Effect of Transient Gasdynamic Processes on the Impulse of Pulse Detonation Engines
Bibliographic record
Abstract
Introduction I N a pulse detonation engine (PDE), thrust results from the expansion of the high-pressureand temperature products of a detonation. Much of the effort in PDE development has been focused on the rapid initiation of detonation to achieve detonation in a distance compatible with the dimensions of an engine. The question of whether the impulse generated depends on different gasdynamic processes, such as direct initiation, de agration to detonation transition (DDT), or constant volume explosion, becomes a valid one. In the present study, the impulse produced by a single-cycle hydrogen–oxygen PDE is experimentally investigated.The goal is to determine the effect of transient gasdynamic processes on impulse. The impulse producedby direct initiation is compared to that producedby DDT for two different initiation locations,at the thrust wall and at the open end. The equivalence ratio is varied to control the run-up distance (RUD). The impulse is measured in two ways: the ballistic pendulum method and the integration of the end wall (thrust wall) pressure. The former, the ballistic pendulum method, was rst applied to measuring the impulse generated by a detonation by Nicholls et al. and has recently been used by Cooper et al. and Daniau et al. to measure the effect of obstacles and nozzles on the impulse generated by a single detonation pulse. Harris et al. also used a ballistic pendulum to study the effect of nitrogen dilution and compared the impulse for the cases of direct initiation and DDT initiated from the closed end of the tube. In the ballistic pendulum technique, the amplitude of swing of a pendulum-mounted PDE provides a direct measurement of the total integrated thrust. The latter technique, integrating the end wall pressure, is more typically used in PDE experiments, but will only produce an accurate measurement of impulse if friction and other momentum losses are negligible.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".