Transient Equilibrium Research Articles

Diffuse interface modeling of non‐isothermal Stokes‐Darcy flow with immersed transmissibility conditions

AbstractThe coupling between free and porous medium flows has received significant attention since it plays an important role in a wide range of problems from fluid‐soil interactions to biofluid dynamics. However, modeling this coupled process remains a difficult task as it often involves a domain decomposition algorithm in conjunction with a special treatment at the interface. The problem can become more challenging under non‐isothermal conditions because it requires the iterative procedure at every time step to simultaneously meet the transient mass continuity, force equilibrium, and energy balance for the entire system. This article presents a diffuse interface framework for modeling non‐isothermal Stokes‐Darcy flow and the corresponding finite element formulation that bypasses the need for explicitly splitting the domain into two, which enables the unified treatment for distinct regions with different hydrothermal flow regimes. To achieve this goal, we employ the Allen‐Cahn type phase field model to generate the diffuse geometry, where the solution field can be seen as a regularized approximation of the Heaviside indicator function, allowing us to transfer the interface conditions into a set of immersed boundary conditions. Our formulation suggests that the isothermal operator splitting strategy can be adopted without compromising accuracy if the heat and mass transfer processes are decoupled by assuming that the density and viscosity of the phase constituents are independent to the temperature. Numerical examples are also introduced to verify the implementation and to demonstrate the model capacity.

An Experimental Investigation Of Local Thermo-Fluidic Heat Transfer In A U-Shaped Mini-Channel Sink

This study investigates experimentally a heated U-shaped mini-channel heat sink using Infrared Thermography and Particle Image Velocimetry for a water coolant flow of Reynolds numbers of 280, 650, and 1350 (based on the hydraulic channel diameter). The choice of this cell geometry is based on its role as a simplified unit of a serpentine heat exchanger, which is proved to be one of the most promising for cooling processes. The use of the infrared camera allows the detection of temperature fields on top of the external surface of the cell. Therefore, aiming to derive the temperature distribution on the channel roof, a dedicated transfer function is implemented. Moreover, we employed the lumped capacitance model for thermal analysis on both infrared measurements and thermocouple data. The latter are recorded to capture the cooling process of the aluminium base and water temperature at the end of the outlet tube. As a result, thermal transient rate, cooling magnitude and equilibrium temperature are obtained. These parameters indicate that higher Reynolds numbers correspond to increased thermal transient rates, enhanced cooling effects, and lower equilibrium temperatures. A non-uniform distribution of heat transfer along the channel is reported, with the most efficient cooling area localized close to the first 90-degree corner. These findings are consistent with numerical simulations and previous experimental observations. PIV results reveal the presence of two fluid acceleration zones following both 90-degree corners, which contribute to improve the water cooling ability in their respective regions. Additionally, the formation of two recirculating bubbles is reported at the inner wall from corners vertices, whose intensity is dependent on Reynolds number, pushing the main flow towards the outer channel wall and reducing the local heat transfer. Turbulent kinetic energy distributions are also investigated, pointing out the presence of intense areas that better match with regions of minimum equilibrium temperature than maximum velocity zones. This suggests the presence of local turbulent unsteadiness and three-dimensional phenomena, which contributes significantly to cooling enhancement.

A new integrated intelligent computing paradigm for predicting joints shear strength

Joints shear strength is a critical parameter during the design and construction of geotechnical engineering structures. The prevailing models mostly adopt the form of empirical functions, employing mathematical regression techniques to represent experimental data. As an alternative approach, this paper proposes a new integrated intelligent computing paradigm that aims to predict joints shear strength. Five metaheuristic optimization algorithms, including the chameleon swarm algorithm (CSA), slime mold algorithm, transient search optimization algorithm, equilibrium optimizer and social network search algorithm, were employed to enhance the performance of the multilayered perception (MLP) model. Efficiency comparisons were conducted between the proposed CSA-MLP model and twelve classical models, employing statistical indicators such as root mean square error (RMSE), correlation coefficient (R2), mean absolute error (MAE), and variance accounted for (VAF) to evaluate the performance of each model. The sensitivity analysis of parameters that impact joints shear strength was conducted. Finally, the feasibility and limitations of this study were discussed. The results revealed that, in comparison to other models, the CSA-MLP model exhibited the most appropriate performance in terms of R2 (0.88), RMSE (0.19), MAE (0.15), and VAF (90.32%) values. The result of sensitivity analysis showed that the normal stress and the joint roughness coefficient were the most critical factors influencing joints shear strength. This paper presented an efficacious attempt toward swift prediction of joints shear strength, thus avoiding the need for costly in-site and laboratory tests.

