Combustion Temperature Research Articles

Oxy-fuel co-combustion properties and N-containing pollutants release characteristics of biomass/coal blends

Thermal properties and NO release characteristics during oxy-fuel co-combustion of pine sawdust (PS) and Shenmu coal (SM) were investigated based on the effects of various parameters, including atmosphere, temperature, blending ratio, and oxygen concentration in this research. The results indicate that the release of NO decreased with the increasing temperature during decomposition process of PS and SM. The content of N-Q and N-X in semicoke (SC) increased at higher torrefaction temperature. The N-Q and N-X content for SC at the temperature of 1000 °C was 36.9 % and 23.2 %, respectively. When 40 % PS was added to the SM, the NO release amount was significantly reduced by 16.3–23.1 % in the oxy-fuel atmosphere compared to the O2/N2 atmosphere, and the ignition time was reduced from 4.0s to 0.66s. The NO emission initially increased and then decreased as the combustion temperature increased from 800 to 1000 °C. Furthermore, increasing the oxygen concentration from 10 % to 40 % shortens the combustion time and increases the emissions of NO. Conversely, increasing PS blending ratios from 10 % to 40 % decreased NO emission and the conversion ratio. These findings emphasize that adding biomass can effectively improve coal ignition, increase combustion rates, reduce NO emissions, and address the air pollution problems associated with NOx emissions.

Construction Brick Production Industry in Southern Thailand: a Case Study of Kiln

Purpose: To study the kiln that affect the construction brick production industry and to provide guidelines for solving problems. Method: This is qualitative research collecting data from 17 Kiln brick production industry Owners with in-depth interview. Data is analyzed by content and thematic analysis. Results and Conclusion: (1) Physical characteristics of the furnace square brick kiln model. The structure of this kiln is made of cooked bricks into a rectangular permanent wall. There is a firewood compartment and a brick entry door on the side. Production capacity is 50,000-100,000 bricks/stove. Specific energy was 1.6-3.8 MJ/kg of brick, some stoves use 7.8 MJ/kg brick. (2) Burning temperature. Brick firing in Thailand usually ends at 900 degrees Celsius, with brick heating, brick drying, brick kilning, and temperature reduction. which uses a fairly high temperature for burning. (3) The burning time is approximately 7 days, which corresponds to the temperature of the firing side by heating the bricks, baking the bricks, burning the bricks, and reducing the temperature. By using firewood as a leaven. Therefore, there is a lack of technology development in brick production and efficient brick firing with a long firing period. (4) Heat energy loss. Brick firing in Thailand usually ends at a temperature of 900 degrees Celsius and is then turned off for a few days. To reduce cracking due to sudden temperature changes, then turn on the kiln to let the bricks cool naturally allowing the bricks to cool naturally. The heat energy stored is left and that is a loss of heat energy. Research Implications: Brick burning uses a lot of energy, firewood as fuel, and the efficiency of the kilns used is quite low. It is likely that the efficiency of brick kilns will be improved or brick kilns with high thermal efficiency to be used as a replacement to achieve high efficiency. This allows the brick production industry to continue to exist. Originality/Value: The improvement of fuel using for Kiln in brick burning can be improved for more effectiveness and clean environment.

Safely and Efficiently Prepare Environmental-Friendly Gas Generator with High Gas Production Performance

ABSTRACT Excellent gas generation and boost rate, low residue rate, and low burning temperature, as well as stable combustion, have always been the key performance of gas generators in the effective functioning of automotive airbag systems. Under the conditions of material properties, formulation, and charge structure being determined, how to safely prepare gas generators with closely contacting component interfaces has become a necessary problem to solve. In this study, vacuum freeze-drying technology was used to prepare KNO3/5 aminotetrazole (5-AT) and KNO3/nitroguanidine (NQ) gas generators. The whole process effectively avoids high temperature and thus ensures operational safety. Compared to physically and mechanically mixed agents, the agents prepared through freeze-drying exhibit stable combustion, with a nearly doubled combustion speed and a reduction of nearly 100°C in combustion temperature. The residual rates of KNO3/5-AT and KNO3/NQ after combustion prepared through freeze-drying are 2.55% and 3.30%, respectively, indicating a more complete combustion process. The maximum combustion pressures reach 97.18 MPa and 88.15 MPa, respectively, with a significant increase in the maximum pressure rise rate. Consequently, the prepared gas generators demonstrate enormous potential in automotive airbag systems.

