Marcel Stoewer

The preliminary design of compressors depends upon a large number of parameters. Initially, the main characteristics and velocity triangles are defined by specifying the flow topology, i.e., whether the compressor is axial, mixed-flow, or centrifugal, the flow coefficient, and the loading coefficient, among other parameters. This paper presents a data-driven approach toward the creation of Smith charts for axial, mixed-flow, and centrifugal compressors on the basis of targeted three-dimensional computational fluid dynamics. The influence of the inlet hub-to-tip ratio, Mach number, the inlet Reynolds number, and the inlet boundary layer thickness on the Smith charts are analyzed. The results are applicable to the design of both single-stage and multi-stage compressors, such as the Mach number, Reynolds number, hub-to-tip ratio, and blockage vary from stage to stage. The compressors designed are then compared to the Cordier diagram. It is shown that the Mach number, Reynolds number, and hub-to-tip ratio significantly influence the Smith charts of compressors and limit the available design space in the Cordier diagram. In addition, changes in the suitable range of specific speeds of the topologies depending on the inlet conditions are shown. The diagrams presented in this paper serve as a guideline for the topology selection based on the flow coefficient and loading coefficient, considering the upstream flow conditions.

This paper presents the 4½-stage high-speed axial compressor open test case of the Institute of Turbomachinery and Fluid Dynamics, Leibniz University Hannover. Flow-path geometries, boundary conditions, previously published performance measurements, and new inter-row traverse measurement are provided for a selection of operating points.

The development of novel propulsion systems is essential to achieve the zero-emissions goals in aviation. One promising approach is the electrification of aircraft engines using hydrogen-based polymer electrolyte membrane fuel cells (PEMFC). In addition to the fuel cell stack, the propulsion system includes several subsystems, which determine the mass and volume and thus the feasibility of the architecture. A key subsystem is the cathode air supply, which preconditions the air for efficient and reliable operation. The compressor work required to pressurize the air has a significant impact on the power requirements, efficiency, and mass of the overall system. In addition, the operating range of the compressor influences the possible operating strategy of the fuel cell system. Another crucial subsystem of PEMFC-aircraft is the thermal management system, which manages the heat rejection of all heat sources in the fuel cell system. The paper is organized in two parts. In this part, Part I, a design approach for the air supply system and its components is presented. The objective is to apply the design method to a reference medium-range aircraft with a variable number of cathode air supply systems. This is an important decision point that influences both the design of the individual components of the cathode air supply system and the aircraft design, and thus the performance during the entire flight mission. The design points and boundary conditions are derived from an overall system simulation. Based on this, the compressor, turbine, and thermal management system are designed for the identified design points. In the companion paper, Part II, the compressor and turbine performance maps, as well as the key characteristics of the thermal management design are embedded into the overall system simulation tool in order to evaluate the entire flight mission and cover the impact of component design on the aircraft performance.

The use of polymer electrolyte membrane fuel cells (PEMFC) to generate propulsion power for future aircraft represents a promising approach to reduce carbon emissions caused by the aviation sector. The design of a PEMFC system requires a detailed consideration of the individual subsystems, such as the air supply and thermal management system. These subsystems have a significant impact on performance, parasitic power requirements, and system mass. For this reason, a comprehensive system analysis is required to evaluate the effects on aircraft performance for the entire flight mission. In Part I of this two-part paper, an initial design workflow is presented, focusing on the design point selection and the design of the turbo components and thermal management. The first objective of this part, Part II, is the integration of the components designed previously into the overall system calculation to cover interdependencies. For this purpose, the off-design performance of the air supply compressor, turbine, and thermal management is considered for a flight mission analysis on a standard and hot day scenario. Thereby, the effects on the propulsion power demand of the aircraft due to component masses, parasitic powers, and additional drag caused by the ram air heat exchanger are taken into account. The overall design process is iterative, as updated aircraft power demand affects the boundary conditions for the component design. The second objective of this study is to evaluate the influences and sensitivities of different operating strategies, power densities, as well as heat exchanger pressure losses on key system parameters such as fuel consumption, waste heat, and system mass. In addition, a weighted mission-specific efficiency is defined in order to facilitate a fast, yet application-oriented assessment of turbo component designs.