圖1 實(shí)驗(yàn)通道的橫截面，顯示緊貼左側(cè)“欄桿”的可燃物。（1）固定欄桿，由9.5mm厚的膠合板構(gòu)成；（2）可移動(dòng)欄桿（也由膠合板構(gòu)成）；（3）1.3mm厚的鋁片；（4）石蠟浸過的硬紙板；（5）實(shí)驗(yàn)期間用于固定硬紙板的角鋼。

The fuel

可燃物

As the obiective of these experiments was to examine the behaviour of the flames rather than to model the fire initiation and growth, the fuel was chosen to give established burning in as short a period of time as possible, with sustained burning for at least 1 min. Cardboard (2 mm thick,98 kg/m') soaked in paraffin (c.3g/m) was found to be suitable: the cardboard acted as a stable wick, allowing the liquid to burn off fairly uniformly. Paraffin is perhaps too volatile for this purpose, but other less volatile fuels which were tried caused the cardboard to char and buckle during flaming, which could give irregular behaviour. With paraffin, the card remained in place until the liquid fuel had been largely consumed, thus allowing the behaviour of the flames to be observed.

由于此實(shí)驗(yàn)的目的是研究火焰行為，而不是模擬火焰發(fā)生發(fā)展的，因此選擇的可燃物要在短時(shí)間內(nèi)進(jìn)行穩(wěn)定燃燒，至少持續(xù)燃燒1分鐘。浸有石蠟（c.3g/m2）的硬紙板（2mm厚，98kg/m2）是較為合適的可燃物。硬紙板作為穩(wěn)定的燈芯，可使液體均勻穩(wěn)定的燃燒。根據(jù)此實(shí)驗(yàn)?zāi)康?，石蠟可能揮發(fā)性過強(qiáng)，但是如果使用其他揮發(fā)性較差可燃物，會(huì)導(dǎo)致燃燒過程中硬紙板炭化和變形，繼而產(chǎn)生不規(guī)律的行為。直到液體可燃物幾乎被完全燃盡前，浸有石蠟的紙片將一直保持原位，以便觀察火焰行為。

Sections of paraffin-soaked card, 20 cm in length, were held against the sides and fioor of the channel by lengths of thin-section, mild-steel angle. Ignition was achieved by using a gas torch to set alight pieces of paraffin-soaked string lying along the foot of the "balustrades'. Card on the floor' was ienited by direct fiame contact along its lower edge.Complete involvement of the fuel-bed surfaces was normally achieved within 20-30s, and quasi-steady burning lasted for another 60-75 s.

將長(zhǎng)20cm浸有石蠟的紙片，鋪設(shè)在通道的側(cè)面和底面上，并用角鋼和薄片固定。使用氣體點(diǎn)火器點(diǎn)燃放置在“扶梯”底部浸有石蠟的細(xì)繩，實(shí)現(xiàn)引燃。“地板”上的紙片被來自下方的火焰直接點(diǎn)燃。通常在20~30s內(nèi)，可燃物表面將完全處于燃燒狀態(tài)，準(zhǔn)穩(wěn)態(tài)燃燒可再持續(xù)60-75s。

Several series of experiments were carried out, but the most important involved a section of channel which was in the same proportion as the King's Cross escalator. The behaviour of the fames that were observed characterise the so-called 'trench effect' very well. The 20-cm lengths of paraffin-soaked card were located with their lower edges 50 mm from the foot of the channel. Figures 2-7 compare three situations in which only one side ('balustrade') is burning (Figs 2 and 3), (i) in which both sides are burning (Figs 4 and 5), and (ii) in which both sides and the "floor' are burning (Figs 6 and 7). It was noted that when only a section of "floor' was burning, the flames remained in the channel, flowing upwards at an angle of 30, hugging the floor above the burning section: the implications for fiame spread are discussed elsewhere.

