Numerical investigation of lambda-value prechamber ignition in heavy duty natural gas engine

Turbulent Jet Ignition systems are mainly dedicated to the combustion of lean mixtures of natural gas in heavy duty engines. The use of such a system in combination with lean mixtures leads to an increase in its overall efficiency. The article presents simulation analyzes of the impact of the excess air coefficient occurring in prechamber on the combustion process: combustion indicators and emission indicators. Tests on a single-cylinder engine with a displacement of about 4 dm3 at medium mixture (IMEP = 1.0 MPa) were carried out using the AVL Fire software. It was found that the incineration of global lean mixtures (lambda = 2) is effective when initiating this process (in the prechamber) with a charge of a stoichiometric composition. A strong relationship was found between the thermodynamic indicators in both prechamber and main chamber and the excess air coefficient initiating combustion.

Numerical Modelling of Swirl-Stabilized Turbulent Lean Non-Premixed Flames

Numerical simulations have been performed to analyze the interaction of confined coaxial high-swirl jets in both cases: isothermal and reactive flows. Besides different setups of swirl injectors have been tested to study the influence of swirl in the flames for both stoichiometric and lean mixtures. The aim was to quantify the nitrogen oxide emissions as well as the flow pattern for different swirling annular air jet and non-swirling inner fuel jet. This simple setup is widely used in burners to promote stabilized flames of lean mixtures producing ultra low NOx emissions.

Quantification of Efficiency Gains for Dilute IC Engines due to Increases of the Ratio of Specific Heats

Recent engine developments have demonstrated significant thermal efficiency gains for IC engines employing lean mixtures and high levels of exhaust gas recirculation (EGR). These efficiency gains have often been attributed to reduced heat losses and increases of the ratio of specific heats. No previous publication, however, has provided the quantitative contributions from these two items. This lack of information, therefore, motivated the current work. An automotive engine was selected for this study, and a thermodynamic engine cycle simulation was used for the evaluation. Engine conditions included a range of loads and speeds. For each engine condition, three cases were considered. These cases varied the equivalence ratio from stoichiometric to 0.7, and varied the EGR from zero to 45%. Depending on the engine conditions, the net indicated thermal efficiency increased between 4.2% and 8.9% (absolute) for the engine with the lean mixture (ϕ = 0.7) and EGR (45%). The lower gas temperatures and lean mixtures resulted in reduced heat losses and increases of the ratio of specific heats. For all conditions examined, the majority of the thermal efficiency gains were due to the increases of the ratio of specific heats. The contributions from the increases of the ratio of specific heats toward the efficiency gains ranged between about 46% and 82% for the conditions examined. The rest of the gains were from the reduced heat losses.

Design of System Hydrogen Engine Supercharging

In this paper I am dealing with a general analysis of problems burning of lean hydrogen mixtures in combustion engines. During burning of very lean mixtures burning procedure is over lasted with characteristic features. They need to be removed or reduced. One of these features is low power of engines operating by lean mixtures, which can be partially removed with the help of supercharging such engines. In the second part of the paper I am dealing with a design of supercharging system for a three-cylinder engine with volume 1,2 dm3.