Motor fuels vapor pressure

The density and the volatility, expressed by the distillation curve and the vapor pressure, constitute the most important physical characteristics of motor fuels for obtaining satisfactory operation of a vehicle in all circumstances. 

The criterion retained up to now in the specifications is not the true vapor pressure, but an associated value called the Reid vapor pressure, RVP. The procedure is to measure the relative pressure developed by the vapors from a sample of motor fuel put in a metallic cylinder at a temperature of 37.8°C. The variations characteristic of the standard method are around 15 millibar in repeatability and 25 millibar in reproducibility. 

For these reasons, ethanol is most likely to find use as a motor fuel in the form of a gasoline additive, either as ethanol or ethanol-based ethers. In these blend uses, ethanol can capture the high market value of gasoline components that provide high octane and reduced vapor pressure. 

Due to the Clean Air Act, increasing attention is paid to the production of alkylates, which is a very clean burning fuel and has a high MON (motor octane number) with a low octane sensitivity and moderate vapor pressure. Commercially operated alkylate production uses a liquid acid catalyst such as H2SO4 or HE, resulting in problems associated with cost, apparatus and the environment [47]. New synthetic methods utilizing solid acid catalysts have been developed but no commercial process has emerged due to fast catalyst deactivation [48]. 

Protein Humidity/water content Hydrocarbons Carboxylic acids Amines Oil/fat Sucrose/glucose Additives in fuels Density Digestibility Viscosity Motor fuel octane number Reid vapor pressure of gasoline Seed germination Distillation parameters Fruit ripeness Total dissolved solids Particle size/fiber diameter Temperature Mechanical properties Thermal and mechanical pretreatment Molar masses of polymers... 

In Fig. 23, spectra of two different grades of U.S. gasoline are shown, de Bakker and Fredericks [90] demonstrated that it was possible to perform a variety of petroleum property measurements, including research octane number (RON), motor octane number (MON), density, benzene content, and flexible volatile index (FVI), using fiber-optical FT-Raman spectroscopy coupled with partial least-squares analysis to reduce sample fluorescence. The potential for on-line measurement of these properties was mentioned by both Cooper et al. [89] and de Bakker and Fredericks [90], Cooper et al. [89,92,93] compared Raman spectroscopy to both mid-IR and near-IR for the measurement of several parameters in fuel mixtures including aromatic concentrations, octane number, and vapor pressures. Cooper et al. similarly utilized partial least squares to accomplish the data analysis. In this series of articles. Cooper et al. described their attempts to quantify mid-IR, near-... 

The dry vapor pressure equivalent (DVPE) of volatile motor fuels is regulated by federal and state air pollution control agencies. In order to meet the letter of these regulations, it is necessary to sample, handle, and test these products in a very precise manner. 

Vapor pressure is an indication of the pressure that a material will develop within a closed container and is particularly significant for materials whose boiling points are so low that they cannot be distilled at atmospheric pressure without serious loss. The test is important with respect to safety in transport, vapor lock in jgasoline feed systems, types of storage tanks employed (Fig. 8-7), and the starting characteristics of motor fuels. 

LPG, stored as a liquid at its saturation pressure, is vaporized and introduced as vapor in conventional spark ignition motors. These motors are not modified with the exception of their feed system. Moreover, in the majority of cases, dual fuel capabilities have been adapted, that is, the vehicle can use either LPG or liquid fuel. 

The specific impulse is generally higher than that for solid motors. A hybrid engine usually consists of a pressurized tank (oxidizer) and a combustion chamber containing the solid propellant (fuel). When thrust is desired, the liquid oxidizer flows into the combustion chamber where it is vaporized and then reacted with the solid fuel at chamber pressures of about 7-10 bar. 

For ambient pressures suflBciently less than the critical pressure of the fuel, the droplet remains in the liquid phase throughout its lifetime. The large liquid-to-gas density ratio then implies that the liquid droplet possesses large thermal and mass inertia compared with the gas phase subsequently the gas-phase processes can be assumed to be quasi-steady. This assumption has been found to be very accurate even at moderate pressures (28), For near-critical or super-critical vaporization occurring typically in rocket motors and diesel engines, unsteady gas-phase analyses are required (29-34,85). 

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