Biogas as a "Powergas" is an alternative fuel produced in digestion facilities, that is sustainable and renewable. Given it has a different composition to traditional fuels. A fundamental study of biogas flame propagation characteristics is desirable to quantify this important fuel property. Spherically expanding flames propagating at constant pressure are employed to measure the laminar burning velocity and flammability characteristics as mixture function of the mixture composition. These important parameters were measured using a photographic technique in a high pressure fan-stirred bomb. The characteristics of biogas-air flames were initially studied at reduced pressure and at various equivalence ratios from the lower flammable limit to the upper flammable limit. The results were compared with those from biogasair flames at atmospheric pressure and also methane-air flames, both at reduced and atmospheric pressures. Based on this experimental investigation, the laminar burning velocities of biogas-air mixtures at reduced pressure were 0.2219 m/s for ϕ=0.75, 0.2463 m/s for ϕ=0.80 and 0.2705 m/s for ϕ=0.85 respectively and only for these biogas mixtures propagated at reduced pressure. At the same equivalence ratio (ϕ), the laminar burning velocities of the biogas-air mixtures at reduced pressure is higher than those at atmospheric pressure, the flammable region of biogas becomes narrower in the presence of inhibitors (carbon dioxide and nitrogen) and the presence of inhibitors also causes a reduction in the laminar burning velocity. In addition, the flammable region of biogas became narrower by reducing initial pressure. The dilution effect is stronger at reduced pressure. Therefore, the flammable composition mixture areas of biogas-air mixtures are more limited at reduced pressure than those at atmospheric pressure. The inhibitor gases work more effectively in rich mixtures because the rich biogas-air mixtures have a higher fraction of carbon dioxide and nitrogen components compared to those for lean biogas-air mixtures. Highlights► A fundamental study of biogas laminar burning velocity and flammability characteristics is required before it can become a major sustainable fuel. ► The impact of impurites as inhibitors behavior in biogas on laminar burning velocity and flammability characteristics is understood better at reduced pressure ► At reduced pressure flammable region of biogas becomes narrower and its laminar burning velocities is higher than those at atmospheric pressure ► Inhibitors reduce the laminar burning velocity and make the flammable region narrower ► The dilution effect is stronger at reduced pressures.
Article InfoUtilization of crude palm oils (CPO) as biodiesel faces difficulty due to their high level of viscosity. Mixing crude eucalyptus oils (CEO) with CPO may reduce the viscosity due to the presence of aromatic compounds in CEO. The single droplet analysis was performed to determine the characteristics of mixing CPO with the CEO. The results showed that the addition of CEO decreased the viscosity due to the presence of intermolecular attractions, thereby leading to more active molecules in the CPO-CEO mixture. Furthermore, the aromatic compound in the CEO helped in decreasing the CPO flash point, while the aromatic compound in the triglyceride molecule weakens the bonds between molecules. The addition of CEO to CPO tends to reduce the ignition delay due to the presence of cineol content in the CEO, which weakens the van der Waals bond in CPO. AbstrakMinyak sawit (CPO) sebagai bahan bakar biodiesel memiliki viskositas yang tinggi, sehingga perlu penanganan untuk mengurangi viskositasnya. Perpaduan minyak kayu putih (CEO) dengan minyak sawit dapat menurunkan nilai viskositas minyak sawit karena adanya senyawa aromatik di dalam minyak kayu putih. Analisa tetesan (single droplet analysis) telah dilakukan untuk menentukan karakteristik campuran dari minyak sawit dengan minyak kayu putih. Penambahan minyak kayu putih menghasilkan penurunan viskositas karena interaksi antar molekul yang saling tarik-menarik. Interaksi ini menghasilkan pergerakan molekul yang lebih aktif pada campuran minyak sawit -minyak kayu putih. Penambahan minyak kayu putih menurunkan titik nyala bahan bakar. Senyawa aromatik dalam minyak kayu putih menjadi faktor utama yang membantu mengurangi nilai titik nyala pada minyak sawit; senyawa aromatik dalam molekul trigliserida menyebabkan ikatan antar molekul menjadi lemah. Penambahan minyak kayu putih pada minyak sawit menghasilkan pengurangan waktu tunda pengapian karena adanya senyawa Cineol pada minyak kayu putih yang melemahkan ikatan van der Waals dalam minyak sawit. Kata-kata kunci: Minyak kayu putih, Minyak sawit, Biodiesel, Droplet
Biogas is a mixture of gases which commonly consists of methane (up to 50%) and other inhibitor gases which are dominated by carbon dioxide (up to 50%). Biogas is produced naturally by the decomposition of organic materials such as vegetation or animal manure in the absence of oxygen and it also contributes less greenhouse gases which may lead to global warming or climate change. The presence of carbon dioxide (CO2) in biogas is presumed to have some effects on biogas flame propagation characteristics. This study focuses on the effect of carbon dioxide (CO2) as the biggest inhibitor composition in biogas on flame propagation speed as the important flame propagation characteristic in spark ignited premix combustion. Propagating flames are employed to measure the flame propagation speed as a function of the mixture composition. This parameter was measured using a transparent tube fuel chamber with dimensions of 60 mm inner diameter and 300 mm height based on DIN 51649 standards and recorded by high speed digital photographic technique. The characteristic of biogas-oxygen flames were studied at stoichiometric, room temperature and atmospheric condition from 0% to 50% CO2 biogas inhibitor composition increased by 10% for each experiment. The results showed that the carbon dioxide decreases flame propagation speed of biogas. These indicated that carbon dioxide reduced reaction rate of biogas premixed combustion.
