Pressure Rise Rate Research Articles

Hydrodynamic theory of premixed flames propagating in closed vessels: flame speed and Markstein lengths

A hydrodynamic theory of premixed flame propagation within closed vessels is developed assuming the flame is much thinner than all other fluid dynamic lengths. In this limit, the flame is confined to a surface separating the unburned mixture from burned combustion products, and propagates at a speed determined from the analysis of its internal structure. Unlike freely propagating flames that propagate under nearly isobaric conditions, combustion in a closed vessel results in continuous increases in pressure, burning rate and flame temperature, and a progressive decrease in flame thickness. The flame speed is shown to depend on the voluminal stretch rate, which measures the deformation of a volume element of the flame zone, and on the rate of pressure rise. Both effects are modulated by pressure-dependent Markstein numbers that depend on heat release and mixture properties while capturing the effects of temperature-dependent transport and stoichiometry. The model applies to flames of arbitrary shape propagating in general flows, laminar or turbulent, within vessels of general configurations. The main limitation of hydrodynamic flame theories is the assumption that variations inside the flame zone due to chemistry or turbulence, which could potentially alter its internal structure, are physically unresolved. Nonetheless, the theory, deduced from physical first principles, identifies the various mechanisms involved in the combustion process as demonstrated in detailed discussions of planar flames propagating in rectangular channels and spherically expanding flames in spherical vessels. It also enables the construction of instructive models to numerically simulate the evolution of multi-dimensional and corrugated flames under confinement.

Influence of stearate dry coating on ibuprofen powder: What about the combustibility?

Dust explosion is one common type of process safety incident within the pharmaceutical industry. During powder processing, surface modification is widely used to increase dust flowability by alleviating inter-particle cohesion. However, it is currently unclear whether the addition of guest particles affects the combustibility of pharmaceutical powders. To investigate the explosion hazard of stearate-coated ibuprofen powder, this paper studied the ignition sensitivity and explosion severity of pure and coated ibuprofen by determining a series of explosion parameters in accordance with ASTM standards. The results indicated that the addition of stearate significantly reduced the minimum ignition energy of the mixture. Other parameters including the minimum ignition temperature, the minimum explosible concentration, the maximum explosion pressure, and the maximum rate of pressure rise were found to have less correlation with the improvement in dust flowability. Powder characterization through methods such as the Hausner ratio, scanning electron microscope, thermo-gravimetric analysis, and X-ray diffraction were employed to investigate chemical phase changes between coated mixtures and pure pharmaceuticals. The effects of improved dust flowability and dust dispersibility on the combustibility of ibuprofen dust were discussed to improve explosion-proof awareness in the pharmaceutical industry.

Damage power enhancement of fuel air explosive with typical metal hydrides additions

To study the damage power enhancement of fuel air explosive (FAE) with metal hydrides, the effects of metal hydrides (TiH2, MgH2, ZrH2) powders on shock wave and thermal damage of pure propylene oxide (PO) were explored using a 20 L spherical explosion test system combined with colorimetric thermometry technology. The experimental results showed that compared with the base metal powders, the explosion overpressures, maximum pressure rise rates and maximum average temperatures of the solid-liquid mixed fuel with the metal hydrides (TiH2, MgH2, ZrH2) powders increased by 11.04 %, 22.61 %, 4.80 % and 26.68 %, 38.18 %, 13.91 % as well as 6.85 %, 8.57 %, 1.34 %, respectively. Furthermore, the effects of metal hydride powders on the cloud explosion fuel were better than those of Al powders, and MgH2 powders had the most significant effects on the damage power enhancement of pure PO. Metal hydride powders as high-energy additives could improve the energy release characteristics of FAE.

