Numerical Calculations and Cold Tests for Flow Fields of a 220t/h Retrofitted Oil-Boiler

In this paper, cold simulation experiments and numerical calculations are conducted to predict 3 D flow field aerodynamics for an oil furnace after being retrofitted due to its fuel variation. K ε model and SIMPLE program under body fit coordination (BFC) system, in which TTM non orthogonal method is used to control the irregular geometric boundary, are adopted to solve the control equations. Model tests are conducted to check the calculation results, showing that they are in agreement with each other. Three different alternatives with different side window locations are also calculated to optimize the designs. The field retrofitting results show that the combination of cold tests with numerical calculations has prosperous application in retrofitting or renewing medium and small boilers.

Design,fabrication,and cold test of an S-band high-gradient accelerating structure for compact proton therapy facility

An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator(linac)to accommodate the new development of compact,singleroom facilities and ultra-high dose rate(FLASH)radiotherapy.To optimize the design,an efficient optimization scheme is applied to improve the simulation efficiency.An S-band accelerating structure with 2856 MHz is designed with a low beta of 0.38,which is a difficult structure to achieve for a linac accelerating proton particles from 70 to 250 MeV,as a high gradient up to 50 MV/m is required.A special design involving a dual-feed coupler eliminates the dipole field effect.This paper presents all the details pertaining to the design,fabrication,and cold test results of the S-band high-gradient accelerating structure.

Design optimization and cold RF test of a 2.6-cell cryogenic RF gun

To further improve the performance of acceler-ators,the first cryogenic normal-conducting RF gun in China was designed and manufactured.As a new and attractive trend,this optimized cryogenic RF gun can generate a low-emittance beam with a short-driven laser pulse because of its promising high gradient on the cath-ode.In this paper,optimization of the RF design and beam dynamics,including suppression of the peak RF field and elimination of the multipole mode,is presented.In addi-tion,the emittance growth caused by the alignment devi-ation and RF jitter is discussed.After the gun was manufactured,a cold test was conducted at both room temperature and cryogenic conditions.At room tempera-ture,the field distribution was obtained by the bead pull method.Under cryogenic conditions,the RF properties,such as the coupling coefficient and quality factor,varied with temperature.The test results agreed with the design.In the cryogenic test,vibration measurements were performed.Without vibration isolation,a maximum vibration of 50 lm was observed.These cold test results are the basis of the following high-power test.

Model test study of frost heaving pressures in tunnels excavated in fractured rock mass in cold regions

Based on the similarity theory, taking the horseshoe, city-gate and round linings as examples, the value and distribution regularities of normal frost heaving pressures （hereinafter as frost heaving pressures） in tunnels excavated in fractured rock mass in cold regions under different constraints and freezing depths were studied by a test model. It was found that the larger the frozen depth, the larger the frost heaving pressure, and the stronger the top constraint, the larger the frost heaving pressure. For the horseshoe lining and city-gate lining, the top constraint has a greater effect on the frost heaving pressures on the arch and the inverted arch. For the round lining, the influences of the top constraint on the frost heaving pressure in all linings are almost the same. The frost heaving pressure is maximum on the city-gate lining and minimal on the round lining. The largest frost heaving pressure all occur near the foot of the inverted arch for the three kinds of lining. Thus, the test data basically coincide with the observed in situ data.

Metal and Composite Intermodal Containers in Comparative Cold Tests with Wood Chips

Intermodal containers have many advantages in the bulk supply chain, but idle times may cause freezing problems for containers in terminals and long-lasting deliveries, especially during the winter time in Nordic conditions. The aim of the cold tests was to study metal and composite containers’ ability to tolerate wood chips freezing into the inner surface of the container. Two of the containers were normal metal containers and one was a composite container. The loaded containers were put inside the laboratory hall, the temperature of which was -30°C, and kept there for variable times: less than 24 hours. The inner surface of one of metal containers was treated with a special coolant, EC1. After the test, the chips were unloaded, and the container walls were checked to determine whether there was any material left on them. The test results indicated the advantages of composite containers having a thermally insulated structure without freezing problems. At the same time, chips were freezing badly onto the floor of both metal containers. A frozen chip layer with a thickness of approximately 50 cm - 60 cm was stuck to the floors. As such, EC1 did not seem to prevent the freezing of the chips onto the inner surfaces. The results proved that intermodal logistics of truck and train transportation would be more suitable for composite containers than for metal containers in the winter time in Nordic conditions.

