The engine uses ideal gases, a saturated bubbler, complete mixing and uniform irradiation. It predicts gross primary-radical formation, not radicals surviving secondary chemistry or wall losses.
- Vapor added to dry N₂
- Qvapor = QN₂ psat / (Pbubbler − psat)
- Number density
- n = P / (kB T)
- Actual flow
- Qactual = Qstandard (T / Tref) (Pref / P)
- Irradiation time
- tUV = Villuminated / Qactual
- Reaction-section transit
- t = Vbefore exhaust / Qmixed, actual + Vafter exhaust / Qoutlet, actual
- Photolysed fraction
- f = 1 − exp(−σ F φdissociation tUV)
- Radicals formed
- [R] = [precursor]in f φradical / φdissociation
The optional reaction section starts at the mixing tee or, with UV enabled, at the photolysis outlet. Its post-irradiation transit time is not the total age of radicals formed throughout the illuminated tube. Include fixed tube sections; exclude inlet transport and the detector capillary.
With a reactor exhaust, the downstream flow is pump plus detector sampling flow. The upstream section carries the full main + injection flow. This exhaust is separate from the dilution bypass.
F is photon flux in photons cm⁻² s⁻¹. Cross-sections and quantum yields use the cited literature. Missing data remain unspecified, not zero.