Conceptual Design of a Compressor Vane- HEX for LH2 Aircraft Engine Applications

In order to meet the ambitious environmental targets set by the Paris Agreement, new sustainable carbon neutral aviation fuels need to be introduced. The high gravimetry energy density of hydrogen, makes it a prime candidate for a future aviation fuel. However, the associated poor volumetric energy density, requires an increased aircraft volume and associated penalty in aerodynamic performance. The required volume occupied by the hydrogen fuel can be decreased in half, if stored in its liquid form. This however requires that the liquid hydrogen (LH2) is kept at cryogenic temperatures, requiring adequate tank insulation. Moreover, to increase the effective heating value of hydrogen, the fuel distribution system will include heat exchanger technology to increase the fuel temperature before injection in the combustion chamber. The present work provides an outlook of different heat exchanger technology for application in hydrogen fueled gas turbine aero engines. The heat exchangers can be placed in the vicinity of the engine to reject the heat generated by the gas core to the hydrogen fuel. Ideally, they are strategically located to use heat management to maximize the engine efficiency and ensuring sufficient component durability. Moreover, the combination of liquid hydrogen’s high specific heat with cryogenic storage temperatures results in a formidable cooling capacity that can be explored by more compact heat exchanger solutions

Development of fuel and heat management systems for liquid hydrogen powered aircraft

The presentation describes the recent developments in the design of the fuel and heat management systems for liquid hydrogen powered aircraft within the H2020 project ENABLEH2. The fuel distribution system main task is to deliver the right amount of hydrogen to the combustion chamber at an adequate pressure. This requires the usage of fuel pumps, valves, insulated piping, and a fuel control system to adjust the fuel flow for a given engine rating. Moreover, since liquid hydrogen is stored at cryogenic temperatures (-253C), it also requires the integration of heat exchanger technology to increase the fuel temperature up to a state where it can be efficiently mixed with air and combusted. The combination of hydrogen high specific heat with cryogenic temperatures results in formidable cooling capacity that can be explored by compact heat-exchanger solutions. Concepts that use existing engine aero-surfaces located after rotating turbomachinery are currently being investigated a Chalmers University of Technology.\ua0 A recently commissioned facility to investigate the potential benefits of a compressor flow cooling heat rejection system will also be discussed.\ua0 The test facility comprises a vertically mounted low-speed 2.5 stage compressor designed to operate continuously at rotor mid-span chord Reynold number up to 600,000, which is representative of a large-size future geared turbofan engine. Detailed aerothermal studies at TRL4 will be conducted to calibrate in-house design methods for radical core integrated heat exchangers. The facility is driven by a 147kW electric drive at a nominal speed of 1920 RPM. Traverse access is included in two 18-degree sectors for all the rotor-stator interfaces. At the upstream plane of the compressor outlet-guide-vane, four independent access traverse systems are included for a 360-degree access. Downstream, an ABB robot arm with a U-shaped probe mount provides full volume probing access in the exit compressor duct

Design of Chalmers new low-pressure compressor test facility for low-speed testing of cryo-engine applications

As a part of the ongoing Horizon 2020 ENABLEH2 project, a new low-speed compressor test facility is being constructed at the Chalmers University Laboratory of Fluids and Thermal Sciences. The ENABLEH2 project investigates critical technologies for cryogenic H2 applications in commercial aviation, including new combustion and heat management systems. This paper revolves around the design and construction of a core cooling flow facility which was commissioned to study and verify the potential benefits of incorporating a heat management system into the intermediate compressor duct (ICD).The test facility is designed to operate continuously at rotor midspan chord Reynolds number up to 600,000 to allow for detailed aerothermal studies at a technical readiness level four. The two-stage axial compressor is representative of the low-pressure compressor and ICD of a mid-size commercial jet engine. The compressor is powered by a 147kW electric motor at 1920 RPM. The mass-flow and pressure ratio are controlled by restricting valves located at the inlet of the facility. A compact volute settling chamber, with an integrated thermal control system is used to control the inlet temperature and remove flow non-uniformities downstream the restrictor valves before entering the compressor. At the compressor inlet, a turbulence mesh is mounted to increase the turbulence intensity levels to 3-4% at the leading edge of the variable inlet guide vanes. The compressor is mounted vertically to allow for easy access to the downstream ICD and mitigate non-axisymmetric mechanical loads. The compressor unit allows for optical and traverse access at two +- 9-degree sectors for all the rotor-stator interfaces. Upstream the OGV, there are four independent $\pm$ 180-degree access traverse systems. In the ICD, measurements are carried out by a single ABB robot with a U-shaped probe mount, providing full volume probing access of the ICD. At the first design iteration the ICD is designed to be instrumented with multi-hole probes, hot-wire anemometry and heat transfer measurement using IR-thermography.The paper describes the facility and the process of achieving a high case similarity (engine representative) while maximising the quality of the experimental data over a large test domain, targets that often produce conflicting design demands

Assessment of CO2 and NOx emissions in intercooled pulsed detonation turbofan engines

In the present paper, the synergistic combination of intercooling with pulsed detonation combustion is analyzed concerning its contribution to NOx and CO2 emissions. CO2 is directly proportional to fuel burn and can, therefore, be reduced by improving specific fuel consumption and reducing engine weight and nacelle drag. A model predicting NOx generation per unit of fuel for pulsed detonation combustors, operating with jet-A fuel, is developed and integrated within Chalmers University\u27s gas turbine simulation tool GESTPAN. The model is constructed using CFD data obtained for different combustor inlet pressure, temperature and equivalence ratio levels. The NOx model supports the quantification of the trade-off between CO2 and NOx emissions in a 2050 geared turbofan architecture incorporating intercooling and pulsed detonation combustion and operating at pressures and temperatures of interest in gas turbine technology for aero-engine civil applications

