• Characteristics of turbulent premixed oxy-fuel combustion - a DNS study

      Peng, Zhijun; Zhong, Shenghui; Zhang, F,; University of Bedfordshire; Tianjin University (Institute of Physics Publishing, 2018-08-31)
      A 3D DNS numerical study with detail chemistry mechanism has been carried out to investigate turbulent premixed combustion with oxyfuel mixtures under similar operating conditions as happened in spark ignition Internal Combustion Engine (ICE). H2O and CO2 are adopted as the dilution in oxy-fuel combustion. The temperature profiles of oxy-H2O and oxy-CO2 combustion are consistent with those of air-fired conditions in laminar premixed flame when the molar fraction of H2O and CO2 are 73% and 66% in oxidizer, respectively. 79%, 67% molar fraction of H2O and 79%, 56% molar fraction of CO2 are also conducted to learn the effects of the dilution molar fraction on the process of flame propagation. With the molar fraction of dilution increases, the mass of C2H2 increases the flame propagation speed and the mass of CO does an opposite influence. With the investigation for effects of turbulent intensity under conditions of 73% H2O and 66% CO2 with the initial u′ of 0.8, 1.6 and 2.4 m/s, respectively, results show that the turbulent intensity has little effect on the formation of CO. It is also demonstrated that for oxy-fuel combustion, due to the disparity in laminar flame speed, an appropriate u′ is necessary to keep consistent with the flame propagation speed meanwhile to maintain suitable temperature profiles.
    • Development of a PEMFC dynamic model and the application to the analysis of fuel cell vehicle performance

      Liu, Wei; Peng, Zhijun; Kim, Bill; Gao, Bo; Pei, Yiqiang; Tianjin University; University of Bedfordshire; AVL Powertrain (Institute of Physics Publishing, 2019-12-31)
      In order to investigate basic output performances of PEMFC (Proton Exchange Membrane Fuel Cell) stack, a dynamic model of PEMFC stack has been developed by combining electrochemical sub-model and thermodynamic sub-model. With necessary validation, it demonstrates that modelling results and experimental data are in very good agreement in terms the U-I curve and power output. By applying the dynamic model to analyse performance outputs of PEMFC stack and applying the model for FC-Hybrid vehicle powertrain configuration, it demonstrates that improved PEMFC quality with increased maximum current density could increase the peak power output and also increase the working efficiency, although the increase of peak power is not linear relation with the increase of maximum current density. Higher working temperature of PEMFC would benefit the increases of both peak power output and efficiency. Compared to working temperature, ambient temperature's increase could also make positive influence on power output and efficiency, though the influence is weak. Coupling the dynamic model with a powertrain model of FC-Electric hybrid vehicle, the analysis suggests that both PEMFC stack and battery stack should have similar size for general driving condition. Too big either PEMFC stack or battery stack would increase the total weight then contaminate the fuel/energy economy.
    • Durotaxis behavior of bEnd.3 cells on soft substrate with patterned platinum nanoparticle array

      Wu, Xiaomin; Li, Li; Lei, Zecheng; Yang, Fan; Liu, Ri; Wang, Lu; Zhu, Xinyao; Wang, Zuobin; Changchun University of Science and Technology; University of Bedfordshire; et al. (Springer Science and Business Media, 2020-11-17)
      The directional arrangement of cells has crucial effect in tissue engineering fields such as wound healing and scar repair. Studies have shown that continuous nanostructures have directional regulatory effect on cells, but whether discontinuous nanostructures have the same regulatory effect on cells is also worthy of further study. Here, a series of discontinuous platinum nanoparticles (PtNPs) patterned on the surface of PDMS (PtNPs-PDMS&Glass) and glass (PtNPs-Glass) substrates were developed to investigate the effect on bEnd.3 cell durotaxis. The laser interference lithography and nanotransfer printing method were employed to fabricate the substrates. It was found that about 80% cells orderly arranged on the PtNPs-PDMS&Glass substrate, but only 20% cells orderly arrangement on the PtNPs-Glass substrate, and the number of cells on the PtNPs-PDMS&Glass substrate was five times more than that on the PDMS coated glass substrate (PDMS&Glass). The results suggested that patterning PtNPs on the PDMS substrate not only provided the topographical guidance for cells just like continuous nanostructures, but also promoted cell adhesion and growth. In addition, an improved whole cell coupling model was used to investigate and explain the cell durotaxis from the perspective of mechanism. These findings show the possibility of discontinuous nanostructures in regulating cell arrangement, and offer a useful method for the design of biological functional substrate, as well as help to understand the mechanism of cell durotaxis.
    • Impingement behaviour of single ethanol droplet on a liquid film of glycerol solution

      Lu, Lili; Pei, Yiqiang; Qin, Jing; Peng, Zhijun; Wang, Yuqian; Zhu, Qingyang; Tianjin University; University of Bedfordshire (Elsevier Ltd, 2020-05-16)
      Research on single drop impact, especially in the past two decades, has been motivated by a need for better predictive capability in many industries. However, there are few reports in the literature describing the case of single droplet impinging on liquid films with different physicochemical properties. In this study, laser-induced fluorescence (LIF) methods were used to clarify the impingement behaviour of millimetre-sized single ethanol droplets onto films of different concentrations of glycerol solution. The impingement behaviour is found to differ depending on the Weber number of the incident droplet and the viscosity and the thickness of the liquid film. New results on coalescence/splash thresholds criteria are obtained taking into account the incident droplet Weber number and liquid film characteristics. In addition, the formation mechanism and composition of secondary droplets and crown structures after collision are analysed. For the crown structure parameters, we found that the evolution of the crown height over time is affected by the combination of droplet and liquid film characteristics. The maximum height and diameter of the crown are proportional to the Weber number of the incident droplet, and these parameters can be predicted by the combination of the incident droplet Weber number and the liquid film Ohnesorge number.