Lubricating Oil Research Articles

Combustion and emission characteristics of a gasoline/ammonia fueled SI engine and chemical kinetic analysis of NOx emissions

Mitigating climate change involves the greater adoption of carbon–neutral and renewable energy sources within the transportation sector. Ammonia (NH3), as a carbon-free and sustainable fuel, has garnered growing interest in recent years. The present study aims to investigate the impact of NH3 blending on combustion and emission characteristics of a stoichiometric spark-ignition gasoline engine, with a particular emphasis on nitrogen-based emissions. The experimental investigation was complemented by chemical kinetic calculations. The results showed that NH3 blending could effectively suppress engine knock, optimize combustion phase and improve thermal efficiency. For pure gasoline, advancing the spark timing resulted in increased NOx emissions. However, when NH3 was blended, NOx emissions decreased with advancing spark timing, indicating a negative correlation with pressure. The NH3 emission was attributed to the ‘crevice mechanism’ as well as the absorption/desorption in the lubricant oil film on the cylinder wall. Chemical kinetic analysis revealed that the NOx emission from NH3 blended combustion is closely related to reactive radicals such as OH, H and O. The reduction in NOx emissions under high-pressure conditions was primarily attributed to the consumption of these reactive radicals via three-body reactions. Interestingly, NOx emissions initially increased with increasing NH3 blending ratio but eventually followed a decreasing trend. This can be attributed to the lower combustion temperature, lower concentration of reactive radicals, and enhanced de-NOx reactions.

Purification of Used Lubricating Oils Using Vacuum Distillation

Engine oil (EO) is produced by mixing base oil derivatives from crude oil with chemical additives to the lubricity of moving parts and reduce the friction inside the engine. Used lubricating oil (ULO) is one of the hazardous materials that consists of pollution harmful to the environment, it needs to be managed properly. In this work, vacuum distillation technique is used to recycle used lubricating oil. Used lubricating oil samples from two different brands of diesel engine oil (20w-50) and gasoline engine oil (10W-30) are used in this study. Various properties of ULO and recycled oil were characterized such as kinematic viscosity, viscosity index, density, pour point, flash point, Sulphur content, and Fourier transform Infrared spectroscopy FTIR. The yield recycles for ULO of gasoline engines, diesel engines, and mix (gasoline and diesel) by vacuum process were 85%, 74%, and 75% respectively, it was discovered that the sulfur component decreased from 9792.3 ppm of ULO to 405 ppm of yield distillates. The pour point results show an increase from -30 °C of used lubricating oil to -18 and -6 for distillates cut for vacuum distillation, compared to the pour point of Iraqi base oil 40 and 60 Stook (SN150 and SN200) -18 °C and -6 °C

Elastohydrodynamic lubrication simulation analysis and experimental verification of different tandem reciprocating rod seal systems

Utilizing multiple seals in tandem is a prevalent technique employed to enhance the reliability of hydraulic sealing systems. In this paper, based on the elastohydrodynamic lubrication simulation of a single seal interface, a methodology for evaluating the performance of tandem reciprocating rod seal systems is established by manipulating the boundary conditions of the seals based on the principle of flow conservation. Through the simulation of two sealing systems, it is observed that inadequate lubricating oil occurs in the second sealing ring when the first sealing ring surpasses its sealing performance. Conversely, if the second sealing ring outperforms the first one, pressure will be generated between them. Additionally, a self-constructed experimental platform is utilized, and the results demonstrate simulation accuracy within an error margin of less than 15% when compared to the corresponding experimental measurements.

TCN-GAWO: Genetic Algorithm Enhanced Weight Optimization for Temporal Convolutional Network

Abstract This article proposes a genetic algorithm (GA)-enhanced weight optimization method for temporal convolutional network (TCN-GAWO). TCN-GAWO combines the evolutionary process of the genetic algorithm with the gradient-based training and can achieve higher predication/fitting accuracy than traditional temporal convolutional network (TCN). Performances of TCN-GAWO are also more stable. In TCN-GAWO, multiple TCNs are generated with random initial weights first, then these TCNs are trained individually for given epochs, next the selection-crossover-mutation procedure is applied among TCNs to get the evolved offspring. Gradient-based training and selection-crossover-mutation are taken in turns until convergence. The TCN with the optimal performance is then selected. Performances of TCN-GAWO are thoroughly evaluated using realistic engineering data, including C-MAPSS dataset provided by NASA and jet engine lubrication oil dataset provided by airlines. Experimental results show that TCN-GAWO outperforms existing methods for both datasets, demonstrating the effectiveness and the wide range applicability of the proposed method in solving time series problems.

