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The demand for non-toxic and biodegradable shale inhibitors is growing in the drilling industry. In this paper, the effect of notoginsenoside (NS) as a new, environmentally friendly inhibitor of shale hydration is systematically studied for the first time. The inhibition performance of NS was evaluated via inhibition evaluation tests, including mud ball immersion tests, linear expansion tests, shale rolling recovery tests, and compressive strength tests. The inhibition mechanism of NS was analyzed using Fourier transform infrared spectroscopy (FTIR), contact angle measurements, particle size distribution determination, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The experimental results demonstrate that NS is able to adhere to the clay surface, forming a hydrophobic film that prevents the entry of water molecules and inhibiting the hydration dispersion of the clay. Because of this, NS can maintain the original state of bentonite pellets in water, which can effectively reduce the swelling rate of bentonite, increase the recovery rate of shale drill cuttings, maintain the strength of the shale, and therefore maintain the stability of the borehole wall during drilling. In addition, NS is non-toxic, degradable, and compatible with water-based drilling fluids. The above advantages make NS a promising candidate for use as an environmentally friendly shale inhibitor.

Drilling fluids face failure during drilling deep reservoir with high temperature and high salt. The experimental results show that high temperature and salinity reduce the negative charge on the surface of bentonite in the drilling fluid and cause the coalescence of bentonite particles. As a result, the particles coalesce, the grid structure is destroyed, and the rheological properties, rock-carrying capacity and filtration properties are lost. To resolve the foregoing, in this study, 0.05-wt% carbon nanotubes are introduced into a 4% bentonite drilling fluid under conditions where the temperature and concentration of added NaCl reach 180 °C and 10 wt%, respectively. The carbon nanotubes adsorb on the bentonite surface and increase the space among bentonite particles. The steric hindrance prevents the coalescence of bentonite in high temperature and high salt environment. Thus bentonite maintains the small size distribution of bentonite and supports the bentonite grid structure in the drilling fluid. As a result, the rock-carrying capacity of the drilling fluid increases by 85.1%. Moreover, the mud cake formed by the accumulation of small-sized bentonite particles is dense; consequently, the filtration of bentonite drilling fluid reduced by 30.2%.

The introduction of oxygen-defects has been a versatile strategy to enhance photocatalysis efficiency. In this work, a 2D/3D Bi/BiO2-x/Bi2WO6 heterojunction photocatalyst with rich oxygen-defective was in sequence prepared through a facile solvothermal method, which displays favorable photocatalytic activity towards organic contaminants under visible-NIR light irradiation. The enhancement in photocatalytic performance can be attributed to the synergistic effect between oxygen-vacancy-rich heterojunction and the localized surface plasmon resonance induced by metallic Bi. The functional group interaction, surface morphology, crystal structure, element composition, and tuned bandgap were investigated by FT-IR, SEM, Raman shift, ICP-MS, and XPS technique. The spectrum response performance of the photocatalyst was verified by UV-visible DRS analysis. Results of photodegradation experiments toward organic contaminants showed that the prepared photocatalyst can degrade 90% of phenol in 20 mins under visible-NIR light irradiation, both Z-scheme heterojunction and the introduction of Bi metal contribute to the enhancement in the photocatalytic activity. The results of the DFT calculation suggest that the valence band-edge hybridization within BiO2-x and Bi2WO6 can effectively enhance the photocatalytic performance by increasing the migration efficiencies of electron-hole pairs. Moreover, a possible mechanism was proposed on the results of EIS, ESR and GC-MS tests. This work offers a novel insight for synthesizing efficient visible-NIR light photocatalysis by activating the semiconductors with Bi metal.

An updated H2/O2 kinetic mechanism was proposed by incorporating carefully selected reaction rate coefficient and great progress in radical chain mechanisms, in which the uncertainties of rate coefficient were discussed. The performance of the current mechanism was compared to other H2 mechanism and validated against a wide range kinetic targets, including oxidation, decomposition in shock waves, ignition, flame speed and flame structure. Results show that the current mechanism obtains an overall improvement of performance, especially for the flame speed. By using the updated binary diffusion coefficient from ab initio calculations and the chemically termolecular reactions, the current mechanism presents better agreement with the new experimental flame speed at atmospheric pressure and obtains the improved performance with respect to the negative pressure dependence of high-pressure H2 flame. Furthermore, the flame speed predictions are strongly sensitive to the H2O third body efficiency in the H2 mechanism, affecting the water-contained H2 flame. The modeling results of rapid compression machine ignition show that present mechanism can more accurately predicts the ignition delay under engine-like conditions. However, all three mechanisms cannot accurately reproduce the negative pressure dependence behavior of mass burning rate in high-pressure H2 flame, which may be attributed to the fact that the important reaction O + OH(+M) = HO2(+M) that significantly affects lean high-pressure H2 flame is not included in current mechanism. Consequently, continuous works should be emphasized on the reactions that are important but neglected in H2 mechanism. All these not only develop an improved H2 reaction mechanism for high-pressure combustion, but also point out the direction for refining the H2 mechanism.

The respective performances of hypothetical Stirling engine and Stirling cooler in Vuilleumier machines are usually unclear. In this paper, a method of alternate combination of adiabatic sub-model with considering the losses and isothermal sub-model without considering the losses was proposed. The engine's work output is obtained by combining adiabatic engine and isothermal cooler, while the cooler's work input is obtained by combining adiabatic cooler and isothermal engine. Then, engine's thermal efficiency and cooler's coefficient of performance (COP) were obtained. The relative Carnot efficiency of hypothetical engine was 45%–57% at conditions of 550 °C hot temperature and 50 °C–70 °C warm temperature. The relative Carnot efficiency of hypothetical cooler was 44%–51% at conditions of −20 °C~10 °C cold temperature and 50 °C~70 °C warm temperature. In addition, a comparison of Vuilleumier machines’ COP based on a complete adiabatic model and the hybrid model was made. The ratio of COPV,hybrid over COPV,adia was in the range of 0.9~0.94. It indicated that the respective thermal efficiency and COPcooler in the hybrid model could approach to those in a complete adiabatic model.

The methane oxy-fuel combustion highly diluted by CO2 at supercritical region has the best potential for its near-zero emission characteristics and high thermal efficiency, while its auto-ignition characteristic is still not clear. In current investigation, a model with detailed chemical kinetic mechanism was introduced to research its ignition delay times (IDs). Results showed that the fold points in low-temperature and high-pressure region is due to CH3O2 which only involved in Aramco-Mech 1.3. When temperature increases, the inhibition of the termination reactions plays a dominate role at low pressure, while the promotion of the branching reactions contributes more to the acceleration of ignition at high pressure. Five dominant pathways and their variations were clarified to depict the inhibition effect of the ratio of CO2/O2. Based on the newly proposed combustion mode, it was found that temperature dependence of the nonnegligible CO2 collision effect is opposite under low and high pressure with full-oxy combustion mode. This investigation extended the research region to higher pressure and comprehensively studied the relevant factors on the auto-ignition which not only provides theoretical reference for the chemical kinetics study of methane, but also contributes to the further researches of EGR, SCF and near-zero emissions technologies.

