Hot-jet simulation in cryogenic wind tunnels

In order to evaluate hot jet simulation capability in cryogenic wind tunnel testing, simple theoretical calculations were performed. The similarity parameters, isentropic flow properties, and normal shock relations were calculated for a variety of jet simulation techniques. The results were compared with those estimated for a full scale flight condition. It was shown that the cryogenic wind tunnel testing provides an opportunity for the most accurate hot jet simulation technique. By using a compressed nitrogen gas at ambient or moderately elevated temperatures as a jet gas, most all of the relevant similarity parameters including the jet temperature and velocity ratios and the Reynolds numbers, can be set to the full scale flight values. The only exception is the ratio of specific heats for jet flow. In an attempt to match the ratio of specific heats for the turbojet flow, gases other than pure nitrogen were considered. It was found that a nitrogen/methane mixture at moderately elevated temperature behaves like the real combustion gas. Using this mixture as a jet gas, complete simulation of the full scale turbojet exhaust becomes possible in cryogenic wind tunnels

反復的な督励が口頭指導下の心肺蘇生法に与える効果に関する無作為化シミュレーション研究

Background: Current guidelines emphasize the assistance of the emergency dispatcher in bystander cardiopulmonary resusitation (CPR). Its quality, however, has varied across cases. Objective: To determine the effect of repetitive coaching by dispatchers using verbal encouragement on the quality of lay-rescuer CPR. Methods: We conducted a dispatch-assisted CPR (DACPR) simulation study. Participants with no CPR training within the previous year were assigned randomly to 1 of 2 DACPR simulations. One was the No Coaching Group: callers were told to perform CPR and the dispatcher periodically confirmed that the caller was performing CPR. The second group was the Coaching Group: the dispatcher repetitively coached, encouraged, and counted aloud using a metronome. Participants performed CPR for 2 min under instruction from the study dispatcher. Parameters including chest compression depth, rate, and chest compression fraction were recorded by video camera and CPR manikin. Results: Forty-nine participants 20 to 50 years of age were recruited, and 48 completed the simulation (Coaching Group, n = 27; No Coaching Group, n = 21). The chest compression fraction was higher in the Coaching Group (99.4% vs. 93.0%, p = 0.005) and no participants interrupted chest compression more than 10 s in this group. When comparing the average depth of each 30-s period in each group, the depth increased over time in the Coaching Group (40.9 mm, 43.9 mm, 44.1 mm, and 42.8 mm), while it slightly decreased in the No Coaching Group (40.6 mm, 40.1 mm, 39.4 mm, and 39.8 mm). Conclusions: Repetitive verbal encouragements augmented chest compression depth with less-hands off time. Continuous coaching by dispatchers can optimize lay-rescuer CPR.博士（医学）・甲第852号・令和4年9月28日© 2022 Elsevier Inc.© 2022 The Author(s). Published by Elsevier Inc.This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Compressibility effects on Flat-Plates with Serrated Leading-Edges at a Low Reynolds Number

This study evaluates the influence of a serrated leading edge on flat-plate aerodynamics at low-Reynolds-number and subsonic high-Mach-number conditions. Forces are measured for a Mach number ranging from 0.2 to 0.64 at aReynolds number of (12,000 ± 1000). Pressure distributions are obtained under the same conditions using pressure sensitive paint (PSP) measurement. Three models are tested: a flat plate without serrations used as the baseline case and two flat plates with serrated leading edges of different wavelength-to-amplitude ratios. Results show that the aerodynamic performance of flat plates with serrations is slightly changed from the baseline case. The plate with short-wavelength serrations underperforms in terms of the lift-to-drag ratio under all the conditions compared to the baseline case while the plate with large-wavelength serrations slightly outperforms it at around the stall angle. The Mach number has little effect on the attached flow while the lift increases with the Mach number under deep stall conditions. Serrations maintain the lift even under high angle of attack conditions when Mach number varies. The twodimensional pressure distributions and the analyses of local chordwise pressure coefficient distributions at different spanwise locations and of periodicity of spanwise pressure coefficients allow categorisation of the complex flow structures into three types. These configurations feature different types of low pressure regions downstream of troughs. The periodicity of the pattern depends not only on the angle of attack but also on the Mach number

Development Of Fuel-Flexible Gas Turbine Combustor

LectureGrowing global energy demands are motivating the gas turbine industry to seek fuel-flexible gas turbines capable of burning a wide variety of fuels as a means of increasing energy supply stability and security. These fuel-flexible gas turbines require diluent-free (“dry”), low nitrogen oxide (NOx) and flashback-resistant combustors for various fuels in order to achieve low NOx emissions and high plant efficiency for low carbon dioxide (CO2) emissions. This paper describes the development of a state-of-the-art dry low-NOx and flashback-resistant combustor for fuel-flexible gas turbines. This advanced combustor consists of multiple fuel nozzles and multiple air holes. One fuel nozzle and one air hole are installed coaxially to give one key element, and a cluster of key elements constitutes one burner, which forms one flame. Multiple cluster burners constitute a can combustor, and several can combustors are installed on a gas turbine. In this paper, the burner is called a “cluster burner,” and the combustor is called a “multi-cluster combustor.” The essence of the burner concept is the integration of two key technologies: low-NOx combustion due to the enhancement of fuel-air mixing; and flashback-resistant combustion due to short premixing sections, air-stream-surrounded fuel jets and lifted flames. The development approach of the multi-cluster combustor consists of three steps: burner development; combustor development; and feasibility demonstration for practical plants. The first step optimizes burner configurations by fundamental research at atmospheric pressure. The second step optimizes combustor configurations by single-can combustor testing at medium to high pressures. The third step demonstrates the feasibility of the combustor by field testing with real gas turbines. This paper describes the development work in each step of the multi-cluster combustor developed particularly for hydrogen content syngas fuels in a coal-based integrated gasification combined cycle (IGCC), and the field test in an IGCC pilot plant demonstrates the feasibility of the combustor for practical plants. This paper also describes applications of this combustion technology to expand fuel flexibility

Wind Tunnel Testing on Start/Unstart Characteristics of Finite Supersonic Biplane Wing

This study describes the start/unstart characteristics of a finite and rectangular supersonic biplane wing. Two wing models were tested in wind tunnels with aspect ratios of 0.75 (model A) and 2.5 (model B). The models were composed of a Busemann biplane section. The tests were carried out using supersonic and transonic wind tunnels over a Mach number range of 0.3≤M∞≤2.3 with angles of attack of 0°, 2°, and 4°. The Schlieren system was used to observe the flow characteristics around the models. The experimental results showed that these models had start/unstart characteristics that differed from those of the Busemann biplane (two dimensional) owing to three-dimensional effects. Models A and B started at lower Mach numbers than the Busemann biplane. The characteristics also varied with aspect ratio: model A (1.3<M∞<1.5) started at a lower Mach number than model B (1.6<M∞<1.8) owing to the lower aspect ratio. Model B was located in the double solution domain for the start/unstart characteristics at M∞=1.7, and model B was in either the start or unstart state at M∞=1.7. Once the state was determined, either state was stable