Abstract: From an analyses of the composition of products of combustion of arbitrary hydrocarbon fuel CxHy with air (t≤1500℃，β≤1), author demonstrated that, the thermodynamic properties of products of combustion of arbitrary hydrocarbon fuel with air can computed in term of known thermodynamic properties of any two essential hydrocarbons with airy computing equations are presented. Some examples of using C and H2 as the essentical hydrocarbons to compute the thermodynamic properties of products of combustion of (CH2)n with air are given: From such calculations it is shown that, when isentropically expaned from 15000C to the same final temperature (temperature drops about 1500℃-1000℃), the properties (β= I ) of products based on fuel composition of (CH2)n deviate from the properties based on C and H2 by about 1-2 percent for enthalpy drop and by about 4~14 percent for pressure of final state, when isentropically expanded from 1500℃ initial state to the final state of the same pressure (pressure ratio about 1000-40), properties of products of (CH2)n deviate from the properties of products of C and H2 by about less than 1 percent for enthalpy drop and by about 1~4 precent for final temperature Under the above conditions, properties of products of arbitrary hydrocarbon fuel deviate form the properties of products of (CH2)n by values less than the above mentioned figures.

Key words: device parameters, excavating machinery, excavating performance, working device