Combustion Duration Research Articles

Evaluating the potential performance of methane in lean conditions and examining the variations in combustion in a gasoline direct injection engine

The present work investigates the effect of methane addition on a direct injection spark-ignition engine's performance, combustion, cycle-to-cycle variation, coefficient of variation, and emission characteristics. Equivalence ratio of the engine is varied from λ = 1.0, 1.02, 1.08, 1.15, and 1.22. Methane addition for the equivalence ratios (λ = 1.0, 1.02, and 1.08) close to the stoichiometric condition does not support the methane addition. Decrease in peak pressure is seen in minimum to the maximum methane addition of 19.5 %. Adding the gaseous fuel to the intake manifold causes charge displacement, as the fuel is inducted at the suction top dead center. This effect is consistent with the increase in flame initiation and combustion durations. The same methane addition fraction for the equivalence ratios of λ = 1.15 and 1.22 provides better combustion stability and efficiency. The peak pressure attainment for λ = 1.22 is a 25 % increment with the maximum methane addition. Emission formation of carbon monoxide and unburnt hydrocarbons drops as the fuel is leaner towards λ = 1.22, even with the addition of methane. The oxides of nitrogen emissions decrease initially for the equivalence ratio close to the stoichiometric condition but increase for the leaner equivalence ratio with the methane addition fraction.

Observations and impact of char layer formation and loss for engineered timber

The char layer plays a critical role in the fire behaviour of engineered timber. Several chemical and physical processes can reduce char layer thickness and integrity. A series of experiments studied 12 cross-laminated timber (CLT) columns (130 × 790 × 125 mm WxHxD) exposed to combined thermal (20 kW/m2 or 50 kW/m2) and mechanical loading (39 kN, eccentric). Char loss from the surface lamella was observed and the impact of this on the thermal response of the timber studied. In all cases, unprotected CLT exhibited fall-off of charred pieces. Cracking, shrinkage and movement of char contributed significantly to the exposure of underlying timber sections to external heating. There was no direct correlation between char fall-off and the measured glue line temperature in this configuration. To enable comparison between CLT with and without char fall-off, a thin layer of glass fibre-reinforced polymer was added to the exposed surface of six samples which prevented all char fall-off. Retention of the char layer significantly decreased temperatures beneath the char layer, loss of section and burning duration compared to samples with char fall-off.

An Optical Study on the Ignition and Flame Development Initiated by a Combination of Passive Pre-Chamber and Spark Ignition

ABSTRACT Pre-chamber jet ignition combined with spark ignition in main chamber has advantages in adjusting the combustion phase and improving the burning rate for spark ignition engines. In this study, optical experiments based on a constant volume combustion chamber and high-speed schlieren imaging were conducted to investigate the ignition and flame development under the combined ignition mode with a passive pre-chamber and spark plug using methane fuel. Two modes of flame development were observed with different ignition time interval of pre-chamber ignition and spark ignition (Δt ign). At relatively short Δt ign, the “jet-disturbed flame” mode occurs with a three-stage combustion process: laminar flame; flame acceleration by jet-flame interaction and re-ignition at the jet root; flame deceleration. The maximum global flame speed can be increased from 2 m/s to 9 m/s under λ = 1 and from 1 m/s to 5.5 m/s under λ = 1.3. The ignition delay is relatively short and the heat release shows a slow and multi-stage feature. Moreover, the ignition delay and combustion duration in main chamber are relatively not sensitive to the variation of nozzle diameter. As the spark ignition becomes later (longer Δt ign), the “spark-initiated turbulent flame” mode occurs. In this mode, a rapidly developing turbulent flame is initiated by the spark plug, with a global flame speed up to 16 ~ 18 m/s under λ = 1 and 6 ~ 11 m/s under λ = 1.3. Compared with pre-chamber ignition, a shorter combustion duration is obtained at certain Δt ign and misfire can be avoided because of the synergy of the combined ignition mode.

