Effect of ratio of wall boundary layer thickness to jet diameter on mixing of a normal hydrogen jet in a supersonic stream

A preliminary experimental program was conducted to determine the effect of the ratio of the free-stream boundary-layer thickness to jet diameter on the secondary jet penetration and mixing rate. Tests were conducted on a flat plate in a Mach number 4.05 airflow with sonic injection of hydrogen normal to the free-stream direction from circular underexpanded injectors. The ratio of boundary-layer thickness to jet diameter ranged from 1.25 to 6.5. Previous correlations of mixing performance were modified to account for the effect of the ratio of boundary-layer thickness to jet diameter

Normal injection of helium from swept struts into ducted supersonic flow

Recent design studies have shown that airframe-integrated scramjets should include instream mounted, swept-back strut fuel injectors to obtain short combustors. Because there was no data in the literature on mixing characteristics of swept strut fuel injectors, the present investigation was undertaken to provide such data. This investigation was made with two swept struts in a closed duct at Mach number of 4.4 and nominal jet-to-air mass flow ratio of 0.029 with helium used to simulate hydrogen fuel. The data is compared with flat plate mounted normal injector data to obtain the effect of swept struts on mixing. Three injector patterns were evaluated representing the range of hole spacing and jet-to-freestream dynamic pressure ratio of interest. Measured helium concentration, pitot pressure, and static pressure in the downstream mixing region are used to generate contour plots necessary to define the mixing region flow field and the mixing parameters

Evaluation of a bulk calorimeter and heat balance for determination of supersonic combustor efficiency

Results are presented from the shakedown and evaluation test of a bulk calorimeter. The calorimeter is designed to quench the combustion at the exit of a direct-connect, hydrogen fueled, scramjet combustor model, and to provide the measurements necessary to perform an analysis of combustion efficiency. Results indicate that the calorimeter quenches reaction, that reasonable response times are obtained, and that the calculated combustion efficiency is repeatable within + or -3 percent and varies in a regular way with combustor model parameters such as injected fuel equivalence ratio

Interaction between step fuel injectors on opposite walls in a supersonic combustor model

Results are presented from an experimental investigation of perpendicular, hydrogen fuel injection and combustion from opposing walls in a scramjet combustor model using a longitudinally staged laterally inline step-injection configuration. The model represents a portion of the flow in the Langley integrated modular scramjet engine combustor operating at a flight Mach number of 7. When operating at a ratio of jet pressure to free-stream dynamic pressure of 3, the injectors produce a bulk equivalence ratio of unity. This investigation represents part of a continuing study of the modular engine fuel injectors and is specifically designed to eliminate the adverse lateral pressure gradient observed at the injector location in a previous test. Flow survey contours at three axial locations, ranging from one-third of the engine combustor length to the total engine combustor length, are used to determine mixing efficiency and fuel distribution. Wall static pressures are analyzed by using one-dimensional theory to determine the combustion efficiency. Results show a significant improvement over previous injector designs tested in this duct geometry

Criteria for self-ignition of supersonic hydrogen-air mixtures

A correlation of available self ignition data for supersonic hydrogen-air mixtures in configurations representative of scramjet combustors was made. The correlation was examined in light of simplified ignition-limit models. The data and model included cases of injection from transverse fuel jets on walls, transverse jets behind swept and unswept steps, and transverse injection ahead of swept and unswept steps and strut bases. The results provide useful guidance for predicting self ignition in a variety of applications. The likely regions for self ignition in a combustor are given in order of merit

Nonreactive mixing study of a scramjet swept-strut fuel injector

The results are presented of a cold-mixing investigation performed to supply combustor design information and to determine optimum normal fuel-injector configurations for a general scramjet swept-strut fuel injector. The experimental investigation was made with two swept struts in a closed duct at a Mach number of 4.4 and a nominal ratio of jet mass flow to air mass flow of 0.0295, with helium used to simulate hydrogen fuel. Four injector patterns were evaluated; they represented the range of hole spacing and the ratio of jet dynamic pressure to free-stream dynamic pressure. Helium concentration, pitot pressure, and static pressure in the downstream mixing region were measured to generate the contour plots needed to define the mixing-region flow field and the mixing parameters. Experimental results show that the fuel penetration from the struts was less than the predicted values based on flat-plate data; but the mixing rate was faster and produced a mixing length less than one-half that predicted

