High-pressure Combustion Research Articles

Effect of the leak port area and tube length on suppression of spontaneous ignition of high-pressure hydrogen

Suppression of high-pressure hydrogen spontaneous combustion is essential for the sustainable development of hydrogen energy. Previous studies have shown that suppressing hydrogen spontaneous combustion by reducing the area of the leak port is a feasible method. However, the effect of some factors, such as tube length, on this suppression method has not received attention. Therefore, the effect of leakage port areas of 10 mm, 8 mm, 6.6 mm, and 4.5 mm on the suppression of hydrogen spontaneous combustion was investigated experimentally and simulated for different pipe lengths. The results show that reducing the leak port area increases the hydrogen-air mixing path, which raises the combustible concentration. However, by reducing the leak port area, the intensity of shock waves and the maximum temperature in the tube decreased significantly, and the possibility of hydrogen spontaneous combustion decreased. This indicates that reducing the leak port area can inhibit hydrogen spontaneous combustion. In addition, within a certain leak area, increasing the tube length weakens the performance of this inhibition method. However, the effect of tube length on this method disappears as the leak area decreases. Finally, the leakage port area is reduced, changing the flow field at the nozzle, so that the spontaneous combustion flame in the near field of the nozzle undergoes extinguishment and re-ignition. The results show that reducing the area of the leakage port can effectively inhibit hydrogen self-ignition and is not affected by the length of the tube, providing a way to inhibit hydrogen self-ignition.

The Effects of Cracking Ratio on Ammonia/Air Non-Premixed Flames under High-Pressure Conditions Using Large Eddy Simulations

Ammonia is a promising carbon-free fuel. However, one of the main challenges for ammonia combustion is the high level of NO emissions. In this study, simulations were conducted for ammonia/air laminar counterflow flames and turbulent non-premixed jet flames in the KAUST high-pressure combustion duct (HPCD) at a pressure of 5 bar, with two ammonia cracking ratios of 14% and 28%. The influence of ammonia cracking ratio on the flame structure and NO formation mechanism were examined. The laminar counterflow flame results showed that HNO is one of the most critical species related to NO formation and NO is mainly generated through the path of NH2→NH→HNO→NO. For the turbulent flames, the flamelet/progress variable (FPV) approach was employed in the context of large eddy simulations (LES) for high-fidelity simulations. The simulation results were compared with the measured data with promising agreements, which proves the accuracy of the FPV method for the present flames. It was shown that with increasing cracking ratio, not only the flame reactivity is enhanced, but also the generation of NO is increased. The correlation between NO and HNO is weaker when compared to that between NO and radicals such as O, H and OH in the entire flame. Through the distribution of NO source terms, it was found that the NO source term has a higher absolute value in the upstream region and the absolute value rapidly decreases with increasing streamwise distance. The total NO source term is positive in the fuel-lean zone and shows negative values in the fuel-rich zone.

The regulation of ferrocene-based catalysts on heat transfer in high-pressure combustion of ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum composite propellants

The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum (AP/HTPB/Al) composite propellants under high pressures is a crucial step for its application in high-pressure solid rocket motors. In this work, the combustion characteristics of AP/HTPB/Al composite propellants containing ferrocene-based catalysts were investigated, including the burning rate, thermal behavior, the local heat transfer, and temperature profile in the range of 7–28 MPa. The results showed that the exponent breaks were still observed in the propellants after the addition of positive catalysts (Ce-Fc-MOF), the burning rate inhibitor ((Ferrocenylmethyl)trimethylammonium bromide, FcBr) and the mixture of FcBr/catocene (GFP). However, the characteristic pressure has increased, and the exponent decreased from 1.14 to 0.66, 0.55, and 0.48 when the addition of Ce-Fc-MOF, FcBr and FcBr/GFP in the propellants. In addition, the temperature in the first decomposition stage was increased by 7.50 °C and 11.40 °C for the AP/FcBr mixture and the AP/FcBr/GFP mixture, respectively, compared to the pure AP. On the other hand, the temperature in the second decomposition stage decreased by 48.30 °C and 81.70 °C for AP/FcBr and AP/FcBr/GFP mixtures, respectively. It was also found that FcBr might generate ammonia to cover the AP surface. In this case, a reaction between the methyl in FcBr and perchloric acid caused more ammonia to appear at the AP surface, resulting in the suppression of ammonia desorption. In addition, the coarse AP particles on the quenched surface were of a concave shape relative to the binder matrix under low and high pressures when the catalysts were added. In the process, the decline at the AP/HTPB interface was only exhibited in the propellant with the addition of Ce-Fc-MOF. The ratio of the gas-phase temperature gradient of the propellants containing catalysts was reduced significantly below and above the characteristic pressure, rather than 3.6 times of the difference in the blank propellant. Overall, the obtained results demonstrated that the pressure exponent could be effectively regulated and controlled by adjusting the propellant local heat and mass transfer under high and low pressures.

