韩雪教授运用桂枝加厚朴杏子汤治疗儿科疾病经验

韩雪教授从事中医儿科临床多年,通过辨证施治运用桂枝加厚朴杏子汤治疗小儿急性上呼吸道感染、急性扁桃体炎、慢性咳嗽、支气管哮喘、儿童抽动障碍等疾病取得良好疗效。韩雪教授认为,桂枝加厚朴杏子汤可有效调节患儿机体阴阳平衡,营卫气血流通,三焦气机升降,对于外感营卫不和、气机升降失调、脾胃虚弱导致的疾病有较好效果,且该方药味少,口感好,小儿容易接受,值得临床借鉴。

Design Optimization of Non-Axisymmetric Vane for an Axial Compressor under Inlet Distortion

The flow field at the inlet of compressors is generally encountered combined total pressure and swirl distortion for either aircraft engine with S-duct or gas turbine with lateral air intake.This inevitably deteriorates compressor aerodynamic performance,including not only the efficiency or pressure ratio but also the operation stability.In order to conquer this issue,appropriate measures such as integrating flow control techniques and modifying inlet or compressor design are of benefits.Due to this motivation,this article develops a full-annular two-dimensional(2D)and a partial-annular three-dimension(3D)optimization strategy for non-axisymmetric vane design.Firstly,two numerical simulation methods for evaluating performance of full-annular 2D vane and compressor with partial-annular 3D vane are developed.The swirl patterns at the inlet of a 1.5-stage axial compressor are analyzed and parametrized,and the parameterization is transferred to characterize the circumferential distribution of geometrical parameters of the vane profile.These approaches dramatically reduce computational simulation costs without violating the non-axisymmetric flow distortion patterns.Then various full-annular 2D sections at different radial locations are constructed as design space.The designed vane is reconstructed and 3D numerical simulations are performed to examine performance of the non-axisymmetric vane and the compressor with it.Also,partial annular 3D optimization is conducted for balancing compressor efficiency and stall margin.Results indicate that the designed non-axisymmetric vane based on full-annular optimization approach can decrease the vane total pressure loss under the considered inlet flow distortion,while those using partial-annular optimization achieve positive effects on compressor stall margin.

A Review on Theoretical and Numerical Research of Axial Compressor Surge

Surge is an unstable operating condition of the aero-engine that can move the engine into a destabilized state and cause devastating damage.One of the most popular topics in the academic and industrial communities is to figure out the mechanism of the surge and withdraw from the surge safely.Based on rig test results and practical data from engine operation,various theories of surge mechanisms have been proposed by researchers,and some classical analytical models have been developed for modelling and prediction.In recent years,with the rapid development of numerical simulation and the improvement of computational capability,computational fluid dynamics(CFD)has been widely applied to the investigation of axial compressor surge events.In this review,the principles and general characteristics of the surge phenomenon are first introduced.Subsequently,the main theoretical models and CFD simulations are presented,and their advantages and disadvantages are discussed.In conclusion,we have proposed potential improvements and future technical routes for the surge phenomenon.The purpose of this paper is to provide a valuable reference for surge studies on axial compressors.

Hybrid Slot-Groove Casing Treatment for Stall Margin Improvement on an Axial Flow Compressor with Circumferential Total Pressure Distortion

The hybrid slot-groove(S-G)casing treatment(CT),which combines the advantages of slot and groove in consideration of stall margin enhancing and efficiency penalty,was experimentally investigated under circumferential distorted inflows.Previous experiments showed that the hybrid S-G CT can extend the stability by 19.79%with uniform inflow condition.To further estimate its stability enhancement ability with distorted inflow,three types of circumferential total pressure distortion inflow that the distorted intensities(DC(60))are equal to 0.90%,4.12%,and 24.75%,are selected to conduct a serial of experiments.Results demonstrated that the stability of the compressor were deteriorated by 7.87%,9.19%and 39.08%respectively under three distorted inflows.It was founded that,under the above-mentioned distorted inflows,the hybrid S-G CT was able to extend the stability by 18.48%,17.81%,and 13.80%,respectively,which proved the strong anti-distortion ability of the hybrid S-G CT.By using the dynamic pressure sensors fixed on the casing wall,the unsteady measurements demonstrated that the stall precursor with uniform and circumferential distorted inflows are always spiky-wave;thus the hybrid S-G CT can play an excellent stability enhancement capability.The analytical results with power spectral density proved that,when at the same flow point,the perturbation,with frequency being around the rotating stall frequency band,was distinctly suppressed by hybrid S-G CT,thus delaying the rotating stall.The stall precursor detected in the casing wall depicted that unlike the short length-scale of stall precursor(5–6 blade passage)under smooth casing;the hybrid S-G CT can create a stall precursor with long length-scale.Under the distortion intensities from 0 to 4.12%,the length scale of the stall precursors occupies approximately 10–12 blade passages.As the distortion intensity further increases to 24.75%,the length scale of stall precursor increases to occupy 16–17 blade passages.This phenomenon can guide the stall warning studies with compressors using CT in the future.

