DESIGN AND TESTING OF A MULTI-STAGE IP TURBINE FOR FUTURE GEARED TURBOFANS

The multi-stage intermediate pressure turbine (IPT) is a key enabler of the thermodynamic cycle in geared turbofan engine architectures, where fan and turbine rotational speeds become decoupled by employing a power gearbox between them. This allows for the separate aerodynamic optimization of both components, an increase in engine bypass ratios, higher propulsive efficiency, and lower specific fuel consumption. Due to significant aerodynamic differences with conventional low pressure turbines (LPTs), multi-stage IPT designs present new aerodynamic, mechanical and acoustic trade-offs. This work describes the aerodynamic design and experimental validation of a fully featured three-stage IP turbine, including a final row of outlet guide vanes. Experiments have been conducted in a highly engine-representative transonic rotating wind tunnel at the CTA (Centro de Tecnolog'as Aeron'uticas, Spain), in which Mach and Reynolds numbers were matched to engine conditions. The design intent is shown to be fully validated. Efficiency levels are discussed in the context of a previous state-of-the-art LPT, tested in the same facility. It is argued that the efficiency gains of IPTs are due to higher pitch-to-chord ratios, which lead to a reduction in overall profile losses, and higher velocity ratios and lower turning angles, which reduce airfoil secondary flows and three-dimensional losses.

Optimization and Comparison of Two Technologies for the Manufacture of Blades for Flow path HPC Turbine K-330-23.5

The article presents the results of multiparameter optimization of the structural and thermogasdynamic parameters of the flow path of the HPC K-330-23.5, obtained using the developed CAD “Turboagregat”. The found 12 optimal solutions for the flow path of the HPCK-330-23.5 make it possible not only to assess the effect of the design parameters and the number of blades of the HPC stages on the HPC efficiency, but also to carry out a comparative analysis of two technological approaches to manufacturing the rotor blades – with and without trimming the initial edges. Calculations have confirmed the negative effect of increasing the radius of the “tummy” circle on the nature of the flow and on the efficiency of the cascades. In cascades with increased profiles by 9.83 % with a radius of the “tummy” circle, the coefficient of profile losses of the cascade increased by 0.07 % (absolute) in comparison with the original cascade from the original 1MMK-U profiles.

Design and Testing of a Multi-Stage IP Turbine for Future Geared Turbofans

The multi-stage intermediate pressure turbine (IPT) is a key enabler of the thermodynamic cycle in geared turbofan engine architectures, where fan and turbine rotational speeds become decoupled by employing a power gearbox between them. This allows for the separate aerodynamic optimization of both components, an increase in engine bypass ratios, higher propulsive efficiency, and lower specific fuel consumption. Due to significant aerodynamic differences with conventional low pressure turbines (LPTs), multi-stage IPT designs present new aerodynamic, mechanical and acoustic trade-offs. This work describes the aerodynamic design and experimental validation of a fully featured three-stage IP turbine, including a final row of outlet guide vanes. Experiments have been conducted in a highly engine-representative transonic rotating wind tunnel at the CTA (Centro de Tecnologías Aeronáuticas, Spain), in which Mach and Reynolds numbers were matched to engine conditions. The design intent is shown to be fully validated. Efficiency levels are discussed in the context of a previous state-of-the-art LPT, tested in the same facility. It is argued that the efficiency gains of IPTs are due to higher pitch-to-chord ratios, which lead to a reduction in overall profile losses, and higher velocity ratios and lower turning angles, which reduce airfoil secondary flows and three-dimensional losses.

Fermentative profile, losses and chemical composition of silage soybean genotypes amended with sugarcane levels

The experiment aimed to evaluate the fermentative and nutritional profile of the silage of four soybean plant genotypes (BRS 333 RR, Pampeanas: C50, C60, and C70) ensiled with levels of sugarcane (0, 25, 50, 75, and 100%). The experiments were conducted in a completely randomized design, in factorial scheme 4 × 5 (four soybean genotypes and five levels of sugarcane inclusion) with four replicates. Silages with 100% soybean plant presented the highest levels of butyric acid (P < 0.001) and ammoniacal nitrogen (P < 0.047); however, the intermediate addition of sugarcane contributed to lactic fermentation (P < 0.001). Besides, there was a quadratic effect (P < 0.05) for the recovery of dry matter, which ranged from 83.28 to 95.29%, with higher values observed for silage with the same proportions of soybean plant and sugarcane. It was verified that the crude protein content exhibited decreasing linear effects (P < 0.001), varying among 4.60 to 7.48% in the silages. It was concluded that the highest recovery of dry matter, the best fermentation profile, and the highest levels of crude protein and digestibility occurred in the inclusion between 25 and 50% of sugarcane in soybean silage, with the superiority of the C50 soybean genotype.

