High Efficient gasification in a Low-tar biomass (LTB) gasifier by Coupling with Inclined Nozzle and Combustor for Tar Reduction

A novel design of low-tar biomass (LTB) gasifier with an inclined nozzle in the pyrolysis zone and a separate combustor installed inside the partial oxidation zone has been designed, developed and tested, while maintaining an extremely low tar in the producer gas. The design process was focused on a swirling flow created by an inclined nozzle which allows a good mixing between gasifying air and pyrolysis gases in the pyrolysis zone. A separate combustor which has large annular and reverse flow zones with the help of swirl flow. The resulted mixing gases has sucked inside in to the combustor and burning the mixture with the help of induced thermal cracking in the partial oxidation zone. At an equivalence ratio of 0.35, the gasifier had a thermal capacity at 23.8 kW and a maximum cold gas efficiency of 93.1%. Using wood chips with a moisture content of 9–34%, the LTB gasifier had generated a producer gas at 7.4-27.14 mg/Nm3 with a lower heating value of 4.57–5.11 MJ/Nm3. The resulted producer gas can be piped directly to the internal combustion engine or a gas turbine at small to medium scale power plant in remote rural off-grid areas.

Discrete Phase Modeling of the Powder Flow Dynamics and the Catchment Efficiency in Laser Directed Energy Deposition with Inclined Coaxial Nozzles

Laser Directed Energy Deposition (DED) is one of the most promising additive manufacturing processes for restoring high value components. The damaged components can have complex free-form shapes which necessitates depositions with an inclined nozzle, where, the gravity can adversely affect the powder flow dynamics and the powder catchment efficiency (PCE). PCE is defined as the fraction of the total mass flow rate entering the melt pool and a low PCE can render the process inviable. In this paper, the effect of nozzle inclination on the powder flow dynamics and resulting PCEs have been studied. It was found that the powder flow dynamics is altered significantly in an inclined nozzle and results in an asymmetric and skewed powder jet. This affects the powder focusing adversely and the PCE deteriorates rapidly with an increase in the inclination and falls below 20% at 75°. A discrete phase model has been developed to understand the powder flow dynamics at different inclinations and process conditions. The mass flow distribution asymmetry on the focal plane at various nozzle inclinations have been analyzed via the model. The model is able to predict PCEs at different nozzle inclinations with reasonable accuracy. It has been observed that carrier gas flow, particle size and laser diameter affect the PCE significantly and can be used to counter the enhanced powder loss at large nozzle inclinations. Process maps have been developed to identify the favorable, acceptable and low PCE regions for the selection of optimal DED parameters.

The Axial Decay and Radial Spread of a Supersonic Jet Exhausting into Air at Rest

SummaryThe distribution of total pressure, stagnation temperature and gas velocity is determined for the subsonic region of a supersonic jet emerging from a solid propellant rocket motor into air at rest. Measurements of Pitot pressures in the supersonic flow region have shown that the flow follows the axis of an inclined nozzle within the order of accuracy of the measurements. Nozzle cone angle, and probably the expansion ratio, affect the jet distribution significantly.