IMPROVEMENT OF THE DESIGN OF THE CYLINDER-PISTON GROUP OF COMPRESSOR MACHINES OF THE FOOD INDUSTRY

Abstract

The main directions of energy efficiency increase of air supply systems in production premises of food enterprises as well as of improvement of the most widespread reciprocating compressors are considered in the article. It is shown that the reduction of the load is accompanied by a progressive decrease in the mechanical coefficient of performance, and when it decreases sharper the lower the level of mechanical coefficient of performance at full load. A method for assessing the reliability of compressors operation considering the coefficient of performance in the production conditions of food enterprises, based on a progressive service strategy according to the real technical condition of the cylinder-piston group is developed. It is proved that the friction losses between the piston skirt and the cylinder cartridge case are an important way to reduce mechanical losses and increase efficiency. A slight reduction in mechanical losses leads to significant savings in energy consumption. The relative value of mechanical coefficient of performance depending on the load is calculated. The distribution of components of mechanical losses by parts and units of the compressor is shown. The influence of load on the increase of mechanical coefficient of performance while reducing mechanical losses by 10%, at full load and initial level of 0.8 mechanical coefficient of performance is shown. Reduction of mechanical losses by 10% causes an increase in mechanical coefficient of performance by 2%, at low load mechanical coefficient of performance increases by 7–8%. Therefore, measures even with a relatively small reduction in mechanical losses give a tangible effect in increasing the mechanical coefficient of performance and, consequently, the energy efficiency of the compressor. This effect is enhanced as the load decreases during operation of the compressor in the area of modes inherent in operation. It is determined that the tribo conjugation “piston – cylinder” accounts for up to 22.4% of all mechanical losses of a modern compressor. The stages of piston skirt formation are traced. It is proposed to use a symmetrical single-support piston, in which the oval cross-section of the skirt consists of upper and lower parts with different profiles. In the upper part, the larger and smaller diameters of the ovals increase evenly in the direction from the compression chamber, and in the lower part, the smaller diameter of the oval increases, and the larger one remains constant. As a result, trapezoidal shape contact surfaces are formed on the skirt. Due to the greater width of the contact surfaces, wear resistance increases and noise level decrease.