Thermodynamic basis for refi ned calculation of the operating cycle of a reciprocating internal combustion engine

Abstract

Introduction (problem statement and relevance). The notion of “charge coeffi cient” used only by the engine building specialists has a number of signifi cant disadvantages, since this coeffi cient characterizes not the charge as such, but only its deterioration. In particular, it is impossible to specify its limit value, at which the maximum engine power is achieved.
The purpose of the study is to search for a parameter alternative to the charge coeffi cient and quantitatively determining the charge degree of the total cylinder volume with the incoming charge. The parameter shall unambiguously estimate the charge reserves and the limit value one shall aim at in order to achieve the maximum engine power with no incoming charge losses as a result of scavenging.
Methodology and research methods. In order to solve the assigned task, thermodynamic analysis of gas exchange results was used, on the basis of the ratios of the components of the resulting air-fuel mixture.
Scientifi c novelty and results. The paper proves that the charge is unambiguously characterized by the basic technical notion of a proportion – a proportion of incoming charge σСЗ in the air-fuel mixture. Accordingly, the proportion of residual gases representing diff erence σr= 1 σСЗ allows estimating the degree of internal recirculation and, on the other hand, characterizes the charge reserves.
Practical signifi cance. The suggested approach allows taking into account the infl uence of the used fuel type (its molar weight), external recirculation and (variable) valve timing on the charge. Thus, it is possible to relate the charging up coeffi cient to the purifi cation coeffi cient as well as to decrease the number of independent variables when conducting thermal calculation of the operating cycle of the reciprocating internal combustion engine, which ultimately simplifi es its performance.