In this paper, three recently updated mechanisms were compared with experimental data, and FFCM 1.0 mechanism was chosen to perform chemical kinetic investigation of laminar burning velocity (LBV) for CH4/H2 mixtures. Results show that increasing hydrogen and pressure, LBV presents opposite results, which depends on the competition between promotion and inhibition effect at different hydrogen fractions and pressures. Based on growth rate of LBV, it is possible to determine three regimes for CH4/H2 mixtures at high pressures. When hydrogen fraction is less than 60%, the LBV of CH4/H2 mixtures at high pressures is not very sensitive to hydrogen, showing complex variation. Flame structure and radical concentration imply that the enhanced LBV by adding hydrogen, which is a combined result of chemical and thermal effects, is realized by improving the active radical production. Then, quantitative analysis of contribution value found that reaction OH+H2=H+H2O plays an important role in H production with increasing hydrogen fraction at high pressure. Through this work, it not only studied the interactive effect between CH4/H2 combustion system and varied conditions (such as pressure and hydrogen fraction), but also the influence mechanism was revealed in depth. All these have provided useful suggestions on fuel design for power machines.

In this research, a newly proposed method combining Chemkin with CONVERGE was used to study the transient in-cylinder chemical reaction process in NG-diesel dual fuel engine. The selected mechanism was verified by comparing the results of CONVERGE with experimental data, and then the calibrated model of CONVERGE was used to provide boundary conditions for Chemkin. On this basis, the detailed combustion process was simulated at different natural gas substitution ratio (NGSR). The results show that, the chain branching reaction, long-chain to short-chain reaction, and reactions associated with OH radicals have significant impacts on temperature. It can also be found that the combustion of fuel shows a distinct two-stage reaction process. During the low temperature stage, both the CO and NO emissions are little. While at the high temperature stage, the CO emissions first rapidly increase and then decrease due to the consumption reaction, and the NO emissions also have a quick increase. When the NGSR is reduced, a new path for CO generation occurs at low temperature stage, resulting in minor increase (up to 0.0019 mol fraction) of CO concentration. Meanwhile, the ignition delay is reduced significantly (by 88.5%), but the increase of diesel species does not alter the formation mechanism of emissions. All these provide guidance for improving combustion and emission performance of NG-diesel dual fuel engine.

The ever-mounting drilling operations of the petroleum industry has been accompanied by tremendous wasted drilling fluid, Polycyclic Aromatic Hydrocarbons (PAHs) in which pose a huge threat to the health of human and ecosystem. Varying approaches have been proposed to remediate the damage caused by wasted drilling fluid, among which photocatalysis has been one of the most promising approaches for organic contaminants removal. The latest investigation shows that Bi2WO6 decorated on hydrophobic CNT can remove up to 80 % organic contaminant within a short time, exhibiting a preferable photocatalytic performance. Moreover, this hydrophobic CNT can play a vital role in stabilizing the wellbore due to its excellent water repellent. The objective of the study was to find out the effect of Bi2WO6 modified hydrophobic CNT on the PAHs photodegradation and wellbore stability in the process of drilling. Bi2WO6 as a near-infrared driven photocatalyst has attracted worldwide attention due to its preferable oxygen vacancy and quantum efficiency. However, the application of Bi2WO6 was impeded by the low migration efficiency of photo-generated carriers. The combination of Bi2WO6 and composite with good conductivity has been an effective method to resolve this problem. The instability of wellbore caused by shale hydration during oil and gas drilling operations also brings a huge challenge. In this study, a photocatalyst with wellbore stabilization capacity is achieved by hydrophobic CNT modified via Bi2WO6 sheet with nano-size. The fluid loss and wettability property were measured to evaluate the wellbore stabilization capacity of this novel agent. Meanwhile, photodegradation experiments and pathway analysis were conducted to evaluate the effect of photodegradation by Bi2WO6/CNT on the organic contaminants. Data of photodegradation indicated that the PAHs can be degraded up to 80% after treated by Bi2WO6/CNT, the migration efficiency of photogenerated carriers improved significantly. A slight decrease in fluid loss and distinctive increase in viscosity can be observed after treated with 0.3% Bi2WO6/CNT solution. The results of the rheology test verified that the photocatalyst has little effect on the rheological properties of drilling fluid. The result of SEM indicated that this novel Bi2WO6/CNT composite with a bombax structure can absorb preferentially organic contaminants, which is good at in-situ photodegradation and prevention of water invasion. To sum up, PAHs in wasted drilling fluids can be photodegraded by the novel Bi2WO6 nano-sheet modified CNT, and the stability of wellbore can also be significantly enhanced due to wettability alteration.

Vuilleumier machines are a promising technology for heating. Respective performances of Vuilleumier’s engine and cooler are generally unclear. In Stirling machines, performances can be determined based on PV power flow and heat flow methods. In this work, respective performances based on two methods in current Vuilleumier models were investigated. It was found that PV power flow and heat flow methods in current Vuilleumier models were ineffective for analysis of respective performances due to there being no piston as a boundary between Vuilleumier’s engine and cooler. Then, a virtual piston was assumed, and a virtual piston based Vuilleumier model (VPBVM) was developed. The relative Carnot efficiencies of the obtained engine and cooler were 53~64% and 43~49%, respectively, at conditions of 550 °C hot temperature, 50~70 °C warm temperature, and −20~10 °C cold temperature. The results indicated that respective performances obtained in VPBVM were reasonable. Moreover, the engine’s compression ratios could be obtained in VPBVM and were 1.2~1.24. Thus, VPBVM could be effective for the analysis of the Vuilleumier machine’s engine and cooler.

In this study, a detailed 1D simulation model of the hydrogen-enriched natural gas SI engine was built according to realistic engine layout in the lab with practical boundary conditions, and validated against the experimental data. Four different types of EGR systems were comprehensively investigated, including a low-pressure (LP) EGR, a high-pressure (HP) EGR, their combinations, and an internal EGR, using the validated 1D simulation model of the hydrogen-enriched natural gas SI engine for their combustion, performance, and emissions characteristics. The results indicated that the peak combustion pressure of the in-cylinder pressure decreased with increase in EGR ratio either using the HP, LP, or combined HP-LP systems. The NOx emissions with the HP EGR were observed to be lowest of all types of EGR systems. Combined the 10% HP EGR ratio with the 5% LP EGR ratio (total 15% EGR ratio) was predicted to achieve the highest indicated thermal efficiency compared with other EGR strategies. As for the internal EGR, the peak combustion pressure and the heat release rate slightly increased with decrease in the valve overlap. Moreover, the indicated thermal efficiency firstly increased with decrease in overlap and then slightly declined. The internal EGR was mainly determined by the timing of the exhaust valve closing; However, it was not the only influence factor. The positive and negative waves in the intake and exhaust systems also played a crucial role in the gas exchange process and volumetric efficiency.

Vuilleumier heat pumps can reduce the consumption of fossil combustion and thus have huge potential for applications in heating systems. However, it receives less attentions. In this paper, a Vuilleumier heat pumps with alternate move-and-stop motions (Hofbauer–Vuilleumier heat pump) was studied. A theoretical adiabatic model and a simple adiabatic model were derived. Both models were compared to the numerical adiabatic model and isothermal model. The results of theoretical adiabatic model agreed well with that of the numerical adiabatic model in terms of Qh, Qc, COP, pressure and temperature. The accuracy of the simple adiabatic model was relatively worse than the theoretical adiabatic model but much higher than the isothermal model. Furthermore, the effects of hot, warm and cold temperatures, initial pressure, dead volumes and various heat losses (regenerators’ heat losses, displacers’ shuttle losses, pumping losses and axial conduction losses) on the performance were investigated.

