Changes In Combustion Characteristics Research Articles

Numerical simulation of co-firing LRC and ammonia in Pangkalan Susu 3 & 4 coal-fired steam power plant (CFSPP) capacity 210 megawatts

The effort to reduce CO2 and NOx emissions plays a crucial role in mitigating climate change, improving air quality, complying with environmental regulations, and promoting clean technology innovation. Ammonia, as an emission-free fuel, shows significant potential as a co-firing agent with Coal in coal-fired steam power plants (CFSPP). Previous studies have demonstrated promising results in emission reduction through ammonia co-firing. This research presents a numerical analysis based on Computational Fluid Dynamics (CFD) to investigate the co-firing of ammonia with low-calorific Coal (LRC) in the CFSPP Pangkalan Susu Units 3 and 4, with a capacity of 210 MW. The study employs fluid flow modelling and chemical reaction analysis using the Discrete Phase Model (DPM) to provide accurate predictions of temperature distribution and pollutant concentrations in pulverized coal boilers. Cofiring simulations were conducted with ammonia additions of 5 % and 15 % on a calorific basis. Injection experiments from each burner (A-D) were performed to identify the optimal injection location. The simulation results indicate changes in combustion characteristics, particularly in temperature distribution. The main finding reveals a temperature decrease when ammonia is added as a co-firing material, attributed to the higher H2O content, which leads to increased moisture losses. In terms of efficiency, co-firing showed a decline compared to the baseline combustion of 100 % LRC coal due to the more significant moisture losses. The highest reduction in CO2 emissions was observed when 15 % ammonia was injected from burner B in case #6, with a mass fraction value of 0.171 at the boiler outlet. Similarly, the most significant reduction in NOx emissions occurred with a 15 % ammonia co-firing from burner B, yielding a mass fraction value of 8.81E-04 at the boiler outlet. This co-firing technology is expected to enhance decarbonization efforts and optimize the use of renewable energy in the future.

Characteristics of spray and combustion in gas-centered swirl coaxial injector with varying gas nozzle diameter

Gas-centered swirl coaxial (GCSC) injectors, a type used in the combustion chamber of liquid rocket engines, have been widely investigated because their characteristics are key parameters for the performance of the engine. This study investigated the spray and combustion characteristics of GCSC injectors used in the combustion chamber of oxidizer-rich staged-combustion cycle engines. When the propellant mass flow rate and oxidizer-to-fuel mass flow ratio (O/F ratio) were identical, the diameter of the gas nozzle was changed such that the ratio of the gas-to-liquid momentum could be changed; thus, the swirl strength of the liquid also changed because of the increase in the injector diameter. In the spray experiments, the spray characteristics were identified in accordance with changes in the diameter of the gas nozzle through the spray angle, droplet mean velocity, and droplet size by using backlight photography and the ParticleMaster imaging system. For combustion tests, four types of reduced combustion chambers were designed to spray propellants through the same two injectors used in the spray experiments. To generate an oxidizer-rich combustion gas, combustion tests were performed using a pre-burner. The changes in combustion characteristics according to the change in the injector shape under the same combustion chamber shape, propellant flow rate, and O/F ratio were identified through the characteristic velocity and heat flux of the combustion chamber. As the gas–liquid momentum flux ratio increased in accordance with the change in diameter of the gas nozzle, the characteristic velocity increased from at least 1700 m/s to a maximum of 1721 m/s, which was related to the decrease in the Sauter mean diameter observed in the spray experiments. Few studies have investigated GCSC shape variables by simultaneously conducting atmospheric spray experiments and high-pressure combustion tests on GCSC injectors using kerosene and oxidizer-rich combustion gases as propellants. This study observed the changes in spray characteristics according to the change in the diameter of the injector gas nozzle through atmospheric spray experiments of the GCSC injector and compared and analyzed the combustion characteristics through combustion tests using the same injector. The results of this study will potentially aid the design optimization of GCSC injectors and facilitate future developments.

