Volumetric fuel consumption

FIGURE 5-4. Relationship Between Fuel Density and Volumetric Fuel Consumption in DI and IDI Engines... 

Two approaches may be used to replace petroleum fuels with alcohol fuels. The first is to blend the alcohol with the petroleum fuel in mixtures that contain 5 to 20 volume percent alcohol. Blending alcohols with petroleum fuels at such levels may allow operation of unmodified vehicles with little noticeable change in the volumetric consumption of fuel per unit of distance traveled. (The question of whether or not the volumetric fuel consumption changes for alcohol blends is a topic of current research and debate.)... 

To meet the requirements of fuel consumption and emissions, modern fuel-injection systems require precise metering of the intake air mass. There are two main approaches direct and indirect measurement. In the indirect method the density of the air upstream of the intake valves is determined by measuring pressure and temperature, volumetric flow is determined from engine speed and displacement, including the volumetric efficiency of the engine. With direct measurement the disadvantages of the indirect method (adulteration due to exhaust gas recirculation and changes in the volumetric efficiency) can be avoided. 

In the United States, for instance. Volumetric Excise Tax Credits for the blending of fuel ethanol and biodiesel are being provided to biofuel producers under the American Jobs Creation Act since 2004. In the European Union, the Energy Taxation Directive permits exemptions or reductions from energy taxation for biofuels (Directive 2003/96/EC). Currently, nearly all EU member states (with the exception of Finland and the Netherlands) provide partial or total tax exemptions or deduction, most aimed at hnal consumption (European Commission, 2011). Because the tax exemption has an upper bound equal to the acmal level of the fossil fuel tax, the instrument has proven to be highly effective in those EU member states with fossil fuel tax levels high enough to compensate for the additional production costs of biofuels (Wiesenthal et al., 2009). 

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