Pressure Rise Rate Research Articles

Diesel-natural gas dual fuel injection strategy effects on engine ignition delay and cylinder pressure evolution

Diesel pilot high-pressure direct injection (HPDI) natural gas technology has been noticed and applied in medium and heavy-duty engines due to its outstanding economy and power performance. However, the combustion of two kinds of fuels will involve more injection parameters, which increases the difficulty of designing injection strategy and calibrating injection parameters. This paper investigates comprehensively the effects of three key engine injection parameters (injection timing, injection duration of the pilot diesel, interval of injection between diesel and natural gas) on the engine ignition delay and cylinder pressure evolution using the experimentation method, which are utilized to guide the design of injection strategy and optimize injection parameters. Results show that the maximum in-cylinder pressure and its position are determined by the injection timing of natural gas, but little affected by the injection parameters of diesel. As the injection timing advances and the duration of diesel injection shortens, the ignition delay increases. To avoid rough combustion in the cylinder, it is necessary to optimize the injection timing, injection interval, and ignition diesel injection duration to ensure that the pressure rise rate does not exceed the threshold.

Inhibition of hydrogen-air mixtures by using chemical vapor additives

Various approaches are being used for the minimization of risk related to hydrogen hazards. The present study highlights the suppression of hydrogen-air explosion using additives (bromoethane and bromopropane) through experimental and theoretical methods. The experiments were carried out with different equivalence ratios (Ф = 0.5–2) and additive contents (3–15%) at 298 K and 1 bar initial conditions. The results indicate the influence of additives on the maximum pressure-rise, minimum ignition energy and burning velocity. Theoretical study was conducted using CHEMKIN and determined the sensitivity analysis, species profile and reaction path analysis. After the explosion, pressure increases at lower additive fractions for fuel-lean and stoichiometric mixtures and decreases at higher additive contents. In fuel-rich mixtures, pressure rapidly decreases with the increasing additive contents. In the presence of additives, the relative pressure-rise rate decreases, while the time to maximum pressure-rise and ignition energy increase are irrespective of Ф. Moreover, the maximum declination of burning velocity reflects at Φ = 2 and 3% of either additive reduces the burning rate almost by half. The sensitivity coefficient decreases for the flame-promoting reactions and increases for the flame-inhibiting reactions. In such reactions, the inhibiting radicals capture the free radicals and cease the flame propagation, resulting in flame suppression. The reactions R788 (C2H5Br + OH = C2H4Br + H2O) and R834 (C3H7Br + OH = C3H6Br + H2O) have a negative reaction sensitivity coefficient that reflects the effect of suppression. The enhancement of the mole fraction of hydrogen bromide (HBr) with additive content signifies flame suppression. The effect of additives on the explosion characteristics indicates that bromopropane is more effective than bromoethane in minimizing hydrogen hazards.

Preliminary assessment of the potential for rapid combustion of pure ammonia in engine cylinders using the multiple spark ignition strategy

In pursuit of carbon neutrality, the adoption of zero-carbon fuels in internal combustion engines offers a path to zero carbon emissions. Among such fuels, ammonia (NH3) stands out as an effective hydrogen energy carrier with a higher energy density and a more advanced production-storage-transportation lifecycle than hydrogen (H2) fuel, making it a superior alternative. Nevertheless, achieving high combustion efficiencies in engine cylinders requires the use of fuels with fast flame speeds, since the time scales of the combustion event are practically milliseconds. The inherent flame speed of NH3 falls short, typically necessitating augmentation with H2. Yet, the in-situ generation of H2 from NH3 remains constrained, rendering the flame speed of NH3 less competitive against traditional fuels like gasoline and natural gas. To address the dual challenges of slow flame speed of NH3 and the difficulty of generating large amounts of H2 from NH3 onboard, this study evaluates an alternative method of accelerating the ammonia combustion in the engine combustion chamber through the use of multiple spark plugs, which is limited discussed in existing research. Numerical simulations performed in this study show that the application of the multi-spark strategy increases the mass burn rate, advances the combustion phasing, shortens the combustion duration, increases the engine power output, improves the fuel economy, and reduces the unburned ammonia emissions, all of which indicate that rapid combustion of pure ammonia is achieved in the combustion chamber. Moreover, the use of multiple spark points does not lead to a marked increase in nitrogen oxides emissions, thereby ensuring no added stress on exhaust aftertreatment systems. In addition, pure ammonia combustion appears to be very well adapted to this strategy, as evidenced by the avoidance of excessive cylinder pressures and pressure rise rates—a challenge faced by conventional spark ignition engines, given ammonia notably slower flame speed relative to conventional petroleum-based fuels. Overall, all these findings strongly support that the multi-spark ignition system presents a compelling direction for future zero-carbon ammonia engines. However, it is crucial to address design challenges to ensure that the engine head layout provides sufficient cooling, structural robustness, optimal breathing efficiency, and reliable multi-ignition events within the confined space.