A modified phosphorus-based inhibitor for dry water inhibitor and its chemical mechanisms in preventing benzoyl peroxide explosion

Dust explosions caused by benzoyl peroxide (BPO) pose a significant risk to the chemical industry, making the development of high-performance inhibitors essential. The effect of a novel inhibitor on the explosion behavior of BPO dust was studied through experiments and simulations. The chemical mechanism behind the suppressed BPO dust explosion was clarified. The primary explosion hazard of BPO stems from the instability of the oxygen–oxygen bond. To address this, a novel phosphorus-based dry water powder inhibitor, MAP-DW, was prepared which effectively captures key reactive radicals involved in the chain reaction. At the optimal explosion concentration of BPO, a concentration of 400 g/m3 of MAP-DW reduced the maximum explosion pressure and the maximum explosion pressure rise rate by 96.48 % and 99.58 %, respectively. The suppression effects of MAP-DW on the explosion of BPO dust include heat absorption, oxygen dilution, thermal insulation, and capture of key free radicals. The kinetic simulation results showed that the suppression cycle between phosphorus-containing substances captured key chain reaction radicals, and the coupled suppression among NH3, H2O, and phosphorus-containing substances dominated the suppression mechanism of MAP-DW on BPO dust explosion. This study provides new insights into the characterization and suppression of BPO dust explosion, while also supplying crucial data for the safe utilization of peroxides.

DPdT >1200ms predicts greater and sustained drop in ejection fraction post mitral TEER

Abstract Background The maximum rate of left ventricular pressure rise (dP/dTmax) using a CW Doppler from a mitral regurgitation (MR) curve is a simple technique which can estimate myocardial contractility, with "normal" values >1200ms. This technique has not been applied to patients undergoing mitral transcatheter edge-to-edge repairs (M-TEER). Purpose Assess if dP/dT can predict post-procedural ejection fraction (EF). Methods A retrospective review of all M-TEER's performed from January 2011 – February 2023 at a single cardiac centre with an adequate MR CW Doppler to calculate the dP/dT as well as a subsequent TTE at the institution were included. An early TTE (performed day 1-50, average 34.9) and late TTE (goal 1 year, average 354 days) were recorded. Results A total of 155 M-TEER procedures were performed; 66 for degenerative MR (DMR), 11 for atrial functional MR (AFMR) and 78 for ventricular functional MR (VFMR). Baseline characteristics: overall EF 47.9% (DMR 61%, AFMR 52% and VFMR 32%). Age DMR 75.8y, AMFR 78.9y, VFMR 75.6y), overall 31.6% female (DMR 34.6%, AFMR 45.5%, VFMR 25.8%). Surprisingly the DMR cohort demonstrated a significant drop in EF post M-TEER of 5.1% (p<0.001, figure 1). This was most marked in the group with "normal" dP/dT of >1200ms (figure 2, DMR EF drop 7.8% p<0.001). This cohort remained at the new, lower value on follow up (figure 2). The EF in the VFMR remained severely impaired despite M-TEER (figure 1). There was no significant difference between EF pre or early post (p= 0.86). When divided into groups according to baseline dP/dT. The greatest drop in EF was again seen with an apparently normal dP/dT of >1200ms (figure 2). Conclusion "Normal" dP/dT of >1200ms in patients undergoing M-TEER is likely a marker of hyper-contractile LV function as a compensatory mechanism, and may predict a greater fall in EF post correction of MR.

Study on gas explosion propagation law in excavation roadway with TBM

Gas explosion is one of the five major hazards in mines, with about 36% of such incidents occurring in the excavation working face. Therefore, to investigate the impact of gas explosion propagation laws within excavation roadways, we conducted a simulation analysis of parameters such as peak of explosion overpressure, peak rate of pressure rise, and flame propagation speed in the presence of a Tunnel Boring Machine (TBM). In the presence of the TBM, the explosion overpressure approximately doubles, and the flame propagation speed also greatly increases, exacerbating the explosion hazard. Thus, when investigating gas explosion laws within excavation roadways, the presence of a TBM emerges as a significant factor that cannot be overlooked. Furthermore, an analysis of the effects of methane concentration and gas accumulation length on explosion parameters was conducted. The results indicate that when the flame passes through the TBM baffle, the average flame propagation speed increases the most when the methane concentration is 9.5%, increasing by about 6 times. In addition, as the gas accumulation length increases, both explosion overpressure and flame propagation speed gradually increase. Additionally, TBM has a certain impact on flame propagation and methane dissipation.