DIFFUSION COMBUSTION OF A HYDROGEN MICROJET, OUTFLOWING FROM A CURVLINEAR CHANNEL

The presented work examines the combustion of a hydrogen microjet flowing from a curved channel with a round micronozzle. Jet flows that are generated using rectilinear and curved channels differ in that in the second case, Dean vortices make a noticeable contribution to the formation of the jet and its combustion. The interaction of the latter with Kelvin–Helmholtz vortices, the formation of which is typical for flows with a velocity shift, causes changes in combustion characteristics. They include spatial distortions of the laminar flame zone near the nozzle exit, the area of turbulent combustion downstream, as well as the turbulent flame in the conditions of its separation from the nozzle exit and the cessation of laminar combustion in the initial section of the flow. The results of these studies provide an opportunity to better understand the combustion features of hydrogen microjets under conditions of their hydrodynamic instability.

Gas Turbine Combustion Technologies for Hydrogen Blends

The article reviews gas turbine combustion technologies focusing on their current ability to operate with hydrogen enriched natural gas up to 100% H2. The aim is to provide a picture of the most promising fuel-flexible and clean combustion technologies, the object of current research and development. The use of hydrogen in the gas turbine power generation sector is initially motivated, highlighting both its decarbonisation and electric grid stability objectives; moreover, the state-of-the-art of hydrogen-blend gas turbines and their 2024 and 2030 targets are reported in terms of some key performance indicators. Then, the changes in combustion characteristics due to the hydrogen enrichment of natural gas blends are briefly described, from their enhanced reactivity to their pollutant emissions. Finally, gas turbine combustion strategies, both already commercially available (mostly based on aerodynamic flame stabilisation, self-ignition, and staging) or still under development (like the micro-mixing and the exhaust gas recirculation concepts), are described.

Enhancing the Anti-Migration Performance and Mechanical Properties of EPDM Insulation through Functionalized GO.

The excessive migration of small molecular plasticizers in solid propellants may lead to debonding and changes in combustion characteristics, affecting the safety of solid rocket motors. Herein, two functionalized graphene oxides (GO) were used to enhance the anti-migration performance of EPDM insulation. GO, 3-Aminopropyltriethoxysilane-modified GO (AGO) and octadecylamine-modified GO (HGO) were filled into EPDM to fabricate EPDM insulation. The anti-migration properties and migration kinetics of EPDM insulations were studied using immersion tests. Moreover, the mechanical properties, including the tensile properties, crosslink density, hardness, and aging resistance of different EPDM insulations, were also explored. Compared with GO, AGO, and HGO obviously enhanced the anti-migration and mechanical properties of the EPDM insulations. This study shows that the anti-migration performance of EPDM insulation can be enhanced by functionalized GO.

Effect of Fuel Preheating on Engine Characteristics of Waste Animal Fat-Oil Biodiesel in Compression Ignition Engine.

The present study aims at understanding the effects of fuel preheating on engine characteristics of waste animal fat-oil (WAF-O) biodiesel in a single-cylinder CI engine, with the preheating technique proposed as an effective means for enhancing the fuel properties. To understand the effects of the preheated fuel, the WAF-O biodiesel was preheated at 60, 80, 100 and 120 °C and tested along with neat diesel and unheated WAF-O biodiesel. For this purpose, biodiesel was produced from different animal wastes by means of KOH-assisted ethanol-based transesterification, reporting its maximum yield as 96.37 ± 1.8%, with significant distribution of unsaturated oleic acid, saturated palmitic acid and stearic acid. Upon evaluating its fuel characteristics as per ASTM D6751 standards, a rise in preheating temperature by 1 °C reduced the density and kinematic viscosity of WAF-O biodiesel by 0.383 kg/m3 and 0.025 mm2/s, respectively, and was explained by the weakening of intermolecular forces between its fatty acid ester molecules. Preheated samples reported superior combustion characteristics by exhibiting increased in-cylinder pressure (2.24%, on average) and heat release rates in addition to their shortened ignition delay (1–4 °CA). Furthermore, preheating of WAF-O biodiesel reduced its specific fuel consumption and increased its brake thermal efficiency by 7.86% (on average) and 9.23% (on average), respectively. However, higher preheating temperatures (>120 °C) resulted in increased fuel consumption owing to its varied flow characteristics. In addition to the changes in combustion characteristics, preheating WAF-O bio-diesel also resulted in reduced carbon monoxide, nitrous oxide and hydrocarbon emission by 13.88%, 7.21% and 26.94%, respectively, and increased carbon dioxide emission by 7.58%. Summing up, the enhancements in overall engine characteristics of preheated samples were accounted for by their improvised fuel injection characteristics due to their reduced density and viscosity, which ensured for their effective combustion.