Acetone and nanoparticles effect on performance and exhaust emissions of a diesel engine

This research investigated the effects of acetone and metal nano magnesium oxides (MNMgOs) on combustion and emissions in diesel engines. Tests were conducted at various load conditions at a speed of 1500 rpm. The results showed that the use of a low percentage (2 %) of acetone led to increases in instantaneous energy changes, cylinder pressures (CP), heat release rates (HRR), mean gas temperatures (MGT), and pressure rise rates (PRR). However, an increase in acetone concentration and the use of Acetone + MNMgOs resulted in a decrease in combustion parameters. Concentrations of 2 %, 5 %, and 10 % acetone reduced carbon monoxide (CO) emissions by 7.85 %, 11.35 %, and 2.23 % respectively, hydrocarbons (HC) by 10.84 %, 15.86 %, and 3.02 % respectively, and nitrogen oxides (NOx) emissions by 3.79 %, 2.02 %, and 10.25 % respectively. The combined use of acetone and MNMgOs resulted in a reduction of 1.10 % in CO emissions, 1.48 % in HC emissions, and 10.62 % in NOx emissions.

Spectroscopic verification of biodiesel synthesis from turpentine tree oil through two-step chemical reactions: investigation of the use of synthesized biodiesel and acetone as fuel additives in diesel engines

ABSTRACT In this research, the influence of acetone addition in diesel engines was assessed, examining its implications on combustion, performance, and emissions. Biodiesel was synthesized from turpentine oil via a dual-step process involving esterification and transesterification, validated through Fourier Transform Infrared Spectroscopy. Nuclear Magnetic Resonance confirmed the presence of methyl esters while Gas Chromatography-Mass Spectrometry facilitated the biodiesel component analysis. Tests on mixed fuels, conducted under varied load settings at 1500 rpm, showcased that introducing acetone to diesel escalated in-cylinder pressures, heat release rates, and gas temperatures but mitigated pressure rise rates. In contrast, its incorporation in the diesel/biodiesel blend revealed a decline in the aforementioned parameters and an enhancement in pressure rise rates. Specifically, diesel with acetone yielded a 2.72% and 8.07% reduction in brake specific fuel consumption and carbon monoxide emissions, respectively. However, brake thermal efficiency marginally elevated by 0.01%, accompanied by a 4.19% surge in nitrogen oxide emissions. Incorporating acetone in the diesel/biodiesel blend led to a 1.13% reduction in brake thermal efficiency and a notable 7.53% cut in nitrogen oxide emissions, while brake specific fuel consumption and carbon monoxide emissions rose by 1.14% and 3.61%, respectively. These effects of acetone necessitate additional research to explore its potential as an additive.

Study of water injection on suppressing knock in a high compression ratio and supercharged hybrid gasoline engine

This study investigated the effects of a direct water injection from both macroscopic characteristics and chemical kinetics aspects in high compression ratio engines, specifically regarding knocking concerns. On the one hand, −80 °CA is thought to be the ideal water injection timing (WIT) in terms of lowering mixture temperature, knock suppression, and water droplet dispersion. The mixture temperature is lowered to below 760 K by −80 °CA of WIT. When ignition timing (IT) is maintained at 2 oCA or −3 oCA, respectively, the water-fuel ratio (WFR) of 0.4 and 0.6 is the threshold for the impact of water droplet mass on combustion. The knock intensity decreases with increasing water-fuel ratio, and the pressure rise rate threshold of 0.6 bar/°CA is a knock-occurrence criterion. On the other hand, spontaneous combustion of end mixtures first occurs beneath the exhaust valve, transporting burned gases and raising temperatures. The IC4H7 concentration is higher in the mid-to-high temperature areas near the cylinder liner. Elevated concentrations of CH2O indicate high-temperature reactions, while increased levels of CH3 and HCO signify auto-ignition onset. Whether the IT is 2 oCA or −3 oCA, both IC4H7 concentration and OH concentration observe a declining trend with the increase of WFR.

