Rapid Prototyping for Optimization of the Charge Motion in Internal Combustion Engines Driven by Sewage Gas

This paper presents a newly developed method using rapid prototyping (RP) to develop gas engine cylinder heads with optimized charge motion characteristics to adapt to lean-burn and Miller combustion process requirements. The geometry in close vicinity to the inlet valve seats was designed to increase swirl and flow performance of the cylinder heads. A three-dimensional (3D) printer was used to realize a rapid prototyping concept for the testing of multiple designs; the effects of the different designs were measured using a static flow test bench and a laser-optical method to visualize the flow patterns. The results of the static flow bench tests showed potentially higher flow and swirl performance, with one high-swirl version proving beneficial specifically for lean-combustion and one high-flow version matching the Miller combustion requirements. The two cylinder head versions were then manufactured and the lean-combustion version was tested for on-engine performance on a 150kW sewage-gas driven lean-combustion engine. It has been shown that the cylinder head generates higher swirl on the test bench but achieves only a slight increase in combustion speed on the test engine. The potential to increase engine efficiency by intensifying swirl is, therefore, considered exploitable. Research has further shown the coefficient of variance (CoV) was reduced by 0.3-1.2%. Charge exchange losses have also been demonstrated to decrease at all tested engine settings. It has further been found that higher swirl intensity has a positive impact on engine emission levels, as the engine out carbon monoxide (CO) emission can be reduced by approximately 70mg.m(-3).