Effects of pyrolyzed semi-char blend ratio on coal combustion and pollution emission in a 0.35 MW pulverized coal-fired furnace

The effects of blend ratio on combustion and pollution emission characteristics for co-combustion of Shenmu pyrolyzed semi-char (SC), i.e., residuals of the coal pyrolysis chemical processing, and Shenhua bituminous coal (SB) were investigated in a 0.35 MW pilot-scale pulverized coal-fired furnace. The gas temperature and concentrations of gaseous species (O2, CO, CO2, NOx and HCN) were measured in the primary combustion zone at different blend ratios. It is found that the standoff distance of ignition changes monotonically from 132 to 384 mm with the increase in pyrolyzed semi-char blend ratio. The effects on the combustion characteristics may be neglected when the blend ratio is less than 30%. Above the 30% blend ratio, the increase in blend ratio postpones ignition in the primary stage and lowers the burnout rate. With the blend ratio increasing, NOx emission at the furnace exit is smallest for the 30% blend ratio and highest for the 100% SC. The NOx concentration was 425 mg/m3 at 6% O2 and char burnout was 76.23% for the 45% blend ratio. The above results indicate that the change of standoff distance and NOx emission were not obvious when the blend ratio of semi-char is less than 45%, and carbon burnout changed a little at all blend ratios. The goal of this study is to achieve blending combustion with a large proportion of semi-char without great changes in combustion characteristics. So, an SC blend ratio of no more than 45% can be suitable for the burning of semi-char.

Change in combustion characteristics due to swirl intensity of diffusion flame burner

Change in combustion characteristics due to swirl intensity of diffusion flame burner

Performance of W/MnO2 as an Environmentally Friendly Energetic Time Delay Composition

Current fielded delay formulations face increased scrutiny due to their environmentally hazardous components (i.e., BaCrO4/KClO4), and there is an immediate need for viable replacements. In this work, the W/MnO2 composition is explored as an environmentally benign time delay replacement. Delay performance and aging characteristics are examined at diameters (6.35 and 4.7 mm) similar to those of common delay housings. Measured maximum combustion temperatures ranged from 1466 to 1670 K as a function of mixture stoichiometry. The measured combustion velocities ranged from 0.67 to 1.68 mm/s for 6.35 mm open air pellets, and from 1.62 to 4.61 mm/s when combusted in 6.35 and 4.7 mm ID Al/SS housings. When packing density was increased and decreased from the standard 60% theoretical maximum density, combustion velocity decreased. For all W/MnO2 formulations, the maximum measured gas production was 9.1 mL/g. Accelerated aging was performed for 8 weeks, and negligible changes in combustion characteristics were obse...

Effects of Microwave Irradiation on Combustion and Sodium Release Characteristics of Zhundong Lignite

Lignite can be upgraded by using microwave irradiation (MI), which may change physical and chemical properties of the coal, affecting its combustion characteristics. In this work, MI was used to upgrade coal samples, and the changes in combustion characteristics of the upgraded coal samples were analyzed by thermogravimetric analysis (TGA) and surface temperature measurement. The method of sequential extraction was employed to investigate the changes of various Na classes in different coal samples, and laser-induced breakdown spectroscopy was then used to measure the temporal sodium release during combustion of the different coal samples. Results show that the MI process significantly reduces the moisture concentration, thereby increasing the carbon content and calorific value of the coal. The decrease of the oxygen–carbon atomic ratio indicates an improvement of the coal rank. The TGA shows that the upgrading process will delay the combustion process toward higher temperatures. The comprehensive combusti...

