Trifunctional synergy of CuFe2O4 as oxidizer, catalyzer and microwave sensitizer in Ti-based pyrotechnics: Low ignition latency and superior combustion

Fossil fuels are the primary sources of energy used in the world. They are polluting and detrimental to the environment. To meet this challenge, renewable energies with a better environmental footprint and that are inexhaustible have been developed. This is the case with biochar, an intriguing alternative to the unsustainable use of traditional energy (firewood, charcoal, and natural gas) in developing nations. Biochar is a clean and sustainable energy source. Unfortunately, this technology needs to be used more in Benin. In order to understand the low level of use of biochar in Benin, this research was carried out. A semi-directive survey of Benins biochar producers and consumers was conducted as the first step in the approach used to identify and analyze the factors that influence the adoption of biochar. The purposive sampling technique was used to select three towns in Benin republic with large populations and where biochar factories are located (Porto-Novo, Cotonou, and Abomey-Calavi). In the second step, the manufacturing process of biochars was analyzed. The findings showed that 56% of surveyed households had adopted biochar compared to 44% who had not. Low ignition and combustion, crumbling, and late delivery of biochars are factors in the need for more adoption. The reasons for the non-adoption are low ignition and combustion, crumbling, and late delivery of biochars.

This study focuses on the fundamental characteristics of DME (Dimethyl ether) combustion with exhaust gas recirculation EGR, aiming at development of the low NOx combustion technology of DME under the high pressure. EGR reduces the NOx emission by recirculating the exhaust gas into the combustion chamber to control the oxygen concentration and the combustion gas temperature. EGR at the high mixing ratio, however, may lead to unstable combustion of conventional fuels, methane or city gas. On the other hand, DME has high potential of applicability of EGR even at the high mixing ratio because of its high burning velocity and low ignition temperature. In this experiment, the oxygen concentration and the combustion air temperature were systematically regulated, so that the exhaust gas recirculation was simulated. The combustion test was conducted with laboratory-scale 8kW combustor. Initial air ratio λ was 1.5. At the atmospheric pressure, the exhaust gas recirculation can be applied to 54% of the EGR ratio. The NOx concentration reduces to 10ppm at 0%-O2, which corresponds to about 22% of NOx emission without EGR. However, the flame became unstable at 54% of the EGR ratio. By increasing the pressure in the combustion chamber, the NOx concentration increased the 84ppm at 0.3MPa-without EGR. The maximum EGR ratio can be applied to 59% under the pressure of 0.3MPa, wihch is almost the same with that at atmospheric pressure. The NOx emission in the exhaust gas decreases to 17ppm. The exhaust gas recirculation is effective to the low NOx combustion of DME at the high pressure.

<div class="section abstract"><div class="htmlview paragraph">Low temperature plasma ignition has been proposed as a new ignition technique as it has features of good wear resistance, low energy release and combustion enhancement. In the authors’ previous study, lean burn limit could be extended slightly by low temperature plasma ignition while the power supply’s performance with steep voltage rising with time (dV/dt), showed higher peak value of the rate of heat release and better indicated thermal efficiency. In this study, basic study of low temperature plasma ignition system was carried out to find out the reason of combustion enhancement. Moreover, the durability test of low temperature plasma plug was performed to check the wear resistance.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Low temperature plasma ignition has been proposed as a new ignition technique as it has features of good wear resistance, low energy release and combustion enhancement. In the authors’ previous study, lean burn limit could be extended by low temperature plasma ignition while a voltage drop during discharge, leading to the transition to arc discharge, was found. In this study, the structure of plug and power supply’s performance with steep voltage rising with time, dV/dt, are examined to investigate the effects on combustion performance. As a result, comparing three power sources of conventional, IES and steep dV/dt, steep dV/dt showed small cycle-to-cycle variation and shorter combustion period, leading to higher peak value of the rate of heat release and better indicated thermal efficiency by relatively 6% and 4% compared to CIC and IES, respectively.</div></div>

