Pressure Rise Rate Research Articles

Study on flame propagation of H2/LPG premixed gas in a tube

This work aims to is to study the flame propagation characteristics of the hydrogen/liquefied petroleum gas (LPG) premixed gas in a closed tube. With the aid of a self-developed square glass explosion tube and a high-speed camera, the characteristic parameters (i.e., flame structure, flame tip speed, maximum explosion overpressure, maximum rate of explosion pressure rise, deflagration index) were obtained and analyzed the explosion characteristics of the premixed gas. The results show that the time for the flame to reach the end of the pipe decreased, and the maximum explosion overpressure increases as the hydrogen addition ratio increases. However, the explosion overpressure and flame propagation velocity increased slowly when the hydrogen addition ratio was less than 40%, While the explosion overpressure and flame propagation velocity increased drastically in the range of hydrogen addition ratio 40–80%. Therefore, the key turning point for LPG hydrogenation is when the hydrogen volume fraction is 40%. The peak explosion flame propagation velocity and the peak explosion pressure showed the change law of increasing first and then decreasing with the equivalent ratio increasing. The Pmax and Vmax are 6.4 bar and 71.2 m/s respectively. The explosive flame structure of the premixed gas formed a "multiple tulip" structure after the typical tulip flame structure due to the influence of hydrodynamic. In addition, the propagation law of H2-LPG-Air premixed flame in the pipeline was influenced by the interaction of pressure wave and flame front velocity, and Pmax trajectory and Vmax curve showed similar oscillation law. Hence, the study provides crucial data for the prevention and control of H2-LPG-Air gas mixture combustion and explosion accidents.

Experimental study on the multi-level suppression of N2 and CO2 on hydrogen-air explosion

The multi-level suppression of the hydrogen-air explosion by non-premixed N2 and CO2 in a closed duct was experimentally investigated. The multi-level suppression effect of inert gas on hydrogen-air explosion was discussed by comparing explosion parameters such as explosion pressure, the rate of pressure rise, combustion duration and flame propagation. The results showed that the inert gas adjacent to the explosion zone played a major role in explosion suppression. Compared to single-level explosion suppression, the multi-level explosion suppression was not obvious for inhibitors on the same side, while the multi-level explosion suppression was most efficient for inhibitors on different sides. Moreover, the turbulent development of the flame would exacerbate the explosive reaction, which could not be avoided. The experiment in this paper had great practical significance, and the experimental results could provide data support and theoretical guidance for the safe utilization of hydrogen and the effective suppression of hydrogen-air explosion.

Laminar combustion characteristics of methane/methanol/air mixtures: Experimental and kinetic investigations

Methanol has been studied to solve the problems of insufficient combustion and unstable operation of natural gas engines. To explore the influence of methanol addition on natural gas/air mixture, the laminar combustion characteristics of stoichiometric methane/methanol/air mixture with methanol volume fractions of 0–100% are measured in a constant volume combustion chamber under the initial pressures of 1–4 bar and initial temperatures of 353–393 K. The experimental results show that the laminar combustion characteristics are linearly enhanced by methanol addition. When the methanol volume fraction varies from 0% to 100% at 393 K and 4 bar, the change rates are 11.7%, 120.4%, - 28.1% and 61.7% for combustion peak pressure, maximum pressure rise rate, combustion duration and laminar burning velocity (LBV) respectively. At high pressure, the influence of methanol addition is enhanced. Chemical kinetics analysis shows that CH2OH, the intermediate product of methanol oxidation, generates HO2 through R134: CH2OH + O2<=>CH2O + HO2, which contributes from 14% to 56% to the generation of HO2, so that HO2 replaces part of the O2 to participate the reaction with H, resulting in the transformation of part of R1: H + O2<=>OH + O to R10: HO2+H<=>2OH, thereby generating more OH and promoting the reaction.

