Mil kaplama kalınlığının otomotiv turboşarjının dinamik davranışlarına etkisi
Küçük Resim Yok
Tarih
2024
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Düzce Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Turboşarj, otomotiv motorlarına takılan, atmosferik basınçtaki havayı alıp, daha yüksek bir basınca sıkıştırıp, giriş valfleri aracılığıyla basınçlı havayı motora vererek performansı ve verimliliği artırmak için kullanılan sistemdir. Çoğu durumda kaymalı yataklarla desteklenen bir mille birbirine bağlanan türbin ve kompresör pervanesinden oluşur. Mil, turboşarj sisteminin en önemli bileşenlerinden biridir ve yüksek hızda çalışır. Mil titreşimleri doğal bir olgudur ve çevredeki yapıya doğru hareket ederek turboşarj sisteminin kararlılığını ve güvenilirliğini etkiler. Sistemin titreşimini etkileyen parametreler arasında uygun mil malzemesi özelliğinin seçimi kritik bir parametredir. Bu çalışma, AISI 4140 alaşımlı çelikten imal edilen mil için her biri sırasıyla 2, 4 ve 6 µm kalınlığa sahip Alüminyum Krom Nitrür (AlCrN), Titanyum Nitrür (TiN) ve Alüminyum Titanyum Nitrür (AlTiN) dahil olmak üzere farklı türdeki kaplama malzemeleri kullanılarak mil titreşiminin azaltılmasının mümkün olup olmadığını araştırmaya odaklanmaktadır. Kaplamalı ve kaplamasız turboşarj milinin rezonans frekansları, sönümleme ve mod şekilleri gibi doğal titreşim özellikleri, turboşarj milinin önceden tanımlanmış bir matematiksel modeli kullanılarak verilerin eğriye uydurulmasıyla ilgili olan Frekans Tepki Fonksiyonu ölçümleri yoluyla Deneysel Modal Analiz yapılarak elde edildi. Sonuçlar Sonlu Elemanlar Yöntemi ile sayısal olarak doğrulandı. Genel sonuçlardan, AlCrN, TiN, AlTiN kaplama kalınlıklarının rezonans frekansları üzerinde küçük bir etkiye sahip olduğu, ancak iyi bir sönümleme etkisi olduğu gözlemlendi. Turboşarj milinin rezonans frekanslarındaki rezonans tepkisi, özellikle sırasıyla 6 ve 4 µm kalınlığa sahip AlCrN ve AlTiN kaplama ile önemli ölçüde bastırıldığı gözlemlendi. Ayrıca AISI 4140 mil malzemesi özelliklerinde 70 adet numune hazırlanarak 2, 4 ve 6 µm kalınlığa sahip AlCrN, TiN ve AlTiN kaplamaların mekanik ve tribolojik özellikleri incelendi. Kaplama yüzeyi, numune kesitinden kaplama kalınlığı ve aşınmış yüzeyler taramalı elektron mikroskobu (SEM) ile analiz edildi. X-Işını difraksiyonu ile PVD kaplamaların faz yapıları analizi edildi ve kaplamaların kristal boyutu ve kafes bozulması hesaplandı. Kaplamalara mikro sertlik testleri yapıldı. Tribolojik ölçümler için yağlı ve yağsız ortamlarda pi-on-disk testleri yapıldı. Test sonuçlarına göre; kaplamaların aşınma oranı ve sürtünme katsayısında azalmaya neden olduğu görüldü. Yağlı ortamda 2 µm, yağsız ortamda 4 µm kalınlığa sahip sırasıyla TiN ve AlCrN kaplamaların en düşük sürtünme katsayısına sahip olduğu görüldü. Maksimum sertliğe ve güçlendirme içeriğine sahip 6 µm kalınlığındaki TİN kaplamanın en düşük aşınma iz genişliği gösterdiği görüldü.
