Abstract
New regulations are pushing towards lower and lower allowed levels of pollutants and CO2 (in EU CO2 level is reducing from current 130 g/km to 95 g/km in 2021). While other pollutant levels could be reduced with after treatment devices, CO2 emissions can be reduced only reducing injected fuel and increasing combustion efficiency.
3D CFD simulations are the best option to optimize the combustion chamber and therefore meet the future CO2 targets. The advantages of simulation compared to experiments are that it allows to test several design solutions in a short time and with reduced costs with good accuracy in predicted values; furthermore, it enables to have a detailed insight on what is happening inside the combustion chamber (such as spray and combustion evolution).
The idea behind this work is to use the 3D CFD simulations to test several designs (100 piston bowl shapes) and create a detailed statistical model of geometrical features of Toyota GD engine combustion chamber (2.8L turbocharged diesel engine) in order to use it to detect the driving parameters and maximum possible benefits changing only the chamber shape.
Using this statistical model it is possible to investigate in detail how geometrical features are affecting combustion characteristics (such as ISFC, soot, NOx) and which is the reachable limit that can be achieved without changing calibration and engine architecture. This model showed that the maximum possible reduction in ISFC is approximately 3.5% with benefits also in NOx and Soot production. As far as the NOx is concerned, the maximum reduction is approximately 50% with drawbacks in Soot and ISFC.
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