Performance evaluation of artificial neural networks for a fish oil biodiesel fueled diesel engine: Paying a pathway to sustainable energy in environmental progress

AbstractThe purpose of this study is to develop a neural networks model to predict the performance monitoring of the compression ignition engine at various injection timings (21°, 24°, 27°bTDC) using fish oil biodiesel thereby increasing the sustainability of the biodiesel and leading to greener environment. The influence of the injection timing on the engine performance, emission, and combustion are observed in a four‐stroke single cylinder, constant speed, direct injection with a rated output of 4.4 kW using fish oil biodiesel blended with diesel. Feed forward back propagation, Elman feed forward, and Cascade back propagation neural networks‐based models are created to predict the parameters like ignition delay, maximum rate of pressure rise, combustion duration, smoke, hydrocarbon, oxides of nitrogen, carbon monoxide, and carbon dioxide, brake thermal efficiency, brake specific fuel consumption, and exhaust gas temperature. Scaled conjugate gradient and Levenberg–Marquardt have been used as training functions. The predictive capability of the models is compared with each other. It is observed that Elman feed forward with trainlm is the best model with the correlation coefficient is 0.9–1 and low root mean square error. The developed artificial neural network (ANN) predicts the engine parameters with the acceptable correlation limits and proves the efficiency and precision of the model which significantly reduces the time consumption and cost incurred in real time application. Hence by using limited experimental investigations the more accurate engine performance and emissions can be determined for wider engine operating conditions using Elman feed forward ANN.

Comparative Study of Spark-Ignited and Pre-Chamber Hydrogen-Fueled Engine: A Computational Approach

Hydrogen is a promising future fuel to enable the transition of transportation sector toward carbon neutrality. The direct utilization of H2 in internal combustion engines (ICEs) faces three major challenges: high NOx emissions, severe pressure rise rates, and pre-ignition at mid to high loads. In this study, the potential of H2 combustion in a truck-size engine operated in spark ignition (SI) and pre-chamber (PC) mode was investigated. To mitigate the high pressure rise rate with the SI configuration, the effects of three primary parameters on the engine combustion performance and NOx emissions were evaluated, including the compression ratio (CR), the air–fuel ratio, and the spark timing. In the simulations, the severity of the pressure rise was evaluated based on the maximum pressure rise rate (MPRR). Lower compression ratios were assessed as a means to mitigate the auto-ignition while enabling a wider range of engine operation. The study showed that by lowering CR from 16.5:1 to 12.5:1, an indicated thermal efficiency of 47.5% can be achieved at 9.4 bar indicated mean effective pressure (IMEP) conditions. Aiming to restrain the auto-ignition while maintaining good efficiency, growth in λ was examined under different CRs. The simulated data suggested that higher CRs require a higher λ, and due to practical limitations of the boosting system, λ at 4.0 was set as the limit. At a fixed spark timing, using a CR of 13.5 combined with λ at 3.33 resulted in an indicated thermal efficiency of 48.6%. It was found that under such lean conditions, the exhaust losses were high. Thus, advancing the spark time was assessed as a possible solution. The results demonstrated the advantages of advancing the spark time where an indicated thermal efficiency exceeding 50% was achieved while maintaining a very low NOx level. Finally, the optimized case in the SI mode was used to investigate the effect of using the PC. For the current design of the PC, the results indicated that even though the mixture is lean, the flame speed of H2 is sufficiently high to burn the lean charge without using a PC. In addition, the PC design used in the current work induced a high MPRR inside the PC and MC, leading to an increased tendency to engine knock. The operation with PC also increased the heat transfer losses in the MC, leading to lower thermal efficiency compared to the SI mode. Consequently, the PC combustion mode needs further optimizations to be employed in hydrogen engine applications.

