Pressure Loss Ratio Research Articles

Side Gust Effects on the Performance of a Supersonic Inlet with Bleed

A computational investigation on the effects of side gust on the performance of a supersonic inlet with a bleed system at Mach 1.8 is reported. This is an extension to a recent study (Halwas, H. K., and Aggarwal, S. K., “Effect of Side Gust on the Performance of External Compression Supersonic Inlet,” Journal of Aircraft, Vol. 56, No. 2, March 2019, pp. 569–582) that analyzed a similar inlet without bleed. The supersonic section is designed using the Taylor–Maccoll method, and the rest of the inlet is designed using a methodology from the literature. The bleed is positioned at the throat inner wall, and its shape is a combination of a ram scoop and a flush slot. ICEM CFD software is used to generate a three-dimensional (3-D) structured mesh. ANSYS Fluent 18.2 code is used to perform 3-D simulations. Grid sensitivity tests are performed using local grid refinements and by varying the total grid points from 3 to 10 million. The effects of side gust on the shock system and flow are analyzed by examining the Mach number and pressure distributions. The inlet performance is characterized in terms of the total pressure loss, flow distortion, and mass flow ratio parameters for a gust speed of and angles of 0, 30, and 60 deg. The results indicate that the inlet performance is significantly affected by the side gust, although the bleed system mostly removes the low-momentum flow.

Numerical investigation of turbulent flow and heat transfer of nanofluid inside a wavy microchannel with different wavelengths

In the present study, turbulent flow and heat transfer inside a three-dimensional wavy microchannel with different wavelengths have been numerically simulated. The main purpose of this study is to investigate the effects of changing the wavelength of the sinusoidal microchannel and CuO nanoparticle concentration on flow and heat transfer properties. For this reason, flow is simulated at Reynolds numbers of 3000, 4500, 6000, and 7500 with volume fractions of 0, 1.5, and 3% in three different geometries and the effects of each parameter have been investigated. Validation of the results showed there is an excellent agreement between the presented results with the previous studies. The average Nusselt number, pressure loss ratio, performance evaluation criterion, and local Nusselt number have been presented. Moreover, the distribution of the static temperature contour has been presented. In the flow with lower Reynolds numbers, the Nusselt number is not changed significantly; however, in flow with Reynolds number of 7500, the Nusselt number is increased. The performance evaluation criterion has the highest value in nanofluid flow with the volume fraction of 3%, indicating the effects of heat transfer with pressure drop caused by nanoparticles, and from engineering and economic perspectives, using nanoparticles in the wavy microchannel is recommended.

Investigation of the thermal separation in a counter-flow Ranque-Hilsch vortex tube with regard to different fin geometries located inside the cold-tube length

A Ranque-Hilsch vortex tube is a mechanical device in absence of any portable part or work input and significantly separates the inlet gas stream into hot and cold gas which provides a variety of applications. Current research consists a three-dimensional numerical model at steady state condition using installed fins on cold tube. Six different geometry were chosen for fins including triangle, square, rectangle, circle, parallelogram and trapezium. The outcome data of the research then is verified with compare to prior experiment results brought in literature. This article surveys the influence of different fin shapes on critical performance parameters of cold temperature difference, hot temperature difference, isentropic efficiency and COP numerically. The modeling results indicate that the parallelogram and rectangular fins have the highest and lowest cold temperature difference, isentropic efficiency and COP, respectively. It was also observed that the greatest COP and efficiency happens at pressure loss ratio equal to 0.65 at which, the optimum performance parameters of parallelogram fin for cold temperature difference, hot temperature difference, isentropic efficiency and COP were 35, 35.3, 0.279 and 33 respectively; whereas, these parameters were 30, 30, 0.255 and 23.9 for rectangular fin, respectively.

Optimization of Key Parameters of Two-way Inner and Outer Tube Differential Pressure Flowmeter

In view of the existing insufficient research on the parameters of the key structure of the two-way inner and outer tube differential pressure flowmeter, on the basis of the structure of the two-way inner and outer tube differential pressure flowmeter, the front and rear cone angles are respectively set. The study of the length of the thin tube for the bidirectional inner and outer tube differential pressure flowmeter was added. For the three structural parameters of the front cone angle α, the rear cone angle β, and the length of the thin tube l, nine sets of orthogonal tests were designed, which is different from the previous ones. The pressure loss ratio is proposed as the main evaluation index, and the simulation is performed by using FLUENT. By analyzing the results, the optimal combination is selected. Through simulation, the optimal model has good performance in measurement accuracy and pressure loss.

