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The objective of the paper is to study the influence of turbulence on the burning velocity of a lean gas-air mixture at high compression ratio ε = 14.5. In the present work turbulent combustion are examined in conditions very similar to those in the engine. Experiments are carried out in a rapid compression machine. The combustion area in a cylinder is divided into two parts: the main combustion chamber and very small open prechamber containing catalyst with developed surface. The temperature of the catalyst is controlled by means of special electronic device. Special inserts with orifices of different diameters are used to generate turbulence in the main combustion chamber. A piston pushes the mixture through the insert and creates swirl with superimposed different scale of turbulence in this chamber. Mutual influence of turbulence and catalytic ignition on combustion of a lean propane air mixture is extensively examined in special sets of experiments.

In the present work it is proposed to improve the efficiency of an Otto engine by development of a system with assisted catalytic ignition and combustion. The system is characterized by the use of a lean mixture in a swirling charge, substantial increase of the compression ratio, and application of a catalytic prechamber. For a long time, the combustion of lean mixtures has been one of the most important tendencies in development of gasoline engines. To be able to burn lean mixture at full load it is necessary to induce intense swirl in the combustion chamber and to increase compression ratio. One of the possible ways to burn lean homogeneous mixture is to use the combustion system made up of a main combustion chamber and prechamber. The latter is fed with the same lean homogenous mixture as the main combustion chamber, but it contains catalytic insert, kept at temperatures high enough, to secure catalytic reactions and torch ignition of the main charge.

Problems of ignition and flame development in combustion chambers of internal combustion engines supplied with lean, homogeneous, fuel-air mixture are of fundamental importance. One of the effective methods, which can improve flame initiation, is catalytic assistance of ignition and combustion. To be able to use catalysts efficiently in combustion processes in engines, it is necessary to know in detail their catalytic properties. The microcalorimetric method used before to determine characteristic temperatures of catalytic reactions was able to determine catalytic performance very roughly, because measurements were carried out at constant pressure and temperature of the analyzed mixtures. It was impossible, under such conditions, to evaluate precisely the influence of the catalysts on the progress of the combustion processes inside of the combustion chamber. In the present work properties of the catalyst are examined in conditions very similar to those in the engine.

Combustion systems with swirl chambers are applied in some spark ignition engines with homogeneous mixture. Such systems are developed to burn lean mixture with increased compression ratio far from the knock limit [1,2]. It was shown that these systems could be significantly improved by employing a prechamber with a catalyst [3,4]. An important part of the discussed combustion systems is cylindrical combustion chamber with a strong swirl. In this chamber, the flame propagates in the field of centrifugal forces increasing with a radius. In such conditions the flame surface takes the form of a cylinder. In the past, in a few experimental studies the behavior of flame propagation was investigated under the action of increased centrifugal forces, but the results were qualitative in nature [5, 6 and 7]. In the proposed paper an experimental study of flame propagating in a mixture with rigid-body rotation was carried out.

Lean burning in piston engines gives opportunity to achieve important enviromental and fuel economy objectives. Unfortunately, lean mixtures are not readily ignited and are characterized by poor flame propagation. Thus, techniques which enhance ignition, flame formation and its propagation must be applied, if lean combustion is to be reliably sustained. To overcome difficulties related to the lean burning, it has been proposed to equip the engine cylinders with prechambers, containing catalytic inserts, shaped in form of an open coil. The coils not only facilitate ignition but also generate turbulence, to intensify the combustion process in prechamber. A four-cylinder Diesel engine has been adapted for experiments aimed at confirmation of the effectiveness of the catalytic action on operation of the system.