Markus Schatz

Helmut Schmidt University | HSU · Laboratory of Fluid Machinery

Considerable progress has been achieved in recent decades in understanding the phenomena related to the onset of condensation in steam flows, both experimentally and especially numerically. Nevertheless, there is still a certain disagreement between the different numerical models used. Unfortunately, the available experimental validation data are n...

The present experimental study was intended to investigate the impact of casing roughness on the tip leakage flow and the loss in a linear turbine cascade. Detailed flow measurements utilizing a five-hole probe, namely the so-called Oxford probe, and a miniaturized Pitot probe were made upstream and downstream of a row of steam turbine blades with...

To face the challenge regarding reconversion of stored green hydrogen into electricity, zero emission oxyfuel hydrogen cycles with steam as a working fluid are very promising in both thermal efficiency and large-scale applicability. Previous studies suggest that with Turbine Inlet Temperatures (TIT) of 1700 °C thermal efficiencies in excess of 70%...

Lightweight components are essential for the future of the energy and aerospace fields. This paper presents an innovative radial turbine design that utilizes a cavity structure on the rotor for solar hybrid microturbines. The performance of the cavity-structured radial turbine is studied using mean-line models, computational fluid dynamics (CFD), a...

div class="section abstract"> Dry dust testing of vehicles on unpaved dust roads plays a crucial role in the development process of automotive manufacturers. One of the central aspects of the test procedure is ensuring the functionality of locking systems in the case of dust ingress and keeping the dust below a certain concentration level inside th...

Multi-channel casing (MC) shows promising results in controlling the performance of the radial turbines. It has neither movable parts nor complicated control mechanisms therefore it withstands higher thermal loads compared to the commonly used control systems such as the Variable Geometry Turbine (VGT). This advantage makes the MC applicable for a...

Flow measurements were made in a steam turbine cascade with a single blade of reduced height modeling a blade damage. In the experiments, the height of the single blade varied from full span (i.e., no tip clearance) up to totally removing the blade. The experimental investigation was supported by computational fluid dynamics (CFD) simulations which...

Results from an experimental profile loss study are presented of an additive manufactured linear turbine cascade placed in the test section of a closed-loop organic vapor wind tunnel. This test facility at Muenster University of Applied Sciences allows the investigation of high subsonic and transonic organic vapor flows under ORC turbine flow condi...

The performance of axial diffusers installed downstream of heavy duty gas turbines is mainly affected by the turbine load. Thereby the outflow varies in Mach number, total pressure distribution, swirl and its tip leakage flow in particular. To investigate the performance of a diffuser at different load conditions, a generic diffuser geometry has be...

Evaporation cooling increases gas turbine power output. Experimental results suggest an 8% increase of power when 1% of the overall mass flow is added via water droplets injected upstream of the compressor. However, water injection has an impact on the flow field, which requires experimental research involving probe measurements in the droplet-lade...

A novel control technique for radial turbines is under investigation for providing turbine performance controllability. This technique is based on replacing the traditional spiral casing with a Multi-channel Casing (MC). The MC divides the turbine rotor inlet into a certain number of channels. Opening and closing these channels controls the turbine...

Pneumatic probes are commonly used to determine the flow vector as well as the thermodynamic state of the fluid in turbomachinery applications. The conventional method to measure a flow passage velocity or pressure field is to move the probe to discrete positions and to hold a certain settling time before valid data can be recorded. This study pres...

A novel control technique for radial turbines is under investigation for providing turbine performance controllability, especially in turbocharger applications. This technique is based on replacing the traditional spiral casing with a Multi-channel Casing (MC). The MC divides the turbine rotor inlet circumferentially into a certain number of channe...

The application of power plants based on renewable energy sources is attractive from an ecological viewpoint. Micro Gas Turbine (MGT) combined with solar energy is a highly promising technology for small-scale electric power generations in remote areas. In MGT state-of-the-art development, the necessity of the numerical optimization in turbomachine...

The performance of axial diffusers installed downstream of heavy duty gas turbines is mainly affected by the turbine load. Thereby the outflow varies in Mach number, total pressure distribution, swirl and its tip leakage flow in particular. To investigate the performance of a diffuser at different load conditions, a generic diffuser geometry has be...

Radial turbine featuring a Multi-channel Casing (MC) is a new design under investigation for enhancing the turbine controllability. The idea behind this new design is to replace the traditional spiral casing with a MC, which allows controlling the mass flow by means of opening and closing control valves in each channel. The arrangement of the close...

Multiple Exhaust DUct with Source Adjustment (MEDUSA) is a novel concept, which may be used to control the operation of radial turbines in turbochargers. This technique is based on replacing the traditional spiral volute with a Multi-channel Casing (MC) to provide turbine inlet area controllability, which in turn will control the inlet flow angle....

Partial admission using Multi-channel Casing (MC) is a technique under investigation for controlling the operation of radial inflow turbines. The MC has different admission configurations according to the number of open channels which control the relation between the mass flow and expansion ratio at different operating speeds in order to provide th...

