Intake Flow Field Research Articles

CFD Prediction of Ramjet Intake Characteristics at Angle of Attack

The characteristics of installed intakes of a ramjet engine at angle of attack are predicted numerically. Three dimensional Navier Stokes equations are solved alongwith k - ε turbulence model using commercial CFD software. The software was first validated for isolated intake and computed results match very well with theoretical results available in literature. Pressure recovery Vs. mass flow characteristics of four installed intakes placed in a rear location of a ramjet vehicle is evaluated at different angles of attack upto 6°. Intake performance matches reasonably well with experimental results. It has been observed that significant variation of intake performance exists between windward and leeward intakes. For higher angle of attack, the leeward intake move towards the subcritical operation faster and the intake flowfield is seen to interact with the corebody boundary layer causing significant spillage.

Numerical Investigation of Aerodynamic and Electromagnetic Performances for S-Duct Caret Intake with Boundary-Layer Bleed System

This study presents the numerical results for the aerodynamic and electromagnetic performances of an S-duct caret intake. Using the multilevel fast multipole method (MLFMM) to solve Maxwell equations, the current on the intake surface is calculated, and the radar cross-section (RCS) is analyzed. Moreover, the intake flow field is numerically investigated using the SST k–ω turbulence model to solve the Reynolds-averaged Navier–Stokes equations. Compared to a straight intake, for an S-duct caret intake, the average RCS is lower by 7.65 dB, and the maximum RCS difference value caused by the blade rotation is lower by 6.75 dB. However, the flow capacity deteriorates when the total pressure recovery coefficient decreases by 0.004. Based on the analysis of the aerodynamic and electromagnetic characteristics of different intakes, a double S-duct intake is designed. Compared to a traditional S-duct intake, for the novel intake after model parameter modification, the average RCS is lower by 0.05 dB, and the total pressure distortion (TPD) is lower by 0.18. The analysis of the effects of different boundary-layer bleed systems shows that the symmetrical layout adversely affects the aerodynamic and electromagnetic performances of the S-duct intake, but the unilateral partial layout is beneficial, whose TPD is lower by 0.04 and average RCS is higher by −2.17 dB compared to a straight intake.

Effects of boundary-layer bleed parameters on supersonic intake buzz

Extensive wind tunnel tests were conducted to study effects of the location, entrance slant angle, entrance width, and type (slot or porous) of boundary layer bleed on the buzz phenomenon in a supersonic air intake. The intake was a mixed-compression axisymmetric intake for the design Mach number of 2.0 that was studied at zero degrees angle of attack at three free stream Mach numbers of 1.8, 2.0, and 2.2 through shadowgraph visualization system and pressure recordings. For every free stream Mach number and bleed geometry, eight different back pressures were examined. Results showed that the bleed can significantly postpone the buzz onset and increase the stability range of the intake. The bleed location was the most effective parameter among the examined parameters of the bleed system. According to the results, the bleed restricts the domain of shock oscillations to downstream of the bleed entrance and consequently, it increases the frequency of buzz as compared with the no-bleed case. In addition, the slot bleed is more effective in stabilizing the intake flow field than the porous bleed.

Effects of upstream vortex generators on the intake duct performance for a waterjet propulsion system

This paper investigates the effects of vortex generators (VGs) on the flow separation in the intake duct for a waterjet propulsion system. A row of plate VGs is installed on the ship hull bottom upstream before the intake entrance. Flow's RANS equations are solved with the standard SST turbulence model to simulate the flow field inside the intake duct. Results show that the flow separation along the intake ramp wall is restrained leading to improved flow's uniformity before entering the waterjet pump. The VG effects on the intake flow field at various Inlet Velocity Ratio (IVR) conditions are elucidated from the aspects of vortex distribution, flow separation and overall performance. The VG induced extra vortices increases the fluid momentum near the duct ramp wall. The inflow distortions of axial flow velocity and total pressure are reduced before the suction pump. At the designed operation conditions, the flow's hydraulic efficiency flow through the intake duct is increased by 4.3 percent. Compared with the intake duct prototype, the total pressure distortion index on the duct outflow plane is reduced by 37.9 percent. The outflow's uniformity is decreased by 15.8 percent. Miniature shaped VGs have yielded evident improvements on the intake hydraulic performances.

