Search Results

In this work, a promising technique, consisting of a liquid Water Injection (WI) at the intake ports, is investigated to overcome over-fueling and delayed combustions typical of downsized boosted engines, operating at high loads. In a first stage, experimental tests are carried out in a spark-ignition twin-cylinder turbocharged engine at a fixed rotational speed and medium-high loads. In particular, a spark timing and a water-to-fuel ratio sweep are both specified, to analyze the WI capability in increasing the knock-limited spark advance. In a second stage, the considered engine is schematized in a 1D framework. The model, developed in the GT-Power™ environment, includes user defined procedures for the description of combustion and knock phenomena. Computed results are compared with collected data for all the considered operating conditions, in terms of average performance parameters, in-cylinder pressure cycles, burn rate profiles, and knock propensity, as well.

Increasingly stringent pollutant and CO2 emission standards require the car manufacturers to investigate innovative solutions to further improve the fuel economy of their fleets. Among these techniques, an extremely lean combustion has a large potential to simultaneously reduce the NOx raw emissions and the fuel consumption of spark-ignition engines. Application of pre-chamber ignition systems is a promising solution to realize a favorable air/fuel mixture ignitability and an adequate combustion speed, even with very lean mixtures. In this work, the combustion characteristics of an active pre-chamber system are experimentally investigated using a single-cylinder research engine. Conventional gasoline fuel is injected into the main chamber, while the pre-chamber is fed with compressed natural gas. In a first stage, an experimental campaign was carried out at various speeds, spark timings and air-fuel ratios.