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In this paper, the laminar combustion characteristics of n-heptane/carbon dioxide/air flames are numerically investigated by using the Chemkin/Premix Code and LLNL v3.1 mechanism. The equivalence ratios vary from 0.8 to 1.4 at the initial temperature of 298 K. The initial pressure is set as 1, 2, 5, 10, 20 atm. Laminar burning velocity (LBV), adiabatic flame temperature (AFT), net heat release rate (NHRR) and the mole fractions of H, O, OH, CO at stoichiometric ratio are studied with carbon dioxide (CO2) addition. Meanwhile, temperature sensitivity and rate of production (ROP) are analyzed. In addition, the physical and chemical effects of CO2 are investigated by introducing fictitious carbon dioxide (FCO2).The results show that with the increase of initial pressures, LBV decreases, AFT and NHRR increase, the peaks of intermediate products such as H, O, OH and CO decrease. The promoting effect of elementary reactions on temperature is greatly enhanced, while the inhibiting effect is slightly enhanced. With the increase of CO2 doping ratios, LBV, AFT and NHRR decrease, while the peaks of H, O, OH, CO increase first and then decrease. The promoting and inhibiting effects of elementary reactions on temperature are enhanced. Both physical and chemical effects of CO2 inhibit the combustion of n-heptane, where physical effect dominates. The total ROPs of H, O, OH change from consuming to producing, while the total ROP of CO is opposite.

The simulation results are used CHEMKIN/PREMIX code to explore the combustion characteristic of n-heptane/hydrogen/air flame. The initial temperature is set as 300 K, the pressures are set as 1, 2,...

Petroleum hydrocarbons can serve as a carbon source for marine phytoplankton, so, marine high-acid crude oil pollution events are likely to result in algal outbreaks or harmful algal blooms (HABs) in surface waters. Naphthenic acids (NAs) are the primary acidic component of crude oil, and red tide is of great concern due to its high diffusivity and strong destructive properties. It is important to study the mechanism of the toxic effect of NAs on the typical red tide algae, Heterosigma akashiwo, for the balance and stability of marine algae. The mechanism of NAs’ damage effect was investigated in terms of the antioxidant enzyme activity, cell number, the chlorophyll positive fluorescence parameters, and the cell morphology of microalgae. Experiments confirmed the hormesis of low-concentration (0.5, 2, and 4 mg/L) NAs on Heterosigma akashiwo, and the indicators of high-concentration (8 and 16 mg/L) NA exposures showed inhibition. In this study, the toxic effect of NAs on the target organism showed a clear concentration–dose relationship. The 16 mg/L NAs stress caused severe damage to the morphology and structure of the target biological cells in a short time (96 h), and the population growth decreased. The target organisms showed a staged oxidative stress response to NAs. The behavior in the low-concentration treatment groups showed toxicant excitatory effects on the photosynthetic efficiency and antioxidant enzyme activity of the target organisms. This study provides theoretical and practical data for the development of an important toxicological model of the toxicant’s excitement effects and antioxidant defense mechanisms. In addition, it provides prospective research data for the prediction and avoidance of ecological risk from NA pollution in marine environments.

Laminar diffusion flame was used to study the effect of ethanol on n-heptane flame in terms of the morphology and microstructure of soot under atomization combustion. For the same carbon mass flux at the outlet of the burner, the ratio of ethanol doping in n-heptane was changed, and the soot was collected from the axial positions of the flame at different heights using the thermophoresis probe method. The results showed that the flame height increased significantly with the increasing ratio of ethanol doping. When the ratio of ethanol and n-heptane (CE/CN) was 1.5, the flame height increased by 10 mm compared with that of pure n-heptane flame. Besides, the temperature in the center of the flame decreased with the increasing ratio of ethanol doping, but the temperature in the low position was higher than that in the pure n-heptane flame, and the temperature in the high position was lower than that in the pure n-heptane flame. However, the flame temperature was the highest when the proportion of ethanol in the mixture was greater than that of n-heptane. The temperature at the flame center decreased with the increasing ratio of ethanol doping, while the temperature at the flame edge increased with the ratio. The primary particle size of soot (soot size hereafter) in all working conditions increased with the increase of flame height, which was in line with the general growth law of soot. Moreover, the soot size at the same height decreased with the increasing ratio of ethanol doping, and this trend was most obvious at the flame height of 20 mm and 30 mm. Compared with pure n-heptane, when CE/CN was 1.5, the soot size at 20 mm and 30 mm decreased by an average of 34.83%, indicating that ethanol could inhibit the surface growth of soot particle. Furthermore, the density of soot particles collected by a single copper net decreased significantly, indicating that ethanol could reduce the production amount of soot.