Supersonic Combustion with Supersonic Injection Through Diamond-Shaped Orifices

Supersonic injections through diamond-shaped injectors were applied to a supersonic combustor with a diverging section, with a Mach 2.4 incoming vitiated airflow at a total temperature of 2000 K, and combustion characteristics were experimentally investigated and compared to those with sonic injection through circular injectors. Without any flame-holding devices installed, scramjet-mode combustion was attained in wide range of fuel flow rate, in which the supersonic injections resulted in a higher pressure-rise in far-field than the sonic injections. Regardless of the injection scheme (i.e, orifice shape, orifice number, and injection conditions), transition to dualmode combustion enhanced the thrust production, and the supersonic injection through the diamond-shaped orifice had lesser ability to cause the transition than the sonic injection through the circular orifice. The ability was enhanced by installation of a recess and introduction of recess fueling, and resulting combustor performance was slightly better than that with the sonic injection, in the case with single orifice. Both the number of the orifice and the injection pressure (by changing the total orifice throat area) were varied for the supersonic injection through the diamond-shaped orifice for fixed fuel flow rates, and the change in combustion characteristics were also reported.

Use of a single-zone thermodynamic model with detailed chemistry to study a natural gas fueled homogeneous charge compression ignition engine

A single zone thermodynamic model with detailed chemical kinetics was used to simulate a natural gas fueled homogeneous charge compression ignition (HCCI) engine. The model employed Chemkin and used chemical kinetics for natural gas with 53 species and 325 reactions. This simulation was used to complete analyses for a modified 0.4 L single cylinder engine. The engine possessed a compression ratio of 21.5:1, and had a bore and stroke of 86 and 75 mm, respectively. Several sets of parametric studies were completed to investigate the minimal initial temperature, engine performance, and nitric oxide emissions of HCCI engine operation. The results show significant changes in combustion characteristics with varying engine operating conditions. Effects of varying equivalence ratios (0.3–1.0), engine speeds (1000–4000 RPM), EGR (0–40%), and fuel compositions were determined and analyzed in detail. In particular, every 0.1 increase in equivalence ratio or 500 rpm increase in engine speed requires about a 5 K higher initial temperature for complete combustion, and leads to around 0.7 bar increase in IMEP.

정적연소기내 예연소실 설계인자가 연소특성에 미치는 영향에 관한 실험적 연구

Natural gas is a promising alternative fuel that can be used to satisfy the strict engine emission regulations in many countries. To develop natural-gas engines, low emission, efficient fuel consumption, and increased power ratings have to be realized. In this study, a cylindrical constant-volume combustion chamber (CVCC) was used to investigate natural-gas combustion characteristics for different prechamber design parameters and equivalence ratios. In particular, the maximum combustion pressure and mass fraction of the burned gas were evaluated by considering orifice diameter, volume ratio of prechamber and equivalence ratio. Using this result and by analyzing the changes in combustion characteristics with variations in design parameters, the optimum prechamber parameters were determined.

Investigation of the Combustion Characteristics with Focus on Partially Premixed Combustion in a Heavy Duty Engine

Partially Premixed Combustion (PPC) has shown its potential by combining high combustion controllability with emission characteristics that are close to those of an HCCI engine. In order to get PPC the ignition delay needs to be long enough for the fuel and air to mix prior to combustion. This can be achieved by injecting the fuel sufficiently early while running with high EGR.In order to find out where and how PPC occurs a map that shows the changes in combustion characteristics with injection timing and EGR was created. The combustion characteristics were studied in a six cylinder heavy duty engine where the Start of Injection (SOI) was swept from early to late injection over a wide range of EGR levels. The emissions were monitored during the sweeps and in the most promising regions, with low emissions and high efficiency, additional changes in injection pressure and engine speed were applied to get a more versatile picture of the combustion. (Less)