Three-Dimensional Visualization of Adsorption Distribution in a Single Crystalline Particle of a Metal-Organic Framework.

Many unique adsorption properties of metal-organic frameworks (MOFs) have been revealed by diffraction crystallography, visualizing their vacant and guest-loaded crystal structures at the molecular scale. However, it has been challenging to see the spatial distribution of the adsorption behaviors throughout a single MOF particle in a transient equilibrium state. Here, we report three-dimensional (3D) visualization of molecular adsorption behaviors in a single crystalline particle of a MOF by in situ X-ray absorption fine structure spectroscopy combined with computed tomography for the first time. The 3D maps of water-coordinated Co sites in a 100 μm-scale MOF-74-Co crystal were obtained with 1 μm spatial resolution under several water vapor pressures. Through the visualization of the water vapor adsorption process, 3D spectroimaging revealed the mechanism and spatial heterogeneity of guest adsorption inside a single particle of a crystalline MOF.

A physics-informed data-driven algorithm for ensemble forecast of complex turbulent systems

A new ensemble forecast algorithm, named the physics-informed data-driven algorithm with conditional Gaussian statistics (PIDD-CG), is developed to predict the probability density functions (PDFs) of complex turbulent systems with partial observations. The PIDD-CG algorithm integrates a unique multiscale statistical closure modeling strategy with a highly efficient nonlinear data assimilation scheme to create a mixture of conditional statistics. An effective data-driven modeling method is integrated with the dominant conditional statistics to serve as the forecast ensemble members that can significantly reduce the high computational cost of recovering high-dimensional PDFs. The multiscale features in the time evolution of these conditional statistics ensembles are effectively predicted by an appropriate combination of physics-informed analytic formulae and recurrent neural networks. An information metric is adopted as the loss function for the latter to more accurately capture the desirable turbulent features. The proposed algorithm displays effective forecasting performance in both the transient and statistical equilibrium non-Gaussian PDFs of strongly turbulent systems with intermittency, regime switching, and extreme events. It also facilitates the development of efficient statistical reduced-order models in recovering and predicting the large-scale coherent structures of a large group of multiscale complex systems.

Stability of sandy soils against internal erosion under cyclic loading and quantitatively examination of the composition and origin of eroded particles

Internal erosion refers to the movement of fine particles within soil framework due to subsurface water seepage. Existing criteria for assessing internal erosion usually are based on static loading, and the effect of cyclic load is not considered. Additionally, there are limited studies to examine the particle-size distribution and origin of eroded fine particles. This study presents an experimental investigation that examines the impact of cyclic loading on internal stability through a series of seepage tests. The composition and origin of lost particles are quantitatively studied using particle staining and image recognition techniques. With increasing hydraulic gradient, particle erosion progresses from top layer to bottom layer, with a gradual increase in the maximum particle size of eroded particles from each layer. After significant loss of particles, the specimens reach a state of transient equilibrium, resulting in a gradual slowdown of both particle loss rate and average flow velocity. The results indicate that cyclic loading promotes massive particle loss and causes erosion failure of specimens that are considered stable according to existing criteria. The reason is that under cyclic loading, local hydraulic gradients is oscillating, and a larger than average hydraulic gradient may occur, which is responsible for the internal instability. The analysis suggests that existing criteria can provide a reasonable assessment of the relative stabilities of specimens under static loads but fail to capture the stabilities under cyclic loading conditions.

Data-driven enhanced FDEM for simulating the rock mechanical behavior

In this paper, a data-driven enhanced combined finite-discrete element method (DDFDEM) is proposed to simulate the rock mechanical behavior by directly assigning the rock experimental data into mechanical simulations, thus bypassing the empirical constitutive model of rock. To achieve this, a novel data-driven iterative solver with transient dynamic system equilibrium constraint is first proposed and embedded into the FDEM computing framework. Then, the bonding force update algorithm for crack elements is improved to mitigate the error accumulation during the iteration process. After that, a recommended formation for the proper size of the experimental data set is proposed to balance the computational accuracy and efficiency of DDFDEM, and an efficient nearest neighbor search algorithm is introduced to significantly improve the computational efficiency of DDFDEM. After the above improvements, the computational accuracy and efficiency of DDFDEM in simulating the rock deformation and complex failure process are validated by conducting several examples, including the thin plate tension test, uniaxial compression test, and Brazilian disk test. Finally, the advantage of DDFDEM over conventional FDEM in comprehensively presenting the information hidden behind the experimental data sets is validated by reproducing the nonlinear mechanical behaviors of rock samples based on a data set following the nonlinear elastic material law.

