Influence of the EGR Rate, Oxygen Concentration and Equivalent Fuel/Air Ratio on the Combustion Behaviour and Pollutant Emissions of a Heavy-Duty Diesel Engine

Intake flow structure was studied using various port geometries in a four-valve heavy-duty diesel engine. Swirl ratio, LDV measurements of bulk flow and turbulence, and flow visualization experiments were conducted on a steady-state bench rig. In addition to the standard production port, archetypal intake port flows (swirl, anti-swirl and tumble) were created using intake valve shrouds. These flow types are not usually found in heavy-duty engines, which typically employ quiescent combustion chamber designs. However, recent CFD analyses have indicated that intake flow structures can significantly influence engine pollutant emissions (Fuchs and Rutland, 1998). Thus, it was of interest to characterize these flows in a heavy-duty engine. The measured swirl and axial velocity components were analyzed to reveal the swirl and tumble generation mechanisms, and the LDV data compared favorably with the swirl meter results. The flow visualization confirmed the existence of flow recirculation regions under the intake valves also seen in the LDV data. These flow structures help to explain the origins of the overall swirl and tumble flow fields. The results were also compared with available CFD predictions made using the same port configurations. The measured swirl levels were found to agree with the CFD trends. However, in some cases quantitative differences were found, presumably due to the effect of piston motion in the actual engine. These differences need to be accounted for when evaluating port designs from steady-flow measurements, especially in cases with high tumble flow components. [S0742-4795(00)00804-8]

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Calculation of Intake Oxygen Concentration through Intake CO2 Measurement and Evaluation of Its Effect on Nitrogen Oxide Prediction Accuracy in a Heavy-Duty Diesel Engine

Energies ◽

10.3390/en15010342 ◽

2022 ◽

Vol 15 (1) ◽

pp. 342

Author(s):

Roberto Finesso ◽

Omar Marello

Keyword(s):

Diesel Engine ◽

Oxygen Concentration ◽

Control Unit ◽

Absolute Error ◽

Operating Conditions ◽

Intake Manifold ◽

Heavy Duty ◽

Input Quantity ◽

Heavy Duty Diesel Engine ◽

Heavy Duty Diesel

A new procedure, based on measurement of intake CO2 concentration and ambient humidity was developed and assessed in this study for different diesel engines in order to evaluate the oxygen concentration in the intake manifold. Steady-state and transient datasets were used for this purpose. The method is very fast to implement since it does not require any tuning procedure and it involves just one engine-related input quantity. Moreover, its accuracy is very high since it was found that the absolute error between the measured and predicted intake O2 levels is in the ±0.15% range. The method was applied to verify the performance of a previously developed NOx model under transient operating conditions. This model had previously been adopted by the authors during the IMPERIUM H2020 EU project to set up a model-based controller for a heavy-duty diesel engine. The performance of the NOx model was evaluated considering two cases in which the intake O2 concentration is either derived from engine-control unit sub-models or from the newly developed method. It was found that a significant improvement in NOx model accuracy is obtained in the latter case, and this allowed the previously developed NOx model to be further validated under transient operating conditions.

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