This study developed a new model for the low NOxignition for the direct flow of pulverized coal, which enabled the influence of the primary air and internally recirculated flue gas (RFG) on NOx formation to be investigated. A model of the preignition zone was discussed in detail. Three new parameters, the Local Stoichiometric Ratio of Volatiles(LSRV), the Virtual Temperature of Ignition (VTI) and a Gxnumber to indicate NOx reduction potential were introduced to analyze the influence of the primary air/RFG parameters on low NOx ignition. It was found that coal volatiles and size had a major impact on establishing the primary air parameters and ignition position which are favorable for low NOxcombustion. The model can be used to determine the necessary mixing parameters for the design or modification of boilers for low NOx coal combustion.

Boron particles have several major burning problems, such as incomplete combustion, poor ignitability, and a complex burning process in solid propellants. It is documented that the low ignitability and combustion efficiency of boron are caused by the oxidation of its surface. In order to improve the combustion efficiency of boron particles, a precipitation method was employed to prepare nanometer‐sized NiO and coat it on boron particles. The morphology and coating results of the B/NiO nanocomposite thermite were characterized using different approaches such as SEM, X‐ray Diffraction (XRD), and EDS. The results indicated that the boron particles were well distributed and coated completely by nanocomposite NiO. The B/NiO nanocomposite thermite reaction process was tested by TG‐DTA. The results showed that the reaction temperature of B/NiO particles is about 30 °C lower than that of boron particles. The B/NiO thermite and boron powder were added to Mg/PTFE propellant to be measured for their respective combustion performance. The results showed that the burning rate of the B/NiO‐Mg/PTFE propellant increased by 22.8–25.2 %, mass burning rate by 26.7–30.8 %, and combustion temperature increased by 8–56 °C compared to the B‐Mg/PTFE propellant. The above results indicate that NiO coating of boron particles has a significant effect on the combustion behavior and increases the combustion performance of the propellant compared with uncoated particles.

Because ammonia is easier to store and transport over long distances than hydrogen, it is a promising research direction as a potential carrier for hydrogen. However, its low ignition and combustion rates pose challenges for running conventional ignition engines solely on ammonia fuel over the entire operational range. In this study, we attempted to identify a stable engine combustion zone using a high-pressure direct injection of ammonia fuel into a 2.5 L spark ignition engine and examined the potential for extending the operational range by adding hydrogen. As it is difficult to secure combustion stability in a low-temperature atmosphere, the experiment was conducted in a sufficiently-warmed atmosphere (90 ± 2.5 °C), and the combustion, emission, and efficiency results under each operating condition were experimentally compared. At 1500 rpm, the addition of 10% hydrogen resulted in a notable 20.26% surge in the maximum torque, reaching 263.5 Nm, in contrast with the case where only ammonia fuel was used. Furthermore, combustion stability was ensured at a torque of 140 Nm by reducing the fuel and air flow rates.

Thermal energy simulation safety model of wupaolong fireworks based on Friedman method

<div class="section abstract"><div class="htmlview paragraph">An increasing need to lower greenhouse gas emissions, and so move away from fossil fuels like diesel and gasoline, has greatly increased the interest for methanol. Methanol can be produced from renewable sources and eliminate soot emissions from combustion engines [<span class="xref">1</span>]. Since compression ignition (CI) engines are used for the majority of commercial applications, research is intensifying into the use of methanol, as a replacement for diesel fuel, in CI engines. This includes work on dual-fuel set-ups, different fuel blends with methanol, ignition enhancers mixed with methanol, and partially premixed combustion (PPC) strategies with methanol. However, methanol is difficult to ignite, using compression alone, at low load conditions. The problem comes from methanol’s high octane number, low lower heating value and high heat of vaporization, which add up to a lot of heat being needed from the start to combust methanol [<span class="xref">2</span>]. This paper investigates methanol combustion at low load and compares it to diesel fuel, using a more classical diesel combustion strategy of diffusion combustion. This paper also investigates how a high compression ratio could aid the low load combustion of methanol. To get the methanol burning, with similar stability as diesel fuel, intake heating was used together with a pilot injection, of about a third of the main injection quantity. The resulting efficiencies were similar between diesel fuel and methanol, and for the emission measurements NOx was much lower for methanol than for diesel fuel. Increasing the compression ratio resulted in stable combustion without the need for intake heating and a pilot injection, at even lower loads. It also yielded higher efficiency without having a major effect on the emissions.</div></div>

