Effect of Reformer Gas on HCCI Combustion - Part I:High Octane Fuels
Bibliographic record
Abstract
Homogeneous Charge Compression Ignition (HCCI) engines offer high fuel efficiency and some emissions benefits. However, it is difficult to control and stabilize combustion over a sufficient operating range because the critical compression ratio and intake temperature at which HCCI combustion can be achieved varies with operating conditions such as speed and load as well as with fuel octane number. Replacing part of the base fuel with reformer gas, (which can be produced from the base hydrocarbon fuel), alters HCCI combustion characteristics in varying ways depending on the replacement fraction and the base fuel auto-ignition characteristics. Injecting a blend of reformer gas and base fuel offers a potential HCCI combustion control mechanism because fuel injection quantities and ratios can be altered on a cycle-by-cycle basis. This paper describes an experimental study of reformer gas fuel replacement effects on HCCI combustion with base fuels having sufficient octane number to allow spark ignition operating modes. This would be appropriate for engines designed to start and run at high power using spark ignition but using HCCI combustion to improve efficiency and emissions at part load. An experimental study was carried out using a CFR engine which was modified to achieve high compression ratio for HCCI combustion on primary reference fuel with 100 and 80 octane numbers. A variable blend of the base fuel with simulated reformer gas (75% H2, 25% CO) was used to alter the HCCI combustion characteristics. Experimental results indicated that combustion was retarded by increasing RG fraction in base fuel. It reduced maximum cylinder pressure and maximum cylinder pressure rise rate, leading to a smoother combustion. NOx remained minimal for all operating points. HC and CO increased slightly with RG addition as an indication of lower combustion temperature. It was found that RG replacement with high octane fuels has two advantages. First, it smoothed combustion by retarding combustion timing while maintaining the same λ. Second, it effectively controlled combustion timing when keeping λ and EGR ratios constant.
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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) | 0.002 | 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".