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The purpose of the study is a comparative analysis of methods for graphic analytical determination of the characteristics of moist air in multistage compressors. Two methods are compared, which differ in the used I-d-diagrams: unified in terms of pressure and atmospheric. I-d-diagrams unified in terms of pressure differ from atmospheric ones by diagrams of saturated air relative humidity () only at various pressures. For multistage compressors, curves are plotted on unified I-d-diagrams at atmospheric pressure and compressed air pressure in intercoolers and receivers. It is assumed that the isobaric cooling of compressed air and condensation of its water vapor occurs in coolers and receivers at the final compression pressure in the previous compressor stages. The method, which uses I-d-diagrams unified by pressure, involves the diagram plotting of air compression and cooling on a grid of curves. An example of plotting such diagrams for a two-stage compressor with an intercooler and a receiver is given. A detailed description of the thermodynamic state of moist air in such a compressor is given. The nodal points of the processes in the compressor are plotted on a pressure-unified I-d-diagram according to the known values of moisture content and air temperature. The pressure and temperature at the end points of compression are calculated by the equations of the polytropic process at n = 1.26. The dew points in the cooler and receiver are graphically defined as the intersection of the curves for the final compression pressures with the corresponding straight lines for constant air moisture content in the compressor stages. The technique using atmospheric (barometric) I-d-diagrams is used in the absence of unified I-d-diagrams suitable for pressure. The essence of the developed technique is to determine the curves on the atmospheric I-d-diagrams, graphically coinciding with the curves A numerical example of the application of such a technique is given. The advantages and disadvantages of both methods are evaluated.

In engineering practice, when determining the characteristics of atmospheric air, I-d Ramzin diagrams are widely used, developed for a certain average barometric pressure. Direct transfer (without recalculation) of characteristics from atmospheric I-d diagrams to compressed air leads to serious errors. For compressed air, only individual and unified pressure I-d diagrams are applicable. Research objectives: creation of working (up to the level of algorithms) methods for constructing such I-d diagrams and establishing the boundaries of their applicability to air in a different state and at a different pressure. To construct I-d diagrams of compressed air, the atmospheric I-d diagram field is used. Humid air is assumed to be an ideal gas, the enthalpy of which does not depend on pressure. Isotherms and isoenthalps are copied from atmospheric I-d diagrams with their scale preserved. Also, the graph of the partial pressure of water vapor is copied, but its scale changes in proportion to the ratio of compressed air pressure to the accepted barometric pressure. Section 1 gives an algorithm for constructing pressure-individual I-d diagrams with a grid of curves of constant relative humidity. A method is given for determining at a given point such an I-d diagram of relative air humidity for a different pressure. This technique makes it possible to depict compressed air relative humidity curves on an atmospheric I-d diagram. For practical problems with the condensation of compressed air water vapor, it is convenient to use I-d diagrams unified by pressure, which are distinguished by the presence of a grid of saturated air relative humidity curves for a number of pressure values. Section 2 provides an algorithm for constructing unified I-d diagrams and gives a method for determining the relative humidity of unsaturated air at pressure P at a given point of such a diagram. The paper gives examples of the application of this technique.

Ижевский государственный технический университет имени М. Т. Калашникова, 426069, г. Ижевск, ул. Студенческая, 7 ________________________________________________________________________________ АННОТАЦИЯ. Рассматривается применение метода расчетного определения границ нестабильной детонации природного газа в газопоршневых установках для определения детонационной стойкости алканов C 1-C 4 (метан; этан; пропан и бутан). Детонация рассматривается как результат самовоспламенения газовой смеси при ее неизотермическом сжатии в цилиндре газопоршневой установки. Используется понятие верхнего и нижнего пределов температуры воспламенения углеводородных газов. Границы области нестабильной детонации определяются совместным решением уравнения Н.Н. Семенова, связывающего температуру и давление газа при самовоспламенении, с уравнением изменения температуры газа при политропном сжатии. В качестве источника опытных данных о величине детонационной степени сжатия индивидуального алкана, используется его октановое число по исследовательскому методу (ОЧИ). Идентификатором расчетных и опытных значений детонационной степени сжатия принимается верхний предел температуры самовоспламенения алкана. Используются данные ИХФ РАН по величине энергии активации задержки воспламенения алканов C 1-C 4 и объясняется немонотонный характер изменения опытных (по ОЧИ) значений детонационной степени сжатия при увеличении числа атомов углерода в молекуле алкана. Получено хорошее согласование расчетных и опытных (по ОЧИ) значений детонационной степени сжатия, позволяющее распространить разработанный авторами метод расчетного определения границ нестабильной детонации природного газа в газопоршневых установках на все алканы C 1-C 4 (метан, этан, пропан и бутан). КЛЮЧЕВЫЕ СЛОВА: попутный нефтяной газ, газопоршневая установка, детонация, температура самовоспламенения, энергия активации, степень сжатия, верификация, октановое число. Calculation method for determining detonation resistance of C 1-C 4 alkanes. Verification of the method by octan numbers Didenko V. N., Fakhraziev I. I., Martynov A. I.