Biogas is an alternative energy source that is sustainable and renewable containing more than 50% CH 4 and its biggest impurity or inhibitor is CO 2. Demands for replacing fossil fuels require an improved fundamental understanding of its combustion processes. Flammability limits and laminar burning velocities are important characteristics in these processes. Thus, this research focused on the effects of CO 2 on biogas flammability limits and laminar burning velocities in spark ignited premixed combustion. Biogas was burned in a spark ignited spherical combustion bomb. Spherically expanding laminar premixed flames, freely propagating from spark ignition in initial, were continuously recorded by a high-speed digital camera. The combustion bomb was filled with biogas-air mixtures at various pressures, CO 2 levels and equivalence ratios (ϕ) at ambient temperature. The results were also compared to those of the previous study into inhibitorless biogas (methane) at various pressures and equivalence ratios (ϕ). Either the flammable areas become narrower with increased percentages of carbon dioxide or the pressure become lower. In biogas with 50% CO 2 content, there was no biogas flame propagation for any equivalence ratio at reduced pressure (0.5 atm). The results show that the laminar burning velocity at the same equivalence ratio declined in respect with the increased level of CO 2. The laminar burning velocities were higher at the same equivalence ratio by reducing the initial pressure.
In order to reduce the use of fossil fuel without interfering the availability of food crop, Cerbera manghas biodiesel has been studied as potential renewable fuel. This study investigated Cerbera manghas biodiesel as a replacement for pure petro-diesel and palm oil biodiesel produced in Indonesia. The investigation result indicates that Cerbera manghas biodiesel fuel has a lower density, kinematic viscosity, sulfur content, color (lighter), water content, distillation point compared to pure petro-diesel and palm oil biodiesel. Higher flash point and cetane index value in Cerbera manghas biodiesel were also discovered. The study investigated further the effect of biodiesel derived from Cerbera manghas biodiesel compared with pure petro-diesel and palm oil biodiesel in a single cylinder diesel engine. The study suggested that Cerbera manghas biodiesel has better engine performance (fuel consumption, brake mean effective pressure, thermal efficiency, torque, and power) compared to pure petro-diesel and palm oil biodiesel. The utilization of Cerbera manghas biodiesel gave better engine performance output compared to pure petro-diesel and palm oil biodiesel. This study supported the viability of Cerbera manghas biodiesel to be implemented as an alternative diesel fuel without interfering food resources or requiring additional modification to the existing diesel engine.
As a renewable and sustainable fuel made from digestion facility, biogas is composed predominantly of methane (CH4) and carbon dioxide (CO2). CO2 in biogas strongly affects its combustion characteristics. In order to develop efficient combustors for biogas, fundamental flame characteristics of biogas require extensive investigation. In understanding the influence of CO2 concentration and mixture pressure on biogas combustion, the effects of CO2 concentration on the laminar burning velocity of methane/air mixtures were studied at different pressures. The studies were conducted using both numerical and experimental methods. The experiment was conducted using a constant volume high pressure combustion chamber. The propagating flames were recorded with a high speed digital camera by employing Schlieren photography technique. The numerical simulation was carried by utilizing CHEMKIN-PRO with GRI-Mech 3.0 employed as the chemical kinetics model. The results show that the laminar burning velocity of methane-air mixtures decreased with an increase in CO2 concentration and mixture pressure. Therefore, the burning velocity of biogas mixtures may decrease as the amount of CO2 in the gas increases.
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