Exploring the benefits of hydrogen-water injection technology in internal combustion engines: A rigorous experimental study

Previous hydrogen researchers have demonstrated the great potential of hydrogen as a zero-carbon fuel and its wider operational ability to directly replace the existing fossil-fuelled internal combustion engines (ICE). Hydrogen direct-injection technology can operate at stoichiometric combustion conditions, fully eliminating the intake backfire phenomena, which has the benefit of low airflow requirements and is a suitable solution for naturally aspirated ICE platforms. However, significant challenges must be addressed when operating an H2 ICE at or near stoichiometric. These include rapid pressure rise rate, high in-cylinder gas pressure and temperature and the consequential higher engine-out NOx emissions. This study provides a comprehensive experimental analysis of the effect of water injection on a light-duty H2 engine’s performance, efficiency, burn durations and NOx emission. The engine was modified to operate with hydrogen via a centrally-mounted direct H2 injector and an intake port-mounted water injection system. The study included water vapour measurements, NOx concentrations and other exhaust gases. The practical implications of these findings are significant. The results demonstrated that the NOx emissions were reduced by 79% when the water was injected at a rate of 5 kg/h at 10 bar IMEP and 2000 rpm. This reduction in emissions, coupled with the observed decrease in cylinder pressure and the rate of pressure rise, could substantially improve engine performance and efficiency. At higher load regions, the water injection extended the maximum engine load to 24 bar IMEP and increased the engine torque output by 10%. The maximum Indicated Thermal Efficiency (ITE) increased from 41% at 16.5 bar IMEP to 42.5% at 18 bar IMEP at a lower lambda, with a corresponding reduction in the intake-air-boost pressure requirement. Of particular note, the use of water injection decreased the engine-out NOx emissions under high-load conditions by more than 55%, even at richer AFR compared to pure hydrogen operation.

Performance Characteristics of a Compression Ignition (CI) Engine Using an Environmentally Friendly Waste Plastic Fuel

Due to growing demands and depleting reserves of petroleum-based fuel, there is a necessity to find an alternative fuel for IC engines. Also, environmental concerns and globally faced problems like lots of garbage generated through plastics is a major issue in India. There is a significant disparity between plastic production and waste plastic generation. Therefore, the need for alternative fuels derived from municipal plastic waste has emerged to enhance the performance of IC engines, decrease emissions, and address other environmental concerns in line with the “Swachh Bharat Mission of India”. In this study, the alternative fuel was produced from a municipal mix of plastic waste by pyrolysis process. The experiments were carried out with a constant speed of 1500 rpm at different load conditions and fueled with standard diesel, waste plastic fuel and other blends to investigate IC engine performance and combustion and emissions in terms of brake thermal efficiency, brake power, brake specific fuel consumption, cylinder pressure, net heat release, mean gas temperature, rate of pressure rise, andbrake specific CO2, NOx, CO and HC emissions parameters were investigated and it is compared with standard diesel. The overall result shows that WPO20D80 and WPO30D70 exhibit the peak performance (torque, BP, BTE and BSFC) and lowest emissions (HC, CO, NOx) at all load conditions. Moreover, according to all the performance results, the lowest BSFC with maximum brake thermal efficiency and variations was 24.01% and 0.346 Kg/kWh for the WPO30D70 blend at part load condition. The minimum brake-specific NOx produced by the diesel blend at peak load conditions (WPO20D80) is 138.66 ppm, which is higher than other blends. This phenomenon may be attributed to an elevated proportion of pre-combustion and an extended ignition duration, resulting in a high cylinder temperature and an enhanced rate of heat release. This analysis contributes to a deeper understanding of the environmental implications associated with different fuel blends and load conditions. Notably, the blends ranging from 10% to 50% showed good tendencies to be utilized with diesel engines and consistently exhibit favourable brakespecific emission profiles, suggesting its potential as an environmentally friendly alternative fuel.

