Christian Oliver Paschereit

Technische Universität Berlin | TUB · Department of Fluid Dynamics and Technical Acoustics

A two-dimensional unsteady reactive Euler solver is employed to model rotating detonation combustion (RDC). A baseline case is chosen, and several combustor geometric and design parameters are varied individually in order to assess their effect on flowfield structure, exhaust flow properties, and performance. The parameters of interest are the peri...

To fight global warming the European Union formulated the objective of completely decarbonising the energy sector, stimulating the advent of unconventional fuels and the adaption of the corresponding energy infrastructure. The decarbonisation strategy identified hydrogen to play a key role as an energy storage medium, making systems capable of pure...

In the H2mGT project, funded by the German BMWK, a micro gas turbine (mGT) burner with 100% hydrogen firing is developed and validated. The project is a collaboration between TUB and the manufacturer Euro-K GmbH. It consists of three phases: 1. Atmospheric pressure tests with optical access; 2. Atmospheric pressure tests with secondary air injectio...

To limit global warming, meet growing global energy demand and to increase security of supply, enormous investments are now being made in renewable electricity generation. A high-efficiency process, called the Biomass-fired TopCycle (BTC), is being developed by Phoenix BioPower to address this market. By increasing the electrical efficiency, a cost...

In this study, the acoustics and flame dynamics of a prototype multi jet burner with 19 individual mixing tubes for operation with pure hydrogen and pure natural gas are experimentally investigated. The burner transfer matrix of the jet burner is determined from experimental data and acoustic network modeling, showing very good agreement. A compari...

Most industrial gas turbine combustion systems feature two or more separately controlled fuel lines. Every additional fuel line improves the operational flexibility but increases the system's complexity. When designing such a system, the goals are low emission of various pollutants and avoiding lean blow out or extinction. Typically, these limitati...

For flame stabilization, burner systems are usually equipped with swirlers which incite a defined air rotation, quantified by the swirl number. In consequence, the swirl number, which significantly influences the flame dynamics, is fixed. Applications exist in which the swirl number can be varied through mechanically adjustable swirler geometries....

To fight global warming the European Union formulated the objective of completely decarbonising the energy sector, stimulating the advent of unconventional fuels and the adaption of the corresponding energy infrastructure. The decarbonisation strategy identified hydrogen to play a key role as an energy storage medium, making systems capable of pure...

The vision of a carbon-neutral world, implies the shift from fossil to clean fuels for combustion-driven processes and machines like gas turbines. Green hydrogen is a promising alternative to substitute natural gas and other fossil fuels. In the H2mGT project, funded by the German BMWK, a micro gas turbine (mGT) burner with 100% hydrogen firing is...

Gas turbines that are used as compressor drives are often operated in the part load regime because compressor stations are usually designed for operation with full power at extreme weather conditions. Consequently, these gas turbines must comply with strict emission regulations at unfavorably low turbine inlet temperatures. To extend the low emissi...

In this work, we investigate a single hydrogen jet burner with a premixed pilot injection stage. This burner enables combustion of pure natural gas and hydrogen as well as blends of both fuels. To determine the operational capabilities of this burner different blends of these two fuel types are investigated regarding NOx emissions and flame shape....

To realize the projected increase in world-wide demand for floating offshore wind, numerical simulation tools must capture the relevant physics with a high level of detail while being numerically efficient. This allows engineers to have better designs based on more accurate predictions of the design driving loads, potentially enabling an economic b...

Gas turbines that are used as compressor drives are often operated in the part load regime because compressor stations are usually designed for operation with full power at extreme weather conditions. Consequently, these gas turbines must comply with strict emission regulations at unfavorably low turbine inlet temperatures. To extend the low emissi...

Thermoacoustic oscillations are a major challenge in gas turbine combustor design. Data-driven methods can help to design combustors without requiring an understanding of the underlying physics. However, data-driven optimization is usually associated with a high number of tests and is therefore not practical for costly combustion processes. A metho...

