XIII Международная студенческая научная конференция Студенческий научный форум - 2021

Saving fuel resources and preserving the environment are priority areas for the development of the global engine industry. Since the introduction of the EURO standards, the requirements for CO2 and CH emissions have significantly increased, and compliance is achieved by improving old engine systems and creating new ones.

Indicators of exhaust gas toxicity and fuel efficiency of the engine are largely determined by the quality of mixing and combustion. The most problematic are the following modes of engine operation: partial load and idle, where the intensity of mixing processes is insufficient. Therefore, an important task in the development and improvement of engines is to improve the filling of the cylinder with a fresh charge and ensure the necessary quality of mixing. The development of piston engines has reached a high level, and improving any indicator by even a fraction of a percent is a difficult task.

One of the ways to improve the quality of mixing in diesel engines is the use of swirling the air flow in order to increase the intensity of mixing.

It is known that with an increase in the intensity of the vortex flow in the cylinder, the quality of mixture formation and combustion in diesel engines increases. But overly intense swirling flow at the inlet can significantly reduce the volumetric efficiency of the engine at peak power, to increase the heat losses in the combustion process to increase the thickness of the wall layer in the combustion chamber and increased CO2 emissions and CH in exhaust gases, so as to ensure maximum filling of the cylinder with minimum air pumping loss. It follows from this that for different engine operating modes, the most suitable intensity of the air flow swirl at the inlet must be provided, and this is possible only when using eddy control devices.

Creating a vortex flow motion in the cylinder of a piston engine is carried out in three ways.

The first method is implemented by supplying a fresh charge flow tangentially to the wall of the engine cylinder. A channel of this type is called tangential, the shape and location of channels of this type contribute to the movement of the flow along a helical trajectory.

At the same time, the β-angle of inclination of such a channel is less than that of a conventional one that performs one function. Also, the shape and size of these channels are limited by the design of the engine cylinder head. The air consumption coefficient for them is relatively less.

The second method is based on creating a vortex motion in the inlet channel before entering the cylinder. The inlet channel in this design is in the form of a spiral located around the rod of the intake valve. The twist of the flow is due to the shape of the channel itself. Also, it practically does not depend on the location relative to the axis of the cylinder. Depending on the design of the cylinder head and the layout of the engine, the screw channel can have either a lateral or vertical (with a falling flow) charge supply. When the entire cross-section is fully used, a higher air flow coefficient can be obtained, which leads to an increase in the filling coefficient.

The third method of swirling the flow involves creating a directed air flow by shading part of the passage section with a special insert called a screen, or screen. The screen itself can be pressed into the head or located on the valve itself. Now intake valves with a screen in serial engines are not used, since not only does the weight and cost of the valve increase, but also the hydraulic resistance increases and, accordingly, the filling coefficient decreases in the range from 5% to 10%, which is especially noticeable at high speeds of the crankshaft.

Thus, the vortex formation at the inlet has a positive effect on the performance of the engine at low and medium speed and load conditions.

References:

1. Dragomirov M. S. Investigation of the effect of air flow swirling in the intake channels on the performance of an automobile engine with distributed gasoline injection: abstract of the thesis of the Candidate of technical sciences. – Vladimir: Vladimir State University, 2005. – 25 c.

2. Kavtaradze R. Z. Theory of piston engines. Special Chapters, Moscow: Bauman Moscow State Technical University, 2008, 719 p.

3. Voshni G., Zeilinger K., Kavtaradze R. Z. Vertical movement of air in internal combustion engines / / Vestnik MGTU im. N. E. Bauman. Ser. Mashinostroenie. 1997. № 1. – 74 c.

4. Kavtaradze P. Z., Zelentsov A. A. Influence of the shape of intake channels on the effective and environmental performance of internal combustion engines// Bulletin of the Bauman Moscow State Technical University. Ser. Mashinostroenie. 2015. № 6. – 59 c.