Investigation on lubricity effectiveness Ficus carica lubricant modified with PTFE and TBHQ as additives for steel-steel contact application

The application of additives to the bio-lubricants is essential to improve the base oil tribological properties. A high-frequency reciprocating rig and different operating conditions were used to test the effects of tert-butylhydroquinone (TBHQ) and polytetrafluoroethylene (PTFE) polymer on the tribological performance of Ficus carica oil as a base oil for machine lubrication. The viscosity and Fourier transform infrared spectroscopy (FT-IR) evaluations were carried out to ascertain the additive's effectiveness. A scanning electron microscope was used to analyse the morphologies and the substrate-worn surfaces. When additives were applied separately, 1 wt% of PTFE produced a superior coefficient of friction (COF) and better wear reduction than other examined samples. In terms of wear resistance, commercial lubricant oil (CLO) SAE 5 W-30 performed better than the optimal 1 wt% PTFE + 0.3 wt% TBHQ blended with Ficus carica oil (FCO/L). At an increased frequency of 5 Hz, CLO outperformed FCO/L on COF and wear resistance. When examining the worn surfaces, less iron (Fe) was discovered on the FCO/L than the base Ficus carica oil, demonstrating the mending effect of the used additive as the underlying mechanism of wear reaction. The results show promising potential for the new formulation of a green lubricant since the tribological characteristics of Ficus carica oil were improved by the addition of the selected additives.

Influence of spent oil on soil physical properties and performance of two okra varieties (Abelmoschus esculentus) in PortHarcourt, Rivers State, Nigeria

A study was conducted at the Department of Crop and Soil Science teaching farm, University of Port Harcourt to examine the effect of lubricant automobile oil on soil physical properties and performance of Abelmoschus esculentus for a period of eight weeks. Composite soil samples were collected randomly at depths of 0-20 cm. The soil was placed in 10 kg buckets. Spent lubricant oil collected from the automobile mechanic workshop was used to contaminate the soils at 0, 2, 4, and 6% w/v. Two varieties of Okra V1 (local) and V2 (Clensom spineless) were used. Three okra seeds were planted two weeks after contamination and later thinned to two. Each treatment was replicated thrice; the design was completely randomized. The results showed that the spent oil had no effect on per cent germination on V1 in the treatments and at 0 and 2% contamination for V2. As contamination increases, the percent germination of V2 decreases to 83.3 and 72.2% for 4 and 6% respectively. Increase in spent oil contamination reduced the height of the two varieties. V2 was more affected as percent contamination increases in week 1, thereafter, improves better than V1. No significant (p>0.05) difference in number of plant leaves even as contamination increased except in weeks 3, 5 and 6. Number of leaves decreased with increase in level of contamination and increases as the weeks increased in both varieties. Lowest number of leaves observed at 6% and highest at control in the two varieties. Leaf area of both varieties significantly reduced in contaminated over control though varietyV2 was significantly (p<0.05) higher than V1. Contamination of the soil did not change the textural class of the soil. Significant decrease was recorded in hydraulic conductivity of the soil between the contaminated and control. As the contamination level increased, hydraulic conductivity decreased. Contamination of the soil with lubricant oil increased the soil bulk density. The effect of hydrocarbon contamination was pronounced as there was delay in plant germinations, poor and stunted growth of the two varieties, and yellowing of leaves at the seventh and eighth weeks, especially at 6% contamination on both varieties.

A study of surface fatigue wear and influence of contaminated lubricant in journal bearing system using tribological and vibration analyses

