Thesis (M. in mechanical engineering )--Washington State University, May 2009. / Title from PDF title page (viewed on Apr. 12, 2010). "School of Mechanical and Material Engineering." Includes bibliographical references (p. 48-49).

Improvements in the efficiency of power generation via turbomachinery are essential in order to reduce greenhouse gas emissions throughout the world. Advancements in measurement techniques are therefore crucial to understanding the main areas of energy loss in turbines and compressors. This thesis presents a novel system which allows that loss to be characterised using fast response, 3-D measurements of the pressure field within industrial scale rigs. Turbulent energy dissipation rates give an insight into where useable energy is lost from. To gain an insight into such rates, measurement techniques must be able to take data in all three dimensions simultaneously at high sampling rates, usually over 50 kHz. Traditional methods of flow characterisation such as optical techniques and pneumatic pressure probes are unable to capture the rapid fluctuations in pressure and velocity which lead to energy loss from the turbomachine. A new system was therefore designed and implemented into a 6-stage compressor rig to take fast response measurements at sampling frequencies up to 100 kHz behind the last stage stator. A fast-response 5-sensor pressure head, acquired from Kulite Semiconductor Products Inc, has been embedded into a bespoke stem to allow turbulence measurements in a range of turbomachinery applications. The five-sensor (5S) probe was calibrated for pressure sensitivity as well as aerodynamically to give total and static pressure along with velocity magnitude and direction. Individual sensors were calibrated and characterised at temperatures within a range of 200C and 500C, which corresponds to the conditions found within the final application. The probe was also used in a vortex shedding experiment where alternative eddies were detected from the 5S probe measurements in both the time and frequency domain. The aerodynamic calibration of the 5S probe consists of exposing the probe sensors to a range of flow angles in order to map their response between ±200 in both the yaw and pitch directions. This results in four non-dimensional coefficients, two to represent pressure and two to signify the flow angles. A linear interpolation method was written and implemented to deduce pressure and flow angles from experimental query points and the calibration data. The linear interpolation was used as an alternative to the standard surface fit method, where the calibration data is expressed as system of polynomial equations. It was found that the linear method was applicable to the interpolation of flow angles and gave a reduction in computation time of the order of 104. The total and static pressure values do however require the more tried and tested polynomial interpolation method due to the need for higher order interaction terms in the surface fit equation describing the terms. The fully calibrated 5S probe was then implemented into a 6-stage industrial scale rig where it acquired fast response pressure data from the flow field at the exit of the last stage vane. The data was processed to give time resolved, 3-D measurements of total and static pressure, flow angle and velocity. Due to the simultaneous capture of data from all 5 sensors, the resulting velocity vectors can be decomposed into their mean and periodic components to obtain values of energy loss from the turbomachine. The acquisition of such data from an industrial rig marks a novel advancement in the area of turbomachinery flow characterisation and the use of the 5S probe in a range of applications will begin to fulfil the need for a database of fast response data from chaotic and turbulent flow fields.

No description available.

It is clear that there is no long-term solution to energy supply problems other than planned and continuous conservation. The use of low-grade energy as an unlimited resource will play an important part in maintaining the balance between the future of the world for both developed and developing countries alike. A literature survey reviewing the most promising approaches to the construction of low-grade energy engines has been conducted. The validity of each feasible system has been examined and the principles of operation described. A feasibility study concerning the adoption_of the organic Rankine cycle utilizing common suitable refrigerants (e.g. halo-carbons) as working fluids has been conducted. In particular, the use of a multiple vane expander as the prime mover has been fully investigated. A suite of computer programs has been developed to: • describe working fluid properties; • optimise the geometrical and dynamical parameters of the Rankine cycle to achieve the most efficient operation in both steady and transient states; • optimise the mechanical design of the expander depending upon the mode of operation and the source and sink characteristics. A fully flexible experimental test facility was constructed so as to be capable of testing a wide variety of prime movers. This has been operated for a real time test period in excess of 300 hours. The test results are encouraging. Efficiencies were measured in accordance with the mathematical predictions and a portfolio of suggested modifications towards a high efficiency, low-cost, robust and reliable expander capable of utilising low grade thermal energy has been produced. Fruitful links with relevant British industries have been forged. Demonstrations of the system are planned within the UK and overseas.

