Qiangling Duan

Experimental study on a comparison of typical premixed combustible gas-air flame propagation in a horizontal rectangular closed duct

Research surrounding premixed flame propagation in ducts has a history of more than one hundred years. Most previous studies focus on the tulip flame formation and flame acceleration in pure gas fuel-air flame. However, the premixed natural gas-air flame may show different behaviors and pressure dynamics due to its unique composition. Natural gas, methane and acetylene are chosen here to conduct a comparison study on different flame behaviors and pressure dynamics, and to explore the influence of different compositions on premixed flame dynamics. The characteristics of flame front and pressure dynamics are recorded using high-speed schlieren photography and a pressure transducer, respectively. The results indicate that the compositions of the gas mixture greatly influence flame behaviors and pressure. Acetylene has the fastest flame tip speed and the highest pressure, while natural gas has a faster flame tip speed and higher pressure than methane. The Bychkov theory for predicting the flame skirt motion is verified, and the results indicate that the experimental data coincide well with theory in the case of equivalence ratios close to 1.00. Moreover, the Bychkov theory is able to predict flame skirt motion for acetylene, even outside of the best suitable expansion ratio range of 6

Experimental investigation of spontaneous ignition and flame propagation at pressurized hydrogen release through tubes with varying cross-section

An experimental investigation of spontaneous ignition and flame propagation at high-pressure hydrogen release via cylindrical tubes with varying cross-section is presented. Tubes with different transverse cross-sections are considered in the experiments: (1) local contraction, (2) local enlargement, (3) abrupt contraction, and (4) abrupt enlargement. The results show that the presence of the varying cross-section geometries can significantly promote the occurrence of spontaneous ignition. Compared to the tube with constant cross-section, the minimum pressure release needed for spontaneous ignition for the varying cross-sections tubes is considerably lower. Moreover, the initial ignition location is closer to the disk in the presence of varying cross-section geometries in comparison with straight channel. As the flame emerges from the outlet of the tube, the velocity of the flame front in the vicinity of the nozzle increases sharply. Then, a deflagration develops across the mixing zone of hydrogen/air mixture. The maximum deflagration overpressure increases linearly with the release pressure. Subsequently, a hydrogen jet flame is produced and evolves different shapes at different release stages. A fireball is formed after the jet flame spouts in the open air. Later, the fireball develops into a jet flame which shifts upward and continues to burn in the vertical direction.

An optimal multistage charge strategy for commercial lithium ion batteries

Herein, an optimal multistage charge strategy for commercial lithium ion batteries is proposed to enhance the performance of electric vehicles and hybrid electric vehicles. The strategy includes four stages of constant current charge and short constant voltage (CV) charge time. Equivalent circuit model (ECM) and capacity fade analysis are used to search for optimal charge profiles. The results indicate that the parameters of ECM change with SOC and over battery lifetime. The charge time simulation based on ECM is still accurate enough to obtain fast charging after hundreds of cycles. The charge capacity depends on the final stage charge rate and CV charge time. The maximum temperature during charging and the temperature at the end of charging, which are related to the first and fourth stage charge rates, respectively, have different effects on the capacity fading. The influence of the maximum temperature on the capacity fading changes over the battery lifetime, which may be because the capacity fading mechanisms of the battery change over the battery lifetime. Thus, the charge profiles should be suitable at different periods. CV charging prolongs the cycle life when its time is suitable value. Considering all the results and practicality, optimal values of charge can be acquired to obtain fast charging, less charge capacity loss and long cycle life.

An Experimental and Theoretical Study of Optimized Selection and Model Reconstruction for Ammonium Nitrate Pyrolysis

Ammonium nitrate (AN) is a commonly-used industrial raw material in industrial explosives and fertilizers areas. However, as an energetic material, its danger exists during the production, transportation, and storage, resulting in a large number of accidents involving personal injury and property loss. To obtain the accurate kinetic triplet parameters of AN thermal decomposition, a series of thermogravimetry analysis (TGA) experiments was conducted with four different heating rates. Activation energies were calculated by different isoconversional methods Then the kinetic triplet of AN pyrolysis was optimized using a combination of experimental and simulant methods. Combined with the traditional model-free and model-fitting approaches, the experimental kinetic model for AN pyrolysis was optimized and then reconstructed. Through the pyrolysis reaction of AN, a reliable methodology for processing TGA data of hazardous material is proposed in the paper, and the kinetic parameters can be accurately obtained by using such a kinetics method.

A multi criteria comprehensive evaluation approach for emergency response capacity with interval 2-tuple linguistic information

Abstract Emergency response capacity evaluation (ERCE) is an important and challenging issue in emergency management with the frequent occurrence of emergency events. Because of their different backgrounds and preferences, decision makers (DMs) often prefer to use linguistic variables from different linguistic term sets to express their decision information about the importance and the ratings of multi criteria involved in ERCE issue, some of which may be imprecise and uncertain. Therefore, this paper proposes a multi criteria comprehensive evaluation (MCCE) approach for ERCE with interval 2-tuple linguistic information. First, a new method for comparison between interval 2-tuples is proposed. Then, the classic analytical hierarchy process is extended into the ITL-AHP, in which the interval 2-tuple linguistic preference relation (ITLPR) and its multiplicative consistency are defined. An iterative algorithm to improve the consistency level of an ITLPR is proposed. Based on improved ITLPRs, the priority weights of criteria are derived by the normalizing rank summation method. In individual decision information collecting processes, both subjective weights and objective weights of DMs are considered. Furthermore, some interval 2-tuple interval weighted aggregation operators in which the weight vectors take the form of interval 2-tuple linguistic information are developed. Finally, a numerical illustration and comparison analyses are provided to elucidate the feasibility and superiority of the proposed method. The proposed method can provide a flexible way to perceive and appraise the emergency response capacity (REC) and an effective tool to handle the emergency management performance evaluation and decision making under fuzzy and uncertain information environment.