Numerical study on transient response of transpiration cooling with hydrocarbon fuel as coolant

A transient non-thermal equilibrium model was established to solve the transient process of transpiration cooling, which considers the influence of cracking reaction. The occurrence of cracking reaction leads to the increase of inlet pressure, thermal diffusion coefficient and heat transfer coefficient and effectively reduces the temperature of porous matrix. In the absence of external oscillation excitation, the change rate of porous matrix temperature and fluid temperature with heating time gradually decreases. In the case of unsteady heat flux, the oscillation amplitude of fluid parameters near the outlet of porous media is larger. The increase of thermal conductivity of solid matrix can effectively restrain the temperature oscillation caused by external heat flux, but the amplitude of coolant supply pressure increases with the increase of thermal conductivity, which is not conducive to the supply of coolant. The amplitude of reaction heat is the smallest when the frequency of coolant mass flux and heat flux is the same. The greater inlet pressure oscillation is formed when the coolant supply cycle period is lower than the cycle period of heat flux.

Experimental investigation on evaporation characteristics of RP-3 aviation kerosene droplet above the critical temperature under various pressure conditions

The evaporation of aviation kerosene droplets in the aeroengine combustion chamber is one of the basic processes during liquid fuel combustion, which directly affects fuel atomization, air-fuel mixture formation and the combustion quality. However, the data are rarely reported due to the difficulty of conducting experiments in high temperature and pressure conditions. In this study, a series of experiments were carried out to investigate the evaporation characteristics of RP-3 aviation kerosene droplet. The environmental pressure and temperature of droplet evaporation ranged from 1 and 20 bar and 400 and 600°C respectively. An individual RP-3 kerosene droplet with initial diameter between 0.9 and 1.1 mm was suspended at a thermocouple bead with 50 μm diameter to measure droplet temperature. Droplet diameter during the whole evaporation process was recorded simultaneously by a high-speed camera. Experimental results indicated that at lower evaporation rate, RP-3 kerosene droplet evaporation experienced two processes: transient heating and equilibrium evaporation periods. While under high evaporation rates, the droplet only underwent equilibrium evaporation period without droplet expansion. At all the studied temperatures, droplet temperature kept increasing during the entire evaporation process without reaching a stable temperature. In most cases, the transient evaporation rate (K) of RP-3 kerosene droplet first increased rapidly until reaching the peak, and then followed by a monotonous decrease. However, at 20 bar above 500°C conditions, the temporal K curve exhibited a double-peak feature. Above the critical temperature of the fuel, increasing ambient pressure and temperature both can promote the heating and evaporation. However, the promotion of increasing ambient temperature to droplet evaporation was weakened at high ambient pressure. The quantitative correlations of droplet lifetime and evaporation rate constant with pressure were proposed under different ambient temperatures.

A Novel Numerical Method for Geothermal Reservoirs Embedded with Fracture Networks and Parameter Optimization for Power Generation

Geothermal recovery involves a coupled thermo-hydro-mechanical (THM) process in fractured rocks. A fluid transient equilibrium equation, considering thermal conduction, convection, and heat exchange, is established. The evolution of the reservoir permeability and the variance in the fracture aperture due to a change in the stress field are derived simultaneously. THM coupling is accomplished through iterative hydromechanical and thermo-hydro processes. To overcome the difficulty of geometric discretization, a three-dimensional THM coupler model embedded with discrete fracture networks, using a zero-thickness surface and line elements to simulate fractures and injection/production wells, is established to evaluate the geothermal production. The reliability of the method is verified by a case study. Then, this method is applied to evaluate the influence of the geometric topological characteristics of fracture networks and the fracture aperture on the reservoir temperature evolution and heat extraction effectiveness. The results show that the power generation efficiency and geothermal depletion rate are significantly affected by the injection–production pressure. Injection wells and production wells with pressures higher than the initial fluid pressure in the fractures can be used to significantly increase power generation, but the consumption of geothermal energy and loss of efficiency are significant and rapid. To achieve better benefits for the geothermal recovery system, an optimization algorithm based on simultaneous perturbation stochastic approximation (SPSA) is proposed; it takes the power generation efficiency as the objective function, and the corresponding program is developed using MATLAB to optimize the position and pressure values for each production well. The results show that the heat transfer for the entire EGS reservoir becomes more uniform after optimization, and the heat transfer efficiency is greatly improved.