Hydrogen as an essential part of future decarbonisation of the energy industry makes it a crucial necessity to replace conventional, natural gas based concepts in gas turbine combustion. This paper presents an experimental study of a multi tube jet flame burner. The study is carried out with natural gas and pure hydrogen fuel at gas turbine relevan...

The COVID-19 pandemic demonstrated that reliable risk assessment of venues is still challenging and resulted in the indiscriminate closure of many venues worldwide. Therefore, this study used an experimental, numerical and analytical approach to investigate the airborne transmission risk potential of differently ventilated, sized and shaped venues....

The development of a novel burner concept for the synthesis of nanoparticles in spray flames is described and the prototype is experimentally characterised. The burner was designed to enable the process to be scaled up while maintaining stable operation in terms of fluid mechanics and combustion kinetics. It utilises a hydrogen pilot flame that is...

In this study, the acoustics and flame dynamics of a prototype multijet burner with 19 individual mixing tubes for operation with pure hydrogen and pure natural gas are experimentally investigated. The burner transfer matrix of the jet burner is determined from experimental data and acoustic network modeling, showing very good agreement. The burner...

Hydrogen as an essential part of future decarbonisation of the energy industry makes it a crucial necessity to replace conventional, natural gas based concepts in gas turbine combustion. This paper presents an experimental study of a multi tube jet flame burner. The study is carried out with natural gas and pure hydrogen fuel at gas turbine relevan...

Gas turbines that are used as compressor drives are often operated in the part load regime because compressor stations are usually designed for operation with full power at extreme weather conditions. Consequently, these gas turbines must comply with strict emission regulations at unfavorably low turbine inlet temperatures. To extend the low emissi...

The majority of premixed industrial gas turbine combustion systems features two or more separately controlled fuel lines. Every additional fuel line improves the operational flexibility but increases the complexity of the system. When designing such a system, the goals are low emission of various pollutants and avoiding lean blow out or extinction....

The COVID-19 pandemic has focused attention to the importance of understanding and mitigating the airborne transmission of pathogens in indoor environments. This study investigated the aerosol distribution in different indoor venues with varying ventilation concepts, including displacement, mixed, and natural ventilation. A measurement system was d...

The COVID-19 pandemic demonstrated that reliable risk assessment of venues is still challenging and resulted in the indiscriminate closure of many venues worldwide. Therefore, this study used an experimental, numerical and analytical approach to investigate the airborne transmission risk potential of differently ventilated, sized and shaped venues....

The potential of airfoil optimisation for the specific requirements of airborne wind energy (AWE) systems is investigated. Experimental and numerical investigations were conducted at high Reynolds numbers for the S1223 airfoil and an optimised airfoil with thin slat. The optimised geometry was generated using the NSGA-II optimisation algorithm in c...

Volume correction factors have been an important aspect when reporting pollutant emissions from gaseous combustion for many years. Their application has become standard procedure in such a way that their applicability is seldom questioned. However, their emergence dates back to a time when power generation primarily relied on conventional fuels suc...

A time resolved, two-dimensional reactive Euler solver is employed to simulate Rotating Detonation Combustion (RDC). The influence of combustor diameter, axial length, combustion annulus mass flux, outlet throat area, and air injector area on the flow field geometry and performance is studied. There is a similarity in the unsteady outlet state for...

This paper presents an experimental assessment of a blended fatigue-extreme controller for load control employing trailing edge flaps on a lab-scale wind turbine. The controller blends between a repetitive model predictive controller that targets fatigue loads and a dedicated extreme load controller, which consists of a simple on-off load control s...

In this study, we use an annular combustor experimental model with electroacoustic feedback to investigate systematically the effect of stochastic forcing and of non-uniform flame response distribution on azimuthal thermoacoustic modes. We break the symmetry of a nominally degenerate mode of azimuthal order m by imposing a non-zero 2m Fourier compo...

This experimental study explores fundamental qualitative differences of the response of a lean-premixed turbulent swirl flame to azimuthal acoustic excitation in the low- (LF), medium- (MF), and high-frequency (HF) regime. An experimental test rig with a cylindrical combustion chamber is equipped with an array of azimuthally distributed acoustic dr...

