Autoignition and Emission Characteristics of Gaseous Fuel Direct Injection Compression Ignition Combustion

Abstract

Heavy-duty natural gas engines offer air pollution and energy diversity benefits. However, current homogeneous-charge lean-burn engines suffer from impaired efficiency and high unburned fuel emissions. Natural gas direct-injection engines offer the potential of diesel-like efficiencies, but require further research. To improve understanding of the autoignition and emission characteristics of natural gas direct-injection compressionignition combustion, the effects of key operating parameters (including injection pressure, injection duration, and pre-combustion temperature) and gaseous fuel composition (including the effects of ethane, hydrogen and nitrogen addition) were studied. An experimental investigation was carried out on a shock tube facility. Ignition delay, ignition kernel location, and NOx emissions were measured. The results indicated that the addition of ethane to the fuel resulted in a decrease in ignition delay and a significant increase in NOx emissions. The addition of hydrogen to the fuel resulted in a decrease in ignition delay and a significant decrease in NOx emissions. Diluting the fuel with nitrogen resulted in an increase in ignition delay and a significant decrease in NOx emissions.

Effects of Hydrogen Addition on High-Pressure Nonpremixed Natural Gas Combustion

“…This triggering arrangement ensures that the first introduction of fuel into the shock tube (Start of Fuelling, SOF) occurs shortly after constant pressure and temperature conditions have been established in the experimental section. Earlier injector characterization tests, detailed in Wu (2007), found the mean injection delay of the fuel injector to be 0.311 ms with a standard error of approximately 400…”

“…The design and operation of the shock tube used in this work has been described previously (Huang et al 2004Sullivan et al 2006;Wu et al 2007). The stainless steel shock tube is 7.90 m long (3.11 m driver section and 4.79 m driven section) with an inside diameter of 5.9 cm.…”

Parametric Study of Autoigniting Hydrogen–Methane Jets in Direct-Injection Engine Conditions

“…In diesel-engine-like conditions, there are very few direct-injection experimental studies of the ignition and flame structure of H 2 –natural gas blends. Perhaps the most comprehensive among the available data sets is the measurements of Wu et al , that characterized the H 2 and methane (CH 4 ) blends (20 vol % H 2 ) that were directly injected into a shock tube via a 0.275 mm single-hole nozzle. Their studies, which investigated the injection of the H 2 -blended mixture at varied injection pressures (6–15 MPa) and durations (1.5–2.5 ms) into a compressed charge at a fixed ambient pressure of 3 MPa but with varied temperature conditions (1200–1400 K), reported a decreasing trend of ignition delay with increasing the ambient temperature and injection pressure.…”