Combustion characterization of hybrid methane-hydrogen gas in domestic swirl stoves.

Combustion of hybrid natural gas (methane) and hydrogen mixture in domestic swirl stoves has been characterized using hot-state experiments and numerical analysis. The detailed combustion mechanism of methane and hydrogen (GRI-Mech 3.0) has been simplified to obtain reduced number of chemical reactions involved (82% reduction). The novel simplified combustion mechanism developed has been used to obtain combustion characteristics of hybrid methane-hydrogen mixture. The difference between the calculations from the detailed and the simplified mechanisms has been found to be < 1%. A numerical model, based on the simplified combustion model, is developed, rigorously tested and validated against hot-state tests. The results depict that the maximum difference in combustion zone's average temperature is < 13%. The investigations have then been extended to hybrid methane-hydrogen mixtures with varying volume fraction of hydrogen. The results show that for a mixture containing 15% hydrogen, the release of CO due to combustion reduces by 25%, while the combustion zone's average temperature reduces by 6.7%. The numerical results and hot-state tests both confirm that the temperature remains stable when hybrid methane-hydrogen mixture is used in domestic swirl gas stoves, demonstrating its effectiveness in cooking processes

Theoretical and experimental investigations on the combustion characteristics of three components mixed municipal solid waste.

The combustion characteristics of Mixed Municipal Solid Waste (MMSW) play a vital role in dictating the efficiency of the incineration process. At present, few studies on combustion characteristics of three components MMSW and the establishment of corresponding comprehensive kinetic model of single component waste have been reported. In the present study, based on the law of mass action and Badzioch's relation, the mathematical expressions for describing the TG (Thermogravimetric) curves and the DT (Differential thermal) curves of single component MMSW are derived. A comprehensive kinetic model for the combustion characteristics of single component MMSW is developed and the appropriateness of the model is confirmed by the experimental results. The calculated TG curves closely agree with the experimental curves; the maximum deviation between the experimental and calculated curves is within 5%. Based on the principle of mixture experiments, the co-combustion characteristics of MMSW composed of food bag, disposable chopstick and cotton cloth are studied by using TGA (Thermogravimetric Analysis) and DTA (Differential Thermal Analysis). It has been found that the activation energy of three components MMSW is lower than that of single component. Finally, based on multiple regression analysis for the design of mixture experiments and the corresponding data, an empirical formula for calculating activation energy of three components MMSW is obtained. The experimental and calculated values match closely; the maximum deviations between them is within 7%. The empirical formula provides a robust way to calculate activation energy of three components MMSW

Design of a novel α-shaped flue gas route flame incinerator for the treatment of municipal waste materials.

In order to improve the combustion characteristics of municipal waste materials and reduce excess pollutants generated during the incineration process, this study develops a novel waste incinerator with an α-shaped flue gas route. This has been achieved through the application of momentum vector synthesis theory in order to modify the secondary air structure in a conventional incinerator, resulting in enhanced combustion efficiency of the incinerator. Computational fluid dynamics (CFD)-based cold-state test results demonstrate that, with appropriate modifications to the design of the incinerator, the flue gas propagates through a longer α-shaped route rather than conventional L-shaped route. Hot state tests have been carried out on a full-scale 750 tons/day waste incinerator. Test rests show that the temperature of the flue gas increases by 138% under the front arch when secondary air supply is being incorporated into the design of the incinerator, resulting in better combustion of the municipal waste materials, lower emissions and higher thermal efficiency of the incinerator. The results obtained in this study confirm the rationality and feasibility of momentum flow rate method for better design of waste incinerators

The innovative design of air caps for improving the thermal efficiency of CFB boilers.