Evaluation of a pressure sensing glow plug in terms of its application possibility to control the combustion process of a hydrogen-powered spark-ignition engine

The article contains the results of an analysis of the suitability of a pressure sensing glow plug for use in a hydrogen engine control system. Due to the properties of hydrogen, the process of its combustion in spark-ignition engines is significantly different from the classic fuels. It is planned to use the pressure sensor signal to control the combustion process to obtain high power and efficiency, with the lowest possible emission of nitrogen oxides, which is the main harmful component of hydrogen engines. After an initial assessment of suitability, it was decided to use a pressure sensing glow plug. This choice is dictated by the low price, good availability and high durability of these sensors. The preliminary tests were carried out using a low-power single-cylinder SI engine coupled with a 48V generator. The tests were carried out for several values of engine speed and load of the generator and for classic gasoline with a research octane number (RON) of 95. In order to obtain an increased pressure rise rate in the cylinder, as for hydrogen fueling, the engine operation was also tested with unmodified light gasoline used as solvent, which is characterized by a significantly lower RON value. The use of a reference pressure sensor in the cylinder made it possible to determine the behavior of the PSG in various operating conditions. The tests revealed that the differences in the pressure waveforms registered with both sensors can be systematized depending on the engine speed and its load.

Prognostic implications of invasive hemodynamics during cardiac resynchronization therapy: Stroke work outperforms dP/dtmax

Invasive measurements of left ventricular (LV) hemodynamic performance can evaluate acute response to cardiac resynchronization therapy (CRT). The study sought to determine which metric, maximum rate of LV pressure rise (LV dP/dtmax) or LV stroke work (LVSW), is more strongly associated with long-term prognosis. CRT patients were prospectively included from 3 academic centers. Invasive pressure-volume loop measurements during implantation were performed, and LV dP/dtmax and LVSW were determined at baseline and during biventricular pacing (BVP) as well as their relative increase (%Δ). Hazard ratios (HRs) for the primary outcome of 8-year all-cause mortality were derived using Cox proportional hazards. The secondary endpoint was echocardiographic response, defined as 6-month LV end-systolic volume reduction ≥15%. Paired data from 82 patients were analyzed (67% male; age 66 ± 9 years; QRS duration 158 ± 22 ms, median survival time 72 months). Survival was better when LVSW during BVP was ≥4400 mL∙mm Hg (HR 0.21, 95% CI 0.08-0.58, P < .003) or when ΔLVSW% was ≥10% (HR 0.22, 95% CI 0.08-0.65, P=.006). In multivariate analysis, following direct comparison of continuous measures of acute ΔLV dP/dtmax% and ΔLVSW%, only ΔLVSW% remained associated with the primary endpoint (HR 0.982 per percentage point, P = .028). In contrast to LV dP/dtmax (all P > .05), significant associations with echocardiographic response were found for stroke work during BVP (area under the receiver-operating characteristic curve 0.745, P = .001) and ΔLVSW% (area under the receiver-operating characteristic curve 0.803, P < .001). Stroke work, but not LV dP/dtmax, is consistently associated with long-term prognosis and response after CRT. Our results therefore favor the use of stroke work as the hemodynamic parameter to predict long-term outcome after CRT.

