The objective of this thesis was to further the validation effort on the SU2 flow solver for non-ideal compressible flows. To do so, an uncertainty quantification infrastructure based on the V&V20 validation standard was developed. To determine whether a model error was present, the different sources of uncertainty were combined and then compared to the error between the SU2 simulations and the experiments. A variety of paradigmatic test cases were proposed which, together, would constitute a robust validation of the SU2 flow solver. Two paradigmatic unit test cases were analyzed; namely, a supersonic inviscid flow and a Mach 2.0 flow over a 2.5 degree wedge. The operating conditions of the experiments were as follows: an inlet total temperature and pressure of T_0=252°C and P_0=18.4 bara, and a back pressure of P_out=2.1 bara, for the first case, and T_0=180°C, P_0=3.5 bara and P_out=1.0 bara, for the second. The solver is able to predict the shock wave angle accurately. This step towards the validation was successful because the calculated total expanded uncertainty of 1.79% is higher the comparison error of 0.57%.In the second part of the thesis, the uncertainty quantification infrastructure was adapted to a test case constituted by more complicated flow features; namely, a supersonic flow through a 5-channel blade row. The computed uncertainties were on the same order of magnitude as in the supersonic inviscid flow test case. The simulations were verified with state-of-the-art CFD software for the quantities pressure and the Mach number. The positive result of the validation represents a step forward in the validation of the flow solver for non-ideal turbomachinery cases. The adaptation of the infrastructure to the cascade blade row paves the way for complex cases and for system response quantities of interest in industrial applications of CFD software, such as efficiency, to be assessed.

Water accumulating in the fuel tanks of any aircraft presents an unacceptable safety hazard. This accumulation, which is due to a combination of physical phenomena, is difficult to assess and therefore not well known. The purpose of this project is the development of a lightweight computational prediction method for water accumulation in helicopter fuel tanks. This model delivers a better understanding of the physical mechanisms involved and allows prediction of the accumulated water quantity under given conditions.

The shipping industry has a notable share in global greenhouse gas emissions and other pollutants such as sulphur and nitrogen oxides. Fuel cells and batteries are identified as relatively new technologies for shipping with high potential and hydrogen is also considered as one of the most promising sustainable fuels, especially for smaller vessels. This research contributes to three identified knowledge gaps: (1) the potential of hydrogen propulsion for high-speed craft, (2) the hybridisation of fuel cells and batteries for marine applications and (3) the characteristics of the response of a hybrid fuel cell/battery propulsion system under transient loads. The objective of this research is to analyse these aspects based on a series of time domain simulations of various operational conditions. A mathematical model of a fuel cell/battery propulsion system is developed in Matlab/Simulink. The developed model is used to analyse the energy consumption for various operational conditions of a test vessel. Based on this analysis, two configurations of fuel cell power and battery energy are selected. If the vessel sails at top speed, the fuel cell power stacks operate at maximum power and the battery operates as power booster. A strong correlation was found between the endurance at top speed and the battery size which is selected. A larger battery has a positive effect on endurance, but it also increases the displacement of the vessel significantly and, hence, required power. Fuel cells are least responsive and these should be protected against high fluctuations in a short time. A fuel cell can only follow low-frequency transient loads. The battery is required to support in high-frequency load changes. Contrary to the fuel cell, both the battery and PMSM were found to have very favourable characteristics in transient conditions. Finally, it is concluded that it is feasible to implement fuel cell/battery propulsion on high-speed craft. It is proposed that the fuel cell and hydrogen deliver the majority of the energy and use the battery as power booster and for transient support. Novel energy management strategies can deliver high system efficiencies in both full and part load and this is one of the main advantages of hybridisation. The implementation of a fuel cell/battery system does, however, come at significant costs in terms of endurance and top speed due to the low volumetric energy density of hydrogen. It should be acknowledged that the functionality of the vessel is reduced. In addition to this, the storage of hydrogen requires some deck space, so the cargo capacity in terms of crew and material is also reduced. Therefore, it is recommended to redefine the user profile of the vessel.