Effect of Side Gust on Performance of External Compression Supersonic Inlet

This Paper reports a computational investigation on the effects of side gust on the performance of a double-cone external compression supersonic inlet at Mach 1.8. The supersonic inlet geometry comprises three zones: a supersonic zone, a transit zone, and a subsonic zone. The supersonic zone is designed numerically using the Taylor–Maccoll method, while the transit and subsonic zones are designed using a methodology from literature. A three-dimensional structured mesh is generated by using the ICEM computational fluid dynamics software. Detailed three-dimensional simulations are performed using the ANSYS Fluent 18.2 code. The grid independency tests are performed by using local grid refinements and varying the number of grid points from 2.5 to 9.5 million. Further, the Fluent code is validated by comparing predictions with those using the SUPIN and Wind-US codes. The effects of side gust on the flowfield and oblique and normal shocks are analyzed by examining the Mach number and pressure distributions in the three zones. The inlet performance is characterized in terms of total pressure loss, flow distortion, and mass flow ratio parameters for a side gust of and gust angles of 30, 60, and 90 deg. Results indicate that the inlet performance is significantly affected by the side gust, especially at small gust angles.

Numerical investigation and improvement strategy of flow characteristics inside supersonic separator

ABSTRACTIn order to study the flow behavior and optimize separation performance, a three-dimensional numerical model of an improved supersonic separator was developed. The proposed model takes into account the compressible and strong swirling effect. Four widely-used turbulence models include Sparlart–Allmaras model, realizable k–ε model, shear-stress transport (SST) k–ω model, and Reynolds stress model (RSM) were validated and compared by the experimental date reported in the literature. The comparison results indicated that RSMs have great potential to predict the flow inside supersonic separator. Based on the established numerical model, the distribution of critical parameters such as temperature, pressure, and Mach number was obtained. The influence of the pressure loss ratio on the shockwave location occurred at the divergence section of the Laval nozzle was systematically studied. Analysis about the relationship between the pressure effect and shock wave location was carried out to explore the principal factors that limit the performance of the supersonic separator.

Numerical simulation of bubble separation length in a gas–liquid separator based on the Euler–Lagrange method

In this study, the bubble separation behavior in a gas–liquid separator is numerically investigated on the basis of the Euler–Lagrange approach, in which the forces acting on bubbles in a swirling flow field are modeled to calculate the trajectories of the bubbles. By adopting this approach, the effects of five parameters, namely, back pressure, Reynolds number, bubble diameter, void fraction, and swirl number, on separation performance in terms of pressure loss, separation efficiency, separation length, and split ratio are computed and analyzed. On the basis of the analysis, correlations of separation length with the two main parameters are established, which can serve as a basis for the optimal design of separator.

LES of Internal Combustion Engine Flows Using Cartesian Overset Grids

Accurate computations of turbulent flows using the Large-Eddy Simulation (LES) technique with an appropriate SubFilter Scale (SFS) model require low artificial dissipation such that the physical energy cascade process is not perturbed by numerical artifacts. To realize this in practical simulations, energy-conserving numerical schemes and high-quality computational grids are needed. If unstructured meshes are used, the latter requirement often makes grid generation for complex geometries very difficult. Structured Cartesian grids offer the advantage that uncertainties in mesh quality are reduced to choosing appropriate resolution. However, two intrinsic challenges of the structured approach are local mesh refinement and representation of complex geometries. In this work, the effectiveness of numerical methods which can be expected to reduce both drawbacks is assessed in engine flows, using a multi-physics inhouse code. The overset grid approach is utilized to arbitrarily combine grid patches of different spacing to a flow domain of complex shape during mesh generation. Walls are handled by an Immersed Boundary (IB) method, which is combined with a wall function to treat underresolved boundary layers. A statistically stationary Spark Ignition (SI) engine port flow is simulated at Reynolds numbers typical for engine operation. Good agreement of computed and measured integral flow quantities like overall pressure loss and tumble number is found. A comparison of simulated velocity fields to Particle Image Velocimetry (PIV) measurement data concludes the validation of the enhanced numerical framework for both mean velocity and turbulent fluctuations. The performance of two SFS models, the dynamic Smagorinsky model with Lagrangian averaging along pathlines and the coherent structure model, is tested on different grids. Sensitivity of pressure loss and tumble ratio to the wall treatment and mesh refinement is presented. It is shown that increased wall friction introduced by applying a wall model is overcompensated by some secondary effects, which lead to an overall reduction of pressure loss in the investigated engine geometry. Finally, dynamics of the statistically stationary valve jets are analyzed using Proper Orthogonal Decomposition (POD). Two distinct flow patterns are identified and the relevance for Cycle-to-Cycle Variations (CCV) is discussed.