Mechanistic Insight into Anion-Binding Catalytic Living Cationic Polymerization.

Exploiting non-covalent interactions to catalyze challenging ionic polymerizations is an ambitious goal but is in its infancy. We recently demonstrated non-covalent anion-binding catalysis as an effective methodology to enable living cationic polymerization (LCP) of vinyl ethers in an environmentally benign manner. Here, we further elucidate the structure-reactivity relationships of the elaborately designed seleno-cyclodiphosph(V)azanes catalysts and the roles of anion-binding interactions by a combined theoretical DFT study and experimental study. The investigation suggests that the distinct cis-cyclodiphosph(V)azane framework combined with "selenium effect" and electron-withdrawing 3,5-(CF3 )2 -Phenyl substitution pattern in catalyst enables a critical contribution to accessing excellent stability, anion affinity and solubility under polymerization conditions. Thus, the catalyst could leverage anion-binding interactions to precisely control reversible and transient dormant-active species equilibrium, allowing it to dynamically bind, recognize and pre-organize propagating ionic species and monomer, thereby facilitating efficient chain propagation and minimizing irreversible chain transfer events under mild conditions. The more in-depth understanding of the mechanism for anion-binding catalytic LCP reported herein should help to guide future catalyst design and to extend this concept to broader polymerization systems where ionic species serve as crucial intermediates.

Enhancing Heat Transfer Behaviour of Ethylene Glycol by the Introduction of Silicon Carbide Nanoparticles: An Experimental and Molecular Dynamics Simulation Study.

As the critical component of automotive engine coolant, ethylene glycol (E.G.) significantly matters in heat dissipation. In this study, the key aim is to investigate the heat transfer behaviour of E.G. as nano-additives base fluid. The heat transfer capability of E.G./SiC nanofluid (N.F.) was experimentally and theoretically evaluated via transient hot wire methods and equilibrium molecular dynamics (EMD) simulation, respectively. M.D. simulation exhibited a great ability to accurately forecast the thermal conductivity of N.F. compared with the experiment results. The results confirmed that the thermal stability of N.F. is relatively greater than that of E.G. base fluids. An improvement mechanism of thermal conductivity and thermal stability under an atomic scale via the analysis of mean square displacement (MSD) and radial distribution function (RDF) calculation was elaborately presented. Ultimately, the results indicated that the diffusion effect and the increasing transition rate of liquid atoms are responsible for thermal conductivity enhancement.

Dual targeting with 224Ra/212Pb-conjugates for targeted alpha therapy of disseminated cancers: A conceptual approach.

Metastases are the primary cause of death among cancer patients and efficacious new treatments are sorely needed. Targeted alpha-emitting radiopharmaceuticals that are highly cytotoxic may fulfill this critical need. The focus of this paper is to describe and explore a novel technology that may improve the therapeutic effect of targeted alpha therapy by combining two radionuclides from the same decay chain in the same solution. We hypothesize that the dual targeting solution containing bone-seeking 224Ra and cell-directed complexes of progeny 212Pb is a promising approach to treat metastatic cancers with bone and soft tissue lesions as well as skeletal metastases of mixed lytic/osteoblastic nature. A novel liquid 224Ra/212Pb-generator for rapid preparation of a dual targeting solution is described. Cancer cell targeting monoclonal antibodies, their fragments, synthetic proteins or peptides can all be radiolabeled with 212Pb in the 224Ra-solution in transient equilibrium with daughter nuclides. Thus, 224Ra targets stromal elements in sclerotic bone metastases and 212Pb-chelated-conjugate targets tumor cells of metastatic prostate cancer or osteosarcoma. The dual targeting solution may also be explored to treat metastatic breast cancer or multiple myeloma after manipulation of bone metastases to a more osteoblastic phenotype by the use of bisphosphonates, denosumab, bortezomib or hormone therapy prior to treatment. This may improve targeting of bone-seeking 224Ra and render an augmented radiation dose deposited within metastases. Our preliminary preclinical studies provide conceptual evidence that the dual 224Ra-solution with bone or tumor-targeted delivery of 212Pb has potential to inhibit cancer metastases without significant toxicity. In some settings, the use of a booster dose of purified 212Pb-conjugate alone could be required to elevate the effect of this tumor cell directed component, if needed, e.g., in a fractionated treatment regimen, where the dual targeting solution will act as maintenance treatment.

