Effects of indirect water injection in turbocharged internal combustion engines with spark ignition and direct fuel injection

This study focuses on the analysis of a proposal for a solution of one of the problems presented by internal combustion engines: the high temperature inside the combustion chamber. The proposal was defined as water injection in the intake manifold (one injection valve per cylinder) of a 4-stroke, 4-cylinder engine arranged in line with direct fuel injection (Otto cycle), with 1592 cm³ of total volume, equipped with turbocharger and air to air intercooler – which allows the reduction of this temperature and prevents negative effects. After the analysis of previously published studies on the subject, respecting the singularities and respective parameters of each one, the 30 K temperature reduction inside the combustion chamber was determined as the target of this study. Simulations of the system operation were carried out aided by AVL Boost software, considering the injection of 12.5% of distilled water with the engine running at full load. The results of the simulation indicated an average temperature decrease of 25.51 K, in addition to the reduction in the emission of NO_X and CO₂, but there was an increase in CO emission. Also, a gain in power and torque was observed in the present study when compared to results obtained in the simulation of an engine running without water injection, using the same software.