Numerical Investigation on Diffusion Slot Hole With Various Cross-Sectional End Shapes

The diffusion hole constructed on a slot-type cross section has the potential to obtain high film cooling performance. However, the end shape of the cross section can greatly affect film cooling characteristics. This study examined eight cases of diffusion slot holes with various cross-sectional end shapes. The comparison of the eight diffusion slot holes and a typical fan-shaped hole was performed with a flat plate model using a three-dimensional (3D) steady computational fluid dynamics (CFD) method. The rectangular cross section had an aspect ratio of about 3.4. The end shape variation can be described based on sidewall contraction location, size, and form. The simulations were performed under an engine-representative condition of mainstream inlet Mach number 0.3 and turbulence intensity 5.2%. The simulated results showed that a strip separation bubble caused by inlet “jetting effect” occurs near the downstream wall of the diffusion slot hole and interacts with the diffusion flow. The different end shape of the rectangular cross section leads to different sidewall static pressure and exit velocity profiles, thereby produces three cooling effectiveness patterns, single-peak, bipeak, and tripeak patterns. The tripeak pattern produces higher cooling effectiveness and relatively uniform film coverage. The structure with moderate contraction and smooth transition on two sides of the downstream wall favors creation of a tripeak pattern. Compared with the fan-shaped hole, the discharge coefficient of diffusion slot hole is slightly small in low pressure ratio range, the pressure loss ratio has little difference.

Structure improvements and numerical simulation of supersonic separators

In the separation process of the conventional supersonic separator, the shockwave easily occurs in the nozzle expanding section before the cyclone, the low temperature section is short and the cooling effect is not satisfied, and the swirling flow occurs in subsonic conditions with poor efficiency. Based on this, structure improvement of the supersonic separator was carried out by reducing the nozzle expand angle and extending the length of expanding section, which helps to improve the refrigeration performance and separation efficiency of the separator. The flow characteristics of natural gas in the improved supersonic separator were obtained by three-dimensional numerical simulation. The results show that the shockwave occurs in the back of the cyclone and the improved supersonic separator can achieve a wider range of deep cooling. The shockwave moves back with the increase of the pressure loss ratio, when the pressure loss ratio increases to 70%, the position of shockwave moves back to the diffuser. The numerical results show that when the inlet pressure is 600kPa and the pressure loss ratio is 47.5%, the improved supersonic separator has a good cooling and separation performance.

직선형 냉각채널에서의 압력손실에 대한 실험적 연구

액체로켓엔진에서의 재생냉각 채널은 높은 온도의 연소가스로부터 연소실 내벽을 효율적으로 냉각하기 위해 사용되며, 냉각채널 설계를 위해서는 열전달 특성과 압력손실 특성을 미리 예측하여야 한다. 본 연구에서는 서로 다른 형상을 갖는 5개의 냉각채널을 설계하고, 커터와 엔드밀로 채널을 제작하였다. 채널을 흐르는 유속과 후단 압력조건을 달리하여 가공방법, 채널 형상, 유동조건에 따른 압력손실을 실험적으로 측정하여 해석결과와 비교를 수행하였다. 동일 형상 및 유동조건에서 커터로 가공된 채널이 엔드밀로 가공된 채널보다 압력손실이 적었다. 또한 채널 형상, 유동조건에 따라 실험결과와 해석결과의 압력손실 비가 달라짐을 확인할 수 있었다. A regeneratively-cooled channel in a liquid rocket engine is used to effectively cool a combustion chamber inner wall from hot combustion gas, and the heat transfer/pressure loss characteristics should be predicted in advance to design cooling channels. In the present research, five cooling channels with different geometric dimensions were designed and the channels were respectively manufactured using cutter and endmill. By changing coolant velocity and downstream pressure, the effects of manufacturing method, channel shape, and flow condition on pressure losses were experimentally investigated and the results were compared with the analytical results. At same channel shape and flow condition, the pressure loss in the channel machined by the cutter was lower than that by the endmill. It was also found that the pressure loss ratio between the experimental result and the analytical data changed with the channel shape and flow condition.

