- Détails du magazine
- Format
- Magazine
- eISSN
- 2719-9509
- Première publication
- 01 Jan 1992
- Période de publication
- 4 fois par an
- Langues
- Anglais

#### Chercher

#### Résumé

The importance of the metrology function at Philip Morris Europe (PME), a multinational organisation producing at over 40 sites in the European, Middle Eastern and African Regions is presented. Standardisation of test methods and equipment as well as the traceability of calibration gauges to the same reference gauge are essential in order to obtain comparable results among the various production centers. The metrology function as well as the qualification of instruments and the drafting of test and calibration operating procedures for this region are conducted or co-ordinated by the Research and Development Department in Neuchatel, Switzerland. In this paper the metrology function within PME is presented based on the measurement of the resistance to draw for which the PME R&D laboratory is accredited (ISO/CEI 17025), as both a calibration and a testing laboratory. The following topics are addressed in this paper: traceability of calibration standards to national standards; comparison of results among manufacturing centres; the choice, the budget as well as the computation of uncertainties. Furthermore, some practical aspects related to the calibration and use of the glass multicapillary gauges are discussed.

- Accès libre

The Use of Nonlinear Constitutive Equations to Evaluate Draw Resistance and Filter Ventilation

Pages: 177 - 188

#### Résumé

This study investigates by nonlinear constitutive equations the influence of tipping paper, cigarette paper, filter, and tobacco rod on the degree of filter ventilation and draw resistance. Starting from the laws of conservation, the path to the theory of fluid dynamics in porous media and Darcy's law is reviewed and, as an extension to Darcy's law, two different nonlinear pressure drop-flow relations are proposed. It is proven that these relations are valid constitutive equations and the partial differential equations for the stationary flow in an unlit cigarette covering anisotropic, inhomogeneous and nonlinear behaviour are derived. From these equations a system of ordinary differential equations for the one-dimensional flow in the cigarette is derived by averaging pressure and velocity over the cross section of the cigarette. By further integration, the concept of an electrical analog is reached and discussed in the light of nonlinear pressure drop-flow relations. By numerical calculations based on the system of ordinary differential equations, it is shown that the influence of nonlinearities cannot be neglected because variations in the degree of filter ventilation can reach up to 20% of its nominal value.

- Accès libre

A Mathematical Scheme for Calculating Flows and Pressure Drops in Lit and Unlit Cigarettes

Pages: 189 - 203

#### Résumé

A computational methodology is presented for evaluating the flows and pressure drops in both lit and unlit cigarettes. The flows and pressure drops across rows of tipping-paper perforations are considered explicitly, as are the locations and relative sizes of the ventilation holes. The flows and pressure drops across air-permeable cigarette papers are included. The influence of plugwrappermeabilities on filter ventilation is developed. Lit cigarettes are mimicked by adding a “coal” pressure drop to the upstream end of the cigarette. The computational scheme is used to predict the effects of tobacco-rod length, puff volume, and vent blocking on cigarette ventilation and pressure drop. A derivation of the pressure-drop and flow equations for a cigarette with an upstream pressure drop is included in an appendix.

#### Résumé

Oxygen diffusion coefficients in normal and decomposed cigarette papers were measured, and oxygen transfer through the cigarette papers was estimated. The oxygen diffusion coefficient varied with the properties of the cigarette papers, however, the differences in the oxygen transfer coefficient were not very large. The oxygen diffusivity of the cigarette papers did not increase after thermal decomposition. No correlation was found between the oxygen transfer coefficient of the normal paper and the decomposed paper.

- Accès libre

A Review of the Incidence and Consequences of Cigarette Filter Vent Blocking Among Smokers

Pages: 209 - 228

#### Résumé

Vent blocking, the covering of the filter ventilation zone on a cigarette during smoking, is a potentially important aspect of smoking behavior. Various techniques have been used to assess the incidence of vent blocking, and widely different views have been expressed on its importance. Studies relevant to filter vent blocking have been reviewed with two overall objectives: to examine critically the evidence on the occurrence of vent blocking and to assess the effects of vent blocking on the smoke yield to the smoker. The reviewed studies fall into four main categories: (1) measurements of the incidence of filter vent blocking among smokers; (2) the observed effects of vent blocking on cigarette ventilation and machine smoke yields; (3) the effect of experimentally blocking vents on human smoke yields; and (4) simultaneous determination of vent blocking and smoke yield under human smoking conditions. Direct observation indicates that only 4% of smokers have their fingers in direct contact with the cigarette during puffing. Estimates of vent blocking incidence by lips during smoking range from 15-24% (saliva-staining technique) to up to 50% ('tar’ staining pattern technique) of smokers. For those smokers who do block the ventilation zone, a mean of 27% of the vents are blocked, and a maximum of about 50%. When the cigarettes are machine-smoked, the smoke yield increases in a highly non-linear manner as the blocked portion of the filter ventilation zone increases. This effect is also more pronounced at higher original filter ventilation levels. In contrast, smoking behavior monitoring techniques have shown that when the experimenter deliberately blocks the vent zone, the human smoker adjusts by taking smaller and fewer puffs. The blocked filter affects the yields of smoke components to the smoker less than it does smoking-machine measured yields. It is concluded that the incidence of vent zone blocking by fingers is quite low and relatively insignificant. The most reliable estimate for lip blocking is that up to 25% of smokers may cover the vent zone during at least one puff and for most smokers the coverage is partial. Ventilation zone blocking as it occurs in practice has only a relatively minor effect on human smoke yields compared to other smoker behavior factors. When a human smoker inadvertently partially or completely blocks the filter ventilation zone during smoking, he/she adjusts by taking smaller and fewer puffs. Because of these changes in puffing behavior during human smoking, predictions of the effects of filter vent blocking on smoke yields based solely on smoking machine yields are deceptive.