Development and validation of a novel quasi-dimensional combustion model for un-scavenged prechamber gas engines with numerical simulations and engine experiments

Abstract

Lean-burn gas engines equipped with an un-scavenged prechamber have proven to reduce nitrogen oxides (NOx) emissions and fuel consumption, while mitigating combustion cycle-to-cycle fluctuations and unburned hydrocarbon (UHC) emissions. However, the performance of a prechamber gas engine is largely dependent on the prechamber design, which has to be optimised for the particular main chamber geometry and the foreseen engine operating conditions. Optimisation of such complex engine components relies partly on computationally efficient simulation tools, such as quasi and zero-dimensional models, since extensive experimental investigations can be costly and time-consuming. This article presents a newly developed quasi-dimensional (Q-D) combustion model for un-scavenged prechamber gas engines, which is motivated by the need for reliable low order models to optimise the principle design parameters of the prechamber. Our fundamental aim is to enhance the predictability and robustness of the proposed model with the inclusion of the following: (i) Formal derivation of the combustion and flow submodels via reduction of the corresponding three-dimensional models. (ii) Individual validation of the various submodels. (iii) Combined use of numerical simulations and experiments for the model validation. The resulting model shows very good agreement with the numerical simulations and the experiments from two different engines with various prechamber geometries using a set of fixed calibration parameters.

Investigations on spark pre-chamber ignition and subsequent turbulent jet main chamber ignition in a novel optically accessible test rig

“…Turbulent jet ignition has been studied experimentally in different test rigs such as constant volume combustion chamber, 7,16–18 rapid compression (expansion) machines 19–23 and internal combustion engines, 3,5,24–26 in order to understand the effect of the boundary conditions on the mixing and ignition of a turbulent hot jet. Although, most of those studies have used un-scavenged or passive pre-chambers, 7,16–22,27–33 meaning that the equivalence ratio is the same in the pre- and main chamber; some studies have explored scavenged or active pre-chambers, 14,16,19,27,29,30,34–38 in which the equivalence ratio in the pre-chamber is stoichiometric or richer than in the main chamber. Moreover, 2D DNS simulations have studied the processes taking place inside the pre-chamber and the transition into the main chamber.…”

Jet ignition prediction in a zero-dimensional pre-chamber engine model

“…Engine performance models have been used for a long time in all types of engines, including pre-chamber engines. 12–18 However, as yet, no model includes submodels to take into account the thermal effects in the ducts connecting pre- and main chambers, nor to predict the result of the main chamber jet ignition attempts. They assume an automatic ignition of the main chamber and some of them even impose a combustion law like the well-known Wiebe law.…”

“…Engine performance models have been used for a long time in all types of engines, including pre-chamber engines. [12][13][14][15][16][17][18] However, as yet, no model includes submodels to take into account the thermal effects in the ducts connecting pre-and main chambers, nor to predict the result of the main chamber jet ignition attempts. They assume an automatic ignition of the main chamber and some of them even impose a combustion law like the well-known Wiebe law.…”

“…Figure18. Pressure inside pre-and main chambers for multiple equivalence ratios of intake premixed mixture in, dd = mm.…”

Modelling combustion in spark ignition engines with special emphasis on near wall flame quenching

“…In addition, quenching of laminar and turbulent flames in various other configurations have been studies in. 10–18…”