Sentetik yakıtların sandia D yakıcısında yanma karakteristliğinin incelenmesi
Investigation of the combustion characteristics of synthetic fuels in sandia D burner
- Tez No: 953197
- Danışmanlar: PROF. YAKUP ERHAN BÖKE
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2022
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: Makine Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Isı-Akışkan Bilim Dalı
- Sayfa Sayısı: 91
Özet
Kömür, doğalgaz, petrol ürünleri gibi fosil yakıtların kullanılmasının enerji üretimi için büyük bir avantaj sağlarken, diğer yandan dezavantajı ise yanma sonucu karbon dioksit (CO2), metan (CH4) gibi sera etkisi yaratan gazların oluşmasıdır. Bu gazlar dünyanın atmosfer tabakasında bir katman oluşturarak hava kalitesinin bozulmasına ve aynı zamanda güneşten gelen ışınların yeryüzüne çarptıktan sonra atmosferden çıkmasını engelleyerek dünyanın sıcaklığının artmasına ile canlıların hayatı için önemli bir risk oluşturmaktadır. Bu amaç doğrultusunda, dünyanın enerji kaynağının gelecek yıllar için de varlığını korunması ve canlı yaşamının devamı için temiz yanma teknolojileri çok önemlidir. Temiz yanma teknolojisinde, hidrojen, karbon monoksit ve karbon dioksit karışımı olan sentez gazlar kullanılarak yanma verimi ve emisyon gazlarında iyileşme elde edilir. Sentez gaz ile ilgili literatürde birçok araştırma yapılmıştır. Yapılan araştırmalarda sentez gaz bileşenine farklı oranlarda oksijen, karbon dioksit gazı eklenerek hem deneysel çalışmalar hem de sayısal çözümler yapılmıştır. Yapılan çalışmalar sonucunda sentez gaza eklenen bu kimyasal bileşenler ile yanma işleminden alınan verim artırılmış veya emisyon gazlarındaki değerlerde düşüş yaşanmıştır. Aynı zamanda baca gazı sıcaklığı, alev sıcaklığında da gazın durumuna göre değişiklikler yaşanmıştır. Bu çalışmada kullanılan yakıcı olan pilot yakıcı geometrisi Sydney Üniversitesi tarafından geliştirilmiştir. Yakıcıda kullanılan Alev D, Sandia Laboratuvarları tarafından geliştirilen ve farklı serileri bulunan pilot metan-hava jet alevlerden biridir ve 1998 yılında 3. türbülanslı alev çalıştayında (TNF3 Workshop Series) ortaya yayınlanmıştır. Basit geometri yapısına karşılık kapsamlı bir veri setine sahiptir. Alev D üzerine yapılan birçok makale ve yayının konusu olmuş ve aynı zamanda yapılan yanma modellemeleri için doğrulama çalışması olarak kullanılmıştır. Bu çalışmada ANSYS Fluent HAD programı kullanılmıştır. Sayısal modellemede realizable türbülans modeli kullanılmıştır. Kimyasal çözümleme için Species transfer methodu kullanılırken, Eddy-dissipation konsept modeli seçilerek, GRI-MECH 3.0 kimyasal çözümleyici sisteme eklenmiştir. Radyasyon modeli olarak ayrık ordinatlar metodu kullanılmıştır. Sandia Alev D sayısal modelleme sonuçları deneysel sonuçlar ile karşılaştırılarak model doğrulaması yapılmıştır. Doğrulanan model kullanılarak farklı hidrojen ve karbon monoksit oranlarındaki altı sentez gazı için yanma sayısal olarak çözülmüştür. Elde edilen sonuçlardan, eksenel hız, sıcaklık, kütlesel oran olarak CO, H2O ve CO2 verileri karşılaştırılarak yorumlanmıştır. Sentez gazın içeriğine bağlı olarak alev hızının artması, alev sıcaklığının yükselmesi ve emisyon gazlarının konsantrasyonunda düşüşler gözlemlenmiştir.