Operating Range, Performance and Emissions of an HCCI Engine Fueled with Fusel Oil/Diethyl Ether: An Experimental Study

The main disadvantages of HCCI engines are the knocking tendency at high engine loads, the challenge of the start of the combustion, control of the combustion phase, and the narrow operating range. In this study, we aimed to control the combustion processes in HCCI engines and to expand their working range by improving the fuel properties of fusel oil by the addition of diethyl ether. Thus, the variations in the in-cylinder pressure, rate of heat release, indicated mean effective pressure, start of combustion, combustion duration, CA50, indicated thermal efficiency, mean pressure rise rate, hydrocarbon and carbon monoxide emissions were investigated. It was observed that the in-cylinder pressure and rate of heat release were taken into advance and the test engine could be operated for a wider range by increasing the diethyl ether ratio in the blend. The indicated mean effective pressure increased by 67.5% with DEE40 fuel compared to the DEE80. Under the same operating conditions, HC and CO emissions decreased by 41.6% and 56.2%, in use of DEE40. Furthermore, the highest indicated thermal efficiency was obtained as 42.5% with DEE60 fuel. Maximum hydrocarbon and carbon monoxide emissions were observed with DEE80 fuel as 0.532% and 549 ppm, respectively.

Impacts of Intake Throttling on the Combustion Characteristics and Emissions of a Light-Duty Diesel Engine under the Idle Mode

Intake throttling has been verified as an effective approach to increase the exhaust temperature of diesel engines, which could benefit the catalytic efficiency aftertreatment. To better understand the influence of intake throttling on the combustion characteristics and exhaust emissions of light-duty diesel engines operating under idle mode, a light-duty diesel engine was experimentally investigated. This study is a follow-on to previous studies on the effect of throttling on light-duty diesel engine exhaust temperatures and emissions. Tests were conducted at a fixed idle speed of 1100 rpm, and the throttle position and intake manifold air pressure (MAP) were varied. The in-cylinder pressure, pressure rise rate, heat release rate (HRR), in-cylinder temperature, exhaust temperature, and regular gaseous emissions were analyzed. The results indicated that under the influence of intake throttling, the MAP decreased from 101 kPa under wide-open-throttle (WOT) conditions to 52.5 kPa under the heaviest throttling conditions, and the exhaust temperature increased from 100 °C to 200 °C, with a fuel penalty associated with the increase in the pumping indicated mean effective pressure (IMEP). The in-cylinder pressure continuously declined with decreasing MAP, while the HRR generally increased with increasing MAP. Under WOT conditions, the ignition delay decreased, while the combustion duration decreased under heavier throttling conditions. The in-cylinder temperature with throttling was higher than that under WOT conditions, and after post-injection treatment, the in-cylinder temperature exhibited an increasing trend with decreasing MAP. The CO2, CO, NOx, and HC emissions increased with increasing throttling amounts.

Experimental investigation of the control strategy of high load extension under iso-butanol/biodiesel dual-fuel intelligent charge compression ignition (ICCI) mode

Advanced combustion modes have shown the great advantages to achieve high thermal efficiency and low pollution emissions. However, lack of sufficiently control over combustion phasing of heat release under high and ultra-high engine load limits the commercial application. In this paper, an experimental investigation had been conducted to explore the control strategy under iso-butanol/biodiesel dual-fuel intelligent charge compression ignition (ICCI) mode for achieving the high engine load extension. The criteria is used to identify clean combustion under high load expansion, which the indicated thermal efficiency is 45% or higher, and nitrogen oxides (NOx) emissions should be below 400 ppm. The results show that stable and controllable ICCI operation is obtained under high and ultra-high engine load. An iso-butanol single direct injection in the intake stroke, biodiesel double direct injection strategy in the compression stroke and near top dead center, respectively, offers a very competitive pathway to expand the engine load with clean and highly efficient combustion, in which the maximum indicated thermal efficiency reaches 49.9% and NOx emissions below 100 ppm at the indicated mean effective pressure (IMEP) of 12 bar, and the maximum engine load reaches 18 bar IMEP (96% engine load). At higher engine load, lower iso-butanol energy ratio is used to reduce the in-cylinder pressure and maximum pressure rise rate, while punishes the engine thermal efficiency and emissions. With the iso-butanol energy ratio increase, the lower in-cylinder reactivity leads to the increase of incomplete combustion products. In addition, the exhaust gas recirculation (EGR) is essential on the reduction of NOx emissions, and the second biodiesel injection duration is increased with the engine load increase for the purpose of the load expansion.