Turbocharger is a system that fitted to automotive engines for increasing performance and efficiency by taking air at atmospheric pressure, compressing to a higher pressure and passing the compressed air into the engine via the inlet valves. It consists of a turbine and a compressor impeller interconnected with a shaft supported in most cases by journal bearings. The shaft is one of most crucial component of turbocharger system and it operates at high speed. The shaft vibrations are inherent phenomenon and they are travelling to the surrounding structure effecting the stability and reliability of the turbocharger system. Selection of appropriate shaft material property is critical parameter amongst the parameters that affect vibration of the system. This study focuses on exploring whether it is possible to reduce the shaft vibration using different types of coating materials including Aluminum Chromium Nitride (AlCrN), Titanium Nitride (TiN) and Aluminum Titanium Nitride (AlTiN) each having thickness 2, 4, and 6 µm respectively for the shaft made of AISI 4140 alloy steel. The inherent natural vibration properties such as the resonant frequencies, damping, and mode shapes of the turbocharger shaft with and without coating were obtained by conducting the Experimental Modal Analysis through the measurements of Frequency Response Function which is about curve fitting the data using a predefined mathematical model of turbocharger shaft. The results were validated numerically by Finite Element Method. From overall results, it was observed that AlCrN, TiN, AlTiN coating thicknesses have a small effect on the resonant frequencies, but a good damping effect. The resonant response of the turbocharger shaft at resonant frequencies was suppressed remarkably by AlCrN and AlTiN coating especially having thickness of 6 and 4 µm respectively. In addition, 70 specimens of AISI 4140 shaft material were prepared and the mechanical and tribological properties of AlCrN, TiN and AlTiN coatings with thicknesses of 2, 4 and 6 µm were investigated. The coating surface, coating thickness from the specimen cross-section and worn surfaces were analyzed by scanning electron microscopy (SEM). The phase structures of PVD coatings were analyzed by X-ray diffraction and the crystal size and lattice distortion of the coatings were calculated. Microhardness tests were performed on the coatings. For tribological measurements, pi-on-disc tests were performed in oil and oil-free environments. In abrasion tests, the coatings were kept at 25±1 °C with 30%-40% relative humidity under a contact load of 5 N and the results were analyzed. According to the test results; it was observed that the coatings caused a decrease in wear rate and friction coefficient. TiN and AlCrN coatings with a thickness of 2 µm in lubricated and 4 µm in non- lubricated, respectively, had the lowest coefficient of friction. The 6 µm thick TiN coating with maximum hardness and reinforcement content showed the lowest wear track width.
Turbocharger is a system that fitted to automotive engines for increasing performance and efficiency by taking air at atmospheric pressure, compressing to a higher pressure and passing the compressed air into the engine via the inlet valves. It consists of a turbine and a compressor impeller interconnected with a shaft supported in most cases by journal bearings. The shaft is one of most crucial component of turbocharger system and it operates at high speed. The shaft vibrations are inherent phenomenon and they are travelling to the surrounding structure effecting the stability and reliability of the turbocharger system. Selection of appropriate shaft material property is critical parameter amongst the parameters that affect vibration of the system. This study focuses on exploring whether it is possible to reduce the shaft vibration using different types of coating materials including Aluminum Chromium Nitride (AlCrN), Titanium Nitride (TiN) and Aluminum Titanium Nitride (AlTiN) each having thickness 2, 4, and 6 µm respectively for the shaft made of AISI 4140 alloy steel. The inherent natural vibration properties such as the resonant frequencies, damping, and mode shapes of the turbocharger shaft with and without coating were obtained by conducting the Experimental Modal Analysis through the measurements of Frequency Response Function which is about curve fitting the data using a predefined mathematical model of turbocharger shaft. The results were validated numerically by Finite Element Method. From overall results, it was observed that AlCrN, TiN, AlTiN coating thicknesses have a small effect on the resonant frequencies, but a good damping effect. The resonant response of the turbocharger shaft at resonant frequencies was suppressed remarkably by AlCrN and AlTiN coating especially having thickness of 6 and 4 µm respectively. In addition, 70 specimens of AISI 4140 shaft material were prepared and the mechanical and tribological properties of AlCrN, TiN and AlTiN coatings with thicknesses of 2, 4 and 6 µm were investigated. The coating surface, coating thickness from the specimen cross-section and worn surfaces were analyzed by scanning electron microscopy (SEM). The phase structures of PVD coatings were analyzed by X-ray diffraction and the crystal size and lattice distortion of the coatings were calculated. Microhardness tests were performed on the coatings. For tribological measurements, pi-on-disc tests were performed in oil and oil-free environments. In abrasion tests, the coatings were kept at 25±1 °C with 30%-40% relative humidity under a contact load of 5 N and the results were analyzed. According to the test results; it was observed that the coatings caused a decrease in wear rate and friction coefficient. TiN and AlCrN coatings with a thickness of 2 µm in lubricated and 4 µm in non- lubricated, respectively, had the lowest coefficient of friction. The 6 µm thick TiN coating with maximum hardness and reinforcement content showed the lowest wear track width.
Açıklama
Anahtar Kelimeler
Makine Mühendisliği, Mechanical Engineering