Resistance and Reactance of Monopole Fields Induced by a Test Charge Drifting Off-Axis in a Cold and Collisional Cylindrical Plasma

We study the interaction of a uniform, cold and collisional plasma with a test charged particle moving off-axis at a constant speed down a cylindrical tube with a resistive thick metallic wall. Upon matching the electromagnetic field components at all interfaces, the induced monopole electromagnetic fields in the plasma are obtained in the frequency domain. An expression for the plasma electric resistance and reactance is derived and analyzed numerically for some representative parameters. Near the plasma resonant frequency, the plasma resistance evolves with frequency like a parallel RLC resonator with peak resistance at the plasma frequency pe, while the plasma reactance can be capacitive or inductive in nature depending on the frequency under consideration.

Relationship between autonomic nervous system function and acute mountain sickness

Objective: To elucidate the role of the autonomic nervous system (ANS) in acute mountain sickness (AMS) during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level residents rapidly ascended to Tibet plateau (3 675 m altitude) by airplane from Chengdu plain (560 m altitude). ANS function was tested in plain and day 2–4 in Tibet by heart rate variability (HRV), cold pressor test (CPT). AMS was evaluated by clinic symptomatic scores. All subjects were divided into non-AMS group (57, scores≤4) and AMS group (42, scores>4). Results: Compared with non-AMS group, AMS group had higher standard deviation of normal to normal intervals (SDNN), root mean square of delta RR (rMSSD), low-frequency (LF) power, and normalized low-frequency (LFnu) power in plain (P<0.05). After arrival at 3 675 m altitude, AMS group had greater reduction in percentage of delta RR>50 ms(PNN50), rMSSD (P<0.01) and SDNN, LF, total power (TP) (P<0.05). Although no significant differences in the increase of SP and DP during CPT were found between 2 groups in plain, the SP increase during CPT of AMS group was less than non-AMS group (P<0.05) at 3 675 m altitude. AMS symptomatic scores was not only positively correlated with SDNN, rMSSD, LF/HF in plain (P<0.05), but also negatively correlated with HFnu in plain (P<0.05). Conclusion: During the initial high altitude exposure, ANS modulation is generally blunted, but the relatively predominant sympathetic control is enhanced, and this characteristic change of ANS function is positively correlated with the development of AMS.

Dispersion characteristics of a slow wave structure with a modified photonic band gap

This paper studies the dispersion characteristics of a modified photonic band-gap slow-wave structure with an open boundary by simulation and experiment. A mode launcher with a wheel radiator and a coupling probe is presented to excite a pure TM01-like mode. The cold test and simulation results show that the TM01-like mode is effectively excited and no parasitic modes appear. The dispersion characteristics obtained from the cold test are in good agreement with the calculated results.

Changes of autonomic nervous system function in healthy young men during initial phase at acute high-altitude exposure