Air caps are an effective way of ensuring uniformity of air flow in Circulating Fluidized Bed (CFB) boilers. Published literature on the design and configuration of these air caps is severely limited. In this study, extensive theoretical as well as experimental investigations have been carried out to design novel air caps in order to improve efficiency of CFB boilers. A small-scale test bench of 220 t/h CFB boiler has been developed, integrated with novel air caps. It has been observed that inhomogeneity in air flow velocity decreases from 65.79% to 21.25%, while the pressure drop decreases by 20%. A mathematic model of air caps has been derived and its accuracy verified through cold tests. Two empirical correlations for calculating the pressure drop and the air jet penetration length of the novel air caps have been obtained and verified. Finally, in order to validate the innovative design of air caps, this methodology has been implemented to a full-scale 220 t/h CFB boiler. The hot test results depict that the thermal efficiency of the boiler has increased from 86.4% to 91.8% when tested with the novel air caps in-place, which is equivalent to a saving of 6000 tons of coal per year

Numerical investigation of harbor oscillations induced by focused transient wave groups

Focused wave groups are traveling waves characterized by extremely-large transient wave amplitudes and very short durations. These waves usually cause serious damage to marine/offshore structures and coastal infrastructures, and can even result in human casualties (Nikolkina and Didenkulova, 2011). The studies on natural disasters related to the focused wave groups near the coastal zone have been mostly confined to wave evolution over beaches, wave runup, overtopping, and their impact forces acting on the coastal infrastructures (e.g., the seawall and the circular cylinder); the influence of focused transient wave groups on harbors has not yet been studied. In this study, the generation and propagation of focused transient wave groups and their interactions with the harbor are simulated using a fully nonlinear Boussinesq model, FUNWAVE 2.0. To this end, four elongated harbors with constant depth and a series of focused wave groups with various focused wave amplitudes, spectral width parameters, and incident directions are considered. Based on the Morlet wavelet transform and discrete Fourier transform techniques, the capability of focused transient wave groups to trigger the harbor resonance phenomenon is revealed for the first time. Subsequently, the influences of spectral width parameter, incident wave direction, and resonant mode on different resonant wave parameters (including maximum runup and resonant intensity of various resonant modes inside a harbor) are comprehensively investigated, and it is found that these three factors have significant effects on resonant wave parameters.</p

Development of a novel methodology for calculating the thermal efficiency of clean fuel boilers based on error analysis method.

Clean fuel boilers often use natural gas and wood pellets as their primary fuel, which result in reduced emissions from the boiler. Accurate determination of the thermal efficiency of these boilers plays a vital role in appropriately controlling the process parameters for enhanced thermal performance of the boilers. The traditional methods for calculating the thermal efficiency of clean fuel boilers require a number of input parameters, which is not suitable for fast calculation of the thermal efficiency. Moreover, the conventional methods are often significantly inaccurate in the determination of the thermal efficiency of boilers. Thus, a novel method for rapid and accurate determination of boiler’s thermal efficiency is required. Therefore, using error analysis method, this study presents a novel mathematical model to calculate the thermal efficiency of an industrial boiler, fueled with natural gas and wood pellets. The main factors that affect the thermal efficiency of clean fuel industrial boilers are obtained based on the results of the thermal efficiency error analysis. A novel mathematical model to calculate the thermal efficiency of the boilers is developed as a function of these major factors. Finally, the calculated results, based on the model, are compared with the test values provided by Guangdong Special Equipment Inspection and Research Institute. The maximum deviation in comparative results has been observed to be within ±3%, indicating the appropriateness and commercial viability of the novel methodology proposed in this study

Experimental investigations on a grate incinerator of L-shaped flame fuelled by rural solid waste.

In this article, investigations on the structural parameters and aerodynamic characteristics of the furnace arches of a small scale L-shaped flame incinerator for the disposal of rural solid waste are carried out. A novel configuration of furnace arches for the incinerator of L-shaped flame is developed. Eight different test conditions are determined by using orthogonal experimental design method. Cold test with full coverage arch and sub-warehouse air supply are analyzed under eight different test conditions. Experimental results show that a stable combustion can be obtained by using L-shaped flame technology and the optimum air supply ratio between the front arch and the rear arch is discovered to be 3:7. It is found that the maximum turbulence intensity along the length of grate can reach 10%, and the burning exuberant zone is approximately 40%~75% of the whole relative length of the grate. The optimum dimensionless structural parameters of the furnace arch are: H/L = 0.333 and h/L = 0 .12 with the front arch angle of 45º. The effectiveness of configuration of arches as well as combustion air supply ratio for the L-shaped flame grate incinerator fueled by rural solid waste is verified by hot test