Iron powder particles as a clean and sustainable carrier: Investigating their impact on thermal output

The utilization of iron powder as a sustainable energy carrier, conducive to a carbon-free future, has garnered substantial attention due to its commendable attributes such as high energy density, widespread availability, and absence of emissions. To harness its potential optimally, a comprehensive understanding of the combustion behavior of iron powder and the development of corresponding combustion technologies are imperative. This study endeavors to investigate the influence of iron powder particle size, as well as the flow rate of air and iron powder, on the temperature at the exit of the ignition chamber. Experimental trials were conducted utilizing a metal cyclonic combustor (MC2) equipped with a system for feeding iron powder. The findings reveal that an increase in the diameter of iron particles corresponds to an elongation of the path from the ignition chamber to the outlet. Consequently, this elongation induces prolonged ignition delay time and burning duration. Notably, larger particles exhibit enhanced combustion efficiency in comparison to their smaller counterparts. The outcomes demonstrate that particles approximately 50 µm in size achieve an efficiency of 94%, as opposed to 72% for particles below 20 µm. Temperature measurements and spectrometric analysis expose a discernible relationship between particle size and temperature during combustion, elucidating that larger particles yield higher temperatures. Comprehending the intricate correlation between particle size and combustion behavior is crucial for optimizing combustion systems when utilizing iron powder as an energy carrier. By controlling particle size and combustion conditions, the efficiency and efficacy of iron powder combustion processes can be enhanced, thereby contributing to cleaner and more sustainable energy solutions. The implications of this study extend to the enhancement of burner system design and functionality, along with an overall improvement in combustion efficiency. These findings hold significance within the realm of combustion science, presenting opportunities for the development of more sustainable and environmentally friendly energy solutions. Implementing the insights derived from this research empowers researchers to harness the potential of iron powder as an energy carrier, thereby advancing progress toward a greener future through environmentally conscious combustion processes.

VOF based model of numerical simulation for single aluminum droplet evaporation and combustion

ABSTRACT This study investigates the combustion of a single aluminum droplet in a high-temperature convective setting, focusing on the interplay between the environment and droplet evaporation combustion. Using the VOF numerical method, a two-dimensional multiphase flow combustion model for micron-sized aluminum droplets is developed. Experimental validation compares predicted droplet diameter with experimental data. The combustion behavior of aluminum droplets in high-temperature convective environments is analyzed, emphasizing gas-phase combustion during stable stages. Parametric variations in flow velocity and oxygen concentration reveal the formation of vortices around the droplet, influencing aluminum vapor accumulation and evaporation rates. Combustion primarily occurs at the droplet’s windward side, with reaction rates decreasing downstream. Increasing gas velocity from 1.5 m/s to 3 m/s thins the aluminum vapor concentration boundary layer, boosting combustion rates by 35%. Elevating oxygen concentration from 20% to 50% brings the flame closer to the droplet, accelerating combustion rates by 2.7 times, suggesting oxygen concentration’s role in reaction acceleration and combustion duration reduction. This research offers insights for simulating aluminum droplets in propellant applications.

The Influence of Injector Nozzle Diameter on High-Density and Lean Mixture Combustion in Heavy-Duty Diesel Engines

In order to improve the fuel economy of heavy-duty diesel engines under high-load conditions, based on the combustion pathway model, it is proposed that the proportion of lean mixture with 0 < Φ < 1 is the most important spray characteristic affecting the overall diesel combustion process. Answering the question of how to increase the proportion of lean mixture inside the spray is the key to achieving the efficient and clean combustion of diesel engines. This paper investigated the mechanism of injector nozzle diameter on the in-cylinder air–fuel mixture and combustion process based on a high-density and lean mixture characteristic combustion strategy. The experimental results show that with an increase in nozzle diameter, the peak pressure and instantaneous heat release rate significantly increase, the combustion duration is shortened by about 20%, and the heat release becomes more concentrated. At 1200 rpm and IMEPg~2.3 MPa conditions, the indicated thermal efficiency increases by 1.3%, reaching a maximum of 51.5%. The numerical simulation results show that with the increase in nozzle diameter from 0.169 mm to 0.218 mm, the spray ejection momentum per unit time increases by 30%, the momentum transferred to the air by the spray increases, the oxygen transport process becomes more intense, and the air entrainment mass during the spray free development stage increases by 42%. The proportion of lean mixture inside the spray throughout the entire spray development process increases, resulting in an increase in the heat release rate of the lean mixture, making the overall combustion more intense and concentrated.