This study presents the results of measurements in an industrial steam turbine test rig operated at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) in Stuttgart, Germany. In order to ensure safe operation over a wide range of operating conditions the last and penultimate rotor blade rows of this turbine feature Part-Span Con...

Most of the world’s power is produced by large steam turbines using fossil fuel, nuclear and geothermal energy. The LP exhaust hoods of these turbines are known to contribute significantly to the losses within the turbine, hence a minor improvement in their performance, which results in a lower backpressure and thus higher enthalpy drop for the ste...

It is well known that the last stage of a turbine and the subsequent diffuser should be viewed at and designed as a coupled system rather than as single standalone components. The turbine outlet flow imposes the inlet conditions to the diffuser, whereas the recovered dynamic pressure in the diffuser directly controls the turbine back pressure. With...

A numerical second law analysis is performed to determine the entropy production due to irreversibilities in condensing steam flows. In the present work, the classical approach to calculate entropy production rates in turbulent flows based on velocity and temperature gradients is extended to two-phase condensing flows modeled within an Eulerian-Eul...

It is well known that the last stage of a turbine and the subsequent diffuser should be viewed at and designed as a coupled system rather than as single standalone components. The turbine outlet flow imposes the inlet conditions to the diffuser, whereas the recovered dynamic pressure in the diffuser directly controls the turbine back pressure. With...

Performance optimization of low pressure steam turbine exhaust hood has been a subject of a number of both numerical and experimental studies. This is driven by the understanding that improving the diffuser and exhaust hood outer casing performance results in a lower turbine back pressure and hence an increased plant overall output. The performance...

A numerical second law analysis is performed to determine the entropy production due to irreversibilities in condensing steam flows. In the present work the classical approach to calculate entropy production rates in turbulent flows based on velocity and temperature gradients is extended to two-phase condensing flows modeled within an Eulerian-Eule...

The purpose of the “International Wet Steam Modeling Project” is to review the ability of computational methods to predict condensing steam flows. The results of numerous wet-steam methods are compared with each other and with experimental data for several nozzle test cases. The spread of computed results is quite noticeable and the present paper e...

At the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) Stuttgart, the droplet impact erosion phenomenon has been simulated with the help of an erosion test rig. The experiments confirm that the erosion resistance of steam turbine blade materials can be associated with different mechanical properties of materials. Different combi...

The results of the International Wet Steam Modelling Project presented at the Wet Steam Conference in Prague in 2016 again gave rise to a discussion about the suitability of the flow solver ANSYS CFX for the prediction of spontaneous condensation. In this article, the main reason for the discrepancy between results obtained with CFX and measurement...

An evaluation method for CFD simulations is presented, which allows an in-depth analysis of different loss mechanisms applying the approach of entropy creation proposed by Denton. The entropy creation within each single mesh element is determined based on the entropy flux through the cell faces and therefore the locations, where losses occur, can b...

The performance of the axial-radial diffuser downstream of the last low-pressure steam turbine stages and the losses occurring subsequently within the exhaust hood directly influences the overall efficiency of a steam power plant. It is estimated that an improvement of the pressure recovery in the diffuser and exhaust hood by 10% translates into 1%...

The influence of a cylindrical strut shortly downstream of the bladerow on the vibration behavior of the last stage rotor blades of a single stage LP model steam turbine was investigated in the present study. Steam turbine retrofits often result in an increase of turbine size, aiming for more power and higher efficiency. As the existing LP steam tu...

This paper presents a numerical investigation of the impact of different part-span connector (PSC) configurations on the flow field in a turbine passage. For this purpose a linear cascade based on a profile section of a typical reaction blade used in industrial steam turbines was modeled and 3D simulations with varying size, shape, axial position a...

An experimental and numerical study on the flow in a three-stage low-pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide rang...

Steam turbine retrofits often result in an increase of turbine size, aiming for more power and higher efficiency. As the existing LP steam turbine exhaust hoods are generally not modified, the last stage rotor blades frequently move closer to installations within the exhaust hood, such as baffles or ribs. To assess the influence of supporting ribs...

Industrial steam turbines are operated over an extremely wide range of operating conditions. In order to ensure safe turbine operation, even in blade resonance condition, conical friction bolts are mounted between blade reinforcements of adjacent last stage low-pressure blades. These part-span connectors (PSC) provide blade damping and coupling. Ho...

The present paper evaluates the impact of casing energized jet flow on the performance of an annular-conical exhaust diffuser. Two different inflow profiles, namely a uniform total pressure and a hub-strong total pressure inlet profile were studied. For both profiles, the flow is observed to separate at the casing. Experiments were performed at dif...

A new partial admission concept for turbocharger turbine operation at off-design is designed and investigated numerically and experimentally in a turbocharger test rig. This new concept is called MEDUSA (Multiple Exhaust Duct with Source Adjustment) and is based on a partial admission turbine system consisting of several separate flow channels that...

An experimental and numerical study on the flow in a three stage low pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide rang...

The correct computation of steam subcooling, subsequent formation of nuclei and finally droplet growth is the basic prerequisite for a quantitative assessment of the wetness losses incurred in steam turbines due to thermal and inertial relaxation. The same basically applies for the prediction of droplet deposition and the resulting threat of erosio...

