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    Adyabatik Soğutma Sistemlerinde Nozul Yapısının Soğutma Performansına Etkilerinin Teorik ve Deneysel İncelenmesi
    (2016) Gürel, Ali Etem; Yıldız, Abdulaziz; Deniz, Emrah
    Küresel ısınma, yaşam standartlarındaki artış vb. etkenler soğutma ve iklimlendirme sistemlerine olan talebi her geçen gün artırmaktadır. Bu sistemlerin performanslarının artırılmasına yönelik farklı yöntemler kullanılmaktadır. Bu yöntemlerden biri de soğutma sistemlerinde evaporatif kondenser kullanımıdır. Bu çalışmada, soğutma sistemlerinde evaporatif kondenser kullanımının sistem performansına olan etkileri deneysel olarak analiz edilmiştir. Deneysel sistemin kondenser ünitesi adyabatik nemlendirme yöntemi ile soğutulmuştur. Adyabatik nemlendirme işlemi 0.2, 0.3 ve 0.4 mm çaplarında nozullar kullanılarak gerçekleştirilmiştir. Sistem, hava soğutmalı kondenser kullanımı ve farklı nozul çapları için termodinamik olarak analiz edilmiş, sistemin soğutma performansları karşılaştırılmıştır. Elde edilen veriler evaporatif kondenser kullanımıyla, kompresör işinde %8.48 azalma, soğutma sistemi COP değerinde %32.92 ve tüm sistemin COP değerinde ise, %18.43 artış olduğunu göstermiştir
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    The effect of the CO2 ratio in biogas on the vibration and performance of a spark ignited engine
    (Elsevier Sci Ltd, 2018) Karagöz, Mustafa; Sarıdemir, Suat; Deniz, Emrah; Çiftçi, Burak
    Being a renewable fuel, biogas can be produced either through anaerobic digestion from animal manure, inedible seed residue, food waste, agricultural waste, domestic waste and sewage sludge or through thermo-chemical processes. Along with thermal applications, by means of combustion inside an engine, biogas can produce both mechanical and electric energy. Depending on the inertia forces of the active parts and the characteristics of the in-cylinder combustion of the engine, vibration can be quite a big problem because it leads to rapid breakdown of engine parts, noisy operation and decreased performance and power output. The CO2 in biogas is an important compound that affects its lower heating value (LHV), burning characteristics and exhaust emissions. There are a limited number of studies in the literature on the effect of biogas CO2 content on engine vibration. In the present study, a four-cylinder diesel engine was modified to operate with a spark plug and used to detect the effect of the biogas CO2 content on the vibration of the engine. The experiments were carried out with biogas containing 13% and 49% CO2 at 1.5-9 kW with 1.5 kW load increments at a steady 1500 rpm speed. The amplitude of the engine vibration at all three axes increased as the CO2 ratio in the biogas and the engine load increased. On the other hand, by decreasing the CO2 ratio and increasing the engine load, cylinder pressure increased and brake specific fuel consumption decreased. The highest amplitude of engine vibration for all loads was observed at the lateral axis.
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    An experimental assessment of combustion and performance characteristics of a spark ignition engine fueled with co-fermentation biogas and gasoline dual fuel
    (Sage Publications Ltd, 2021) Agbulut, Umit; Aydin, Mustafa; Karagoz, Mustafa; Deniz, Emrah; Ciftci, Burak
    Natural gas, biogas and alcohols are alternative fuels for spark ignition engines which can be used for reducing exhaust emissions and improving performance metrics. At the first stage of the study, a pilot scale biogas system was built, and biogas was produced from a mixture of manure and water called slurry, consisting of 40% cattle manure, 35% water, 17% whey and 8% poultry manure by co-fermentation method. Scrubbing and desulfurization were applied to remove the harmful gasses (CO2, H2S) from the produced biogas in two stages. In the end of the purification process, biogas with a CH4 content of 51%, 57% and 87% was produced. In the second stage, these biogas fuels were used in an SI engine, and their impacts on performance and combustion characteristics were investigated experimentally. A 4-cylinder, 4-stroke, water cooled SI engine with an 11:1 compression ratio was used in the experiments. Tests were conducted at various loads and constant speed. Results showed that daily amount of mean biogas production has reached 1.6 m(3)/day and biogas methane content has reached 72%. In engine tests, as the methane ratio in biogas increases, cylinder pressure and exhaust temperature values increase and brake specific fuel consumption decreases.