Enhancing Combustion Stability in Biodiesel Engines: The Plausibility of n-Butanol Injection Phasing and Reactivity-Controlled Compression Ignition–An Experimental Endeavour

This study explores the synergistic effect of injection phasing on reactivity-controlled compression ignition strategies upon the combustion and stability indices of biodiesel-fuelled single-cylinder four-stroke diesel engines. Mahua Biodiesel was used as the primary fuel, and n-butanol was injected into the manifold to achieve that strategy. The tests were conducted with varying the start of pilot-main injection timing, energy share of biodiesel in split injection and energy share of butanol. This work also entails the various combustion characteristics and the corresponding consequences on the engine’s performance-emission. Ignition delay is shortened with retarded injection timing. At the same time, combustion duration is reduced with higher butanol share and advanced injection timing of biodiesel. The butanol injection and advanced pilot biodiesel injection timing revealed the advancement of combustion phasing. In conjunction with n-butanol port fuel injection, the current study demonstrates the noteworthy and potential superiority of n-butanol as the less reactive constituent. Shortened ignition delay exhibited improved performance and UHC-CO footprint. This study highlights the maximum reduction in regulated emissions compared to operations solely relying on 100% biodiesel. The occurrence of CA50 at 5°–7° CA revealed a maximum decrease in NOX-UHC-CO-CO2 emissions compared to the B100 fuelled strategy. The reduction percentages observed were 53.4%, 97%, 81.1%, and 53.2%, respectively.

Thermal decomposition and combustion of interior design materials

Research findings on the patterns of thermal decomposition and combustion are reported for widely used interior design materials. The experiments were conducted using a hardware and software system including a thermogravimetric analyzer (to record the characteristics of thermal decomposition), a gas analyzer (with H2, CH4, H2S, SO2, CO and CO2 sensors) and a high-speed camera (to record the characteristics of ignition and combustion). The temperature of the oxidizing medium ranged from 500 to 900°C to investigate the conditions of thermal decomposition initiation and sustained combustion. It was established that the highest concentrations of toxic emissions were typical of the combustion of polypropylene at a maximum temperature of the oxidizing medium (900°C). Wood showed the shortest ignition delay time and the longest duration of combustion. The experimental data were used for a physical problem statement and mathematical model of heat and mass transfer to explore the thermal decomposition and combustion of interior design materials in different rooms. A comparison of the experimental findings with the mathematical modeling results validates the developed model. The growth rates of carbon monoxide and carbon dioxide concentrations were determined for construction (wooden) and interior design (polymer) materials. The maximum concentrations of CO and CO2, and the minimum times taken to reach their threshold values corresponded to wood and polyvinyl chloride panels. This research provides a deeper insight into the thermal decomposition of a wide range of fuels and the formation of gaseous pyrolysis products of these fuels. The results obtained can be used to evaluate the toxicity of construction and interior design materials during compartment fires as well as to estimate the safe egress time and risks involved in the process. They can also serve as a database for the development and testing of mathematical models describing fire outbreaks and propagation in confined spaces.