Nano-lignosulfonate (Nano-LS) was formed gradually from the inside to outside through the layer by layer self-assembly method under the interaction of π-π bond and synergistic effect of ultrasound. Then acrylamide (AM) and 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) were grafted onto Nano-LS in aqueous solution, potassium persulfate used as initiator. The structure of resulting the graft copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (1H NMR) methods. Thermogravimetric analysis (TGA) revealed the thermal stability of the graft copolymer and the results showed that the thermal decomposition of the graft copolymer was after 295.16 ℃. The graft copolymers with different additions were prepared in water-based drilling fluids (WBDFs) and the action mechanism of graft copolymer in water-based drilling fluid was revealed by scanning electron microscopy (SEM). The rheological and filtration properties of drilling fluids were evaluated before and after hot rolling (BHR and AHR) at 200.0 ℃ for 16.0 h. The results revealed that the fluid exhibit shear thinning behavior under static conditions as a gelatinous structure. When the amount of graft copolymer is 3.0 wt%, the result showed that the fluid loss (FLAPI) can be significantly reduced to 7.5 mL after hot rolling at 200.0 ℃ for 16.0 h. Moreover, the results showed that the thermal stability, salt resistance and calcium resistance of the graft copolymers are high enough to be used as effective additives in high temperature, high salinity and high calcium water-based drilling fluids.

In the presented study, the influence of lean-burn on combustion and emission performance of diesel pilot ignition natural gas engine was investigated by using the method of computational fluid dynamics coupling with the reduced chemical kinetic model. Based on bench tested results, the computational fluid dynamics model was validated in four typical conditions, and then it was used for the simulation at different excess air coefficient. Due to the visibility of computational fluid dynamics results, the combustion medium process and emissions medium products were obtained, which then were used to explain the influence mechanism of excess air coefficient. The simulated results show that, under 50% load, the maximum cylinder pressure becomes larger and the start of combustion is advanced when the excess air coefficient increases from 1.0 to 1.5, and the maximum advance of the start of combustion reaches 9.5 °CA. Nevertheless, under 100% load, the start of combustion is advanced first and then retarded. Meanwhile, the higher the excess air coefficient is, the earlier the heat release rate shoots up. When the excess air coefficient increases from 1.2, the 10–50%, 50–90% and 10–90% combustion duration become longer. The nitrogen oxide emission increases as the excess air coefficient rises from 1.0 to 1.1 but decreases if it continues to increase. The unburned methane emission decreases first and then increases with the increase of the excess air coefficient. Nevertheless, at 1500 rpm and full load, the unburned methane emission shoots up as the excess air coefficient changes from 1.3 to 1.5 and the maximum difference of unburned methane emission reaches 3233 ppm.

The CuO micro/nanowires film has been prepared successfully on a Cu substrate using a combination of an electrochemical anodization and an annealing treatment. Its morphology and phase composition ...

Water splitting has been considered as one of the most promising strategies for renewable energy production. The process of water electrolysis is greatly influenced by the sluggish kinetics of the oxygen evolution reaction (OER). Therefore, it is necessary to develop a very effective catalyst for improving OER performances. The electronic properties and morphological structure of electrocatalysts can significantly affect their OER performance. Electrocatalysts with the morphology of dendrite can expose more active sites which would enhance the OER activity. Here, the 3D dendritic Ni@Ni(Fe)OOH core-shell material has been developed on nickel foam (NF) with a controllable morphology and composition using an extremely simple and fast method. The doping of Fe can effectively modulate the morphology and the electronic structure of Ni@NiO to improve the intrinsic activity of active sites. The porous dendritic core-shell structure could allow more active sites to grow and transport electrolyte faster. At the same time, the internal Ni core can work as fast electronic transfer networks. As a result, the optimized Ni@Ni(Fe)OOH/NF shows a great catalytic performance for OER with an overpotential of 226 mV cm−2 at 10 mA cm−2 and an excellent stability in alkaline solution. The results given in paper may bring important implications for the development of a series of hydrogen and oxygen catalysts.

Spray mixing and combustion processes are regarded as the major factors that determine the energy conversion efficiency and emission level of internal combustion engines. However, the related researches mainly rely on 3D flow simulation or optical engine experiments, which are highly expensive and time-consuming. In order to provide a more convenient solution, this paper developed a one-dimensional semi-phenomenological model to achieve accurate and efficient predictions on spray combustion characteristics. The model was constructed by a dimensionless spray theoretical model and limited experimental data of macroscopic spray characteristics. Inside the proposed model, a physical module was used to physical module spray air-fuel mixing conditions like fuel distribution and evaporation. Besides, an improved Arrhenius-typed correlation concerning injection parameters and environment variables was introduced to describe the chemical ignition characteristic of spray combustion. The optical experiment results showed that this method is simple and effective, and the forecasting is satisfactory. Based on the new model, the influences of blending n-pentanol on the spray combustion characteristics of diesel and biodiesel were investigated. On the physical aspect, the critical fuel concentration at liquid length position decreases with n-pentanol is blended into both fuels in the most cases, but witnessed a significant leap in 1200 K condition, especially for diesel blends; the physical ignition delay times of both diesel and biodiesel blends decreases first and go up later. On the chemical aspect, the join of n-pentanol caused the gap between the physical delay time and the chemical delay time much narrower, but the ignition patterns were different in diesel blends and biodiesel blends. Moreover, this paper proposed a series of correlations focused on the liquid length and ignition delay of n-pentanol blends sprays. These correlations covered wide conditions and showed better prediction accuracy than traditional ones.

To investigate effects of various compression ratios (CRs) and spark timing on characteristics of performance and emissions, a high CR six-cylinder heavy-duty compression ignition diesel engine was modified into the port fuel injection hydrogen and liquefied methane gas lean-burn heavy-duty SI engine and tested by using 13.6 and 14.0 CRs. Combination of alternative fuels, high CRs and control strategies was implemented in this study. Results indicated that the equivalent fuel consumption (EFC) dramatically decreased with increase of the hydrogen energy share. Additionally, the EFC reduced as higher CR was adopted. The brake thermal efficiency (BTE) firstly increased and then declined with increase of the hydrogen energy share. Besides, the BTE increased with CR. The maximum additional 1.8% of BTE was obtained by employing higher CR (14.0) for a specific operating condition. Furthermore, the NOX emissions remarkably ascended while the HC emissions significantly declined with increase of the hydrogen energy share. The CO emission formation did not show a strong relationship with the hydrogen energy share and the CR. However, the CO2 emission gradually declined with increase of the percentage of hydrogen and CR.

The design and synthesis of highly efficient electrocatalysts for OER are important for energy storing applications. In this communication, Cu(TCNQ)2 nanorod arrays have been designed and synthesized successfully with a Cu(Fe)OOH nanosheet shell by using a short oxidation process of Cu(TCNQ)2 and subsequently an ultrafast ion exchange reaction. They are expected to combine a variety of desired merits including a simple and rapid preparation process, a large specific surface area, high conductivity and multiple electrocatalytic active sites. All the worthy characteristics which make Cu(TCNQ)2@Cu(Fe)OOH are endowed with an excellent OER catalytic performances with the required overpotential of 261 mV at 25 mA cm−2 only. The present work not only produces a good OER catalyst but also provides us a new idea to design efficient OER electrocatalysts.

