Numerical Investigation on the Effect of Cylindrical Combustion Chamber Diameter-to-Depth Ratio on the Performance of Stoichiometric Natural Gas Engine With Exhaust Gas Recirculation

Abstract

In this study, three cylindrical combustion chambers with different diameter-to-depth ratios were designed to accelerate the flame propagation and enhance the combustion ratio of CH4 in a stoichiometric natural gas engine with EGR. The effects of the diameter-to-depth ratio on the combustion and emission and the interaction between the flow field distribution and flame propagation were investigated numerically. The results showed that the value of the swirl ratio and turbulent kinetic energy (TKE) near the TDC could be increased continuously with a smaller diameter-to-depth ratio, which was conducive to promoting the uniform flame spread in the radial direction and enhanced the combustion efficiency. The peaks of pressure, heat release rate and temperature dramatically increased by using the cylindrical chamber with a higher swirl ratio and higher TKE in the stoichiometric natural gas engines, thereby allowing more fuel energy to be released near the TDC in the chamber. The cylindrical chamber with the diameter-to-depth ratio of 2.36 displayed a higher peak value of combustion pressure and temperature, smaller CH4 and CO emissions, but more NOx emission, compared to other chambers. Moreover, the raised bottom bulge of the piston distorted the flame front, which accelerated the flame speed in the vertical direction. The CA50 was therefore advanced to the TDC. Thus, the cylindrical chamber with the increased squish area and the raised bottom bulge was conducive for the stoichiometric natural gas engine with EGR.

Effect of acetylene as a low reactivity fuel on performance, combustion, exergy and emissions of an acetylene/diesel RCCI engine with variable premix ratios

“…Apart from these, the advancement of HRF injection angles (−110°CA aTDC) increases higher crevice ow and entrapment of gas mixtures (with atomized diesel) which remain largely unburned and are released with exhaust as UHC. 39 Trends of UHC are found to be logical and supportive of the previously discussed combustion results. Fig.…”

“…40 Sustainable Energy & Fuels Paper a higher premixed ratio increases the accumulation of mixed gases in the cylindrical boundary layer (wall quenching layer), which is nearly stagnant. 39 This stagnant layer hardly participates in the combustion process and unburned or partially burned hydrocarbon from the layer is released with the exhaust as unburned hydrocarbon. Apart from these, the advancement of HRF injection angles (−110°CA aTDC) increases higher crevice ow and entrapment of gas mixtures (with atomized diesel) which remain largely unburned and are released with exhaust as UHC.…”

Investigation of the light-off characteristics and secondary pollutants production mechanism in Pd/Rh catalyst for natural gas engines

“…2 The natural gas engines with three-way catalytic converters (TWC) have become the dominant technology. 3 However, pollutants such as CO and NOx would generate greenhouse gas N 2 O and toxic corrosive gas NH 3 in the catalytic converter, which has received more attention in the latest emission standards. 4 The core of the TWC is a multi-channel ceramic or metal honeycomb structure with a layer of precious metals (Pt, Pd, Rh) coated on the inner walls of the channels.…”

“…2 The natural gas engines with three-way catalytic converters (TWC) have become the dominant technology. 3 However, pollutants such as CO and NOx would generate greenhouse gas N 2 O and toxic corrosive gas NH 3 in the catalytic converter, which has received more attention in the latest emission standards. 4…”