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Abstract: Indirect combustion noise is believed to be a key component of turbofan engine core noise, but existing experimental data have not been able to definitively determine its importance. Instead, actuator disk theory (ADT) as developed by Cumpsty and Marble [The interaction of entropy fluctuations with turbine blade rows; a mechanism of turbojet noise, Proceedings of the Royal Society of London A 357 (1977) 323–344] is commonly used to estimate its contribution based on combustor exit conditions and changes in the mean flow across blade rows. The theory, which assumes planar propagation of acoustic, entropic, and vortical waves in the long wavelength limit, is assessed by comparing its predictions to those from two-dimensional compressible Euler calculations of idealized entropy disturbances interacting with a 1980s era NASA turbine stator. Both low-frequency planar waves of constant frequency and higher-frequency, localized entropy disturbances are considered, with the former being within ADT''s range of applicability and the latter outside of it. It is found that ADT performs well for the cut-on acoustic modes generated by the entropy-blade interaction but its accuracy suffers for the cut-off acoustic modes, which could impact indirect combustion noise predictions for turbines with closely spaced blade rows. [Copyright &y& Elsevier]

During the last decade, optical tweezers have been transformed by the combined availability of spatial light modulators and the speed of low-cost computing to drive them. Holographic optical tweezers can trap and move many objects simultaneously and their compatibility with other optical techniques, particularly microscopy, means that they are highly appropriate to lab-on-chip systems to enable optical manipulation, actuation and sensing. [ABSTRACT FROM AUTHOR]

The article offers information about the Rotork intelligent valve actuators which took center stage at the latest official opening of the new skills and maintenance training centre at the British Energy Heysham power station. The new facility provides individual workshop and classroom education for maintenance and engineering staff at Heysham. It also facilitates important abilities such as valve commissioning, maintenance and faultfinding which must be observed. The valve actuators are significant in power station control systems.

The article informs about Scottish Power PLC's purchase of electric actuators worth £300,000 from ABB Ltd. for its Longannet power plant. The Longannet power plant is the largest power plant of Europe and second largest coal-fired power station in Great Britain. The plant produces 600MW of electricity, serving the need of two million people. Eight pulverized mills are used to fulfill the coal demand of Longannet's four generating units. Dampers are installed to control the combustion produced from mills. Around 56 part-turn actuators are designed to control the mill dampers which are sufficient for three to four production units. Other actuators from ABB Ltd. regulate valves to control the flow of water entering into the boiler.