Effects of different gas energy shares on combustion and emission characteristics of compression ignition engine fueled with dual-fossil fuel and dual-biofuel

This study systematically investigates the energetic and environmental performance of a four-cylinder compression ignition (CI) engine fueled by gaseous and liquid dual-fuel (D-F), utilising various combinations of fossil fuels and biofuels. Fossil diesel or pure hydrotreated vegetable oil (HVO) – new generation biodiesel was used as the pilot fuel to initiate ignition of the gaseous fuel. The gaseous fuels used were natural gas (NG) and simulated biogas (BG) composed of 60 % NG and 40 % CO2 by volume, injected into the intake manifold at varying gas energy shares (GES) of 40 %, 60 %, and 80 %. Reference values were provided from conventional combustion of diesel fuel and HVO. This study used numerical simulations to examine indicators of combustion, such as ignition delay, premixed combustion phase, diffusion combustion phase, and subsequent combustion phases, across diverse fuel combinations. Within lean dual-fuel mixtures, when the gaseous fuel remained below the flammability threshold, the peak pressure was diminished, the rate of pressure rise was lowered, and the combustion process decelerated, facilitating a faster transition to the diffusion phase. As the engine load and GES increased, the excess air ratio decreased, bringing the air-fuel mixture closer to the flammability limit, which in turn altered the combustion characteristics and engine performance trends. Combustion with increasing BG content showed partial similarities to that of NG, though the high CO2 content in biogas was found to suppress combustion, functioning similarly to an exhaust gas recirculation. The study also compared brake thermal efficiency (BTE), as well as specific emissions of CO, HC, NOX, CO2, and smoke for the D-F engine operation against pure diesel and HVO at different loads and GES levels. Additionally, an overlimit function was used to assess the emission levels of D-F engines with reference to emission limits.

Assessing combustion characteristics of alternative fuels in a CI engine by use of a wavelet-based analysis of engine vibration signals

In the current work, a wavelet-based approach for assessing combustion performance of alternative fuels in compression-ignition engines, indicated that changes in cylinder pressure amplitude were reflected by commensurate changes in a proposed parameter, with a maximum of a 9% variation. The proposed parameter, the wavelet transform coefficient maximum amplitude (WMA), successfully accomplished this for various engine conditions. The wavelet transform coefficient standard deviation (WSD), a second proposed parameter, was able to track changes in the rates of pressure rise associated with changes in load conditions and fuel type, with a maximum variation in the parameter of 7%. The approach was assessed by testing six fuels in a test engine unit. Thermodynamic property data and vibration signal data were recorded for each of the fuels tested, at six loading conditions. Subsequently, combustion performance was evaluated using traditional thermodynamic parameters and using the WMA and WSD via a MATLAB based algorithm. Thus, it was surmised that the proposed approach can form the basis for a vibration-based assessment of alternative fuel combustion performance in reciprocating engines.

Combustion and emissions of an ammonia heavy-duty engine with a hydrogen-fueled active pre-chamber ignition system

Combustion and emission characteristics of a heavy-duty single-cylinder ammonia engine with a hydrogen-fueled active pre-chamber ignition system are investigated experimentally at the condition of IMEP 10 bar, 1000 rpm, where effects of spark timing, excess air ratio (λ), and hydrogen energy ratio are tested. Three distinguishable combustion phases are observed, including pre-chamber combustion, turbulent-jet-controlled combustion, and ammonia-chemical-kinetics-controlled combustion. Advancing spark timing makes combustion phases earlier, increasing pressure rise rate, combustion pressure, and NOx emissions. The optimal spark timing for the highest indicated thermal efficiency (ITE) is −12°CA ATDC in the experiment. λ range for stable combustion is 1.1–1.5 and ITE peaks at λ = 1.3. The hydrogen energy ratio, 7.9%∼10.5%, has little influence on the engine performance. However, a low hydrogen energy ratio could increase the risk of misfire. The optimal hydrogen energy ratio is about 9∼10%.