The compatible catalytic structure of NiCo2O4 was modified into multi-shelled hollow spheres by one-pot synthesis, followed by heat treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmet–Teller (BET) and N2 adsorption–desorption approaches were used for the characterizations of nanoparticles and multi-shelled hollow porous structures and the morphologies and crystal structures of these hollow spheres, respectively. Differential scanning calorimetry (DSC) was adopted for comparing the thermal decomposition performances of ammonium perchlorate (AP) catalyzed by adding different contents of multi-shelled NiCo2O4 hollow spheres. Impressively, the experimental results showed that the NiCo2O4 hollow spheres exhibited more excellent catalytic activity than NiCo2O4 nanoparticles as a result of their large specific surface areas, good adsorption capacity and many active reduction sites. The decomposition temperature of AP with multi-shelled NiCo2O4 hollow spheres could be reduced up to 322.3 °C from 416.3 °C. Furthermore, a catalytic mechanism was proposed for the thermal decomposition of AP over multi-shelled NiCo2O4 hollow spheres based on electron transfer processes.

In this study, the main objective of the work was to evaluate the injection strategies on the cycle-to-cycle variations of a turbocharged DISI engine fueled with ethanol and gasoline blend by using single injection (SI) and two-stagnation injection strategy (TSIS) modes, respectively. Two-stagnation injection strategy modes were adopted to control the first injection and the later second injection by changing the injection timing or the second fuel mass repartition. The cycle-to-cycle variations of the in-cylinder pressure, peak pressure and its location, maximum rate of pressure rise and its location, indicated mean effective pressure and combustion phasing were statistically analyzed and comprehensively compared with various injection strategies. Results showed that employing TSIS 3 mitigated the in-cylinder pressure fluctuation and concentrated the integral heat release compared with other injection strategies. Meanwhile, adopting TSIS 3 obtained the lowest COVPP (5.63%) and achieved the frequency distributions of peak pressure histograms in a relatively narrow range. Furthermore, the cycle-to-cycle variations of the 10–90% combustion duration were relatively small and less sensitive to change the injection strategy modes. Finally, employing TSIS 3 was proved to be the optimal injection strategy for achieving the lowest COVIMEP while obtaining the highest IMEP.

Gas-wetting alteration is a versatile and effective approach for alleviating liquid-blockage that occurs when the wellbore pressure of a gas-condensate reservoir drops below the dew point. Fluorochemicals are of growing interest in gas-wetting alteration because of their high density of fluorine groups and thermal stability, which can change the reservoir wettability into more favorable conditions for liquids. This review aims to integrate the overlapping research between the current knowledge in organic chemistry and enhanced oil and gas recovery. The difference between wettability alteration and gas-wetting alteration is illustrated, and the methods used to evaluate gas-wetting are summarized. Recent advances in the applications of fluorochemicals for gas-wetting alteration are highlighted. The mechanisms of self-assembling adsorption layers formed by fluorochemicals with different surface morphologies are also reviewed. The factors that affect the gas-wetting performance of fluorochemicals are summarized. Meanwhile, the impacts of gas-wetting alteration on the migration of fluids in the pore throat are elaborated. Furthermore, the Wenzel and Cassie-Baxter theories are often used to describe the wettability model, but they are limited in reflecting the wetting regime of the gas-wetting surface; therefore, a wettability model for gas-wetting is discussed. Considering the promising prospects of gas-wetting alteration, this study is expected to provide insights into the relevance of gas-wetting, surface morphology and fluorochemicals, further exploring the mechanism of flow efficiency improvement of fluids in unconventional oil and gas reservoirs.

In this study, the inhibition property of an organosilicate polymer was investigated as an inhibitor for water-based drilling fluids. A novel polymer was prepared using 2-acrylamido-2-methylpropane sulphonic acid (AMPS), N, N-dimethyl acrylamide (DMAA), maleic anhydride (MA), and γ-methacryloxypropyl trimethoxy silane (MEMO) as the polymerisation monomers, named as ADMM. Also, the inhibition performance was evaluated by an immersion test, a linear swelling test, and a shale cuttings recovery test. Compared with that of the other inhibitors, the addition of ADMM can effectively inhibit the swelling of mud balls, resulting in the lowest swelling height of the drilling fluid. ADMM was characterised using a thermogravimetric analysis, a Fourier transform infrared spectrometer, a nuclear magnetic resonance instrument, a laser particle size distribution instrument, and a zeta potentiometric analyser. The results showed that the decomposition temperature of ADMM was 330 °C. The shale cuttings recovery of the 1.0% ADMM solution at 150 °C was 76.32%. The dynamic shear rise rate was as low as 160%. Furthermore, ADMM was adsorbed on the clay surface at many points to form a “protective film” of the polymer, thus inhibiting the hydration of the clay.

Technically, using hydrogen in the natural gas (NG) will increase the combustion rate of the spark ignition (SI) engine, particularly at the lean burn condition, which also benefits to improve the thermal efficiency and combustion efficiency. The aim of this study was to investigate the effect of hydrogen addition on the flame propagation, emissions formation, energy balance and the relationships between exhaust emissions and mediate species during the flame propagation in the natural gas (NG) SI engine. The 1D and 3D simulation models of the NG SI engine were built and validated against with experimental data. The results indicated that the initial spark kernel volume of the NG SI engine with hydrogen addition was larger than that of without hydrogen enriched. The NO concentration increased with the hydrogen due to its higher peak combustion temperature. The NO emission mainly generated inside the flame front, where located in the high temperature combustion zone. In addition, the CO formation rate of the NG SI engine with the hydrogen addition was faster and oxidized more completely. With adding hydrogen in natural gas, the amount of H and OH were significantly increased due to the chemical amplifiers, thereby enhancing the radical pool. The HC and soot emissions of the NG SI engine were much lower with the hydrogen addition. Furthermore, the energy efficiency and fuel economy of the NG SI engine were improved with the hydrogen addition, particularly at the lean mixture conditions.

The univariate sweeping tests for fuel injection pressure, injection timing and exhaust gas recirculation (EGR) rate were conducted on a three-cylinder gasoline extended range Atkinson cycle engine (ACE). The effects of above parameters on combustion, emission and performance of ACE were studied and some useful conclusions were obtained. In general, injection pressure has little effect on combustion and engine performance except at the injection advance of 280 deg, while its effect on emission is obvious. With injection pressure rising, NOx first increases and then decreases, while CO follows a reverse trend. Compared with injection pressure, injection timing has more significant effects. As injection timing is advanced, the max combustion pressure first increases and then decreases and the peaks appear around 300deg and 320deg. The lower EGR rate reduces BSFC and NOx with little influence on other emissions. At the EGR rate of 7%, NOx decreases significantly (up to 57.5%), CO, particle number (PN) and particle density are almost unchanged, and BSFC decreases by 4 g/(kW·h) at most. As EGR rate increases to 11%, only NOx further decreases, while other emissions become worse. Thus, a lower EGR rate (e.g., 7%) combining with reasonable injection advance (300deg) is suggested to improve ACE performance.

