The effect of inlet flow distortion on installed gas turbine performance.

Military aircraft are often subjected to severe flight manoeuvres with high Angles of Attack (AOA) and Angles of Sideslip (AOSS). These flight attitudes induce non-uniform in flow conditions to their installed gas turbine engines which may include distortion of inlet total pressure and total temperature at the Aerodynamic Interface Plane (AIP). When the downstream compression system of the engine experiences such distorted inflow conditions its operation is significantly affected in that its aerodynamic performance is reduced along with its stall margin. Also the blade stress levels of the compression system increase and vibration becomes an issue. A large, complex facility is required to accurately test how the actual engines response to such distorted conditions. In addition to the engine support facilities, a full-scale inlet is needed to house the engine and a large secondary air supply system is needed to generate flight speed and altitude conditions relative to the inlet. As it can be easily imagined, the cost of this type of full scale testing is remarkably high. The objective of the present study is to develop a numerical method for the estimation of the installed gas turbine engine performance variations due to airflow distortion. This method will also provide the means to assess the compatibility of an airframe-engine set at a specific operating envelope, given the geometry of the upstream intake and the performance simulation model of the under examination gas turbine engine. In the present work, the distorted conditions at the interface between the intake and the engine have been numerically calculated with Computational Fluid Dynamics (CFD), where 27 different aircraft flight attitudes have been tested. As a baseline set of airframe-engine, were chosen an airframe inspired by the General Dynamics/LMAERO F-16 aircraft, equipped with a Pratt and Whitney F100-PW-229-like gas turbine engine. Also, the specified flow field was resolved by a commercial CFD code. The steady state total pressure distortion induced to the AIP due to the aircraft's flight attitude was estimated in terms of distortion descriptors. These parameters were then correlated to the surge margin of the downstream compression system. Following this methodology, it was concluded whether each one of the tested flight attitudes induced enough distortion to the AIP so as to surge the engine's FAN. Also the engine's performance variations due to airflow distortion have been also estimated in terms of net thrust changes. The obtained results justify the anticipated behaviour of the engine with degraded performance, in terms of resulted net thrust, when the aircraft flies with Angle of Sideslip (AOSS). Having the FAN shaft rotational speed as the controlled parameter, the net thrust percentage change between the uninstalled condition of the engine with rather uniform inflow and that when the engine is installed and exposed to different flight attitudes varies between -1.76% to -22.56% depending on the flight Mach number and the aircraft's flight attitude. Finally, all the results were combined and performance maps have been created that correlate the aircraft's flight attitude with the engine's net thrust.PhD in Aerospac

Numerical simulation of the airflow over a military aircraft with active intake

The aim of the study presented herein is to numerically predict the behaviour of the airflow around a flying military aircraft with an active intake in which the airflow may enter and travel all the way up to the aerodynamic interface plane (the analytical interface between the inlet and engine). Computational fluid dynamics is used as the basic tool. The geometry created consists of a full-scale military aircraft exposed to different flight conditions. The flow results are mainly focused at the aerodynamic interface plane since the present study is a part of a greater research effort to estimate how the airflow distortion induced to the engine’s face due to the aircraft’s flight attitude, affects the embedded gas turbine’s performance. The obtained results were validated through a direct comparison against similar experimental ones, collected from a wind tunnel environment

Stability assessment of an airflow distorted military engine’s FAN

Military aircraft are often subjected to severe flight maneuvers with high angles of attack and angles of sideslip. These flight attitudes induce non-uniformity in flow conditions to their gas turbine engines, which may include distortion of inlet total pressure and total temperature at the aerodynamic interface plane. Operation of the downstream engine’s compression system may suffer reduced aerodynamic performance and stall margin, and increased blade stress levels. The present study presents a methodology of evaluating the effect of inlet flow distortion on the engine’s fan stability. The flow distortion examined was induced to the aerodynamic interface plane by means of changing the aircraft’s flight attitude. The study is based on the steady-state flow results from 27 different flight scenarios that have been simulated in computational fluid dynamics. As a baseline model geometry, an airframe inspired by the General Dynamics/LMAERO F-16 aircraft was chosen, which has been exposed to subsonic incoming airflow with varying direction resembling thus different aircraft flight attitudes. The results are focused on the total pressure distribution on the engine’s (aerodynamic interface plane) face and how this is manifested at the operation of the fan. Based on the results, it was concluded that the distorted conditions cause a shift of the surge line on the fan map, with the amount of shift to be directly related to the severity of these distorted conditions. The most severe flight attitude in terms of total pressure distortion, among the tested ones, caused about 7% surge margin depletion comparing to the undistorted value

Remote operation and monitoring of a micro aero gas turbine

Internet applications have been extended to various aspects of everyday life and offer services of high reliability and security at relatively low cost. This project presents the design of a reliable, safe and secure software system for real-time remote operation and monitoring of an aero gas turbine with utilisation of existing internet technology, whilst the gas turbine is installed in a remote test facility This project introduces a capability that allows remote and flexible operation of an aero gas turbine throughout the whole operational envelope, as required by the user at low cost, by exploiting the available Internet technology. Remote operation of the gas turbine can be combined with other remote Internet applications to provide very powerful gas-turbine performance-simulation experimental platforms and real-time performance monitoring tools, whilst keeping the implementation cost at low levels. The gas turbine used in this experiment is an AMT Netherlands Olympus micro gas turbine and a spiral model approach was applied for the software. The whole process was driven by risk mitigation. The outcome is a fully functional software application that enables remote operation of the micro gas turbine whilst constantly monitors the performance of the engine according to basic gas turbine control theory. The application is very flexible, as it runs with no local installation requirements and includes provisions for expansion and collaboration with other online performance simulation and diagnostic tools. This paper will be presented at the ISABE 2017 Conference, 5-8 September 2017, Manchester, UK

Percutaneous Coronary Intervention Complications: Where do we Stand?

