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The calculated ignition index (CII), together with the calculated carbon aromaticity index (CCAI), are empirical indicators which describe the characteristics or properties of a fuel. [1] Both CII and CCAI are calculated from the density and kinematic viscosity of the fuel.
As the name suggests, CCAI is a calculation based on the density and viscosity of a given fuel. The formula is rather complex but in general, the higher the CCAI, the poorer the ignition quality of the fuel is considered to be. Once the CCAI goes above 860, it is an indication that some combustion problems may occur.
Calculated Ignition Index, an index of the ignition quality of fuel oil; Caldera International, Inc., a software company between 2001 and 2002; Centro Intelligence Interforze, an Italian intelligence agency; Chaîne d'Information Internationale, former name of TV station France 24; Chartered Insurance Institute
C. Calculated Carbon Aromaticity Index; Calculated Ignition Index; Cantera (software) Chapman–Jouguet condition; Chemical looping combustion; Chemical WorkBench
The Wobbe index is expressed in MJ/Nm³ (where 'Nm³' indicates'm³ in Normal conditions), or sometimes in BTU/scf.In the case of natural gas (molar mass 17 g/mol), the typical heating value is around 39 MJ/Nm³ (1,050 BTU/scf) and the specific gravity is approximately 0.59, giving a typical Wobbe index of 51 MJ/Nm³ (1,367 BTU/scf).
The heating value of a fuel can be calculated with the results of ultimate analysis of fuel. From analysis, percentages of the combustibles in the fuel (carbon, hydrogen, sulfur) are known. Since the heat of combustion of these elements is known, the heating value can be calculated using Dulong's Formula:
The data is used to calculate air density and determine the engine's air mass flow rate, which in turn determines the required fuel metering for optimum combustion (see stoichiometry) and influence the advance or retard of ignition timing. A fuel-injected engine may alternatively use a mass airflow sensor (MAF sensor) to detect the intake airflow.
To calculate the actual efficiency of an engine requires the energy density of the fuel being used. Different fuels have different energy densities defined by the fuel's heating value. The lower heating value (LHV) is used for internal-combustion-engine-efficiency calculations because the heat at temperatures below 150 °C (300 °F) cannot be ...