Abstract
KEYWORDS:
turbo charging, turbo-lag, response time, instant torque.
ABSTRACT:
The response of the engine in the transient working regimes influences the vehicle's behaviour in terms of dynamic and comfort performances but also in terms of toxic emissions. The study of the transient phenomenon of the automotive engines is very difficult due to the important variation of working regimes (load and speed of rotation). In order to perform a theoretical estimation of the dynamic performances during these transient regimes, mechanical, aerodynamic and thermal problems have to be solved, which are not quite easy at the actual level of knowledge. It is therefore, imperative to perform some experimental investigation during these regimes.
Nowadays, all Diesel engine powered vehicles are turbocharged. The main problem of these engines is related with the turbo-lag phenomenon. Thus, it is very important the analysing of the response time of the engine, which is subject to sudden acceleration.
For the study of the vehicle's behaviour there are widely spread the road tests and the roller bench. Obviously, both of them need the vehicle but if we want to focus our attention only on the thermal engine (e.g. on the turbocharger assembly), then we could use the classical engine test bench equipped with an inertia flywheel mounted between the engine and the brake. One advantage comes from the numerous measuring possibilities presented into a laboratory.
Thus, the authors will present in this paper some results concerning the response time analysis of a turbocharged diesel engine at a sudden acceleration from 30 km/h to 60 km/h into the 3rd gear. The experiments were performed by the authors on the Cnam's engine test bench, equipped with an inertia flywheel. Starting from analysing the speed evolution, information concerning instant torque will be found. On the time interval corresponding to the response time, there are distinguished three phases of the torque evolution. All these phases will be treated carefully in the paper.