A comprehensive understanding of the combustion chemistry of methyl tert‑butyl ether (MTBE) is of key importance in its application as an additive in gasoline fuels. Ignition delay times (IDTs) of MTBE/air mixtures have been measured in both a high-pressure shock tube (HPST) and in a rapid compression machine (RCM) at equivalence ratios of 0.5, 1.0, and 2.0 in air, at pressures of 10 and 30 bar over the temperature range 600 – 1350 K. Species profiles for MTBE oxidation were obtained in a jet-stirred reactor (JSR) at 1 bar, at equivalence ratios of 0.5, 1.0, and 2.0 in the temperature range 700 – 1100 K.

A detailed reaction mechanism, comprising 813 species and 4319 reactions, has been developed and predicts well all of the experimental data obtained in this work and also texisitng literature data. Pressure- and temperature-dependent rate constants for the MTBE unimolecular elimination reaction producing isobutene and methanol were calculated using high-level ab-initio calculations. A sensitivity analysis reveals that this elimination reaction is important, and significantly inhibits fuel reactivity at temperatures above 1300 K. At intermediate temperatures (850 – 1300 K), the reaction MTBE + ȮH = TĊ₄H₈OCH₃ + H₂O plays a crucial role in promoting the reactivity of MTBE oxidation, whereas the reaction MTBE + ȮH = TC₄H₉OĊH₂ + H₂O is the most inhibiting reaction. At low temperatures (600 – 850 K), the isomerization reaction of TC₄OCȮ₂–1 ⇌ TĊ₄OCO₂H-2 significantly promotes the reactivity. Conversely, the reaction 2TC₄OCȮ₂–1 ↔ 2TC₄OCȮ-1 + O₂ inhibits reactivity the most. The NTC behavior in MTBE oxidation can be explained by the competition between the reactions involving the formation and consumption of cyclic ethers from TĊ₄H₈OCH₃ radicals and the reactions associated with the formation and consumption of carbonyl hydroperoxide species.

Exhaust gas recirculation (EGR) and NO_x affect the autoignition of gasoline in internal combustion engines. In this work, ignition delay times of an oxygenated gasoline (Euro 6 E10) are investigated with EGR and NO_x addition. The experimental data are of interest for gasoline surrogate modeling and for predicting fuel ignition behavior in various engine combustion modes. We studied Euro 6 E10 reactivity with EGR additions of 20 % and 40 % (by mass) doped, in select cases, with high levels of NO_x (874, 1501, 3174, and 5568 ppm, by mol%). Experiments were performed in two high-pressure shock tubes (HPSTs) and two rapid compression machines (RCMs) over a wide range of temperature (658–1610 K), equivalence ratio (0.5, 1.0) and at pressures of 20 and 30 bar. Results show that EGR addition inhibits Euro 6 E10 gasoline reactivity in the intermediate- and low-temperature regimes, while it is minimally affected at high-temperatures. In contrast, a strong reactivity-promoting effect of NO_x is observed at temperatures greater than 825 K for all equivalence ratios investigated, while an inhibiting effect is seen at lower temperatures with a high doping of NO_x (1501 ppm). For fuel-lean cases, where Euro 6/EGR mixtures are sensitized with 3174 – 5568 ppm NO_x, a significant reactivity-promoting effect is observed across the entire range of conditions investigated, except at temperatures below 830 K, where the NO_x-inhibiting effect dominates. A gasoline surrogate model is developed by combining a detailed gasoline surrogate mechanism with appropriate sub-models and making minor updates. The proposed model captures well the influence of EGR and EGR/NO_x on Euro 6 E10 autoignition over the wide range of conditions studied here. Finally, sensitivity analyses were conducted to identify key reactions contributing to the perturbative effects of EGR and EGR/NO_x on oxygenated gasoline ignition.

