Premixed-Diffusive Multizone Model for Combustion Diagnostics in Conventional and PCCI Diesel Engines

Abstract

A new multizone premixed-diffusive combustion model has been developed, assessed, and applied to diagnose the burning process and emission formation in a conventional and in a premixed charge compression ignition (PCCI) diesel engine. The model is based on the Dec conceptual scheme, which considers combustion as a two-stage quasi-steady process: All fuel particles undergo a first rich premixed combustion phase, and the products complete their oxidation in close-to-stoichiometric conditions at the jet periphery through a diffusion flame. The combustion chamber contents have been divided into several homogeneous zones to which the energy and mass conserx'ation principles were applied. The computed thermodynamic and thermochemical properties in the burned gas zones allowed a post-processing analysis to be made of the nitric oxides (NO), particulate matter (PM), and carbon monoxide (CO) formation. The model requires the in-cylinder pressure trace and other experimental engine quantities as input data and calculates the premixed and diffusive heat release rates along with the temperature and mass evolutions of the different zones. Thus, the model is not predictive but diagnostic: The objective is to interpret measured engine data in order to obtain insight into the in-chamber combustion and pollutant formation processes. The model has been tested on EGR-sweeps and under full-load conditions on the conventional engine and under a high FGR operating condition on the PCCI engine. With reference to NO emissions, the model results showed an excellent agreement with the experimental data for all the tests even when the main model parameters were kept constant for different test conditions. Good results were also obtained for the prediction of the CO and PM emission levels. Finally, for the premixed combustion zone, it was ascertained that higher local A/F ratios were required in the PCCI combustion mode than in the conventional mode as a consequence of the increase in the degree of premixing.

Diesel Injector Coking: Optical-Chemical Analysis of Deposits and Influence on Injected Flow-Rate, Fuel Spray and Engine Performance

“…15(a) delay, which occurs at higher bmep (case of Fig. 16(a)), is a consequence of the increase in in-cylinder temperature and pressure levels [42] as well as of the reduction in EGR, and it leads to a shorter air-fuel mixing time. This leads to a richer premixed combustion and thus to increased soot compared to the bmep = 5 bar case ( Fig.…”

“…18 have been obtained with a diagnostic tool and refer to n = 2500 rpm and bmep = 8 bar. Combustion diagnostics was carried out by means of a previously developed multizone model [42], which is based on the analysis ofthe in-cylinder measured pressure. The peak of the heat release rate (HRR) at low cratik angle (CA) in Fig.…”

Caracterización de la tasa de liberación de calor en los cilindros de un motor de generación a gas natural de 2 MW.

“…De este tipo de trabajos se destacan los aportes de O. A. Vergel et al [27], M. Lapuerta et al [28], P. Schihl et al [29], C. Rakopoulos et al [30], J. Ghojel et al [31], F. Payri et al [32], y M. Baratta et al [33]. Sin embargo, en este trabajo se opta por el tipo de modelo de valor medio en motores (MVEM), este genera excelentes resultados en la simulación sin presentar una gran complejidad en las ecuaciones que describen el proceso [34].…”

Instantaneous in-Cylinder Volume Considering Deformation and Clearance due to Lubricating Film in Reciprocating Internal Combustion Engines

“…Internal combustion engines have been studied since their creation and because of their vast number of applications, it is indispensable to have a better understanding of the processes occurring in these machines [1,2]. Currently, for combustion analysis, there are computational approaches, such as predictive models [3][4][5][6][7][8] and diagnostic models [9][10][11][12][13], in which the in-cylinder pressure signal is taken, and through the first law of thermodynamics, the rate of heat release is determined.…”