Innovative carbonization techniques for food waste: A comparative study of hydrothermal carbonization (HTC) and vapor-thermal carbonization (VTC)

This study addresses the pressing issue of global food waste (FW) by conducting a comprehensive comparison between two conversion methods: hydrothermal carbonization (HTC) and vapor-thermal carbonization (VTC) for the production of hydrochar. The analysis encompasses physicochemical characterizations, Fuel characteristics, and surface properties. Under identical reaction conditions (180–250 °C, 30 minutes), both processes significantly elevate the carbon content of hydrochar. VTC-hydrochar with a carbon content ranging from 54 % to 62 %, while HTC-hydrochar with a slightly higher range of 55–63 %. Notably, hydrochar derived from both methods results in higher heating values (HHV) of 24.04–27.40 MJ/kg for HTC and 22.85–26.60 MJ/kg for VTC, indicating enhanced fuel quality. But with less volatile matter, VTC-hydrochar shows lower HHV. Moreover, HTC-hydrochar demonstrates superior attributes for rapid ignition and energy release, while VTC-hydrochar proves more suitable for applications requiring higher combustion temperatures and stability. In terms of surface properties, VTC-hydrochar demonstrates a higher NH4+ adsorption capacity attributed to its superior pore structure and abundant key functional groups, making it an ideal choice for adsorption applications. Most notably, through comparative analysis, finding that VTC-hydrochar with a more uniform structure from the complex and diverse FW feedstock. This study establishes a robust scientific foundation for selecting appropriate hydrochar production technologies.

Performance and environmental impact of ethanol-kerosene blends as sustainable aviation fuels in micro turbo-engines

The research experimentally examines the viability of ethanol (E) as a sustainable aviation fuel (SAF) when mixed with kerosene (Ke) – Jet A aviation fuel + 5% Aeroshell oil. Various blends of ethanol and kerosene (10%, 20%, and 30% vol. of ethanol added in kerosene) were subjected to testing in an aviation micro turbo-engine under different operational states: idle, cruise, and maximum power. During the tests, monitoring of engine parameters such as burning temperature, fuel consumption, and thrust force was conducted. The study also encompassed the calculation of crucial performance indicators like burning efficiency, thermal efficiency, and specific consumption for all fuel blends under maximum power conditions. Physical-chemical properties of the blends, encompassing density, viscosity, flash point, and calorific power, were determined. Furthermore, elemental analysis and FTIR were used for chemical composition determination. The research delved into analyzing the air requirements for stoichiometric combustion and computed resulting emissions of CO2 and H2O. Experimental assessments were performed on the Jet Cat P80® micro-turbo engine, covering aspects such as starting procedures, acceleration, deceleration, and emissions of pollutants (CO and SO2) during diverse engine operational phases. The outcomes reveal that the examined fuel blends exhibited stable engine performance across all tested conditions. This indicates that these blends hold promise as sustainable aviation fuels for micro turbo-engines, presenting benefits in terms of diminished pollution and a more ecologically sound raw material base for fuel production.