Özet (Çeviri)
With the developing technology, the energy consumption of human beings is increasing day by day and the level of dependence on energy is increasing. Basically, most of our energy needs are obtained by consuming fossil hydrocarbon resources. We should be more careful when using these very precious non-renewable energy resources given to us by nature, and at the same time, we should use and continue to develop more efficient energy production methods and transfer the world's existing fossil fuel resources to the next generations. Coal, natural gas, petroleum products, such as the use of fossil fuels for energy production provides a great advantage, while on the other hand, its disadvantage is the formation of greenhouse gases such as carbon dioxide (CO2) and methane (CH4) as a result of combustion. These gases create a layer in the earth's atmospheric layer, causing air quality to deteriorate, as well as increasing the temperature of the earth by preventing the rays from the sun from leaving the atmosphere after they hit the earth, posing a significant risk to the life of living things. For this purpose, clean combustion technologies are very important for the preservation of the world's energy source for the coming years and for the continuation of life. In clean combustion technology, combustion efficiency and emission gas improvement are achieved by using synthesis gases that are a mixture of hydrogen, carbon monoxide and carbon dioxide. Many studies have been conducted in the literature on synthesis gas. In the researches, both experimental and numerical solutions were made by adding different amounts of oxygen and carbon dioxide gases added to the synthesis gas component at different rates. As a result of the studies, these chemical components added to the synthesis gas increased the efficiency obtained from the combustion process or decreased the values in the emission gases. At the same time, the flue gas temperature and the flame temperature also experienced changes according to the state of the gas. The burner used in this study was developed by the geometry of the pilot burner developed by the University of Sydney. Flame D, which is used in the burner, is one of the pilot methane-air jet flames developed by Sandia Laboratories and has different series and emerged in the 3rd turbulent flame workshop (TNF3 Workshop Series) in 1998. It has a comprehensive data set as opposed to a simple geometry structure. In many articles and publications, many studies have been done for flame d and it has also been used as a validation study for combustion simulations. The jet stream entering the burner reaches the combustion area by passing through a 7.2 mm inner diameter channel with a gas content of 25% methane and 75% air by volume. With the advantage of the Air-Fuel mixture, the accuracy rate in scalar measurement improves, it shortens the flame length and provides a stronger flame production compared to plain CH4 gas. The inlet velocity of the jet stream is 49,6 m/s and the Reynolds number calculated for the jet stream is 22400. Pilot flow is a flow that surrounds the jet flow. The speed of the pilot flow is 11,4 m/s and its temperature is 1880 K. During this study, the ANSYS Fluent module was used. The Sandia Flame D burner was modeled in two dimensions in the Ansys Fluent CFD program. In many studies with Sandia Flame D, geometry has been handled as two-dimensional and many different turbulence models and chemical reaction models have been used. Realizable turbulence model was used during the study. While Species transfer method was used for chemical analysis, Eddy-dissipation concept model was chosen and GRI-MECH 3.0 chemical analyzer was added to the system. The discrete ordinates method was used as the radiation model. The solution was verified by comparing the values obtained from the simulation of the Sandia Flame D, which was solved, with the experimental results. The solutions made should be independent of the density settings of the mesh. If this condition is not met, the solution will change proportionally with the size of the finite element and cause erroneous results to be found. In order to control this, experiments were carried out by creating meshes with different densities and comparing the results obtained, it was tried to determine the mesh density that could give the correct result regardless of the mesh. Experiments were conducted for six different mesh and compared with experimental data. Temperature, axial velocity, mass ratios of H2, CO, CO2 and CH4 were used in the comparison. Comparisons were made along the x-axis, with the x/d ratio at values of 7.5, 30 and 45. During this study, the combustion of 6 different synthesis gases in the Sandia Flame D geometry was numerically modeled. As a result of numerical modeling, the change of flame structure, temperature, velocity and emissions was studied. In numerical modeling with synthesis gases, the flow rates of fuels were determined to be equal to the burning power of the Sandia Flame D. The diameter of the jet flow inlet channel of the verification geometry has been changed to 10 mm because the inlet speeds generated during the flow rate adjustment of the syngases have reached very high levels. In order to see the effect of hydrogen, methane and carbon monoxide on the flame in the selected gas components, the methane and hydrogen ratios were changed in two different carbon monoxide ratios. In order to compare the results obtained, the results obtained from the synthesis gases, velocity, temperature, methane, hydrogen, carbon monoxide and carbon dioxide diagrams were prepared along the x-axis, where the x/d ratio is 7.5, 30 and 45. As a result of the studies, the flammability properties of the synthesis gas increase with the gases such as hydrogen and carbon monoxide added to the synthesis gas, and at the same time, decreases in the emission levels may occur. Depending on the content of the gas contained in the synthesis gas, changes can be made in properties such as the speed of the flow, the stability of the flame, its temperature, efficiency and flame length. In this study, it was seen that the ratios of syngas components changed the flame characteristics. The methane ratio is the biggest factor affecting the flame length, temperature and speed. The increase in methane content increases the flame width. As the proportion of hydrogen compound decreases in the syngas, the speed, temperature and width of the flame decrease. As the methane content of the synthesis gas increases and the hydrogen level decreases, the formation of emission gases increases. Compared to Sandia Flame D, the speeds reached by the syngas for the same combustible power are higher. According to the results obtained from the synthesis gases, while the damages of the gases released to the environment can be reduced, it is possible to use fossil fuels, which are a limited resource, more efficiently.
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