EFFECTS OF DIMETHYOXYMETHANE BLENDING INTO DIESEL FUEL ON SOOT IN AN OPTICALLY ACCESSIBLE DI DIESEL ENGINE

Experiments were performed in an optically accessible DI diesel engine to investigate the effects of the addition of dimethoxymethane (DMM) to diesel fuel. The DMM was blended into the baseline diesel fuel to obtain 2% and 4% oxygen by fuel mass. Laser light extinction was used to measure soot variation during combustion as well as exhaust soot levels; NOx, CO2 and CO concentrations in the exhaust were measured using gas analyzers. In addition heat release analysis and direct photography were used to characterize the combustion process. The addition of DMM led to significant reductions in soot, but heat release analysis showed that it also caused significant changes in combustion characteristics, with increases of up to 1.7° of crank angle in ignition delay as well as increases in the fraction of premixed burn. Then, 2-ethylhexylnitrate was used to compensate for the effects on heat release characteristics to determine the relative importance of chemical and heat release effects in reducing soot. A fuel blend of 2,2-dimethylbutane in the diesel fuel was studied to estimate the effects of boiling point on soot and combustion characteristics.

Effects of Processing Temperature of Hot Water Drying on the Properties and Combustion Characteristics of an Indonesian Low Rank Coal

ABSTRACT Experiments have been carried out to measure the effect of processing temperature on the moisture content of low rank coal upgraded by the hot water drying (HWD) method. The Berau coal from East Kalimantan, which was used for this investigation, is a sub-bituminous coal with a calorific value of 5324 kcal/kg and an inherent moisture content of 16.13% (air dried basis). Experimental results from this study indicate that at the processing temperature of 300°C the moisture content is reduced to 1.94% and the calorific value is increased up to 6312 kcal/kg (air dried basis). The change in functional groups determined by FTIR analysis and the change in combustion characteristics determined by DTA-TG are discussed for both the raw and upgraded coals.

Determination of magnetic field effects on a jet diffusion flame in a microgravity environment

The effect of magnetic fields on a laminar jet diffusion flames has been investigated by using a microgravity environment. The magnetic field was changed from fairly low (around 0 mT) to strong (around 215 mT) intensities. The effect of oxygen concentration was also investigated. The buoyancy caused by gravity is dominant for diffusion flames under normal gravity, so the microgravity environment was used to allow an observation of the effect of the magnetic field on combustion, especially for weak magnetic fields. A steady flame could be sustained with a field intensity larger than a critical value that depends on the O 2 concentration. The critical value was determined experimentally and evaluated with a nondimensional number corresponding to the Grashof number used for gravitational fields. The changes in combustion characteristics, that is, flame shape, length, brightness, and color, were evaluated as a function of the magnetic-field intensity. The flame length decreased with increases in the magnetic-field strength, and the color of the flame shifted from red to yellow, indicating a temperature increase with increases in magnetic-field strength. By evaluating the changes in the flame color with chromaticity treatment, it was concluded that the effect of the magnetic field is dominated by F [O 2 ], where F is the magnetic force acting on the combustion, a function of field strength, and [O 2 ] is the surrounding oxygen concentration.

95/01184 Changes in combustion characteristics of coals after treatment with molten caustic leaching

95/01184 Changes in combustion characteristics of coals after treatment with molten caustic leaching

Effect, of Light on the Flammability of Nomex Fabric

Nomex fabrics have been irradiated in a xenon-arc Weather-Ometer, and the resulting changes in combustion char acteristics, tensile properties, and degree of discoloration were measured. The ignition and hurning proprties of ir radiated and unirradiated specimens were determined with the TRI Flammahility Analyzer employing burning con figurations of 45° and the horizontal (12 o'clock). Indications are that the limiting oxygen index is reduced and the burning rate increased as irradiation time is increased. Flammability results obtained with DOC FF 3-71 were not conclusive. Nevertheless, the reduction in flame resistance of Nomex as a result of irradiation appears to be less of a potential problem than the concomitant decrease in tenacity.