Lean Methane Mixtures in Turbulent Jet Ignition Combustion System

Abstract

The development of modern vehicle drives is aimed at reducing fuel consumption (i.e., crude oil) and minimizing the exhaust emission of toxic components. One such development is the implementation of a two-stage combustion system. Such a system initiates ignition in the prechamber, and then the burning mixture flows into the main chamber, where it ignites the lean mixture. The system allows the efficient combustion of lean mixtures, both liquid and gaseous fuels, in the cylinder. This article proposes a solution for internal combustion engines with a cylinder capacity of approx. 500 cm3. The tests were carried out on a single-cylinder engine powered by pure methane supplied through a double, parallel injection system. A wide range of charge ignitability requires the use of an active chamber containing an injector and a spark plug. The tests were carried out at n = 1500 rpm with three load values (indicated mean effective pressure, IMEP): 2, 4 and 6 bar. All of these tests were carried out at a constant value of the center of combustion (CoC), 8 deg CA. This approach resulted in the ignition timing being the control signal for the CoC. As a result of the conducted research, it was found that an increase in the load, which improved the inter-chamber flow, allowed for the combustion of leaner mixtures without increasing the coefficient of variation, CoV(IMEP). The tests achieved a lean mixture combustion with a value of λ = 1.7 and an acceptable level of non-uniformity of the engine operation, CoV(IMEP) < 8%. The engine’s indicated efficiency when using a two-stage system reached a value of about 42% at λ = 1.5 (which is about 8 percentage points more than with a conventional combustion system at λ = 1.0).