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.
We investigated the relationship between the smoldering burn rate and the heat transfer from a burning cigarette by measuring the heat emitted by radiation and convection, separately. The net heat generated and the net heat emitted by a burning cigarette did not vary with a change of the cigarette smoldering burn rate. The total heat emitted from a statically burning cigarette was about 50% of the total combustion heat. About 50% of the heat emitted was released as radiation heat. The smoldering burn rate did not affect the total amount of heat emitted nor the ratio of radiated heat to convected heat.
K Miura, S Kitao, Y Egashira, N Nishiyama and K Ueyama
A propagation model of cigarette static burn at the cigarette periphery is proposed. Propagation of cigarette static burn is characterized by intermittent burn of the cigarette paper. The burning rate depends on the period of flash burn of the paper and is independent of the burning width. By measuring the local temperature near the front line of the burning propagation, the rate-determining step was identified as the time required to ignite the paper. A mathematical analysis was performed by calculating the heat transfer at the periphery during the paper heating period, and it was revealed that the thermal properties of the cigarette are the dominant factors of cigarette static burn. Modeling results showed good agreement with measured data.
In order to clarify the mechanism for the generation of cigarette smoke, the combustion mechanism of a burning cigarette during a puff was investigated by focusing on air transfer. In particular, the air flow distribution outside a burning cigarette was observed and related to the aerodynamic effects of the cigarette paper and the puffing rate. The air flow rate was measured by Particle Image Velocimetry (PIV), using olive oil droplets as the tracer particles. It was found that air does not flow into the tip of the burning cigarette and that the air flow was concentrated at the region -2 to 2 mm around the cigarette paper char-line. This behavior was independent of the cigarette paper basis weight. When the puffing rate was changed from 2.5 to 35 mL/s, the air flow was concentrated at a region close to the cigarette paper char-line and the maximum velocity around the cigarette paper char-line increased with the puffing rate.
The combustion mechanism of a shredded tobacco bed during puffing has been investigated. To evaluate changes in the burning rate of the shredded tobacco bed in the region close to the paper char-line, an experimental study was carried out on the reverse combustion of the shredded tobacco bed packed in a furnace. Measurements of the temperature in the shredded tobacco bed were conducted to calculate the combustion propagation rate. The combustion propagation rate decreased with an increase in the tobacco shred width, the tobacco packing density, and with a decrease in the air flow velocity. To investigate differences in the combustion propagation rate, the oxygen transfer coefficient of the shredded tobacco bed was evaluated using the effective diameter of the tobacco shred and the effective surface area of the shredded tobacco bed. The combustion propagation rate of the shredded tobacco bed increased with the oxygen transfer coefficient of the shredded tobacco bed. Furthermore, the weight loss of the cigarette during puffing was evaluated. The weight loss of the cigarette during puffing showed an increase with an increase in the oxygen transfer coefficient of the shredded tobacco bed.
The transient temperature distribution inside a burning cigarette during a 2-second constant-draw single puff was measured to determine the heat generation rate at various positions. The calculation of the heat generation was applied only to a vertically positioned cigarette. The solid-phase temperature was measured by an infrared thermometer with an optical fiber probe, and the gas-phase temperature was measured by a thermocouple. Heat generation rates at various positions inside the burning cigarette were obtained from the temperature distribution profile based on the heat balance equations. Heat generation was found to be concentrated within a region 2 to 3 mm behind the paper char line. The maximum heat generation rate was observed during the initial period of puffing and the heat generation rate decreased significantly in the interval during the middle unsteady period. Steady heat generation was observed in the latter period. The puffing volume as well as the properties of cigarette paper affected the heat generation rate during the unsteady period. The amount of the heat generated during the unsteady period was more than half of the total regardless of the cigarette paper basis weight and the puffing volume.
S. Kurinobu, O. Chigira, K. Matsune, M. Miura and M. Naiem
Nine provenances of Albizia falcataria were planted at three square spacing levels (2, 3, and 4 m) in a split-plot design at Jember in East Java, Indonesia and measured annually for six years, which is three quarters of its rotation age. The effect of spacing on mean height development became progressively evident, due to the decline in growth at closer spacing caused by intensified competition, in six provenances, i.e., three provenances each from Java and East Indonesia, which were considered better adapted to the site because of their better growth and higher survival. On the contrary, the height growth curves of two provenances from New Guinea were almost identical, irrespective of spacing, indicating a lack of plasticity to the favorable environment at wider spacing. Dominant height was defined as the average of the five tallest trees per sub-plot (350 stems/ha), the growth curves at the three spacing levels were similar in the above-mentioned six provenances and were regarded as a single curve according to AIC-values. In contrast, dominant height growth curves of the New Guinea provenances were differentiated in the order of 2, 3, and 4 m spacing, approximately proportional to the intensity of choosing dominant trees per sub-plot. These results suggest that provenance variation exists for mean and dominant height and their response to different spacing. The cause of this variation was presumably attributable to the difference in competitive ability as well as the plasticity to the given environment. The use of dominant height for growth modeling of A. falcataria was found to be the most suitable for the adapted provenances.