Combustion analysis and cycle-by-cycle variations in spark ignition engine combustion Part 1: An evaluation of combustion analysis routines by reference to model data

Abstract

This paper investigates a number of new approaches to mass fraction burned analysis for application to spark ignition engine combustion processes. The rationale for these new approaches is to retain the simplicity and computational efficiency of the technique of Rassweiler and Withrow, but to overcome some of the limitations inherent in the standard methods. The approaches investigated include the use of a two-zone model to determine information about the burned and unburned gas temperatures and the modification of the standard Rassweiler and Withrow expression to incorporate polytropic indices for compression and expansion.The investigation makes use of an engine simulation model, which was used to generate the pressure data. This technique provided a`known' burn rate against which to evaluate the methods investigated. Some experimental data taken from a Rover K4 optical access engine is also presented.The successful aspects of this investigation are the use of the Rassweiler and Withrow equation with different compression and expansion indices, and the application of this analysis to investigate crevice gas burn-up. What was found to be not successful was the use of a two-zone model for calculating gas temperatures. The results indicate that the model is, in general, not reliable for computing temperatures and this is due to the temperature gradient in the burnt zone and the disproportionately high rate of heat transfer from the mixture that burns first during combustion. The mass fraction burned calculations using this model were also found to be not as accurate as those based on simpler models. NOTATION m mass n polytropic index n c polytropic index for compression n e polytropic index for expansion n9 polytropic exponent for the unburned portion of the charge (determined from the compression P± V diagram) n0polytropic exponent for the burned portion of the charge (determined from the expansion P± V diagram) P pressure P t observed pressure during combustion at time t P tf observed pressure at end of combustion P ti observed pressure at ignition R gas constant T temperature V volume V t total volume of combustion chamber during combustion at time t V tf total volume of combustion chamber at end of combustion V ti total volume of combustion chamber at ignition V 0 t

Characterisation of flame development with ethanol, butanol, iso-octane, gasoline and methane in a direct-injection spark-ignition engine

“…Heat release analysis and calculation of Mass fraction Burned (MFB) was performed using methods based on [47,48], following the practice of earlier work published by authors on the same engine for consistency [38][39][40][41][42]. The uncertainties involved in acquiring and processing in-cylinder pressure data were carefully considered.…”

An Analysis of the Combustion Behavior of Ethanol, Butanol,Iso-Octane, Gasoline, and Methane in a Direct-Injection Spark-Ignition Research Engine

“…The CDM pulse from the crankshaft encoder was used via the ETU to provide the clock source for a LABVIEW-based data acquisition program. Heat release analysis of the in-cylinder traces and calculation of mass fraction burned (MFB) was performed using methods based on Ball et al (1998) and Stone and Green-Armytage (1987). The effects of numerical integration on the calculation of the indicated mean effective pressure (IMEP) from the in-cylinder pressure-volume diagram can be minimized, provided the crank angle resolution is smaller than 1 CA (Brunt and Emtage, 1996).…”

Insights into Stoichiometric and Lean Combustion Phenomena of Gasoline–Butanol, Gasoline–Ethanol, Iso-Octane–Butanol, and Iso-Octane–Ethanol Blends in an Optical Spark-Ignition Engine

“…Pressure data were post-processed to calculate the Indicated Mean Effective Pressure (IMEP), amplitude and timing of peak incylinder pressure, including mean values and Coefficients of Variation (COV=Mean/RMS). Heat release analysis and calculation of Mass Fraction Burned (MFB) was performed using methods based on Stone and GreenArmytage (1987) and Ball et al (1998) and followed practices of earlier work by the current authors for consistency Serras-Pereira et al, 2008. All uncertainties involved in acquiring and processing in-cylinder pressure data were carefully considered according to Brunt and Emtgae (1996).…”