Investigation of dielectric barrier discharge plasma flow control

Effects of plasma flow control are researched on the basis of plasma exciting flow experiments and numerical simulations. Turbulent model is more effective than laminar model in plasma numerical simulation as results showed. Both plasma exciting effects of acceleration and flow separation suppression are investigated through experiments carried on the flat plate and the compressor cascades. The results demonstrate that boundary layer characteristic is modified by plasma exciting. Distributions of total pressure and velocity in the wake are improved notably for 20 m/s coming velocity and the effect of plasma can still be observed while velocity is increased to 50 m/s. For low velocity flow, plasma exciting is effective in flow separation suppression.

Model study of relationship between local temperature and artificial heat release

In recent decades,it presents a more obvious temperature rise in urban area along with the global warming.City is generally the center of human society,so the study on urban temperature variation will be helpful to our city development planning that is to reduce urban warming.The study is also helpful to a more comprehensive understanding of the causes of climate warming,which could provide a theoretical support to the government to make more reasonable international energy policies.Local temperature rise has different mechanisms with the global warming:large quantities of artificial heat release from the energy consumption will stay in urban areas for a period of time,which will inevitably influence the short-term trend of the local temperature change.Based on that view,a structural thermodynamic model was established in this paper to investigate the effect of the artificial heat release on the urban local temperatures.In the model,the city environment was divided into Human,Local,Outer three blocks,and then the heat and temperatures of the blocks were analyzed based on the laws of thermodynamics.After that,the effect of artificial heat release in Human block on the local temperatures was clarified.The model shows that the artificial heat release has an approximately linearly promoting effect on the local temperature rise,and the more the heat release is,the stronger the effect is.In addition,a validation of that model was carried out based on some national statistical data.The data of temperatures and artificial heat release of some provincial capitals of China were analyzed with linear regression extrapolation method and Pearson correlation statistical method.The results show that in most capital cities,the temperature variations basically depend on the artificial heat release in a linear relationship,which usually becomes more apparent with the increase of the artificial heat release in both spatial and temporal dimensions.The conclusions of the statistics have good conformity with the model and the rationality of the model is verified.

Control of endwall secondary flow in a compressor cascade with dielectric barrier discharge plasma actuation

Three dielectric barrier discharge plasma actuators were mounted at the positions of 20%,40%and 60%of chord length on the endwall in a compressor cascade.The downstream flow field of the cascade has been measured with a mini five-hole pressure probe with and without the plasma actuation.The measured results show that the plasma actuation most effectively reduces total pressure loss and flow blockage when the actuators are operated simultaneously.As each of the actuators is operated independently,the actuator at the position of 20%of chord length most effectively reduces flow blockage, and the actuator at the position of 60%of chord length fairly reduces total pressure loss.However, negative pressure loss reduction occurs with the plasma actuator at the position of 40%of chord length.In brief,the plasma actuation placed on the endwall in the cascade apparently influences the endwall secondary flow,and the optimal locations and strength of actuation are critical for the control of endwall secondary flow in a compressor cascade with the plasma actuators.

Dynamic analysis of a flameless combustion model combustor

Flameless combustion is a new technology with the following advantages:1)Ultra-low emissions of both NOX and CO;2)fuel flexibility,from liquid fuels,natural gas to hydrogen-rich syngas;3)lower possibility of flashback and thermoacoustic oscillations.In this paper,we focus on the dynamic characteristics of a flameless model combustor.Experimental results show that flameless combustion can lower emissions while maintaining combustion stability.However,combining a pilot flame with flameless combustion may excite thermoacoustic instability.

Performance analysis and improvement of a high flow coefficient centrifugal compressor

Very high flow coefficient centrifugal compressor stages are mostly applied as the first stages of multistage compressors.The performance of this type of stages is critical to the entire centrifugal compressors,but surprisingly little related information is available in the open literature.A centrifugal compressor with high inlet flow coefficient of 0.2,presenting a narrow operating range and unstable running situation even at design speed during the test,is investigated here.To reveal flow details in this centrifugal compressor,numerical simulations have been carried out and indicate that excessive impeller flow diffusion results in the poor performance of this centrifugal compressor.With the same inlet flow coefficient,six redesign cases coming from an in-house one-dimensional analysis program are proposed together with impeller trimming and equal flow area design method for corresponding vaneless diffuser.Performance comparison among these redesign centrifugal compressors is presented and the most suitable one is recommended for test in the future.In addition,three redesign cases with lower inlet flow coefficient developed by means of flow trimming are shown in the end to satisfy potential application areas.Finally,the results in this study can provide valuable reference information for multistage centrifugal compressor design.

