Multi-Zone DI Diesel Spray Combustion Model for Thermodynamic Simulation of Engine with PCCI and High EGR Level

Abstract

A multi-zone, direct-injection (DI) diesel combustion model, the so-called RK-model, has been developed and implemented in a full cycle simulation of a turbocharged engine. The combustion model takes into account: • transient evolution of fuel sprays, • interaction of sprays with swirl and walls, • evolution of near-wall flow formed after spray-wall impingement depending on impingement angle and local swirl velocity, • interaction of Near-Wall Flows (NWF) formed by adjacent sprays, • influence of temperatures of gas and walls in the zones on evaporation rate. In the model the fuel spray is split into a number of specific zones with different evaporation conditions including zone on the cylinder liner and on the cylinder head. The piston bowl is assumed to be a body of revolution with arbitrary shape. The combustion model supports central and non-central injector as well as the side injection system. NOx formation model uses Detail Kinetic Mechanism (199 reactions with 33 species). Soot formation model is phenomenological. The general equation for prediction of ignition delay period was derived as for conventional engines as for engines with PCCI where pilot injection timing achieved 130 CA deg. before TDC. The model has been validated by experimental data obtained from high-speed, mediumspeed and low-speed engines over the whole operating range; a good agreement has been achieved without recalibration of the model for different operating modes. General equations for prediction of spray tip penetration, spray angle and ignition delay for low temperature combustion and high temperature combustion were derived and validated with the published data obtained for different diesels including diesels with multiple injection system and injection timing varied from very early up to after the TDC. To make a computational optimization of multiple injection strategy possible, the full cycle thermodynamic engine simulation software DIESEL-RK has been supplied with library of nonlinear optimization procedures.

Investigating Diesel Engine Performance and Emissions Using CFD

“…Comparison of results demonstrates a good agreement between theoretical and experimental sets of data [3].…”

“…A multi-zone direct-injection (DI) diesel combustion model has been implemented for full cycle simulation of a turbocharged diesel engine [3]. The above combustion model takes into account the following features of the spray dynamics:  the detailed evolution process of fuel sprays;  interaction of sprays with the in-cylinder swirl and the walls of the combustion chamber;  the evolution of a Near-Wall Flow (NWF) formed as a result of a spray-wall impingement as a function of the impingement angle and the local swirl velocity;  interaction of Near-Wall Flows formed by adjacent sprays;  the effect of gas and wall temperatures on the evapo-ration rate in the spray and NWF zones.…”

A numerical study on the performance, combustion and emission parameters of a compression ignition engine fuelled with diesel, palm stearin biodiesel and alcohol blends

“…The physical and chemical features of those four phases are different but each has an effect on the heat release rate. The ignition delay period is the first phase of the heat release and it is calculated using modified Tolstov's equation (Kuleshov 2009) as follows:…”

Self-Ignition Delay Prediction in PCCI Direct Injection Diesel Engines Using Multi-Zone Spray Combustion Model and Detailed Chemistry

“…A more detailed description of the RK-model is presented in [1,2,3,35,53]. The present paper describes additional features of the RK-model developed and integrated into the model with a purpose to improve the accuracy of the heat release prediction in diesels with PCCI process.…”

“…The free spray contours obtained by different ways: a) calculated by Reitz and Bracco using KIVA[33]; b) measured by Dan[34]; c) calculated by Jung and Assanis[35] using Hiroyasu and Arai equations[36]; d) calculated using Equations 17 and 18.…”