Effect of Cylinder-by-Cylinder Variation on Performance and Gaseous Emissions of a PFI Spark Ignition Engine: Experimental and 1D Numerical Study

Luigi Teodosio,Fabio Bozza,Cinzia Tornatore,Luca Marchitto,Gerardo Valentino

doi:10.3390/app11136035

Luigi Teodosio, Fabio Bozza + Show 3 more

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https://doi.org/10.3390/app11136035

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Abstract

Combustion stability, engine efficiency and emissions in a multi-cylinder spark-ignition internal combustion engines can be improved through the advanced control and optimization of individual cylinder operation. In this work, experimental and numerical analyses were carried out on a twin-cylinder turbocharged port fuel injection (PFI) spark-ignition engine to evaluate the influence of cylinder-by-cylinder variation on performance and pollutant emissions. In a first stage, experimental tests are performed on the engine at different speed/load points and exhaust gas recirculation (EGR) rates, covering operating conditions typical of Worldwide harmonized Light-duty vehicles Test Cycle (WLTC). Measurements highlighted relevant differences in combustion evolution between cylinders, mainly due to non-uniform effective in-cylinder air/fuel ratio. Experimental data are utilized to validate a one-dimensional (1D) engine model, enhanced with user-defined sub-models of turbulence, combustion, heat transfer and noxious emissions. The model shows a satisfactory accuracy in reproducing the combustion evolution in each cylinder and the temperature of exhaust gases at turbine inlet. The pollutant species (HC, CO and NOx) predicted by the model show a good agreement with the ones measured at engine exhaust. Furthermore, the impact of cylinder-by-cylinder variation on gaseous emissions is also satisfactorily reproduced. The novel contribution of present work mainly consists in the extended numerical/experimental analysis on the effects of cylinder-by-cylinder variation on performance and emissions of spark-ignition engines. The proposed numerical methodology represents a valuable tool to support the engine design and calibration, with the aim to improve both performance and emissions.

Highlights

Modern internal combustion engines (ICEs) are designed with the aim to reduce the pollutant and CO2 emissions, while delivering the required torque performance, complying with the binding legislations for vehicle homologation [1]
A greater interest is devoted to the emerging techniques to limit the in-cylinder production of pollutant emissions for spark ignition (SI) engines, such as the adoption of innovative combustion modes moving towards the Low-Temperature Combustion (LTC) concept: the homogeneous charge compression ignition (HCCI), the spark-assisted compression ignition (SACI) and the turbulent jet injection [2]
Cylinder-by-cylinder variations are apparent in Figure 2a which shows the experimental incylinder pressure trace and the rate of heat release (ROHR) for two representative operating points (3000@9 and 3000@13, 0% exhaust gas recirculation (EGR))

Summary

Introduction

Modern internal combustion engines (ICEs) are designed with the aim to reduce the pollutant and CO2 emissions, while delivering the required torque performance, complying with the binding legislations for vehicle homologation [1]. TWC device requires a close-to-stoichiometric air/fuel (A/F) mixture to guarantee a high efficiency, with significant performance losses at the engine cold start operations. To overcome this issue, a greater interest is devoted to the emerging techniques to limit the in-cylinder production of pollutant emissions for SI engines, such as the adoption of innovative combustion modes moving towards the Low-Temperature Combustion (LTC) concept: the homogeneous charge compression ignition (HCCI), the spark-assisted compression ignition (SACI) and the turbulent jet injection [2]. Turbulent jet injection (TJI) demonstrates to be a promising technique to reduce the exhaust emissions of SI engines [3], especially in the case of an active pre-chamber thanks to the ultra-lean combustion; on the other side, HCCI and SACI combustion modes allow significant improvements in NOx emissions, while some penalties on the HC and CO are obtained [4]

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