Microscale combustion: Technology development and fundamental research

Pressure conditions under which chemical reactions proceed in gas turbine combustors impact the behavior of the combustion process by either increasing or decreasing the reaction rates depending on whether these reactions are unimolecular/recombination or chemically activated bimolecular reactions. Some reactions are pressure independent such as H-abstraction reactions, while others are conditionally pressure independent if they are not at their either low or high limits. The recombination and decomposition of kinetic reactions rate constants change relative to their limiting values as the pressure and/or temperature conditions vary and as a result the reactants concentrations and reactions pathways are also influenced. In this study, pressure-dependent kinetic rate parameters for 39 elementary reactions have been added to our detailed JP-8/Jet-A kinetic reaction mechanism, we have developed [1–3, 23, 58], to model ignition of JP-8 and Jet-A fuels behind a reflected shock wave. The main objective is to develop a detailed chemical kinetic reaction mechanism for low and high pressure combustion conditions, using a 6-component surrogate fuel blend considered to represent the actual (petroleum-derived) JP-8 and Jet-A fuels. The pressure-dependent kinetic rate parameters for 39 reactions have been incorporated into our low pressure detailed JP-8 chemical kinetic reaction mechanism to generate the fall-off curves for the Arrehnius rate parameters required for low and high pressure ignition analysis. The new JP-8 detailed mechanism has been evaluated, using a stoichiometric JP-8/02/N2 and Jet-A/air mixtures, over a temperature range of 968–1639 K and a pressure range of 10 to 34 atmosphere by predicting auto-ignition delay times and comparing them to the shock tube ignition data of Minsk, Sarikovskii, and Hanson [56]. The results indicated that the developed JP-8/Jet-A reaction mechanism is capable of reproducing the qualitative ignition trends of the measured ignition data behind a reflected shock wave. However, the detailed kinetic reaction mechanism overestimated the measured ignition delay times. The results also suggested that additional more reactions are high pressure-dependent under the conditions considered in this study and as such a need still exists for experimentally measured kinetic rate coefficients for high pressure ignition and combustion conditions. This study, therefore, warrants further experiments and detailed kinetic analysis.

This work was sponsored by the Fuel Technology Division at Saudi Aramco R&DC. The surrogate formulation work at King Abdullah University of Science and Technology (KAUST) was supported by KAUST and Saudi Aramco under the FUELCOM program. We also acknowledge the helpful discussions with Janardhan Kodavasal from Argonne National Laboratory.

Modeling combustion timing in an RCCI engine by means of a control oriented model

n-Butanol reactivity modulation with early fuel injections for low NOx compression ignition combustion

This paper describes a linear optimal control approach for advanced diesel engines equipped with complex air-path systems including a dual-loop exhaust gas recirculation (EGR) and a two-stage turbocharger. Such complex air-path systems are instrumental to achieve smooth and stable transient operation of diesel engines running advanced multiple combustion modes such as low temperature diffusion combustion (LTDC) and homogeneous charge compression ignition (HCCI). A mean-value engine model was developed to capture the main dynamics of the advanced air-path system. A linear quadratic regulator (LQR) optimal controller was designed based on a linearized model at a fixed operating point. Simulation results using a high-fidelity detailed GT-Power engine model show the effectiveness of the controller.