Effect of excess air ratio and ignition timing on the combustion and emission characteristics of the ammonia-hydrogen Wankel rotary engine

As a hydrogen carrier, ammonia can suppress knock and enhance thermal efficiency of the hydrogen-fueled Wankel rotary engine (WRE), and achieve zero carbon emissions. This research established a three-dimensional fluid dynamics model coupled with detailed reaction kinetics of ammonia and hydrogen and verified it based on experiments. Incorporating 10% volume fraction of ammonia into the hydrogen-fueled WRE eliminates knock and decreases the excess air ratio (λ) from 1.8 to 1.4, effectively improving the indicated mean effective pressure (IMEP). The results indicate that when λ exceeds 1.4, flame propagation accelerates with higher concentration of the mixture. This enhances peak in-cylinder pressure and heat release rate, but it results higher NOx emissions. As λ varies from 1.8 to 1.4, NOx emission levels rise by 47.4%. At λ ≤ 1.2, the rapid flame propagation leads to short combustion duration, diminishing the power output. At this stage, the NO formation is dominated by H radicals, and the NOx production reaches its minimum value at λ of 1.0. In summary, the ammonia-hydrogen WRE achieves optimal performance at λ of 1.4 and ignition timing of −5 °CA after top dead center, the indicated thermal efficiency reaches 36.9% and the IMEP achieves 0.683 MPa.

Combustion characteristics of RP-3 aviation kerosene/n-butanol blended fuel in a compression ignition engine

In order to meet the requirements of Sustainable Aviation Fuel (SAF) to achieve the imperatives of energy conservation and emission reduction. This paper compares the combustion characteristics of diesel, RP-3/n-butanol blends in terms of heat release rate, in-cylinder pressure, temperature and fuel economy in a compression ignition engine, taking into account the advantages of lightweight structure, low fuel consumption and wide range of applications of aviation piston engines. The results certified the viability of applying RP-3 and RP-3/n-butanol blends in diesel engines. Adding n-butanol prolonged the ignition delay and shorten the combustion duration. Moreover, the peak of the pressure, temperature and apparent heat release rate (AHRR) increased. In addition, the blended fuel showed obvious diffusion combustion characteristics at high load. With the n-butanol increased, the combustion instability of the blended fuels decreased significantly, at low load. At n = 2400r/min, pme = 0.53 MPa, compared with diesel, the maximum heat release rate (MHRR) of R70B30 increased by 76.6 %, improving the combustion characteristics of the blended fuel. Moreover, the equivalent specific fuel consumption (ESFC) of RP-3 is 5.56–14.83 % lower than that of diesel, and the effective thermal efficiency (ETE) of RP-3 is 2.8–13.46 % higher than that of diesel under most working conditions.

Analyzing the effect of carbon nanoparticles on the combustion performance and emissions of a DI diesel engine fueled with the diesel-methanol blend

With the energy crisis and worsening environmental pollution, methanol, as a carbon-neutral fuel, has become a research hotspot in the field of internal combustion engines. This study discusses the influence of different kinds (graphite oxide, GO; multilayer graphene, MG; carbon nanotubes, CNT) and concentrations of carbon nanoparticles, which do not introduce any new elements, added to the diesel-methanol blend on combustion performance and exhaust emissions in a direct injection (DI) diesel engine across diverse operating load conditions. The results showed that the nano-fuels with carbon nano-additives had a better combustion process, with higher peak cylinder pressure (Pmax) and peak heat release rate (HRRmax), and lower ignition delay (ID) and combustion duration (CD). Moreover, the presence of carbon nano-additives resulted in an improvement in brake thermal efficiency (BTE) and a decrement in the break-specific fuel consumption (BSFC). The nano-fuels with GO showed the best optimization effect on the combustion process, followed by MG and CNT. As for emission, the nano-fuels had fewer emissions of CO, HC, and smoke opacity. The nano-fuels with CNT achieved the most significant decrease in emissions of CO and HC. While the presence of GO had the best reduction effect in smoke opacity. However, there was a slight increase in NOx emission. The experimental findings demonstrate that the utilization of carbon nanoparticles in nano-fuels can effectively enhance the application of methanol in internal combustion engines.