Industrial steam turbines are operated over an extremely wide range of operating conditions. In order to ensure safe turbine operation, even in blade resonance condition, conical friction bolts are mounted between blade reinforcements of adjacent last stage low pressure (LP) blades. These part-span connectors (PSC) provide blade damping and couplin...

The correct computation of steam subcooling, subsequent formation of nuclei and finally droplet growth is the basic prerequisite for a quantitative assessment of the wetness losses incurred in steam turbines due to thermal and inertial relaxation. The same basically applies for the prediction of droplet deposition and the resulting threat of erosio...

A numerical study on the flow in a three stage low pressure industrial steam turbine with conical friction bolts in the last stage and lacing wires in the penultimate stage is presented and analyzed. Structured high-resolution hexahedral meshes are used for all three stages and the meshing methodology is shown for the rotor with friction bolts and...

In this publication an overview of the current state of wetness modeling at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) is given. For the modeling an Euler-Euler method implemented in the commercial flow solver ANSYS CFX is used. This method is able to take into account the non-equilibrium state of the steam and models t...

Combined heat and power generation (CHP) is a way of providing both electric power and thermal heat for industrial and domestic facilities at high fuel efficiencies. Often small and medium sized gas powered internal combustion (IC) engines, rated at electric power outputs of 50–600 kW, are used for such applications. During the time when the availa...

In this publication an overview of the current state of wetness modeling at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) is given. For the modeling an Euler-Euler method implemented in the commercial flow solver ANSYS CFX is used. This method is able to take into account the non-equilibrium state of the steam and models t...

In the last stages of steam turbines, large droplets (so-called coarse water) are generated from the wet steam flow. These droplets collide with the following rotating blades with almost the peripheral speed of the rotor. This high speed impact is perceived in the form of erosion of low pressure steam turbine blades. Among others, impacting droplet...

The prediction of the flow in a gas turbine exhaust diffuser of a combined cycle power plant is particularly difficult as maximum performance is obtained with highly loaded diffusers, which operate close to boundary layer separation. CFD (computational fluid dynamics) simulations then need to cope with complex phenomena such as smooth wall separati...

A new method for turbocharger control in automotive applications is presented. It is called MEDUSA (Multiple Exhaust DUct with Source Adjustment, European patent application number: 21326 - EP) and is a partial admission system consisting of several separate flow channels that connect the exhaust duct of the engine and individual nozzle segments of...

In the Institute of Thermal Turbomachinery (ITSM) at Stuttgart University, a three-stage model steam turbine was used to study the complex steam flow through the last stages of low pressure steam turbines. The conditions in this test rig were such that condensation occurred after the first stage, so that wet steam was prevalent in the last stage. I...

The three-stage low-pressure model steam turbine at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) was used to study the impact of three different steam inlet temperatures on the homogeneous condensation process and the resulting wetness topology. The droplet spectrum as well as the particle number concentration were measur...

Downstream of a modern combined cycle gas turbine there is generally an abrupt end of the turbine inner hub wall leading to a backward facing step with separation and flow recirculation on the hub axis. This can lead to a strong hub wake with high losses in the center of the diffuser. The interaction between the end of the hub and the downstream ax...

Results of numerical investigations of the wet steam flow in a three stage low pressure steam turbine test rig are presented. The test rig is a scale model of a modern steam turbine design and provides flow measurements over a range of operating conditions which are used for detailed comparisons with the numerical results. For the numerical analysi...

The last stages of a low-pressure steam turbine, with long freestanding blades, may experience forced response excitation during resonance crossing at start-up and shut-down and this can be responsible for blade failure. This paper presents an experimental investigation of the circumferential blade amplitude distribution at different operating cond...

The three-dimensional inhomogeneous flow in the exhaust hoods of low pressure steam turbines is a major cause of losses and the design of low-loss exhaust hoods remains a challenge, particularly in retrofit units. This paper examines the sensitivity of certain geometrical exhaust hood parameters on the pressure recovery of the whole exhaust system...

Apart from a few exceptions, Pelton-type turbines have been restricted to hydropower applications. This is mainly due to the fact, that conventional Pelton rotors suffer high disc friction windage losses due to their shape. Whereas this effect is almost negligible in hydropower applications because of the low density of air as surrounding medium co...

To guarantee a faultless operation of a turbine it is necessary to know the dynamic performance of the machine especially during start-up and shut-down. In this paper the vibration behaviour of a low pressure model steam turbine which has been intentionally mistuned is investigated at the resonance point of an eigenfrequency crossing an engine orde...

Large industrial gas turbines for combined heat and power generation normally have axial diffusers leading to the heat recovery steam generator. The diffusers operate with high inlet axial Mach number (0.6) and with a non-uniform inlet total pressure profile from the turbine. Tests have been carried out on a generic highly loaded axial diffuser in...

A new combined optical/pneumatic probe design has been developed in order to enhance steam wetness measurements on the basis of the light extinction method. The new design is a consequent further development of earlier probes. The probe diameter has been kept as small as 10mm, so that it can be used in a model steam turbine of the institute. Measur...