Pressure recovery characteristics for a dilute gas-particle suspension flowing vertically downward in a pipe with a sudden expansion: A two-fluid modeling approach

This work applies the Eulerian-Eulerian model in conjunction with the kinetic theory of granular flow and inter-particle collisions to study the characteristics of pressure recovery for a dilute gas-particle suspension flowing through a pipe with a sudden expansion at a relatively higher solid loading.To do so,the numerical procedure was validated against experimental results for relatively small dilute phase flows in a pipe with a sudden expansion;a satisfactory agreement was obtained.Initially,the effect of the two significant numerical parameters namely,the speculairty coefficient and the coefficient of restitution for particle-particle collisions were investigated and then,for fixed combinations of these parameters the effect of particle-phase volume fraction,particle density,particle size,and inlet slip ratio were studied.It was concluded that pressure recovery diminishes as the speculairty coefficient increases and the particle-particle coefficient of restitution decreases.Pressure recovery was found to increase with increasing solid volume fraction for coarse particles whereas,for fine particles,a critical volume fraction is obtained above which pressure recovery reduces.An increase in slip ratio is found to diminish pressure recovery.Similarly,at relatively higher solid volume fractions,a critical diameter was found,above and below which pressure recovery decreases.

带内部支撑结构的低压排汽缸气动性能分析

The static pressure recovery of low-pressure exhaust hood is important for the overall effectiveness of steam turbines.The tubular and plate stiffeners inside the exhaust contribute to the structural safety of exhaust,which affect the aerodynamic performance.Given the complicated exhaust model coupled with the last stage of turbine,this paper intends to investigate the aerodynamic performance of exhaust hood with individual stiffeners using highfidelity numerical simulations in order to figure out the corresponding effects.The results show that(1)the types of stiffeners have different effects on the aerodynamic performance;and(2)different installation positions and types of plate stiffeners have different effects on aerodynamic performance.The above investigations highlight the future demand regarding reasonable layout and quantity of stiffeners to improve the aerodynamic performance of exhaust as well as maintaining the structural safety.

CHARACTERISTICS OF FLOW IN A PARTIALLY DYNAMIC HELICOPTER INLET

An experimental study of the flow in a helicopter inlet with front output shaft and partial flow dynamic head is conducted in low speed wind tunnel. The flow characters of the inlet in the range of the yaw angle from 0~135°are presented in this paper. The static pressure distributions along the duct, distortions of the flow field at the outlet section and total pressure recovery coefficients are measured and analyzed. The results show that this type of inlet has high total pressure recovery coefficients at a wide range of yaw angle. The regions of local flow separation and distortion are closely related to the yaw angle. It′s also found that the outlet section has the best characteristics at sideslip, and sharply deteriorated characteristics at the yawed flight with a yaw angle of more than 90°

Numerical Study on Aerodynamic Performance of CK Drone Aircraft Air Inlet in Maneuvering Flight

In view of the engineering background that CK drone aircraft needs modification and upgrading to improve its maneuvering performance,numerical research and analysis of air inlet aerodynamic performance are carried out.Firstly,based on the introduction of the theoretical knowledge involved in aircraft maneuvering flight,parameters such as aircraft attitude and engine mass flow etc.required for the aerodynamic performance calculation of CK drone aircraft air inlet are determined.By analyzing the test data of WP6 engine inlet distortion simulation board,the typical indexes are extracted as the basis for evaluating the air inlet performance of CK drone aircraft.Then,the aerodynamic characteristics of the inlet of CK drone aircraft under different maneuvering conditions are numerically studied,and the total pressure recovery coefficient and pressure distortion index of the outlet section are obtained.Several conclusions and suggestions are formed after the study.When CK drone aircraft flies at positive angle of attack,the inlet has good aerodynamic characteristics,which can meet the requirements of engine intake during high maneuverable flight.In the flight of negative angle of attack,the total pressure loss and pressure distortion at the outlet section of air inlet increase sharply,which cannot guarantee the stable working of the engine.On the premise that the aircraft attitude is satisfied,CK drone aircraft can use three engine thrust states of"Rated","Modified rated"and"Maximum"for high maneuverable flight.

SAIL—striding towards the future with the touch of green

Steel plays a vital role in every facet of our life.Like DNA in our body,steel plays a crucial role in the development of any society.From infrastructure,defence,transportation,research & development and even in day to day life,everywhere steel is used.Per capita consumption of steel is treated as an important index for the socioeconomic development of any country.The rapid and continuing growth of steel industry during last few decades bears testimony to the indispensability of steel as a vital resource for economic development.Though steel as a product is eco friendly,the process of making steel is associated with lot of energy and environmental ramifications.According to International Energy Outlook 2009,iron and steel industry account for about 20%of the total industrial energy consumption.Hence this industrial sector can play a pivotal role to influence the energy and environmental scenario of any country. As a responsible corporate citizen,Steel Authority of India Limited,the largest steel producer in India,has taken various initiatives over the years towards the protection of environment and reduction in energy consumption.This has resulted in the reduction of energy consumption by almost 15.45%over a period of last 10 years.The initiative is also evident in the company's growth plan which aims at almost doubling the production capacity in the near future from the existing level of 13.5 Mt/a.Implementation of tate of it lean echnologies like CDQ,TRT,and waste heat recovery from sinter plants,maximizing CDI & CTI in blast furnaces,augmentation of pollution control devices with more efficient equipment are on the anvil.These reaffirm our commitments for clean and sustainable environment. This paper gives an overview of the efforts taken by SAIL over the years for energy conservation and environmental protection with special emphasis on a few projects like by product fuel for power generation,use of energy efficient burners,maximizing the use of thyristors in place of motor generators,coke dry quenching facility, etc.