Computational investigation of combustion and emission characteristics of HCCI engine fueled with Carbon-Free NH3 –H2O2 blend

A computational investigation is provided of the utilization of blends of NH3 and H2O2 as carbonless fuels for HCCI combustion. A Computational Fluid Dynamics (CFD) model is developed and validated to assess the engine’s performance under varying proportions of NH3 and H2O2, equivalence ratios, and inlet temperatures. The heat release rate profiles demonstrated dual peaks, which were rationalized as an initial fuel decomposition followed by a slow thermal explosion and then a fast depletion of the fuel after the generation of a pool of OH radicals through decomposition of H2O2. Findings suggest that an increase in mole fraction of H2O2 advances combustion. Increasing the H2O2 volume fraction also decreases combustion duration, while increasing the IMEP. In-cylinder peak pressure and Maximum Pressure Rise Rate (MPRR) increase with H2O2 mole fraction, leading to reduced thermal efficiency, particularly at higher equivalence ratios, and an increased danger of uncontrolled combustion (knocking). Additionally, higher inlet mixture temperatures were shown to result in an advancement in the start of combustion and a reduction in combustion duration, with a corresponding increase in peak pressure. This points to the possibility of potentially controlling the notoriously difficult-to-control HCCI combustion through intake temperature for NH3/H2O2 fuel blends. However, increased NOx emissions are observed for increased intake temperature and in any case the NOx emissions are orders of magnitude above current regulatory limits, which means that practical engine operation will only be possible with an aftertreatment scheme based on the de-NOx activity of NH3.

Experimental investigation of OH* emission spectrum characteristics and transient ignition dynamics in methane and coal dust mixtures explosions

Combustible gases, dusts and their mixtures are widely present in human production and life，and the fire and explosion disasters caused by them pose a serious threat to the field of energy security applications. Studying the ignition process of mixtures is essential for disaster risk assessment and safety protection. In this work, the explosion characteristics and OH* emission spectra of the mixtures were experimentally tested by varying the fuel equivalence ratio ( ER ≈ 0.79 ~ 1.71), and the evolution of the transient flow field structure during the ignition process was quantitatively analyzed using the schlieren image velocimetry method. The results indicate that the emission spectrum of OH* is closely correlated with the maximum explosion pressure, and the spectral intensity of OH* at 306.4nm is consistent with the maximum rate of explosion pressure rise. The flow field during the ignition process of the mixtures shows that a small amount of coal dust (concentration≤30g/m3) can significantly promote flame acceleration and instability as the methane concentration is in lean combustion or stoichiometric ratio. However, when the concentration of coal dust increases (concentration≥40g/m3), coal dust will suppress flame acceleration and instability. For methane concentration in fuel-rich combustion state, coal dust always suppresses flame acceleration and instability. The experimental results contribute to a further understanding of gas and coal dust mixed explosions and provide a verification database for the construction of chemical kinetic mechanisms.

Phase change materials as hydrogen explosion suppressants: An experimental and kinetic investigation

To investigate the potential application of phase change materials as H2 explosion suppressants, in the present work, the inhibition effect of Na2HPO4·12H2O, K2HPO4·3H2O, and Na2CO3·10H2O on H2 explosion were experimentally studied. The corresponding explosion suppression mechanism was calculated by using a comprehensive combustion model. Results showed that the selected phase change materials inhibited the H2 explosion, and Na2CO3·10H2O has the most significant effect for fuel-lean H2-air mixtures when 12 g was added. Of which the maximum explosion pressure (Pmax) and maximum rate of pressure rise (dp/dt)max were reduced by 26.6 % and 28.1 %, and maximum pressure increase time (tb) and peak pressure time(tc) were increased by 112.2 % and 120.3 %. The inhibition mechanism of Na2CO3·10H2O on H2 was revealed by numerical simulation. The adiabatic flame temperature (AFT) and laminar burning velocity (LBV) of H2-air mixture decrease with increasing hydrated salt addition, the free radicals H, O and OH have a decisive influence on the explosion process during which H decreases by 86.4 % at most. The chain initial reaction O + H2 ⇌ H + OH and the sodium-containing primitive reaction NaO + H + M ⇌ NaOH + M have the most significant influence on the combustion processes. The results of present work give a theoretical foundation for application the phase change materials in H2 explosion safety industry.

