Chemistry of Flash and Fire Points

The flash point is the lowest temperature at which a flammable liquid can form an ignitable mixture in air.

The flash point is the temperature at which vapors can ignite; the fire point is the temperature at which vapors continue to burn after ignition.

Flash and fire points should not be confused with the ignition source temperature or the self-ignition temperature.

<p>Vapor pressure increases with temperature, which raises the concentration of evaporated combustible liquid in the air, affecting the flash point.</p> Signup and view all the answers

<p>In spark ignition engines, the fuel must have a low flash point to ignite easily and a high self-ignition temperature to prevent premature ignition.</p> Signup and view all the answers

<p>The open flash point is measured using the open cup method.</p> Signup and view all the answers

<p>The self-ignition temperature is the lowest temperature at which a substance will spontaneously ignite without an external ignition source.</p> Signup and view all the answers

<p>Knowing the flash point helps in determining safe handling and storage practices for flammable liquids.</p> Signup and view all the answers

<p>Volatility is a measure of a substance's tendency to evaporate, which impacts the distillation of crude oil by determining the range of temperatures at which different hydrocarbons can be separated.</p> Signup and view all the answers

<p>Evaporation is a slow process that occurs at the liquid's surface without external heat influence, while vaporization occurs quickly throughout the liquid when it reaches its boiling point.</p> Signup and view all the answers

<p>The rate of evaporation is influenced by temperature, surface area, humidity, and air movement.</p> Signup and view all the answers

<p>In summer, the high volatility of gasoline ensures easier starting and smooth operation, while in winter, lower volatility can lead to hard starts and poor performance.</p> Signup and view all the answers

<p>Heavier hydrocarbons possess larger molecular weights and stronger intermolecular forces, making them less likely to evaporate compared to lighter hydrocarbons with weaker forces.</p> Signup and view all the answers

<p>As temperature increases, the kinetic energy of the liquid molecules increases, enhancing their escape into the air, thereby increasing volatility.</p> Signup and view all the answers

<p>During evaporation, liquid molecules absorb latent heat from the liquid surface or surrounding air, which enables them to escape into vapor form.</p> Signup and view all the answers

<p>A gasoline distillation curve is a graphical representation that shows the boiling points of various components in gasoline, indicating the percentage of distillable fractions at different temperatures.</p> Signup and view all the answers

<p>They cause distribution problems, leading to knocking in some cylinders while sparing others.</p> Signup and view all the answers

<p>Liquid droplets enter the cylinders and fail to react properly, forming soot that affects spark timing and can damage the spark plug.</p> Signup and view all the answers

<p>Gasoline evaporates within a range of 25°C to 220°C.</p> Signup and view all the answers

<p>These are components that vaporize at low temperatures, essential for smooth cold engine starts and minimizing crankcase dilution.</p> Signup and view all the answers

<p>They are adjusted to meet specific requirements for summer and winter, affecting characteristics like carburetor icing and calorific value.</p> Signup and view all the answers

<p>Heavy hydrocarbons provide calorific value but can lead to liquid droplets causing operational issues and fouling spark plugs.</p> Signup and view all the answers

<p>It governs engine behavior regarding issues like carburetor icing and affects engine performance during sudden acceleration.</p> Signup and view all the answers

<p>They ensure smooth cold engine starting and avoid vapor lock during operation.</p> Signup and view all the answers

<p>The closed flash point is the temperature at which vapors ignite in a closed environment, while the open flash point is the temperature at which vapors ignite in an open environment. The closed flash point is typically lower than the open flash point due to restricted vapor escape.</p> Signup and view all the answers

<p>The fire point is the minimum temperature at which a substance will continue to burn for at least 5 seconds, while the self-ignition point is the temperature at which a substance ignites without an external flame. The fire point is generally higher than the self-ignition point.</p> Signup and view all the answers

<p>The closed flash point for diesel is usually around 52°C, while the open flash point is typically higher at about 60°C. These values can vary slightly based on the specific fuel composition.</p> Signup and view all the answers

<p>Gasoline usually has a flash point range of -43°C to -40°C, while kerosene has a flash point range of 38°C to 72°C. Gasoline is more volatile and poses a greater risk of ignition at lower temperatures.</p> Signup and view all the answers

<p>The test flame is applied at intervals starting from 15°C below the estimated flash point. This helps to accurately determine the point at which ignition occurs.</p> Signup and view all the answers

<p>A stirrer is used to ensure uniform temperature distribution in the oil, which leads to more accurate determination of the flash point. It prevents localized overheating that can alter the results.</p> Signup and view all the answers

<p>The Pensky-Martin apparatus is designed to measure the flash points of petroleum products by providing a controlled environment for controlled heating and ignition tests. It ensures safety and accuracy during the testing process.</p> Signup and view all the answers

<p>An enlargement of the test flame indicates an increase in the concentration of flammable vapors due to the heating of the oil, signaling that the flash point is nearing. This response helps in accurately recording the flash point.</p> Signup and view all the answers

<p>The distillation test is the primary method used to measure the volatility of gasoline.</p> Signup and view all the answers

<p>Volatility is important because it affects the fuel's mixing with air, which is essential for smooth ignition in spark ignition engines.</p> Signup and view all the answers

<p>Higher volatility allows gasoline to evaporate more easily at low temperatures, facilitating cold engine starting.</p> Signup and view all the answers

<p>More volatile gasoline reduces crankcase dilution by minimizing the amount of fuel that condenses and mixes with the lubricating oil.</p> Signup and view all the answers

<p>Vapor lock occurs when fuel evaporates excessively in hot conditions, forming bubbles that prevent fuel from reaching the engine.</p> Signup and view all the answers

<p>Higher gasoline volatility leads to a shorter warm-up time for the engine.</p> Signup and view all the answers

<p>Fuel economy improves with lower gasoline volatility since it reduces vapor escaping from the fuel tank.</p> Signup and view all the answers

<p>Using low volatility gasoline can lead to difficulties in starting the engine and longer warm-up times.</p> Signup and view all the answers

<p>By measuring the time it takes to fill a specific volume of water, the mass flow rate can be calculated using the formula $m_{ow} = \frac{V_w}{time}$.</p> Signup and view all the answers

<p>The corrected mass flow rate formula is $\dot{m} = m \sqrt{\frac{p_f}{p_a}}$.</p> Signup and view all the answers

<p>The higher heating value (HHV) is determined by the energy balance equation $m_w C_{p.w} (t_{two} - t_{twi}) = \dot{m_f} \cdot HHV$.</p> Signup and view all the answers

<p>The lower heating value (LHV) must account for the latent heat of vaporization of the condensed water, represented by the equation $\dot{m} \cdot HHV = \dot{m} \cdot LHV + \dot{m}<em>w.cond imes h</em>{fg}$.</p> Signup and view all the answers

<p>A higher carbon-to-hydrogen ratio typically results in greater water vapor formation, increasing the difference between HHV and LHV.</p> Signup and view all the answers

<p>Hydrogen combustion yields water vapor without producing carbon emissions, leading to a more efficient energy release and lower heat loss.</p> Signup and view all the answers

<p>Yes, waste incineration can produce electricity through the heat generated during combustion, which can be converted to energy using turbines.</p> Signup and view all the answers

<p>The HHV and LHV values for propane and butane differ due to variations in their chemical structures and hydrogen content, which affect combustion characteristics.</p> Signup and view all the answers