Numerical study of intake flow field inside the high-speed refrigeration scroll compressor with spiral suction channels in the motor rotor

To control the temperature of the electric motor, the suction gas is introduced flowing through the motor in hermetic scroll compressors. For high-speed compressors, this flow resistance is high, which results in decreasing of the efficiency. In this paper, spiral flow channels were designed inside the motor rotor to decrease the suction flow resistance and increase the refrigerant flow rate inside the scroll compressor. Simulation of the suction flow through the motor was carried out. Two structure of straight and spiral intake channels were brought into the simulation model, under 3000 rpm, 5000 rpm, 7000 rpm and 9000 rpm. The results showed that the spiral channels could increase the refrigerant flow rate inside the motor rotor and the suction pressure of the compressor, and with the increase of the motor speed, the effect of the intake supercharging improved. At 9000 rpm, the suction pressure at the suction port of the compressor increased by about 4% by using spiral channels, while the mass flow rate increased by about 6%. The increases of total refrigerant flow rate in spiral channels are mainly due to the increase in unblocked channels. The size and the layout of the balance weight have a great effect on intake flow.

Numerical investigation of axisymmetric intake flowfield and performance for scramjet-powered ascent flight

Air intakes play a crucial role in the operation of scramjet engines, one of the most promising hypersonic airbreathing propulsion technologies for efficient and flexible space transportation, it is thus essential to accurately understand and predict the flowfields for high-performance intake design, especially in varying operating conditions. Axisymmetric intake flowfields are investigated numerically assuming a typical scramjet operation on a constant dynamic pressure ascent trajectory, aiming to achieve scramjet-powered access-to-space. Physical insight into scramjet flowfields at various flight altitudes and Mach numbers have been gained by means of high-resolution simulation to resolve the viscous flowfields. High levels of adaptive mesh refinement have identified detailed flow phenomena including shock reflection, interactions, and boundary layer as well as their aerodynamic and aerothermal effects on pressure and temperature fields. In particular, Mach reflection characterized by a Mach disk has been found to occur at the centerline, even in the operating conditions where regular reflection would result from computational simulation without mesh adaption. The intake performance has been evaluated with respect to the compression efficiency, drag, and exit temperature. The intake drag has been found to decrease at higher Mach numbers at higher altitudes on a constant dynamic pressure trajectory during acceleration due to reduced pressure drag while viscous drag varies little. Rather little influence of varying wall conditions has been observed on the intake drag between the isothermal and adiabatic wall conditions due to counteracting behavior between viscous and pressure drag components.

CFD Numerical Simulation for Intake Flow Field Design and Effects on Combustion and Emissions of DI Diesel Engine

The article takes a gander at inevitable results of logical leisure with whirl enhancing modifications on a right away Injection diesel engine. 4 holes at a diversion over every chamber with estimations of the outlet start from 2, 2.five, 3 and 3.5 mm are through within the chamber with affordable tendency concerning the chamber center factor Numerical guesses are the first-class change to provide clean enduring of the fluid circulate wonder in a DI Diesel Engine. outcomes discover that the unessential beginning of two.five mm (2nd) bypass on an unequalled begin and excessive weight. Spin development just motor vitality massiveness increment with the changing starting widths. The chamber with 2.five mm establishing make a most vital execution improvement while the chambers with excessive broadness than second hole bypass on a to a few diploma chop down execution. whilst the development in partition transversely over develops the move discipline characteristics like spin, the execution decays beyond 2.five mm. considering the execution attitude an ensuing hole gives improved ingesting and finally most outrageous load for the proportional gas implanted. alternate ultimate holes have to a few diploma more fiery debris launch. in view that numerical results exhibited that ensuing hole offers a transcendent. Of all of the splendid numerical modifications the resultant chamber gives stepped forward presentation and lessens the fee and dreary experimentation tests.