Analysis of fuel storage tanks under internal deflagrations with different venting technologies: an experimental and numerical study

This study investigates small-scale fuel storage tanks subjected to internal methane-air explosions, focusing on three depressurization technologies using roof ventilation to mitigate overpressure and damage. Tests with low methane-air concentrations were conducted to generate a pseudo-static internal pressure. This approach minimized scale effects and aligned internal pressure frequency with real-scale tank behavior during deflagrations. The first prototype features a tank with a frangible roof activated by localized brittle failure of stitch welds around the roof-to-shell junction. This confirms that stitched weld patterns ensure controlled brittle failure with activation pressure estimated by a simplified equation. The second technology employs a sequential ventilation strategy, starting with a small hinged panel followed by stitch weld failure, managing low to medium-intensity explosions with the small vent alone, and allowing rapid operational recovery. In severe explosions, the hinged door facilitates earlier activation of the frangible roof, reducing the initial pressure rise rate and controlling the roof opening direction. Lastly, the study explores tanks with commercial explosion vent panels as an alternative to traditional frangible roofs, offering a practical solution for retrofitting existing tanks. Each technology enhances safety in fuel storage facilities by effectively managing internal pressures during explosive events.

Experimental Study of Turbulent Premixed Flames of Gas-to-Liquids (GTL) Fuel in a Fan-Stirred Combustion Bomb

This study experimentally investigates the turbulent flame speeds (St) of Gas-to-Liquids (GTL) fuel and a 50/50 blend with diesel across turbulence intensities (u') ranging from 0.5 to 3.0 m/s and equivalence ratios (Φ) from 0.7 to 1.3. Experiments were conducted using a cylindrical fan-stirred combustion bomb at an initial temperature (Ti) of 463 K and atmospheric pressure under near homogeneous and isotropic turbulence (HIT) conditions. A pressure transducer measured the St of the propagating GTL flame. High-speed imaging reveals that changes in flame brightness are associated with variations in flame temperature and soot incandescence. Compared to diesel, stoichiometric GTL and the 50/50 diesel-GTL blend showed peak combustion pressure reductions of 8.9% and 4.9%, respectively. Rich diesel fuel and lean GTL exhibited higher pressure rise rates, flame propagation, and St due to their Lewis numbers (Le) being less than one, enhancing flame-turbulence interaction. At u` of 0.5, 1.5, and 3.0 m/s, St for GTL increased by approximately 3.6%, 5.3%, and 2.8%, respectively, when compared to diesel, with these increases observed at Φ < 1.1. Transition from wrinkled to corrugated flamelets with increasing u` supports models predicting flame stability and potential industrial combustion efficiency improvements. Comparisons with numerical St results using the Zimont Turbulent Flame Speed Closure (Zimont TFC) model showed good agreement at lower (u' = 0.5 m/s) and mid-range (u' = 2.0 m/s) turbulence intensities but discrepancies at higher intensities (u' = 3.0 m/s), highlighting the need to refine numerical models for more accurate predictions across all turbulence levels.

Investigation on the inhibition effect and mechanism of hydrogen explosion by 2-bromo-3,3,3-trifluoropropene

This study investigated the effect of 2-bromo-3,3,3-trifluoropropene (2-BTP, C3H2BrF3) on hydrogen explosion behavior through a combination of experiments and simulations. The maximum explosion pressure (pmax), maximum pressure rise rate ((dp/dt)max), and critical inhibition concentration (CIC), across different equivalence ratios (Φ) and inhibitor concentrations (V), were obtained via experiments. The changes in adiabatic flame temperature, mole fraction of active radicals and sensitivity coefficient throughout the reaction were analyzed using CHEMKIN. The fuel-like properties of 2-BTP and the carbon monoxide (CO) produced by decomposition led to a promoting effect on the lean hydrogen explosion, primarily due to the elementary reactions R31, R806 and R882. When Φ≥1.0, the capture of active radicals via elementary reactions such as R908, R1507, and R88 was enhanced, resulting in the dominance of inhibition and a corresponding inhibitory effect. Notably, 2-BTP exhibited an inhibitory effect for (dp/dt)max at any equivalence ratio. The CIC decreased from 10% to 4% when increasing equivalence ratios from 0.6 to 2.0. This work provides crucial data and a theoretical foundation for the prevention and control of hydrogen explosions.