Utilization of multiwalled carbon nanotubes (MWCNT) additive in HCCI engine to widen operating range

Homogenous charge compression ignition (HCCI) combustion mode is a promising technology for the future of internal combustion engines because of its high thermal efficiency. However, HCCI engines have limited stable operating range which is a major drawback. Nanoparticles usage as fuel additive provides improvement of combustion characteristics of internal combustion engines. The objective of this study is to enlarge operating range of HCCI engine. For this purpose, the effects of multiwalled carbon nanotubes (MWCNT) on combustion characteristics of an HCCI engine were scrutinized. The effects of MWCNT on engine operating range, combustion parameters, and HC and CO emissions were determined. The maximum operating range was obtained with 75 % n-heptane, 25 % ethanol, and 100 ppm MWCNT mixture. Compared to 75 % n-heptane and 25 % ethanol mixture, 75 % n-heptane, 25 % ethanol, and 100 ppm MWCNT mixture increased the operating range of engine 112 %. Furthermore, in-cylinder pressure, heat release rate, indicated thermal efficiency, and maximum pressure rise rate were increased with use of MWCNT additive. Start of combustion and 50 % heat release location was shifted to earlier crank angles. Combustion duration was shortened. HC and CO emissions were also decreased.

Effect of magnetic field on alkane gas explosions

Magnetic field has excellent development potential in the field of explosion. The authors found the suppression effect of magnetic fields on alkane gas explosions. In this paper, the effects of magnetic field on the maximum explosion pressure, rate of pressure rise, and flame propagation velocity of alkane gas have been investigated experimentally. The crucial free radicals and elementary reactions in the process of alkane gas explosions were simulated by CHEMKIN-PRO. The explosion mechanism of alkane gas under a magnetic field was revealed by a comprehensive analysis of experimental and simulation results combined with the gradient magnetic field force. The experimental results show that the magnetic field significantly reduces the maximum explosion pressure, rate of pressure rise, and flame propagation velocity of alkane gas, thus weakening the gas explosion intensity. Compared with methane and propane, the inhibitory effect of magnetic fields on ethane explosions is more substantial. In addition, from the variation law of explosion pressure and flame propagation velocity, which concluded that the magnetic field not only inhibits the propagation of shock waves, but also significantly the propagation of the light waves. Simulation results show that ·OH plays a more dominant role in the explosion of ethane than methane and propane. The magnetic field changes the trajectory of key free radicals such as ·H, ·O and ·OH by applying a gradient magnetic field force, which increases the collision between free radicals and the wall of the reaction vessel, produces the wall effect, and reduces the collision probability between free radicals. Thus, the explosion of alkane gas was inhibited. The equation for the gradient magnetic field force further demonstrates that the magnetic field has the most excellent effect on ·OH, thus presenting that the magnetic field has a more significant inhibitory effect on ethane explosions than methane and propane.

Laminar burning characteristics of bio-aviation fuel candidate derived from lignocellulosic biomass