In the present work, journal bearing performance was evaluated using condition monitoring processes namely wear debris, vibration signal, lubricant oil degradation and temperature analyses. The journal bearing system was operated at 800 rpm and 200 N constant speed and load over a period of 1200 h. The lubricant oil samples were collected for every 300 h of test duration for oil degradation and wear particle analyses by using Fourier transform infrared radiation (FTIR) and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS) techniques, respectively. FTIR results provided specific chemical bonds and functional groups contained in the degraded oil. The vibration signals were acquired for every 100 h of operation, and a fast Fourier transform (FFT) frequency spectrum technique was employed for vibration signal analysis. The friction coefficient and specific wear rate parameters were considered to evaluate the tribological performance of the journal-bearing system. Statistical parameters, namely root-mean-square and kurtosis, were evaluated. Wear mechanisms such as abrasive, adhesive and surface fatigue wear were observed on the journal-bearing contact surfaces using a USB optical microscope. The scoring on the bearing element confirmed the fault development and resulted in an increase in vibration amplitudes. Higher mass loss in the bearing material was observed due to high friction and wear rates owing to its being a softer material than that of the journal material. The results obtained from the aforementioned parameter assessment techniques provided a reliable information on the defects which appeared on journal-bearing contact surfaces.

Effect of Spent Lubricating Oil on Total Antioxidant Power, Total Flavonoid Content and Total Phenolic Content of Sorghum bicolor (L.) Mooch and Soyabean Glycine Max (L.) Merr Seedlings after 14 Days of Germination

Environmental pollution is a growing concern, with its detrimental effects on ecosystems, biodiversity, and human health. Spent lubricating oil (SLO) represents a pervasive environmental pollutant, often finding its way into soil and posing a significant threat to plant life. This study was to investigate effect of the fractions of SLO (water-soluble, WSF; water-insoluble, WISF; and crude whole SLO, cWSLO) and distilled water (DW) respectively. The WSF showed significant (P<0.05) decrease in both species of seedlings (Sorghum 15.34 mg GAE/g ± 2.01 and Soya-bean 16.87 mg GAE/g ± 0.86) from results of TAP when compared to that of DW while the cWSLO was most significantly (P<0.05) decreased. The TPC also revealed significant (P<0.05) decrease from the different fractions when compared to the control (DW) as well as that of the TFC values from the results. The disparities in TPC emphasize the selective influence of different SLO components on the production of phenolic compounds, which could be crucial for plant defense mechanisms against oxidative stress. Thus, the results of the study showed that although the different parameters indicated that SLO can affect the oxidative state of brown sorghum seeds but it can be seen that it may be possible for the plant to utilize some of the water soluble contents of the SLO to aid germination.

Wear pressure induced structural changes of OLC nanoparticles and their regulated lubrication performances by mixing with NDs and GO

Here we report the tribological properties of nanosized onion-like carbon (OLC), OLC-nanodiamond (ND), and OLC-graphene oxide (GO) as additives in lubricant oil tested under different wear pressure. Under the wear pressure of 588 N of the four-ball testing, the 0.125 wt% addition OLC reduced the wear volume and the wear scar diameter by 36.29 % and 82.42 %. TEM characterization revealed structural changes in contour of the OLC particles after the wear testing. Pressure-induced agglomeration was seen for the OLC nanospheres, and the squeezed lattice changes resulted in formation of sp3 diamond structure inside the spheres. These structural changes are directly related to the loading force. However, addition of the sp3 NDs and sp2 GO deteriorated the lubricating performances of the OLC-added lubricant oil.

Alleviating thermal challenges in hydrodynamic bearings: A novel approach through thrust bearing pads with embedded cooling circuitry and deep recess

At high speeds minimization of operating temperature is the critical design objective in hydrodynamic thrust bearings. During the high speed operations of heavy duty machines high temperatures are generated in thrust bearings due to vigorous viscous shearing of lubricant oil film. Under such circumstances thermal effects gain critical importance. Consequences of thermal effects include pad deformation, increased wear, material degradation etc. in hydrodynamic bearings. This research explores a pioneering approach to mitigate thermal challenges by integrating deep recesses and cooling circuitry in thrust bearing pads. The integrated design facilitates enhanced heat dissipation and load carrying capacity along with optimized lubrication process. In this study CFD (CFX) simulation code is used to numerically evaluate the effect of hybrid bearing configuration (conventional thrust pad equipped with deep recess and embedded cooling circuitry) on the performance parameters of thrust bearing. The simulation results confirm an appreciable decrease in maximum pad temperature and thermal pad deformation. The maximum pad temperature decreased from 85℃ to 71℃. Similarly value of thermal pad deformation decreased from 36 µm to 24 µm. The outcomes hold promise for enhancing the thermal performance of existing machinery and inspiring the development of next-generation thrust bearing systems, marking a transformative advancement in the field of mechanical engineering.