Design method for hypersonic bump inlet based on transverse pressure gradient

Transverse pressure gradient(TPG)is one of the key factors influencing the boundary layer airflow diversion in a bump inlet.This paper proposes a novel TPG-based hypersonic bump inlet design method.This method consists of two steps.First,a parametric optimization approach is employed to design a series of 2D inlets with various compression efficiencies.Then,according to the prescribed TPG,the optimized inlets are placed in different osculating planes to generate a 3D bump inlet.This method provides a means to directly control the aerodynamic parameters of the bump rather than the geometric parameters.By performing this method to a hypersonic chin inlet,a long and wide bump surface is formed in the compression wall,which leads to good integration of the bump/inlet.Results show that a part of the near-wall boundary layer flow is diverted by the bump,resulting in a slight decrease in the mass flow but a significant improvement in the total pressure recovery.In addition,the starting ability is significantly improved by adding the bump surface.Analysis reveals that the bump has a 3D rebuilding effect on the large-scale separation bubble of the unstarted inlet.Finally,a mass flow correction is performed on the designed bump inlet to increase the mass flow to full airflow capture.The results show that the mass flow rate of the corrected bump inlet reaches up to 0.9993,demonstrating that the correction method is effective.

Influence of various volute designs on volute overall performance

This paper discusses the influence of various volute designs on volute overall performance for a certain centrifu- gal compressor with both vaned and vaneless diffuser. Firstly, based on a free vortex flow pattern and the assumption of a circumferentially uniform flow at the design condition, a corrected method for volute design is adopted. By means of this method, corresponding to five geometric parameters affecting the volute overall performance, ten volute cases are designed. Secondly, the numerical simulation is employed and the detailed flow field and losses in different volutes with different geometric parameters are analyzed. The numerical investigation reveals that in all of the five geometric parameters, the radial location of the cross-section has the strongest influence on the performance of the volute. The non-uniform volute inlet formed by the upward vaned diffuser outlet flow is another important factor. Finally a relatively better value of D1/D2 is concluded.

Microjet flow control in an ultra-compact serpentine inlet

Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interthce plane （AIP） face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control （MFC） effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the monlcntunl coefficient affects the control effectiveness in a dual stepping manner.

Effect of the second-throat on the performance of supersonic-supersonic ejectors

The pressure matching and recovery performances of the second-throat supersonic-supersonic ejector have been performed experimentally and numerically in the current study.Schlieren pictures of flow structure in former part of the mixing chamber with varied stagnation pressure ratio of the primary and secondary flows have been taken,and the maximum compression ratios have been obtained.Additionally,the relevant numerical simulations have been performed.The obtained results show that the pressure matching performance of the second-throat supersonic-supersonic ejector is weaker than that of the constant area one,and the pressure recovery performance of the former is better than that of the latter.For the ejectors tested in this paper,the stagnation pressure ratios of the second-throat supersonic-supersonic ejector at the limiting condition are approximately 10% lower than those of the constant area one when the contraction angle of the mixing chamber is 4°,and the maximum compression ratio is 12%-30% higher.When the contraction angle of the mixing chamber is 6°,the pressure matching performance of the second-throat supersonic-supersonic ejector declines sharply,and the pressure recovery performance remains almost the same.When the contraction angle of the mixing chamber is 8°,the supersonic-supersonic ejection phenomenon does not take place any longer.

Interaction between Struts and Swirl Flow in Gas Turbine Exhaust Diffusers

The increasing use of gas turbines in combined cycle power plants together with the high amount of kinetic energy in modem gas turbine exhaust flows focuses attention on the design of gas turbine diffusers as the connecting part between the Brayton/Joule and the Rankine parts of the combined cycle. A scale model of a typical gas turbine exhaust diffuser is investigated experimentally. The test rig consists of a radial type, variable swirl generator which provides the exhaust flow corresponding to different gas turbine operating conditions. Static pressure measurements are carried out along the outer diffuser walls and along the hub of the annular part and along the centerline of the conical diffuser. Velocity distributions at several axial positions in the annular and conical diffuser have been measured using a Laser Doppler Velocimeter （LDV）. Pressure recovery coefficients and velocity profiles are depicted as a function of diffuser length for several combinations of swirl strength, tip flow and strut geometries. The diffuser without struts achieved a higher pressure recovery than the diffuser with struts at all swirl angle settings. The diffuser with cylindrical struts achieved a higher pressure recovery than the diffuser with profiled struts at all swirl angle seO.ings. Inlet flows with swirl angles over 18° affected the pressure recovery negatively for all strut configurations.

Gas-solid flow in a diffuser:Effect of inter-particle and particle-wall collisions

This article investigates the role of the specularity coefficient(φ,the extent of the energy dissipation due to particle-wall collisions),inter-particle restitution coefficient(e_(pp),the extent of the energy dissipation due to inter-particle collisions),and four combinations of these variables on the hydrodynamics,and the pressure recovery of the dilute gas-solid suspension in a diffuser.The investigation applies the two-fluid modeling approach along with the kinetic theory of the granular flow.The present investigation’s findings indicate that an increase inφor a reduction in e_(pp) reduces the pressure recovery by weakening the reverse momentum transfer phenomenon,which is recognized as the primary means for the pressure recovery.Besides,in a gas-solid flow system,a higherφor smaller e_(pp) enhances the particles’trapping in the recirculation zone.The recirculation zone’s strength and size increase asφincreases or e_(pp) reduces.Moreover,an increase in the wall-particle and inter-particle interactions strengthens the sidewise displacement of the particles.The effect of the wall-particle and inter-particle interactions are insignificant for extremely small solid loading.