The paper presents a numerical study where a hybrid CFD-Chemical Reactor Network (CRN) approach is used to predict pollutant emissions in a tubular combustor for aero-engine applications. A ...fully-automated clustering of the simulated flow field with the generation of a reactor network representative of the main flow features is exploited. Similar cells are detected and grouped using a two step approach, the first one based only on aerodynamic criteria for turbulent flows followed by a chemical refinement based on mixture fraction. A formulation for turbulent diffusion fluxes is introduced in the reactor code to model species and energy exchanges between reactors. Three different operating conditions are studied for which measured NOx and CO are available. Results highlight the importance of including turbulent diffusion in the network solution. The accurate prediction of pollutant emissions at different load points confirms that CFD-CRN is a valid and flexible approach for preliminary assessment of aero-engine combustor emissions in the design phase.
Abstract
The development of cost-effective energy storage systems with low environmental impact is crucial for the energy transition to enable the widespread use of renewable energy sources. Within ...this context, there is an increasing interest in Compressed Air Energy Storage (CAES), especially for its potential application in small-scale off-grid systems. In this study, a numerical model of a micro-CAES system for off-grid applications, with an output power of
5kW
, is developed; the open source, object-oriented software OpenModelica is used and the model is validated by comparison with available experimental data. Following the validation, the model is used to identify the main exergetic losses and a series of efficiency enhancing solutions are evaluated, using the round-trip efficiency as an indicator. The study allows to identify the main technical aspects to focus on, in ordedr to improve the system, as well as the limit performance that the adopted CAES concept would allow to achieve.
► Measurements of adiabatic effectiveness on an a real combustor liner cooling scheme. ► Thermochromic Liquid Crystal (TLC) and Pressure Sensitive Paint (PSP) were employed. ► Evaluation of the ...cooling system performance and comparison between the techniques. ► Effusion system allows an effective liner protection except for the first rows. ► Use of PSP reduces the experimental uncertainties respect to TLC.
Due to the cooling requirements of high thermal loaded components of modern gas turbine a detailed analysis of the film cooling performance plays a major role in order to optimize coolant consumption and guarantee an effective wall protection. Nowadays several techniques are available to measure the film cooling effectiveness: Thermochromic Liquid Crystal (TLC) was successfully used to measure the surface temperature and hence to estimate the film effectiveness, while Pressure Sensitive Paint (PSP) has been recently applied to film cooling applications.
In the present study PSP and TLC based techniques were applied in order to measure the adiabatic effectiveness of a multi-perforated plate, which reproduces an effusion array of a real combustor liner. Experiments were carried out imposing several effusion blowing ratios within a range of typical modern engine working conditions (BReff=1.5; 3; 5; 7).
Both techniques require a post-processing procedure in order to overcome specific issues. TLC measurements, because of the temperature differences among the mainstream, the coolant and the surface, are indeed affected by heat transfer problems due to the undesirable heat conduction through the plate. On the other hand PSP measurements, which rely on the mass transfer analogy, avoid inherent problems associated with heat transfer methods and thus allow to reduce measurement uncertainties.
Using a correct post-processing, adiabatic effectiveness results obtained thanks to of the two techniques, show a good agreement in terms of average values. However PSP technique is able to capture more detailed 2D maps.
This paper describes an experimental study for a 30:1 scaled model reproducing an innovative wedge shaped discharge trailing edge (TE) cooling scheme. Three configurations were investigated: Smooth, ...Ribs +60° and Ribs −60° with both closed and open tip. Thermochromic Liquid Cristal TLC technique was used to measure the heat transfer coefficient, for a Reynolds number between 10,000 and 40,000 in the stationary condition. The results reveal a direct effect of the Reynolds number and the configurations of cooling scheme on the heat transfer coefficient. Cooling efficiency is influenced by the ribs, the tip configuration and the flow regime. The average Nusselt number at the inlet duct region L0 and the exit trailing edge L1 region is correlated firstly based only on the Reynolds number and secondly on the Reynolds number, Prandtl number and a fraction of blade height. The derived correlations may serve in assessing the effectiveness of blades TE cooling systems.