A comparative investigation was conducted on a turbocharged direct-injection spark-ignition engine fuelled with gasoline and ethanol blend. Influences of single injection (SI) and two-stagnation injection strategy (TSIS) on thermodynamic process and performance of the engine operated on part-load condition were discussed and compared in this paper. The results indicated that 50% combustion position was slightly shifted to TDC and 10–90% combustion duration was shortened by using TSIS modes as compared with SI mode. However, the coefficient of variation in the indicated mean effective pressure was significantly increased with the second injection fuel mass repartition. In addition, the brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) were increase by adopting the TSIS modes, but the increase amplitude of BTE and BSFC was decreased, and even deteriorated in TSIS 6 mode. In comparison with SI mode, Hydrocarbon and carbon monoxide were declined with advanced second injection timing while both of them increased with increasing second injection fuel mass repartition. Moreover, NOx emissions were dramatically reduced by utilizing TSIS modes. Eventually, CO2 emission was mainly related to the carbon atom content, combustion efficiency and heat-work conversion in-cylinder.

An experimental investigation was conducted on the performance, combustion and knock characteristics of a high compression ratio, lean-burn heavy-duty spark ignition (SI) engine fuelled with n-butane and liquefied methane gas blend. Specifically, some technical adaptations were carried out on the original compression ignition (CI) engine for changing the direct fuel injection system into the electronic controlled intake port gas injection and implementing a high-energy ignition system. Results indicate that the in-cylinder pressure, heat release rate and cumulative heat release amount increase with the increased n-butane energy share. Once the n-butane energy ratio exceeds 5% in 1400 r/min, full-load, light knock occurs at this operating condition. In addition, the 50% burning location is advanced, the 10–90% combustion duration is shortened, and knocking intensity is strengthened. Furthermore, the maximum pressure rise rate fluctuates around the average value, and the oscillation amplitude also ascends with increased n-butane energy share which results in higher cycle-by-cycle variation. However, the IMEP and indicated thermal efficiency firstly go up with the increased percentage of the n-butane energy share and then decrease.

Recently, diesel/biodiesel/alcohol blend fuels have attracted tremendous attention as a potential alternative fuel in internal combustion engines, because of their beneficial effects on pollution emission and engine performance. However, there are few chemical mechanisms to forecast combustion characteristics of the ternary blends, especially for those blending with long-chain alcohols, such as butanol and pentanol. The objective of this paper is to develop a combined reduced combustion mechanism for the combustion simulation of diesel/biodiesel/alcohol (up to n-pentanol). This new combined mechanism, consisting of 229 species and 902 elementary reactions, was constructed by integrating two separated reduced mechanisms; one is the PRF-alcohols’ mechanism (Liu et al., 2016), and another is the biodiesel mechanism (Luo et al., 2012). The new combined mechanism reproduced well predictions of fuel ignition and flame speed compared with those obtained using the original ones. Extensive validations were performed against various experimental data for 0-D homogenous systems, 1-D freely propagating premixed flames and 3-D spray combustion flames. The proposed combined mechanism was shown to be versatile and robust, successfully integrating the biodiesel reaction mechanism and the long-chain alcohol reaction mechanisms into a single reaction scheme. Coupling with advanced simulation technology, it could be a powerful numerical tool in the design and optimization of new generation engines which are fueled with clean alternative fuels, especially when concerning long-chain alcohols. In addition, the effects of adding biodiesel and different kinds of alcohols on fundamental combustion characteristics of diesel/biodiesel/alcohol blend fuels were investigated using the proposed combined mechanism.

Traditional oil-based drilling muds (OBMs) have a relatively high solid content, which is detrimental to penetration rate increase and reservoir protection. Aimed at solving this problem, an organoclay-free OBM system was studied, the synthesis methods and functioning mechanism of key additives were introduced, and performance evaluation of the system was performed. The rheology modifier was prepared by reacting a dimer fatty acid with diethanolamine, the primary emulsifier was made by oxidation and addition reaction of fatty acids, the secondary emulsifier was made by amidation of a fatty acid, and finally the fluid loss additive of water-soluble acrylic resin was synthesized by introducing acrylic acid into styrene/butyl acrylate polymerization. The rheology modifier could enhance the attraction between droplets, particles in the emulsion via intermolecular hydrogen bonding and improve the shear stress by forming a three-dimensional network structure in the emulsion. Lab experimental results show that the organoclay-free OBM could tolerate temperatures up to 220 °C and HTHP filtration is less than 5 mL. Compared with the traditional OBMs, the organoclay-free OBM has low plastic viscosity, high shear stress, high ratio of dynamic shear force to plastic viscosity and high permeability recovery, which are beneficial to penetration rate increase, hole cleaning and reservoir protection. Key words: organoclay-free, oil-based drilling mud, rheology modifier, emulsifier, fluid loss reducer, weak gel, reservoir protection

In our previous work, linear polyelectrolyte cross-linker-bridged hydrogel showed fast gelation within hours, which constrained in-depth deployment of such gels. In the present report, precipitation polymerization of bifunctional VBCTHt monomers in ethanol and acetonitrile generated the nano-gel cross-linkers bearing cyclic sulfonium moieties. The addition of nano-gels cross-linkers to partially hydrolyzed poly(acrylamide) formed covalently cross-linked in situ gels at the temperatures greater than 25 °C. As the morphology of the cross-linker changed from linear form to nano-gel in the state of sphere, the gelation time was controlled from 3 to 40 h. Nano-gel–HPAM system showed three orders of magnitude of delayed gelation while maintaining comparable mechanical integrity in comparison with conventional metallic cross-linked in situ gel, where sulfonium-functionalized nano-gel cross-linkers acting as covalent gelator were utilized for in situ gel formation. The change in cross-linker morphology and bonding nature of the gels dramatically extended gelation time. The mechanics of nano-gel cross-linker-derived covalently cross-linked HPAM in situ gels could be tuned by nano-gel cross-linkers concentration. The viscosity of HPAM and ionic cross-linker gelant had lower viscosity compared to conventional Cr3+–HPAM gel system as confirmed by rheological measurements. The gelant showed excellent salt and pH resistance, rendering it applicable to reservoir conditions. We believe this pioneer work in examination of cross-linker morphology to dictate hydrogel gelation offered the possibility to deploy mechanically tunable gels with delayed gelation for in-depth treatment of reservoir formation to improve fossil energy recovery.

Integrating the advantages of inorganic and polymeric nanoscale plugging agents, this paper introduced the synthesis of a nanoscale acrylic resin/nano-SiO2 composite (AR/SiO2) with a core-shell structure for water based drilling fluid (WBM), which can enhance the plugging efficiency of shale pores, reduce fluid invasion and improve wellbore stability in shale gas drilling process. The core-shell structure of AR/SiO2 was characterized by transmission electron microscope (TEM). Thermal Gravity Analysis (TGA) indicated the thermal resistance of AR/SiO2 up to 250 °C. Theoretical analysis implied that improved plugging property of AR/SiO2 might be due to good adhesion of deformable shell parts with shale matrix and the supporting provided by rigid core parts. The plugging ability was evaluated by pressure transmission tests and N2 adsorption tests. The results demonstrated that WBM containing AR/SiO2 can substantially enhance plugging efficiency and reduce fluid invasion. Characterization of filter cakes revealed that AR/SiO2 improved the quality of filter cakes, which resulted in a considerable improvement in filtration properties.