This study investigated the laminar burning characteristics of bio-aviation fuel candidate produced from corn stover lignin via catalytic hydrodeoxygenation (HDO). The experiments were conducted at equivalence ratios of 0.7–1.4, initial pressures of 1 bar, 2 bar, and 4 bar, and initial temperatures of 443 K and 473 K. The laminar burning velocity (LBV), explosion pressure, maximum pressure-rise rate, and combustion duration were studied. The LBV was studied using the constant volume (CVM) and constant pressure (CPM) methods. The CVM results were significantly higher than that of CPM in the presence of cellular flame. In other cases, the deviations of both were within 10 %. The analysis indicated that the LBV of the bio-aviation fuel candidate at certain equivalence ratios was lower than that of Jet A-1, RP-3, and n-decane. However, the LBV of the bio-aviation fuel candidate was greater than that of n-decane in fuel rich mixtures. A 12-term power-law correlation was determined to quantify the relationship between the LBV of the bio-aviation fuel candidate and the equivalence ratio, initial temperature, and initial pressure. The maximum deviation between the experimental data and the correlation was 11.85 %, and the average deviation was 2.95 %. Finally, the effects of the initial conditions on the explosion characteristics of the bio-aviation fuel candidate were analyzed. The explosion pressure, maximum pressure-rise rate, and deflagration index were linearly and positively correlated with the initial pressure; however, the latter two were insensitive to the initial temperature. Furthermore, a quantitative correlation between the explosion characteristics and the equivalence ratio and initial pressure was determined.

On the smoothing explosion pressure curves using Savitzky-Golay method

This study reports the optimal range of window width of Savitzky–Golay method for smoothing the raw oscillating explosion evolution curves obtained in methane-air mixtures. The experiments were carried out in a closed vessel of 3.375 L at various equivalence ratios (φ=0.8−1.2) and initial pressures (P0=1.0−2.5bar). All experiments were conducted at room temperature (293 K). The optimal range of window width and the corresponding explosion characteristics (the maximum explosion pressure Pmax, maximum pressure rise rate (dp/dt)max and deflagration index KG) of each initial condition were determined. The results show that (dp/dt)max is influenced markedly by the window width, and some similar behaviors (three characteristic segments) of (dp/dt)max-window width curves are found. Besides, the optimal range of window width depends not only on the equivalence ratio but also on the initial pressure, and the representative median of each range shows a downward trend with the initial pressure. And the median is stable at 1251 points when P0 is greater than 2.0 bar at φ=0.8, while it shows a linear decrease at φ=1.0 and φ=1.2, and maybe also tends to a stable value at a higher initial pressure. Furthermore, Pmax, (dp/dt)max and KG corresponding to the optimal range of window width have perfect linear correlations with P0, verifying convincingly the correctness of the range we determined.

Simulation study on effects of EGR ratio and compression ratio on combustion and emission characteristics of PODE/methanol RCCI engine

In order to solve the problems of combustion instability and emission deterioration of reactivity controlled compression ignition (RCCI) engine under high load, the in-cylinder combustion model of polyoxymethylene dimethyl ethers (PODE)/methanol dual-fuel RCCI engine was constructed by CONVERGE software coupling with chemical reaction mechanism, and the influence mechanism of exhaust gas recirculation (EGR) ratio and compression ratio (CR) on engine performance, in-cylinder combustion and emission characteristics of PODE/methanol RCCI mode was systematically studied. Results show that with the increase of EGR ratio, the combustion phase of RCCI mode is gradually delayed, the ignition delay and combustion duration are extended, the CA50 phase is gradually delayed, the combustion temperature decreases, the mixture distribution becomes more uniform, and the combustion process becomes smoother. When the EGR ratio increases from 0 % to 30 %, NOx production is reduced by 47.3 %, ringing intensity (RI) and maximum pressure rise rate (MPRR) decreases by 1.31 MW/m2 and 0.37 MPa/°CA respectively, and brake thermal efficiency (BTE) decreases from 45.45 % to 43.19 %. With the reduction of CR, the combustion start point is gradually postponed, the peak heat release rate and combustion temperature continuously decrease, and both IMEP and BTE show a downward trend. The variation of CR breaks the trade-off relationship between NOx and soot, and improves combustion stability, but it is also limited by the BTE reduction. When the CR decreases from 17.5 to 15.5, NOx and soot production are reduced by 28.58 % and 20.1 %, RI and MPRR are reduced by 1.26 MW/m2 and 0.7 MPa/°CA respectively, and BTE decreases from 45.45 % to 44.52 %. Therefore, the CR of 16.5 is more suitable for stable operation of PODE/methanol dual-fuel RCCI engine at high load.

