Experimental and Computational Investigation of a Quarter-Wave Resonator on a Large-Bore Marine Dual-Fuel Engine
Bibliographic record
Abstract
Large pressure pulsations and a non-uniform distribution of charge air temperature along the intake manifold were detected on a large-bore marine Dual-Fuel engine. These two phenomena were found to impact negatively on the knock resistance of individual cylinders, when the engine is operated in gas-mode. As it happens with marine gas engines, the cylinder most prone to knocking drives the engine tuning for all the others, thus reducing the overall fuel conversion efficiency. In order to effectively tackle this issue, a comprehensive study was carried out, which included both experimental testing and fluid-dynamics simulation. A detailed GT-POWER 1D engine model was built, representing the laboratory 8L (i.e. inline eight-cylinder) engine configuration. The model was extensively correlated against measurements at different speeds and loads and it proved capable of closely reproducing both the pressure fluctuations and the temperature gradient along the intake manifold. Models for the other cylinder configurations (6L, 7L, 9L, 12V, 14V and 16V) were built scaling the validated 8L one. Linear acoustic analyses were then used to investigate the eigenvalues (natural frequencies) of the intake air path, for each engine variant. It was possible to infer that the second natural frequency of the intake volumes is to be considered as the main cause of the pressure fluctuations. The temperature gradient was on the other hand identified as a side-effect of the large pressure oscillations, as they increase locally the heat transfer coefficients between the charge air and the warm manifold walls. A quarter-wave resonator was designed, which was tuned on the resonance frequency to mitigate the pressure pulsations. For packaging reasons, it was decided to place the resonator inside the air receiver. As the resonator length was very close to the manifold’s one in some cylinder configurations, a bent resonator pipe was proposed. Its shape, cross-section and dimensions were investigated in detail and optimized by means of 1D and 3D CFD analyses. Eventually, tests on the 8L laboratory engine, fitted with the quarter-wave resonator of choice, supported the simulation results: pressure pulsations decreased by 40% and, after engine re-tuning, brake efficiency increased by 0.3% (absolute) at the same knock-margin.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".