ODI-averaged FE benefit, a fleet test was conducted with a fuel-borne additive intended to control increases in lubricant viscosity. The fleet test compared a market-representative reference fuel to a fuel containing a viscosity control additive (VCA). Five different European vehicle models were tested over a 15,000 mile ODI using a “quad

Rappaport, Scott, Nattrass, Steve, Smith, Sue, Brewer, Mark, Buttery, Ian, Ma, Hongrui

Study of Lower Viscosity Motorcycle Engine Oils for Fuel Saving-Anti-fatigue Performance-

2011-32-063411/08/2011

1 Fuel savings by engine oil have been requested for two-wheeled vehicles from the viewpoint of environmental issues. In four-wheeled vehicles, reduction of oil viscosity and addition of friction modifiers have been effective in improving fuel efficiency. However, direct application of engine oil for four-wheeled vehicles to two-wheeled vehicles is difficult. In a four-cycle two-wheeled vehicle, the transmission, gears, and a wet clutch system are imbedded within the engine1). Engine oil must display a remarkable performance as it is required to function as transmission oil and to improve anti-metal fatigue life and clutch performance2), 3). If fuel efficiency is improved by reducing the viscosity of engine oil used in two-wheeled vehicles, the fatigue life tends to worsen. Therefore, reduction in oil viscosity is difficult to achieve. In this study, the anti-metal fatigue life of an engine oil was evaluated using a gear or a rolling bearing in a crankshaft where fatigue failures may

Watanabe, Nobuaki, Inuzuka, Maiko, Mitarai, Akira

Research on Emissions and Engine Lube Oil Deterioration of Diesel Engines with BioFuels (RME)

2011-01-130204/12/2011

In the diesel sector the fatty acid methyl esters (FAME's) - in Europe mostly RME (rapeseed methyl ester) and in US mostly SME (soja oil methyl ester) - are used as a various share, % volume blends with the diesel fuel (B5, B7, B10, B20, Bxx). The present joint project focuses on RME being the most important representative of the biofuels of 1st generation in Europe. The influences of RME blend fuels on emissions and on lube oil deterioration are emphasized. Emissions were investigated on a modern engine with exhaust gas aftertreatment devices like SCR and (DPF+ SCR). Beside the legally limited exhaust emission components some non-legislated like NO₂, N₂O, NH₃ and nanoparticles were measured at stationary and dynamic engine operation. The most important findings are: - the increased percentage of RME w/o aftertreatment causes an increase of NOx by higher engine load and reduction of CO & HC; at transient operation (ETC) these tendencies are less pronounced and only B100 shows an

Stepien, Zbigniew, Urzedowska, Wieslawa, Oleksiak, Stanislaw, Czerwinski, Jan

Role of Fuel Decomposition Products on Formation of Sequence IIIG Piston Deposits

2010-01-225910/25/2010

Previous research to understand the mechanism for piston deposit formation in the Sequence IIIG engine test has focused on characterizing the piston deposits. These studies concluded that, in addition to lubricant derived materials, Sequence IIIG piston deposits contain a significant amount of fuel-derived carbonaceous material. The presence of fuel degradation by-products in Sequence IIIG deposits shows that blow-by is a significant contributor to deposit formation. However, blow-by can either assist in the degradation of the lubricant or can simply be a source for organic material which can be incorporated into the deposits. Therefore, a series of modified Sequence IIIG engine tests were conducted to better determine the effect of blow-by on deposit formation. In these studies deposit formation on different parts of the piston assembly were examined since different parts of the piston assembly are exposed to different amounts of blow-by. Furthermore, the rate of deposit formation in

Devlin, Mark T., Dvorak, Todd, Sheets, Roger, Bell, Ian, Loper, John, Guevremont, Jeffrey, Guinther, Gregory

Waste Lubricating Oil as a Source of Hydrogen Fuel using Chemical Looping Steam Reforming

2010-01-219210/25/2010

Initial results are presented for the production of hydrogen from waste lubricating oil using a chemical looping reforming (CLR) process. The development of flexible and sustainable sources of hydrogen will be required to facilitate a "hydrogen economy." The novel CLR process presented in this paper has an advantage over hydrogen production from conventional steam reforming because CLR can use complex, low value, waste oils. Also, because the process is scalable to small and medium size, hydrogen can be produced close to where it is required, minimizing transport costs. Waste lubricating oil typically contains 13-14% weight of hydrogen, which through the steam reforming process could produce a syngas containing around 75 vol% H₂, representing over 40 wt% of the fuel. The waste oil was converted to a hydrogen-rich syngas in a packed bed reactor, using a Ni/ Al₂O₃ catalyst as the oxygen transfer material (OTM). An oil conversion rate based on carbon species (CO, CO₂ and CH₄) of up to ~95

Lea-Langton, Amanda, Giannakeas, Nikolaos, Rickett, Gavin, Dupont, Valerie, Twigg, Martyn

Waste Lubricating Oil as a Source of Hydrogen Fuel using Chemical Looping Steam Reforming

2010-01-2192-TEST-REC10/25/2010

Lea-Langton, Amanda, Giannakeas, Nikolaos, Rickett, Gavin, Dupont, Valerie, Twigg, Martyn

Study of Lower Viscosity Motorcycle Engine Oils for Fuel Saving

2010-32-012309/28/2010

As well as a four-wheeled vehicle, in the field of motorcycle, development of the CO₂ reduction technology and practical use are required for global environment protection. Therefore the energy conserving by engine oil is required. There are several technologies which have been applied to the passenger car engine oils using lower viscosity base oils and some friction modifier additives. However, these technologies might bring difficulties or problems to apply to the motorcycle engine oils. Since motorcycles normally have transmission gears and a wet clutch system inside the crankcase, the gear lubricity and clutch friction performance are additionally required for motorcycle engine oils. Motorcycle engine oils are also used under severer conditions than passenger car engine oils. Therefore, lower volatility performance at higher temperature conditions, higher shear stability, anti-wear performance and gear pitting toughness are needed. In this study, we report the results of motorcycle

Watanabe, Nobuaki

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