**4. Inclined effects on dynamic**

#### **4.1 PIV measurements on burners with inclined jets**

The mean velocity fields carried out by PIV in non-reacting flow are represented on **Figure 2**. From initial state where ϴ = 0° to inclined state where ϴ = 30°, the dynamic field changes with the change of flow structure. The jets fusion point

becomes closer the burner by increasing of the slope of jets. The interaction of jets starts at about 15 mm for ϴ = 0°, at z = 25 mm for ϴ = 30°.

#### **4.2 Velocity distribution and current lines**

**Figure 3** shows the distribution of velocity and the current lines in the combustion chamber near the burner with different inclined jets of oxygen. In the part separating the different jets (dark blue), velocity is negative because of the recirculation of the jets. The existence of two zones of recirculation is observed with different directions of rotation, which explains the appearance of the negative velocity. It is noted on the one hand that the recirculation zone decreases with the increase of Ө from 0 to 20°. This is very remarkable near the jet of oxygen. On the other hand, it can be observed that the recirculation zones appear outside the jet of air (see the lines of currents). The perturbation of velocity distribution increases with the increase of Ө. This perturbation is accompanied by an acceleration of the combination of different jets and consequently a faster combustion reaction, which explains the increase in velocity with the increase of Ө.

#### **4.3 Temperature distribution**

The distributions of the temperature in the combustion chamber with different inclined jets are represented in **Figure 4**. It is clear here that the flame exists in the mixing zone of methane and oxygen, which represents the reaction zone. This zone is modified with the variation of the angle Ө. If we assume that the length of the flame is defined by the red color of the flame distribution, we can conclude that the length of the flame decreases with the increase of the angle Ө from 0.44 m for an inclination of 0° to 0.29 m for an inclination of 20° of the jet of oxygen.

**Figure 5** represents the evolution of the axial temperature at y = 0 mm with different angles of injection Ө of the oxygen jets. Firstly, it is observed that the

temperature increases by moving away from the burner to a maximum value and then begins to decrease. For example for Ө = 0° the temperature increases from 300 K near the burner up to 3500 K at a height of 380 mm. This zone of increase presents the mixing zone of the reactants methane/oxygen. The second zone is the reaction zone where the temperature reaches its maximum. The third zone is where the temperature gradually decreases and which presents the plume of the flame. The second interpretation is that the flame reaches its maximum faster while the angle of injection Ө increases. Indeed, the temperature reaches its maximum at a height of 390 mm for Ө = 0° by contrast, it reaches its maximum at 260 mm for Ө = 30°. This interpretation leads to conclude that the length of the flame decreases with the increase in the angle of the oxygen jets. This result is in good agreement with the result of Boushaki [22], which showed that the average flame length

*Axial distribution profiles of temperature at y = 0 mm with variation of the angle Ө.*

**Figure 4.**

**Figure 5.**

**23**

*Temperature distribution in the combustion chamber.*

*A New Combustion Method in a Burner with Three Separate Jets*

*DOI: http://dx.doi.org/10.5772/intechopen.90571*

**Figure 3.** *Velocity distribution and current lines in the combustion chamber.*

*A New Combustion Method in a Burner with Three Separate Jets DOI: http://dx.doi.org/10.5772/intechopen.90571*

becomes closer the burner by increasing of the slope of jets. The interaction of jets

**Figure 3** shows the distribution of velocity and the current lines in the combustion chamber near the burner with different inclined jets of oxygen. In the part separating the different jets (dark blue), velocity is negative because of the

recirculation of the jets. The existence of two zones of recirculation is observed with different directions of rotation, which explains the appearance of the negative velocity. It is noted on the one hand that the recirculation zone decreases with the increase of Ө from 0 to 20°. This is very remarkable near the jet of oxygen. On the other hand, it can be observed that the recirculation zones appear outside the jet of air (see the lines of currents). The perturbation of velocity distribution increases with the increase of Ө. This perturbation is accompanied by an acceleration of the combination of different jets and consequently a faster combustion reaction, which

The distributions of the temperature in the combustion chamber with different inclined jets are represented in **Figure 4**. It is clear here that the flame exists in the mixing zone of methane and oxygen, which represents the reaction zone. This zone is modified with the variation of the angle Ө. If we assume that the length of the flame is defined by the red color of the flame distribution, we can conclude that the length of the flame decreases with the increase of the angle Ө from 0.44 m for an

**Figure 5** represents the evolution of the axial temperature at y = 0 mm with different angles of injection Ө of the oxygen jets. Firstly, it is observed that the

inclination of 0° to 0.29 m for an inclination of 20° of the jet of oxygen.

starts at about 15 mm for ϴ = 0°, at z = 25 mm for ϴ = 30°.