Despite the widespread use of renewable and green energy, the demand for fossil fuels is also rising due to increasing global energy demand. Therefore, unconventional solutions, with safe environmental impacts, are being pursued to solve this problem. Instead of getting rid of the exhaust gases in the surroundings, one solution might be to inject them with the oxidizer into the oil reservoir, to initiate an in-situ combustion (ISC) process to enhance oil recovery. A numerical study of a 1-D combustion tube has been conducted and validated to simulate the in-situ combustion process using enriched air as the oxidizer. The effects of injecting exhaust gases with the oxidizer are studied. Different ratios of oxygen to nitrogen are used in the enriched air as well as different ratios of exhaust gases. If enriched air which is mostly oxygen, i.e. 95% O₂ +5%N₂, is used, it is found that replacing 10% of the enriched air with exhaust gases can increase the oil recovery factor (ORF) from 94.7% to 94.9% and replacing 20% can improve oil recovery to 95.1%. For another enriched air, 60% O₂ +30% N₂, it is found that replacing portions of the enriched air with exhaust gases will reduce the oil recovery factor. In all previous cases, it was found that replacing the proportions of enriched air with exhaust gases reduces the amount of fuel burned and increases hydrogen production.

Dynamic modulus (|E*|) measurements of hot-mix asphalt (HMA) mixtures are critical for understanding material behavior but present significant challenges due to the complex testing procedures and precision required. While substantial efforts have focused on developing predictive models for |E*|, the critical role of experimental data preprocessing has been largely overlooked in the existing literature. This study addresses this gap by proposing a novel, comprehensive framework for both preprocessing and post-processing of dynamic modulus data. Leveraging the well-established ASU |E*| database and the NCHRP 1–40D Witczak prediction model as benchmarks, we introduce advanced empirical techniques, including probability distribution analysis, scatter and box plots, correlation coefficients, and mutual information metrics, to refine data quality and enhance the interpretability of predictive models. Our approach reveals new insights into the interaction of various input factors and |E*| values, leading to improved model robustness and reliability. The post-processing techniques further substantiate the predictive power of the Witczak model, yielding significant enhancements in accuracy and reliability. This research pioneers a standardized data preparation methodology that sets a new precedent in asphalt material engineering, offering a robust foundation for future |E*| modeling and analysis.

Columns are critical components resisting the collapse of a reinforced concrete frame structure subjected to high sustained loads., previous works have been focused on studying the structural behavior of pin-ended RC columns when subjected to sustained loads. The structural behavior of the slender column is the result of geometric nonlinearity as well as the material strength and deformability. This paper sheds a new light on the effects of different influential parameters on the axial and lateral deformational behavior of slender RC columns with different degrees of end restraint, subjected to nonlinear strain distributions produced by a time-dependent loading history. A rigorous and efficient numerical model is developed and the long-term structural and deformational behavior of uniaxially and biaxially loaded slender RC columns is investigated. The numerical method uses the sectional analysis technique and incorporates the nonlinear behavior of cross-section as well as the nonlinear responses of slender columns. Iteration techniques are used to find the strain distribution on the cross-section and the equilibrium deflection profile of the column. Time dependent effects due to creep, shrinkage and aging of concrete are included in the analysis. Comparisons of predicted columns behavior with those observed in laboratory tests show good agreement for both capacity and deformation that validate the numerical model approach. A parametric study is conducted to investigate the effects of key parameters including loading and section properties on the column responses.

This research aims to evaluate the impact of pounding on seismic demands for neighboring irregular buildings with collinear alignment eccentricity and provide valuable recommendations for seismic design. To achieve this, a numerical simulation is conducted to calculate the effects of pounding on the seismic response requirements in different scenarios where two irregular adjacent buildings with eccentric center of mass are considered, plan irregularity is reflected with eccentricities between the rigidity center and mass center of the building’s superstructure. Adjacent buildings with three different heights involve four-, eight-, and twelve-story buildings with moment-resisting frame (MRF) structural system. To ensure reliable estimation of engineering seismic demands, three different ground motions, which are fully compatible with the design spectrum, are applied to different adjacent building configurations. A nonlinear time history analysis is performed to determine the response demands for different adjacent buildings with collinear alignment eccentricity, such as displacement, inter-story drift, story shear force, impact force, and acceleration responses. The Engineering Design Parameters (EDP) are thoroughly examined to gain a comprehensive understanding of the structural behavior and performance of the adjacent irregular buildings. The findings hold for all these scenarios, suggest that the colinear eccentricity of the irregular building in the closing/convergence direction, promotes the pounding and increases the number of impacts, while the eccentricity in the opening/divergence direction, reduces the pounding probability and the number of impacts between adjacent buildings. Moreover, the findings highlight the impact of eccentricity on peak acceleration responses and emphasize the importance of considering eccentricity in assessing the dynamic response of adjacent buildings with insufficient separation.