Fuel Consumption Rate Optimization Analysis of Dual-fuel Marine Diesel Engines Based on Orthogonal Design

To investigate the influence of diesel engine operating matching parameters on the comprehensive fuel consumption rate of butanol-diesel dual-fuel engines, a high-pressure combustion chamber cycle model of a 4190ZLC-2 marine medium-speed diesel engine was established using AVL-FIRE simulation software. After establishing the optimum blending ratio of butanol, the fuel system parameters were optimized using a one-time regression orthogonal experimental design method, and a mathematical model for fuel consumption rate prediction was constructed to find the combination of parameters with the lowest fuel consumption rate as the target. The study shows that inlet pressure has the greatest influence on the fuel consumption rate, followed by EGR and inlet air temperature. The lowest fuel consumption rate was achieved by combining the following parameters: (butanol blending ratio of 20%, EGR rate 0, inlet pressure 0.233 MPa, inlet temperature 325.15 K, Injection advance angle 22.6 °CA, the diameter of oil injection hole (0.26 mm); after optimization, the fuel consumption rate was reduced by 9.96% compared to the original machine.

Mapping the research on the spontaneous combustion of high-pressure hydrogen leakage: A bibliometric analysis

Energy transition is a hot topic in the international arena today, and hydrogen energy is the focus of attention. Scholars have conducted a lot of research and formed a huge theoretical system. However, there are few systematic reviews of this field. To master the research and application status in high-pressure hydrogen leakage spontaneous combustion, revealing the research knowledge base and hot trends. We applied bibliometrics to the study and used 768 pieces of literature from 2000 to 2022 in the Web of Science core database as data samples. VOSviewer and CiteSpace were utilized for co-occurrence, keyword cluster, and co-citation analysis, as well as a bibliometric mapping analysis. The study found that the knowledge basis of the field is mainly the numerical simulation and kinetic studies of hydrogen combustion, the research on hydrogen energy carriers. As well as the research on the spontaneous combustion behavior of pressurized hydrogen leaks. Combustion and Flame, International Journal of Hydrogen Energy, and Fuel are core journals of the field. The current research includes four main hot spots: hydrogen's production and storage, the research on high-pressure hydrogen spontaneous combustion behavior. And the combustion characteristics of mixed combustible gases such as hydrogen and methane, the flame propagation characteristics of high-pressure hydrogen spontaneous combustion. The transition mechanism research of spontaneous combustion to jet fire is at the forefront of this research. Therefore, the results of this study identify the core journals, knowledge base, and research frontiers in the field. It enables readers to acquaint the status and trends of research in the area and can guide future research.

Assessment of the interchangeability of coal-biomass syngas with natural gas for atmospheric burners and high-pressure combustion applications

Assessment of the interchangeability of coal-biomass syngas with natural gas for atmospheric burners and high-pressure combustion applications

Effect of injection strategy on an air-assisted direct injection aviation kerosene two-stroke engine

In small aviation piston engines, the atomization and combustion of aviation kerosene have attracted much attention. Due to the low volatility and high viscosity of aviation kerosene, high-pressure injection or air-assisted injection is used to improve the fuel atomization quality. Considering the weight, cost and power consumption, air-assisted injection is more appropriate for compact, small aviation piston engines. In the paper, computational fluid dynamics (CFD) software was used to simulate the air-assisted spray and spark ignition combustion of aviation kerosene in a heavy-fuel direct injection spark ignition (DISI) two-stroke engine based on air-assisted direct injection (AADI) technology. The effects of injection pressure, single and double injection on formation and combustion characteristics of the aviation kerosene/air mixture were analyzed. The results show that increasing the air-assisted injection pressure can promote air flow in the cylinder and accelerate fuel evaporation, but also increase the film mass on the combustion chamber wall. When single injection is employed, high combustion pressure and temperature are generated, and the tendency to knocking combustion is greater. The use of double injection can effectively achieve fuel stratification and reduce knock tendency. With the delay of the second mixture injection timing, the peak combustion pressure is reduced, the heat release rate is slowed down, and the knock tendency is reduced correspondingly.

