Characterization of Knocking on Spark Assisted Compression Ignition Mode in a Rapid Compression Machine
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Bibliographic record
Abstract
Abstract Spark-assisted compression ignition (SACI) employs a direct spark event to control the combustion phasing of homogeneously charged compression ignition mode. However, the induced deflagration process results in elevated pressure and temperature within the unburned gas zone, leading to the end gas autoignition. In addition, the rapid heat release in the chamber potentially leads to the internal damage caused by conventional knocking, heavy knocking, or detonation knocking. This represents the primary challenge to improving power density and thermal efficiency under a high compression ratio and boosted engine. This study investigates knocking combustions and characterizes the oscillating pressure waves from the end gas autoignition using the DME/air mixtures in a rapid compression machine. The circumferential frequency of the vibration modes is computed with respect to the combustion chamber (Ø50mm). The first (11.5kHz) circumferential mode is the primary focus to explore the impact of end-gas autoignition on the individual wave intensity since they contain the majority of the acoustic energy from the decomposed harmonic waves. A detailed analysis of the ringing intensity, knock intensity, and duration of ratio on excitation to residence are performed to characterize the knocking behaviors under the HCCI and SACI combustion modes. The high-speed images are utilized to observe the end-gas autoignition onset timing and process, and identify transition of the fast flame propagation to detonation which exceeds 2km/s. The knocking suppression is also investigated by increasing the excessive air-fuel ratio up to lambda 2.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it