The influence of the enrichment injection angle on the performance of a pre-chamber spark ignition natural-gas engine

The Turbulent Jet Ignition is an effective concept to achieve stable lean burning for natural gas engines due to the multiple ignition sources, high ignition energy, and fast combustion rate. A variation of the ignition location has a non-negligible effect on the ignition performance of the TJI system. The present work aims to provide more details on this effect by numerical simulations. Both factors of the additional fuel supply to the pre-chamber and the in-cylinder flow field are taken into consideration in this study. A numerical model is built based on a lean burning natural gas engine and validated by experimental results. Five different spark ignition sources are equally arranged on the vertical axis of the pre-chamber, with different distances from the connecting orifices. Simulations are carried out under the same initial and boundary conditions except for the location of the ignition source. Combustion pressure, in-cylinder flow field, fuel mass fraction distribution, and heat release rate are analyzed to study the in-cylinder ignition and combustion process. The results show that a rotational flow and a non-uniform fuel distribution are formed in the pre-chamber during the compression stroke. The turbulent jet characteristics are significantly influenced by the coupling of two factors: the combustion rate inside the pre-chamber as well as the flame propagation distance from the ignition source to the connecting orifices. Rapid combustion rate and shorter flame propagation distance both lead to the earlier ejection of cold jets and hot jets. Among five ignition sources, the one located closest to the connecting orifices generates earlier hot jets with the highest mean velocity. The jets are more effective to ignite the lean mixture and could decrease the combustion duration of the main chamber.

Section: Introductionmentioning

confidence: 99%

Effect of spark ignition location on the turbulent jet ignition characteristics in a lean burning natural gas engine

Xue

Yong

Zhao

et al. 2022

“…The enriching and scavenging timing affects the flow field, the fuel-air mixture concentration distribution and the heat release process in the pre-chamber. Feng et al 25 developed an optical model of a pre-chamber its size was twice the real and installed a high-pressure enrichment injector in the model. They investigated the flow fields induced by the enrichment injection in the pre-chamber model based on the two-dimensional particle image velocimetry measurements.…”

Section: Introductionmentioning

confidence: 99%

The scavenging timing of pre-chamber on the performance of a natural gas engine

Xue

Yong

Wang

2020

The pre-chamber ignition system scavenged with natural gas can effectively improve the in-cylinder combustion process and extend the lean-burn limit of natural gas engines. The scavenging process affects the flow field and fuel-air mixture concentration distribution in the pre-chamber and affects the combustion process in the pre-chamber as well as the ignition process in the main chamber. This has a significant influence on the performance of natural gas engines. It is supposed that the ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing affects the combustion process in the pre-chamber. To verify this suppose, an independent injection system for injecting natural gas into the pre-chamber is designed and experiments are carried out on a single-cylinder natural gas engine. The ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing is adjusted by changing the injection start angle of the scavenging process. The combustion process in the pre-chamber and the main chamber are analyzed using the in-cylinder pressures. The results indicate that, with the delay of the injection start angle, the ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing increases, the combustion process in the pre-chamber is enhanced, the maximum pressure difference between two chambers increases and appears earlier. The energy of the hot jets and the penetration of the jets increase, which enhances the combustion process in the main chamber.

“…They performed 2D particle image velocimetry (PIV) experiments to capture the flow field inside the prechamber. 8,9 To the best of the authors' knowledge, no other experiments with an optically accessible prechamber have been reported.…”

Section: Introductionmentioning

confidence: 99%

Numerical procedure for prechamber transfer from a single-cylinder engine to a rapid compression machine

Soni¹,

Posch²,

Gößnitzer³

et al. 2023

This paper presents a method for transferring a prechamber from a single-cylinder engine (SCE) to a rapid compression machine (RCM) as a pre-step for carrying out optical experiments. The overall objective of the transfer procedure is to achieve similar flow field conditions in the prechamber which is mounted on an RCM as compared to the same prechamber mounted on an SCE. Computational fluid dynamics (CFD) simulations of a large-bore natural gas SCE were carried out up to ignition timing which serve as the basis for the transfer procedure. The mass-flow rate in the prechamber neck, pressure difference between the main chamber and prechamber, prechamber pressure and mass in the prechamber were defined as the governing thermodynamic quantities which affect the evolution of the flow field in the prechamber during the compression stroke. All of these quantities in an RCM are largely influenced by operating piston speed and compression ratio for given initial conditions. The RCM operation parameters for each governing quantity were estimated with the help of 0D simulations. CFD simulations of RCM were performed for the determined RCM operation parameters, and the evolution of the velocity field and turbulent quantities in the prechamber were evaluated. The procedure has been applied to two prechambers of different shape and size and a good agreement between the RCM and corresponding SCE CFD simulations was achieved for the flow field conditions in both of the prechambers near the ignition timing. It was found that mass-flow rate in the prechamber neck is the most important quantity which influences the prechamber flow field. Overall this numerical procedure provided a flexible and computationally feasible approach to adjusting RCM operation parameters for transferring a prechamber from the SCE to RCM.