Constructing a Skeletal Iso-Propanol–Butanol–Ethanol (IBE)–Diesel Mechanism Using the Decoupling Method

In recent years, biofuels have gained considerable prominence in response to growing concerns about resource scarcity and environmental pollution. Previous investigations have revealed that the appropriate blending of iso-propanol–butanol–ethanol (IBE) into diesel significantly improves both the c combustion efficiency and emission performance of internal combustion engines (ICEs). However, the combustion mechanism of IBE–diesel for the numerical studies of engines has not reached maturity. In this study, a skeletal IBE–diesel multi-component mechanism, comprising 157 species and 603 reactions, was constructed using the decoupling method. It was formulated by amalgamating the reduced fuel-related sub-mechanisms derived from diesel surrogates (n-dodecane, iso-cetane, iso-octane, toluene, and decalin) and n-butanol, along with the detailed core sub-mechanisms of C1, C2, C3, CO, and H2. The constructed mechanism is capable of better matching the physical and chemical properties of actual diesel fuel. Extensive validation, including ignition delay, laminar flame speed, a premixed flame species profile, and engine experimental data, confirms the reliability of the mechanism in engine numerical studies. Subsequent investigations reveal that as the IBE blend ratio and EGR rate increase, the ignition delay exhibits an increase, while the combustion duration experiences a decrease. Blending IBE into diesel, along with a specific EGR rate, proves effective in simultaneously reducing NOx and soot emissions.

Simulation Study on Combustion Performance of Ammonia-Hydrogen Fuel Engines

Ammonia is a very promising alternative fuel for internal combustion engines, but there are some disadvantages, such as difficulty in ignition and slow combustion rate when ammonia is used alone. Aiming to address the problem of ammonia combustion difficulty, measures are proposed to improve ammonia combustion by blending hydrogen. A one-dimensional turbocharged ammonia-hydrogen engine simulation model was established, and the combustion model was corrected and verified. Using the verified one-dimensional model, the effects of different ratios of hydrogen to ammonia, different rotational speeds and loads on the combustion performance are investigated. The results show that the ignition delay and combustion duration is shortened with the increase of the hydrogen blending ratio. The appropriate amount of hydrogen blending can improve the brake’s thermal efficiency. With the increase in engine speed, increasing the proportion of hydrogen blending is necessary to ensure reliable ignition. In conclusion, the ammonia-hydrogen fuel engine has good combustion performance, but it is necessary to choose the appropriate hydrogen blending ratio according to the engine’s operating conditions and requirements.

Burning behavior and fire hazards of petroleum liquid combustible spills

In July 2019, an arson using motor gasoline occurred in Kyoto. After the incident, the Fire Services Law in Japan was revised to regulate the sale of motor gasoline in portable cans to prevent similar incidents. However, other petroleum combustible liquids, such as white gasoline and lighter oil, remain easily accessible. Hence, the burning behavior when petroleum combustible liquids and motor gasoline are spilled should be elucidated. Although the burning behavior of spilled motor gasoline on a floor has been studied, the burning behavior of other petroleum combustible liquids has not yet been reported. Therefore, this study aims to investigate the burning behavior of eight types of petroleum combustible liquids, including motor gasoline. Gas chromatography–mass spectrometry analyses were performed to determine the sample compositions. The flashpoints were estimated from the measured saturated vapor pressures. A circular bank with a diameter of 1.6 m was created on a calcium silicate floor, and 4 L sample liquid was spilled inside the bank. From the results of the burning experiments, the flame temperature, surrounding heat flux, flame height, and burning duration of the petroleum combustible liquids were determined. Additionally, we attempted to predict the potential burn injuries to the human body around the flame based on the flux data. The results of this study can be applied to the fire risk assessment caused by petroleum combustible liquids and help predict burn injuries to victims.