Effects of N2 dilution on laminar burning velocity (LBV), adiabatic flame temperature (AFT), intermediate radicals (CH3, H) and NOx emissions (NO, N2O) of methane were investigated using Bunsen burner under the condition of fuel-rich combustion (equivalence ratio 1.0 to 1.4). The Aramco mechanism was selected to analyze the effect of N2 blending on the adiabatic flame temperature and the intermediate radicals of CH4 premixed flame under the equivalence ratios (Φ = 0.8, 1.0, 1.2). The effect of different N2 doping ratios on the NOx emissions (NO, N2O) of methane was analyzed by using GRI 3.0 mechanism. The experimental and numerical results showed that as the equivalence ratio increased (from 1.0 to 1.4), the laminar burning velocity first increased and then decreased, reaching a maximum when the equivalence ratio was about 1.05. The mole fraction changes of intermediate radicals and NOx emissions also showed a trend of increasing first and then decreasing with the increasing of equivalence ratios. Under the same equivalence ratio, the mole fraction of intermediate radicals and NOx decreased as the N2 doping ratio increased. The sensitivity analysis showed that the major elementary reactions that inhibits the generation of intermediate radicals and NOx emissions were different under different equivalence ratios and N2 doping ratios. In addition, the sensitivity coefficients of the elementary reactions that mainly promotes or inhibits the generation of free radicals and NOx decreased with the increasing of the N2 addition.

Background Acute kidney injury (AKI) is the main complication of crush syndrome (CS), and it is also a cause of lethality in CS. However, effective treatments for AKI are still lacking. Ulinastatin (UTI) is a broad-spectrum serine protease inhibitor extracted from human urine that reportedly modulates innate immunity and pro-inflammatory responses in sepsis. Here, we explored the effect and the potential mechanism of ulinastatin on crush syndrome-induced acute kidney injury (CSAKI). Methods A CSAKI rat model was established by using a digital crush injury device platform. Forty-six male Wistar rats were randomly divided into five groups: the normal control (n = 6), CSAKI model (n = 10), CSAKI plus UTI1 (50,000 U/kg) (n = 10), CSAKI plus UTI2 (100,000 U/kg) (n = 10) and CSAKI plus UTI3 (200,000 U/kg) (n = 10) groups. Hematoxylin-eosin (HE) staining was used to investigate the reliability of the CSAKI model. The percentage of Th17/Treg lymphocytes in peripheral blood was measured by flow cytometry, and the expression of transcription factors associated with Th17/Treg cells was evaluated by quantitative real-time polymerase chain reaction (PCR). In addition, specific cytokines released by Th17/Treg cells in serum and kidney tissues were detected by enzyme-linked immunosorbent assay (ELISA). Results Treatment with ulinastatin could significantly decrease serum BUN, CK, Scr, Mb and K+ levels compared with CSAKI group. HE staining results showed that ulinastatin could inhibit inflammatory cells infiltration, decrease sarcomere rupture in muscle tissues induced by extrusion, and alleviate the glomerular congestion and edema, as well as decrease myoglobin cast in kidney tissues. The proportion of CD4+CD25+Foxp3+ regulatory T (Treg) cells and Foxp3 expression levels were decreased in the CSAKI animals, while IL-17 expression levels were significantly increased, compared with those of the normal control group. Treatment with ulinastatin upregulated the proportion of Treg cells in CD4+ T cells and downregulated the expression of IL-17 compared with those of the CSAKI group. Conclusion The findings of our study indicate that UTI attenuates CS-induced AKI and alleviate the inflammatory response during the early stage. The mechanism of UTI may be due to regulating the balance between Th17/Treg cells. Our study provides a new mechanism for the beneficial effect of ulinastatin on CSAKI.