Flow and Combustion in Advanced Gas Turbine Combustors: 1581 (Fluid Mechanics and Its Applications)

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The inlet Reynolds number is ranging from 12, to 60, The detailed 3D fluid flow and heat transfer over the side-wall are presented. The overall performances of several ribbed passages are evaluated and compared. It is suggested that the usage of truncated ribs is a suitable way to augment the side-wall heat transfer and improve the flow structure near the leading edge.

The combustor-turbine interface is an essential component in a gas turbine engine as it allows for thermal expansion between the first stage turbine vanes and combustor section. Although not considered as part of the external cooling scheme, leakage flow from the combustor-turbine interface can be utilized as coolant.

This paper reports on the effects of orientation of a two-dimensional leakage slot, simulating the combustor-turbine interface, on the net heat flux reduction to a nozzle guide vane endwall. In addition to adiabatic effectiveness and heat transfer measurements, time-resolved, digital particle image velocimetry TRDPIV measurements were performed in the vane stagnation plane. Pin-fin channels are commonly used for cooling the trailing edges in turbine blades and vanes.

While many studies have investigated heat transfer performance of pin-fin channels, few studies have investigated pin-fin flowfields. The present study compares the time-dependent near wake flow and the time-mean surface heat transfer for varying pin-fin configurations at a Reynolds number of 2. Changes in streamwise and spanwise spacing, however, were found to significantly impact the behavior of the near wake flow and local heat transfer coefficients. In Computational Fluid Dynamics CFD is possible to identify namely two uncertainties: epistemic, related to the turbulence model, and aleatoric, representing the random-unknown conditions such as the boundary values and or geometrical variations.

In the field of epistemic uncertainty, Large Eddy Simulation LES and DES is the state of the art in terms of turbulence closures to predict the heat transfer in internal channels. The problem concerning the stochastic variations and how to include these effects in the LES studies is still open. In this paper, for the first time in literature, a stochastic approach is proposed to include these variations in LES.

http://taylor.evolt.org/katyn-orgaz-citas-por.php The Reynolds number has been chosen as a stochastic variable with a normal distribution. It is representative of the uncertainties associated to the operating conditions, i. The same method, applied to a steady RANS, generates a different level of uncertainty. This procedure proves that the uncertainties related to the unknown conditions, aleatoric, and those related to the physical model, epistemic, are strongly interconnected.

This result has directed consequences in the Uncertainty Quantification science and not only in the gas turbine world. This paper explores the conjugate heat transfer CHT numerical simulation approach to calculate the metal temperature for the gas turbine cooled stator. A full engine test with thermocouple measurement was performed and used to validate the CHT results. Metal temperatures calculated with the CHT model were compared to engine test data. The results demonstrated good agreement between test data and airfoil metal temperatures and cooling flow temperatures using the CHT model.

However, the CHT calculations in the outer end wall had a discrepancy compared to the measured temperatures, which was due to the fact that the CHT model assumed an adiabatic wall as a boundary condition. This paper presents a process to calculate convection heat transfer coefficient HTC for cooling passages and airfoil surfaces using CHT results.

This process is possible because local wall heat flux and fluid temperatures are known. This approach assists in calibrating an in-house conduction thermal model for steady state and transient thermal analyses. This paper investigates the accuracy of Uniform Crystal Temperature Sensors UCTS under transient conditions and describes a methodology for addressing sources of systematic error based on the findings. The study applies to the important task of thermal mapping of critical turbine parts during the engine development phase, for which UCTS is particularly well suited [1, 2, 3, 4].

A previous study focused on UCTS in steady state regimes and provided recommendations for optimizing the technique [5]. However, a substantial reduction in engine development costs may be achieved by being able to combine, for instance cyclic endurance tests with thermal mapping assuming that neither task will jeopardize the other. The basic trends and magnitude of measurement errors were assessed as a function of factors such as UCTS installation configuration, thermo-physical properties of the installation materials and cycle characteristics.

Stress calculations performed for the case of densely packed multi-UCTS installation on turbine blades showed no detrimental influence of standard micro-cavities on blade structural characteristics. These results were confirmed by a number of successful endurance tests, proving its compatibility with the task of thermography. Attention was focused on the cyclic test influence on the accuracy of thermal mapping.

Single and multiple cycle test configurations have been considered. After completion of a computational matrix, the characteristic results of interest are presented in the form of plots and diagrams to support the technical discussion. Recommendations drawn from this research will help analytical designers, test and instrumentation engineers to plan and execute dual task transient tests with a high accuracy of thermal mapping result interpretation. The purpose of this study is to clarify heat transfer characteristics for the high cooling performance with multiple jet impingement.

In the present study, the influence of the interaction among adjacent impinging jets on heat transfer of target surface is experimentally investigated. The study is focused on the effect of jet injection shape on the heat transfer. Injection distances L are 2 and 4 jet hole diameters, and jet-to-jet spacing S are 4, 6 and 8 jet hole diameters. Steady state thermochromic liquid crystal technique is employed to measure local and area averaged Nusselt numbers.

The flow field is visualized by smoke-wire and oil flow techniques. It is found that the cross-shaped circular jet array improves heat transfer at the intermediate area enclosed by four impinging jets compared to that of circular jet array at the narrow injection distance. Conjugate Heat Transfer studies are a common method to predict the thermal loading in high pressure nozzles. Despite the accuracy of nowadays tools, it is not clear how to include the uncertainties associated to the turbulence level, the temperature distribution or the thermal barrier coating thickness in the numerical simulations.