•Investigation of innovative cooling schemes of a wedge shaped discharge trailing edge of a gas turbine blade.•Measurement of heat transfer coefficient by means of the Thermochromic Liquid Cristal technique.•Cooling efficiency is influenced by the ribs and tip configuration and the flow regime.•Nusselt number is correlated against Reynolds number, Prandtl number and fraction of blade height.
The introduction of highly active antiretroviral therapy (ART) has deeply modified the outcome of HIV patients by improving their overall survival and ameliorating their quality of life (QoL). The ...prolongation of these patients' survival has led to an increased risk of highly diffused non-infectious diseases, e.g., cardiovascular diseases, endocrine disease, neurological diseases, and cancer. The management of antiretroviral therapy and anticancer agents (AC) can be challenging, due to the possible drug-drug interactions (DDI) between AC and ART. For this reason, a multidisciplinary approach is always preferred as demonstrated by the GICAT (Italian Cooperation Group on AIDS and Tumors). This review aims to analyze the current scientific data regarding the possible effects of ART on the management of HIV-positive cancer patients and to evaluate the possible DDIs that must be taken into consideration when co-administrating ART and AC. A collaboration between all the involved professional figures, particularly infectious disease specialists and oncologists, represents the key to the correct managing of these patients in order to guarantee the best oncological outcome possible.
The present work presents a numerical analysis of a low NOx partially premixed burner for heavy duty gas turbine. The first part of the paper is focused on the study of the premixing process inside ...the burner using standard RANS CFD approach. The resulting profiles at different test points have been used to perform reactive simulations of an experimental test rig, where exhaust NOx emissions were measured. A reliable numerical setup was found comparing predicted and measured NOx emissions at different operating conditions and split ratios between main and pilot fuel. The calibrated numerical setup was then employed to explore possible modifications to fuel injection criteria and fuel split, with the aim of minimizing exhaust NOx emissions. This preliminary numerical screening of new fuel injection strategies, allowed defining a set of advanced configurations to be investigated in future experimental tests.
In order to meet the increasingly stringent regulations in terms of pollutant emissions adopted by ICAO-CAEP in last years, a redesign of aero-engine combustors has been required and, today, lean ...combustion technology can be considered as the most effective solution. In this context, common design tools and standard RANS predictive techniques are often not capable of properly characterizing combustors performances. Thus, computational techniques have been rapidly evolving towards an extensive use of Large-Eddy Simulation (LES) or hybrid RANS methods. This paper presents the numerical analysis of an experimental partially premixed flame fed by a dilute spray of acetone1, exploiting a two-phase Eulerian-Lagrangian approach combined with the Flamelet Generated Manifold (FGM) combustion model in the context of LES techniques. All simulations have been performed with thecode Ansys Fluent 15.0.
A comparison both in non-reactive and reactive conditions of the obtained results with experimental data and conventional RANS solution has been realized in order to highlight the LES capabilities to give a new insight into the physics of reactive two-phase flows, particularly on the unsteady evolution of turbulent spray flames involving particles dispersion, evaporation and combustion.
Objective: Awake breast surgery has been proven to be a concrete alternative to surgery under general anesthesia. This technique was shown to be advantageous in various aspects such as length of ...hospitalization and economic sustainability. Our study aims to verify the advantages of this technique in terms of operating room times, length of stay, and outcome in frail patients diagnosed with breast cancer. Patients and methods: Our retrospective study enrolled all frail patients, ASA ≥ 3, diagnosed with breast cancer and scheduled to undergo a surgical intervention. The type of surgery, duration of surgery, length of hospital stay, type of anesthesia, postoperative complications, postoperative dissociative episodes and CCI (Charlson Comorbidity Index) score were evaluated by comparing the data between the group of awake surgery and the group of patients undergoing surgery under general anesthesia. Results: A total of 34 patients were enrolled; 16 patients (45.7%) undergoing awake surgery with a mean age of 78 years 75;95, and 18 patients (54.3%) receiving general anesthesia. CCI was significantly higher in the Awake group with a median score of 12 9;13 vs. 10 9;11 in the No-Awake group: relative p-value was <0.001. Postoperative complications were comparable between the groups, showing no statistically significant differences. Six patients (33.3%) in the general anesthesia group experienced dissociative complications vs. 1 (6.3%) in the awake surgery group (p=0.05). There were no statistically significant differences regarding the other parameters. Conclusions: Awake breast surgery in elderly patients, especially in frail ones, could reduce the incidence of postoperative delirium by enabling a shorter hospitalization and allowing for a faster recovery.