Study on dynamic characteristics of intake system and combustion of controllable intake swirl diesel engine

This paper investigated the intake flow field of a controllable intake swirl diesel engine using computational fluid dynamics (CFD) methodology. It can be observed that the variation of the intake swirl with the opening of the intake baffle shows the two-stage characteristics, while the baffle opening angle of 48° is as a cut-off point. Through the comprehensive analysis of the influence of valve lift and baffle opening angle on flow coefficient, it is concluded that the influence of valve lift on flow coefficient is more sensitive. A mathematical method is used to fit the formula which can calculate the key characteristics of the controllable intake swirl diesel engine. Meanwhile the influence of the swirl ratio on combustion characteristics is investigated. It can be concluded that the swirl ratio has greater influence on the power performance of the diesel engine. When the swirl ratio increases from 0.4 to 1.2, the power performance is increased by 5.79%, and the fuel consumption was also improved. Finally, according to the actual structure of the intake system of diesel engine, a steady-state intake flow test bed was established to verify the accuracy of CFD study of the intake system.

LES analyses of the air-core vortex in intake flow field of pumping station

Air-core vortex is a universal and attention-getting phenomenon in intake flow field of pumping station. Due to the difficulties and complexities of two-phase flow of the air-core vortex, the Coupled Level-Set and Volume-of-Fluid (CLSVOF) method is adopted in the simulation, and a horizontal intake pipe in pump sump was calculated. Results of the simulation were consistent with that of experiment. The air-core vortex is successfully reproduced in the simulation, and four stages during its formation is observed. At the early stage of the simulation, vortices generated in the vicinity of the free surface are gathered in the stagnation region above the pipe intake. The intensity of the gathering vortices increases due to the stretching effect of ωy (vertical vorticity component), and move toward to the pipe intake due to the downward flow motion of the stagnation region. Furthermore, air-core vortex meandering is observed from the time series of instantaneous vortex motion, and quasi-periodicity is founded in its meandering, which is caused by the quasi-periodic characteristic of the velocity filed. The dominant frequency (fD/vD) of coordinate x of the air-core vortex center is around 0.0096, and coordinate z is around 0.0191.

Numerical simulations of an intake-compressor system

Integrated propulsion plays a major role in future civil and military aircraft design. A key component of these systems are highly bent intake geometries. As the flow passes through such ducts, combined total pressure and swirl distortions are generated which have a negative impact on compressor performance, safety margin, and durability. Due to weight and space limitations, a close coupling of intake and compressor is necessary. An experimental test case including a highly bent intake geometry and a state of the art turbofan engine was established and extensive measurement data was acquired. This publication compares results of three different numerical approaches to this test data: Isolated intake simulations, isolated compressor simulations with distorted inflow conditions, and a coupled simulation of intake and three stage compressor. The isolated intake simulation is able to reproduce the static wall pressure field of the intake as well as the occurring flow separation. Towards the interface plane to the compressor however, significant deviations are observed. The upstream effect of the compressor working under the combined pressure swirl distortion is assessed via the second simulation approach. The influence of the swirl and total pressure distortion on the compressor is first simulated separately and then compared to the impact of the combined distortion. The coupled intake-compressor simulation reveals the manipulation of the intake flow field by an upstream static pressure field. In contrast to experiments a slightly unsteady operation point and an asymmetric intake flow field were observed.