This study analyses the feasibility of an engine architecture using bypass cooled cooling air as a method for reducing specific fuel consumption of current and future high bypass turbofan engines. As cooled cooling air reduces required turbine cooling massflow, a major source of loss in modern aeroengines, it is believed that the concept can improve engine efficiency. No extensive or explicit study on the merits of this concept has been performed, however. Using the 0-D engine analysis software GSP, engine performance parameters at Take-Off and Cruise, such as, specific fuel consumption and (specific) thrust were evaluated against altering feed cooling air temperature by 0 to -300K and heat exchanger induced pressure losses of 0 to 8% in the bypass. This was done for two test cases; the Leap-1A engine (TOC OPR 50, CRZ BPR 11.1, TO FN 121kN) representing current conventional technology and GTF2050, a geared turbofan engine (TOC OPR 75, CRZ BPR 17.1, TO FN 174kN) with entry into service of 2050. For the Leap-1A engine the specific fuel consumption increased up to 1.9% at cruise and for GTF2050, the increase was up to 4.1%. It is shown that the change in fuel consumption is linear with the decrease in cooling fraction, as for both engines the specific fuel consumption increases by +0.34% per percent cooling air reduction. With a reduction in cooling fraction, the exhaust pressure of the core increases, resulting in a higher thrust (up to 2.3%). It is shown that the optimal take-off bypass ratio for minimum fuel consumption shifts up, for the GTF2050 engine from 16.4 to 17.5. Furthermore, scenario tests and an exergy analysis were performed to find that the impact of different mechanisms; the pressure loss in heat exchanger has minor impact on performance; change in turbine efficiency has small impact; the effect of changed turbine massflow and heat rejection into the bypass are the dominant phenomena. It is concluded that as a method for reducing fuel consumption, cooled cooling air with the bypass as a heat sink is not feasible for conventional architectures even with extreme design parameters such as high OPR and BPR. Heat rejection to the bypass cannot be effectively utilised and no improvement in core efficiency from reduced cooling air can compensate. In the edge case where there is no heat transfer in cruise, there is an observed specific fuel consumption benefit of up to 4%. The achievable benefit will be lower, however, when accounting for installation penalties. It is recommended to focus turbine cooling studies on the impact and feasibility of active cooling massflow control without heat rejection, investigate alternative heat sinks for cooled cooling air (e.g. cryogenic fuel), and only consider bypass cooled cooling air as last resort when up-flowing cooling schemes is not permissible or ineffective.

The study of compressible fluid dynamics has traditionally focused on flows of gases whose thermodynamic properties are related according to the ideal-gas law. In this context, for a long time, it has been demonstrated that shock waves in gases are exclusively of the compressive type, characterized by a discontinuity across which the fluid pressure rapidly increases. However, in the 1940s, world-renowned scientists such as Bethe and Zel’dovich put forth the theoretical possibility of the formation of rarefaction shock waves (RSWs) if the fluid is a high molecular complexity compound and its thermodynamic state is that of a dense vapour. Across such a RSW, the flow experiences an abrupt drop in pressure. The theoretical concept of RSWs became more known and gained widespread acceptance when further investigations were conducted in the 1970s by Thompson and his colleagues. They introduced the fundamental derivative of gasdynamics Γ, the caloric fluid property that determines the nature of shock waves that can occur in a flow depending on the molecular complexity of the fluid and its thermodynamic state. To acknowledge the significant contributions of the aforementioned scientists to this field of fluid mechanics, fluids that possess the unique characteristic of theoretically admitting RSWs due to the occurrence of thermodynamic states featuring Γ < 0 in the dense-vapour phase are referred to as BZT fluids. The branch of fluid dynamics dealing with fluid flows that might display characteristics that are radically different or even opposite to those of classical gas dynamics is aptly called nonclassical gasdynamics. Despite extensive theoretical knowledge of nonclassical gas dynamics, which includes rarefaction shock waves (RSWs), there is still a lack of compelling experimental evidence supporting their existence. The motivation for the research documented in this dissertation is two-fold: firstly, it is crucial to conduct experiments that can provide empirical validation of nonclassical gas dynamics, with a specific focus on observing RSWs, which have proven elusive in previous attempts. Secondly, performing accurate measurements of fluid properties in the dense-vapour thermodynamic regime has the