Deqing Mei

The catalytic influence of CeO 2 nanoparticles on diesel combustion was investigated through detailed kinetic modeling. A diesel surrogate consisting of n - dodecane ( NC 12 H 26 ) and p-xylene ( C 8 H 10 ) was adopted to represent the major chemical characteristics of real diesel fuel. A catalytic reaction mechanism describing the redox behavior of cerium dioxide ( CeO 2 ) was incorporated into the base fuel mechanism to construct a simplified kinetic framework for CeO 2 nanofuels. Combustion simulations were performed under various initial temperatures and pressures to evaluate the influence of CeO 2 nanoparticles on ignition behavior and combustion reactivity. The results indicate that the addition of CeO 2 significantly promotes the formation of OH and H 2 O 2 radicals at relatively low temperatures, leading to shorter ignition delay and enhanced heat release rates. At higher temperatures, combustion is dominated by rapid thermal decomposition of fuel molecules, which reduces the dependence of the system on catalytic radical generation and weakens the catalytic influence of CeO 2 . Furthermore, CeO 2 nanoparticles accelerate hydrocarbon oxidation and CO conversion while also enhancing nitrogen oxides ( NO x ) reduction reactions. Reaction pathway analysis shows that the primary oxidation pathways of the base fuel remain unchanged, whereas the catalytic reactions mainly affect radical formation and intermediate oxidation processes. These findings provide insight into the catalytic combustion mechanism of CeO 2 nanofuels and their potential for improving diesel combustion performance.

Considering the complementary fuel properties between biodiesel and ethanol, biodiesel–ethanol renewable fuels with different blending ratios were formulated. Under various operating conditions, the effects of different blending ratios of renewable fuels on combustion and emission performances were experimentally investigated. Results showed that equivalent specific fuel consumption (ESFC) was highly sensitive to operating conditions: fuel economy was inferior to diesel under low and medium loads but superior under high loads. Under 50% load, ethanol's cooling effect reduced in-cylinder temperature and delayed combustion, lowering indicated mean effective pressure (IMEP); under 100% load, ethanol's higher volatility improved fuel-air mixing, accelerating combustion and increasing IMEP. Emissions were governed by load-dependent thermal conditions and fuels' oxygenated nature: low and medium loads saw ethanol's high latent heat create a low-temperature environment, suppressing nitrogen oxides (NOx) but increasing hydrocarbon (HC) and carbon monoxide (CO); high loads enhanced combustion via oxygen, slightly raising NOx but significantly reducing HC and CO. Machine learning evaluation indicated that the artificial neural network (ANN) and support vector machine (SVM) performed best for ESFC prediction; SVM and multiple linear regression were most effective for IMEP; and ANN yielded the best results for NOx prediction. This study provides a theoretical basis and practical support for the intelligent prediction and optimization of renewable fuel combustion performance.

A multi-component blend of highly volatile ethanol with low volatile hydrogenated biodiesel and diesel is the subject of study. The internal vapor bubble dynamics and evaporation characteristics of individual droplets at high temperatures were investigated. The evaporation characteristics of droplet normalized square diameter and droplet lifetime of the blends of hydrogenated biodiesel, ethanol, and diesel were captured by means of the hanging droplet method and high-speed microscopic imaging in a constant temperature heating furnace. It is revealed that the rise in ambient temperature contributes to increasing the evaporation rate of fuel droplets and intensifies the micro explosion during evaporation and shortens the evaporation of droplets to a certain extent; Compared to diesel, the inhibition effect of evaporation is stronger with the increase of hydrogenated biodiesel in binary fuels and compared with binary fuels, ethanol in ternary fuels promotes micro explosions and shortens droplet evaporation; The droplet evaporation of binary fuels shows three typical phases of ethanol domination, ethanol, and diesel co-domination and co-evaporation of all three in sequence.

Prefilming air-blast atomizers are widely used in modern gas turbine combustors. Due to insufficient awareness of the coupling mechanism of multi-stage swirling flow in gas turbines, there is a lack of effective methods for flow field optimization in combustor. In this study, the effect of some critical parameters on the flow field of a prefilming air-blast atomizer was analyzed with CFD. The parameters include the angle and number of the first swirler blades, the angle of the second swirler blades and the angle of sleeve. Furthermore, the coupling mechanism of two-stage swirling airflows of prefilming air-blast atomizer was discussed. Moreover, the influence of the interaction between two-stage counter swirling airflows on the characteristics of flow field was explained. The results show that with the increase in SN_i, the axial length of the primary recirculation zone decreased, while the radial width increased. The starting position of primary recirculation zone (PRZ) moves forward with the increase in SN_o. Reducing the sleeve angle β helps to form the primary recirculation zone. The results indicate that it is the transition of tangential velocity of airflow to radial velocity that promotes the formation of the PRZ. These results provide theoretical support for optimization of the flow field in swirl combustor.