Experimental investigation on the explosion characteristics and flame propagation behavior of aluminum hydride dust

Aluminum hydride (AlH3) dust is a high-capacity hydrogen storage material but is prone to explosion. In this paper, explosion characteristics and flame propagation behavior of AlH3 dust are investigated. The results indicate that the exposure of bare aluminum and the increase of specific surface area lead to the maximum explosion pressure of AlH3 dust being 4 times higher than that of Al dust. The enhancement of heat transfer by hydrogen combustion causes a higher combustion rate, leading to a higher maximum explosion pressure rise rate and flame propagation velocity of AlH3 dust. The thermo-diffusive instabilities and the evolution of hydrogen result in a pulsation flame propagation velocity of AlH3 dust. Combining the explosion temperature calculated by NASA CEA with the explosion residues analysis, the explosion mechanism of AlH3 dust is further revealed. The break of the oxide film and the combustion of hydrogen result in a different explosion mechanism.

Quantitative investigation of explosion behavior and spectral radiant characteristics of free radicals for syngas/air mixtures

The combustion characteristics and explosive hazard of syngas (H2/CO)/air mixtures are affected by its exact composition and equivalence ratios. In this paper, the explosion pressure and spectral radiant intensity of free radicals were quantitatively examined for syngas with different H2 proportions ([H2 in syngas] = 0, 30, 50, 70, 100 vol%) and equivalence ratios (φ = 0.8, 1.0, 1.2, 1.4, 1.6, 2.0, 2.5). The results show that the explosion process of syngas/air mixtures can be separated into the initial slow combustion stage, the violent deflagration stage and the deflagration ending stage. The peaks of explosion pressure, pressure rise rate, OH*spectral intensity and rise rate of spectral intensity first increase and then decrease with increasing the equivalence ratio, and they reduce gradually with the decrease of H2 proportion in syngas. The H2 content in syngas greatly affects the heat release and the concentration of excited state OH*, especially for the syngas/air mixtures with smaller proportion of H2. Additionally, the presence of H2 greatly increases the deflagration index and spectral radiant index of OH* for syngas/air mixtures. The average rise rates of explosion pressure and spectral intensity of free radicals are introduced and the coupling model between them is established based on the first law of thermodynamics and the principle of chain reaction. The established model is furthermore verified by the experimental results. It is indicated that there is a linear relationship between average rise rates of explosion pressure and spectral intensity (OH*). The results can be used to improve the combustion efficiency of syngas and to guide theoretically the prevention, mitigation and control of syngas explosions.

A computational parametric study of ducted fuel injection implementation in a heavy-duty diesel engine

Experiments have shown that ducted fuel injection (DFI) effectively reduces soot emissions from direct-injection diesel engines. Although many computational studies have evaluated DFI’s spray development and soot reduction mechanisms in constant volume chambers, only limited computational work on internal combustion engines exists. The DFI duct assembly changes the engine’s in-cylinder flow, spray, and combustion development. Therefore, current production engine designs might not be optimal for achieving the best engine performance with DFI. This work conducted an extensive numerical study to evaluate how parameter changes affect DFI performance. The parameters include swirl ratio, piston geometry, compression ratio (CR), number of injector orifices, split injection strategy, and exhaust gas recirculation (EGR) in a heavy-duty diesel engine utilizing DFI. The combustion and soot emission data from the Sandia compression ignition optical research engine were used for model validation. Simulations showed that an increased swirl ratio resulted in more intense jet flame-piston interaction, slowing down the combustion heat release during the late combustion stage and leading to lower indicated thermal efficiency (ITE) due to higher exhaust losses. A piston-bowl design with a reentrant inner piston edge yielded the highest thermal efficiency, due to the reduced cylinder head heat transfer loss. Additional injector orifices led to higher efficiency owing to a more advanced combustion phasing. Nevertheless, the maximum pressure rise rate (MPRR) and oxides of nitrogen (NOx) emissions also increased with the number of injector orifices due to more rapid heat release and higher combustion temperature. Implementation of a split injection strategy combined with a higher EGR rate effectively inhibited the excessive MPRR and NOx formation. In general, the study concluded that DFI is not sensitive to most parameter changes but will benefit from future parameter optimization.

