Water Film Height Research Articles

The effect of water ingestion on an axial flow compressor performance

The aero-thermodynamic effects of water ingestion on an axial flow compressor performance are presented in this article. Under adverse weather conditions, gas turbine engine performance deteriorates and in extreme cases, this performance deterioration may result in flameout or shutdown of the engine, which means that serious incidents or possibly accidents may occur. When the water droplets enter into the engine they break up into smaller droplets which may bounce, coalesce or splash onto the compressor blades. They also form a liquid film whose motion is influenced by inertia forces, blade friction, aerodynamic drag and pressure gradient. The water liquid film has considerable effects on blade’s geometric characteristics. Apart from the change in its profile due to thickness increase, air shear force and water droplets momentum cause waves in water film’s surface introducing a kind of ‘roughness’ on blade’s surface. The current work focuses on the aero-thermodynamic effects. Its methodology is based on computational fluid dynamics, which is used to solve the flow field of the computational domain. The model consists of an extended inlet, an inlet guide vane, a rotor and a stator blade. Several cases with water ingestion are solved, varying the parameter of water mass and engine rotational speed, simulating adverse weather conditions. On the rotor blade, the water film height and speed are calculated at the equilibrium condition. This condition is achieved when the water mass which flows out of the blade surface equals with this which impacts on it. Taking into account the film thickness at each computational node of the blade surface, the blade’s geometry is changed. Furthermore, an equivalent roughness is introduced and the effects on compressor’s performance are calculated. It is found that deterioration is more pronounced in low rotational speed. For 4% water/air, compressor’s isentropic efficiency deteriorates 8.5% for idle speed and 1.6% for full speed. For the same water mass, mass flow capacity deteriorates 2.4% at idle speed while the change is small for full speed.

Experimental study on static flash evaporation of aqueous NaCl solution

Experimental study on static flash of aqueous NaCl solution was present. Initial waterfilm concentration and superheat ranged between 0 and 0.15 (mass fraction), between 1.7 and 53.9K respectively. Influence of factors, such as initial waterfilm concentration, initial waterfilm height and superheat on thermo-properties during flash, such as waterfilm temperature, non-equilibrium fraction (NEF), and volumetric heat transfer coefficient were analyzed and compared with that on flash of pure water. Results suggested that higher initial waterfilm concentration suppressed liquid–vapor phase change, reduced the rate of flash evaporating and weakened the intensity of boiling heat transfer. But the influences of superheat and initial waterfilm height on flash of aqueous NaCl solution were same as that on pure water. At last, NEF was fitted with relative error between −49.30% and 55.2%, upon which volumetric heat transfer coefficient could be calculated with relative error varying between −12.6% and 18.8%.

Study on steam-carrying effect in static flash evaporation

Study on steam-carrying effect in static flash of both pure water and aqueous NaCl solution was present. Properties, including steam-carrying ratio, waterfilm height drop and equilibrium concentration of waterfilm, were measured in experiments. Their dependences on separating height, initial waterfilm concentration and mean pressure difference were analyzed. Particularly, steam-carrying ratio was defined as the mass ratio of be-carried liquid and generated steam. Results suggested that this ratio increased with the decreasing of separating height or the rising of initial waterfilm concentration, and a peak value existed in its evolution versus mean pressure difference. At last, according to experimental results and basic principles a calculating model for steam-carrying effect in static flash was built.