Compression ignition of directly injected natural gas with entrained diesel
Why this work is in the frame
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Bibliographic record
Abstract
A new fuel injector prototype for heavy-duty engines has been developed to use direct-injection natural gas with small amounts of entrained diesel as an ignition promoter. This ‘co-injection’ is quite different from other dual-fuel engine systems where diesel and gas are introduced separately. In an engine with co-injection, diesel and gas are injected simultaneously through one set of nozzle holes as the piston approaches top dead centre. Most of the combustion is non-premixed, as in a conventional diesel engine, but the natural gas supplies over 90 per cent of the energy for typical operating conditions. Reliable compression-ignition can be attained, but two injections per engine cycle are often needed to minimize engine knock. The present paper focuses on 800 r/min light-load operation (equivalence ratio between 0.05 and 0.22) with a single injection per cycle, in order to better understand how the ignition process is affected by in-cylinder conditions and the gas/diesel ratio. Two techniques were used to explore the data: response surface methodology and power-law fits. These methods both showed above a certain diesel/gas ratio that ignition delay approached that of pure diesel injections, but significant knock would occur if the total fuel energy of the injection was high. With high injection pressure and low cylinder pressure, the region of allowable diesel flow (i.e. the region with low knock intensity and high combustion efficiency) was increased for cases with low to moderate gas flow compared with low injection pressure. Injection pressure had little effect at high cylinder pressure, and had no significant effect on ignition delay.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| 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