Şehir içi otobüslerde tekstil hava kanalı tasarımı

Abstract

Sanayileşmenin kaçınılmaz sonucu olarak şehirleşme tüm dünyada hızla gelişmektedir. Ancak bu gelişme beraberinde bazı sorunlar getirmektedir. Bu sorunlara ise ülkenin gelişmişliğiyle orantılı olarak çözümler üretilmeye çalışılmaktadır. Gelişen şehirlerdeki sorunların başında ulaşım sorunu gelmektedir. Bu soruna çözüm olarak sürekli yeni yollar yapmak sorunu çözecek gibi dursa da bunun kısa vadeli olduğu, uzun vadede insanları daha fazla araç almaya teşvik ettiği ve bu yöntemin yanlış olduğu anlaşılmıştır. Bu sebeple gelişmiş ülkelerde ulaşım sorunu insanları toplu taşımaya yönlendiren yatırımlar yaparak çözülmeye çalışılmıştır. Toplu taşımanın en başında karayolu taşımacılığı ve karayolunda da otobüs kullanımı gelmektedir. Bu çerçevede otobüs üreticilerinin, otomobillerinden feragat etmiş insanlar için konforlu bir ortam sunmak zorunda olduğu açıktır. Bu konfor elemanlarının başında da havalandırma sistemi gelmektedir. Bu çalışmada şehir içi otobüslerinden Mercedes-Benz Conecto aracının havalandırma sistemi için müşterinin talepleri doğrultusunda araç içi sıcaklık dağılımını daha düzenli hale getirecek ve kanal boyu basınç düşüşünü en aza indirecek ve böylece daha dengeli havalandırma sağlayacak bir sistemin araştırması yapılmıştır. Bu amaçla mevcut hava kanalı sistemi, bu sistemin müşteri özel isteğiyle verilen bir konstrüksiyonu ve asıl olarak da bu özel konstrüksiyonu daha ucuz, daha basit ve daha hafif üretmenin yolları araştırılmıştır. Bu doğrultuda itfaiye hortumlarının çalışma şeklinden ve piyasadaki basit uygulamalardan yola çıkarak tekstil hava kanalı fikri incelenip mevcut sistemle gerekli karşılaştırmaları yapılmıştır. Bu yeni uygulama çalışılırken başta DIN 1946-3 Yolcu Araçları ve Ticari Araçlar İçin İklimlendirme Standardı ile ASHRAE 62-1999 İç Mekanlar İçin Havalandırma Standardı olmak üzere kanal boyutları için ve debi ölçümü için ilgili normlar dikkate alınmıştır. Çalışmada seri durum olarak 'ayrık hava kanalı olmayan durum', müşteri özel isteği olarak 'ayrık ABS hava kanalı' ve yeni konstrüksiyon için 'ayrık tekstil hava kanalı' ifadeleri kullanılmıştır. Çalışmada seri durumdaki havalandırma sistemi ile müşteri özel isteği sonucu üretilen ayrık ABS kaplama hava kanalı konstrüksiyonu incelenip daha sonra ayrık tekstil hava kanalı bileşenlerinin neler olduğu, konstrüksiyonunda kullanılan bazı makina elemanlarının tayin edilme bilgileri yer almaktadır. Ayrıca mevcut durum ile yeni geliştirilen konstrüksiyonun karşılaştırmalı ağırlık ve maliyet verileri incelenmiştir. Son olarak da bu üç durum için yapılmış olan test verilerinin incelenmesinin yanında yeni konstrüksiyon için Star CCM+ Hesaplamalı Akışkanlar Dinamiği programında akış analizi yapılmış ve gerekli iyileştirmelere analiz sonucunda gidilmiştir. Gerek hesaplamalardan, gerek testlerden, gerekse de akış analizinden çıkan sonuçlara göre tekstil hava kanalı konstrüksiyonun daha ucuz, daha hafif, daha kolay monte-demonte edilebildiği ve üretilen havanın daha az kayıpla yolculara ulaştırılabildiği ortaya çıkmıştır.

