On the three charge regimes of bipolar charge conditioners
Notice bibliographique
Résumé
Many aerosol instruments utilize bipolar charge conditioners (neutralizers), including scanning mobility particle sizers (SMPS). The charge distribution from a bipolar charge conditioner must be known to calculate size distributions from SMPS scans. Therefore, a reproducible and known “steady-state” charge distribution is desired to improve measurement accuracy. In this work, we show that although a steady-state charge develops within a common Kr-85 bipolar charge conditioner (TSI 3077A), gaseous ions are readily convected into tubing downstream of the charge conditioner, causing significant deviation from steady-state in less than a second. The “downstream ions” are predominantly positive since negative ions are more readily lost to tubing walls due to their higher diffusivity. Others have previously studied this potential effect, but there is disagreement among them. This study resolves the disagreements, and to the authors’ knowledge, we are the first to: quantify the surprising significance of this effect (mean charge at 239 nm changes by up to a factor of 4); show it occurs rapidly (milliseconds); and demonstrate that a true steady-state distribution is more asymmetric than classical theory (mean charge at 239 nm is >3ñ higher in magnitude). Interaction time of the particles with the remaining free ions downstream of the charge conditioner is shown to be the main consideration for this effect, as demonstrated by varying flow rate, tube length and tube diameter and achieving similar charging results as a function of this time. We perform advanced numerical modeling of charging, convection and diffusion of particles and ions, and show good quantitative agreement with experimental data. These results are further supported by similar charging results measured from a bipolar charge conditioner that has a different internal geometry and ion source than the 3077A charger. To increase consideration of this critical charging effect and enhance understanding of bipolar charging in general, we thereby quantify three distinct regimes of bipolar charging, namely: the (1) charging regime (i.e., as charge develops from its initial to steady-state), (2) steady-state regime, and (3) discharging regime (i.e., effect of “downstream ions”). These three regimes of bipolar charging have wide implications for designing instrumentation, interpreting measurements and validating charging models with the aim of improving accuracy in aerosol instruments such as the SMPS.Copyright © 2025 American Association for Aerosol Research
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».