Online measurement of gas and liquid flow rate in wet gas through one V-Cone throttle device

In the present study, an accurate cost-effective online system for metering both the gas flow rate and the liquid flow rate in wet gas with only one V-Cone throttle device is developed. The two-phase mass flow coefficient is employed to correct the measurement deviation of the V-Cone throttle device. The effects of the liquid densiometric Froude number, the gas densiometric Froude number and the ratio of gas density to liquid density on the two-phase mass flow coefficient are experimentally investigated. The equivalent diameter ratio of the V-Cone throttle device is 0.55. The experimental fluids are air and tap water. The operating pressure, the superficial gas velocity and superficial liquid velocity range from 0.1MPa to 0.3MPa, 4.87m/s to 25.26m/s and 0 to 0.38m/s, respectively. The results show that the two-phase mass flow coefficient linearly increases with the liquid densiometric Froude number and is affected by the gas densiometric Froude number and the ratio of gas density to liquid density. On the basis of the two-phase mass flow coefficient, the correlation for measuring the gas flow rate of the wet gas is developed. To reflect the influences of the liquid on the measurement, the pressure loss ratio of the V-Cone throttle is proposed. By incorporating the gas measurement correlation of the wet gas, the wet gas correlations to simultaneously meter the gas and liquid flow rate are concluded. In the present cases, the relative error of the gas mass flow rate predicted by the correlations is within ±5.0% and the mean absolute percentage error is 2.52%; the full scale relative error of the liquid mass flow rate is within ±5.0% and the mean absolute percentage error is 7.03%. The method proposed in this study creates a simple inexpensive wet gas metering system that can operate well in a significant range of industrial applications.

Experimental research on pressure drop of wet gas flow in Venturi

In the research of wet gas, the pressure drop is an important parameter in the design of the pipelines and the selection of the wet gas flow meters. Although an algorithm is described in the ISO11583 technical report that used to predict pressure loss ratio (PLR), the exploration of this method still need to be studied under the different flow conditions. A new correlation of pressure drop is proposed based on the important influence factors. Dimensional analysis is adopted to find the significant dimensionless parameters to establish the correlation of PLR, such as Lockhart–Martinelli parameter and gas Froude number. The experiment of the Venturi tube has been carried out in the wet gas flow loop of Tianjin University. In the test, the static pressure of pipe ranged from 0.2 to 1.2MPa and the superficial gas velocity ranged from 5 to 10m/s. Results implied that the correlation of ISO11583 gave an unsatisfactory prediction of PLR. In order to improve the accuracy, the new correlation in this work was based on the dimensional analysis and experimental data. Finally, the average relative error of this correlation is about 3.85% and the root mean square error is about 2.5%.

New Simplified Approach for Hydraulic Design of Micro-Irrigation Paired Laterals

A simple, direct, and easily adaptable analytical approach was developed for the hydraulic design of micro-irrigation paired laterals laid on uniformly sloping ground based on the locations where the same average emitter pressure head exists in the uphill and downhill laterals. Analytical expressions of the best manifold position, inlet working pressure head, maximum pressure difference, and water application uniformity of the paired laterals were separately developed using the energy gradient line method. All equations of the design parameters were regression analyzed by the numerical fitting technique with the specific velocity exponent and the pressure loss ratio of a single downhill lateral with the same length as the paired laterals. When the length, diameter, and designed emitter flow were given, the best manifold position and other parameters of the paired laterals could be directly designed without using iterative methods. When the designed emitter flow, water application uniformity criterion, and one parameter (either diameter or length) were provided, the other parameter, best manifold position, and the remaining parameters of the paired laterals could be easily determined by Equation Solver in Microsoft Excel. A comparison test with three numerical design examples covering various conditions indicated that the proposed approach could produce accurate results for practical purposes. By using the developed analytical expressions and regression relationships, the proposed approach provided a simpler and more adaptable design procedure than the traditional analytical methods. The proposed procedure is preferred to the numerical techniques, which need large amounts of execution time and complex computer operations. The proposed procedure also provided the chance to evaluate the influence of local energy losses on the hydraulic designs of paired laterals for a given uniformity level.