A comparative investigation of the explosion mechanism of metal hydride AlH3 dust and Al/H2 mixture

Aluminum hydride (AlH3) is an excellent hydrogen storage material, whereas hydrogen is easily released because of the low-temperature dehydrogenation characteristic. Therefore, the explosion mechanism of AlH3 dust is explored by comparison with the Al/H2 mixture. The findings indicate that since the residual aluminum after hydrogen evolution combusts more completely, AlH3 has a higher explosion pressure value than Al/H2 mixture. However, the explosion pressure rise rate and average flame propagation velocity of AlH3 dust are lower than those of Al/H2 mixture. It is attributed to the initial free hydrogen state and initial higher hydrogen concentration of Al/H2 mixture. The key radicals that generate main explosion residues Al2O3 are AlO and O. AlH3(+M) ≤> AlH + H2(+M) has the greatest sensitivity on the formation of O and AlO. Hydrogen combustion expedites the phase transition process of aluminum dust, while their competition for oxygen is not conducive to the formation of Al2O3.

Investigations on methyl pentanoate-air mixtures confined explosion and cellularity

Combustible fuels like methyl pentanoate (MPe) could cause accidental explosions and fire. Therefore, MPe explosion characteristics have to be well characterized and understood for its safe and reliable use in industries and combustion devices. Considering this, MPe’s explosion pressure, maximum explosion pressure, rate of pressure rise, maximum rate of pressure rise, heat release rate, etc., were investigated in this study at the initial conditions of 1, 2, and 4 bar and 423 K, 453 K, and 483 K using the equivalence ratios of 0.7–1.4. The maximum explosion pressures and maximum rate of pressure rise of MPe increased as the initial pressures increased but the maximum rate of pressure rise was insignificantly affected by the initial temperature. The explosion duration decreased with a decrease in the initial pressure. The maximum heat release rate and deflagration index increased with increasing initial pressure. The MPe maximum deflagration index was 224.8 bar•m/s, which occurred at a higher initial pressure and fuel-rich mixture. Therefore, the explosion severity of MPe was enhanced at higher initial pressures and fuel-rich mixtures. Moreover, the flame cellularity study showed that MPe unstable flame crack length and cell number were more affected by increments in the initial pressure and equivalence ratio. Therefore, flame instability and cellularity would significantly influence explosion severity at higher pressures and equivalence ratios. This study’s findings provide first-hand data that could be used to further investigate and characterize MPe’s explosion risk.

Explosion mechanism of nano-sized dust cloud in interconnected vessels

The effect of pipe diameter and volume ratio on overpressure characteristics and flame propagation behavior of nano-sized PMMA dust in interconnected vessels is investigated in this study. To reveal the explosion mechanism of nano-sized dust clouds in interconnected vessels, a model to predict the pre-compression level of turbulence and choking flow is established. The results show that the dust explosions in interconnected vessels go through three stages: the forward flow of the medium, the violent combustion of the pre-compressed dust cloud, and pressure oscillations. Due to changes in the geometry of the pipe inlet, the flame front is stretched and accelerated propagates. The loss of kinetic energy and the suspended acceleration of the flame front depend heavily on the diameter of the pipe. The increase in volume ratio significantly enhances the explosion intensity in the second vessel. Particularly, for a pipe diameter of 40 mm, the maximum explosion overpressure with a volume ratio of 6 is 2.6 times that of a 1/6 volume ratio, and the maximum pressure rise rate is 10.14 times higher. The prediction model accurately predicts the pre-compression in the second vessel, which supports the safety design of interconnected vessels in industrial processes.

Combustion cycle-to-cycle variations of opposed-piston two-stroke gasoline direct injection engine