Revealing flow structures in horizontal pipe and biomass combustor using computational fluid dynamics simulation

AbstractComputational fluid dynamics (CFD) is a powerful tool to provide information on detailed turbulent flow in unit processes. For that reason, this study intends to reveal the flow structures in the horizontal pipe and biomass combustor. The simulation was aided by ANSYS Fluent employing standard ‐ model. The results show that a greater Reynolds number generates more turbulence. The pressure drop inside the pipe is also found steeper for small pipe diameters following Fanning's correlation. The fully developed flow for the laminar regime is found in locations where the ratio of entrance length to pipe diameter complies with Hagen–Poiseuille's rule. The sucking phenomenon in jet flow is also similar to the working principle of ejector. For the biomass combustor, the average combustion temperature is 356–696°C, and the maximum flame temperature is 1587–1697°C. Subsequently, air initially flows through the burner area and then moves to the outlet when enters the combustor chamber. Not so for particle flow, the particle experiences sedimentation in the burner area and then falls as it enters the combustor chamber. This study also convinces that secondary air supply can produce more circulating effects in the combustor.

Effect of diglyme on diesel engine combustion and un/regulated emission

ABSTRACT The influence of diglyme on diesel engine combustion and emission, including regulated and unregulated emissions, was carried out at various engine modes, in which ultra-low sulfur diesel and diglyme were employed, and diesel-diglyme blends were designed containing specific mass oxygen content varied from 2% to 20% corresponding to 5% to 53% diglyme blended by volume. With the addition of diglyme, actual air/fuel ratio decreased in general, combustion initiated earlier by 5.3% to 14.6% at tested modes but weighted center postponed with short ignition delay and combustion duration, meanwhile maximum in-cylinder combustion temperature reduced by 3 to 30°C, which affected emissions significantly.Consequently, the optimized PM-NOx trade-off was obtained with particulate and NOx decreased simultaneously, but formaldehyde and acetaldehyde increased by the varation from 3% to 190% with the addition of diglyme. Sulfur dioxide emission was much lower with ultra-low sulfur diesel compared that with other fuels including conventional diesel, about one order of magnitude smaller, and diglyme could bring further reduction by maximum of 62.5%. In addition, the oxygen in diglyme promoted CO oxidation and NO2 conversion from NO, leading to an increased NO2/CO ratio by even to 375.9%.

Advanced orthogonal analysis of multi-factorial interactions influencing co-combustion performance and pollution reduction potential of coal gangue and biomass in oxy-fuel combustion conditions

In the current scenario of increasing energy scarcity and stricter environmental protection requirements, the utilization of coal gangue and biomass energy is gaining attention worldwide. Biomass and coal gangue are complementary in nature, and their co-combustion can improve the burnout efficiency of coal gangue and reduce pollutant emissions. In this study, coal gangue and wheat straw are selected as research subjects, the optimal process conditions for their co-combustion under the coupling of multiple parameters in oxy-fuel atmosphere through orthogonal experiments are investigated. The results indicate that the most significant factor influencing combustion characteristics is the heating rate. When the biomass content is 45 %, O2 concentration is 50 %, heating rate is 30℃/min and particle size is 180–250μm, the flammability and comprehensive combustion indexes of the samples are maximized, which indicates the optimum combustion characteristics. The primary factor affecting pollutant release is biomass content. When the biomass content is 45 %, O2 concentration is 75 %, combustion temperature is 700℃, and particle size is 180–250μm, the pollutant release concentration is minimized.

Enhanced syngas production from wood biomass by the catalytic packed bed of dolomite, limestone and olivine

Wood biomass was a promising renewable energy source that achieved carbon neutrality and alleviated the energy crisis. To enhance the conversion efficiency of wood to hydrogen, the catalytic combustion system of natural ores (dolomite, limestone and olivine) and wood chips was established. And the effects of the type, location, calcination temperature, content and diameter of catalysts were investigated on the temperature distribution and gas production. The results indicated that the combustion temperature of the hybrid bed was significantly increased with the catalyst addition. The dolomite and limestone particles promoted the hydrogen production, and the mole fractions of hydrogen were improved by 75% and 42%, respectively. When the dolomite was located above the wood layer, the hydrogen fraction was greatly higher than that of mixing with the wood. As the dolomite content increased, both of the hydrogen mole fraction and release time were enlarged obviously. Furthermore, the wood chips and dolomite particles with smaller diameters contributed to syngas production. And the hydrogen decreased with the increasing of air velocity when dolomite addition, which achieved the maximum of 11.2% at the velocity of 2 cm/s.