Effect of ignition timing and hydrogen injection phase on HDI engine combustion and NOx emissions

ABSTRACT In order to improve the ITE and reduce NOx emissions in direct-injected hydrogen (HDI) engines under at medium and high loads, the effects of IT and hydrogen injection phase on the combustion and NOx emission characteristics of the HDI engine at high rpm and medium load were investigated numerically. The base engine is a four-cylinder turbocharged direct-injected gasoline (GDI) engine, which is modified into a HDI engine with direct-injected hydrogen fuel. The simulation is performed using GT-Power software. The operating condition of HDI engine is set to 5500 rpm and 50% load. Firstly, IT is optimized, and then based on the IT optimization results, the hydrogen injection phase is optimized. The results show that as the IT is advanced, the maximum pressure rise rate (MPRR) shows a gradual increasing trend, while the combustion intensity and the indicated thermal efficiency (ITE) increases firstly and then decreases, and the former reaches a maximum value at 25° CA BTDC, while the latter reaches a maximum value of 40.5% at 18°CA BTDC. In addition, the nitrogen oxide (NOx) emissions decrease as the IT is delayed. Based on 18°CA BTDC of IT, the results indicated that the later the moment of hydrogen injection, the higher the MPRR, resulting in the greater the knock intensity. The ITE is less affected by the hydrogen injection phase. When the hydrogen injection phase is delayed, NOx emissions increase slightly.

Investigation on decelerated propagation of hydrogen-air premixed flames in confined space

This study investigates the flame propagation characteristics of hydrogen-air mixture explosion in confined spaces through a small-scale experiment and simulations, in which the experiment were conducted at normal temperature and pressure, covering a wide range of equivalence ratios (0.8-3.5) to obtain flame evolution and propagation velocity. The results indicate that enhanced thermal-diffusive instability leads to an increased cellular structure in hydrogen-air flames, with flame propagation speed increasing with radius enlargement; the numerical simulation results demonstrate that flame propagation speed is generally divided into acceleration, deceleration, and weak rebound phases; flame deceleration is mainly caused by increased pressure and wall constraints. The flame deceleration critical radius (Rcr) exhibits a trend of initially decreasing and then increasing with increasing equivalence ratio, primarily due to the influence of the pressure rise rate, while the magnitude of the deceleration factor is not directly related to the equivalence ratio. Additionally, an empirical formula summarizing the relationship between flame propagation speed during the deceleration phase, laminar burning velocity, and pressure is as follows: v=2.7∙SL0∙(P/P0)-0.48.

Cardioprotective Action of the JNK Inhibitor Tryptanthrin Oxime in the Late Period after Myocardial Infarction.

In experiments on Wistar rats, the effect of a new selective JNK inhibitor tryptanthrin oxime (TR-Ox) on parameters of systemic hemodynamics, cardiohemodynamics, and post-infarction fibrosis was studied 4 months after acute myocardial ischemia (1 h) followed by reperfusion. TR-Ox was administered intraperitoneally at a dose of 12 mg/kg 20 min before reperfusion, and then once a day for the next 4 days. Administration of TR-Ox to animals in the acute phase of myocardial infarction contributed to more complete preservation of myocardial viability in the delayed period: a relative increase of muscle elements proportion in the scar, a decrease in the formation of connective tissue areas with complete and >50% replacement of the myocardium, and deceleration of fibrotic scarring in myocardium areas distant from the focus of injury, resulting in improved systolic and diastolic myocardial function. Four months after myocardial infarction, significant improvement in systemic hemodynamics and cardiohemodynamics parameters was observed in the group treated with TR-Ox: stroke volume, cardiac output, left ventricular systolic pressure, maximum rates of left ventricle pressure rise and fall significantly increased and the left ventricle end-diastolic pressure decreased in comparison with the corresponding parameters in the control group.