Fluorescent Molecular Photoswitches for the Generation of All-Optical Encryption Keys

Herein, we report a tri-component photochromic molecular cocktail that can be used to encrypt and decrypt information. The time-dependent fluorescent response of this cocktail is highly non-linear with respect to the set of inputs used (concentrations of the three photochromic components, excitation- and emission wavelengths), a property required for the generation of so-called encryption keys. The all-optical system can generate more than 80 million unique fluorescence responses by applying different input combinations and is operated using a conventional fluorimeter

Feasibility Study of a Radical Vane-Integrated Heat Exchanger for Turbofan Engine Applications

The density of liquid hydrogen (LH2), at the normal boiling point, is two times higher than that of highly compressed hydrogen. This makes LH2 the prime candidate for hydrogen storage in aviation. However, LH2 is stored at cryogenic temperatures that require adequate insulation, as well as the integration of heat exchangers to warm up the hydrogen on its way to the combustion chamber. Ideally, the required heat exchangers are strategically placed in the engine core to produce optimum heat management, thus improving the engine efficiency, increase its durability as well as to reduce emissions. Moreover, the combination of hydrogen high specific heat with cryogenic temperatures results in formidable cooling capacity, that can be explored by more compact HEX solutions. The present work numerically investigates a novel concept of a compact compressor vane-integrated heat exchanger, for application in cryogenically fuelled gas turbine engines. The baseline engine used for establishing the HEX requirements is a large geared turbofan, operating on liquid hydrogen. The HEX aero-thermal performance is first estimated using zero-dimensional models and Chalmers in-house gas turbine performance tool GESTPAN. After, the conceptual design of an outlet guide vane-HEX is developed and integrated into a three-stage low-pressure compressor. The baseline compressor geometry is a lightly loaded high-speed booster with a design pressure ratio of 2.8. The multi-stage compressor with the integrated HEX is evaluated using steady-state computational fluid dynamics. Results allow to estimate the heat exchanger performance in terms of total pressure loss, heat transfer effectiveness, and the potential enhanced radial flow turning capability. Further, the impact of the new developed OGV-HEX on the compressor characteristics is also reported and discussed

Over-wing integration of ultra-high bypass ratio engines: A coupled wing redesign and engine position study

The integration of next-generation high-bypass turbofan engines poses a major challenge to the aeronautical industry due to the larger fans necessary to achieve more fuel-efficient engines. The limited space underneath the wings and the strict ground clearance constraints bring the necessity to investigate solutions other than the conventional under-wing mounted engines. Over-wing installed nacelles have the potential to solve the ground clearance issue and, in addition, might reduce ground noise due to acoustic shielding from the wing. Nevertheless, a strong and complex coupling between aerodynamics and propulsion is the result of such integration choice, and traditional design practices may result in configurations with prohibitively high drag penalties.This paper presents a novel wing redesign method, specifically developed for over-wing mounted engines. The wing is reshaped to recover the spanwise lift distribution of the clean airframe (wing-body) configuration, for a single aisle airliner at a cruise condition. The wing redesign is conducted along with an engine position sensitivity study, in which the wing is reshaped for different engine axial and vertical positions. The coupling between propulsion and aerodynamics is thoroughly investigated, as well as the interaction and interference effects between the wing, pylon, and nacelle. Moreover, the best over-wing solution is compared to a baseline under-wing mounted nacelle. Results show that, by applying the developed method, an overall drag reduction of 17.65 counts, or 6.4%, was obtained, compared to the initial over-wing configuration, comprising the original wing and baseline engine position. Nonetheless, the best over-wing nacelle design is still 5.58 counts, or 2%, higher in overall drag compared to the baseline under-wing mounted nacelle case

The heat transfer potential of compressor vanes on a hydrogen fueled turbofan engine

Hydrogen is a promising fuel for future aviation due to its CO2-free combustion. In addition, its excellent cooling properties as it is heated from cryogenic conditions to the appropriate combustion temperatures provides a multitude of opportunities. This paper investigates the heat transfer potential of stator surfaces in a modern high-speed low-pressure compressor by incorporating cooling channels within the stator vane surfaces, where hydrogen is allowed to flow and cool the engine core air. Computational Fluid Dynamics simulations were carried out to assess the aerothermal performance of this cooled compressor and were compared to heat transfer correlations. A core air temperature drop of 9.5\ua0K was observed for this cooling channel design while being relatively insensitive to the thermal conductivity of the vane and cooling channel wall thickness. The thermal resistance was dominated by the air-side convective heat transfer, and more surface area on the air-side would therefore be required in order to increase overall heat flow. While good agreement with established heat transfer correlations was found for both turbulent and transitional flow, the correlation for the transitional case yielded decent accuracy only as long as the flow remains attached, and while transition was dominated by the bypass mode. A system level analysis, indicated a limited but favorable impact at engine performance level, amounting to a specific fuel consumption improvement of up to 0.8\ua0% in cruise and an estimated reduction of 3.6\ua0% in cruise NOx. The results clearly show that, although it is possible to achieve high heat transfer rate per unit area in compressor vanes, the impact on cycle performance is constrained by the limited available wetted area in the low-pressure compressor

The Full Two-Loop R-parity Violating Renormalization Group Equations for All Minimal Supersymmetric Standard Model Couplings

We present the full two-loop $\beta$-functions for the minimal supersymmetric standard model couplings, extended to include R-parity violating couplings through explicit R-parity violation