Transient equilibrium determination of dopamine D2/D3 receptor densities and affinities in brain.

Long-term alteration of dopaminergic neurotransmission is known to modulate the D2/D3 receptor expression in the brain. The modulation can occur as a response to pathological processes or pharmacological intervention. The receptor density can be monitored by in vivo positron emission tomography (PET) of [11C] raclopride. To obtain accurate measurements of receptor-ligand interaction, it is essential to estimate binding parameters at true (if transient) equilibrium of bound and unbound ligand quantities. We designed this study as a comparison of two quantitative approaches to transient equilibrium, the TRansient EquilibriuM BoLus Estimation (TREMBLE) method and the Transient Equilibrium Model (TEM) method, to determine binding parameters at transient equilibrium with bolus injection of the radioligand. The data demonstrates that TREMBLE unlike TEM identified the time at which equilibrium existed. TREMBLE revealed that equilibrium prevailed at one or more times after bolus injection and identified differences of receptor density among regions such as putamen and caudate nucleus. We demonstrated that TREMBLE is a quantitative approach suitable for the study of pathophysiological conditions of certain types of neurotransmission the brain.

Temporal epistasis inference from more than 3500000 SARS-CoV-2 genomic sequences.

We use direct coupling analysis (DCA) to determine epistatic interactions between loci of variability of the SARS-CoV-2 virus, segmenting genomes by month of sampling. We use full-length, high-quality genomes from the GISAID repository up to October 2021 for a total of over 3500000 genomes. We find that DCA terms are more stable over time than correlations but nevertheless change over time as mutations disappear from the global population or reach fixation. Correlations are enriched for phylogenetic effects, and in particularly statistical dependencies at short genomic distances, while DCA brings out links at longer genomic distance. We discuss the validity of a DCA analysis under these conditions in terms of a transient auasilinkage equilibrium state. We identify putative epistatic interaction mutations involving loci in spike.

A new Galerkin Reduction approach for the analysis of a fully coupled foil air bearing rotor system with bilinear foil model

The foil air bearing (FAB) is a key enabler of the rapidly expanding technology of oil-free turbomachinery. However, it presents a formidable computational challenge due to the intricacy of the mathematical modelling of the nonlinear interaction between the foil structure, air film, and rotor. Galerkin Reduction (GR) allows the integration of the compressible Reynolds Equation within a FAB-rotor model without the need for spatial discretisation, resulting in a considerable gain in computational efficiency relative to grid/mesh-based methods like Finite Difference (FD) and Finite Element (FE). GR has so far been limited to a simple model that ignores the detachment of the top foil from the underlying foil. A new GR approach is developed to overcome this limitation. Following transient and static equilibrium analyses of the nonlinear system, Jacobian-based linearization is used to extract the full mode set, Campbell diagram and linear stability map. The use of GR instead of FD reduced the computational time by over 50% and required 20-60 times less memory for saving the results, without compromising accuracy and reliability. In particular, Jacobian-based linearization using GR retains the ability to detect instabilities (like top foil flutter) that are beyond the capability of the traditional linear force coefficients method.

Hybrid absorbing scheme based on hyperelliptical layers with non-reflecting boundary conditions in scalar wave equations

