Ağir Hizmet Araci Fren Diski Soğuma Davranişinin İncelenmesi

Bu çalışmada, ağır hizmet araçlarında kullanılan havalandırmalı fren disklerinin farklı havalandırma kanatçığı geometrileri için soğuma davranışı incelenmiştir. İlk aşamada, deneysel taşınım katsayısı değerleri farklı dönüş hızları için bilinen, standart (konikleşme engelleyici olmayan) ağır hizmet aracı fren diskinin hesaplamalı akışkanlar dinamiği (HAD) analizleri gerçekleştirilmiştir. Sayısal olarak hesaplanan ortalama taşınım katsayısı değerleri ile deneysel sonuçlar karşılaştırılarak HAD analizi değişkenleri doğrulanmıştır. Sayısal ve deneysel ortalama taşınım katsayıları arasındaki korelasyon % 99.9 olarak hesaplanmıştır. İkinci aşamada, konikleşme engelleyici düz havalandırma kanatçıklı ağır hizmet aracı fren diskinin (referans) soğuma başarımı sayısal olarak incelenmiştir. Referans fren diskinin soğuma süresi değerleri, farklı araç hızları için atalet dinamometresi deneyleri ile elde edilmiştir. Referans havalandırmalı fren diskinin ortalama taşınım katsayısı, HAD analizleri ile hesaplanmıştır. Zamana bağlı disk sıcaklıklarını ve soğuma sürelerini elde etmek için taşınım ve ışınım etkileri göz önünde bulundurularak referans fren diskinin zamana bağlı termal analizleri gerçekleştirilmiştir. Sayısal ve deneysel soğuma süresi sonuçları karşılaştırılarak, termal analiz değişkenleri doğrulanmıştır. Doğrulama sonucunda, sayısal ve deneysel soğuma süreleri arasında % 97.9’a varan bir korelasyon elde edilmiştir. Yeni bir havalandırma kanatçığı geometrisi önerilerek, konikleşme engelleyici fren diski geometrisine uyarlanmıştır. Yeni kanatçık geometrisine sahip diskin HAD ve termal analizleri gerçekleştirilerek, ortalama taşınım katsayısı ve soğuma süresi sonuçları referans fren diski ve ağır ticari araçlarda kullanılan diğer bir fren diski ile karşılaştırılmıştır. Önerilen fren diski tasarımı ile referans havalandırmalı fren diski tasarımı karşılaştırıldığında, ortalama taşınım katsayısında % 18.5 artış ve soğuma süresinde % 23.5 iyileşme elde edilmiştir. Bu çalışmada, ilk olarak, ağır hizmet aracı fren disklerinin atalet dinamometresi üzerindeki soğuma süresi deneyleri sayısal olarak modellenmiş ve deneysel veriler kullanılarak doğrulanmıştır. Sonrasında, farklı havalandırma kanatçıklarının fren diski soğuma süresine etkisi araştırılmıştır. Bu sayede, literatüre katkı sağlanmıştır.

Anahtar Kelimeler:

havalandırmalı fren diski, HAD analizi, zamana bağlı termal analiz, atalet dinamometresi, ağır hizmet aracı

INVESTIGATION OF HEAVY-DUTY VEHICLE BRAKE DISC COOLING BEHAVIOUR

In this study, cooling behaviour of ventilated brake disc which is used in heavy-duty vehicles was investigated for different ventilation vane geometries. In the first stage, computational fluid dynamics (CFD) analyses were conducted on a standard (non-anticoning) heavy-duty brake disc whose experimental convective heat transfer coefficients are known different rotational speeds. The CFD analysis parameters are verified by comparing the numerically calculated average convective heat transfer coefficient values with the experimental results. The correlation between numerical and experimental average convective heat transfer coefficients was calculated as 99.9 %. In the second stage, the cooling performance of anticoning heavy-duty disc (reference) with straight ventilation vanes were investigated numerically. The cooldown period values of reference brake disc were measured by inertia dynamometer experiments for different vehicle speeds. Average convective heat transfer coefficient of reference ventilated brake disc was calculated by CFD analyses. To obtain time dependent disc temperatures and cooldown periods, transient thermal analyses of reference brake disc were conducted by consideration of convection and radiation effects. The thermal analysis parameters are verified by comparing the numerical and experimental cooldown period results. As a result of the verification, a correlation between numerical and experimental cooldown periods was obtained up to 97.9 %. A new ventilation vane geometry was proposed and adopted to anticoning brake disc geometry. The CFD and thermal analyses of disc with new ventilation vane geometry were carried out and the average convective heat transfer coefficient and cooldown duration results were compared with the reference brake disc and another brake disc used in heavy commercial vehicles. In comparison of the proposed brake disc design with the reference ventilated brake disc design the average convective heat transfer coefficient was increased by 18.5 % and the cooldown period was improved by 23.5 %. In this study, firstly, the cooldown period experiments of heavy-duty vehicle brake discs on inertia dynamometer were modelled numerically and verified by using experimental data. After that, the effect of different ventilation vanes on the brake disc cooldown period was investigated. In this way, the contribution has been provided to the literature.

Keywords:

ventilated brake disc, CFD analysis, transient thermal analysis, inertia dynamometer, heavy-duty vehicle,

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