XIII Международная студенческая научная конференция Студенческий научный форум - 2021

The presence of gas-dynamic phenomena in the engine intake tract has been known for a long time, and the desire of researchers and designers to use these processes to improve filling and increase the environmental friendliness of the engine has also been known for a long time.

The essence of gas dynamic boost (GDB) is to increase the filling of the engine cylinder by increasing the pressure and air flow rates during the opening of the intake valve. With individual intake pipes, due to variable pressures in the cylinder, forced and natural vibrations of the air column enclosed between the open intake valve and the intake system receiver occur. If these frequencies coincide, a resonance occurs in the system, which increases the filling of the cylinders. Due to inertial phenomena during the flow movement at the inlet, the cylinders are also recharged.

The general principles of designing intake systems in order to increase filling are reduced to determining the necessary lengths, volumes of the receiver and intake pipeline, to finding ways to reduce aerodynamic losses in the system, to selecting the optimal timing phases.

Increasing the filling ratio by GDB usually does not exceed 5-10%. Obtaining a higher filling is limited by the desire to maintain sufficiently high engine performance over the entire operating range of modes. Gas-dynamic supercharging provides an improvement in the operational efficiency of the car by 2-12%.

The main idea of gas dynamic boost control is to change the geometric parameters of the intake system depending on the engine operating mode. Usually, this change is carried out by a special mechanical or electronic-mechanical actuator based on signals from the engine shaft speed sensor or sensors of other operating parameters of the latter.

The main technical contradiction in the creation of controlled GDB systems is the difficulty of expanding the range of boost control without the overall dimensions of the devices. The primary tasks in resolving this contradiction are: rational use of the volume of the device due to the appropriate layout of the structure and compact arrangement of the device in the engine compartment of the car.

According to the classification of the system GDB are divided into unmanaged and controlled two-mode and three-mode with mechanical or electronic-mechanical control.

In order to ensure the effect in a wide range, a smooth or step-by-step adjustment of the length of the tuned path is used when switching from one speed mode to another. Step control by means of special valves or rotary dampers is considered more reliable and is successfully used in automobile engines of many foreign companies. A number of proposals for controlled gas dynamic boost systems contain the same idea-the separation of one pipeline into several channels and their inclusion in operation depending on the engine operating mode using rotary dampers controlled by actuators based on signals from the electronic control unit.

Despite the apparent simplicity of the technical solutions described above, it is not always possible to rationally assemble sufficiently long configured intake pipelines, since with a decrease in the speed of rotation, the length of the configured pipeline increases. Finally, the size of the pipeline is chosen by mathematical modeling and experimental refinement.

References:

A course of lectures on the discipline supercharging units for students of VlSU / A. A. Gavrilov, 2016.

Mashinostroenie enciklopediya / L. V. Grekhov, N. A. Ivashchenko, V. A. Markov, E. V. Aboltin, S. A. Afineevsky, F. B. Varchenko, D. I. Velsky, A. O. Borisov, G. V. Borisova, B. M. Bunakov, V. A. Wagner, A.V. Vasiliev, V. I. Volkov, A. I. Gaivoronsky, Yu.V. Galyshev, M. D. Garipov, L. N. Golubkov, A. N. Gotz, A. I. Yamanin, etc.; ed. K. V. Frolova, Moscow: OOO "Publishing House Mashinostroenie", 2013.