Facile preparation of Fe-Beta zeolite-supported transition metal oxide catalysts and their catalytic performance for the simultaneous removal of NOx and soot

Diesel engine exhaust comprises nitrogen oxides (NOx) and soot particles, which cause serious air pollution. However, owing to the contradictory nature of NOx reduction and soot oxidation, a trade-off exists in the simultaneous removal of NOx and soot. Consequently, catalytic technology has become a hot research topic. This study prepared MOδ/Fe-Beta (M=Fe, Co, Ni, Mn, Cu) catalysts through incipient wetness impregnation using Fe-Beta as the support and explored the catalytic performance of the above catalysts. The results exhibited the good performance of the prepared catalysts. The introduction of Mn resulted in a lower peak temperature of soot combustion for the catalyst, and slightly decreased deNOx performance of Fe-Beta. The soot combustion temperature was as low as 422 °C, and the temperature window for 80% NO conversion was 164–423 °C. The interaction between MnOδ and zeolite can regulate the acid sites and produce sufficient active oxygen species for the catalyst. The catalytic activity of the MnOδ/Fe-Beta catalyst is due to its strong redox property, appropriate number of acid sites and sufficient number of active oxygen species. In addition, the catalyst had good stability and water and sulfur resistance, therefore it had great potential for future application in simultaneous removal of NOx and soot from diesel engine exhaust.

Comprehensive study and design optimization of a hybrid solar-biomass system for enhanced hydrogen production and carbon dioxide reduction

This study introduces an innovative multi-generation system powered by biomass, which aims to tackle the urgent problem of climate change by reducing CO2 emissions and increasing sustainability. The main problem being tackled is the ineffectiveness and environmental consequences of conventional biomass systems, which do not have methods for generating and injecting hydrogen. The proposed method combines solar panels with proton exchange membrane electrolyzers to generate green hydrogen, hence improving the quality of combustion byproducts. The methods utilized consist of integrating a supercritical carbon dioxide cycle with a thermoelectric generator to enhance the efficiency and cost-effectiveness of power generation. Additionally, flue gas condensation, a multi-effect desalination unit, and efficient waste heat recovery are employed to maximize the utilization of passive energy. The study concludes that under the optimal design, the proposed system outperforms the standard model that exclusively depends on biomass. The key results demonstrates that these characteristics are clearly demonstrated by its superior net power productivity of 3927 kW, exergy efficiency of 32.9 %, and drinkable water production rate of 9.4 kg/s. In addition, the suggested system has a lower levelized energy cost of 17.6 dollars per megawatt-hour and an emission index of 75.5 kg per MWh. However, upon comparing the rates at which exergy is being destroyed, it becomes evident that the majority of the components in the proposed model, such as photovoltaic panels and the electrolyzer unit, have a higher rate of exergy destruction. Ultimately, it can be noted that the fluctuations in combustion and turbine inlet temperature are crucial design parameters that substantially influence the power cycle and the system’s overall performance.

Methanol, the ICE Green Maker

AbstractGreen methanol is a renewable fuel with great advantages when used in a spark ignition combustion process. Methanol has a comparatively high enthalpy of vaporization, leading to lower combustion temperatures as compared to gasoline combustion, and, hence, lower wall heat losses as well as a reduced tendency to pre‐ignition. Therefore, a brake efficiency of more than 40 % (this is comparable to diesel engines!) and furthermore minimal emissions, even at cold start, are possible. The serial combination with an electric powertrain provides a disconnection of the load demand of the powertrain and the operating point of the combustion engine. In this case, a high volumetric and gravimetric power density, easy energy storage and proven infrastructure of fuel distribution are combined with electric driving, high efficiencies, minimal emissions, and a closed carbon cycle for the energy provision.