Improvement of the combustion, emission, and stability features of diesel-methanol blends using n-decanol as cosolvent

This research endeavored to boost the applicability of methanol in CI engines utilizing n-decanol as cosolvents. The work was split into binary phases. Firstly, the stabilities of pure methanol (M100) and hydrous-methanol (MH10), with diesel as a reference fuel, were examined applying various temperatures: 10 °C, 20 °C, and 30 °C. The findings showed that the M100-diesel and MH10-diesel combinations were unstable. Thus, n-decanol was utilized as a cosolvent. Following by the engine combustion and emissions characteristics were evaluated by manipulating three proportions of M100-diesel mixtures with n-decanol. Three mixtures comprised of 5, 10, and 15% M100 with 20% n-decanol, which are denoted as M5, M10, and M15, correspondingly. These combinations were assessed via thermogravimetric assessment, and their physicochemical properties were assessed corresponding to the ASTM. The maximum in-cylinder pressure, heat release rate, and pressure rise rate diminished by 10, 11, and 10%, respectively, for the M100/diesel/n-decanol combinations compared with the diesel oil. The brake thermal efficiency lowered by 10%, whereas the brake specific fuel consumption enlarged by 10% for the combinations compared with the diesel. NOx and smoke opacity levels diminished by about 30 and 50%, respectively, whereas the CO and UHC enlarged by about 50 and 60% for the blends compared with the diesel oil.

Features of vascular rigidity in patients with arterial hypertension in combination with chronic heart failure and senile asthenia syndrome

Objective. The aim of the study was to evaluate the features of vascular rigidity in patients with arterial hypertension (AH) depending on the presence of chronic heart failure (CHF) and senile asthenia syndrome (SAS).Design and methods. 320 patients with AH were divided into two main groups: group 1 — patients with AH and CHF (n = 161), group 2 — patients with AH without CHF (n = 159). Depending on the presence of SAS, patients of each group were divided as follows: subgroup 1A — patients with AH, CHF and SAS (n = 84), subgroup 1B — patients with AH, CHF without SAS (n = 77), subgroup 2A — patients with AH, SAS without CHF (n = 84), subgroup 2B — patients with AH without CHF and without SAS (n = 75). To identify SAS, we used the “Age is not a barrier” questionnaire and a short battery of physical functioning tests. The parameters of vascular stiffness were determined using a device for daily monitoring of blood pressure BPLab using Vasotens technology (Peter Telegin, Nizhny Novgorod). The obtained data were processed using STATISTICA 12.0 (StatSoft Inc., USA), SPSS 21.0, MedCalc (version 9.3.5.0).Results. Analysis of the effect of SAS on vascular stiffness showed that in patients with AH, CHF and SAS, compared with patients with AH, CHF without SAS, there were statistically significantly lower values of the reflected wave propagation time (RWTT) (p = 0,001) against the background of higher values pulse wave velocity in the aorta (РWVао) (p &lt; 0,001), arterial stiffness index (ASI) (p = 0,0001) and ambulatory arterial stiffness index (AASI) (p = 0,002), which indicates more pronounced vascular stiffness in patients with AH, CHF in the presence of SAS. In the group of patients with AH and SAS without CHF, compared with patients with AH without CHF and without SAS, higher values of РWVао (p &lt; 0,001) and “adjusted” index of augmentation index (AIх@75) (p &lt; 0,001) were revealed, which allows to judge the effect of SAS on the development of arterial stiffness in patients with AH without CHF. Analysis of the effect of CHF on vascular stiffness showed that in patients with AH, SAS and CHF, compared with patients with AH, SAS without CHF, statistically significantly lower values of RWTT (p &lt; 0,001) and higher values of РWVао (p = 0,024) were noted, ASI (p &lt; 0,001), AASI (p &lt; 0,001), maximum rate of blood pressure rise (dP/dtmax) (p &lt; 0,001) and AIх@75 (p &lt; 0,001). In the group of patients with AH, CHF without SAS, compared with patients with AH without CHF and without SAS, lower values of RWTT (p &lt; 0,001) and higher values of РWVаo (p = 0,004), ASI (p &lt; 0,001), AASI (p &lt; 0,001) and dP/dtmax (p &lt; 0,001), which in turn demonstrates the contribution of CHF to the development of vascular stiffness in AH patients without SAS. CS.Conclusions. In hypertensive patients over 80 years of age, the development of both SAS and CHF was accompanied by limited compliance of the aortic walls and increased vascular stiffness in the peripheral arteries. Significantly more pronounced changes in vascular stiffness parameters were noted in patients with a combination of AH, CHF and SAS compared with those in patients with AH and CHF or AH and SAS, which indicates an increase in vascular stiffness, and, consequently, a higher risk of cardiovascular diseases in this combined pathology.