Combustion and emission of diesel/PODE/gasoline blended fuel in a diesel engine that meet the China VI emission standards

The present study examined the impact of blending polyoxymethylene dimethyl ethers (PODE) and gasoline with diesel on combustion and emission characteristics in an engine compliant with China VI emission standards. The effects on cylinder pressure, combustion duration, and emissions (CO, THC, PN, and NOx) by blending 20 % PODE into diesel and adjusting the gasoline content (0 %, 5 %, and 10 %) were analyzed. The results showed that the cylinder pressures and the combustion duration were reduced with the addition of PODE, compared to the cases of the pure diesel. Moreover, it was found that PODE contributed to reducing the emissions of CO, THC, and PN, and but increasing NOx emissions. Compared to the cases of PODE and diesel blended fuel, the effect of the addition of gasoline on the cylinder pressures and combustion duration presented a minor increasing tendency, and the lower proportion of gasoline blending was found to effectively curb NOx formation. Specifically, blending 5 % gasoline with a 20 % PODE and diesel mixtures resulted in a 4.01 % reduction in NOx emissions. Based on the results of the present study, it can be concluded that 5 % gasoline and 20 % PODE blend in diesel can enhance combustion efficiency and heat release rate and also can achieve a balanced reduction in NOx emissions. The present study provides valuable insights for the development of energy-saving and emission reduction technologies for diesel engines, highlighting the potential of optimized fuel blends to improve combustion and emissions control.

Experimental study on diesel spray flame and wall heat transfer of two-dimensional combustion chamber: effect of common rail pressure

Reducing the heat transfer occurring during the spray combustion of diesel engines remains a challenging task. This study investigated the spray flame behaviour, wall heat flux, and heat transfer phenomena of diesel engines at varying common rail pressures. A rapid compression and expansion machine (RCEM) was employed to simulate a single cycle of diesel spray combustion using split injection sprays. The two-dimensional (2D) stepped piston cavity is a uniquely shaped model used to describe the spray flame behaviour in the combustion chamber. To investigate the heat transfer phenomena, we installed wall heat flux sensors in the cylinder and cavity side. The results indicated that higher common rail pressures increased the peak value of the wall heat flux and reduced the combustion duration and the luminous flame. The higher common rail pressure led to an increase in spray velocity, thereby enhancing the turbulence level. This increase in turbulence to higher peak value of the wall heat flux. The highest peak value of the wall heat flux was reached by the cylinder head owing to the intense combustion region, followed by the cavity bottom owing to the highest flame temperature occurring around this location. Additionally, the heat transfer phenomena in diesel engines were successfully represented by local Nu-Re correlations. Our results contribute to the discussion on heat transfer phenomena that influence the thermal efficiency of diesel combustion engines.

Effects of in-cylinder water injection on knocking and combustion stability generated by expanding the lean burn limit

The integration of direct water injection (DWI) with the lean burn (LB) process can significantly enhance engine performance. This study reveals that an increase in the water-fuel (W/F) ratio suppressed knocking by extending the ignition delay time. Specifically, the knocking of stoichiometric combustion was suppressed, while that of deeper LB (excess air ratio (λ)˃1.5) was sensitive to a larger W/F ratio. The intensity of knocks during stoichiometric combustion decreased significantly (more than twofold) when the W/F ratio increased from 0.1 to 0.2. Under identical W/F conditions, a shorter ignition delay (CA0–10) and combustion duration (CA10–90) of the main combustion flame were identified as important factors for knocking when λ increased from 1 to 1.5. However, for λ values exceeding 1.5, CA10–90 emerged as the primary knocking determinant. Faster flame propagation and higher oxygen concentration caused by LB and an early spark promoted autoignition of the end-gas and increased the autoignition heat release rate, thus strengthening knock intensity (KI). Furthermore, a minimal amount of water (W/F ≤ 0.3) exerted negligible influence on the stoichiometric combustion stability. As the LB approached its limit, the average KI remained relatively consistent, with combustion stability emerging as the key factor in elevating the LB performance. A 0.3 W/F ratio and precise spark timing ensured that a balance exists between combustion stability and knocking, while simultaneously elevating λ to 2.0.