Low Speed Axial Compressor Stall Margin Improvement by Unsteady Plasma Actuation

This research investigates the use of single dielectric barrier discharge(SDBD) actuators for energizing the tip leakage flow to suppress rotating stall inception and extend the stable operating range of a low speed axial compressor with a single rotor.The jet induced by the plasma actuator adds momentum to the flow in the tip region and has a significant impact on the tip-gap flow.Experiments are carried out on a low speed axial compressor with a single rotor.The static pressure is measured at both the rotor inlet and outlet.The flow coefficient and pressure rise coefficient are calculated.Then the characteristic line is acquired to show the overall performance of the compressor.With unsteady plasma actuation of 18kV and 60W the compressor stability range improvement is realized at rotor speed of 1500 r/min – 2400 r/min.

The Self-induced Unsteadiness of Tip Leakage Flow in an Axial Low-Speed Compressor with Single Circumferential Casing Groove

Numerical investigation on the self-induced unsteadiness of tip leakage flow(TLF) for an axial low-speed compressor with smooth wall and six single grooved casings are presented. A ten-passage numerical scheme is used to solve the unsteady Reynolds averaged Navier-Stokes(URANS) equations. It is found that the single grooves at various axial locations could have a large impact on the self-induced unsteadiness and the stall margin improvement(SMI) of compressor. The trend of SMI with groove center location demonstrates that the groove located near the mid of blade tip chord generates the best SMI. The worst groove is located about 20% Cax after the blade leading edge. The root-mean-squre of static pressure(RMSP) contours at 99.5% span and fast Fourier transform for the static pressure traces recorded in the tip clearance region for each casing are analyzed. The results demonstrate that the single groove location not only affects the oscillating strength but also the frequency of the unsteady tip leakage flow. At the near-stall point of smooth casing, the self-induced unsteadiness of TLF is enhanced most by the best grooved casing for SMI. While, the self-induced unsteadiness disappears when the worst groove for SMI is added. The characteristic frequency of TLF is about 0.55 blade passing frequency(BPF) with smooth casing. The frequency components become complicated as the single groove moves from the leading edge to the trailing edge of the blade.

Aerodynamic Performance Improvement of a Highly Loaded Compressor Airfoil with Coanda Jet Flap

Coanda jet flap is an effective flow control technique,which offers pressurized high streamwise velocity to eliminate the boundary layer flow separation and increase the aerodynamic loading of compressor blades.Traditionally,there is only single-jet flap on the blade suction side.A novel Coanda double-jet flap configuration combining the front-jet slot near the blade leading edge and the rear-jet slot near the blade trailing edge is proposed and investigated in this paper.The reference highly loaded compressor profile is the Zierke&Deutsch double-circular-arc airfoil with the diffusion factor of 0.66.Firstly,three types of Coanda jet flap configurations including front-jet,rear-jet and the novel double-jet flaps are designed based on the 2D flow fields in the highly loaded compressor blade passage.The Back Propagation Neural Network(BPNN)combined with the genetic algorithm(GA)is adopted to obtain the optimal geometry for each type of Coanda jet flap configuration.Numerical simulations are then performed to understand the effects of the three optimal Coanda jet flaps on the compressor airfoil performance.Results indicate all the three types of Coanda jet flaps effectively improve the aerodynamic performance of the highly loaded airfoil,and the Coanda double-jet flap behaves best in controlling the boundary layer flow separation.At the inlet flow condition with incidence angle of 5°,the total pressure loss coefficient is reduced by 52.5%and the static pressure rise coefficient is increased by 25.7%with Coanda double-jet flap when the normalized jet mass flow ratio of the front jet and the rear jet is equal to 1.5%and 0.5%,respectively.The impacts of geometric parameters and jet mass flow ratios on the airfoil aerodynamic performance are further analyzed.It is observed that the geometric design parameters of Coanda double-jet flap determine airfoil thickness and jet slot position,which plays the key role in supressing flow separation on the airfoil suction side.Furthermore,there exists an optimal combination of front-jet and rear-jet mass flow ratios to achieve the minimum flow loss at each incidence angle of incoming flow.These results indicate that Coanda double-jet flap combining the adjust of jet mass flow rate varying with the incidence angle of incoming flow would be a promising adaptive flow control technique.

Special column for the memory of Professor CHEN Naixing

The special column of Journal of Thermal Science (JTS) is dedicated to the late Professor CHEN Naixing, who passed away on the 6th of August of 2018 when he was turning 85 years old. Professor Chen received his postgraduate degree from Bauman State Technical University in Moscow in 1958. Before he joined the Institute of Engineering Thermophysics of Chinese Academy of Sciences in 1980, he also worked for Harbin Turbine Factory, the Naval Research Center, and the Institute of Mechanics of Chinese Academy of Sciences.