Mobility and Vehicle Mechanics

15-26

Authors: Dejanu Marcel, Dascalu Traian, Popa Dinel, Pârlac Sebastian, Salamu Gabriela

The experimental bench has in its composure a laser equipment, a high speed recording video equipment, a measuring system for recording pressure variations and a static enclosure in which experiments are conducted. The recording of images was done using the shadow graph technique, a source of light with xenon and a 3000 frames/s high speed camera with a resolution of 512x512 pixels. There were recorded and analyzed the next phenomenon: the variation of the flame front depending on the initial pressure, the variation of the pressure from inside the chamber depending on the initial pressure and also the shape and the way of how the flame front is propagated. The results are presented under the form of images and diagrams.

35-50

Authors: Adrian Clenci, Adrian Biziiac, Pierre Podevin, Rodica Niculescu

Reducing fuel consumption is a prime objective in the automotive industry in order to meet legal and customer demands due to the increasing price of oil. Variable valve actuation offers many opportunities for improving the spark ignition engine’s performance in areas such as fuel economy and pollutant emissions. This study presents a variable intake valve lift (ViVL) mechanism, used to enhance fuel economy in the area of idle operation and low part loads, which are the ones most frequently encountered in a vehicle’s operation time. Currently, this mechanism is self-regulated thanks to a hydro-mechanical system and allows a continuous intake valve lift variation during engine operation. Our studies revealed that the ability to control valve lift does indeed offer the ability to control intake air mass but also has the added benefit that it improves the fuel-air mixing process and controls air motion. This is particularly important at idle and low part loads when low lifts are to be used for improving the fuel economy or for achieving the required power. The paper focuses on the experimental results obtained when approaching idle operation with different configurations of the intake valve timing system. Results indicating the potential of the ViVL system for fuel economy improvement, as well as results regarding the in-cylinder pressure evolution are presented in this paper. Last but not least, the paper also presents a so-called Sleep&Start strategy, which can be seen as an alternative to the Stop&Start micro-hybridization solution. In other words, once a ViVL system has been installed on an engine, it should be used in every possible way in order to obtain a high benefits/cost ratio.