In this study, the thermodynamics, combustion and emission characteristics of a NG-diesel dual fuel engine with varying pilot injection degree at low speed and low load were investigated by computational fluid dynamics (CFD) simulation and bench test. Based on tested in-cylinder pressure, the in-cylinder combustion process of NG-diesel dual fuel engine was quantitatively analyzed. On this basis, both the one-dimensional and three-dimensional CFD simulated models were built and then validated by tested data, which were used to analyze the combustion and emission characteristics of NG-diesel dual fuel engine. From this study, the effects of advanced pilot injection degree (APID) on the thermodynamics, combustion and emission characteristics of NG-diesel dual fuel engine were found. With the advancing of pilot injection degree, both the SOC and 50% combustion position are advanced, which leads the maximum in-cylinder pressure and heat release rate (HRR) to increase. The 10–50% combustion duration decreases slightly but the 50–90% combustion duration increases obviously. Meanwhile, both the effective expansion efficiency (EEE) and the percent of heat transfer loss increase, while their increase rates are different, which make the brake thermal efficiency (BTE) firstly increase and then decrease. The BSNOx increases largely while the BSTHC is almost unchanged with the advance of injection timing. Although more HC is generated in the early stage as the pilot injection degree is retarded, the post-combustion becomes clear which accelerates the oxidation of HC. All these have provided theoretical guidance and data support for improving the performance of NG-diesel dual fuel engine.

This study presents an alternative method to enhance the emulsion stability of oil based drilling fluids (OBMs). Modified dimer acid (MDA) was synthesized with a molecular structure having two hydrophilic heads and two hydrophobic tails. Theoretically, the adsorption of MDA on an oil–water interface makes it possible to increase hydrogen bonding between water droplets and form three dimensional networks which benefit emulsion stability. The influence of MDA on the stability of base emulsions was studied by visual observation. Then the stabilization mechanism of MDA was analyzed from the micro and macro points of view by morphology study using a cryo-scanning electron microscope (cryo-SEM) and rheological measurements including viscosity vs. shear rates, zero-shear viscosity (η0), and creep and recovery tests. Experimental results showed that a substantial improvement in emulsion stability was visually observed when the MDA concentration was 2 g L−1. From cryo-SEM observation, a honeycomb structure was observed in the emulsion containing 2 g L−1 MDA, which can provide a physical barrier to restrain the movement of water droplets. In comparison with the rheological behaviors of the emulsion without MDA, a remarkably larger zero-shear viscosity, a solid-like behavior and a greater elasticity were observed when 2 g L−1 MDA was present. Finally, the application in OBMs shows that MDA can largely enhance electrical stability (ES) and reduce the filtration volume. The method proposed in the paper could be used to enhance the stability of w/o emulsions in a variety of fields.

In this study, an approach of direct water injection was applied to suppress knock in the high compression ratio (CR) hydrogen-enriched natural gas (NG) engine. A CFD model for the high CR hydrogen-enriched NG engine was established and its effectiveness was verified by experimental data. On this basis, effects of water injection (WI) timings on knock mitigation, combustion, and emission features of the hydrogen-enriched NG engine were studied in detail. Results show that due to the slower flame propagation speed, monitoring points No.3 and 4 (the area near the intake valve) is more likely to knock accompanied by the higher flow velocity and turbulent kinetic energy. Besides, with the advance of WI timing, KI (knock intensity) keeps nearly unchanged firstly and then has a little increase after the second phase of reduction, whose minimum occurs at −150 °CA. Meanwhile, IMEP, CA10-90, and indicated thermal efficiency (ITE) have a similar change tendency with the maximum at −150 °CA, and ITE reaches its peak of about 40.9% with an increment of 3%. From −30 °CA to −180 °CA, NOx decreases a lot, while HC and CO emissions increase to some extent. Therefore, proper WI timing can not only effectively reduce KI and NOx emission, but also improve thermal efficiency and realize high CR in spark-ignition NG engines further.

The multifunctional assembly of amphiphilic ionic liquids (AILs) can play an important role in the synthesis of various composite nanomaterials. In this work, we developed a novel strategy to steer the generation of polymer/AIL16/Ag spheres by using amphiphilic ionic liquid, 1-hexadecyl-3-methylimidazolium chloride (AIL16) as a “bridge”. Two kinds of polymer spheres (poly(methyl methacrylate), PMMA or polystyrene, PS) were used to assemble of the PMMA/AIL16/Ag (or PS/AIL16/Ag) microspheres. Subsequently, the PMMA/AIL16/Ag (or PS/AIL16/Ag) microspheres and AIL16 were used as templating agents of macropores and mesoporores respectively to prepare Ag-decorated bimodal porous silica. The effects of mass ratios of m(Ag)/m(PMMA, or PS) and amount of AIL16 on the formation of the PMMA (or PS)/AIL16/Ag microspheres and the Ag-decorated bimodal porous silica structure were investigated in detail. It was found that the dispersity and loading capacity of Ag nanoparticles onto the polymer spheres and the structures of the bimodal porous silica can be easily manipulated by changing the mass ratios of m(Ag)/m(PMMA, or PS) and the amount of adding AIL16. The obtained Ag-decorated bimodal porous silica exhibited three dimensional ordered spherical macroporous array with an ordered mesoporous silica walls, in which Ag-NPs with good dispersibility were immobilized onto the inner walls of the macroporous holes. Furthermore, the synthesized Ag-decorated bimodal porous silica displayed a better catalytic activity for the reduction reaction of 4-nitrophenol by using NaBH4 as reducer.

The unprecedented development of global industrialization has accelerated the discharge of wastewater, organic pollutants and heavy metals in which pose great threats to human health and ecosystem due to their high toxicity and poor decomposition. In this work, a facile magnetic-responsive CNT/chitosan composite for multiple contaminants removal was constructed through a two-step approach, which exhibits impressive adsorption capacity toward organic contaminants and heavy metals, the adsorbed composite can be conveniently collected by applying an external magnetic field. Surface morphology and microstructure of the fabricated CNT/chitosan composite were characterized using scanning electron microscopy, scanning electron cryomicroscopy, and transmission electron microscopy. Fourier transform infrared spectroscopy, zeta potential, Thermogravimetric analysis, and X-ray diffraction were employed to investigate the modification mechanism and the interaction within the functional groups; the magnetic responsiveness of the composite is verified by the vibrating sample magnetometer. The prepared composite displayed better adsorption to organic Rhodamine B than to methyl orange due to the strong π-π electron-donor-acceptor interaction between the benzene ring of RhB and CNT. The adsorption capacity for heavy metals followed the order Fe3+>Cu2+>Pb2+>Zn2+, the organic contaminants and heavy metals removal by CNT/chitosan composite fit the pseudo-second-order kinetic model well, the preferable adsorption could be ascribed to the synergy of the π–π stacking and hydrophobic interaction of CNT and chelation interaction of chitosan. Recyclability of CNT/chitosan composite displays its great potential in multiple contaminants elimination from aqueous solutions.