Objective: To investigate the changes of autonomic nervous system (ANS) function during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level male residents were studied in Chengdu plain and then Tibet plateau. Heart rate variability (HRV), cold pressor test (CPT), resting heart rate (HR) and blood pressure (BP) were measured at baseline (560 m altitude) and in 2 to 4 d after arriving at Tibet plateau (3 675 m altitude) to assess the ANS function. Results: Compared with baseline, on day 2 in Tibet the standard deviation of normal to normal intervals (SDNN), high-frequency (HF) power, total power (TP), root mean square of delta RR (rMSSD), percentage of delta RR>50 ms (PNN50), normalized high-frequency (HFnu) and fractal dimension (FD) decreased significantly (SDNN, HF, TP P<0.01, rMSSD, PNN50, HFnu, FD P<0.05), while the normalized low-frequency (LFnu) and LF/HF increased significantly (P<0.01). During day 3–4 in Tibet, SDNN, rMSSD, HF, TP and HFnu tended to rebound while LFnu and LF/HF decreased towards baseline day by day. In addition, in Tibet the increase in systolic pressure (SP) and diastolic pressure (DP) during CPT decreased significantly (P<0.01, 0.05), but resting HR increased compared with baseline (P<0.01). Conclusion: ANS modulation is generally blunted, and the relatively predominant sympathetic control is enhanced originally, then it reverts to the sea level states gradually during the initial days of acute high-altitude exposure.

Detection of angiospastic disorders in the microcirculatory bed using laser diagnostics technologies

The evaluation of the microcirculatory bed functional state and the identification of angiospastic disorders with related complications,when the pathological changes are reversible,have an important role in medical practice.The aim of this study was to evaluate the possibility of using optical noninvasive methods and the cold pressor test to solve this problem.A total of 33 patients with rheumatological diseases and 32 healthy volunteers were included in the study.Laser Doppler flowmetry,tissue reflectance oximetry and pulse oximetry were used as optical noninvasive methods.The parameters were recorded before,immediately after and 20 min after the cold pressor test.Based on the measured parameters,the complex parameters of the microcirculatory bed were calculated.A detailed statistical analysis of the parameter changes for each individual in the two groups displayed diverse microcirculatory bed parameter responses upon cold exposure,with differing recovery of parameters after CPT.New diagnostic criteria were proposed for the identification of angiospastic disorders.According to the proposed criteria,27 people of the volunteers group were confirmed to not display any disorders.In the patient group,however,18 people were observed to have a relatively normal functional state of the microcirculatory bed,while 15 people were observed to have a possible tendency to angiospasm.To highlight the diferences between a relatively normal state and presence of angiospastic disorders,statistical analysis of experimental data was carried out,which revealed significant differences.Further analysis of data with angiospastic disorders identified a relationship between their diagnoses and the results of labo-ratory studies.Thus,the evaluation of combined noninvasive optical diagnostic method use,the cold pressor test and proposed diagnostic criteria showed a positive result.This approach can be used to detect the presence of possible angiospastic disorders and related complications,as well as mi-crocirculatory bed disorders against the background of other diseases.

Design and cold test of a rectangular cavity beam position monitor

The CBPM is a kind of monitor which is used for the measurement of beam transverse position. It is becoming increasingly popular due to its high potential in resolution performance. In theory, the resolution can reach about 1 nanometer. In this paper, a rectangular CBPM is designed for it has better X-Y isolation than a cylindrical one. It has been simulated and measured, and the results agree with each other very well. The procedures and results for the simulation and the cold test will be shown later and it will be proved that this is a reliable method for the CBPM design.

Design,fabrication,and cold-test results of C-band spherical RF pulse compressor prototype

Purpose Pulse compressor is a useful and common RF structure for Free Electron Laser and Linear Collider Facilities, whichcan improve the input power of accelerating structures significantly.Methods In this study, we designed, fabricated and tested a prototype of a compact C-band spherical pulse compressor.This pulse compressor utilizes one high Q0 spherical RF resonant cavity that works with two degenerated TE1,1,3modes anda dual-mode polarized coupler. The cavity and coupler were designed and machined separately and then brazed together.The prototype was tested carefully using vector network analyzer, and a cold-test system was set up to check the workingconditions of the spherical pulse compressor with inversed input powerResults Associated with the C-band high-gradient accelerating structures, the peak power gain and energy multiply factorcan be as high as 6.1 and 1.85, respectively, in theory. The average power gain is 3.8 in the first 0.372 μs after the phasereverse, which is the accelerator filling time. During the cold test, a peak power multiply factor of 6.04 and an energy multiplyfactor of 1.83 were achieved.Conclusions The test results agreed with the design well. The prototype was successfully made as a pre-research for thefuture energy multiplying scheme of SXFEL.