Jet aircraft lubrication oil droplets as contrail ice-forming particles

Abstract. The radiative characteristics and lifetimes of contrails are dependent on the number concentration of ice-forming particles in the engine exhaust plume. Aircraft gas turbine engines produce a variety of particles, yet it is understood that non-volatile black carbon aggregates are the dominant source of ice-forming particles with typical, fossil-derived jet fuel. However, with cleaner combustion technologies and the adoption of alternative fuels (e.g. hydrogen or synthetic aviation fuel), non-volatile black carbon particle emissions are expected to decrease or even be eliminated. Under these conditions, contrail properties will depend upon the concentration and characteristics of particles other than black carbon. Ultrafine (< 100 nm) jet lubrication oil droplets constitute a significant fraction of the total organic particulate matter released by aircraft; however, their ability to form contrail ice crystals has hitherto been unexplored. In this work, we experimentally investigate the activation and freezing behaviour of lubrication oil droplets using an expansion chamber, assessing their potential as ice-forming particles. We generate lubrication oil droplets with a geometric mean mobility diameter of (100.9 ± 0.6) nm and show that these activate to form water droplets, which subsequently freeze when the temperature is below ∼ 235 K. We find that nucleation on lubrication oil droplets should be considered in future computational studies – particularly under soot-poor conditions – and that these studies would benefit from particle size distribution measurements at cruise altitude. Overall, taking steps to reduce lubrication oil number emissions would help reduce the climate impact of contrail cirrus.

Conductive nano-Al/polyaniline composites prepared via mechanical milling

The conductive nano-Al/polyaniline composites were prepared by the milling method in the solid state. Here, aluminum nanostructures were prepared in two different mechanical methods, wire drawing and wire milling in the presence of lubricant oil. The effects of the preparation methods on the structures and morphologies of aluminum nanostructures were investigated by XRD and FESEM. The results show that the shape and size of aluminum nanoparticles in the preparation by the wire drawing method are significantly different than the wire milling method. The aluminum nanostructures were prepared by milling method have flake-like nanosheets while the wire drawing method leads to the formation of spherical ultrafine nanoparticles, which particles size are in the range of 30–60 nm. Then, polyaniline was produced using a solid-state polymerization process by the chemical reaction between aniline hydrochloride and potassium peroxydisulfate. Finally, nano-Al/polyaniline composites were prepared by mechanical milling at room temperature. The quantitative analysis was carried out with the materials analysis using diffraction (MAUD) method and weight fraction for aluminum and PANI were calculated 6.66% and 93.34%, respectively. Electrical conductivity measurements show the conductivity (1.2 × 10−2 S cm−1 at 25 °C) for polyaniline emeraldine salt and (1.02 × 10−3 S cm−1 at 25 °C) in nanocomposite respectively. The results show that by adding aluminum nanoparticles to the polymer the conductivity of nanocomposite (Al/PANI-ES) is lower than that for pure (PANI-ES). Thermogravimetry and differential thermal analysis curves show pure (PANI-ES) and nanocomposite (Al/PANI-ES) have a similar thermal degradation process. The total weight loss in TG curve of pure PANI-ES, in the temperature range 45–800 °C is 46.28% but, total weight loss observed in nanocomposite is 38.67%. Therefore, nanocomposite has higher thermal stability than that of the pure PANI-ES.

A novel TMR sensor based on digital lock-in amplifier technology for portable oil multipollutant detection system

Metal particles identification in lubrication oil has become a popular technology to perform the fault diagnosis and health monitoring of machinery equipment. Unfortunately, the magnetic signals induced by particles are generally weak or even submerged in heavy noise. The sensitivity of conventional inductive sensors for detecting non-ferrous particles can still be improved to better distinguish between different non-ferrous particles. Based on the above issues, this paper proposed a novel tunnel magnetoresistance (TMR) sensor based on digital lock-in amplifier (DLIA) technology to detect ferrous and multiple nonferrous metallic particles in oil under noisy conditions. Moreover, compared to conventional inductive sensor structures, the proposed method can effectively reduce the sensor volume, which is particularly necessary when considering the design of portable oil multipollutant detection system. Owing to the high resolution of TMR and outstanding versatility of DLIA for extracting weak signal overwhelmed in noise, the detection sensitivity can be improved tremendously. Extensive simulation and experimental results validated that the proposed approach was practical and effective. Based on the experimental results, the minimum values of detectable diameter could be computed as 24.76 µm for iron particles, 81.34 µm and 82.32 µm for copper and aluminium particles respectively.