Study on the synergistic control of nitrogenous emissions and greenhouse gas of ammonia/diesel dual direct injection two-stroke engine

This study developed a numerical model for an ammonia/diesel dual direct-injection two-stroke engine and validated it based on engine bench test results. The engine combustion and emission characteristics were discussed under the cases of different injection parameters, intake temperatures, and exhaust gas re-circulation (EGR) rates. The findings indicate that altering the injection angle of ammonia and diesel sprays impacts the in-cylinder swirl and the ignition timing of the ammonia spray, consequently affecting the heat release phase of ammonia combustion. A suitable arrangement spray plumes can effectively reduce the emissions of unburned ammonia and greenhouse gas (GHG), while increase the emissions of NOx. On the other hand, higher intake temperatures can increase the average in-cylinder temperature, reducing unburned ammonia, N2O and GHG emissions. However, it also results in greater NO emissions, which can affect fuel economy negatively. Furthermore, the use of EGR technology can reduce the combustion temperature, thereby lowering the emission of nitrogen-based pollutants, but it also reduces ammonia combustion efficiency. By simultaneously applying the three aforementioned technologies within a certain range of conditions, it is possible to effectively synergize and control nitrogenous emissions and GHG while maintaining high thermal efficiency of ammonia/diesel dual direct injection engines.

Degradation of the protective layer on stainless steel by chlorine variation under high-temperature conditions

This study investigates the impact of various chlorine (Cl) content ratios on the degradation of 304 stainless steel during co-combustion of coal with solid recovered fuel (SRF) at a combustion temperature of 1250 °C. The research specifically focuses on the corrosion potential at 550 °C, which represents the temperature in the superheater area of a power plant. High-temperature corrosion experiments are conducted in a laboratory-scale drop tube furnace to observe initial corrosion during combustion. Analyses include visual examination, mineral analysis, microstructure-based metal analysis, and corrosion rate determination. The results show significant degradation at Cl contents higher than 0.09 wt%. The usual carbide formation at the grain boundaries in 304 stainless-steel does not occur in the short-term tests, as indicated by Cr content remaining above 12 % and Cl content less than 0.06 wt%. In addition, material degradation is due to the Cl reacting with alkali content, damaging the oxide layer and causing pits in the cross-section area of the probe material. This research provides insights into the critical role of Cl in metal degradation and identifies the optimum Cl amount suitable for coal blending in power plants.

Understanding FABA composition in coal-fired power plants: Impact of operating conditions and combustion efficiency on ash characteristics – A case study in PT Bukit Asam, South Sumatra, Indonesia

Coal-fired power plants are integral to global electricity production due to their cost-effectiveness and widespread availability of coal. This research investigates the operational dynamics of these plants, emphasizing the production of fly ash and bottom ash (FABA) as crucial by-products. The study focuses on three power plants in South Sumatra, Indonesia, operated by PT Bukit Asam Tbk. Fly ash and Bottom ash (FABA) and feed coal samples were collected to determine how the operational conditions of a power plant impact the composition of FABA. The mineralogical composition of FABA has been determined accurately with X-Ray diffraction analysis. Significant feed oxides in coal and FABA were identified using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The primary characteristics of FABA mostly consist of unburned carbon, which may exceed levels as high as 76.05 %. The existence of unburned carbon residues is evidence of an inefficient coal grinding operation and low combustion efficiency of carbon in the boiler. The abundance of quartz in the FABA corresponds to its condition of being unmelted when heated to a temperature of 850 °C. A decrease in operating temperature results in a lower percentage of amorphous glass. The presence of quartz and reduced plagioclase concentration in FABA components correspond to the utilization of boiler-incompatible sand as bed material. In addition a consequence of a decrease in combustion temperature, pyrite exhibits partial decomposition, resulting in the formation of a tiny amount of hematite, while the other pyrite is still into its original form. A relatively small amount of spinel was associated to a mineral composed of Fe-oxide. Spinel is formed as a secondary mineral through the decomposition of Fe sulfides and other Fe-bearing minerals that exist in coal. This study evaluates the combustion efficiency and operational characteristics of power plants by applying the shrinking reactive core model by the assistance of Matlab®. The results demonstrate that since the efficiency of coal combustion increases, the concentration of unburned carbon in the FABA decreases. The modeling corresponds with the current findings in the field.