Numerical simulation on rectifying flow in intake system of a pumping station connected with headrace pipe

Pipes are usually adopted in those conditions for which the pump house is far from water source. As for fore-bay, flow of headrace pipe can be considered as jet-flow. Jet-flow has a high velocity, and creates large pressure gradient between jet-flow and near wall flow, which contributes to large scale circulation. In that circumstance, a single rectification measure cannot effectively improve the flow pattern of intake flow field. For large scale pumping station, there is enough space to arrange complex anti-vortex devices. Thus, a new type of combined diversion piers composed of double-I type pier, three-I type pier and cross anti-vortex baffle was proposed. In order to investigate the influences of combined division piers on flow pattern, four cases with different geometry and location parameters are designed. The results of numerical simulation and site tests show that the combined diversion piers could effectively improve the intake flow field of pumping station with headrace pipe. As for pumping station with headrace pipe, the distance between inlet section of fore-bay and leading edge of double-I type diversion pier should be 0.25L-0.53L (where L is the length of fore-bay). The distance between inlet section of fore-bay and trailing edge of double-I type diversion pier should be 0.5L-0.73L. The total length of double-I type pier should be 0.2L-0.25L.

Low Frequency Distortion in Civil Aero-engine Intake

The main role of the intake is to provide a sufficient mass flow to the engine face and a sufficient flow homogeneity to the fan. Intake-fan interaction off design represents a critical issue in the design process because intake lines are set very early during the aircraft optimization. The offdesign operation of an aero-engine, strictly related to the intake flow field, can be mainly related to two different conditions. When the plane is in near ground position, vorticity can be ingested by the fan due to crosswind incidence. During the flight, distortions occur due to incidence. In these conditions, the windward lip is subjected to high acceleration followed by strong adverse pressure gradients, high streamline curvature, and cohabitation of incompressible and transonic flow around the lip. All these features increase the risk of lip stall in flight at incidence or in crosswind near ground operation and increase the level of forcing seen by the fan blades because of the interaction with nonuniform flow from the intake. This work deals with the study of two sources of distortions: ground vortex ingestion and flight at high incidence conditions. A test case representative of a current installation clearance from the ground has been investigated and the experimental data available in open literature validated the computational fluid dynamics (CFD) calculations. An intake, representative of a realistic civil aero-engine configuration flying at high incidence, has been investigated in powered and aspirated configurations. Distortion distributions have been characterized in terms of total loss distributions in space and in time. The beneficial effect of the presence of fan in terms of distortion control has been demonstrated. The mutual effect between fan and incoming distortion from the intake has been assessed in terms of modal force and distortion control. CFD has been validated by means of comparisons between numerical results and experimental data which have been provided. Waves predicted by CFD have been compared with an actuator disk approach prediction. The linear behavior of the lower disturbance frequency coming from distortion and the waves reflected by the fan has been demonstrated.

Coupled Analytical-Numerical Procedure to Solve the Double Wedge Spiked Supersonic Intake Flow Field

Designers of the aero engines are in quest of maintaining the pressure as high as possible at the face of the compressor, with air velocity not higher than 0.8 Mach. Reduction of the flow from supersonic to such speed is combined with pressure reduction. This paper presents results from coupled techniques to solve for the flow field of double wedge spiked supersonic intake. The selected spike has 4° forebody wedge angle and the second ramp angle is 8°. The external part of the flow was solved analytically while the internal part was solved numerically by finite volume technique. The analysis was carried out at different Mach numbers (1.4, 1.8, 2.2, 2.4, and 3) and different angles of attack (0°, 6°, and 12°). The procedure is validated and the results are presented in terms of the pressure recovery at the face of the compressor. The results have shown that generally the pressure recovery decreases by increasing of incidence angle. The non-zero incidence was found to produce noticeable difference in pressure distribution at the face of the compressor. This became considerably effective at incidences leading to detached shocks at the leading edge of the spike.

9733215 Analysis of intake flow field with a rotary valve system Yasuo Moriyoshi (Chiba Univ.), Takumi Muroki (Kanagawa Tech. Inst.), Susumu Sekizuka (Chiba Univ. Graduate)

9733215 Analysis of intake flow field with a rotary valve system Yasuo Moriyoshi (Chiba Univ.), Takumi Muroki (Kanagawa Tech. Inst.), Susumu Sekizuka (Chiba Univ. Graduate)