A towing tank is utilized to investigate the flow field around a two-dimensional submerged foil model operating near the free surface. Free surface effects are analyzed for steady and unsteady model velocity. The model’s submergence depth and angle of attack are varied. Tests are conducted for the model facing upside-up and upside-down. The surface...

In this study, we investigate experimentally the linear and nonlinear thermoacoustic response of an annular combustor model with electroacoustic feedback to study the effects that various types of asymmetric modifications have on the system’s eigenvalue degeneracy, and on its self-sustained oscillations. The baseline configuration has a nominal rot...

In this study, we use an annular combustor experimental model with electroacoustic feedback to investigate systematically the effect of stochastic forcing and of non-uniform flame response distribution on azimuthal thermoacoustic modes. We break the symmetry of a nominally degenerate mode of azimuthal order m by imposing a non-zero 2m Fourier compo...

Lean premix combustion is the state of the art technology to achieve ultra low NOx emissions in stationary gas turbines. However, lean premix flames are susceptible to thermoacoustic instabilities, lean blowout and flashback. The design of such a combustion system is thus always related to the balancing between the levels of emissions and flame sta...

Blending of natural gas with hydrogen is a viable pathway for the decarbonization of industrial gas turbines for combined heat and power applications. Very high blending ratios of hydrogen are needed to achieve significant CO2 emission reductions. However, burning high hydrogen contents in the gas turbine is challenging in terms of NOx emissions an...

Lean premixed combustion is the state of the art technology to achieve ultra low NO X emissions in stationary gas turbines. However, lean premixed flames are susceptible to thermoacoustic instabilities, lean blowout and flashback. The design of such a combustion system is thus always related to the balancing between the levels of emissions and flam...

This wind tunnel study investigates the aerodynamic effects of mini Gurney flaps (MGFs) and their combination with vortex generators (VGs) on the performance of airfoils and wind turbine rotor blades. VGs are installed on the suction side aiming at stall delay and increased maximum lift. MGFs are thin angle profiles that are attached at the trailin...

Lifting-line based solvers could supersede the blade element momentum (BEM) method as the industry standard in the near future as rotor sizes of modern wind turbines and computational resources continue to increase. A comparison study between both methods is presented where the IEA 10 MW wind turbine is evaluated in the aero-servo-elastic simulatio...

Operation under stable conditions is an important prerequisite for gas turbine safety. While recent studies have focused primarily on acoustic design to avoid thermoacoustic instabilities, in the present study we shift the focus to improving stability margins by flame transfer function (FTF) modification. The flame transfer function of premixed fla...

This paper presents the results of an advanced control strategy that employs active trailing edge flaps to reduce the fatigue loads of an experimental wind turbine. The strategy, called repetitive model predictive control, is a multiple‐input multiple‐output controller that aims at the alleviation of out‐of‐plane blade root bending moments. The str...

This study describes the impact of postprocessing methods on the calculated parameters of tip vortices of a wind turbine model when tested using particle image velocimetry (PIV). Several vortex identification methods and differentiation schemes are compared. The chosen methods are based on two components of the velocity field and their derivatives....

Kiel probes have the potential to be a versatile tool for determining stagnation pressure gain in rotating detonation combustors (RDCs), accompanying the commonly used equivalent available pressure method. Although average pressure gain values determined with Kiel probes are comparable to those from thrust stand experiments, one can expect several...

Mitigation of pressure pulsations in the exhaust of a pulse detonation combustor is crucial for operation with a downstream turbine. For this purpose, a device termed the shock divider is designed and investigated. The intention of the divider is to split the leading shock wave into two weaker waves that propagate along separated ducts with differe...

This study describes the experimental characterization of an RDC across a broad parameter range. The operation and stagnation pressure gain of this device are quantified while varying the air injector area, the fuel injector area, the annulus width, the outlet throat area, the mass flow rate, and the equivalence ratio. It is shown that a reduction...

View Video Presentation: https://doi.org/10.2514/6.2022-0278.vid This paper presents the experimental results of an active flap controller on the recently updated Berlin Research Turbine. The three blades of the horizontal axis wind turbine are equipped with active trailing edge flaps. The fatigue load reduction capabilities of a repetitive model p...

