Abstract
In order to improve combustion characteristic of swirl chamber diesel engine, a simulation model about a traditional cylindrical flat-bottom swirl chamber turbulent combustion diesel engine was established within the timeframe of the piston motion from the bottom dead centre (BDC) to the top dead centre (TDC) with the fluent dynamic mesh technique and flow field vector of gas in swirl chamber and cylinder; the pressure variation and temperature variation were obtained and a new type of swirl chamber structure was proposed. The results reveal that the piston will move from BDC; air in the cylinder is compressed into the swirl chamber by the piston to develop a swirl inside the chamber, with the ongoing of compression; the pressure and temperature are also rising gradually. Under this condition, the demand of diesel oil mixing and combusting will be better satisfied. Moreover, the new structure will no longer forma small fluid retention zone at the lower end outside the chamber and will be more beneficial to the mixing of fuel oil and air, which has presented a new idea and theoretical foundation for the design and optimization of swirl chamber structure and is thus of good significance of guiding in this regard.
Highlights
Swirl-chamber type diesel engine, especially the medium and low-power one, is manufactured in large volume and widely used in China
In the studies on swirl chamber, in other countries, Komatsu et al have conducted simulation analysis on the flow field in the chamber [10] and Montorsi et al and Okazaki et al have studied the law on change of flow field in the chamber and oil atomization with the crank angle [11, 12]; in China, Zhu et al have studied the influence of various interface channels on the flow field in the chamber taking the highspeed photography and numerical simulation method in succession [13, 14], Tang et al have simulated the influence of interface channels in various angles of inclination on the flow field in the chamber [15], and An has conducted simulation analysis on the compression and atomization processes in the chamber [16]
This paper studied the flow field characteristic in the swirl chamber of a certain type of swirl-chamber turbulent-combustion diesel engine with a fluid simulation software, presented the air flow status in the chamber and the change of gas velocity, pressure, and temperature in the swirl chamber and the combustor in the time frame of the piston’s motion from bottom dead centre (BDC) to top dead centre (TDC), and further proposed a new swirl structure
Summary
Swirl-chamber type diesel engine, especially the medium and low-power one, is manufactured in large volume and widely used in China. The diesel’s combustion process has been a key point of in-cylinder study all the time, while the formation and combustion of gas mixture and the structure of combustor are closely related to the motion of air therein [3]; a suitable swirling strength is available for effectively improving fuel evaporation, promoting the mixing progress of fuel and air [4,5,6], and improving the combusting condition inside the combustor. The recent years have witnessed people’s coming to realize that the air’s turbulent motion has played a critical role in the formation and combustion of gas mixture as well [7,8,9] and their progressive study on swirl-chamber type diesel engine. This paper studied the flow field characteristic in the swirl chamber of a certain type of swirl-chamber turbulent-combustion diesel engine with a fluid simulation software, presented the air flow status in the chamber and the change of gas velocity, pressure, and temperature in the swirl chamber and the combustor in the time frame of the piston’s motion from BDC to TDC, and further proposed a new swirl structure
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