外部辐射下汽车变速器油燃烧特性及其火灾危险性研究

Combustion features and the fire risk liability of the automobile transmission oils under the impact of the external radiation

为了加深对汽车上2种典型变速器油（自动变速器油和无级变速器油）火灾危险性的了解,在锥形量热仪上通过耗氧原理对2种油进行了小尺度研究。辐射强度从15 kW/m^2到40 kW/m^2,每5kW/m^2一个标度。试验测得点燃时间、热释放速率、放热总量等一系列参数用以表征油燃烧危险性。基于试验结果,从火灾增长指数、火灾性能指数、热危险性评价等方面讨论了2种油品的火灾危险性：自动变速器油趋于较长燃烧时间,无级变速器油火势增长较快。点燃时间与辐射强度呈指数关系,通过拟合得到2种油品的拟合指数均为0.55。自动变速器油和无级变速器油的临界辐射强度分别为2.949kW/m^2和0.961 kW/m^2。引入Petrella评价体系来判断油品的闪燃危险性,发现油的闪燃危险性随辐射强度增加而增加,综合考虑可得自动变速器油的危险性高于无级变速器油的危险性。因此,建议采取防辐射、安全隔离、选用安全性高的油品等措施来进行火灾预防。

The given paper is inclined to do a bench scale fire experiment in a cone calorimeter based on the standard oxygen consumption method to increase the knowledge of the fire performance of the two kinds of typical flammable car-use transmission oils （ e. g. the automatic transmission oil and the constantly variable transmission oil）. For the experiment to be done, it is necessary to measure the external radiant heat fluxes set from 15 kW/m2 to 40 kW/m2 in steps of 5 kW/m2 so as to make a comprehensive fire hazard assessment of the fluids by using the specific indexes, such as the ignition time, the heat releasing rate and the total heat release. In so doing, we would like to put our emphasis on the examination of the fire risk liabilities of the two kinds of the said transmission oil through the fire growing index, the fire performance index and the other fire evaluation related foctors. As is well known, the automatic transmission oil tends to cause the fire of long duration while the continuously variable transmission oil has a propensity to cause a fast-spreading fire. Thus, the power exponent relation can be deduced between theignition time and the radiant thrmos flux. The fitting results tend to indicate that the power exponent is 0. 55 for both the said transmission oils, while the critical thermos fluxes＂ of the automatic transmission oil and the continuously variable transmission oil should be equal to 2. 949 kW/m2 and 0. 961 kW/m2, respectively. In this paper, we have to adopt the Petrella＇ s evaluation system to obtain the fire burst and cmbustion risk of the corresponding materials through the flashover. It is natural that the risk probability of the flashover tend to increase with the growing thermos flux. Taking all the factors into consideration, it can be expected that the automatic transmission oil tends to face a greater fire risk hazard than the continuously variable transmission oil. Thus, specific measures are to be taken, such as anti-radiation, the safety liability isolation and the frequent safety oil replacement to get rid of the fire risk liabilities. The testing and experimental data gained from our experiments can help to enrich the database of the combustion probabilities of the automobile transmission oils and contribute to the future successful experiemnts and the numerical simulations of the vehicle fire risk lialibities.