Finding a way through the “misty” evaluation of the flammability and explosivity of kerosene aerosols

• JetA1 mist flammability and explosivity are assessed in a confined explosion vessel. • Influence of initial conditions on explosion sensitivity and severity is studied. • JetA1 mists with a small droplet size have a higher rate of pressure rise. • The MIE of JetA1 mist may be lower than that of vapors at low temperatures. • The vapor/liquid ratio of a mist is a key parameter of its explosion severity. In the context of assessing hydrocarbon mist ignition sensitivity and explosion severity, an original test method is proposed, focusing on kerosene JetA1 mists but is applicable to other hydrocarbons. Experiments were carried out in a modified apparatus based on the 20L explosion sphere. Fine control of the gas/liquid ratio and flow rates, the mist concentration, and the ignition energy and duration, was ensured by a specifically customized control system guaranteeing the flexibility and compliance of the test apparatus. The droplet size distribution (DSD) and the level of turbulence of the JetA1 mist cloud were first determined by an in-situ laser diffraction sensor and by Particle Image Velocimetry, respectively. The lower explosive limit (LEL), the minimum ignition energy (MIE), the limiting oxygen concentration (LOC), the maximum explosion overpressure (P max ), and the maximum rate of pressure rise (dP/dt max ) were then determined for different mist concentrations, ambient temperatures, initial turbulence levels, energies, and DSD. Tests showed that the LEL mist of JetA1 mists of an average diameter of 8 µm is around 94 g/m 3 , a value which increases to 220 g/m 3 with increasing DSD. This value also tends to decrease considerably with increasing temperatures. Moreover, at a JetA1 concentration of 125 g/m 3 , P max and dP/dt max as high as 6 bar and 192 bar/s respectively were reached, the latter increasing to about 480 bar/s at T = 60 °C. These mists were shown to be ignitable using energies as low as 200 mJ, which is lower than that of vapors at low temperatures, and a limiting concentration of oxygen of 15.8 % v/v . The potential presence of hydrocarbon mist should therefore be an element that requires reconsidering the classification of hazardous areas. Finally, to stress the influence of the vapor-liquid ratio present in the cloud before ignition on the combustion kinetics, an evaporation model based on the d 2 -law was developed estimating the evaporation time and the vapor quantity at different initial temperatures or droplet diameters. Findings were shown to be well coherent allowing the proposition of a new technique for determining hydrocarbon mist safety criteria. Finally, results have shown that JetA1 mists can ignite at temperatures below the liquid’s flashpoint under varying turbulence levels and droplet size distributions.

Influence of Synthesis Gas Composition on Internal Combustion Engine Parameters

Abstract The presented article deals with the possibility of using synthesis gas produced from municipal waste in a spark-ignition combustion engine intended for a micro-cogeneration unit. The subject of investigation is the effect of fuel composition on the internal parameters of the internal combustion engine analysed from the course of pressure in the cylinder. The analysis shows that, in general, increasing the proportion of hydrogen increases the pressure rise rate as well as the rate of heat release in the cylinder. The presented results will serve to understand the processes taking place in the combustion engine as well as the importance of the composition of synthesis gas produced from renewable energy sources in order to achieve the highest possible energy and economic evaluation in the cogeneration unit.