雖然進(jìn)行了多組實(shí)驗(yàn)，但最重要是在與國(guó)王十字站扶梯比例相同通道內(nèi)進(jìn)行的實(shí)驗(yàn)。所觀察到的火焰行為，很好地表征了所謂的“溝槽效應(yīng)”。浸有石蠟的長(zhǎng)20cm紙片從距離底邊50mm的位置開始鋪設(shè)。圖2-7對(duì)比了三種情況：（1）只有一側(cè)（“欄桿”）燃燒（圖2和3）；（2）兩側(cè)都燃燒（圖4和5）；（3）兩側(cè)和“地板”都燃燒（圖6和7）?？梢钥吹剑?dāng)只有“地板”一面燃燒時(shí)，火焰被限制在通道內(nèi)，緊貼著燃燒區(qū)域的上部地板，沿30°傾斜面向上蔓延燃燒。此種火焰蔓延情況將在他處論述。

When only one side is burning, the fames are observed to rise vertically (Figs 2 and 3). When both sides are alight, the flames are deflected towards the centre-line of the channel, their tips merging (as shown in Fig. 4), and also towards the slope of the channel, effectively reducing the height of the flames as seen from the side (Fig. 5). When both sides and the floor are alight, the flames interact and are deflected o such an extent that the confinement to the channel is almost complete (Figs 6 and 7).

當(dāng)只有一側(cè)燃燒時(shí)，觀察到的火焰是垂直向上（如圖2和圖3）。當(dāng)兩側(cè)都在燃燒時(shí)，火焰將偏向通道的中心線，其火焰前鋒發(fā)生合并（如圖4），也會(huì)偏向通道斜坡，從側(cè)面看顯著降低了火焰高度（如圖5）。當(dāng)兩側(cè)和地板都燃燒時(shí)，火焰相互作用，并會(huì)傾斜到完成限制在通道燃燒的程度（如圖6和圖7）。

The same type of behaviour was observed when the burning surfaces were located near the top (within 200 mm) of the channel, and when the length of the burning fuel bed was reduced from 20 to 5 cm. The effect of channel width was also investigated, albeit superficially. It was more pronounced for 'a 200-mm-wide channel, but there was still some fame deflection when one side was completely removed (infinite width), provided the floor was alight.

當(dāng)燃燒表面位于通道頂部200mm附近，且當(dāng)可燃物長(zhǎng)度由20cm減至5cm是，觀察到了相同火焰行為。同時(shí)，研究了通道寬度對(duì)火焰特征的影響，但研究不夠深入。通道寬為200mm時(shí)，現(xiàn)象更為明顯，但只要地板被引燃后，即使是一側(cè)墻被完全拆除后，有些火焰仍會(huì)出現(xiàn)偏向通道的情況。

The scale experiments described in this paper clearly reveal a type of flame behaviour which had not previously been identified. If the internal surfaces of an inclined channel are burning, the flames are deflected into the channel if the angle of inclination is 30 ° . The effect is greatest if the floor is burning, but there is evidence that it will occur to a significant extent if only the sides are involved. The effect is enhanced in narrow channels, although the limits have not been ascertained. No attempt was made to model either the confining shaft or the combustible side wall that were present in the King's Cross fire. The fact that the channel itself was capable of confining the flames and keeping them below the 'handrail' level is consistent in a qualitative sense with the dynamics of natural diffusion flames, which satisfy their demand for oxygen by entraining air from the surrounding atmosphere.

本文所述的1：3比例實(shí)驗(yàn)清晰地揭示了一種以前未發(fā)現(xiàn)的火焰行為。如果通道傾斜30°，通道內(nèi)側(cè)發(fā)生燃燒，火焰將向通道傾斜。雖然地板燃燒時(shí)，現(xiàn)象最為明顯，但也有證據(jù)表明，只要一側(cè)壁面燃燒，此現(xiàn)象也會(huì)出現(xiàn)。雖然邊界條件尚未明確，但狹窄通道將強(qiáng)化此種現(xiàn)象。實(shí)驗(yàn)沒有模擬國(guó)王十字站火災(zāi)中的豎井和易燃側(cè)面。通道自身能夠限制火焰并將其保持在“扶手”水平高度以下，這一事實(shí)在本質(zhì)上與自然擴(kuò)散火焰動(dòng)力學(xué)是一致的，后者通過從周圍大氣中吸入空氣來滿足其對(duì)氧氣的需求。