All these parameters are stochastic even if their value is commonly assumed to be deterministic.

Flow and Combustion in Advanced Gas Turbine Combustors

For the first time, in this work a stochastic analysis is used to predict the metal temperature in a real high pressure nozzle. The domain is the complete high pressure nozzle of F-type Mitsubishi Heavy Industries gas turbine with impingement, film and trailing edge cooling. The stochastic distribution of thermal barrier coating thickness, used in the simulations, has been measured at the midspan. A Gaussian distribution for the turbulence intensity and hot core location has been assumed. The two methods predict the same distribution of temperature with a maximum difference of 0. The experimental data are inside the uncertainty band associated to the CFD predictions except near at the trailing edge on the pressure side.

This work shows that one of the most important parameters affecting the metal temperature uncertainty is the pitch-wise location of the hot core. Assuming a probability distribution for this location, with a standard deviation of 1. The impact of turbulence level and thermal barrier coating thickness is one order of magnitude less important.

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A large portion of the over-tip leakage flow is often transonic for a typical high pressure HP turbine blade. It has been observed that the tip heat transfer is noticeably lower in a high speed flow tip region than in a low speed region. The present study therefore investigates the feasibility of controlling blade heat transfer by tip shaping to locally accelerate the flow to a transonic regime. The results show that a significant heat load reduction can be achieved by the local flow acceleration.

Such over-tip-shaping provides a great potential as an effective means to control heat load distribution and hence thermal stress over the blade tip surface. The feasibility of the concept and flow physics have been demonstrated in detail by CFD analyses, with and without the effect of moving casing. The experimental results obtained from a high speed linear cascade facility have also been presented. In addition, the proposed tip-shaping concept may also provide a potential for promoting choking inside the tip gap as a way to control the over-tip leakage mass flow.

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Most of these tests are taken in icing tunnels, which consist of usual wind tunnels and spray systems, and can be used to simulate the movement of super cooled water droplets in air. Generally, diameters of the droplets produced by the system are not unique in each test, and temperature of the water at the position of injections is much higher than the air at the same position. These factors may affect the droplets impingement characteristics and cause heat and mass transfer between droplets and the free steam.

So they should be taken into account in test analysis. In this paper, an improved Lagrangian approach is presented to simulate the unsteady process of droplets movement in the icing tunnel. This method considers the droplet size distribution where they are injected and heat and mass transfer during their movements. In addition, statistical approach is also developed in this method so that local collection coefficient of complex three-dimensional surface can be calculated. An entry strut of a turbo-shaft engine is chosen as a case to validate the effectiveness of the method.

This study examines experimentally the cooling performance of integrally cast impingement cooling channels which provide increased heat transfer area compared to traditional impingement configurations.

Professor Derek Bradley

For the evaluation of the heat transfer coefficient, the transient liquid crystal method was used. Full surface heat transfer coefficient distributions on the target plate and the side walls of the channel have been measured by recording the temperature history of liquid crystals using a frame grabber.

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Several impingement cooling geometries have been tested composing a test matrix of nine different geometrical configurations. The experimental data are analyzed by means of various post-processing procedures and aim to clarify and quantify the effect of hole staggering on the overall cooling performance, a variable which has been little addressed in the open literature. The experiments were carried out in a low speed wind tunnel over a wide range of Reynolds numbers between 15, and , The results indicated similarities with convectional multi-jet impingement cooling systems as well as a noticeable effect of the cooling hole pattern.

Finally, an error propagation analysis of the experimental uncertainties was performed providing information for the significance of scatter on repeated experiments. Jet impingement is an efficient heat transfer method and has been used successfully in cooling of turbine blades in gas turbine engines. Although many studies have been conducted on the heat transfer characteristics of jet impingement array, there is a lack of knowledge in pressure drop characteristics of large jet impingement arrays.

The pressure losses encountered are becoming increasingly important when applied to micro gas turbines, cooling concentrated solar panels and high density electronic chips. Numerical simulations were also performed with available commercial CFD tools. Reasonable comparisons between experimental results and numerical simulations were obtained.

Detailed flow structure, mass flow rate distribution, jet velocity profiles, and pressure drop within the array in the streamwise direction were obtained from the CFD simulations.

These simulations enhance the understanding of the physics within multiple jet impingement system. Additionally a semi empirical—analytical method is developed for calculating the total pressure loss within a multi jet impingement system. This simple methodology can provide a quick estimate of the total pressure drop and hence is suited for first order optimization.

The methodology is validated by results obtained from experiments and from CFD simulations. Contouring of turbine endwalls has been widely studied for aerodynamic performance improvement of turbine passages. However, it is equally important to investigate the effect of contouring on endwall heat transfer, because a substantial increase in endwall heat transfer due to contouring will render the design impractical.

In this paper, the effect of contouring on endwall heat transfer performance of a high-turning HP-turbine blade passage, operating under transonic exit Mach number conditions, is reported. Three endwall geometries were experimentally investigated at three different passage exit Mach numbers, 0.

One endwall is a non-contoured baseline endwall and the other two are contoured endwall geometries. One of the contoured endwall geometry was generated with the goal of reduction in stagnation pressure losses and the other was generated with the goal of reduced overall heat transfer through the endwall. Endwall surface temperatures were measured using infrared thermography technique.