Laser-induced breakdown spectroscopy using modulated ns-laser pulses for multi-property measurements in high-pressure combustion environments

The present work proposes a novel method to improve the calibration accuracy of laser-induced breakdown spectroscopy (LIBS) in high-pressure combustion environments. Typically, optical plasma breakdown suffers from instability in highly pressurized environments, and the plasma emits photons of noisy and broadened spectra that are unusable for extracting quantitative property information. An improved plasma emission spectrum signal is obtained by modulating or chopping the pulse width of a fundamental 10 Hz Nd:YAG laser pulse by limiting the stochastic inverse-Bremsstrahlung (IB) photon absorption process. The modulated pulse duration is decreased from 9.2 ns to 5 ns utilizing a simple optical setup prior to being focused into a high-pressure combustor. In order to evaluate the impact of the modulated temporal laser pulse profile on the plasma emission, Proper Orthogonal Decomposition (POD) is applied to the emission spectra collected over a customized flat flame burner with varied composition and pressure. POD is capable of decomposing property-sensitive spectrum components that determine the accuracy of the spectrum calibration for property measurements using LIBS. The POD-analyzed database comprises 50 flame cases with pressure and equivalence ratios ranging from 1 to 10 bars and 0.7 to 1.1, respectively. Two Reduced-Order Models (ROMs) are trained with the collected spectra; modulated and original pulse, to predict three distinct flame properties; pressure, equivalence ratio, and adiabatic flame temperature. The output model estimates pressure, equivalence ratio and adiabatic flame temperature with an improved accuracy of 8%, 7% and 55%, respectively when the ROM is trained with chopped spectra over the calibrated pressure range. This is because the reduced pulse width in general lowers the signal level of broadband plasma emission that is sensitive to pressure. The POD-aided spectrum analyses suggest that flexible pulse modulation helps to improve the calibration accuracy in a broad gas density range with varied pressure and temperature.

Assessing requirements for modeling radiation in diffusion flames using an analytical, non-local model

An analytical approach for the calculation of radiative self-absorption in flames is presented, with the objective of providing an effective and computationally inexpensive tool for selecting radiation modeling methods for combustion applications. This one-dimensional non-local model approximates the flame structure as an infinitely long cylinder where all properties vary only along the radial direction. Flamelet solutions are then mapped to the radial direction and the radiative source terms, in particular the absorption, are computed analytically. The model is validated for a laminar jet flame and a turbulent pool fire, with results for the net radiative loss and the flame self-absorption showing good agreement to those of multidimensional, coupled simulations. To illustrate its applicability, the model is employed to study the characteristics of radiation in high-pressure combustion, in fire suppression and in hydrogen combustion. For the pressurized case, increased significance of radiation self-absorption is observed compared to an atmospheric flame, and accounting for the non-gray nature of radiation is found to be critical. In the fire suppression case, comparisons of the S-curves show that the choice of radiation model modifies the lower extinction limit, which becomes more important with reduced oxygen content. Lastly, for the hydrogen flame, the Planck-mean absorption coefficient is found to be more uniformly distributed in the mixture fraction space, and the optical thickness is smaller than a hydrocarbon flame at comparable conditions, indicating that radiation modeling requirements for that flame are likely less stringent. In general, the findings regarding radiation characteristics made on the basis of the non-local model are consistent with observations reported in the literature, but without the need for complex coupled combustion-radiation calculations. Therefore, the model provides a viable approach for selecting appropriate radiation models in combustion simulations.

