CO 2 -diluted methane fuel is relevant to biogas combustion applications. Despite its poor heating value and low reactivity, which limit its practical applicability, biogas gains popularity as a renewable fuel.However, implementing it in combustion systems requires either modifying or replacing the existing burners. This study investigates the stability, temperature eld, and pollutant emissions of CH 4 /CO 2 /airpremixed ames red by a double-swirl burner. A CH 4 /air mixture of equivalence ratio, Φ out was used in the outer stream, while a CH 4 /CO 2 /air mixture was supplied to the inner stream. The CO 2 mole fraction, 𝒳 CO 2 , in the inner fuel blend varied from 0 to 0.4 for various inner stream equivalence ratios, Φ in . The stability diagram of these ames was mapped in terms of Φ in verses 𝒳 CO 2 for a xed Φ out . Based on the stability map, the in ame temperature eld was investigated for six ames.Increasing the %CO 2 in the biogas modi es the stability map by increasing the inner stream lean blow-off limits. However, increasing Φ out sustains the ame stability, while reducing the CO 2 increases the overall ame below off equivalence ratio. Flame size growth with increasing 𝒳 CO 2 requires a longer residence time for e cient combustion. The addition of CO 2 physically and chemically affects the thermal ame structure, and hence the pollutant emissions. In this burner, ultra-low NO X emission was reported, while an increase in the CO and UHC, with increasing 𝒳 CO 2 was observed. However, the results show that, for a given 𝒳 CO 2 , controlling Φ in and Φ out could reduce CO and UHC emissions.

A series of experiments were done on a vertical EV burner with a constant coflow air of 873 L /min in order to investigate the impact of fluidics insertion technique on the temperature field and flame structure. The flow rates of fuel (LPG/ Ar) and air were measured using calibrated rotameters. The different volume ratios of the fuel constituents were admitted via three solenoid valves at the entry section of each stream prior to mixing and monitored using a lab view program. The axial temperature profiles at different operating conditions were measured using a bare (type S) thermocouple. Flame images were obtained, before and after fluidics insertion using a high resolution digital camera. The experimental program aims at identifying and analyzing the changes in flame characteristics (flame length, axial profiles of mean gas temperature, NOx concentration and overall combustion efficiency) resulting from the insertion of fluidics while considering different proportions of the fuel constituents. The results obtained indicate the following: it was noticed that in most cases of pure LPG only, and other mixtures of argon the images shows increase in both the length and luminosity of the flame as a result of higher degrees of swirl due to the fluidics insertion while the temperature profiles of the different flames were changed. It was indicated that NOx trend was decreased by 50% while the combustion efficiency was improved by 2.5%.

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The fluidic oscillator shows very promising outcomes as an actuator in active flow control applications as it features several characteristics including no-moving parts, self-excitation, rigidity and reliability. The fluidic oscillator can be utilized in diverse applications including active-control of combustion and flow separation. The present work investigates the exit configuration influence on the flow dynamics of a small-scale double-feedback fluidic oscillator. Three configurations were modelled to examine the effects of the inclusion of a splitter inside the exit channel as well as the whole elimination of both the exit channel and splitter. Experimental results were obtained using particle image velocimetry (PIV) laser system with water as a working fluid and time-resolved pressure measurements using a hydrophone. Two-dimensional computational models based on Unsteady Reynolds-averaged Navier-Stokes (URANS) equations and shear stress transport (SST) were utilized considering the flow to be turbulent, incompressible, and isothermal. The results indicate that the exit configuration has no significant effects on the frequencies, while the jet deflection angle of the outflowing jet increases and the jet tends to be continuous when the splitter is removed. The splitter increases the outflow fluctuation amplitudes which would be suitable for diverse applications.

A spectroscopy and visual investigation for turbulent swirling flames formed by four-circumferential swirling turbojet EV in comparison with a two-circumferential swirling air entries configuration burner using hyper spectral camera. The special design of the EV-burner guarantees flame stabilization at the burner exit by a recirculation of hot gases and entrained fresh reactance mixture. A recirculation zone (vortex breakdown) can be generated when a sufficient strong swirling flow exist. The main parameter of combustion diagnostics based on optical devices is the flame itself, whose spectrum is closely related to the process state, as a fingerprint of the instantaneous operational condition, in terms of energetic yield, fuel consumption and pollutants emissions. The hyperspectral imaging technique in the aspect of flame analysis to give a complete description for the flame zones behavior and distribution of reactions through the whole flame. The spectral peaks for issued flames have been studied to give complete vision for the effect of changing the equivalence ratio and different burner arrangement four and two circumferential swirling entries.