The combustion characteristics and cycle-to-cycle variations of opposed-piston two-stroke (OP2S) gasoline direct injection (GDI) engine are investigated with experiment. The effects of engine speed on the combustion process and cycle-to-cycle variations are discussed. This paper chooses the indicated mean effective pressure, the maximum cylinder pressure and the maximum pressure rising rate to characterize the combustion cycle-to-cycle variations. The heat release rate of OP2S-GDI engine is in accordance with the conventional gasoline engine, which is divided into flame developing period, rapid burning period and after burning period. With the increase of engine speed, the maximum combustion pressure and maximum pressure rise rate decrease, and the time corresponding to the maximum in-cylinder pressure is delayed. The pressure rise rate associated with different engine speeds all show an increasing trend, with maximum values less than 0.2 MPa/°CA. The peak value of instantaneous heat release rate in the combustion process decreases and the combustion amount in the post-combustion period increases as the engine speed increases. The cycle-to-cycle variation rate of indicated mean effective pressure (IMEP) increases as the engine speed increases. The maximum IMEP cycle-to-cycle variation rate is 6.101% at 4000 rpm, which is less than the traditional gasoline engine cycle-to-cycle variation rate (10%). The cycle-to-cycle variation rate of the maximum cylinder pressure ( pmax) increases as the engine speed increases. The pmax cycle-to-cycle variation rate is 1.083% at 4000 rpm, which is less than traditional gasoline engine cycle-to-cycle variation rate (2%). The R ( pmax, pi) is weakly correlated at 2000 rpm and uncorrelated at 3000 rpm and 4000 rpm. The R( θ( pmax), pi) is strongly correlated at 3000 rpm and uncorrelated at 2000 rpm and 4000 rpm. The cycle-to-cycle variation rate of the maximum pressure rise rate (d p/d φ) is 7.406%%, 7.919% and 7.667% respectively at 2000 rpm, 3000 rpm and 4000 rpm. The R ((d p/d φ) max, pi) is weakly correlated at different engine speed, the R( θ(d p/d φ) max, pi) is moderately correlated at 2000 rpm and positive correlation at 3000 rpm and 4000 rpm.

Effect of nanoparticles (Al2O3 and CeO2) blended with biodiesel on combustion, performance, and emissions of a diesel engine

The increase in the utilization of fossil fuels in almost all the energy production sector badly impacts the environment because of incomplete combustion. The incomplete combustion of fuels releases soot, unburned hydrocarbon, and greenhouse gas emissions, contributing significantly to climate change. In the current experimental work, the evaluation of the effect of the addition of aluminium oxide (Al2O3) and cerium oxide (CeO2) nanoparticles in Jatropha biodiesel (B20) has been performed on the combustion, performance, and emission characteristics of compression ignition engine. These nanoparticles have been added because they have a large surface area-to-volume ratio. The air-fuel mixture and the evaporation rate are enhanced, leading to improved burning. The increase in brake thermal efficiency has been observed with nanoparticles blended fuel, i.e. (B20 + 30 ppm Al2O3 + 30 ppm CeO2) by 9.354%. In contrast, drop-in oxides of nitrogen, carbon monoxide, HC, and smoke opacity emissions were observed by 24.67%, 33.33%, 23.08%, and 34.01%, respectively, compared with pure biodiesel. Using nanoparticles in Jatropha methyl ester reduces ignition delay, increases combustion duration, and starts earlier combustion, reducing heat release rate, cylinder pressure, and pressure rise rate by 10.53, 1.994, and 3.687%, respectively, as compared to the B20 blend.

Experimental and reaction kinetics studies on deflagration characteristics of liquefied petroleum gas-air mixture with different compositions in confined space

To assess the hazardous impact of liquefied petroleum gas (LPG), this study investigated its macro–micro deflagration characteristics under various compositions and equivalence ratios using a 20 L spherical experimental apparatus and CHEMKIN-Pro kinetic software. The findings are as follows: when the equivalence ratio was 1.2, the LPG exhibited peak values for the maximum explosion pressure (pmax), maximum explosion pressure rise rate ((dp/dt)max), deflagration index (KG), and average flame propagation velocity (v). Furthermore, the (dp/dt)max, KG, and v increased with increasing the proportion of C3H8. In the LPG chain reaction, the most influential steps in terms of promotion and inhibition were R1: H + O2 = O + OH and R104: 2CH3(+M) = C2H6(+M), respectively. C2H4 gradually accumulated during the chain initiation phase and rapidly depleted as the temperature sharply increased. Hence, to effectively inhibit LPG explosion, it is recommended to develop inhibitors capable of eliminating reactive radicals (such as H*, O*, and OH*) and targeted inhibitors that specifically inhibit the reaction involving C2H4. Additionally, augmenting the C3H8 proportion in LPG can mitigate the emission of toxic and harmful gases, such as CO and CO2. This study has significant theoretical and practical implications for the safe, environmentally friendly, and efficient use of LPG.

