Diagnostics of Mixing Process Dynamics, Combustion and Emissions in a Euro V Diesel Engine Politecnico di Torino

Format:

Conference/Event

Author/Creator:

Catania, Catania, author.

Contributor:

Finesso, Roberto

Spessa, Ezio

Conference Name:

10th International Conference on Engines & Vehicles (2011-09-11 : Naples, Italy)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2011

Summary:

An innovative approach to the study of combustion and emissionformation in modern diesel engines has been applied to a EURO Vdiesel engine equipped with an indirect-acting piezo injectionsystem.The model is based on the joint use of a predictivenon-stationary 1D spray model, which has recently been presented byMusculus and Kattke, and a diagnostic multizone thermodynamic modeldeveloped by the authors.The combustion chamber content has been split into homogeneouszones, to which mass and energy conservation laws have beenapplied: an unburned gas zone, made up of air, EGR and residualgas, several fuel/unburned gas mixture zones, premixed combustionburned gas zones and diffusive combustion burned gas zones. The 1Dspray model enables the mixing process dynamics of the differentfuel parcels with the unburned gas to be estimated for eachinjection pulse; therefore, the equivalent ratio time-history ofeach mixture zone can be estimated. A separate set of zones hasconsequently been generated for each pulse, according to a similarconceptual approach to that introduced by Dec.A premixed burned gas zone is generated as combustion takesplace. This zone progressively oxidizes the mixture zones of thepulse, until they are completely consumed. If the averageequivalence ratio of the premixed burned gas zone is higher thanunity, diffusive burned gas zones are generated to completecombustion.The global heat release rate is calculated on the basis of theexperimental pressure signal, as the approach is of the diagnostictype. The main model results are the mass and temperatureevolutions of the zones, along with the equivalence ratio values ofthe different mixture zones at the start of combustion. In theliterature, this value has been shown to be significantly relatedto the soot formation rate.The diagnostic tool includes predictive submodels for thecalculation of the pollutant emissions. In other words, NOformation is modeled by means of thermal Zeldovich and promptmechanisms; CO is calculated via the Bowman equations; sootformation is modeled by means of an expression that is derived fromKitamura and others's, results, in which an explicit dependence onthe local equivalence ratio at the start of combustion isconsidered; soot oxidation is modeled via theNagle-Strickland-Constable formulation; the THCs are calculated byaccounting for the effects of spray overmixing, injector sac andhole volumes, and spray impingement.The model outcomes can be reported in the well-known φ-Tdiagrams, which offer a synthetic representation of the localconditions during the fuel/unburned gas mixing processes and duringcombustion for each single injection pulse.The diagnostic approach has been applied to a EURO V dieselengine equipped with indirect-acting piezo injectors, at bothmedium-low and medium-high load/speed conditions. The effects ofEGR rate variations have been also investigated in order to assessthe capability of the model to take the changes in the chargechemical composition into account. The main results have shown thatthe combustion of the pilot injection mainly occurs atstoichiometric/lean premixed conditions, as it is responsible forNOx but not for soot formation. The main injectioncombustion initially occurs in rich premixed conditions, a resultthat confirms the Dec conceptual model. No spray impingementoccurred in the analyzed data as far as THC formation is concerned,and the main contribution to THC emissions at the engine exhaustwas due to the injector sac and hole volumes. However, thecontribution of spray overmixing increased at medium-low loads.Finally, it has been confirmed that EGR is not an effectivemeans of decreasing the average φ value at the start of combustionto reduce soot formation

Notes:

Vendor supplied data

Publisher Number:

2011-24-0018

Access Restriction:

Restricted for use by site license