Evaluation and Synthesis of Environmentally Benign Multifunctional Additives for Lube Oil

Behenyl acrylate (BA) homo-polymer and its copolymers with citral were synthesized with varying percentage compositions (w/w) and subjected to thorough characterization through GPC (gel permeation chromatography) analysis and spectroscopic techniques (FT-IR, NMR). The polymers' capability was assessed through viscosity index improvers/viscosity modifiers (VII or VM), anti wear (AW) additives and pour point depressants (PPD) for base oils (lubricating oil). The action mechanism of the PPD properties was investigated through photomicrographic analysis. Additionally, the thermal stability of the polymers was measured using TGA or thermo gravimetric analysis. Biodegradability tests on copolymers were conducted using soil burial test (SBT) and the Disc Diffusion (DD) method. The copolymers exhibited exceptional PPD, VII, and AW performance when incorporated into lubricating oil.

Modelling lubricating oil wear using fuzzy logic

The content of this article presents research on used and fresh engine oils. The aim of the experiment is to preliminarily develop a method for assessing the condition of engine oil subjected to service. A four-ball tester was used to compare the lubricating properties of the engine oil as one component of the tribosystem under laboratory conditions. The method used to determine the mashing load consisted of subjecting the kinematic node to a linearly increasing load with a build-up rate of 409 N·s-1 under operating conditions of approximately 20°C and a spindle speed of 500 rpm. The presented article is a continuation of the consideration of the lubricating properties of engine oils subjected to operation. The tests carried out made it possible to observe that fresh oils are characterised by their ability to carry higher loads in relation to oils subjected to service. This is evidenced by the obtained values of scuffing loads, which have a higher value for fresh oils (The average percentage increase in scuffing load for fresh oils was 62.23%). Comparing the friction torque characteristics with each other, it can be seen that the values of maximum friction torque are also higher for the fresh oils group. The modelling process made it possible to characterise changes in the tribological properties of the lubricating oil being used. In the future, the described model will be extended to include further input parameters (viscosity, contaminant content, fractional composition, etc.), which will allow a multi-parametric assessment of lubricating oil wear.

New recycling method of lubricant oil and the effect on the viscosity and viscous shear as an environmentally friendly

Abstract The present investigation adopts a new method to recycle the oils. The used and recycled lubricants were compared to fresh oil. Accordingly, an investigation was carried out to evaluate the viscous shear of different oil grades at each certain temperature using the Walther formula of the viscosity–temperature relationship. The investigation indicates acceptable and fair results in front of a technical point of view and environmental improvement by reducing pollution. The results show lower viscosity of the recycling oil than the used oil, which affects the viscous shear as it is directly proportional to the velocity gradient and the fluid’s viscosity at ascertaining temperature. In the present investigation, alum (Al2(SO4)3(H2O)18) was used, which gives good precipitation according to the practical results mentioned in this work. The used oils of grades 5w20, 5w30, and 10w30 under consideration are collected from the local internal combustion engines. Both kinematic viscosity and viscous shear for 10w30 oil grade record the highest values, and 5w20 records the lowest values for all oil types (fresh, recycled, and used oil).

Assessing the efficacy of three bio‐based flocculants in the reclamation of spent lubricating oil

AbstractThe current study encompasses a comprehensive assessment of three biopolymeric flocculants on the overall performance of recycling waste lubricating oil to achieve a higher percentage recovery, flocculation efficacy, and better quality of recovered base oil. The findings reveal that with experimental conditions such as (i) mixing time of 80 min; (ii) agitation speed of 400 rpm; (iii) reaction temperature 50°C; (iv) solvent to waste oil ratio 3:1 g/g; and (v) flocculant dosage 1 g/ kg of solvents, 1‐butanol and sodium alginate gives highest percentage yield of 91% followed by corn starch of 89.10% and xanthan gum of 87.18% as bio‐polymer flocculant. The effects of various process parameters of bio‐flocculants on flocculation efficiency are expounded. With the process parameters of (i) initial pH of 5.9, 6.0, and 6.2; (ii) mixing time − 59, 60, and 63 min; and (iii) solution temperature of 59, 60, and 62.2°C, maximum flocculation efficacy (% sludge removal) of 16.24%, 13.01%, and 14.09% were attained for the cases of refined oil treated with sodium alginate, corn starch, and xanthan gum, respectively. Results also reveal that the physicochemical properties of refined base oil treated with 1‐butanol and sodium alginate as bio flocculant are almost close to the virgin lubricating oil. The optimum recovery of high‐quality base oil with the adoption of green technology and solvent–bio flocculant combination can mitigate the environmental impact of waste oil and create an energy‐efficient sustainable condition for the regeneration of re‐refined base oil.