Influences of ultra-low load operation strategies on performance of a 300 MW subcritical bituminous coal boiler

To reveal the operational characteristics of subcritical boilers under ultra-low loads, numerical simulations were conducted based on a 300 MW subcritical bituminous coal boiler. The impacts of boiler load and low-load operation strategies on coal combustion behavior, heat transfer process, and NOx emission were thoroughly examined. Results indicate that acceptable aerodynamic and temperature fields can still be formed at 25 % ultra-low load, but the boiler performance is significantly reduced, with the maximum cross-sectional average combustion temperature being reduced by 225.98 K compared with the full-load condition. At 25 % load, the use of only two layers of burners results in a substantial increase in NOx emission from 290.32 mg/m3 to 445.56 mg/m3. The position of in-service burners affects the region where the intense coal combustion and heat release process occurs, and using the middle three layers of burners helps to maintain heat absorption by the suspended heating surfaces and to minimize NOx emissions. Furthermore, increasing primary air velocity at ultra-low loads can promote coal combustion and heat transfer processes in the lower furnace, but increase NOx emission by 14.23 % when primary air velocity is increased from 14.90 m/s to 23.00 m/s at 25 % load. These findings provide valuable insights for optimizing the ultra-low load operation of subcritical boilers engaged in deep peak-shaving processes under the carbon neutrality goal.

Optimization on manifold injection in DI diesel engine fuelled with acetylene

Researchers demonstrated that implementing new combustion technology and optimising fuel quantity results in a significant reduction in traditional fossil fuel usage and emission levels. The Reactivity Controlled Compression Ignition (RCCI) combustion strategy is one of the low temperature combustion technologies, and it is used to reduce the overall combustion temperature while also providing better combustion control. This study looks into RCCI combustion technology, which uses conventional diesel fuel as the high reactivity fuel (HRF) injected through the injector and acetylene gas as the low reactivity fuel (LRF) injected into the cylinder via a modified inlet manifold alongside air. The modified engine setup was tested for performance, emissions, and combustion under various load conditions, as well as different mass flow rates of acetylene gas, a low reactivity fuel that is injected with air. The flow field of the low reactivity fuel at the inlet manifold is analysed using the Computational Fluid Dynamics principle, which is used to determine the best flow rate for improving combustion quality. According to the simulation results, the optimal acetylene flow rate is 3 Litres Per Minute (LPM), and experimentation shows that at 3 LPM acetylene injection, the brake thermal efficiency (BTE) improves by about 3.2%, and emissions such as carbon monoxide (CO), hydrocarbon (HC), smoke intensity, and oxides of nitrogen (NOx) are reduced by about 35%, 17%, 10%, and 21%, respectively.

Tuning the textural properties of biomass-derived nanocrystallized BEA for acetyl functionalization of anisole

The synthesis of a highly active zeolite beta catalyst for acetyl functionalization of anisole by utilizing the silica precursor obtained from rice husk is a promising approach for the mitigation of agricultural waste. The influence of combustion temperature (CT) (300, 500, 700, and 900 °C) on the characteristics of rice husk ash was investigated. The C52H obtained at a medium CT (500 °C) has a high surface area compared to the C72H indicates that, merging of smaller crystals of amorphous silica to form crystalline silica with larger crystallites by applying more thermal energy when CT ≥ 700 °C. The PS-5 catalyst derived from C52H possess high surface area (332 m2/g) and a smaller crystallite size (14.8 nm) compared to the PS-7 obtained from C72H, which shown the lower surface area (131.5 m2/g) with a larger crystallite size (25.6 nm). Solid-state NMR and NH3-TPD analysis reveals that PS-5 catalyst possessing higher acidity compare to both PS and PS-7. The activity studies confirms that the PS-5 catalyst exhibited superior catalytic activity (>98%) compared to PS (conventional) and PS-7 catalysts, making it a potential candidate for continuous production of aromatic ketones. acylation reactions.