Dual-fuel engines fueled with n-butanol/n-octanol and n-butanol/DNBE: A comparative study of combustion and emissions characteristics

The dual-fuel combustion mode has drawn much attention due to its high thermal efficiency and low emissions. In this study, to realize the dual-fuel combustion, n-butanol was selected as the port-injected fuel (PIF); whereas two C8-biofuels, i.e., n-octanol and di-n-butyl ether (DNBE), were used as the direct-injected fuels, respectively. A comparative study between n-butanol/n-octanol and n-butanol/DNBE fueled dual-fuel engines in terms of their combustion and emissions characteristics was numerically carried out with the KIVA4-CHEMKIN code. The energy fractions of PIF varied from 0 to 0.4 at 1500 rpm and 2280 rpm. The results show that with the PIF increasing, the peak pressure and CO emissions increase, while the combustion duration gets shorter. Though adding more n-butanol contributes to a lower global fuel reactivity, the ignition delay is still shortened. Compared with the n-butanol/n-octanol engine, the n-butanol/DNBE engine exhibits a shorter ignition delay due to the high reactivity of DNBE. Also, it has a lower maximum pressure rise rate and longer combustion duration for its diffusion combustion phase. Consequently, a higher indicated thermal efficiency and much lower CO emissions are observed in the n-butanol/DNBE dual-fuel engine, with the expense of a slight increase in NOx emissions.

Analysis of Combustion Conditions for Sustainable Dual-Fuel Mixtures

The scientific contribution is focused on the analysis and optimization of combustion conditions concerning the dual-fuel mixtures. The greatest attention was paid to the temperature of intake air when a mixture of ethanol and gasoline created the applied fuel. An experimental fuel mixture was added into the intake pipe and ultra-low sulphur diesel fuel (ULSDF) was added directly into the engine cylinder using the CR (common rail) injection system. The article analysed the medium- and high-level operational engine load, whereby the engine timing parameters originally corresponded to a conventional diesel engine. The obtained results of the performed analysis showed that the temperature of intake air affected the following operational parameters: delay of ignition, pressure rise rate in the engine cylinder and the maximum level of pressure in the engine cylinder. Lower values of the intake air temperature enabled higher injection speeds for the ethanol–sustainable mixture (ESM), especially at high engine loads. An increase in the injection speed was possible due to lower charge air temperature. While there were reduced nitrogen oxide emissions, we also noted a reduction in both carbon monoxide emissions and the total amount of unburned hydrocarbon emissions.

The effect of low temperature on the explosion characteristics of a methane/air mixtures

Prevention and mitigation of unwanted explosions require knowledge of explosion characteristics. Available explosion data are not always adequate for use in a particular application. For example, predicting the behavior of gas explosions at a lower temperature should be based on the explosion data obtained at these temperatures and not atmospheric. Basic knowledge of the methane explosions at low temperatures is desirable for a thorough understanding of this gas that cannot be found in the literature. In the presented research, the methane/air deflagrations were studied in the millisecond time domain. The standard 20-L deflagration chamber was adopted to produce consistent and reproducible data for the comparison of atmospheric and low initial temperature measurements. Methane/air mixtures were studied experimentally for concentrations between 4.6 vol.% and 16.6 vol.% and two initial temperatures of 20 and −5 °C. More than three hundred and fifty pressure–time curves were recorded and analyzed. Twenty-five deflagration curves of the methane/air mixtures were studied in 20-L volume for the first time, including thirteen pressure–time curves at −5 °C. The effects of temperature on the maximum rate of pressure rise and deflagration index were investigated. The evaluated experiments’ results are the maximum pressure rise rate of 261 bar/s at −5 °C. This work allowed potential hazards involving the handling and storing of fuels. Many pieces of knowledge must be collected to advance the phenomenological understanding of low-temperature deflagrations to make realistic theoretical predictions and correlations.