Experimental and numerical investigation of aluminum particle combustion driven instability in solid rocket motors

Aluminum particles are extensively employed to enhance the energetic properties of propellants. However, the heat release rate (HRR) fluctuations resulting from aluminum combustion can potentially affect the stability of solid rocket motors (SRMs). Using a self-made high-pressure combustion diagnostics system and laser ignition system, this work investigates the combustion behavior of single aluminum particle under propellant atmosphere and acoustic excitation. An unsteady aluminum combustion model using Ranz-Marshall correlation and involving the heat and mass transfer equation was developed. The D2 law of aluminum particle combustion in a real propellant under 0.5 MPa was fitted as t = D2/0.31. The measured combustion rate of laser-ignited aluminum particles was found to increase from 0.381mm2/s to 0.465 mm2/s when an acoustic excitation of sine wave(200 Hz, 20Pa) was applied to the propellant, which agreed well with the prediction of the proposed unsteady combustion model whose error was 4.7%. Then, the verified correlation was included in the SRM to calculate the HRR fluctuation of the aluminum on acoustic boundary near the propellant burning surface. The effects of particle diameter, gas velocity, oscillation amplitude and frequency on the HRR fluctuation were obtained. It was found that the HRR fluctuation increases with the increasing particle diameter, gas velocity, and oscillation amplitude, and that due to the acoustic boundary effect, the HRR fluctuation is more sensitive under low-frequency oscillation. Based on the HRR fluctuation of aluminum combustion and particle damping, the growth rate of instability resulting from aluminum combustion in an SRM was investigated. The results showed that the growth rate of instability resulting from aluminum combustion were 9.38s-1 and 24.06s-1, while the particle damping (−25.8s-1) caused by combustion residuals, which suggests the aluminum particles play a critical role in SRMs combustion instability.

Numerical investigation of hydrogen addition effects to a methane-fueled high-pressure combustion chamber

To get a general understanding of hydrogen fuel usage in a real-condition high-pressure industrial gas turbine burner operating at 15 atm pressure, the effects of hydrogen addition to methane fuel are studied numerically. Methane-hydrogen premixed fuel-lean flame is investigated while hydrogen is substituted for methane at a fixed fuel and air mass flow rate at the burner inlet. Steady-state reacting and swirling flow equations (RANS) are solved using the standard k−ε model as the turbulence model. A detailed methane combustion mechanism GRI 2.11 is used to simulate methane-hydrogen combustion with Finite Rate formulation more accurately. Temperature and axial velocity variation and important pollutant species emissions such as CO, CO2, and NOx were investigated at the combustion chamber exit. Flame shape, flow pattern, and flame location variation with hydrogen addition were studied due to hydrogen flashback limits. The hydrogen addition leads to higher temperatures inside the burner and the hot zone inside the combustion chamber extends and moves toward the fuel inlet. Flow structure including recirculation zones change with hydrogen addition. CO emission increases by hydrogen addition to the fuel mixture near the burner exit while CO2 mass fraction is reduced. A significant increase in NO mass fraction with hydrogen addition was observed near the burner exit due to higher temperature.

Study on the effect of injection temperature and nozzle geometry on the flashing transition of liquid ammonia spray

Ammonia is a promising alternative fuel for carbon emission reduction in industry, transport, and power generation. For high-pressure combustion environment applications, direct injection of liquid ammonia (LNH3) is considered. Because of its thermophysical properties, and dependence on the injection and combustion environment conditions, the direct injection of ammonia in its liquid state can lead to flash-boiling, changing drastically the spray characteristics. In this study, we characterized the effect of injection temperature and nozzle geometry on the spray characteristics and transition to flashing using backlit imaging. Flow rates pressure curves and spray angles were obtained in a well-controlled environment and can be used as a database for simulation. Finally, some practical considerations on the design of nozzles are highlighted in the present work.

Rocket-augmented flame stabilization and combustion in a cavity-based scramjet

The scramjet engine has become an important propulsion system in hypersonic vehicles for its high specific impulse, but it also has obvious shortcomings, such as narrow reliable operating and thrust adjustment range, and consequently, insufficient maneuverability. To solve these problems, a rocket is introduced into the scramjet to improve the thrust performance while stabilizing flame and enhancing combustion, referring to the operating principle of the RBCC engine. The function mechanism of the high mass flow rate rocket jet on the flame stability and combustion characteristics in a cavity-based scramjet combustor is investigated through the ground direct-connect test. The experimental results show that: 1) Effective secondary fuel combustion enhancement and thrust enhancement can be obtained through the rocket augmentation. The embedded rocket leads to a 69% increase in the peak combustion pressure. 2) In the rocket-augmented combustion mode, the core combustion zone concentrates in the central region of the flow passage and simultaneously expands upstream, resulting from the increased mixing efficiency of kerosene/air and a more stable flame, which effectively augments the combustion and the engine thrust. 3) As the kerosene injection positions move upstream to the exit of the rocket nozzle, the secondary combustion efficiency can be further improved by inhibiting the negative effects of oxygen consumption by the fuel-rich rocket jet. The length of the high combustion pressure region is increased by 150%, and the scramjet performance has been enhanced significantly. 4) During the process of the kerosene injection position transition, the flame in the combustor keeps sustained under the function of the embedded rocket jet, and the rocket-augmented combustion exhibits favorable robustness.

