JP Journal of Heat and Mass Transfer
Volume 12, Issue 2, Pages 197 - 210
(November 2015) http://dx.doi.org/10.17654/JPHMTNov2015_197_210 |
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FUEL CONSUMPTION REDUCTION AND POWER DOWNSIZE VIA ROBOTIZED MULTIPLE SPEED GEARBOX AND AUTOMATIC SELECTION SYSTEM FOR AN AUTOMOTIVE APPLICATION
Luca Piancastelli and Leonardo Frizziero
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Abstract: Multiple-speed gearboxes with computer controlled automatic gear selection devices are a common possible choice in cars. Robotized gear insertion of one tenth of a second is possible. Economical and weight consideration are to be made to verify if it is convenient to use a smaller engine and a larger gearbox with a wider choice of speeds. In this paper, an automotive application for a public transport vehicle based on a Class S chassis with the choice of common-rail direct injection engines. This choice is particular unfavorable for the multi-speed gearbox since common-rail engines have very flat specific fuel consumption curves. The lumped mass model implemented is conceived to estimate velocity, acceleration and fuel consumption starting from aerodynamic, inertia and thermodynamic data of the vehicle. The estimated data of performance and fuel consumption were compared with measured values. A Genetic elitarian Algorithm (GA) was used to optimise the engine choice and the gearbox speeds distribution. A maximum reduction of 15% was then calculated with a 16-speeds gearbox and a 140HP/300Nm engine in comparison with the standard 5-speeds 204HP/500Nm engine. This fuel reduction was obtained on the mixed city-motorway cycle. In this case, maximum speed is limited to 180km/h and the 0-100km/h acceleration is reduced to 11s (from the original 8.6s). The weight remains almost unaltered since the 204HP engine is heavier than the 140HP and this largely compensates the gearbox weight increase. The multiple speed solution seems to be very interesting also for public transports vehicles and for trucks. |
Keywords and phrases: multiple-speed gearbox, automotive, automatic selection system. |
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