Heat transfer to impinging isothermal gas and flame jets

Erosion Prediction in Turbomachinery Resulting from Environmental Solid Particles

Publisher Summary Impinging liquid jets have been demonstrated to be an effective means of providing high heat or mass transfer rates in industrial transport processes. This chapter summarizes the available analytical and experimental work in the area with the objective of correlating the research findings. Significant progress has been made in understanding the fundamentals of heat, mass, and momentum transport in these systems. This chapter suggests that, there is considerable need for further research in liquid jet array applications, both in submerged and free-surface jet configurations. Cross-flow effects in these systems, which have been quite well characterized for submerged jets, have received only superficial treatment for free-surface jets. The physical phenomena are highly complex, requiring careful experimental investigation.

Single-Phase Liquid Jet Impingement Heat Transfer

Experimental analysis and modelling of particle-wall collisions

The distribution of the feature [high] in Shona verbs is a prototypical example of positional neutralisation accompanied by vowel harmony. In languages which exhibit positional neutralisation of vowel contrasts, one or more vowels (generally, the most marked members of the vowel inventory) may occur distinctively in only a small subset of the structural positions available in the language. Outside of these positions, the marked vowels may surface only if they harmonise with a similar vowel in the privileged position. For example, the mid vowels e and o in Shona verbs are contrastive only in root-initial syllables. These vowels may appear in subsequent syllables only when preceded by a mid vowel in root-initial position. A string of height-harmonic Shona vowels is therefore firmly anchored in the root-initial syllable, as shown in (1):

Positional faithfulness, positional neutralisation and Shona vowel harmony

Heat Transfer by a Square Array of Round Air Jets Impinging Perpendicular to a Flat Surface Including the Effect of Spent Air

This paper presents a review of erosion and deposition research in turbomachines and the associated degradation in engine performance caused by particulate matter ingestion Parameters affecting surface material losses as a result of erosion and development of experimental and analytical approaches to predict flowpath erosion and deposition are discussed Tests results that quantify the effects of temperature, impact particle composition, impact velocity and angle, and surface material composition are reviewed along with particle restitution data (ratios of rebound to impact velocities and angles) Development and application of models using these data to calculate surface erosion in turbomachinery are described These models predict particle trajectories in turbomachinery passages to determine impact rates, impact velocities, impact angles and uses the experimentally-obtained erosion data to calculate material losses Literature on the effects of erosion on turbomachine performance and life is surveyed Mechanisms of particle delivery and attachment upon arrival at turbomachine flowpath surfaces are also discussed along with experiential models that have been developed to predict surface deposit buildup Delivery to turbine surfaces can occur as a result of inertial flight, as for erosion, but also through transport mechanisms involving turbulence, Brownian diffusion, and thermophoresis The particle size range, where each of these mechanisms is dominant for delivery to surfaces, is described The history and experience of developing models that use these mechanisms to quantify particle delivery rates to turbine flow path surfaces is discussed, along with the use of sticking fraction data to determine the amount of material retained on the surfaces after delivery and the resulting deposit buildup rates Finally, factors that control whether extreme rates of deposition can occur in turbomachinery are described

Erosion and Deposition in Turbomachinery

This paper presents the results of a combined experimental and computational research program to investigate turbine vane and blade material surface deterioration caused by solid particle impacts. Tests are conducted in the erosion wind tunnel for coated and uncoated blade materials at various impact conditions. Surface roughness measurements obtained prior and subsequent to the erosion tests are used to characterize the change in roughness caused by erosion. Numerical simulations for the three-dimensional flow field and particle trajectories through a low-pressure gas turbine are employed to determine the particle impact conditions with stator vanes and rotor blades using experimentally based particle restitution models. Experimental results are presented for the measured blade material/coating erosion and surface roughness. The measurements indicate that both erosion and surface roughness increase with impact angle and particle size. Computational results are presented for the particle trajectories through the first stage of a low-pressure turbine of a high bypass turbofan engine. The trajectories indicate that the particles impact the vane pressure surface and the aft part of the suction surface. The impacts reduce the particle momentum through the stator but increase it through the rotor. Vane and blade surface erosion patterns are predicted based on the computed trajectories and the experimentally measured blade coating erosion characteristics.

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Widen Tabakoff

Papers

Erosion Prediction in Turbomachinery Resulting from Environmental Solid Particles

Heat Transfer by a Square Array of Round Air Jets Impinging Perpendicular to a Flat Surface Including the Effect of Spent Air

Erosion and Deposition in Turbomachinery

Turbine Blade Surface Deterioration by Erosion

Erosion study of different materials affected by coal ash particles