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

explains the increase in velocity with the increase of Ө.

**4.3 Temperature distribution**

**Figure 3.**

**22**

*Velocity distribution and current lines in the combustion chamber.*

**4.2 Velocity distribution and current lines**

**Figure 4.** *Temperature distribution in the combustion chamber.*

**Figure 5.** *Axial distribution profiles of temperature at y = 0 mm with variation of the angle Ө.*

temperature increases by moving away from the burner to a maximum value and then begins to decrease. For example for Ө = 0° the temperature increases from 300 K near the burner up to 3500 K at a height of 380 mm. This zone of increase presents the mixing zone of the reactants methane/oxygen. The second zone is the reaction zone where the temperature reaches its maximum. The third zone is where the temperature gradually decreases and which presents the plume of the flame. The second interpretation is that the flame reaches its maximum faster while the angle of injection Ө increases. Indeed, the temperature reaches its maximum at a height of 390 mm for Ө = 0° by contrast, it reaches its maximum at 260 mm for Ө = 30°. This interpretation leads to conclude that the length of the flame decreases with the increase in the angle of the oxygen jets. This result is in good agreement with the result of Boushaki [22], which showed that the average flame length

decreases when the angle of oxygen jets increases such that its value is about 500 mm for Ө = 0° and decreases until 220 mm for Ө = 30°.

## **5. Equivalence effects on dynamic**

#### **5.1 Radial profiles of longitudinal velocity and turbulence intensity**

The radial profiles of the mean longitudinal velocity (U) at different section (x/D = 1.66, x/D = 8.33 and x/D = 16.66) and for three equivalence ratios are represented in **Figure 6**. A classical behavior of the multiple jets is found, one notices that the velocity profile presents maxima and minima corresponding to the three jets. In the initial zone (near the burner) each jet follows its own evolution, further downstream these velocity extremes begin to disappear to form a single maximum located in the middle of the inner mixing layer.

Near the burner (x/D = 1.66) and for the three values of richness (Ф = 1, Ф = 0.8 and Ф = 0.7), we note that the velocity remains constant at the level of the central jet and it increases at the level of the lateral jet (jet of oxygen) with the decrease of the wealth. It should be noted that for Ф = 1 and Ф = 0.7 the mean longitudinal velocities are equal to 27 m/s and 38.57 m/s, mean velocity show an increase of 30%. In the case x/D = 16.66, the velocity profiles are slightly flattened, more open which improves the mixing of the reagents.

The influence of the equivalence ratio on the longitudinal velocity U is significant less. From an aerodynamics point of view, the decrease of equivalence ratio

modifies the longitudinal velocity of flow near to the burner but keep the flow

to the equivalence ratio and on sections different, x/D = 1.66, 8.33 and 16.66. In the case x/D = 1.66 we see two peaks of fluctuations in u<sup>0</sup> 'of the order of 7 m/s, one at the center corresponding to the mixing layer of the central jet and one from the central jet corresponding to the mixture layer of side jet. These peaks of fluctuations fade along the flow with decreasing longitudinal velocity as the jets interpenetrate.

The distribution of the temperature in sections different inside the combustion chamber, is shown in **Figure 8**. In the near of the burner, the temperature present one peak with maximum value equal to 3000°C. For a richness equal to 1 (Ф = 1) the maximum temperature of the adiabatic flame is T = 3000 K and for a richness 0.7 the maximum temperature equals approximately T = 3300 K. Therefore, the peaks represent the zone of the reaction between the fuel and oxidant after mixing and the region between the peaks represents the area of the fuel which is not yet burned and the reaction takes place at the interface of jets between fuel and oxidant. At x/D = 8.33 and for three equivalence ratio the peak temperature is observed equal to 3200°C and the temperature profile keep constant. Far from the burner when the richness decreases, an increase in the temperature in the flame zone is observed from 3000 to 3500°C which makes it possible to improve the heat transfers and

/U, on function

**Figure 7** shows, the radial profiles of the turbulence intensity, u<sup>0</sup>

velocity behavior in the combination zone.