Experimental and numerical study on pressure oscillation in a combustor with rotary valve

A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine.This paper proposes a cold gas flow experimental system based on a rotary valve and a corresponding rotation model.A 3 D numerical model is proposed to obtain the transient flow inside the rotary valve,and the dynamic mesh technique and User-Defined Functions(UDFs)are adopted to implement a swing motion instead of a rotary motion.Several cold gas flow experiments are carried out at rotating speeds of 75225,and 375 rpm to verify the validity of the numerical model.The effects of rotating speed,stroke length ratio and radius of the RED(Rotor Exhaust Duct)on the pressure oscillations are studied using this numerical model.The results show that the maximum and peak-to-peak values of the pressure oscillations gradually decrease with increasing rotating speed.The ratio of the corresponding peak-to-peak value to the maximum pressure(pressure amplitude ratio)is reduced from 1.81 to 0.6%.The stroke length ratio affects the pressure waveform because it leads to a change in the time spent in the non-exhaust stage.When the stroke length ratio is 0,the waveform closely resembles a sine wave.With the increase in the stroke length ratio,the pressure waveform exhibits a more square or a triangular wave shape.Finally,a high-frequency and high-amplitude pressure oscillation can be obtained by appropriately increasing the radius of the RED.

Design and test of SX-FEL cavity BPM

This paper reports the design and cold test of the cavity beam position monitor （CBPM） for SX-FEL to fulfill tile requirement of beam position measurement resolution of less than 1 p_m, even 0.1 btm. The CBPM was optimized by using a coupling slot to damp the TM010 mode in the output signal. Tile isolation of TM01o mode is about 117 dB, and the shunt impedance is about 200 ~@4.65 GHz with the quality factor 80 from MAFIA simulation and test result. A special antenna was designed to load power for reducing excitation of other modes in the cavity. The resulting output power of TM110 mode was about 90 mV/mm when the source was 6 dBm, and the accomplishable minimum voltage was about 200 btV. The resolution of the CBPM was about 0.1 btm from the linear fitting result based on the cold test.

Development of a 325 MHz β=0.12 superconducting single spoke cavity for China-ADS

Twelve very low Beta superconducting single spoke cavities, whose Beta is only 0.12 （Spoke012） when operating at 325 IvIHz, are adopted in Injector I for China-ADS linac. This type of spoke cavity is believed to be one of tile key challenges for its very low geometric Beta. So far, in collaboration with Peking University and Harbin Institute of Technology, IHEP has successfully designed, fabricated, and tested the Spoke012 prototype cavity. This paper presents the details of the design, fabrication and test results for Spoke012 prototype cavity.

Simulation and analysis of O_(2)-CaO jet behavior with different shrouding fuel mediums in electric arc furnace steelmaking

The O_(2)-CaO jet with shrouding combustion flame demonstrates some advantages in quick melting and effective slag foaming by delivering lime powder deeply into the molten bath.Combining the discrete particle model and the eddy dissipation concept model with the detailed chemical kinetic mechanisms(GRI-Mech 3.0),computational fluid dynamics models of the O_(2)-CaO jet with different shrouding fuel mediums injection were developed.Firstly,the results of the numerical simulation were validated by the measured data of cold test for O_(2)-CaO injection.Then,the interaction between the particles and the gas jet of the O_(2)-CaO jet and the effect of shrouding fuel medium species on the fluid flow characteristics of the O_(2)-CaO jet were analyzed.Results show that the CaO particles can be effectively heated by the shrouding high-temperature combustion flame and compared with the O_(2)-CaO jet without shrouding gas,the potential core length was increased about 2.5,3.3 and 4.3 times by the shrouding flame generated from CO,CH_(4) and C_(3)H_(8).And with shrouding CH_(4) and C_(3)H_(8) injection,the CaO particles can be clustered together in a long distance,which would be helpful to improve the utilization efficiency of CaO particles.