Effect of jet nozzle geometry on flow and heat transfer performance of vortex cooling for gas turbine blade leading edge

In this paper, 3D viscous steady Reynolds Averaged Navier–Stokes (RANS) equations are utilized to investigate the influence of jet nozzle geometry on flow and thermal behavior of vortex cooling for gas turbine blades. Comparison between calculation with different turbulence models and the experimental data is conducted, and results show that the standard k-ω model provides the best accuracy. The grid independence analysis is performed to obtain the proper mesh number. First, the mechanism of vortex cooling is further discussed, and the pronounced impact of kinetic turbulence intensity, thin thermal boundary layer, violent radial convection and complex vortices on enhanced heat transfer performance is confirmed. Then, seven jet nozzle aspect ratios and seven jet nozzle to chamber cross section area ratios are selected to research the flow field and thermal characteristics of vortex cooling focusing on the streamline, static pressure ratio, total pressure loss ratio and Nusselt number. It is presented that the jet nozzle aspect ratio and jet nozzle to chamber cross section area ratio both impose a significant effect on the flow and thermal parameters. The averaged Nusselt number decreases at first and then increases with the increasing jet nozzle aspect ratio, reaching highest when aspect ratio equals to 1. The effect of area ratio on averaged Nusselt number is complex. Finally, the heat transfer results in this study are compared with other previous works. Results indicate that good agreement with previous data is achieved, and the enhanced thermal behavior may be acquired by carefully designing and optimizing the vortex chamber geometry.

Experimental investigation on the performance of improving jet pump cavitation with air suction

In order to improve the jet pump cavitation, a new method of inhaling air into the low-pressure region was proposed, and its performance was investigated experimentally under different air suction quantity and cavitation levels. Test results show that the cavitation number increases with the air suction quantity increasing in a linear approximation fashion. Increasing air suction quantity corresponds to a sharp decrease in acoustic noise, especially for the severe cavitation. As the air suction quantity increases, the pressure fluctuation range and fluctuation variance both decrease in the downstream, which relieve the cavitation vibration damage and enhance the jet pump stability. In addition, the pressure loss ratio reduces by 0.95%–3.46% and the pressure ratio increases by 5.7%–18% due to the water–air cushion layer formed in the wall boundary. The marked effect on preventing cavitation damage and improving the pressure transmission performance of the jet pump proves that the new air suction method proposed is practical and effective. Therefore, it is believed that this study would lay an important foundation for the widespread application of jet pump in the future.

A New Design of Double-Stage Parallel Adding Equipment Used for Dust Suppression in Underground Coal Mines

In order to solve the problems of conventional single-stage adding equipment, such as high adding proportion, easy to generate cavitation, large pressure loss and low pressure ratio, an original design of double-stage parallel adding equipment is proposed. Its performance is investigated experimentally under different working flow and outlet pressure and compared with the single-stage jet equipment. Testing results show that the adding proportion of double-stage parallel adding equipment is less than that of the single-stage one, and the cavitation flow is higher. The new equipment can decrease pressure loss, inlet pressure and improve pressure ratio, which lowers the energy loss of adding equipment and raises its driving ability in application. An adding proportion of 4.6 ‰ and an outlet pressure of 0.16–0.18 MPa were realized when the double-stage parallel adding equipment was used to add foaming agent for dust suppression with foam (DSF). The marked reduction in the adding proportion of foaming agent significantly reduces foam production cost. Therefore, it is believed that the study would lay an important foundation for the widespread application of DSF in underground coal mines.