potential to improve the thermodynamic models of BZT fluids or fluids made of complex organic molecules in general. This in turn can contribute to a more accurate characterisation of flows in practical applications that involve these fluids, such as turbine flows in Organic Rankine Cycle (ORC) systems or compressors in high temperature heat pumps. This research work aimed to provide conclusive experimental evidence for the existence of nonclassical expansion shock waves in the flows of a candidate BZT fluid, siloxane D6. For this purpose, two novel test facilities namely the Asymmetric Shock Tube for Experiments on Rarefaction Waves (ASTER) and the Organic Vapour Acoustic Resonator (OVAR) have been conceived, developed, designed, built and commissioned at TU Delft. Relevant theoretical studies were performed to complement the experimental observation of nonclassical effects. Novel measurements of fluid properties in the nonclassical gasdynamic region of the candidate BZT fluid were executed, the outcomes of which are useful for the improvement and the optimisation of thermodynamic models for this fluid. @en

The vast number of pioneering theoretical developments inthe area of non-classical gas dynamics together with the rising number ofapplications of organic Rankine cycle (ORC) technology have shaped a new branchof fluid mechanics called non-ideal compressible fluid dynamics (NICFD). Thisfield of fluid mechanics is concerned with flows of dense vapors, whoseproperties do not comply with the ideal gas model. These types of flows occurin dense vapors, supercritical fluids and liquid-vapor mixtures. NICFD is encountered in a variety of industrial processes,the most relevant in the power and propulsion sector, and is of interest forfundamental research.  Chapter 2documents an extensive literature review which covers the main developments inthe numerical, theoretical and experimental areas. In particular, the review ofcurrent and past experiments was aimed at summarizing the lessons learned.Despite the relevance of NICFD applications, experimental information regardingthis type of flows is scarce, due to the challenges inherent with the operatingconditions of such experiments. The main objective of the research documented in thisdissertation was to perform accurate measurements of NICFD flows which can thenbe used to assess the predictive capabilities of state-of-the art numericaltools. To this end, the design and commissioning of suitable and fullyinstrumented facilities capable of generating NICFD flows in a multitude ofsteady, controlled conditions is necessary in order to provide high-quality andwell characterised data. Arguably, state-of-the-art optical techniques are mostsuited for this goal, together with more conventional temperature, pressure andmass flow rate measurements.Advanced laser diagnostic techniques such as particle imagevelocimetry (PIV) are possibly the measurement technique of choice whenaccurate measurements with a high spatial and temporal resolution are needed.However, the use of PIV or other optical techniques capable of providing localand instantaneous information within the flow is not documented. Therefore, afeasibility study was conducted by means of a simpler experiment:  the planar PIV technique was applied tocharacterise the dense vapor of an organic fluid (D4, a siloxane) stirred withina transparent container. Chapter 3 documents the successful results of thisexperiment. The optical properties of the dense vapor make PIV possible.Titanium dioxide (TiO2) seeding particles were used to track the low-speed motionof the fluid around a rotating disk. Vector fields of the natural convectionflow and of the superposition of natural convection and rotating flow wereacquired and studied as exemplary cases. The particles adequately trace theflow since the calculated Stokes number is 6.5×10-5. The quality ofthe experimental data was assessed by means of particle seeding density andparticle image Signal to Noise ratio (S/N). The results are deemed acceptablein view of envisaged high-speed flow experiments. In order to obtain measurement data of high-speed vaporflows in the NICFD regime, new experimental facilities must be conceived,designed, realized and tested. Chapter 4 presents the organic Rankine cyclehybrid integrated device (ORCHID), which was designed, built and commissionedat the Delft University of Technology. The facility can operate continuouslyand with a wide range of operating conditions. The maximum operating pressureand temperature are 25 bara and 350 °C. The facility has been designedto operate with siloxane MM as the working fluid, but it was numericallyverified that it may also be operated with other working fluids such as MDM, MD2M,D4, D5, D6, pentane, cyclopentane, NOVEC649, PP2, PP80, PP90, and toluene. Twotest sections allow to operate the ORCHID either as a supersonic/transonicvapor tunnel or as an ORC turbine test bed. Currently, a supersonic nozzlefeaturing a throat of 150 mm2 with optical access allows to perform gasdynamic experiments for the validation of numerical simulation codes. A secondtest section, a test-bench for mini-ORC expanders,  is being designed and will accommodate afully instrumented 10 kWe machine, however machines of any configuration andwith a rated power of up to approximately 80 kWe can be tested. Chapter 5 documents the achievements reached during thecommissioning of the ORCHID. The successful commissioning of the setup with MMas the working fluid is detailed and discussed based on the recordings ofseveral test runs, including the start up and shut down of the facility.  