RETRACTED: Assessing methanol potential as a cleaner marine fuel: An analysis of its implications on emissions and regulation compliance

This article aims to fill a gap in existing studies by examining methanol's prospects as a cleaner marine vessel fuel and addressing the industry's challenges in reducing pollution from ship oil. The analysis focuses on methanol as a decarbonization fuel option, following its advantages compared to others through data triangulation that uses both bottom-up and top-down approaches to examine the safety concerns and environmental impacts of methanol. The findings support its use as a promising alternative to conventional marine fuels, considering regulations and safety codes related to low-flashpoint fuels and specifying key safety measures. Also, container vessels (6% of the global fleet) consume 23% of all annual bunker volume and require nearly two-thirds of the global bunker demand, along with liquid bulk tankers and dry bulk carriers. These findings, along with the current regulatory landscape and infrastructure requirements for methanol fuel distribution, pose the greatest challenges to its widespread adoption, despite successes by MAN and Wärtsilä engine manufacturers in offering high-pressure diesel combustion technology engines for burning methanol. This study provides insights that can help ASEAN adopt methanol fuel while complying with emission standards and reducing its environmental impacts.

Large eddy simulations of ammonia-hydrogen jet flames at elevated pressure using principal component analysis and deep neural networks

The combustion of ammonia/hydrogen is currently gaining importance in the power generation sector as an alternative for hydrocarbon fuels and improved fundamental insights will facilitate its application. To investigate the complex interactions between turbulence and chemistry for ammonia-hydrogen jet flames under high-pressure conditions, large eddy simulation (LES) computations are conducted using the PC-transport model, which is based on Principal Component Analysis (PCA), coupled with nonlinear regression that utilizes deep neural networks (DNN) to enhance the size-reduction potential of PCA. Classical statistics-based nonlinear regression methods are inefficient at fitting highly nonlinear manifolds and when large data sets are involved. These two drawbacks can be overcome by utilizing DNN tools. Several DNN architectures composed of fully connected layers of different depths and widths, batch normalization, and various activation functions coupled with various loss functions (mean squared error, absolute error, and R2) are explored to find an optimal fit to the thermo-chemical state-space manifold. The ability to achieve highly accurate mapping through DNN-based nonlinear regression with an R2-score >0.99 is shown by employing a single graphical processing unit (Nvidia RTX 3090). Furthermore, the proposed PC-DNN approach is extended to include differential diffusion based on a rotation technique and utilization of the mixture-averaged transport model for the training data set. To demonstrate the potential of the PC-DNN approach in modeling turbulent non-premixed combustion, LES results are compared with the recent Raman/Rayleigh scattering measurements that were obtained at the KAUST high-pressure combustion duct (HPCD). Results show that the PC-DNN approach is able to capture key flame characteristics with reasonable accuracy using only two principal components. The inclusion of differential diffusion leads to improved predictions, although some discrepancies are observed in fuel-lean regions.

Effect of Aluminum Content on the Combustion Performance of HTPB/AP/Al Propellants under High Combustion Pressure

Effect of Aluminum Content on the Combustion Performance of HTPB/AP/Al Propellants under High Combustion Pressure

Tuning the micro‐structure, laser ignition, and isovolumetric burning performance of nitrocellulose propellant via incorporation of graphene oxide

AbstractNanoscale recombination between carbon nanomaterials (CNs) and polymers has been proposed for a variety of industrial and scientific applications. Composite energetic materials consisting of CNs with novel laser ignition property and tunable combustion performance have attracted people's attention. Here, reported is the novel manufacturing process of uniform nitrocellulose (NC)/graphene oxide (GO) nanocomposite propellant and the micro‐structure, laser ignition and isovolumetric burning features of the propellants introduced by GO. The results of microstructure tests indicated that GO (0.25–2 wt%) was stripped and dispersed homogeneously and dense nanocomposite propellants were prepared successfully through water ultrasonic dispersion, twin‐screw mixture, as well as compression molding. The crystallization of NC was forbidden by doping GO, meanwhile, the thermal stability and thermal conductivity of the composite propellants increased slightly with the addition of GO. The results of laser ignition combustion experiments showed that GO was an efficient additive to shorten the ignition delay time from more than 2000–14 ms when 2 wt% of GO was doped, however, the combustion flame intensity was also weakened due to the addition of GO. The combustion tests in a closed bomb vessel were conducted, and the results showed that GO would not affect the stable combustion of NC at high combustion pressure, moreover, the burning rate and dynamic vivacity of the composite propellants decreased with the increase of GO content.