Fuzzy Comprehensive Evaluation of the Suitability of Downhole Inflow Control Device in Sandstone Reservoir

The downhole inflow control device (ICD) could control the production profile of every section in horizontal well and the edge and bottom water coning, so it is important in enhancing oil and gas recovery. To quantitatively depict ICD's suitability in horizontal wells requires analyzing reservoir parameters like permeability variation coefficient, average permeability, the ratio of vertical permeability to horizontal permeability and the technology parameters like tube string size, horizontal section length, segment number and the pressure loss ratio between ICD and reservoir. With fuzzy mathematical method, this work has analyzed these factors through relative subordinate function and established the fuzzy comprehensive evaluation model to study the suitability of ICD in sandstone reservoirs by the weight of each factor and fuzzy relationship matrix. The fuzzy evaluation and simulation results prove this method could well evaluate the suitability of ICD in sandstone reservoirs and it is significant for the application of ICD in horizontal well development.

Ｄｅｓｉｇｎ‐ｂｙ‐Ａｎａｌｙｓｉｓと試験による低圧損気水分離器の開発（Ｉ）解析の妥当性確認および低圧損スワラーの設計

The purpose of this study is to develop a steam separator for BWR with low pressure loss by CFD and a scale model test. The swirler is the key component for the separation performance and pressure loss. Therefore, we have focused on the improvement of the swirler and tried to improve the swirler geometry to reduce the swirler pressure loss while maintaining the separation performance. This study consists of two stages. In the first stage, we measure pressure loss and water discharge ratio using the 1/2.22-scale test under BWR operating pressure, and then validate the CFD method by comparison with the scale test results. In the second stage, we improve the swirler geometry by the survey of some geometry factors using CFD. We predict that the inlet and outlet pressure losses of the swirler are dominant in the separator. By improving the geometry at the inlet and outlet of the swirler, we show from the results of CFD and a scale test that the improved swirler can reduce pressure loss by about 50% compared with the conventional swirler.

A study on supersonic mixing by circular nozzle with various injection angles for air breathing engine

SCRAM-jet engine is considered to be one of the useful system propulsion for super/hypersonic transportation vehicle and various researches were made to develop the engine. However, there are a lot of problems to be solved to develop it and one of them is the problem of supersonic mixing. In the SCRAM-jet engine combustor, main airflow is supersonic and residence time of the air is very short (about 1 ms). Hence rapid mixing of air and fuel is necessary. However, usually it is quite difficult to mix fuel with air in very short distance. Also total pressure loss occurs by flow interaction the air and fuel. Total pressure loss is not preferable because it causes the thrust loss. Therefore, supersonic mixing with very rapid mixing and lower total pressure loss ratio is highly requested. In order to develop the supersonic mixing, it is very important to understand the effect of injection angle. In present study, we investigate the effect of injection angle with circular sonic nozzle by changing the injection angle. Experimental and computational studies on supersonic mixing phenomena of two-dimensional slot injector with various injection angles were conducted. Supersonic wind tunnel was used for the experiments. The free stream Mach number is 3.8, total pressure is 1.1 MPa and total temperature is 287 K on average. As a secondary gas, helium gas was injected at sonic speed from the circular nozzle. The injection angle is 30°, 90° and 150°. Its total pressure is 0.4 MPa and total temperature is 287 K on average. The same flow field was also simulated by solving three-dimensional full Navier–Stokes equation with AUSM-DV scheme [Y. Wada, M.S. Liou, A flux splitting scheme with high-resolution and robustness for discontinuities, AIAA Paper 94–0083, 1994] for convective terms and full implicit LU-ADI factorization method [S. Obayashi, K. Matsushima, K. Fujii, K. Kuwahara, Improvements in efficiency and reliability for Navier–Stokes computations using the LU-ADI factorization algorithm, AIAA Paper 86–0338, 1986] for time integration. Central difference was used for viscous terms and k – ω two-equation turbulence model [D.C. Wilcox, Reassessment of the scale determining equation for advanced turbulent models, J. AIAA 26(11) (1988) 1299–1310; D.C. Wilcox, A two-equation turbulence model for wall-bounded and free-share flows, AIAA Paper 93–2905, 1993] was also employed. In the experiments, stream line on the wall surface was revealed by the oil flow picture and the flow field was visualized by the Shlieren photograph. The wall static pressure profile along the flow was obtained by the wall pressure measurements. Also volume fraction distribution measurements were conducted. Each one of those showed good agreement with computational ones. From the thorough investigation of the flow field by experiments and computations, various characteristics of the supersonic mixing with circular nozzle have been revealed.