Coronary angioplasty (or percutaneous coronary intervention, PCI) is a mature and widely diffused treatment technique for coronary artery disease. Over the last decades, great evolution has been realized concerning the related technology, the pharmacologic armamentarium and operators’ experience resulting in improved safety and success rates of PCI.  Despite the fact that associated risks have declined over time, since PCIs are invasive procedures, complication rates have always been and still are a vexing reality. They concern the cardiologist who sets the indication, the interventionalist who performs the procedure but most importantly the patient who should be well informed for the anticipated benefits and risks before giving his written informed consent. A concise update on recent data about the most important issues regarding PCI complications is attempted herein

Laparoscopic Cholecystectomy for Severe Acute Cholecystitis in a Patient with Situs Inversus Totalis and Posterior Cystic Artery

Situs inversus totalis is an inherited condition characterized by a mirror-image transposition of thoracic and abdominal organs. It often coexists with other anatomical variations. Transposition of the organs imposes special demands on the diagnostic and surgical skills of the surgeon. We report a case of a 34-year-old female patient presented with left upper quadrant pain, signs of acute abdomen, and unknown situs inversus totalis. Severe acute cholecystitis was diagnosed, and an uneventful laparoscopic cholecystectomy was performed. A posterior cystic artery was identified and ligated. Laparoscopic cholecystectomy is feasible in patients with severe acute calculus cholecystitis and situs inversus totalis; however, the surgeon should be alert of possible anatomic variations

Correction to: Two years later: Is the SARS-CoV-2 pandemic still having an impact on emergency surgery? An international cross-sectional survey among WSES members

Background: The SARS-CoV-2 pandemic is still ongoing and a major challenge for health care services worldwide. In the first WSES COVID-19 emergency surgery survey, a strong negative impact on emergency surgery (ES) had been described already early in the pandemic situation. However, the knowledge is limited about current effects of the pandemic on patient flow through emergency rooms, daily routine and decision making in ES as well as their changes over time during the last two pandemic years. This second WSES COVID-19 emergency surgery survey investigates the impact of the SARS-CoV-2 pandemic on ES during the course of the pandemic. Methods: A web survey had been distributed to medical specialists in ES during a four-week period from January 2022, investigating the impact of the pandemic on patients and septic diseases both requiring ES, structural problems due to the pandemic and time-to-intervention in ES routine. Results: 367 collaborators from 59 countries responded to the survey. The majority indicated that the pandemic still significantly impacts on treatment and outcome of surgical emergency patients (83.1% and 78.5%, respectively). As reasons, the collaborators reported decreased case load in ES (44.7%), but patients presenting with more prolonged and severe diseases, especially concerning perforated appendicitis (62.1%) and diverticulitis (57.5%). Otherwise, approximately 50% of the participants still observe a delay in time-to-intervention in ES compared with the situation before the pandemic. Relevant causes leading to enlarged time-to-intervention in ES during the pandemic are persistent problems with in-hospital logistics, lacks in medical staff as well as operating room and intensive care capacities during the pandemic. This leads not only to the need for triage or transferring of ES patients to other hospitals, reported by 64.0% and 48.8% of the collaborators, respectively, but also to paradigm shifts in treatment modalities to non-operative approaches reported by 67.3% of the participants, especially in uncomplicated appendicitis, cholecystitis and multiple-recurrent diverticulitis. Conclusions: The SARS-CoV-2 pandemic still significantly impacts on care and outcome of patients in ES. Well-known problems with in-hospital logistics are not sufficiently resolved by now; however, medical staff shortages and reduced capacities have been dramatically aggravated over last two pandemic years

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Corroded RC Beams at Service Load before and after Patch Repair and Strengthening with NSM CFRP Strips

This paper presents the experimental results of the structural behavior of four reinforced concrete beams with corroded steel reinforcement at service loads. One beam was non-corroded, one beam was corroded under an accelerated electrochemical technique to a small corrosion level (for one corrosion cycle), while two beams were corroded under the same conditions of an accelerated electrochemical technique and then subjected to vertical service loads that corresponded to 60% and 75% of the yield load of the non-corroded beam respectively for three corrosion cycles (with maximum mass loss around 25% for the first and 31% for the latter). Longitudinal cracks due to corrosion and flexural cracks due to loading were thoroughly recorded at the end of each cycle. The beam under the 75% service load had higher deflection increase for heavier corrosion. After the three successive serviceability load tests, the cracked concrete cover was removed and the steel rebars were treated. The cement-based repair mortar and two NSM FRP laminates were applied to both beams and were tested to failure. Despite the heavy corrosion, the patch repair and NSM strengthening enhanced the load-bearing capacity of the beams when compared with the non-corroded beam. All 10 tests are thoroughly discussed