Tiki haagise aerodünaamiline analüüs

Käesoleva lõputöö eesmärgiks oli leida haagise juures elemendid, mis mõjutavad selle aerodünaamilist efektiivsust. Selle tarbeks kasutati voolavusanalüüsi tarkvara Simscale. Seetõttu ei tehtud lõputöö käigus päriselulisi katseid, kuna oli vaja leida elemendid, millega on mõtet hiljem katseid sooritada. Töö alguses seadis autor omale 4 põhilist hüpoteesi. Esimene hüpoteesi oli, et siledad haagise poordid ja kinni kaetud põhi vähendavad autorongi õhutakistustegurit. Vooluanalüüside tulemused kinnitasid, et siledad poordid ja sile põhi parandavad õhutakistustegurit vastavalt 5% ja 7%. Teiseks hüpoteesiks oli, et lahtise kasti korral tekitab tagumine kinnine poord väga suuri keeriseid ning on õhuvoolu sujuvusel suur takistus. Vooluanalüüside tulemusete kohaselt parandab kinni kaetud kabaruum aerodünaamilist efektiivsust 10%. Kolmandaks hüpoteesiks oli, et hetkel Bestneti nomenklatuuris olev plastkaane kuju on võimalik aerodünaamilise efektiivsuse eesmärgil optimeerida. Optimeerimise käigus tehti kolm iteratsiooni, mille tulemuseks oli 17% parem õhutakistustegur. Neljandaks hüpoteesiks oli, et lühendades haagise tiisli pikkust väheneb autorongi õhutakistustegur, kuna alarõhutsoon haagise ja veduki vahel väheneb. Vooluanalüüsid kinnitasid ka seda hüpoteesi, sest lühendades tiislit 400mm võrra vähenes õhutakitsustegur 10% võrra. Lõputöös selgitati, miks on õhutakistusjõu vähendamine vajalik. Selgitati piirikihi mõju ja toodi võrdlusesse eri kujude õhutakistustegurid. Antud töös kirjeldati, mis on aerodünaamika ja selle alused. Selgitati nii turbulentse kui ka laminaarse voolamise olemust. Selgitati haagiste tüübikinnitamist. Samuti tuuakse välja CFD tarkvara kasutamise alustõed. Sellest lähtuvalt kirjeldati nii tuuletunneli kui ka võrgu (ing. mesh) vajalikkust. Praktilises osas loodi mudelid, mille alusel hakati kontrollima hüpoteeside tõele vastamist. Loodi mudelid, kus autorongi vedukiks oli ahmedi keha. Samuti loodi mudel tilgakujulisele haagisele. Seejärel tehti igale mudelile CFD analüüs. Vooluanalüüsi tulemused koondati kokku tabelitesse ning tehti nende põhjal hüpoteeside osas järeldusi. Arvutati, mis oleks sellise töö inseneri tunnihind, selgus et 80 eurot tunnis on väga õiglane hind. Lõpuks arvutati energia kulu eri haagiste lahenduste korral, selgus et reaalne võit eri lahenduste korral võib tähendada elektriauto korral kuni 35km suuremat ühe laadimisega läbitud vahemaad.

The aim of this thesis was to find the elements that affect the aerodynamic efficiency of a trailer. Simscale flow analysis software was used for this purpose. Therefore, no real-life experiments were performed during the graduation thesis, as it was necessary to find elements which makes sense to perform the experiments later. At the beginning of the work, the author set up 4 main hypotheses. The first hypothesis was that the smooth sides of the trailer and the covered bottom reduce the aerodynamic draf of the vechicle and trailer combination. The results of the flow analyzes confirmed that the smooth ports and smooth bottom improve the drag coefficient by 5% and 7%, respectively. The second hypothesis was that when the trailer box is open, the rear closed port causes very large vortices and is a major obstacle to the smooth flow of air. According to the results of the flow analyzes, the covered trailer box improves the aerodynamic efficiency by 10%. The third hypothesis was that the shape of the plastic cover currently in the Bestnet nomenclature could be optimized for aerodynamic efficiency. During the optimization, three iterations were performed, resulting in a 17% better drag coefficient. The fourth hypothesis was that shortening the drawbar length of the trailer reduces the air resistance of the vechicle and trailer combination as the negatiive air pressure zone between the trailer and the towing vehicle decreases. Flow analyzes also confirmed this hypothesis, as shortening the drawbar by 400 mm reduced the drag coefficient by 10%. The thesis explained why it is necessary to reduce the air resistance force. The effect of the boundary layer was explained and the air resistance factors of different shapes were compared. This work described what aerodynamics and its bases are. The nature of both turbulent and laminar flow was explained. The type approval of trailers was clarified. The basics of using CFD software are also outlined. Based on this, the need for both a wind tunnel and a mesh was described. In practical part of the thesis, models were created to test the validity of the hypotheses. Models were created in which the body of the car was Ahmed's body. A model for a teardrop-shaped trailer was also created. CFD analysis was then performed on each model. The results of the flow analysis were summarized in tables and conclusions were drawn based on them. The hourly rate of an engineer for such work was calculated, it turned out that 80 euros per hour is a very fair price. Finally, the energy consumption for the different trailer solutions was calculated, it turned out that a real gain with different solutions could mean a distance of up to 35km per charge in the case of an electric car. 33 The goals of the thesis were achieved, and the company was offered a solution in which the trailer has a covered cargo area, a smooth bottom, smooth panels and the shortest possible drawbar. Next, the company would need to design such a trailer, build a prototype, and then perform real-life tests.