Combustion Characteristic Analysis

Abstract

In-cylinder pressure is directly related to the combustion process in reciprocating engines. Thus, the cylinder pressure measurement and its analysis can provide a large amount of information that can be utilized for further development, optimization, and tuning of engines. Combustion parameters can be quantified using thermodynamic analysis of cylinder pressure data. Presently, online estimation of combustion parameters is required for closed-loop control of the combustion process in reciprocating engines. Methods for the burn rate and heat release rate analysis are discussed in this chapter for offline and real-time estimation. Various heat release rate estimation models and sources of error in the calculation of heat release are summarized. For accurate computation of heat release, tuning of measurement parameters is required. Different methods for estimation of various combustion parameters such as the start of combustion (SOC), end of combustion (EOC), combustion duration, etc. are discussed. The SOC is an important parameter to assess ignition delay in diffusion-controlled combustion concepts, flame kernel growth in spark-ignited concepts, or success of combustion initiation in homogeneous charge compression ignition (HCCI) concepts. Different techniques for detecting the SOC and EOC for online and offline applications are described. Thermal stratification of the unburned charge before ignition plays a significant role in governing the heat release rates, particularly in HCCI engine. Understanding the conditions affecting thermal stratification is essential for actively managing HCCI burn rates and expanding its operating range. Recently developed thermal stratification analysis applied to calculate the unburned temperature distribution before ignition is also discussed in this chapter.