Spiral-wound organic solvent membrane modules for dewaxing solvent recovery

The petrochemical industry is typically energy-intensive, involving frequent and intricate separation processes. SINOPEC is a globally recognized lubricant manufacturer and distributor, with a substantial production capacity exceeding 1.7 million tonnes in 2022. The dewaxing solvent recovery process in lubricant production necessitates a multi-stage flash and distillation treatment, resulting in substantial energy consumption and high costs. Utilizing organic solvent nanofiltration (OSN) membranes offers a feasible alternative approach to address this issue. A series of thin film composite OSN membranes with varying molecule weight cut-offs were prepared through precise adjustment of the chemical composition and proportion of the organic co-monomers. The application potential of the optimized membranes in the lubricant dewaxing solvent recovery was evaluated using lubricant base oil derived from the actual production line, specifically light deasphalted oil and vacuum cut2. The membrane exhibited a rejection of 99.3 % for light deasphalted oil and 95.6 % for vacuum cut2, with corresponding fluxes of 16.8 and 13.4 LMH under 2 MPa, respectively. Based on this, spiral-wound membrane modules (1.8″ × 12″) were fabricated and their suitability for dewaxing solvent recovery was further validated. The fabrication of spiral-wound membrane modules (8″ × 40″) is in progress, with intentions to conduct a pilot plant trial on the lubricant oil manufacturing line.

قياس انبعاثات الجسيمات الصلبة وتوزيعها الناتجة من الوقود الحيوي في محرك التوربين الغازي المصغر

Atmospheric CO2 has been reported to be on a rapid increase in recent times mainly due to the rising consumption of fossil fuel for anthropogenic activities. Currently the situation is that of the 25% fossil fuel consumption by the transportation sector, aviation sector consumes about 13% of transport fuel consumption, which is the second biggest sector after road transportation. Therefore, the applications of biofuels have been increased in aviation. The aim of this work is to investigate and compare biodiesel and its blends with syntactic kerosene. The pollutants of particulate emissions and their size distributions were analyzed. Jet A1 and blends of Jet A1 and biodiesel in volume ratios of 90:10 (B10), 80:20 (B20), 70:30 (B30), 50:50 (B50) and 30:70 (B70) mixed with 2.5% turbine lubricating oil were tested. The fuels were tested at three load conditions (throttle settings): Full power, 70% and idle condition. Scanning Mobility Particle Sizer has been used to determine the particulate size distribution and the number of concentration of diluted exhaust gases. The results showed that particulates from all throttle settings showed uni-modal distribution characteristics. Particulate number concentration of each fuel increases with the increase in throttle position. The increase in biodiesel ratio in biodiesel blend has also increased the particulate size concentration. More particulates were seen to be produced with Jet A1 and lower blends of biodiesel. The engine also produces a significantly higher number of particles at full power for all fuel types. Keywords: Biodiesel, Micro Gas Turbine Engine, Scanning Mobility Particle Sizer, waste cooking oil, pollutants.

Lubrication Reliability and Oil Churning Loss of Differential Gear Trains in a Mechanical-Hydraulic Coupling Mechanism

A differential gear train (DGT) is a crucial component of a mechanical-hydraulic coupling mechanism. The transmission process generates oil churning losses, which significantly impact the overall transmission efficiency. Due to the complexity of DGTs and the unpredictability of lubrication reliability, traditional analysis of churning characteristics is inadequate. In this study, the moving particle semi-implicit (MPS) method is employed to analyze the effects of steady-state rotation speeds, dynamic rotation speeds, and oil filling heights on the oil churning characteristics of DGTs. The accuracy of the MPS method in predicting churning loss is illustrated by the average absolute percentage error of 6.4% obtained experimentally. It is concluded that: increasing the oil filling height improves lubrication reliability by 20.9%, but results in greater power loss. The lubrication reliability and power loss of DGTs with different output forms are mutually advantageous under different influencing factors. This paper helps to improve the lubrication reliability of DGTs.