The finite element method has been used to calculate the stresses and creep deformations of flanged turbine casing models subjected to internal pressure and bolting forces. The finite element results have been compared with results from photoelastic and lead model turbine casings. An axisymmetric thin shell of revolution ring finite element has been developed to analyse casings subjected to pressure, thermal and creep loads. The thin shell of revolution ring finite element is shown to be extremely powerful and has been used to investigate the shell portions of the turbine casing away from the flange. The three-dimensional isoparametric finite elements have been used for more accurate idealisations of the turbine casing. A thick shell isoparametric finite element has also been developed which can be used with the more common hexahedral isoparametric finite elements. A solution algorithm based on a frontal technique has been developed to solve the large number of linear equations given by the finite element equations. This algorithm, which is fully automatic and uses fast access backing store, has a resolution facility which is used to recalculate subsequent creep solutions assuming that the stiffness of the structure remains constant. The creep algorithms are based on time marching techniques where the creep solutions are found for small time increments, the final solution being the sum of all the incrementa1 solutions. During each time increment the stresses are assumed to remain constant and the change in stress between time increments is kept within a preset ratio. The creep algorithms have been used to predict the creep deformation of simple structures to compare with published results. The agreement between the finite element and lead model creep results is limited. The finite clement programs have been written to be compatible with the PAFEC suite of finite element programs.

No description available.

No description available.

Thesis (Ph. D.)--University of New South Wales, 2003. / Also available online.

Thesis (Masters in mechanical engineering)--Washington State University, May 2008. / Includes bibliographical references (p. 63-64).

This project aims to provide an in-depth understanding on pin-fin based cooling structure for gas turbine heat transfer applications, particularly for turbine hot-path airfoil blade trailing edge cooling. Based on past researches, new cooling structures are then proposed and investigated. This thesis is comprised by four primary studies including three experimental studies and one numerical study. Transient thermochromic liquid crystal method was used to measure endwall heat transfer coefficient of the channel while lumped capacitance method was used to measure the average heat transfer coefficient of cooling structure surface in corresponding studies. The Reynolds number was evaluated and pressure drop of flow across test channel was measured by the pressure taps. Parameters, such as Nusselt number, friction factor and thermal performance index, were evaluated based on experimental results. A scaled realistic NGV (Nozzle Guide Vane) hub platform model was tested. The local heat transfer distribution of its endwall was measured by liquid crystal method. The test has been carried out at Reynolds number range from 10,000 to 40,000. Two impinging nozzle plate with nozzle diameter of 5.5mm and 11.0mm were used. General findings include low heat transfer at acute angle corner and imbalance heat transfer distribution between upstream jet impingement region and downstream pin-fin region. The heat transfer rate at pin-fin region is only 44% of that at jet impingement region. Additionally, the existence of film hole (extraction hole) upstream of pin-fin region has insignificant influence on downstream pin-fin heat transfer in this test. It is also found that the heat transfer has been enhanced by 40% when the impinging nozzle diameter was doubled. Furthermore, the buoyancy effect at inlet flow has certain impact on magnitude and distribution of heat transfer at jet impinging target surface. The new elongated pedestal structure was proposed and investigated experimentally and numerically. Four elongated pedestal test sections with D/d=5.0 and 8.0, X/d=0.8 to 1.2, S/d=1.175 to 1.5 were designed and have been tested at Reynolds number range from 6,000 to 25,000. The average heat transfer coefficient at pedestal surface has been measured by lumped capacitance method. Revealed by the results, the heat transfer coefficient of pedestal surface could be at most 70% higher than that of endwall. Meanwhile, the pedestal surface could account for 50% of overall heat transfer at specific cases. The elongated pedestal structure enhanced the endwall heat transfer up to 9 times compare to reference data. Moreover, the elongated pedestal structure achieved similar heat transfer level comparing with perforated blockage structure but obtained 3 times higher heat transfer enhancement comparing to circular pin-fin structure. Generally, the tightly spaced structure obtained higher overall heat transfer than that of widely spaced structure which is same as circular pin-fin array. Via the numerical study, the flow behavior of elongated pedestal array is more like the turning flow inside the bending duct instead of flow around pin-fin structure. An extra structure, known as split elongated pedestal, has been studied numerically. However, the split elongated pedestal did not show significant improvement as expected in heat transfer enhancement as well as overall thermal performance. Currently split opening did not lead to significant flow interaction between two split parts. But it is recommended to further investigate this structure with much smaller split opening. Furthermore, three test sections with multiply cooling structure implemented were studied at Reynolds number range from 9,000 to 30,000. In addition, the test sections were modified in order to generate non-uniform inlet flow. One key finding is that the non-uniform inlet flow generated in this study leads to 25%-30% reduction in endwall heat transfer. Compare to circular pin-fin structure, cooling structure with high duct cross-section area block ratio, such as elongated pedestal and perforated blockage, provided more desired heat transfer distribution and higher heat transfer rate. Benefited from turbulence promotion by upstream pin-fin array, the heat transfer of downstream cooling configurations have been improved by 51%, 42% and 73% for pin-fin array, elongated pedestal array and perforated blockage array, respectively.