Effect of direct injection of small amounts of ethanol on port-injected hydrogen internal combustion engines

Hydrogen is a renewable fuel with excellent combustion characteristics. However, the direct use of hydrogen in existing engines faces obstacles such as abnormal combustion and high NOx emissions. This study proposes a strategy for controlling the combustion and emissions performance of a port-injection (PI) hydrogen internal combustion engine using ethanol direct injection (DI). The test conditions are 1000 rpm, 1500 rpm, and 2000 rpm respectively, the excess air coefficient is 1, 1.5, and 2, and 3%, 6%, and 9% ethanol is added. The results showed that the addition of ethanol can significantly reduce the pressure rise rate of the hydrogen engine and prolong CA0-10 and CA10-90. The addition of ethanol can promote the BMEP and BTE of the hydrogen engine. The addition of ethanol can reduce NOx emissions under lean burn conditions by 18%. The disadvantage is that the addition of ethanol increases the hydrocarbon emissions of hydrogen engines by about 50%, but the total amount is less. After the addition of ethanol, the flashback phenomenon of the hydrogen engine was significantly improved.

Experimental Study of the Explosion Characteristics of Energy-Containing Materials Nto’s Lead Salt Dust

ABSTRACT The explosion characteristics of NTO’s lead salt as an energy-containing material are significantly different from those of ordinary dust. In order to systematically recognize its hazards in the production, storage, and transportation processes, the lower limit of explosion concentration, explosion pressure, pressure rise rate, and minimum ignition energy were systematically studied using the self-made 5 L column-type dust explosion test system and the modified 1.2 L steel Hartmann tube, respectively. The findings demonstrate that the explosion pressure and pressure rise rate gradually increase with the dust concentration; compared with ordinary dust, there is no maximum explosion pressure; the pressure rise rate has an inflection point of 550 g/m 3 , and if the concentration is greater than 550 g/m 3 , the pressure rise rate increases sharply. The explosion pressure is only slightly influenced by the pressure of powder spraying, which is inversely related to the rate of pressure rise. Contrary to the typical tendency of ordinary dust, where the ignition energy initially reduces and then increases with increasing concentration, the ignition energy tends to decrease as the dust concentration increases. As electrode spacing grows, the ignition energy tends to rise, and as concentration rises, the influence of electrode spacing progressively declines.

Performance evaluation of a diesel engine fueled with Chlorella Protothecoides microalgal biodiesel

The main objective of the current study is to determine the engine performance, combustion, and emission analysis of compression ignition engines fuelled with Chlorella Protothecoides microalgal biodiesel (CPMB). The biodiesel was derived from Chlorella Protothecoides microalgal oil (CPMO) through transesterification. Under the specified conditions, which included a methanol-to-oil molar ratio of 7.41 (vol/vol), a reaction time of 105.6 min, a reaction temperature of 65 °C, and a catalyst concentration of 1.024 (% wt/vol) and achieved a biodiesel yield of 98.1%. The fuel properties were determined using standard methods, revealing that the density and kinematic viscosity of CPMB were significantly higher than those of diesel. However, CPMB still exhibits satisfactory fuel properties that meet most biodiesel specifications. CPMB boasts a low cloud point (CP) and pour point (PP) of 0 and -3 °C, respectively, indicating its effective usability in cold climates. The oxidation stability of CPMB, determined by the modified Rancimat method, was found to be 4.6 h, satisfying ASTM specifications. The fuel tested in this study was 20% biodiesel with diesel, 100% biodiesel, and neat diesel. These fuels had been tested on a CI engine in which the engine speed and compression ratio were fixed at 1500 rpm and 18:1, respectively. Based on the results, it is found that the indicated thermal efficiency decreases up to 3.68% and 8.22% with B20 and B100 as compared to diesel. However, mechanical efficiency, volumetric efficiency, and indicated power were estimated to be higher at peak engine load conditions when correlated with neat diesel. Furthermore, the mean effective pressure for B20 and B100 was estimated to be decreasing while the mass fraction of fuel burnt and the rate of pressure rise increased compared to diesel at peak load conditions. For exhaust emission analysis, a significant reduction was recorded in CO and UHC emissions, while NOX emission increases at peak engine loads. From the above results, it is accomplished that the performance of B20 blends is nearly identical to diesel, and it can be recommended to be used in engines without any modification.