![]() Therefore, diesel is required to have a high flash point and a low autoignition temperature.ĭiesel varies between 126☏ and 204☏ (52☌-96☌/WJ). Air is compressed until it has been heated above the autoignition temperature of diesel then the fuel is injected as a high-pressure spray, keeping the fuel-air mix within the flammable limits of diesel. Therefore, gasoline is required to have a low flash point and a high autoignition temperature.ĭiesel is designed for use in a high-compression engine. The fuel should not preignite in the hot engine. ![]() The fuel should be premixed with air within its flammable limits and heated above its flash point, then ignited by the spark plug. Petrol (gasoline) is designed for use in an engine which is driven by a spark. The testers and protocols are specified in standards such as DIN 51758, ASTM 93, and Determination of flash point: Closed cup equilibrium method (ISO 1523:2002). The measured value will vary with equipment and test protocol variations, including temperature ramp rate (in automated testers), time allowed for the sample to equilibriate, sample volume and whether the sample is stirred. The flash point is an empirical measurement rather than a fundamental physical parameter. Closed cup testers give lower values for the flash point (typically 5-10 K) and are a better approximation to the temperature at which the vapour pressure reaches the Lower Flammable Limit (LFL). The vapour above the liquid is assumed to be in reasonable equilibrium with the liquid. The main difference being that the former is heated from below, while the later is heated from the sides as well as below.Ĭlosed cup testers, of which the Pensky-Martens closed cup is one example, are sealed with a lid through which the ignition source can be introduced periodically. Examples include Cleveland Open Cup and Pensky-Martens open cup. The measured flash point will actually vary with the height of the flame above the liquid surface, and at sufficient height the measured flash point temperature will coincide with the fire point. In open cup devices the sample is contained in an open cup (hence the name) which is heated, and at intervals a flame is brought over the surface. There are two basic types of flash point measurement: open cup and closed cup. ![]() There is a sufficient concentration of evaporated fuel in the air for combustion to propagate after an ignition source has been introduced. The flash point is that minimum temperature at which Different flammable liquids require differentĬoncentrations of the fuel in air to sustain combustion. Hence, temperatureĭetermines the concentration of evaporated flammable liquid in the air Increases, the concentration of evaporated flammable liquid in the air increases. As the temperature increases, the vapor pressure increases. Every flammable liquid has a vapor pressure, which is a function of
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