Combustion Chambers for Natural Gas SI Engines Part 2: Combustion and Emissions

Abstract

The objective of this paper is to investigate how the combustion chamber design will influence combustion parameters and emissions in a natural gas SI engine.Ten different geometries were tried on a converted Volvo TD102 engine. For the different combustion chambers emissions and the pressure in the cylinder have been measured. The pressure in the cylinder was then used in a one-zone heat-release model to get different combustion parameters. The engine was operated unthrottled at 1200 rpm with different values of air/fuel ratio and EGR. The air/fuel ratio was varied from stoichiometric to lean limit. EGR values from 0 to 30% at stoichiometric air/fuel ratio were used.The results show a remarkably large difference in the rate of combustion between the chambers. The cycle-to-cycle variations are fairly independent of combustion chamber design as long as there is some squish area and the air and the natural gas are well mixed.Geometries that give the fastest combustion give the highest NO x values at λ=1.2, but at λ>1.5, which is normally designated lean-burn, the differences are smaller. The lowest NO x values for lean burn were obtained with the geometries that gives fast combustion.The HC emissions display some correlation between high combustion rate and low levels of HC emissions, but combustion chambers with dead zones and large total combustion chamber areas give higher HC contents than the combustion rate alone would indicate.Indicated efficiency is reduced for combustion chambers with a large total combustion chamber surface area and thus large heat losses. High levels of turbulence also tend to reduce the efficiency for the same reason.

Combustion Diagnostics by Means of Multizone Heat Release Analysis and NO Calculation

“…These data are published in [11] where details of the test engine and test conditions are also given.…”

Investigation of the Effects of Piston Geometry and Combustion Process Parameters on Engine Performance of Methane Fuelled Compression Ignition Engines with Kriging Method

“…Metan yakıtlı sıkıştırmalı ateşlemeli motorlarda piston geometrisinin performansa etkileriyle ilgili bazı çalışmalarda; piston çanağının dar olan geometrilerinde, çanak içinde daha iyi dağılımlı gaz karışımının oluşması motor performansını iyileştirdiği vurgulanmıştır [12,13,14]. Ayrıca, bu çalışmalarda dar çanak geometrilerde metan hava karışımlarında zengin, daha geniş çanak geometrilerinde ise fakir karışım oluştuğu sonucuna ulaşılmıştır.…”

Hybrid and Conventional Hydrogen Engine Vehicles that Meet EZEV Emissions

“…The combustion chamber is a simple right circular cylinder with no squish and a flat top piston. This geometry has been shown to be the most efficient shape for reducing heat transfer losses in lean-burn engines [11]. Engine characteristics are listed in Table 1, along with the range of conditions used in the experiment.…”