Cold-Flow Investigation of the Darmstadt Engine with Focus on Statistical Convergence: Experimental and Large Eddy Simulation Analysis

In fluid mechanics research, data gathered from measurements and simulations may be challenging to interpret due to complexities such as transience, non-linearity, and high dimensionality. Velocity data from the airflow through an internal combustion engine often exhibit such properties; nevertheless, accurate characterizations of these airflows are required in order to correctly predict and control the subsequent combustion and emission processes in pursuit of net zero targets. The temporal mean is a common way of representing an ensemble of realizations of velocity fields, but the averaging process can artificially diminish the magnitudes of the resultant vectors. Accurate representation of these vector magnitudes is of particular importance, as the velocity magnitudes in the intake airflow are thought to be primary drivers of the subsequent variation in an engine flow, which influences emission formation and overall efficiency. As an alternative to the ensemble mean, this work proposes the application of a dimensionality reduction method known as the sparsity-promoting dynamic mode decomposition (SPDMD), which can extract core structures from an ensemble of velocity fields while retaining more realistic vector magnitudes. This is demonstrated for the first time with large-eddy simulation (LES) velocity data and compared to a corresponding set of experimental particle image velocimetry (PIV) data. The SPDMD 0 Hz modes are shown to be more representative of the velocity magnitudes present in both datasets. This facilitates more accurate quantification of the differences in vector magnitudes between simulations and experiments, and more reliable identification of which LES snapshots are closer to the PIV ensemble.

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Experimental and Numerical Momentum Flux Analysis of Jets from a Hydrogen Injector

Postrioti,

Martino,

Fontanesi

et al. 2024

SAE Technical Paper Series

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<div class="section abstract"><div class="htmlview paragraph">The use of hydrogen in internal combustion engines is an effective approach to significantly support the reduction of CO<sub>2</sub> emissions from the transportation sector using technically affordable solutions. The use of direct injection is the most promising approach to fully exploit hydrogen potential as a clean fuel, while preserving targets in terms of power density and emissions. In this frame, the development of an effective combustion system largely relies on the hydrogen-air mixture formation process, so to adequately control the charge stratification to mitigate pre-ignitions and knock and to minimize NOx formation. Hence, improving capabilities of designing a correct gas jet-air interaction is of paramount importance. In this paper the analysis of the evolution of a high-pressure gas jet produced by a single-hole prototype injector operated with different pressure ratios is presented. The experimental analysis is carried out using global momentum flux measurement with the support of Schlieren imaging and needle lift detection. A combined CFD analysis of the injection process is used to investigate the details of the momentum flux device operation, offering an interesting insight in the measurement mechanisms and in the jet evolution. The final goal of the combined experimental-numerical approach is to provide quantitative description of the injection process dynamics and spatial/temporal jet evolution and morphology so to support the combustion system design.</div></div>

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Cold-Flow Investigation of the Darmstadt Engine with Focus on Statistical Convergence: Experimental and Large Eddy Simulation Analysis

Cited by 3 publications

References 66 publications

Cause-and-effect chain analysis of combustion cyclic variability in a spark-ignition engine using large-eddy simulation, Part I: From tumble compression to flame initiation

Cause-and-effect chain analysis of combustion cyclic variability in a spark-ignition engine using large-eddy simulation, Part I: From tumble compression to flame initiation

Extracting vector magnitudes of dominant structures in a cyclic engine flow with dimensionality reduction

Experimental and Numerical Momentum Flux Analysis of Jets from a Hydrogen Injector

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