Released in the combustion zone of the heat available to heat the products of combustion, for heating of combustible materials and the environment. The temperature, which is in the process of combustion of the heated products of combustion, called the combustion temperature. In the technique of fire and fact, distinguish theoretical, calorimetric, adiabatic and valid the combustion temperature (table.3.1).

Table 3.1. The conditions determining combustion temperature

The combustion temperature	The conditions determining
Q loss	a	Accounting for dissociation of the PG
Theoretical			Yes
Calorimetric			no
Adiabatic		11	no
Valid	10	11	no

In the General case, to calculate the combustion temperature, use the following dependency:

Q_PG = V_PG × ×T_G , where (3.6)

Q_PG – heat (the heat content) the products of combustion, kJ/kg;

V_PG – the volume of combustion products, m³/kg;

– average volumetric heat capacity of the mixture of combustion products in the temperature range from

T₀ to T_g, kJ/m³×To;

T_G – temperature of combustion, To.

When calculating the calorimetric temperature of combustion proceed from the, the heat losses to the environment are missing, and in this case, the lowest heat of combustion of combustible substances (Q_n) equal to the heat content of combustion products (Q_PG), ie. energy, required to heat combustion products from 0⁰With up to a theoretical combustion temperature.

In real conditions the combustion temperature depends not only on the composition of the combustible material, but also on the combustion conditions: dilution of combustion products by excess air (what is taken into account the excess air ratio a), the initial temperature of the air, the completeness of combustion of the original combustible material and the presence of heat loss (heat loss coefficient h).

Q_loss = Q_radiation + Q_{incomplete combustion} + Q_{dissociation PG} (3.7)

Depending on the kind of considered heat losses from the combustion zone is calculated, or that the combustion temperature.

The calculation of temperature of combustion carried out by the equation of energy balance:

Q_n × (1 – h) = V_PG^PR × With_g × (T_G – T₀) , where (3.8)

Q_n – heat, generated in the combustion reaction, kJ;

h – coefficient of heat loss; Q_n × (1 – h)= Q_PG;

V_PG^PR – volume of products of complete combustion with consideration of the excess air, m³;

With_g – average volumetric heat capacity of combustion products at constant pressure,

kJ/m³×To;

T_G – temperature of combustion, To;

T₀ – initial temperature, To.

From the equation (3.8) should, for calculation of temperature of combustion it is necessary to know the heat of combustion, volume and heat capacity of combustion products.

 

 

In a first approximation, the combustion temperature can be calculated directly from the equation (3.6), referring to, the average specific heat of gaseous products of combustion in the temperature range 1500 – 2500 K can be taken equal

= 1,75 kJ/m³×To. However, the heat capacity depends on temperature, and therefore for more accurate calculations of the specific heats take values from tables (app 3 and 4), and the count produced by the method of successive approximations (iteratively), every time determining the heat content of combustion products at selected temperatures.