Direct ignition of a gas turbine combustor using blast furnace gas fuel has become a critical issue at present. As an alternative technology of traditional spark plug ignition, plasma-assisted ignition has excellent performance in the gas turbine combustor. In this paper, the ignition system is designed to conduct a direct ignition experiment using the plasma and spark plug igniter. Then, the plasma jet characteristics, ignition limit, and flame propagation of the blast furnace gas combustor are analyzed. The results show that, using blast furnace gas fuel in the gas turbine combustor, the direct ignition of spark plug igniter fails and direct ignition of the plasma igniter succeeds. The jet from the plasma igniter is conical with a length of 30 mm and a diameter of 8 mm, which contains various active species (O、, O*、, O+、, O2+、, N2*, and, N2+). With the increase of air flow rate in the combustor, the equivalence ratio of plasma ignition limit increases from 0.7 to 0.83, and the time required for successful ignition increases from 860 ms to 4300 ms. Meanwhile, the flame propagates from a unidirectional mode to a bidirectional mode in the combustor. The laminar flame characteristics and ignition delay time of BFG/air mixtures were investigated by CHEMKIN package using the Gri-Mech 3.0 model. The active species in the plasma jet can shorten the ignition delay time from 1E-4s to 1E-5s and improve the laminar burning velocities from 7.58 cm/s to 10.90 cm/s. A large-scale initial flame kernel with concentrated energy is formed rapidly so that the flame can successfully propagate to the recirculation zone and burn stably. Finally, the blast furnace gas fuel was successfully ignited directly by the plasma igniter.

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With the development of high performance gas turbine engines, the temperature before turbine is rising and it presents a serious challenge to existing thermal management. It is very attractive to use fuel as the cooling medium for gas turbine engines. For this purpose, the effects of fuel temperature on combustion characteristics are urgently needed to be understood. In this work, the characteristics of lean direct injection (LDI) combustor is simulated by changing the physical properties of fuel with different temperatures. The predictions of gas phase and droplet velocity, droplet diameter are compared well with the experiment data. The numerical results show that as fuel temperature rises, the droplet evaporation rate and mixing efficiency of fuel and air in non-reacting case is improved significantly, the spray angle, concentration and distribution profile of fuel in reacting case are enlarged as well. When fuel temperature is raised from 350K to 550K, the peak value of droplet evaporation rate at the vicinity of nozzle is increased by 26.7 times, the uniformity index downstream of the primary recirculation zone (PRZ) is increased by 2.57%, the axial length and maximum negative axial velocity of PRZ are reduced by 13% and 21%. The average temperature and NO emission at combustor outlet are increased by 1.99% and 48.15%, the mass fraction of CO is decreased by 5.45%. Besides, the number, diameter, and distribution space of droplets are decreased sharply. The formation of premixed flame and propagation of high-temperature region are promoted, the flame front is changed from a conical shape to a recessed shape. The combustion efficiency can be improved by increasing fuel temperature. The present study is expected to provide insightful information for understanding characteristics of LDI combustor with elevated fuel temperatures.

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The performance of the ignition device has an impressive impact on the working range and reliability of gas turbines. In the extreme conditions and with low pollutant emissions, gas turbines advancing higher requirements for the better performance of the ignition device. Due to its exceptional advantages, plasma ignition technology has become a research hotspot for all the scholars around the globe. The plasma ignition device ignites by the plasma jet with high-temperature and abundant active species, which has the advantages of large ignition energy, concentrated energy and strong penetration of the plasma jet. In the current research work, experimental research work is carried out on the plasma ignition using the plasma jet. The voltage and current features of plasma power supply are measured by a voltage probe and a current probe. The developed process of plasma jet generation is captured by a high-speed camera. The characteristics of plasma jet morphology and the law of the influence of the variable electrode gap (1.5 mm-3.5 mm) on the features of the plasma jet morphology are investigated. The experimental results demonstrate that during plasma ignition the discharge voltage and the current have a maximum peak-to-peak value of 11.67kV and 70A. The maximum reverse voltage and the reverse current are 2000V and 15A during the discharge and breakdown. The plasma jet produced active species along with a cone-shaped high-temperature during the air breakdown. The structure of the plasma jet can be divided into two portions, central high-temperature kernel (HTK) and peripheral halo gas (PHG) by gray processing of high-speed camera pictures. Different discharge electrode gap is leading to change the size of the plasma jet high-temperature kernel and the peripheral halo gas. If the gap of the discharge electrode is increased, then the area of the high-temperature kernel is also increased.