In order to determine the flame transfer function of a combustion system, different mechanisms have been identified that need to be modeled. This study focuses on the generation and propagation of one of these mechanisms, namely, the swirl fluctuations downstream of a radial swirl combustor under isothermal conditions. Swirl fluctuations are genera...

Pressure gain combustion as an alternative to isobaric combustion has been in the focus of research for the past decades as it potentially allows for increasing the thermal efficiency of conventional gas turbines significantly. Beside the most known concepts, such as pulse detonation and rotation detonation combustors, the shockless explosion combu...

The generation of large pressure fluctuations at the combustor outlet due to the periodic combustion process involving propagating detonation waves is a major drawback on the way of integrating a pulse detonation combustor (PDC) into a gas turbine. Recently, the attachment of an annular plenum downstream of a multi-tube PDC was proposed to allow fo...

Numerical simulations are used here to obtain further understanding on the flashback mechanism of a technically premixed hydrogen flame operated in lean conditions. Recent work from the authors (Mira et al., 2020) showed that the hydrogen momentum strongly influences the flame dynamics and plays a fundamental role on the stability limits of the com...

A theoretical idea on how to effectively increase the robust stability of the entire thermoacoustic system through specific modification of the flame transfer function. We apply the Nyquist method, well known in control engineering, to thermoacoustic systems and extend the analysis to account for parameter uncertainties and considerations about rob...

This published paper is freely accessible here: https://doi.org/10.5194/wes-7-943-2022 or https://wes.copernicus.org/articles/7/943/2022/

This study describes the impact of postprocessing methods on the calculated parameters of tip vortices of a wind turbine model when tested using Particle Image Velocimetry (PIV). Several vortex identification methods and differentiation schemes are compared. The chosen methods are based on two components of the velocity field and its derivatives. T...

The shockless explosion combustion (SEC) is a recently proposed concept aiming for pressure gain combustion through an unsteady process of multiple, distributed autoignitions occurring simultaneously. For this, a stratified fuel profile of dimethyl ether is injected into a continuous air flow. This profile is tailored such that the mixture residenc...

The observation of a Hopf bifurcation in fluid dynamics is commonly associated with the occurrence of a global hydrodynamic instability. The increase of a control parameter above a critical value causes a change from a stable to an unstable flow condition. This behaviour is well understood for the occurrence of instabilities in laminar flows. In tu...

This study explores the increase of stagnation pressure through a detonative combustion process in a rotating detonation combustor (RDC) operating on hydrogen and air. The features of the flow field in an RDC are introduced, as well as the most important length and time scales and how they influence the operating mode of such devices. Through the u...

Emission measurements from unsteady combustion systems such as Pulse Detonation Combustion (PDC) are challenging due to the inherently large variations in pressure, temperature, composition, and flow velocity of the exhaust gas. Comparison of experimental data is additionally complicated by differences in operating conditions and gas sampling setup...

The operation of a multitube pulse detonation combustor (PDC) evokes undesirable pressure fluctuations for a turbine downstream of the combustor. Pressure measurements in a downstream annular plenum reveal distinct pressure fluctuations. Although pressure peaks due to the shock waves emanating from the PDC tubes have been investigated in previous s...

This study describes a rotating detonation combustor (RDC) equipped with a set of nozzle guide vanes (NGVs) of variable number and inclination angle. Different instrumented guide vanes were manufactured and integrated for in situ measurements of static and stagnation pressure. It is shown that the mode progression and stagnation pressure gain of th...

Machine learning and automatized routines for parameter optimization have experienced a surge in development in the past years, mostly caused by the increasing availability of computing capacity. Gradient-free optimization can avoid cumbersome theoretical studies as input parameters are purely adapted based on output data. As no knowledge about the...

The generation and turbulent transport of temporal equivalence ratio fluctuations in a swirl combustor are experimentally investigated and compared to a one-dimensional transport model. These fluctuations are generated by acoustic perturbations at the fuel injector and play a crucial role in the feedback loop leading to thermoacoustic instabilities...