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Abstract:
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The project is part of a cooperation between Hyuandai GmbH and Ecokat, Ecokat is a company dedicated to the construction of catalytic converters and particulate filters for diesel engines. The testing of Ecokat catalysts in Hyundai engines are done in the laboratory of the Hochschule Darmstadt, equipped with testing banks and measuring devices. Specifically, the subject of my project is to develop a system to cool the exhaust of a diesel engine with 80 kW of power. The reason for having to cool the exhaust gas is to check whether the temperature influences the performance of the catalyst and particulate filter, and the goal is to cool the exhaust gases 50 º C.
Above all I asked to choose within a liquid and a air cooling. As a cooling liquid required more pieces and more accurately due to the tightness I decided to do the calculations with cooling air.
The first step was to calculate the composition of exhaust gas to calculate their physical and chemical characteristics with the help of the data bank of tests. After calculating the internal and external convection of the system, raising it to two different designs, a single tube with cooling fins and the other three tubes with the same smooth and cooling fins. To simplify the calculations I made an Excel sheet to experiment with different diameters, thicknesses, materials, etc.. In the end I decided to design a single tube with squared fins, as the design of three tubes would have had masses of gas friction losses. The choice of squared fins was for costs reasons, since copper is sold in square plates, and it was easier to cut the square-shaped and weld them to the tube. The building plans are made with Catia v5, after I asked the cooper and then the workers of the workshop built the radiator at the University.
Once assembled, I did the tests, check results were not unexpected, since it not obtained the calculated cooling, especially at low rpm and low power. To promote the heat transfer coefficient I introduced a spring inside the tube, so the turbulence of the gases increased. After that I got good test results at low rpm and low power but at high power and at high rpm the results were worse than those calculated, probably because the spring had no effect.
In conclusion, I think the reason for the difference between the calculated values and there obtained on the testing bank are because the formula that I used is based on ideal cases and gives approximated values with poor accuracy. |
