Search Results

Low temperature combustion (LTC) of diesel fuel offers a path to low engine emissions of nitrogen oxides (NOx) and particulate matter (PM), especially at low loads. Borescopic optical imaging offers insight into key aspects of the combustion process without significantly disrupting the engine geometry. To assess LTC combustion, two-colour pyrometry can be used to quantify local temperatures and soot concentrations (KL factor). High sensitivity photo-multiplier tubes (PMTs) can resolve natural luminosity down to low temperatures with adequate signal-to-noise ratios. In this work the authors present the calibration and implementation of a borescope-based system for evaluating low luminosity LTC using spatially resolved visible flame imaging and high-sensitivity PMT data to quantify the luminous-area average temperature and soot concentration for temperatures from 1350-2600 K.

An experimental investigation of the autoignition and emission characteristics of transient turbulent gaseous fuel jets in heated and compressed air was conducted in a shock tube facility. Experiments were performed at an initial pressure of 30 bar with initial oxidizer temperatures ranging from 1200 to 1400 K, injection pressures ranging from 60 to 150 bar, and injection durations ranging from 1.0 to 2.5 ms. Methane and 90.0% methane/10.0% ethane blend were used as fuel. Under the operating conditions studied, increasing temperature resulted in a significant decrease in autoignition delay time. Increasing the injection pressure decreased ignition delay as well. The downstream location of the ignition kernel relative to the jet penetration distance was found to be in the range, 0.4

The effects of impinging airflow on the near nozzle characteristics of an inwardly opening, high pressure-swirl atomiser are investigated in an optically-accessed, steady-state flow rig designed to emulate the intake flow of a typical, side-injected, 4-valve gasoline direct-injection combustion system. The results indicate that the impinging airflow has a relatively minor effect on the initial break-up of the fuel spray. However, the secondary break-up of the spray, i.e. the break-up of liquid ligaments, the spatial distribution of droplets within the spray and the location of the spray within the cylinder are significantly affected by the impinging air.