*Turbulence intensity at different positions from the burner.*

*A New Combustion Method in a Burner with Three Separate Jets*

*DOI: http://dx.doi.org/10.5772/intechopen.90571*

**Figure 7.**

**25**

**5.2 Radial profiles of temperature**

makes it possible to have a better thermal efficiency.

**Figure 6.** *Radial profiles of longitudinal velocity at different positions from the burner.*

*A New Combustion Method in a Burner with Three Separate Jets DOI: http://dx.doi.org/10.5772/intechopen.90571*

decreases when the angle of oxygen jets increases such that its value is about

**5.1 Radial profiles of longitudinal velocity and turbulence intensity**

The radial profiles of the mean longitudinal velocity (U) at different section (x/D = 1.66, x/D = 8.33 and x/D = 16.66) and for three equivalence ratios are represented in **Figure 6**. A classical behavior of the multiple jets is found, one notices that the velocity profile presents maxima and minima corresponding to the three jets. In the initial zone (near the burner) each jet follows its own evolution, further downstream these velocity extremes begin to disappear to form a single

Near the burner (x/D = 1.66) and for the three values of richness (Ф = 1, Ф = 0.8 and Ф = 0.7), we note that the velocity remains constant at the level of the central jet and it increases at the level of the lateral jet (jet of oxygen) with the decrease of the wealth. It should be noted that for Ф = 1 and Ф = 0.7 the mean longitudinal velocities are equal to 27 m/s and 38.57 m/s, mean velocity show an increase of 30%. In the case x/D = 16.66, the velocity profiles are slightly flattened, more open which

The influence of the equivalence ratio on the longitudinal velocity U is significant less. From an aerodynamics point of view, the decrease of equivalence ratio

500 mm for Ө = 0° and decreases until 220 mm for Ө = 30°.

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

maximum located in the middle of the inner mixing layer.

*Radial profiles of longitudinal velocity at different positions from the burner.*

**5. Equivalence effects on dynamic**

improves the mixing of the reagents.

**Figure 6.**

**24**

**Figure 7.** *Turbulence intensity at different positions from the burner.*

modifies the longitudinal velocity of flow near to the burner but keep the flow velocity behavior in the combination zone.

**Figure 7** shows, the radial profiles of the turbulence intensity, u<sup>0</sup> /U, on function to the equivalence ratio and on sections different, x/D = 1.66, 8.33 and 16.66. In the case x/D = 1.66 we see two peaks of fluctuations in u<sup>0</sup> 'of the order of 7 m/s, one at the center corresponding to the mixing layer of the central jet and one from the central jet corresponding to the mixture layer of side jet. These peaks of fluctuations fade along the flow with decreasing longitudinal velocity as the jets interpenetrate.

### **5.2 Radial profiles of temperature**

The distribution of the temperature in sections different inside the combustion chamber, is shown in **Figure 8**. In the near of the burner, the temperature present one peak with maximum value equal to 3000°C. For a richness equal to 1 (Ф = 1) the maximum temperature of the adiabatic flame is T = 3000 K and for a richness 0.7 the maximum temperature equals approximately T = 3300 K. Therefore, the peaks represent the zone of the reaction between the fuel and oxidant after mixing and the region between the peaks represents the area of the fuel which is not yet burned and the reaction takes place at the interface of jets between fuel and oxidant. At x/D = 8.33 and for three equivalence ratio the peak temperature is observed equal to 3200°C and the temperature profile keep constant. Far from the burner when the richness decreases, an increase in the temperature in the flame zone is observed from 3000 to 3500°C which makes it possible to improve the heat transfers and makes it possible to have a better thermal efficiency.

**Figure 8.** *Radial profiles of temperature at different positions from the burner.*
