Review and assessment of the database and numerical modeling for turbine heat transfer

The objectives of the NASA Hot Section Technology (HOST) Turbine Heat Transfer subproject were to obtain a better understanding of the physics of the aerothermodynamic phenomena and to assess and improve the analytical methods used to predict the flow and heat transfer in high-temperature gas turbines. At the time the HOST project was initiated, an across-the-board improvement in turbine design technology was needed. A building-block approach was utilized and the research ranged from the study of fundamental phenomena and modeling to experiments in simulated real engine environments. Experimental research accounted for approximately 75 percent of the funding while the analytical efforts were approximately 25 percent. A healthy government/industry/university partnership, with industry providing almost half of the research, was created to advance the turbine heat transfer design technology base

Measured and calculated wall temperatures on air-cooled turbine vanes with boundary layer transition

Convection cooled turbine vane metal wall temperatures experimentally obtained in a hot cascade for one vane design were compared with wall temperatures calculated with TACT1 and STAN5 computer codes which incorporated various models for predicting laminar-to-turbulent boundary layer transition. Favorable comparisons on both vane surface were obtained at high Reynolds number with only one of these transition models. When other models were used, temperature differences between calculated and experimental data obtained at the high Reynolds number were as much as 14 percent in the separation bubble region of the pressure surface. On the suction surface and at lower Reynolds number, predictions and data unsatisfactorily differed by as much as 22 percent. Temperature differences of this magnitude can represent orders of magnitude error in blade life prediction

Validation of a low field Rheo-NMR instrument and application to shear-induced migration of suspended non-colloidal particles in Couette flow.

Nuclear magnetic resonance rheology (Rheo-NMR) is a valuable tool for studying the transport of suspended non-colloidal particles, important in many commercial processes. The Rheo-NMR imaging technique directly and quantitatively measures fluid displacement as a function of radial position. However, the high field magnets typically used in these experiments are unsuitable for the industrial environment and significantly hinder the measurement of shear stress. We introduce a low field Rheo-NMR instrument (1H resonance frequency of 10.7MHz), which is portable and suitable as a process monitoring tool. This system is applied to the measurement of steady-state velocity profiles of a Newtonian carrier fluid suspending neutrally-buoyant non-colloidal particles at a range of concentrations. The large particle size (diameter >200μm) in the system studied requires a wide-gap Couette geometry and the local rheology was expected to be controlled by shear-induced particle migration. The low-field results are validated against high field Rheo-NMR measurements of consistent samples at matched shear rates. Additionally, it is demonstrated that existing models for particle migration fail to adequately describe the solid volume fractions measured in these systems, highlighting the need for improvement. The low field implementation of Rheo-NMR is complementary to shear stress rheology, such that the two techniques could be combined in a single instrument

Bioconversion of cellulose into bisabolene using Ruminococcus flavefaciens and Rhodosporidium toruloides

In this study, organic acids were demonstrated as a promising carbon source for bisabolene production by the non-conventional yeast, Rhodosporidium toruloides, at microscale with a maximum titre of 1055 ± 7 mg/L. A 125-fold scale-up of the optimal process, enhanced bisabolene titres 2.5-fold to 2606 mg/L. Implementation of a pH controlled organic acid feeding strategy at this scale lead to a further threefold improvement in bisabolene titre to 7758 mg/L, the highest reported microbial titre. Finally, a proof-of-concept sequential bioreactor approach was investigated. Firstly, the cellulolytic bacterium Ruminococcus flavefaciens was employed to ferment cellulose, yielding 4.2 g/L of organic acids. R. toruloides was subsequently cultivated in the resulting supernatant, producing 318 ± 22 mg/L of bisabolene. This highlights the feasibility of a sequential bioprocess for the bioconversion of cellulose, into biojet fuel candidates. Future work will focus on enhancing organic acid yields and the use of real lignocellulosic feedstocks to further enhance bisabolene production

MAGNETIC RESONANCE (MR) MEASUREMENTS OF THE MASS FLUX IN GAS-SOLID FLUIDIZED BEDS

Magnetic Resonance (MR) Imaging was used to measure the time-averaged voidage and particle velocity in a 3D gas-solid fluidized bed. Two different distributors were used. The mass-flux through a horizontal plane was calculated by combining the local voidage and particle velocity measurements. Based on the conservation of mass it was possible to give an error in the combined voidage and particle velocity measurements. It was found that the error in the mass flux was usually small (\u3c 5%), albeit increasing with increasing fluidization velocities

The structure and mechanistic impact of carbon deposits in dehydrogenation reactions

The catalytic dehydrogenation (DH) and oxidative dehydrogenation (ODH) of light alkanes is widely studied as a route to the formation of alkenes and di-alkenes, important precursor molecules for synthetic rubbers, plastics and a variety of other products [1-4]. Recent studies have focused on the non-oxidative DH of butane over alumina-supported vanadia catalysts [5-7]. In the present work, we provide a detailed understanding of both the role and structure of coke deposited on VOx/Al2O3 during reaction. A range of characterisation techniques have been employed including the first application of terahertz time domain spectroscopy (THz-TDS) to the study of coke. Complementary THz-TDS characterisation of carbonaceous materials including carbon nanofibres (CNFs) has also been conducted

The role and structure of carbonaceous materials in dehydrogenation reactions

The catalytic dehydrogenation (DH) and oxidative dehydrogenation (ODH) of light alkanes is widely studied as a route to the formation of alkenes and di-alkenes, important precursor molecules for synthetic rubbers, plastics and a variety of other products [1,2]. Recent studies have focused on the non-oxidative DH of butane over alumina-supported vanadia catalysts [3-5]. In the present work, we provide a detailed understanding of both the role and structure of coke deposited on VOx/Al2O3 during reaction. A range of characterisation techniques have been employed including the first application of terahertz time domain spectroscopy (THz-TDS) to the study of coke. Complementary THz-TDS characterisation of carbonaceous materials including carbon nanofibres (CNFs) has also been conducted. For such materials THz-TDS spectra can be correlated with their catalytic performance in the oxidative dehydrogenation of ethylbenzene to form styrene