Cellular Premixed Flames of Synthetic Biogas Composition Effects on Flat Burner

To compare the effects of biogas compositions, cellular premixed flames of synthetic biogas on flat burner was investigated. As the variation of main composition of biogas such as methane (CH4) and carbon dioxide (CO2), the biogas produced from agricultural waste (54.9 : 45.1), food waste (73.4 : 26.6) and cow dung (85.1 : 14.9) were used to investigate for this study. Moreover, the lean combustion system was experimented on flat burner to reduce the greenhouse gases. The variation of equivalence ratio between Φ = 0.65 - 1.00 and firing rate with 45 L/min of mixture flow rates were studied. The results showed the cellular flame from agricultural waste, food waste and cow dung were found between Φ = 0.75 - 1.00, Φ = 0.70 - 0.90 and Φ = 0.65 - 0.80, respectively. In addition, the blown off flames were also observed at Φ < 0.75, Φ < 0.70 and Φ < 0.65 from agricultural waste, food waste and cow dung compositions, respectively. The results showed the variation of biogas compositions, equivalence ratio and firing rate affected to cellular flames owing to the intrinsic instability. Moreover, it was concluded that small cell size, higher light emission and narrower unstable range and wider flame range obtained in the combustion of biogas produced from cow dung composition, was more stable compared to biogas from agricultural waste and food waste compositions

Hydrogen-enriched natural gas as a domestic fuel: An analysis based on flash-back and blow-off limits for domestic natural gas appliances within the UK

In the effort to reduce carbon emissions from an ever-increasing global population, it has become increasingly vital to monitor and counteract the environmental impact of our domestic energy usage given its contribution to overall carbon emissions. To this end, hydrogen has emerged as a foremost candidate to offset and eventually replace the use of traditional gaseous fossil fuels. Hydrogen as the universal energy carrier or vector is easily produced from all forms of renewable or recovered energy as a storable, transportable commodity that can be used on demand, thus decoupling the supply from demand that is often considered to be the down-side of intermittent renewable energy usage. European trials have already been conducted to investigate the practical implementation of hydrogen-enriched natural gas (HENG) within a mains gas supply. In this work, the limitations of such a strategy are evaluated based on a novel meta-analysis of experimental studies within the literature, with a focus on the constraints imposed by the phenomena of flash-back and blow-off. Through consideration of the Wobbe Index, we discuss the relationship between molar hydrogen percentage and annual carbon dioxide output, as well as the predicted effect of hydrogen-enrichment on fuel costs. It is further shown that in addition to suppressing both blow-off and yellow-tipping, hydrogen-enrichment of natural gas does not significantly increase the risk of flash-back on ignition for realistic burner setups, while flash-back at extinction is avoided for circular port diameters of less than 3.5 mm unless the proportion of hydrogen exceeds 34.7 mol%. It is thus proposed that up to 30 mol% of the natural gas supply may be replaced in the UK with guaranteed safety and reliability for the domestic end-user, without any modification of the appliance infrastructure

Development of a high performance flexible porous burner (FPMB) with an adjustable cooling effect

A high performance flexible porous medium burner that can burn gaseous and liquid fuel with different type of flames (premixed and non-premixed) is proposed. The merit of the combustion within porous medium is that heat is recirculated from the combustion gas to porous medium at upstream wherein vaporization is taken place (in case of liquid fuel) or preheated (in case of gaseous fuel) before mixing with the combustion air followed by combustion within another porous medium at downstream. In a former version of the high performance flexible porous medium burner, the upstream porous medium is incorporated with a cooling system using the combustion air as a coolants to prevent thermal decomposition of fuels and thus the burner clogging caused by carbon deposit within the porous medium can be avoided. However, the cooling effect cannot be properly controlled such that the boiling point of the liquid fuel is maintained at suitable value irrespective of the volume flow rate of the combustion air, which is linearly varied with the firing rate of the burner. In particular at the lean burn condition, where high air flow rate is required with high cooling effect with porous medium. This can result in the porous medium temperature lower than the corresponding boiling point of the liquid fuel and thus evaporation of the fuel is failed and the combustion is ceased. Therefore, method of controlling the cooling air flow rate in the porous medium is proposed and studied in order to appropriately control the porous medium temperature and maintain it at above the boiling point irrespective of the combustion conditions. In this research, experimental and computation analysis are used to design the flexible porous burner (FPMB), with adjustable cooling effect. The result shows that, the new design of FPMB which has temperature in the upstream porous medium is higher than boiling point and lower than thermal decomposition temperature of fuel (kerosene) at all conditions and can be operated at a wide range of equivalence ratio without fuel decomposition and fuel non-vaporization problem

The application of ceramic stove cover and loading distance to the performance of water boiling system

Conventional gas stove (CGS) used in the water boiling system (WBS) is quite inefficient if the mechanism is not considered. In the present research, an assessment has been performed to a CGS by applying a ceramic stove cover (CSC) and also investigated the optimum distance between CSC and the loading to obtain very best efficiency of a CGS. Several parameters used to investigate the CGS’s performance such as water temperature, heating value of the fuel and temperature of CSC have been used in reference to the definition of efficiency. In this study the distance between CSC and the loading is varied by 1 mm to 7 mm by increment of 1 mm. The results show that at a distance of 4 mm, the performance of a CGS in a certain fuel rate of 12.5 cc/s increase significantly indicated by the best efficiency of 46.4 %. It is because of an optimum condition is accomplished simultaneously in heat transfer processes such convection and radiation in the WBS. Although the fuel rate itself have an influence to the flame structure heating the loading, however, the used of ceramic cover have an effect to the exchange between fresh air and flue gas to the combustion process