The NASA Hyper-X Program

This paper provides an overview of NASA's Hyper-X Program; a focused hypersonic technology effort designed to move hypersonic, airbreathing vehicle technology from the laboratory environment to the flight environment. This paper presents an overview of the flight test program, research objectives, approach, schedule and status. Substantial experimental database and concept validation have been completed. The program is currently concentrating on the first, Mach 7, vehicle development, verification and validation in preparation for wind-tunnel testing in 1998 and flight testing in 1999. Parallel to this effort the Mach 5 and 10 vehicle designs are being finalized. Detailed analytical and experimental evaluation of the Mach 7 vehicle at the flight conditions is nearing completion, and will provide a database for validation of design methods once flight test data are available

The Effectiveness of a Ventilator Care Bundle Protocol in Decreasing Incidence of Ventilator-Acquired Pneumonia: A Scoping Review

Purpose/Background Ventilator-acquired pneumonia (VAP) is a preventable hospital-acquired infection with a high mortality rate. Ventilator care bundles (VCB) are implemented to decrease the risk of infection while patients are mechanically ventilated. The aim of this scoping review was to assess how adult patients in the intensive care unit (ICU) requiring mechanical ventilation and the incidence of VAP are affected by staff’s compliance to a VCB. Methods From August of 2022 to November 2022, literature research was done among databases such as PubMed, MEDLINE, and CINAHL. The systematic search in PubMed yielded 55 results with the headings of “(ventilator) AND (care bundle) AND (pneumonia)”. 43 articles were excluded due the inclusion of non-adult patients. From the 12 articles remaining, only 3 from PubMed were relevant. 7 articles from similar searches were also included. The final 10 articles went through rapid critical appraisal and the primary outcomes were synthesized in a data table. Results 2 systematic reviews, 1 controlled trial without randomization, 6 case-control studies, and 1 quality improvement project were included. Each article provided evidence supporting staff compliance with a VCB improved patient outcomes. These outcomes include decreased incidence of VAP, hospital and ICU length of stay, and patient mortality. Implications for Nursing Practice A VCB is a feasible protocol to improve patient outcomes. Prioritization of these interventions decreases incidence rates of VAP. All staff caring for ventilated patients should be educated on the success of VCBs to ensure appropriate compliance and improve patient outcomes

Esmolol Compared to Fentanyl for Hemodynamic Attenuation during Intubation: A Scoping Review

Purpose/Background Endotracheal intubation and laryngoscopy potentiate the cardiovascular response in the form of hypertension, tachycardia, and ventricular arrhythmias. Suppression of this adrenergic response is necessary to ensure patient safety. Currently, anesthesia providers employ many methods to attenuate the sympathetic response without established guidelines. As such, our project aimed to determine the effectiveness of fentanyl compared to esmolol in attenuating the hemodynamic response during laryngoscopy and endotracheal intubation within the first five minutes and throughout the intraoperative period. Methods A literature review was completed of ten critically appraised articles from the years 2011-2022. Articles in the review included randomized control studies, peer reviews, evidence-based practice, comparative studies, and meta-analyses. All articles included must have addressed fentanyl or esmolol groups associated with hemodynamics before and after intubation. A level of evidence outcomes table was composed to provide a synthesis of results from the ten chosen articles. Results Of the multiple articles reviewed, the majority concluded fentanyl was the better choice to administer before induction for attenuating hemodynamic responses to intubation. Many studies differ in the patient populations evaluated, but overall, fentanyl caused the least number of hypertensive episodes. Esmolol was typically more effective on the heart rate response, while the combination of the two medications was more effective on the arterial pressure. However, such combination resulted in significant post-intubation hypotension, requiring an immediate response. Implications for Nursing Practice Results provided in this scoping review afforded the authors a diverse level of evidence that using fentanyl or esmolol can attenuate hemodynamic responses to endotracheal intubation. The individual need of each patient is highly regarded as the decision-making aspect of each case, with fentanyl as the preferred agent for overall hemodynamic stability. These findings suggest further evaluations regarding patient individualization are needed when choosing the appropriate drug for attenuating the hemodynamic response to intubation

Systematic review of perioperative and quality-of-life outcomes following surgical management of localised renal cancer

UCAN Cancer Charity (www.ucanhelp.org.uk) and MacMillan Cancer Charity (www.macmillan.org.uk) helped design and conduct the study.Peer reviewedPostprin