Urbanization has developed all over the world as an inevitable consequence of the industrialization. However, this development brings with it some problems. For these problems, it is attempted to produce solutions related to the development of the country. Transport problem is one of the biggest problems in developing cities. As a solution to this problem, even though it seems that building roads constantly will solve the problem, it is understood that this method is short-dated, it incites people to buy more vehicles and it is wrong way to manage this problem. For this reason, it is tried to figure out the transport problem in developed countries by making investments to make people to use public transport. Overland transport is at the top of public transport and bus is the top of the overland transport. Therefore, it is evident that bus manufacturers have to present a comfortable environment for people who give up using their cars. In addition, one of the most important comfort components is ventilation system. Providing sufficient internal air circulation is one of the most important parameters for passenger comfort in intercity public transportation. Effectivity of ventilation and air conditioning in vehicles (Indoor Air Quality: IAQ) can be raised through optimally management of air that is released from air conditioning system in order to raise the passenger comfort to a higher level. Especially, considering vehicle manufacturers use air conditioners, which have similar properties, the importance of duct flow in vehicle air conditioning can be seen obviously. Within the project, which is supported by Mercedes Benz Turk A.Ş. , design of a new bus air duct system which ensures desired passenger comfort conditions with optimized air outlet properties is envisioned. For this purpose the present air duct system, a construction given by the special request of customer and essentially the way of producing this construction cheaper, easier and lighter is researched. Accordingly, based on the manner of work of fire hoses and the simple applications on the market, by examining the idea of the textile air duct, essential comparisons with present system has been made. While studying on this new air duct application, the norms, notably DIN 1946-3, the climatization standard for passenger vehicles and commercial vehicles, and ASHRAE 62-1999, the ventilation standard for interior spaces, have been taken into consideration for air flow rate and duct size. According to DIN 1946-3, the well-being of the person in the passenger compartment of a bus is determined by the influencing variables of temperature, air velocity, air humidity, radiation from components, radiation to and from the surrounding surfaces, direct solar radiation, noises, etc. In urban transportation, one of the most important parameter is undoubtedly to provide adequately the ventilation in vehicle. For bringing the passenger comfort at the highest level, by managing the air going out of air-conditioner most appropriately, the effects of the ventilation in vehicle and the climatization could be increased. The air duct, which forms the connection between the vehicle and the air conditioner, is the main factor for providing the air velocity outlet values and the air circulation accepted as reference values for passenger comfort. Especially, by taking into consideration that the vehicle manufacturers use the air conditioners which have the same features, the importance of the induct flow improvement has been seen obviously. In the study, the expressions 'non separate air duct' for in series, 'separate ABS air duct' for previous special request of customer, and 'separate textile air duct' for new construction, is used. In the study, air duct system in series and air duct construction with separate ABS covering which is produced as a result of the special request of customer have been examined and afterwards, textile air duct components, the informations about the assignment of some machine elements have taken place. Besides, the present situation and the comparative weight and cost data of newly developed construction are examined. In addition, air activity in concept duct geometry, which is designed as part of the project, is numerically computed using computational fluid dynamics (CFD) techniques by using STAR CCM+ computational fluid dynamic software and current concept is optimized repetitively. Passing of conditioned air from air duct into vehicle interior is simulated and investigated. Changes, which are desired for optimization of concept air duct geometry is done repetitively with respect to assessment of simulation results and duct geometry that provides optimal channel outlet flow conditions are obtained. For analysis, the steady state incompressible Reynolds-averaged Navier-Stokes equations, K- ε turbulence model and the finite volume method are used. According to the examination within preliminary research of the project, it is observed that patents about constructive designs of public transport vehicle's air duct systems have been found. In accordance with the examinations, it is concluded that in terms of the duct geometry and construction, new air duct design, which is predicted as a part of the project, has a patent potential. The project could be secured by patent with the necessary changes of the optimization studies, following the different designs. In addition, integration of new textile air duct concept to newly developed vehicles, whose mass production starts in 2017, which are produced for very hot countries or vehicles that are still being developed is envisioned. As a result of this study and tests, it is seen from prototypes that this new textile air duct design is cheaper than previous air duct design. In addition, separated ABS air duct construction is heavier than this new textile air duct construction. For replacement parts, it is easier to manage new design. One of the advantages of textile air duct is, while assembling this duct, there is no need to disassemble the front window. Because separated ABS air duct parts are 9 meters extrusion parts, it is hard to assemble. Moreover, if some problems occur, first of all front window must be disassembled and after that ABS air duct can be taken off. With this proses, there could be some damages and corrosions to front body. As a continuation of this study, a more detailed calculation of the machine elements can be used, so losses in duct can be reduced. Thus, a better quality of airflow can be provided. Seals used in duct can be examined in detail and with this, would have avoided the dangers that may occur in the future, such as tearing.