Numerical study of the combustion process and NOx evolution mechanism of ammonia-hydrogen compound fuel engine under different intake conditions

To explore the distinction between generation atmosphere of fuel NOx and thermal NOx in an ammonia-hydrogen compound fuel engine, a numerical calculation model was established based on a detailed ammonia-hydrogen oxidation mechanism. The combustion process and NOx evolution mechanism of the ammonia-hydrogen compound fuel engine under different intake conditions were studied. The researchresults for different equivalence ratios show that the in-cylinder hydrogen volume is the primary factor influencing the initial heat release. When the equivalence ratio is between 0.89 and 1.14, the mixture exhibits a higher combustion rate, leading to a shorter CD and an earlier CA50. At this point, the heat release process closer to TDC contributes improving engine combustion efficiency and indicated efficiency. Therefore, when the equivalence ratio is between 0.89 and 1.00, combustion efficiency is higher than 98 % and indicated efficiency is higher than 43 %, the ammonia-hydrogen compound fuel engine achieves relatively higher economy. Both over-rich and over-dilute mixtures induce an enhancement of fuel NOx, while the higher in-cylinder temperature caused by stoichiometric combustion leads to a boom of thermal NOx. Consequently, the total NOx emission from the ammonia-hydrogen compound fuel engine is higher at equivalence ratios between 0.80 and 1.00, and the NOx emission reaches its peak at an equivalence ratio of 0.89. Analysis of the evolution process of key N components in the cylinder shows that incomplete combustion plays a significant role in fuel NOx emissions, while thermal NOx emissions are mainly influenced by the distribution of in-cylinder components and combustion temperature. Specifically, thermal NOx emissions primarily depend on the in-cylinder components distribution in the narrow equivalence ratio range around stoichiometric ratio, and are significantly affected by in-cylinder temperature under other conditions. The in-cylinder oxygen concentration significantly affects fuel NOx emissions under most operating conditions. Further optimization of intake temperature shows that combustion efficiency exceeds 90 % when the intake temperature is above 280 K. When the intake temperature reaches 310 K, the combustion efficiency reaches up to 98 %, thus an intake temperature of about 310 K is sufficient to meet the need for improving the combustion efficiency of ammonia-hydrogen compound fuel engine. To achieve high efficiency and lower NOx emissions, appropriate lean combustion combined with an intake temperature slightly above room temperature is recommended.

Combustion synthesis of TiC- high entropy alloy CoCrFeNiMn composites from granular mixtures

The advantage of combustion synthesis is the ability to produce composites from powders in a single technological step, using the heat of an exothermic reaction, in a fast and energy-efficient manner. Ceramic-metal composites TiC–High-Entropy Alloy (HEA) CoCrFeNiMn were fabricated by combustion synthesis from granular mixtures. The content of the metal binder components varied from 10 to 30 wt% and the combustion velocity and temperature gradually decreased as the binder content increased. Scaling up synthesis requires clarification of the parametric range for implementing a safe combustion mode. The impurity gas content and the range of safe conductive combustion were determined from known theoretical models and experimental combustion velocities of samples of granules of 0.6 and 1.1 mm size. The main phases of the product were titanium carbide with up to 3 at. % Cr and HEA CrCoFeNiMn with a reduced Mn content compared to the equimolar composition. The content of secondary phases Cr7C3 and carbon did not exceed 5 wt%. The use of granular mixtures solved the problem of significant sintering of exothermic powder mixtures containing metal binder during combustion. After synthesis, the granules retain their size and do not sinter together, making it easy to grind the sample and obtain a TiC-HEA composite powder.