A compact LWIR borescope sensor for 2D engine component surface temperature measurement

A compact long-wavelength infrared (LWIR) borescope imaging sensor operating in the wavelength range of 8–14 μm is designed and developed for non-contact two-dimensional (2D) surface temperature measurements in gas-turbine engines. The LWIR detection minimizes optical interferences from hot combustion gases and soot (emission within UV–mid IR region). Using simulations, the system is optimized for improving the signal collection efficiency and minimize image aberrations. The LWIR borescope probe is shielded by the custom-build compact water-cooled probe housing (outer diamter (OD) 19 mm, inner diameter (ID) 10 mm), which can sustain flame temperature up to 2400 K at a pressure of 50 bar. It facilitates long-term optical diagnostics inside the actual high-pressure combustion facilities where extreme thermal acoustic perturbation and intense heat fluxes are encountered. The design, construction, and characterization of the LWIR borescope sensor are discussed in detail. We present the 2D surface temperature measurements of a V-gutter bluff-body with simple nitrogen gas cooling in a laboratory testbed. The results indicate the sensor’s ability to accurately measure surface temperature with low background noise and to track transient cooling effect. The water-cooled probe housing was tested to verify the effectiveness of fast heat dissipation in high-temperature combustion environment to avoid unwanted thermal signals from the LWIR probe window. The developed LWIR sensor suite has promising applications in surface temperature measurements of engine components. The findings of this study may aid propulsion system engineers and researchers in designing thermal management systems and optimizing operation.

CFD-Based Prediction of Combustion Dynamics and Nonlinear Flame Transfer Functions for a Swirl-Stabilized High-Pressure Combustor

Thermoacoustic instabilities in gasturbine combustor systems can be predicted in the design phase with a thermoacoustic network model. In this model, the coupling between acoustic pressure fluctuations and the combustion rate is described by the Flame Transfer Function. The present paper introduces a new, efficient, and robust method for deriving the FTF from CFD predictions by means of a discrete multi-frequency sinusoidal fuel flow excitation method. The CFD-based FTF result compares well with experimental data for the time delay, but for the gain, only up to 400 Hz. Above 400 Hz, the CFD result reveals a smooth low-amplitude gain, which is not found in the measured data. A novel, accurate continuous correlation function for the FTF gain is computed based on the results for discrete frequencies. When this is implemented into a 1D acoustic network model, the stability map shows, below 600 Hz, two eigenfrequencies, by both the experiment and CFD-based FTF, that are identical. The CFD-based FTF correctly predicts marginal activity at the highest eigenfrequency, while the experimentally based FTF suggests an unstable operation. The unstable operation is not observed in the experiments. This suggests that the CFD-based FTF is also correct for high frequencies.

Explosion Mechanism of Lubricating Oil Droplets in High-Temperature and High-Pressure Combustion Environments

Lubricating oil-induced pre-ignition is a critical issue that requires attention in downsized gasoline engines and marine low-speed two-stroke natural gas engines. As a result, the ignition behavior of lubricating oil at high temperatures and pressures has been extensively studied. In some cases, when studying the ignition of oil droplets using a rapid compression machine, an explosion-like behavior of the oil droplets is observed, producing a soot cloud that can spread throughout the combustion chamber, especially when the ignition delay time of the ambient gas is short. To gain detailed insights into the mechanism of oil droplet explosion, the explosion process under initial pressures from 13 to 31 bar and temperatures from 700 to 1600 K was visualized using high-speed photography and microphotography on a rapid compression machine. The effects of temperature and shock waves were experimentally investigated, and droplet deformation after shock wave impact was calculated using a simple model. The results demonstrated that high temperature does not have a significant effect on droplet explosion under the conditions studied in this paper. The shock wave impact is the primary cause of the droplet’s explosion.