No <sub>x.</sub> reduction from a heavy-duty diesel engine with direct injection of natural gas and cooled exhaust gas recirculation
Bibliographic record
Abstract
A heavy-duty ISX diesel engine has been commissioned for single-cylinder operation fuelled with pilot diesel ignited natural gas injected directly into the cylinder. The stock ISX engine was modified by replacing the diesel fuelling system with a high-pressure natural gas system, replacing the turbocharger with an independently controlled supercharger and installing a variable-flow exhaust gas recirculation (EGR) system. A study of the impact of cooled EGR on engine performance and gaseous emissions was carried out. Various engine speeds, loads and injection timings were tested over a range of EGR fractions. A preliminary study of the effect of EGR ‘type’—supplemental or replacement—was also carried out. The results indicate that the NO x emissions varied linearly with the intake oxygen mass fraction (representative of the EGR fraction) until NO x emissions reached 20 per cent of their non-EGR levels. Further NO x reductions were achieved with higher EGR fractions, but the rate of reduction was significantly reduced. The NO x reductions were found to be independent of engine speed and load. An overall activation energy for NO x formation was determined by correlating the NO x reductions with a representative flame temperature. The emissions of combustion by-products, including carbon monoxide (CO) and unburned total hydrocarbons (THC) increased significantly at higher EGR fractions. The engine performance and efficiency were not significantly affected except at very high EGR fractions.
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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 | 0.000 |
| 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) | 0.001 | 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".