## 2 Materials and Methods
### Methods
In the first stage, the content of CH, CO, CO\({}_{2}\), and O\({}_{2}\) in the exhaust gas of the vehicle was determined as a function of the crankshaft speed without ultrasonic exposure and with ultrasonic exposure at an ultrasound frequency of 25, 28, and 40 kHz. In the second phase of the experiment, the parameters of the smoke content of the gas were determined without exposure and with the influence of ultrasound, depending on the change in the crankshaft speed of the engine with the set value of the ultrasound frequency. Smokiness is a visible dispersion of liquid and (or) solid particles in the exhaust gas, formed as a result of incomplete combustion of fuel and evaporated oil in the engine cylinders, affecting the transmission of light. Smoke affects the light attenuation coefficient \(N(\%)\), which is recorded by the smoke meter. Repeated experiments were conducted 5 times. This article shows the average data for five experiments. Based on the results of the experimental tests on the composition of the exhaust gases, diagrams of the changes in oxygen (O2) and carbon dioxide content (CO2) as a function of the engine crankshaft speed and considering non-exposure and exposure to ultrasound at specific frequencies of 25, 28, and 40 kHz were drawn up (Figures 4 and 5). The content of the remaining gases was insignificant. Elevated temperature, humidity, and gas-chemical composition do not affect the operation of the ultrasound, as it is used even in hazardous industries for gas purification. Increasing the speed of gas movement and increasing the frequency of the crankshaft reduces the volume of gas from which the oxygen concentration is determined by the device. And, also, the operation of the engine is controlled by the ECU, which in turn controls the fuel-air mixture supplied to the combustion chamber in different modes. The diagrams obtained (Figures 4 and 5) show the effective effect of ultrasound on the change in composition and the degree of gas cleaning, i.e., at an engine speed in the range of 750 rpm to 950 rpm and at all ultrasonic frequencies of 25, 28, and 40 kHz, an increase in the oxygen content of the exhaust gases and a reduction in carbon dioxide were observed. However, at a crankshaft speed of 1250 rpm, an increase in gas composition was observed. This is because when the engine crankshaft speed is increased, more fuel is consumed, resulting in an immediate increase in carbon dioxide and a decrease in oxygen. It should be noted, however, that at the highest ultrasonic frequency of 40 kHz, the lowest indicators for CO2 and the highest indicators for O2 at 950 rpm were recorded, leading us to conclude that the higher the value of the ultrasonic frequency, the higher the degree of gas purification. Based on the results of the experimental studies to determine the indicators of smoke development, diagrams of the changes in the smoke development index were then prepared depending on the engine crankshaft speed and considering non-exposure and exposure to ultrasound at specific frequencies of 25, 28, and 40 kHz (Figures 6-8). Figure 5: Change in carbon dioxide content CO2 without exposure and with exposure to ultrasound (at ultrasound frequencies 25, 28, and 40 kHz). Figure 6: Indicators of gas smokiness depending on the change in engine crankshaft speed (ultrasound frequency of 25 kHz). Overall, the results of the experimental studies have shown the success of the experiments conducted, because according to the graphs (Figures 6-8), the indicators of smokiness of the gas after exposure to ultrasound have lower values than the indicators of smokiness of the gas that was not exposed to ultrasound. In general, smoke indicators decreased by about 20-40% after exposure to the gas with ultrasound. In general, the results of the experimental studies have shown the success of the experiments carried out, since, as, according to the graphs (Figures 6-8), the smoke values of the gas after exposure to ultrasound have lower values than the smoke values of the gas that was not exposed to ultrasound.