1,721,022 research outputs found
Measurement of local heat transfer coefficient on the endwall of a turbine blade cascade by liquid crystal thermography
No full textThis paper presents convective heat transfer measurements on the endwall of a turbine blade cascade by
means of the liquid crystal thermography. The measurement method is based on the heating, at uniform
heat flux, of the endwall by means of an electronic circuit board. The heated region of the endwall surface
exposed to the airflow is covered with a thermochromic liquid crystal coating. The colour map of the
coating during a given test, featured by an assigned mass flow rate, is measured by using an image processing
system. With a prescribed wall heat flux, the convective heat transfer coefficient is obtained, at
every pixel location, from the measured temperature maps recorded at the steady-state. Heat transfer
results, presented for the endwall of a high-pressure turbine cascade, have been obtained for different
values of the Reynolds number. Regions of the endwall surface associated with high rates of heat transfer
are well identified: the leading edge of blades, pressure and suction side corners, the blade wake and
cascade throat. The spatially-resolved heat transfer measurements presented here could provide a useful
baseline for a condition-specific, optimized endwall film-cooling solution that reduces overall heat
transfer rates
Effect of discrete-hole arrangement on film-cooling effectiveness for the endwall of a turbine blade cascade
No full textThis paper investigates film cooling in a turbine cascade endwall for two discrete-hole configurations using liquid crystal thermography. The discrete holes, arranged in rows aligned in the pitchwise direction, gave rise to relative maxima of film-cooling effectiveness downstream of each row, followed by a marked decrease of effectiveness along the gap between adjacent rows of holes. This resulted in a not efficient coverage of the endwall surface, with succession of over- and under-cooled regions. The re-design of discrete-hole configuration, based on knowledge of the heat transfer coefficient map on the endwall without film cooling, enabled the redistribution of the coolant to provide a better coverage of the endwall and a significant increase of the area-averaged film-cooling effectiveness
Heat transfer and friction in a high aspect ratio rectangular channel with angled and intersecting ribs
No full textForced convection heat transfer in a high aspect ratio (5:1) rectangular channel with 45 deg angled ribs
has been investigated. The ribs are periodically positioned on one wall of the channel, heated at uniform
heat flux over each inter-rib region. In the pursuit of heat transfer enhancement, longitudinal ribs (termed
intersecting ribs), oriented parallel to the mainstream, have been added to the angled ribs. Friction and
heat transfer characteristics were determined for two values (10000 and 20000) of the Reynolds number.
Liquid crystal thermography was employed as diagnostic tool in heat transfer experiments. The study was
supplemented with CFD numerical calculations using the RNG k-ε turbulence model. Local and regionally
averaged heat transfer and flow characteristics of the tested rib configurations have been presented and
compared. Both experimental and numerical results were able to capture the effect produced by the
intersecting ribs on vortices and their ability to locally increase the heat transfer coefficient and promote
its more uniform distribution. If the standard angled rib configuration is assumed to be the reference
condition, the thermal performance based on the same pumping power is increased in the case of the
insertion of one intersecting rib, while two intersecting ribs are unable to provide further enhancements
Aerodynamic and Thermal Characteristics of a Hot Jet in Parallel Flow
No full textThis paper presents an experimental investigation of the aerodynamic and thermal characteristics of a round jet of hot air, injected through a nozzle into a parallel air flow, simulating a hot streak. Experiments were performed by imposing the same total pressure, established by means of a five-hole probe, for the mainstream and the jet at nozzle exit. Time-averaged temperatures at different points over planes downstream of the nozzle exit section were measured by thermocouple rakes. Experimental data, presented in a non-dimensional form, provide a representation not correlated to individual maximum jet temperature and Reynolds number, in the respective fields of variation. The attenuation of the hot jet strength is reported as a function of the normalized axial coordinate for the various operating conditions considered. Results obtained for the hot jet discharged into a parallel flow are compared with data obtained for the hot jet spreading into stagnant air
Experimental Investigation of the Wake Shed from a High-Lift LPT Blade under Unsteady Inflow Conditions
No full textMeasurement of film-cooling effectiveness on a turbine endwall using a liquid crystal image method
No full textThe accurate evaluation of heat transfer and film-cooling effectiveness plays a crucial role in the design of efficient turbomachines. Liquid crystal (LC) thermography is a reliable measurement tool to obtain detailed, full-field maps of surface temperature. In this paper, a steady-state LC technique was employed for measuring the film-cooling effectiveness of a turbine endwall. The experiments were performed in a blow-down type wind tunnel housing a large-scale high-pressure turbine blade cascade. The endwall regions immediately upstream and in a passage of the cascade featured discrete holes, arranged according to two different discrete-hole arrangements. Liquid crystal images and reconstructions of the adiabatic film-cooling effectiveness are provided for the Reynolds number (based on the chord length and the isentropic exit velocity) of 960000 and for the blowing ratios of 2.5 and 3. Results for both discrete-hole configurations are presented and compared
Unsteady inflow effects on the wake shed from a high-lift LPT blade subjected to boundary layer laminar separation
No full textTechno-economic optimization of hybrid-electric power plants onboard cruise ships
No full textThis work aims at assessing energy, environmental and economic performances of hybrid-electric plants installed onboard large-size cruise vessels fuelled by Liquefied Natural Gas. Specifically, hybrid-electric power plants coupling combined gas electric and steam plants, reciprocating engines and lithium-ion battery pack are considered. By adopting cogeneration efficiency, carbon dioxide emissions, nitrogen oxide emissions and costs as objective functions, optimal performances were assessed by a Mixed Integer Linear Programming code, following a two-step procedure. First, the MILP code has been applied considering 8-days long, phase-mean operating profiles to identify an optimal design of the engine room. Second, power plant performances have been investigated by applying MILP code to hourly demand profiles, in order to provide more detailed insight on working schedule. Overall, as main outcome of the phase-mean analysis, the potential of combined gas electric and steam plants and lithium-ion batteries in promoting a more efficient energy utilization, reduced environmental impact and enhanced cost savings is proved. Specifically, combined gas electric and steam plant was shown to optimize objective functions during navigation and maneuvering, whereas batteries improved energy and environmental performances in the most demanding ship operating conditions. Furthermore, optimal sizing of lithium-ion battery pack was determined at 40 MWh, despite its economic competitiveness resulted to deeply rely on carbon tax. On the other hand, the hourly analysis showed that controlling the combined gas electric and steam plant and batteries according to a mixed spinning reserve-peak shaving strategy optimizes the performance of power plant even in port conditions, with almost no role played by reciprocating engines. In detail, in comparison to a reference non-hybrid electric power plant, batteries are shown to improve cogeneration efficiency and greenhouse gas emission savings by nearly 2%, whereas nitrogen oxide emissions and costs were reduced by 12% and 2%, respectively
An Experimental Investigation of the Wake Shed From a High-Lift Low Pressure Turbine Cascade at Different Reynolds Numbers.
No full textBoundary Layer Development on a High-Lift LP Turbine Profile under Passing Wakes Conditions
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