Browsing by Author "Vogt, Damian M. (Prof. Tekn. Dr.)"

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Open Access
Modeling and simulation of solar hybrid microturbine technology based on a parabolic dish solar concentrator
(2025) Arifin, Maulana; Vogt, Damian M. (Prof. Tekn. Dr.)
The development of Concentrated Solar Power (CSP)-based solar hybrid microturbines presents a formidable challenge. The system effectiveness relies on various factors, including weather conditions, time of day, and location, all of which contribute to its dynamic interaction between key components: the compressor, turbine, combustor, and solar receiver during daily operations. However, despite the promising potential, a commercial solar hybrid microturbine utilizing a parabolic dish solar concentrator remains unavailable in the market. Consequently, there exists a significant gap in understanding the behavior and characteristics of this system, leaving crucial questions unanswered in the existing literature. Notably, the performance of the turbomachinery components, solar receiver, and combustor arrangements play essential roles in the solar hybrid microturbine concept. Therefore, rigorous investigations are imperative to establish a fundamental understanding of the system dynamic behavior and pave the way for the future design of more efficient compressors and turbines. Addressing these challenges, the Energy Research Group at BRIN (formerly LIPI) and ITSM at the University of Stuttgart collaborated to develop a CSP system based on hybrid solar microturbines for a remote area in Indonesia. The concept involves integrating a solar receiver and a combustor into a single turbo-machine, utilizing a parabolic dish solar concentrator to harness solar energy effectively. To enhance performance and operating range, a novel concept of multiple splitter blades is implemented in the radial compressor. The radial turbine is also designed with a novel cavity structure inside the rotor to achieve a lightweight design. The primary objective of this work is to design a system capable of generating up to 40 kW of power output. The initial objective of this study is to develop a preliminary design tool for predicting the performance of the solar hybrid microturbine. The model accounts for both the on-design condition and the variations in ambient temperature and Direct Normal Irradiance (DNI) throughout the year, utilizing meteorological data from the specific location in Indonesia. Moreover, the economic aspects of the system are considered. Furthermore, a thorough investigation is conducted to comprehend the steady and dynamic operational behavior of the solar hybrid microturbine, including a comparison performance of the system between series and parallel configurations for reducing fuel consumption and emissions from the combustor. The present study also evaluates the design and optimization of the turbomachinery components such as radial compressor and turbine for solar hybrid microturbine. The design process begins with the utilization of mean-line models based on enthalpy loss models and progresses to 3D simulations utilizing computational fluid dynamics (CFD), finite element analysis (FEA), and surrogate-based optimization. Recent updates to enthalpy loss models were evaluated and compared to assess the accuracy of the mean-line models in predicting performance. The new design of a multi-splitter in the radial compressor and a modified cavity structure for the radial turbine rotor were also evaluated and analyzed. The performance of radial compressors and turbines was compared using air and sCO2 as the working fluids. The thesis delivers that the parallel configuration system exhibits higher overall performance compared to the series configuration, mainly due to lower pressure losses in the parallel setup. However, fluctuations in the mass flow rate distribution between the solar receiver and combustor lead to a slight decline in the thermal and fuel efficiency of the parallel configuration when compared to the series configuration. This reduction can be attributed to variations in the air mass flow at the solar receiver and combustor during periods of decreasing or increasing solar heat input. The results demonstrate that the optimized turbomachinery components exhibit improved performance compared to the baseline design. There is an improvement in the total-to-total efficiency at the same pressure ratio and the operating range has been expanded for both air and sCO2 radial compressor when comparing the non-splitter and multiple-splitter designs. The cavity structure design for the rotor blade of both air and sCO2 turbine has been optimized with variations to support a lightweight structure, which has led to a significant increase in structural stability and a reduction in maximum stress, as well as prevented potential dangerous vibrations at the design operating conditions.
Open Access
Novel concept for the control and operation of radial turbine
(2023) Hassan, Ahmed Farid Saad Ayad; Vogt, Damian M. (Prof. Tekn. Dr.)
Radial turbines have proven their capability in many applications, due to their ability to operate at high-pressure ratios, structure robustness, and inherent cost advantages compared to the axial turbine. Controlling their performance allows efficient operation, even when operating at off-design conditions. Various control concepts are used for this purpose. These concepts depend mainly on movable parts and complicated control mechanisms, which limits radial turbines usability in some applications. Hence the need rises for a new control concept based entirely on fixed parts. Responding to these requirements, the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) at the University of Stuttgart started a research project which aims to build and test a new control concept for radial turbines. The idea behind this concept is to replace the traditional spiral casing with a new casing. This casing consists of multiple channels which divided the rotor inlet circumferentially to many sectors. Each channel is connected to control valves. Opening and closing these valves will control the turbine inlet area and the operating mass flow by applying different partial admission configurations. The main advantage of this new concept is that it is based only on fixed geometry, and the control valves could be placed away upstream of the turbine. Therefore the turbine can operate under control in any application requiring higher temperature ranges and smaller turbine size. Among various radial turbine applications, turbocharger has been chosen to apply and test the new control concept. In turbocharger application, matching between the radial turbine and the Internal Combustion Engine (ICE) is a complicated balance of many design parameters. Therefore it requires a control mechanism to adjust the turbine mass flow for different ICE operating regimes and achieve an efficient operation. Thus, it was chosen for this task due to its sensitivity toward the control aspects. The first assignment of this study is to build a design tool in order to apply the new control concept by designing Multi-channel Casing (MC) for the radial turbine. This casing will replace the traditional spiral casing and provide a mass flow characteristic comparable to that of the original turbine design at acceptable operating efficiency. Moreover, this design tool will be tested experimentally for a selected case to ensure the design requirements. After achieving the design requirements, different partial admission configurations will be applied to control the turbine performance. The second assignment is to study the effect of the casing replacement on many radial turbine design aspects such as performance, blade excitation and aerodynamic damping at full and different partial admissions conditions. The thesis delivers a MC design model that is capable of replacing the spiral casing with an MC and ensuring comparable mass flow characteristics. It proves also that using the MC design can enhance the radial turbine operating efficiency by 1 up to 3 percent compared to the traditional spiral casing under some design considerations. The results illustrate also the effect of using the MC on the turbine performance and blade vibration during full and partial admission. They explain the reason behind the efficiency drop during the partial admission which is attributed mainly to the flow deviation due to the pressure difference between open and closed channels. They show also how selecting the channel count and building the excitation map for different admission configurations is crucial to avoid high blade vibration amplitude and High Cyclic Fatigue (HCF) during the turbine operation.