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

Noga M., Sendyka B.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2014

Vol. 62, nr 2

349--355

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.

New design of the five-stroke SI engine

Noga M., Sendyka B.

Journal of KONES

2013

Vol. 20, No. 1

239--246

The paper describes design of the five-stroke engine developed in the Chair of Combustion Engines at Cracow University of Technology. The idea of five-stroke engine, in which the expansion ratio is significantly greater than the compression ratio has been presented by the Belgian engineer Gerhard Schmitz. The prototype of such an engine was made by Ilmor Engineering. Engine developers have released results of preliminary research, but there is no detailed information on the toxic exhaust emissions. For this reason, at Cracow University of Technology the research was undertaken to determine the impact of implementing the five-stroke cycle into the engine with spark ignition to reduce toxic emissions and increase total efficiency. To achieve this goal, the test engine was built, which is based on a concept similar to the idea of Gerhard Schmitz, with the difference that it has not been designed from the ground up, and it is based on an existing four-cylinder four-stroke engine. In comparison with the original solution, the engine built in Cracow has a completely different design of timing system, four valves per cylinder and petrol direct injection. This paper presents a detailed description of the engine design and the results of its preliminary research. The results of the tests of the five-stroke engine confirm an increase of specific torque and power (related to unit of engine displacement) and improve of total efficiency within a certain range of the engine map.