Heat Release Characteristics of a Volatile, Oxygenated, and Reactive Fuel in a Direct Injection Engine
Bibliographic record
Abstract
Abstract Compression ignition diesel engines offer a power dense solution for heavy-duty on-road vehicles. The purpose of combustion management for diesel engines primarily concerns the balance of high efficiency and low emissions. Conventional diesel combustion, i.e. single-shot fuel scheduling, is subject to an extended overlap of fuel injection and combustion promoting the diffusion mode of combustion, that is one highly efficient yet prone to form excessive amounts of nitrogen oxides (NOx) and soot emissions. The application of exhaust gas dilution to reduce NOx below regulation limits leads to an increase in smoke emissions, further magnifying the emission control dilemma. Dimethyl ether (DME) contains suitable reactivity for compression ignition engines while also possessing distinct characteristics to diesel, notably physical properties such as volatility and oxygen content, which significantly lowers engine-out soot emissions. In turn, DME enables direct NOx control via oxygen dilution. Nonetheless, the influence of charge dilution towards the combustion heat release behavior of DME persists. In this study, the heat release pattern of high-pressure DME combustion was investigated in a single-cylinder direct injection engine. The conventional combustion mode was employed, i.e. a single-shot fuel scheduling, with the start of fuel injection fixed at top dead center wherein the in-cylinder temperature and pressure are highest, and the combustion proceeds in an expanding volume. Throughout the study, the fuel injection pressure, engine load, and oxygen dilution were adjusted separately to characterize their influence on the subsequent combustion process. Diesel combustion operated at matching conditions was used to provide reference and relevance to the results. Most notably, the period of diffusion burning was extended in DME following a longer period of injection-combustion overlap. To add, the heat release of DME combustion was repeatedly shorter than diesel owing to the lack of end-burning combustion phase inherent to diesel combustion.
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How this classification was reachedexpand
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".