Moreover, such behaviour can account for two critical features of the original fire-why it was not perceived much earlier that a life threatening situation was developing, and why the fire spread so rapidly into the booking hall. The former is consistent with flame deflection into the escalator channel (cf. Fig. 7): none of the survivors reported seeing "large flames' before the fire erupted into the ticket hall-not even Fireman Bell, who descended an adjacent escalator (No. 6) only 2 or 3 min previously.5 The rapid spread of fiame up the escalator is consistent with high rates of heat transfer generated by fiames and hot gases deflected upwards between the wooden balustrades. This hypothesis was subsequently confirmed in the t-scale tests carried out at the Health and Safety Executive Laboratories at Buxton (Derbyshire, UK).

此外，這種火焰行為可以解釋火災(zāi)初期的兩個(gè)關(guān)鍵問題，即：為什么人們沒有在初期火災(zāi)發(fā)展到危及人的生命之前，更早地發(fā)現(xiàn)火災(zāi)？為什么火災(zāi)會(huì)如此迅速地蔓延至售票大廳？第一個(gè)問題與實(shí)驗(yàn)中火焰向自動(dòng)扶梯通道內(nèi)傾斜的研究結(jié)果一致（如圖7）：在火燒到售票大廳前，沒有一名幸存者表示看到過“大火焰”，甚至消防員Bell也沒有發(fā)現(xiàn)，他在火災(zāi)前2～3分鐘乘相鄰的（6號(hào)）自動(dòng)扶梯下來。實(shí)驗(yàn)中在木質(zhì)壁面之間，向上的火焰和熱煙氣造成的快速熱量傳遞與實(shí)際火災(zāi)中火焰在自動(dòng)扶梯上的迅速蔓延是一致的。隨后在Buxton（英國(guó)德比郡）的健康與安全實(shí)驗(yàn)室（Health and Safety Executive Laboratories）進(jìn)行的1：3比例的實(shí)驗(yàn)證實(shí)了這種假設(shè)。

It is likely that this behaviour will not be unique to escalators and may be observed in other inclined combustible surfaces with an appropriate degree of confinement.' A better understanding of the controlling factors is required so that other configurations which are capable of rapid fire growth can be identified. Such work is currently in hand at Edinburgh University.

此種火焰行為并非只自動(dòng)扶梯處發(fā)生，當(dāng)限制條件合適時(shí)，在其它切斜可燃平面也可能發(fā)生。這就需要更深入的了解控制因素，以便可以識(shí)別出其它可能造成火勢(shì)快速結(jié)構(gòu)。目前愛丁堡大學(xué)正在進(jìn)行此項(xiàng)研究。

1. Simcox, S, Wilkes, N. S. & Jones, I. P, Fire at King's Cross Underground Station, 18th November 1987: Numerical simulation of the buoyant flow and heat transfer. Report No. AERE-G 4677, Harwell Laboratory, Harwell, UK, 1988.

2. Markstein, G. H. & De Ris, J., Upward fire spread over textiles, l~h Symposium (International) on Combustion. The Combustion Institute, Pittsburgh, PA, USA, pp. 1085-97.

3. Drysdale, D. D, Introduction to Fire Dynamics. John Wiley & Sons, Chichester, UK, 1985.

4. Drysdale, D. D. & Macmillan, A. J. R. Flame spread on inclined surfaces. Fire Safety J. (in press).

5. Fennell, D, Investigation into the King's Cross Underground Fire. HMSO, London, UK, 1988, Ch. 12.

6. Moodie, K. & Jagger, S. F., The King's Cross Fire: Results and analysis from the scale model tests. Fire Safety J, 18(1) (1992) 83-103.