Experimental investigation of supersonic boundary-layer tripping with a spanwise pulsed spark discharge array

In this paper, a pulsed spark discharge plasma actuator array is deployed to control laminar–turbulent transition in a Mach 3.0 flat-plate boundary layer, and the subtle flow structures are visualized by nanoparticle planar laser scattering (NPLS) technique. Results show that the onset location of turbulence can be brought upstream by plasma actuation, corresponding to forced boundary-layer transition. Hairpin vortex packets evolved from the thermal bulbs play a vital role in the breakdown of laminar flow. With the help of a machine learning tool, all the relevant structures induced by plasma actuation are extracted from NPLS images, and a conceptual model of the hairpin vortex generation is proposed, including three stages: production and lift-up of the high-vorticity region, formation of the $\varLambda$ vortex and evolution of the hairpin vortex.

Platinum Based Nanoparticles Produced by a Pulsed Spark Discharge as a Promising Material for Gas Sensors

We have applied spark ablation technology for producing nanoparticles from platinum ingots (purity of 99.97 wt. %) as a feed material by using air as a carrier gas. A maximum production rate of about 400 mg/h was achieved with an energy per pulse of 0.5 J and a pulse repetition rate of 250 Hz. The synthesized nanomaterial, composed of an amorphous platinum oxide PtO (83 wt. %) and a crystalline metallic platinum (17 wt. %), was used for formulating functional colloidal ink. Annealing of the deposited ink at 750 °C resulted in the formation of a polycrystalline material comprising 99.7 wt. % of platinum. To demonstrate the possibility of application of the formulated ink in printed electronics, we have patterned conductive lines and microheaters on alumina substrates and 20 μm thick low-temperature co-fired ceramic (LTCC) membranes with the use of aerosol jet printing technology. The power consumption of microheaters fabricated on LTCC membranes was found to be about 140 mW at a temperature of the hot part of 500 °C, thus allowing one to consider these structures as promising micro-hotplates for metal oxide semiconductor (MOS) gas sensors. The catalytic activity of the synthesized nanoparticles was demonstrated by measuring the resistance transients of the non-sintered microheaters upon exposure to 2500 ppm of hydrogen.

Сравнение энергетической эффективности воспламенения топливной смеси искровым и стримерным разрядами

An increase in fuel efficiency and efficiency of combustion processes in power plants is discussed based on the data of physical and computational experiments. Two systems for ignition of a fuel mixture are considered, one of which uses a multi-point pulsed spark discharge, and the other uses a multipoint streamer discharge. A comparative assessment of the energy efficiency of each approach to the ignition of the air/fuel mixture is carried out, and conclusions are drawn about their effectiveness and prospects for use.