Effects of vacuum degree on the detonation characteristics and energy release laws of RDX explosive

To explore the detonation characteristics and energy release laws of RDX explosives under varying degrees of vacuum, the influence of vacuum degree on the fireball characteristic parameters, shock wave propagation laws and detonation performance of columnar RDX charges were studied using the air-blast experiments and AUTODYN simulations, and the fireball temperature distributions were mapped with the colorimetric thermometry technique. The experimental results indicated that as the degree of vacuum increased, the combustion duration and zone area size of the explosive fireball were both extended, while its temperature decay rate was slowed down, making the afterburning effect more pronounced. Furthermore, the peak overpressure and positive impulse of the explosion shock wave showed a downward trend, with the reductions of 56.1 % and 53.5 %, respectively, with the increasing vacuum degree. Numerical simulation was also used to reveal the energy release laws of RDX explosive, and the comparison between the experimental and numerical results showed a good degree of concordance with an average error of 6.45 %. The results of the study could provide a reference for expanding the explosion theory of explosives in plateau environment and improving the performance of explosion-proof equipment.

Combustion and mechanical properties of pellets from biomass and industrial waste

Experimental research findings are reported on the impact of industrial waste additives on the mechanical properties of pellets, their ignition and combustion. The compositions under study consisted of wood sawdust with coal slime/peat/a mixture of straw and rice husk. Composite pellets exhibited high moisture resistance and durability when subjected to vibration. The respective coefficients were 6–32 % higher than for sawdust without additives. The ignition characteristics of wood pellets tended to worsen when additional components were used in their composition. The ignition delay times increased by a factor of 3–4. In most cases, the use of additives increased the combustion duration of pellet fuels. The greatest environmental benefits in terms of carbon oxides were gained from mixtures of straw with rice husk and coal slime. СО2 and СО emissions decreased by 10–20 % and 10–54 %, respectively. A high nitrogen content in peat, coal slime and straw led to 5–94 % higher emissions of NOx for composite pellets. Using plant biomass and peat reduced the concentrations of sulfur oxides almost 3-fold. The results of multi-criteria analysis covering 13 energy, operational, economic and environmental components suggest that the difference in the relative efficiency indicator of wood pellets and compositions with industrial waste additives is 4.4–6.5 %.

Effect of Temperatures on Flame Propagation of Diethyl Ether Spray Explosion

ABSTRACT The study aims to identify the flame propagation in the diethyl ether (DEE) spray explosion through mathematical analysis by processing the gray-level histogram of the flame images. Different ambient and material temperatures’ effect on flame propagation and structure was investigated using a high-speed camera in a 20-L explosion vessel. The results showed that the overall duration could be divided into combustion and deflagration processes. With the ambient temperature increased, the combustion duration showed a trend of first decreasing, then increasing, and then decreasing again. The combustion zone first increased and then decreased. The explosion duration showed an overall decreasing trend. The explosion duration was longer than the combustion duration, ranging from 152.75 to 307 ms. The overall combustion and explosion duration trend was consistent with the explosion duration. When the ambient temperature was 308.15 K, the combustion duration reached its minimum value of 13.25 ms, and the equivalent radius of the combustion zone reached its maximum value of 52.89 mm. With the increase in material temperature, both the combustion and explosion durations showed a trend of first decreasing and then increasing, with combustion durations ranging from 12.42 to 16.25 ms and explosion durations ranging from 106 to 117.5 ms, respectively. When the material temperature was 308.15 K, the combustion zone expansion rate reached its maximum value of 10.20 m/s, and the explosion zone expansion rate reached its maximum value of 13.36 m/s. The effect of ambient temperature on the development of combustion zone is greater than that of material temperature, which is mainly reflected in the obvious change of equivalent radius.