To date non-invasive (NIV) mechanical ventilation use is not recommended in chronic obstructive pulmonary disease (COPD) patients with acute respiratory failure (ARF) and pH < 7.30 outside a ...'protected environment'. We assessed NIV efficacy and feasibility in improving arterial blood gases (ABG) and in-hospital outcome in patients with ARF and severe respiratory acidosis (RA) admitted to an experienced rural medical ward.
This paper is a prospective pilot cohort study conducted in the General Medicine Ward of Budrio's District Hospital. Two hundred and seventy-two patients with ARF were admitted to our Department, 112, meeting predefined inclusion criteria (pH < 7.35, PaCO2 > 45 mmHg). Patients were divided according to the severity of acidosis into: group A (pH < 7.26), group B (7.26 ≤ pH < 7.30) and group C (7.30 ≤ pH < 7.35). ABG were assessed at admission, at 2-6 h, 24 h, 48 h and at discharge.
Group A included 55 patients (24 men, mean age: 80.8 ± 8.3 years), group B 31 (12 men, mean age: 80.3 ± 9.4 years) and group C 26 (15 men, mean age: 78.6 ± 9.9 years). ABG improved within the first hours in 92/112 (82%) patients, who were all successfully discharged. Eighteen percent (20/112) of the patients died during the hospital stay, no significant difference emerged in mortality rate (MR) within the groups (23%, 16% and 8%, for groups A, B and C, respectively) and between patients with or without pneumonia: 8/29 (27%) versus 12/83 (14%). On multivariable analysis, only age and Glasgow Coma Scale had an impact on the clinical outcome.
In a non-'highly protected' environment such as an experienced medical ward of a rural hospital, NIV is effective not only in patients with mild, but also with severe forms of RA. MR did not vary according to the level of initial pH.
Nowadays total inlet temperature of gas turbine is far above the permissible metal temperature; as a consequence, advanced cooling techniques must be applied to protect from thermal stresses, ...oxidation and corrosion the components located in the high pressure stages, such as the blade trailing edge. A suitable design of the cooling system for the trailing edge has to cope with geometric constraints and aerodynamic demands; state-of-the-art of cooling concepts often use film cooling on blade pressure side: the air taken from last compressor stages is ejected through discrete holes or slots to provide a cold layer between hot mainstream and the blade surface. With the goal of ensuring a satisfactory lifetime of blades, the design of efficient trailing edge film cooling schemes and, moreover, the possibility to check carefully their behavior, are hence necessary to guarantee an appropriate metal temperature distribution. For this purpose an experimental survey was carried out to investigate the film covering performance of different pressure side trailing edge cooling systems for turbine blades. The experimental test section consists of a scaled-up trailing edge model installed in an open loop suction type test rig. Measurements of adiabatic effectiveness distributions were carried out on three trailing edge cooling system configurations. The baseline geometry is composed by inclined slots separated by elongated pedestals; the second geometry shares the same cutback configuration, with an additional row of circular film cooling holes located upstream; the third model is equipped with three rows of in-line film cooling holes. Experiments have been performed at nearly ambient conditions imposing several blowing ratio values and using carbon dioxide as coolant in order to reproduce a density ratio close to the engine conditions (DR=1.52). To extend the validity of the survey a comparison between adiabatic effectiveness measurements and a prediction by correlative approach was performed to compare the experimental results with 1D methodologies.
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