Suitability of light scattering technique for measurements of water droplets in turbine wet steam flows

International audienceSuitability of light scattering technique for measurements of droplets in turbine wet steam flow depends on a variety of parameters. This paper examines all relevant aspects for droplet measurements inside low pressure steam turbines. On basis of light scattering theory, influence of these aspects for a distinct measurement of droplets is investigated. After clarification of these factors, a discussion on measurement errors is given comprising errors that lie within the physics of light scattering theory as well as those caused by the measurement configuration. Possible avoidance by selection of proper measurement equipment and an elaborate design and setup of the probe is described including an estimation on each errors significance on measurement results. Light scattering technique is then evaluated on its applicability for low pressure steam turbines. It is argued in favor of light scattering that only measurements of single droplets provide insight into the fundamentals of droplet condensation and growth during expansion. Requirements for measurements with a light scattering probe in steam turbines regarding the system's design and composition are pointed out. Finally an outlook on present and future developments is given

What is Stored, Why, and How? Mental Models, Knowledge, and Public Acceptance of Hydrogen Storage

AbstractAlthough electricity storage plays a decisive role for the German “Energiewende,” and it has become evident that the successful diffusion of technologies is not only a question of technical feasibility but also of social acceptance, research on electricity storage technologies from a social science point of view is still scarce. This study, therefore, empirically explores laypersons’ mindsets and knowledge related to storage technologies, focusing on hydrogen. While the results indicate overall supportive attitudes and trust in hydrogen storage, some misconceptions, a lack of information as well as concerns were identified which should be addressed in future communication concepts

Optimized Approach for Determination of the Solid Temperature in a Steam Turbine in Warm-Keeping-Operation

International audienceThe determination of the temperature distribution in the thick-walled components in steam turbines is increasing in relevance. Due to the growing share of volatile renewable power generation, power plants with a high flexibility and a high integral efficiency are required. e current operational conditions lead to high thermal stresses inside the heavy components and thus to a reduced lifetime. To improve the ability for a fast start-up, the steam turbine can be kept warm during a longer period of stand still. Therefore, information about the metal temperature inside the rotor and the casing are crucial. However, the temperature distribution of the inner casing and especially the rotor cannot be measured without high additional effort. us, a calculation model with sufficient accuracy and also manageable calculation effort is required. In the present work, a hybrid-numerical FEM and analytical-approach has been developed to calculate the solid body temperatures of a steam turbine in warm-keeping operation in a most efficient way. The presented model provides accuracy of nearly % compared with Conjugate-Heat-Transfer simulations with a simultaneously reduced calculation effort by a factor of more than

Test Rig for Applied Experimental Investigations of the Thermal Contact Resistance at the Blade-Rotor-Connection in a Steam Turbine

International audienceStudies have shown that in a pre-warming respectively warm-keeping operation of a steam turbine, the blades and vanes transport most of the heat to the thick-walled casing and rotor. Thereby, a bottle-neck arises at the connection between the blade root and the rotor. The contact heat resistance at these interfaces affects the temperature distribution and thus the thermal stresses in the rotor. The present paper introduces a thermal contact resistance test rig, which is designed to quantify the contact heat transfer at the blade-rotor-connection of a steam turbine. An uncertainty analysis is presented which proves that the average measurement uncertainties are less than one percent. In addition to the test rig, a numerical model of the specimen for the determination of the thermal contact resistance is developed and introduced. Results of several steady-state measurements under atmospheric and evacuated atmosphere using a highly temperature-resistant chromium molybdenum steel are shown. As a main influence parameter the contact pressure is investigated, which is affected by the rotational speed of the turbine. The investigations show a significant contact heat resistance especially at small contact pressures

Thermomechanical Analysis of Transient Temperatures in a Radial Turbine Wheel

In turbomachinery design, the accurate prediction of the life cycle is one of the most challenging issues. Traditionally, life cycle calculations for radial turbine wheels of turbochargers focus on mechanical loads such as centrifugal and vibration forces. Due to the increase of exhaust gas temperatures in the last years, thermomechanical fatigue in the turbine wheel came more into focus. In order to account for the thermally induced stresses in the turbine wheel as a part of the standard design process, a fast method is required for predicting metal temperatures. In order to develop a suitable method, the mechanisms that cause the thermal stresses have to be understood. Thus, in a first step, a detailed analysis of the temperature fields is conducted in the present paper. Extensive numerical simulations of a thermal shock process are carried out and validated by experimental data from a test rig. Based on the results, the main heat transfer mechanisms are identified, which are crucial for the critical thermal stresses in transient operation. It is shown that these critical stresses mainly depend on local 3D flow structures. With this understanding, two fast methods to calculate the transient temperatures in a radial turbine were developed. The first method is based on a standard method for transient fluid/ solid heat transfer. In this standard method, heat transfer coefficients are derived from steady-state computational fluid dynamics (CFD)/conjugate heat transfer (CHT) calculations and are linearly interpolated over the duration of the transient heating or cooling process. In the new method, this interpolation procedure was modified to achieve an exponential behavior of the heat transfer coefficients over the transient process in order to enable a sufficient accuracy. Additionally, a second method was developed. In this method, the specific heat capacity of the solid state is reduced by a "speed up factor" to shorten the duration of the transient heating or cooling process. With the shortened processes, the computing times can be reduced significantly. After the calculations, the resulting times are transferred into realistic heating or cooling times by multiplying them with the speed up factor. The results of both methods are evaluated against experimental data and against the results of a numerical method known from literature. The methods show a good agreement with those data

Dynamic Simulation of a solar tower system with open volumetic receiver - a review on the vICERP project

The paper presents an overview on the modeling and simulation activities of the virtual institute for central receiver power plants (vICERP). Within a three years launch period models and tools for dynamic simulation of central receiver power plants have been developed by the five research institutes involved. The models are based on the Modelica modeling language. Today, models for the heliostat field, the receiver, the air cycle, the thermal storage, and the water-steam cycle are available within the consortium. As a first application, the Solar Tower Jülich technology was used as a reference. Models are validated with real operational data from the Solar Tower Jülich