Statistical determination of correlation between pressure and crankshaft angle during indication of combustion engines (No. Gas pressure at the inversion crank angle P eĬentroid of the pressure distribution oCA: National Aeronautics and Space Administration NLLS:Ĭonstant pressure specific heat of the gas C VĬonstant volume specific heat of the gas D Indicated mean effective pressure IMEP error: Homogeneous charge compression ignition IMEP: This chapter presents the methods for determination of residual gas fraction, cylinder wall temperature, and air-fuel mass using in-cylinder pressure measurement. Thus, estimation of these parameters is necessary for detailed combustion analysis. Variations in residual gas fraction, wall temperature, and air-fuel mass significantly contribute to cyclic combustion variability in addition to performance and emission characteristics. The models for the estimation of blowby losses are also discussed. Blowby and gas flow through the cylinder-piston-ring crevices are phenomena that affect the in-cylinder pressure, the temperature, and the amount of charge during combustion, which affects the performance and exhaust emissions. This chapter presents different methods for compression ratio estimation based on in-cylinder pressure traces and evaluates for their accuracy and convergence speed. Displacement volume can be calculated within tight limits, but volume at TDC is difficult to determine because it consists of different crevices including the top-land region between piston, first ring and cylinder, head gasket, injectors and valve seats interstices, as well as the spark plug thread. Compression ratio depends on displacement volume and combustion chamber volume at TDC position. The different methods for TDC position determination by thermodynamic analysis of measured in-cylinder pressure are presented in this chapter. The TDC determination can be pursued by a dedicated TDC sensor (additional hardware) or by thermodynamic methods based on in-cylinder pressure measurement. Total cylinder volume determination is directly affected by the value of compression ratio used for calculations. The phasing of cylinder pressure and volume (by exact determination of TDC position) is of vital importance because it causes a large error in the calculation of IMEP and heat release.

Heat release rate calculation based on the first law of thermodynamics relies mainly on two parameters: (1) cylinder pressure and (2) cylinder volume as a function of crankshaft position. In-cylinder pressure-based heat release analysis is one of the most commonly used tools for engine combustion investigations.

Cylinder compression ratio calculator