A Bayesian Approach for the Identification of Cascade Loss Model Strategy

A Bayesian method has been used to identify the best model strategy to describe the profile losses of low pressure turbine (LPT) cascades operating under unsteady inflow. The model has been tuned with experimental data measured in a large scale cascade facility, equipped with a moving bar system. Tests have been carried out on two different cascades, investigating three different reduced frequencies, three mass flow coefficients and several Reynolds numbers (up to eight) per condition, accounting for an overall amount of 51 different combinations of these parameters for each cascade. The predictor functions included into the model have been varied starting from a classic polynomial formulation for each influencing parameter, and then with functional relationships mimicking physical constrains and loss tendencies. Different combinations of the predictors, also including different types and orders of the cross-terms, have been evaluated by means of a Bayesian model selection method searching for the maximum probability of the model in fitting the cloud of experimental data. In particular, the evaluation of the Model Evidence (ME) using the Bayesian Information Criterion approximation (BIC) has allowed obtaining sufficient accuracy and avoiding overfitting at the same time. The best model here identified will be shown to be able to well reproduce the loss surface of a third different cascade that does not participate to the model selection. Realistic profile loss evolutions outside of the design space tested are provided, thus also allowing for a generalization of the structure of the model for other applications and future works.

Profile Loss Investigations With a S-CO2 Axial Turbine Aerofoil

Axial turbines are being extensively designed for supercritical carbon-di-oxide (S-CO2) Brayton cycle power blocks. But very little information is available in the open literature on the aerodynamics of S-CO2 axial turbines, their aerofoils and loss mechanisms. The understanding of real gas behavior of S-CO2 inside a turbine is still very far from complete. Profile losses contribute to more than 50% of overall losses in a turbine. Hence, estimation of profile losses at the outset of the design process is very important. In the present study, the mean section aerofoil of the first stage of a 5 MWe Brayton cycle high temperature turbine is investigated for profile loss characteristics. The basic aerodynamic characteristics of the aerofoil in a linear cascade were initially studied using CFD simulations and cascade test experiments with air as the fluid medium. The aerofoil cascade is then subjected to numerical simulations with S-CO2 as the fluid medium. CFD simulations were carried out using a commercial RANS solver with SST k-ω turbulence model for closure. Air was modelled as ideal gas and S-CO2 was modelled as real gas with Refrigerant Gas Property tables generated over the appropriate pressure and temperature ranges using NIST Refprop database. Losses are also calculated using Craig and Cox loss model. Experiments were carried out by testing a linear cascade model comprising 12 two dimensional blades, in a high-speed cascade wind tunnel. Cascade tests were carried out over a range of exit Mach numbers and incidence angles with air as the working medium. Losses, flow deflection and blade loading were measured during the experiments. Scaling of the profile losses between air and S-CO2 fluid mediums were examined over a range of Mach numbers, Reynolds numbers and incidence angles. Detailed analysis of data generated from numerical simulations, experiments and loss model (mainly in the transonic regime) are discussed in this paper. Losses with S-CO2 was 1.5% lower than that of air while the flow deflection roughly remained the same.

Advances in axial turbine blade profile aerodynamics

The aerodynamic performance of axial turbines depends significantly on profile losses, secondary flow losses, and clearance gap losses of vanes and blades. In modern high-efficiency turbomachinery operating at various working conditions, profile losses are very important criteria for the development of vanes and blades, and turbine designers strive to minimize the losses, based on better understandings of flow and loss characteristics at various working conditions. This paper summarizes recent advances in the field of turbine blade profile aerodynamics, and covers: (1) flow and loss characteristics of blade profiles, (2) flow structure and loss mechanism for transonic blade profiles, (3) off-design performance, (4) flow control, (5) design and optimization, (6) engineering design considerations, and (7) research methods of blade profile aerodynamics. The emphasis is placed on flow characteristics and loss control methods, and present insights regarding the current research trends and the prospects for future developments.

Development of mathematical model and computer program for primary design of transonic axial compressor

The mathematical model underlying the program for calculating and designing axial compressors is presented. The process of calculating the pressure loss in the elements of the axial compressor stage flow path is described. The loss coefficient consists of losses on the limiting surfaces, secondary losses and profile losses. The effect of roughness on the pressure loss is taken into account by introducing the corresponding empirical coefficient. An algorithm for calculating the blades and vanes angles of the impeller and the guide apparatus is presented by calculating the incidence angle and the lag angle of the flow. The flow lag angle is the sum of the lag angle of the flow on the profile and the lag angle due to viscous flow on the limiting surfaces

New Insight Into Aspect Ratio's Effect on Secondary Losses of Turbine Blades

In view of improving the understanding of the loss mechanisms existing on a compact turbine driving a cryogenic engine turbo-pump for a satellite delivering rocket, a new perspective on how the aspect ratio of turbine blades affects the secondary and profile losses is presented. This perspective, originally based on published experimental data, is further developed by a series of back-to-back highly resolved computational fluid dynamics (CFD) numerical simulations, with the aim of acquiring further insight into the dynamics of the secondary vortices, and the intermediate boundary layer flow for varying blade heights. The main outcome redefines the extreme cases and the partition of losses between secondary and profile, and establishes a new critical ultra-low aspect ratio of 0.35 as a threshold distinguishing two different behaviors. The final venue of this new perspective is the possibility to further improve existing off-design turbine loss models, like those presented by Craig–Cox and Ainley–Mathieson.