During the drilling in shale reservoirs using water-based drilling fluids, shale hydration leads to various risks such as wellbore collapse and stuck drills. However, the mechanism of shale hydration remains unclear. This work presents a comprehensive experimental investigation on the mechanisms of shale hydration using core samples of Sichuan shale (China), with a high content of illite. The impact of shale hydration on the stability of a borehole wall is presented by conducting fracture development tests, rock compressive strength experiments, SEM analyses, expansion tests, infrared analyses, and thermogravimetric analyses. Owing to the high content of illite and absence of smectite in the target shale formation, hydrogen bonding force between free/self-associated hydroxyl groups on rock surfaces and their neighbouring water molecules was observed as the primary factor that induces shale hydration. In comparison to the hydration mechanisms of mudstone, fewer hydrogen molecules bond with shale rock surfaces; however, a strong bonding force could result in the rapid hydration of the shale. For example, the hydration rate of shale 1.7 times greater than that of mudstone within the first 10 min was observed in our experiments. For this reason, the conventional inhibitors fail to prevent the surface hydration of shale rocks, and they can only protect rocks with percolation hydration. Therefore, the results of this work provide an unambiguous criteria for the development of novel inhibitors that can completely prevent shale rock hydration.

The effects of high compression ratio combining hydrogen enrichment on thermodynamic process and the consequent efficiency are experimentally evaluated on a LNG heavy-duty engine. The results indicate that increasing compression ratio and hydrogen enrichment have similar effects on the improvement of thermodynamic process. With increased compression ratio and hydrogen content, the peaks of cylinder pressure and pressure rise rate increase, ignition advances and combustion duration shortens. Moreover, combustion stability improves. Effective expansion ratio (EER) is in good agreement with indicated efficiency. The increase in compression ratio and hydrogen content can attain higher EER by improving thermodynamic process, and consequently achieve higher indicated efficiency. As hydrogen contents increase to a certain value, however, the thermal efficiencies may decrease, and NOx emissions continue to increase. Therefore, hydrogen content should be controlled in a proper proportion to achieve a balance between efficiency and emission. In the current study, the maximum loads cannot be affected as the compression ratio increases from 10.6 to 13.6, and the ultimate improvement of brake efficiency can reach 6% by the combination of high compression ratio and hydrogen enrichment. This effectively demonstrates their potential for improving thermodynamic process and efficiency of natural gas engines.

The aim of this paper investigated the performance, combustion and emission characteristics of a high compression ratio heavy-duty spark ignition engine fuelled with liquefied methane gas (LMG) and different hydrogen blends under at low engine speed. In this study, a compression ignition engine was modified to inject hydrogen and LMG using port fuel injection in spark ignition mode. The results showed that the brake thermal efficiency increased with increasing percentage of hydrogen energy content. The equivalent fuel efficiency value dramatically decreased with increasing load and slightly decreased with increasing percentage of hydrogen energy content. In-cylinder pressures of all the blends with hydrogen are higher than that only LMG fuel. The heat release rate shifted to the top dead center (TDC) and the 50% combustion location was remarkably advanced with the increasing of hydrogen energy content. Furthermore, the maximum pressure rise rate increased and the location of the maximum pressure rise rate shifted to the TDC with increasing of hydrogen energy content, respectively. NOx emission dramatically increased with increasing load and hydrogen energy content, respectively. Conversely, HC and CO2 emission concentration declined with increasing of hydrogen energy content. CO emission concentration kept low value at all the loads.

A novel approach was proposed to improve the performance of liquefied natural gas (LNG) engine. The LNG is first purified into liquefied methane and then used as engine fuel. Since the octane number of methane is higher than other compositions of natural gas, the compression ratio of liquefied methane engine (LME) can be increased for improving thermal efficiency. To verify the performance improvement potential of this approach, the experiment was conducted under varied compression ratios, and then the effects of compression ratio on in-cylinder combustion and heat-work conversion processes were analyzed. The results show that, peak heat release rate of LME is not very sensitive to compression ratio, so does the 10–90% combustion duration. With the rise of compression ratio, ignition delay period is reduced and start of combustion (SOC) is advanced. LME torque is increased by 9.5% at most while BSFC is reduced by a maximum of 10.9% under the studied conditions. NOX emissions ascend obviously with compression ratio increasing but this problem can be solved by retarding ignition timing. When other parameters are unchanged, the available compression ratio of LME can be increased to 15.6 or so without obvious knocking, which indicates great performance improvement potential for LME.

Generally, the homogeneous charge compression ignition (HCCI) engine presents superior fuel economy and ultra-low NOx and particle matter emissions compared with the traditional combustion engine. However, the HCCI engine is essentially decoupled from the spark plug and fuel injection. That means the HCCI engine has no direct control mechanism for the auto-ignition timing and subsequent combustion phase. Without effective strategies to control the auto-ignition timing on time according to the operating conditions, the HCCI engine will be limited in a small operation range due to the cold start problem, high pressure rate and combustion noise, and even knocking combustion at the high-load. Generally, the properties of physical–chemical kinetics of fuels, as well as the mixture temperature spatial and temporal changing histories in the cylinder, strongly determine the ignition timing and affect the combustion phase in HCCI engine. Some effective techniques and controlling strategies, such as fuel management, homogeneous charge preparation, exhaust gas recirculation, etc. are widely used in the HCCI engine. These techniques and controlling strategies are used solely or conjunctively with each other to control the compressed gas temperature, pressure and mixture distribution in the cylinder at the end of the compression stroke so that the charge mixture could be auto-ignited at the desired crank angle, and thereby obtaining optimal combustion phase and heat release rate on a wide operation range for the HCCI engine. Thus, this paper comprehensively reviews different effective techniques and controlling strategies used in the HCCI engine, and also summarizes in the tables.

It is a potential approach to improve the fuel efficiency that the liquid methane gas (LMG) purified from liquefied natural gas (LNG) is fueled with the high compression ratio (CR) engine, while the actual effect is restricted by the low combustion velocity of methane. To solve this problem and further improve the LMG engine performance, the approach of hydrogen addition to LMG engine was investigated by combining experiment with numerical simulation. Based on experimental data, the computational fluid dynamics (CFD) model coupled with reduced chemical kinetic mechanism was built and calibrated, which was then employed to study the effects of different hydrogen energy fraction (HEF) on combustion, thermodynamic and emission of LMG engine. The results show that, the peak of heat release rate (HRR) increases sharply with the HEF rising and leads the maximum in-cylinder pressure to increase. The indicated thermal efficiency of LMG engine first increases and then decreases, and the maximum falls in the HEF range between 8% and 12%. Although the combustion velocity of mixture gas is obviously increased by hydrogen addition, the detonation trend still becomes larger and it increases by 10 times as HEF changes from 12% to 20%. As the HEF increases from 0 to 20%, NOx emission increases continuously, while CO and CH4 emissions decrease due to the higher combustion temperature. All these provided direction for improving LMG engine performance, and offered theoretical basis for selecting technology routes to meet emission regulations.

In this study, in order to investigate the impacts of the hydrogen enrichment on the combustion cyclic variability, five cases with different hydrogen energy shares were selected to unveil their influences on the cycle-to-cycle variations of the large bore and lean burn natural gas SI engine. The results indicated that the cycle-to-cycle variations of the indicated mean effective pressure of the test engine decreased with increasing the hydrogen energy share. Moreover, the coefficient of variation of the peak combustion pressure (PCP) was 8.75% without the hydrogen addition, while the coefficient of variation of the PCP was only 2.82% with 27.68% hydrogen energy share. Additionally, the average start of combustion (SOC) was advanced, while the cycle-to-cycle variations of the SOC did not show obvious improvement with increasing the hydrogen ratio. In addition, the average CA50 combustion phase advanced, and its cycle-to-cycle variations reduced with increasing hydrogen energy ratio. The average combustion duration was shortened with increasing the hydrogen energy share. The cycle-to-cycle variations of the combustion duration reduced by 5.4% with adding 27.68% hydrogen energy share compared to the case of without hydrogen addition. Finally, no matter with hydrogen enrichment or not, the values of the correlation coefficients of the PCP and the CA50 combustion phase were all greater than 0.8, which meant the PCP and the CA50 combustion phase were strongly related.

