Combining in-cylinder pressure and 1D simulation tools to understand the combustion characteristics of natural gas in pre-chamber ignition systems for energy generation

Abstract

Recent outlooks suggest a long-term relevance of internal combustion engines for both power generation and transportation. Nonetheless, stringent pollutant reduction requirements combined with new CO2 mandates draws a challenging scenario, requiring intensive research and development activities to develop and optimize combustion modes to fulfill these requirements. Among the recent advancements, the active pre-chamber ignition system has been considered as a potential alternative to achieve a highly efficient and clean combustion process. Its combustion development is dictated by the pre-chamber ignition system which will provides a high energy flow jet inside the main chamber to enable a multi-site oxidation of the global lean mixture. The comprehension and quantification of the flow and combustion characteristics of the pre-chamber are of utmost importance to optimize the engine operation and pre-chamber design. Nonetheless, restrictive space for instrumentation at experimental side requires alternative numerical methods to aid the quantification of the state parameters and combustion process of these systems. In this sense, this research proposes a novel methodology combining in-cylinder pressure measurement and 1-D simulations as a tool to determine the state, flow and combustion development of different active pre-chambers operating with natural gas in a heavy-duty engine for power generation. The methodology is developed considering 3 different pre-chamber geometries, operating at different spark timings and equivalence ratios. The results suggest that the methodology is able to quantify the state conditions prior to the spark discharge as well as the evolution of the combustion process by means of considering the perturbations of the mass flow from the pre-chamber inside the main chamber energy balance. Moreover, the methodology allowed to quantify variations of equivalence ratio as small as 0.1 and combustion durations variations of 1 CAD.