Increase of efficiency of SI engine through the implementation of thermodynamic cycle with additional expansion

Abstract

Abstract. The paper presents the theoretical basis and practical implementation of the concept of a five-stroke cycle where an additional expansion of the working medium is achieved in a separate cylinder. The work, carried out at the Cracow University of Technology, constitutes a development of the idea of five-stroke engine. This paper proposes a new theoretical thermodynamic cycle that describes the processes occurring in a five-stroke engine. It has been taken into consideration that the expansion ratio of the engine is twice the compression ratio. At the next step an analysis of the thermodynamic cycle with particular emphasis on its thermal efficiency compared to efficiency of four-stroke engine has been shown. In the second part of the article selected research results of the five-stroke engine built based on the existing four-cylinder spark ignition engine have been presented. A comparison of the total efficiency obtained by the engine in the four-and five-stroke version has been provided. Similar comparisons for specific emission of the selected exhaust components have also been given.Key words: innovative five-stroke engine cycle, Carnot Cycle, Otto cycle, five-stroke engine, additional expansion, increase of thermal efficiency of the five-stroke engine cycle.

A comparison between Miller and five-stroke cycles for enabling deeply downsized, highly boosted, spark-ignition engines with ultra expansion

“…Since the engine was designed for the range extender application, the full load limit was defined as the point of drastic increases of fuel consumption with increasing torque, and a regular turbocharger could be employed. Noga et al [31,32] studied both theoretically and experimentally the similar concept to the five stroke cycle engines with the total expansion ratio twice than the compression ratio. They modified a four-cylinder four-stroke engine into a five stroke engine with remaining the outer two cylinders working with conventional four-stroke cycle and the inner two cylinders working only with expansion and exhausting strokes.…”

A three-way catalyst system for a five-stroke engine

“…The basic technical specifications of the engine with additional expansion of exhaust gases developed at Cracow University of Technology in its current configuration are shown in Table 1. The engine developed at Cracow University of Technology was the subject of several previous studies [34][35][36][37] and [39][40][41]. These works focused mainly on aspects related to the description of the design itself in which the engine was constructed on the basis of an existing four-stroke engine, issues of the thermodynamic description of processes occurring in it and the analysis of engine test results in the context of its thermal and mechanical efficiency indicated the mean effective pressure and the ratio of exhaust energy recovery in cylinders of additional expansion.…”

Selected Issues of the Indicating Measurements in a Spark Ignition Engine with an Additional Expansion Process

“…During the development of the engine with the additional expansion of exhaust gas, a thermodynamic cycle taking into account the specific characteristics of the tested engine was proposed [17]. Extensive simulation studies of a similar engine, but with a single-cylinder of additional expansion, was also carried out by Li et al at Shanghai Jiao Tong University [18,19].…”