In this study, the mechanisms of the chemical, thermal and dilution effects of the CO2, H2O, N2 and EGR quantitatively analyzed on the laminar flame speed, laminar flame structure and key radicals profiles of the premixed methane/air mixture. Moreover, the artificial species of the FCO2, FH2O, FN2 and FEGR were used to separate the combined chemical and physical effects. Furthermore, the impacts of the hydrogen enrichment coupled with the EGR on the laminar flame speed, the laminar flame structure and key radicals profiles of the premixed methane/air mixture was also studied in detailed. The results indicated that the chemical effect of the CO2 dilution gas produced the greatest impacts on the laminar flame speed, adiabatic combustion temperature and key radicals formation of the methane/air, and followed by the H2O vapor, EGR and N2. In addition, the dilution limitation of the CO2 in the methane/air was smallest, followed by the H2O vapor, EGR and N2. Moreover, the thermal effect of the CO2 in the methane/air was strongest due to its highest specific heat capacity, followed by the H2O vapor, EGR and N2. The laminar flame speed and adiabatic combustion temperature of the methane/hydrogen/air increased with increasing the hydrogen. Furthermore, the lean-burn limitation of the methane/air was extended with the increase of the hydrogen. The radical pool, such as H, O, OH, accelerated the chain branching reactions and the chain propagation reactions, and thereby increasing the effect of the chemical amplifier during the combustion of the premixed methane/air mixture.

Shuyun Liu,1 Lanlan Zhang,2 Jingqiu Cheng,1 Yanrong Lu,1 Jingping Liu1 1Key Laboratory of Transplant Engineering and Immunology, West China Hospital, 2Institute for Nanobiomedical Technology and Membrane Biology, Sichuan University, Chengdu, People’s Republic of China Abstract: Inflammatory response is a major cause of grafts dysfunction in islet transplantation. Hepatocyte growth factor (HGF) had shown anti-inflammatory activity in multiple diseases. Inthis study, we aim to deliver HGF by self-assembling peptide/heparin (SAP/Hep) hybrid gel to protect β-cell from inflammatory injury. The morphological and slow release properties of SAPs were analyzed. Rat INS-1 β-cell line was treated with tumor necrosis factor α in vitro and transplanted into rat kidney capsule in vivo, and the viability, apoptosis, function, and inflammation of β-cells were evaluated. Cationic KLD1R and KLD2R self-assembled to nanofiber hydrogel, which showed higher binding affinity for Hep and HGF because of electrostatic interaction. Slow release of HGF from cationic SAP/Hep gel is a two-step mechanism involving binding affinity with Hep and molecular diffusion. In vitro and in vivo results showed that HGF-loaded KLD2R/Hep gel promoted β-cell survival and insulin secretion, and inhibited cell apoptosis, cytokine release, T-cell infiltration, and activation of NFκB/p38 MAPK pathways in β-cells. This study suggested that SAP/Hep gel is a promising carrier for local delivery of bioactive proteins in islet transplantation. Keywords: self-assembling peptide, islet transplantation, inflammation, HGF, slow release

Cylinder-to-cylinder variation is unavoidable in multi-cylinder engine and has a severe impact on engine performance. To explore the cylinder-to-cylinder variation of engine under transient conditions, a hybrid method of dynamic signal measurement coupling with gas dynamics and thermodynamics processes simulation is presented to detect the parameters of engine. Then, this method is applied to an automobile engine under road test conditions, and the continuous state and performance parameters of each cylinder were obtained from cycle to cycle. On this basis, the range and influence factors of non-uniform of engine performance parameters were analyzed. The results show that, under transient conditions, the relative deviation of excess air coefficient in each cylinder is within ±5%, which is mainly affected by intake average pressure in low to medium speed operating regions but influenced by exhaust pressure wave and residual gas fraction in high-speed and high-load operating regions. There appears a symmetry relation between the non-uniform of RGF and excess air coefficient. The relative deviation of indicated mean effective pressure in each cylinder depends largely on the gas exchange performance, including excess air coefficient and residual gas fraction, and the maximum is larger than ±30%.

The TiO2 nanotube arrays decorated with graphene sheets (GSs) and Ag nanoparticles were prepared on Ti foils and field emission performances were explored in detail. The conventional electrochemical anodization process was used to synthesize TiO2 nanotube arrays on Ti foils. The GSs and Ag nanoparticles were deposited on as-prepared TiO2 nanotube arrays by electrophoretic deposition process and chemical deposition. The field emission properties of samples were dramatically improved after depositing GSs and Ag nanoparticles on TiO2 nanotube arrays. Compared with pristine TiO2 nanotube arrays, the TiO2 nanotube arrays decorated with GSs and Ag nanoparticles composite film show good field emission stability and a higher field enhancement factor of 3450. The turn-on and threshold fields can be decreased from 6.63 to 2.68 V/μm and from 15.28 to 6.13 V/μm, respectively. Quantitative discussion about the hybrid hetero-nanostructure field emission improvement is presented. The good field emission properties of the decorated TiO2 make it a promising candidate for applying in high-performance emission device.

In this study, the single-spark natural gas (NG) SI engine was simulated by using the CFD coupled with detailed combustion mechanism, and validated against with the experiment data. Additionally, the axisymmetrically twin-spark plugs were placed diametrically opposite to each other in the combustion head of the NG SI engine, and fired simultaneously during the simulation cases to trigger two independent spark kernels. The results indicated that twin-spark plugs yielded approximate combustion phasing and better fuel conversion efficiency. Interestingly, in the early stages of flame propagation triggered by the twin-spark plugs configuration, two independent spark kernels looked remarkably similar to the iconic of “Taiji” diagram of the Chinese Taoism, and two independent flame kernels were obviously moved along with the flow. The strong flow pushed the flame front close to the side of the intake port of the NG SI engine equipped with the single-spark plug. While two independent flame fronts of the NG SI engine equipped with the twin-spark plugs were located separately at the intake and exhaust ports in the combustion chamber. Furthermore, two independent flame fronts mutually collided with each other, and generated more independent combustion block areas in the center of the combustion chamber.

The mechanical properties and microstructure transformation of Cu–15Ni–8Sn-xFe (x = 0, 0.1, 0.3, 0.5, wt. %) alloys prepared by vacuum induction melting were investigated by using optical microscopy (OM), atom-probe tomography (APT) and scanning transmission electron microscopy (STEM). The results showed that the addition of Fe in Cu–15Ni–8Sn alloy could improve the anti-aging resistance, hardness and tensile properties. Further, when the Fe content is 0.1%, the maximum hardness, ultimate tensile strength and yield strength of the alloy were 30 HV, 123 MPa and 58 MPa higher than that of the Fe-free alloy, respectively. Through APT analysis, it is found that Fe was mainly enriched at the core of the DO22 ordered phase, which probably the key factor to improve the performance. Moreover, the inhibition of the discontinuous precipitation (DP) was related to the increases in the interlamellar spacing of DP, the decrease in the solute diffusivity along the advancing boundary, and increase in the stability of the DO22 ordered phase.