Optimizing a compressor, combustor and turbine system towards a 100 kWe hydrogen fueled micro gas turbine
Cedric Devriese defended his PhD thesis at the department of Mechanical Engineering on October 18th.
In the context of an increasing reliance on wind and solar power, the importance of storing energy for the power grid is becoming crucial. One promising method involves converting surplus or wasted electricity into green hydrogen through a process called electrolysis. Rather than using this green hydrogen to generate electricity in a large, conventional power plant, a more efficient approach is to integrate it into a Decentralised Energy System (DES). In a DES, green hydrogen can be used to produce both electricity and heat using various technologies like Reciprocating Internal Combustion Engines (RICE), micro Gas Turbines (mGT), or Fuel Cells (FC). mGTs offer distinct advantages over RICE engines, but they are less efficient. For his PhD Cedric Devriese designed a 100 kWe micro Gas Turbine that has a higher electrical efficiency than a RICE engine of the same size, but with a lower production cost than currently available micro gas turbines that run on natural gas or diesel.
Advantages mGTs over RICE engines
Among these options, RICE engines are currently the most commonly used for DES applications. However, mGTs offer distinct advantages over RICE engines, including lower maintenance costs, the ability to use multiple types of fuel, and the potential for reduced emissions, particularly nitrogen oxides (NOx). When compared to FCs, mGTs also have several benefits, such as higher power density, longer service life, less stringent hydrogen quality requirements, and reduced reliance on rare earth metals.
Lower electrical efficiency
Nonetheless, mGTs have a drawback: they are less efficient than both RICE engines and FCs. For instance, a 100 kWe FC unit can achieve 50% electrical efficiency, a RICE engine can reach up to 35%, while a typical natural gas-powered mGT with the same power output only achieves 30%. This lower electrical efficiency is why mGTs have a relatively small market share in small-scale Combined Heat and Power (CHP) systems. To address this efficiency challenge, one solution is to operate mGTs at higher Turbine Inlet Temperatures (TIT) to boost their electrical efficiency. To achieve the goal of a 100 kWe hydrogen-fueled mGT with enhanced efficiency, this study focuses on designing and optimizing the combustor, compressor, and turbine components. The outcome of this work includes a new design for a 100% hydrogen-fueled micromix-type combustion chamber, along with insights into the impact of various factors on combustion performance, emissions, and temperature.
Detailed design and cost estimate
Additionally, the study presents a design script for quickly and accurately sizing radial compressors and turbines, as well as a method to create performance maps with minimal computational simulations. Combining these elements, the research analyses and enhances the mGT cycle for improved Turbine Inlet Temperature (TIT), electrical efficiency, and operating range. The result is a detailed design and cost estimate for the compressor and turbine sections of a 100 kWe mGT, with a TIT of 1125°C and an electrical efficiency of 35.16%.
Title of PhD-thesis: The CFD design and optimization of a compressor, combustor and turbine system towards a 100 kWe hydrogen fueled micro gas turbine Supervisors: Rob Bastiaans, Niels Deen and Ward de Paepe.