Modeling unbounded or semi-infinite media with numerical methods, such as finite elements, requires avoiding that waves pass through the boundaries of the truncated computational domain without reflection. For this reason, in areas such as Geophysics or Acoustics, absorbing layers are used to circumvent this issue. Nevertheless, sizing them is an open problem due to the necessary calibration of their parameters for an adequate performance and to prevent numerical instabilities. Absorbing layers are dependent on both wave frequency and material properties set up inside them and, affect the convergence of iterative methods in inverse problems by the inherent variation of domain properties within the process, especially in the transient regime. On the other hand, hybrid absorbing boundary conditions are the combination of absorbing layers and the application of non-reflecting boundary conditions on the layer boundary with the purpose of increasing their effectiveness. In this work, an analytical approach is presented to size the portion added to the original domain and to determine its damping parameters simultaneously. Hyperelliptical absorbing layers are introduced and, for generating the hybrid absorbing boundary conditions scheme, Sommerfeld or 1st-Higdon boundary conditions are imposed on the outer layer boundary. Therefore, this methodology is adaptive according to the intermediate solutions of the transient optimization process for reducing possible numerical instabilities and spurious information for the inverse problem. The transient equilibrium equations are implemented by using the finite element method and an implicit time integration method. Results are presented to show the potential of the proposal.

Statistical thermodynamics in reversible clustering of gold nanoparticles. A first step towards nanocluster heat engines

A statistical thermodynamics variational criterion is propounded to study thermal hysteresis in reversible clustering of gold (Au) nanoparticles. Experimentally, a transient equilibrium mapping analysis is employed to characterize it thermodynamically, further measurements being performed at the nanostructural and electrochemical levels (UV-Vis-NIR spectra, SLS/SAXS, zeta potential). Theoretically, it is successfully interpreted as a thermodynamic cycle, prompting that nanoclusters has potential to produce useful work from heat and paving the way to nanoclustering heat engines. By taking into account the virial expansion of hysteretic pressure, an entropy measure is deduced for a dilute system with given virial coefficients. This allows us to figure out the role of relevant interparticle potential parameters (i.e. surface potential, nanoparticle size, Debye’s length, Hamaker energy) in both isothermal and isochoric variations at the onset of hysteresis. Application to spherical Au nanoparticles in watery salt solution (NaCl) is developed when an ad-hoc (DLVO) pairwise potential governs the second virial coefficient at the nanoscale. In particular, the variational criterion predicts a pressure drop between heating and cooling paths which is likely at the base of some energy redistribution (e.g. ordering/restructuring of electric double layers). We found an integrating factor that is able to numerically predict the existence of a critical value for the initial salt concentration maximizing the hysteretic area, and the effect of nanoparticle size on the cycle extent.

Evaporation Characteristics of Lubricant/Gasoline Blending Oil Film Under Different Thermal Radiations

Abstract The evaporation and pro-ignition characteristics of the lubricating oil blending in the cylinder can bring a super knock for the high-efficiency gasoline engine. The evaporation characteristics of the lubricant/gasoline blending oil film were investigated experimentally under different thermal radiative heat flux, film thickness, and carrier material in a radiation device. The blending ratios of lubricant/gasoline oil film changed from 0% to 15%. Three stages of the blending oil film evaporation process were observed according to the different evaporation rates, namely, transient heating, equilibrium evaporation, and evaporation gel. During the transient heating stage, with the increase of gasoline blending ratio, oil film thickness, and radiative heat flux, the evaporation rate increases, while the evaporation rate decreases in the equilibrium evaporation stage. The evaporation rates in transient heating stage and equilibrium evaporation stages are reasonably predicted by using the proposed relationship model.

A new shift mechanism for micro-explosion of water-diesel emulsion droplets at different ambient temperatures

Water emulsified diesel is an ideal new alternative fuel for diesel engines, which has great potentials in reducing NOx and PM emissions simultaneously. A thorough understanding of its evaporation process is critical for achieving the emission reduction potentials. Therefore, this study investigated the evaporation characteristics of emulsion droplets with 65% diesel, 30% water and 5% surfactant by mass using the droplet suspension technology at ambient temperature 573–873 K. The normalized squared diameter, micro-explosion frequency, micro-explosion intensity and expansion intensity were used to quantify the effect of ambient temperature on the evaporation characteristics. The results showed that the evaporation process of water emulsified diesel droplets mainly included three stages, namely transient heating, fluctuation evaporation, and equilibrium evaporation. The maximum normalized squared diameter first increased with ambient temperature and then decreased, leading to a maximum of 2.91 at 773 K. The micro-explosion frequency first decreased and then increased, which was consistent with that of micro-explosion intensity. In addition, this study innovatively correlated the internal relationship between bubble formation and micro-explosion. Based on this, a new micro-explosion shift mechanism of water emulsified diesel droplets was proposed. As the ambient temperature increased, bubble nucleation in the droplet gradually changed from single site to multiple sites, and the nucleation sites shifted from the droplet center to surface.