Experimental and simulation analysis of the transient operation of a turbocharged multi-cylinder IDI diesel engine

Abstract

SUMMARYAn experimental and theoretical analysis is carried out to study the response of a multi-cylinder, turbocharged, IDI (indirect injection) compression ignition engine, under transient operating conditions. To this aim, a comprehensive digital computer model is developed which solves the governing differential equations individually for each cylinder, providing thus increased accuracy over previous 'single-cylinder' simulations. Special attention has been paid for diversifying the transient operation from the steady-state one, providing improved or even new relations concerning combustion, heat transfer to the cylinder walls, friction, turbocharger and aftercooler operation, and dynamic analysis for the transient case. An extended steady state and transient experimental work is conducted on a specially developed engine test bed configuration, located at the authors' laboratory, which is connected to a high-speed data acquisition and processing system. The steady-state measurements are used for the calibration of the individual submodel constants. The transient investigation includes both speed and load changes operating schedules. During each transient test four major measurements are continuously made, i.e. engine speed, fuel pump rack position, main chamber pressure and turbocharger compressor boost pressure. The hydraulic brake coupled to the engine possesses a high mass moment of inertia and long nonlinear load-change times, which together with the indirect injection nature of the engine are important challenges for the simulation code. Explicit multiple diagrams are given to describe the engine and turbocharger transient behaviour including smoke predictions. The agreement between experimental and predicted responses is satisfactory, for all the cases examined, proving the validity of the simulation process, while providing useful information for the engine response under various transient operations.

The Effect of Various Dynamic, Thermodynamic and Design Parameters on the Performance of a Turbocharged Diesel Engine Operating under Transient Load Conditions

“…Engine dynamics -If G tot represents the total system moment of inertia (engine, flywheel and load), then the conservation of energy principle applied to the total system (engine plus load) yields [20,3,[16][17][18]:…”

“…Polynomial expressions from Ref. [19] are used for each of the four species (O 2 , N 2 , CO 2 , and H 2 O) considered, concerning the evaluation of internal energy and specific heat capacities for first-law application to the engine cylinder contents [16][17][18][19][20][21][22][23].…”

“…Friction modelling -For the calculation of friction inside the cylinder the method proposed by Rezeka and Henein [27,18,28] is adopted, which describes the non-steady profile of friction torque during each cycle. In this method the total amount of friction is divided into six parts; three of these parts are concerned with the cylinder movement, as follows:…”

“…To this aim, improved relations concerning (indirect) fuel injection, combustion, dynamic analysis, heat transfer to the cylinder walls, friction modelling, and turbocharger and aftercooler operation during the transient response have been developed, which contribute to a more indepth modelling [16][17][18]. Moreover, a multi-cylinder engine model is incorporated, i.e.…”

“…A high-speed data acquisition system was set up for measuring engine and turbocharger variables performance under both steady-state and transient operation. An extended series of experiments was conducted, with engine operations covering both speed and load changes operating schedules [18]. The engine in hand possesses a high moment of inertia which leads to slow recovery with small speed droop (difference between initial and final engine speed) and extremely low soot emissions under any load-change.…”