Data were acquired during the operation atsteady state at the two main operating conditions typical of supersonic nozzleand ORC turbine tests. The operation of the facility is characterized withregards to the process stability, moreover process variables are assessed fortheir uncertainties. The correct operation of the nozzle test section wasverified with a mass flow rate of fluid of m = 1.15 kg / s, and at a thermodynamic state at the nozzle inletcorresponding to T = 252 °C and P =18.36 bara. The test sectionconditions typical of a turbine experiment were T = 275 °C, P =20.8 bara, with a mass flow rate of m = 0.17 kg / s. All therelevant process variables of the test section are affected by a relativeuncertainty that is lower than 0.6 %.Chapter 6 reports the results of the first supersonic nozzleexperiments. Schlieren images of the MM flow through the two-dimensionalconverging-diverging nozzle with the inlet in the NICFD regime were recorded,together with the static pressure profile along the nozzle. A series ofschlieren photographs displaying Mach waves in the supersonic flow wereobtained and are documented at two operating conditions, namely, for inletconditions corresponding to a stagnation temperature and pressure of T0  = 252 °C and P0 = 18.4 bara, and to a back pressure of 2.1bara. Furthermore, static pressure values were measured along the expansionpath for operating conditions given by T0 = 252 °C and P0 = 11.2 bara at the nozzle inletand by a back pressure of 1.2 bara. The two inlet conditions of the fluidcorrespond to a compressibility factor of Z0 = 0.58 and Z0 = 0.79.These Mach number values together with the values of thestatic pressure along the top and the bottom profile of the nozzle were usedfor a first assessment of the capability of evaluating NICFD effects occurringin dense organic vapor flows by comparison with the results of CFD simulations.The outcome of this initial comparison was deemed satisfactory.Chapter 7 introduces the first steps towards the validationof a CFD solver for non-ideal compressible flows. In particular, anindustry-standard validation method was used together with syntheticexperimental data (experimental data were not available yet) to illustrate, asan exercise, how the uncertainty of NICFD software can be quantified. Theassessment is limited to determining how the uncertainties in model inputs,e.g., fluctuations in boundary conditions and thermodynamic property modelsinfluence the overall accuracy of NICFD simulations. The assessment of theuncertainty of the other sub-models is left for a successive phase of thisresearch program. The validation exercise confirmed the applicability of theproposed method, but also pointed out that the adopted validation metricsshould be complemented with additional statistical indicators. The errorsources in the designed experiment are identified and all the uncertainties areadequately quantified.The final chapter summarizes the answers to the researchquestions listed in the first chapter, above all that the ORCHID facility wassuccessfully commissioned and can generate stable dense vapor flows of organicfluids for both fundamental gas dynamic experiments and ORC turbine testing.The first experiments demonstrate that it can be used to obtain accurateoptical and non-optical measurements of supersonic nozzle flows for thevalidation of CFD codes, including flows in the NICFD regime.  An overview of the next phases of theresearch program is also provided.@en

Over the years, aero engines have evolved into the efficient turbofans present on commercial airliners today. Although these engines are very reliable, they still experience degradations in performance and reductions in component health. The degradation affects the operation of the engine, which can be measured using the pressure, temperature, and rotational speed sensors. Using accurate engine models together with engine sensor measurements, the condition of individual components can be determined. Surrogate models of a non-linear Gas Path Analysis model have been developed for the GEnx-1B turbofan in the form of High Dimensional Model Representations. It is determined that the surrogate models developed are able to determine component conditions with a high accuracy and low computational complexity. The models are able to properly identify the effects of water-washes and turbine failures when applied to real-world on-wing data. Due to the low computational complexity of the models, they provide the possibility for fleet-wide continuous engine diagnostics.