Inward-turning Inlet Research Articles

An Inverse Design Method for Non-uniform Flow Inlet with a Given Shock Wave

For the hypersonic inlet and fore-body integrated design, the non-uniform incoming flow generated by the fore-body will bring a relatively big challenge to the inward-turning inlet design. To make the inlet match the non-uniform incoming flow, this paper, based on previous studies, develops a cross-stream marching plus (CSMP) method, by which an aerodynamic surface used to generate a given shock shape can be acquired. The method can correct such solution points as may give rise to grid distortions or flow-field abnormity and overcome the shortcoming of the insufficient stability of previous methods. Numerical simulation results of the conical supersonic flowfield show that the error obtained from the proposed CSMP method drops with the reduction of the grid dimension and the marching step, being less than 0.05% for reducing the marching step to 10%; that with this method the maximum relative error of the pressure on the profile is less than 0.23%. In the design process of the inward-turning inlets that match the fuselage fore-body, it’s found that in comparison with the results of the inviscid CFD results, the aerodynamic surface designed with the CSMP method can fully generate the given shock wave shape. Thus, the CSMP method provides a new direction for the inlet/fore-body integrated design.

Design of a Three-Dimensional Hypersonic Inward-Turning Inlet with Tri-Ducts for Combined Cycle Engines

The operation of a propulsion system in terms of horizontal takeoff/landing and full-speed range serves as one of the main difficulties for hypersonic travelling. In the present work, a three-dimensional inward-turning inlet with tri-ducts for combined cycle engines is designed for the operation of three different modes controlled by a single rotational flap on the compression side, which efficiently simplifies the inlet structure and the flap control mechanism. At high flight speed between Mach 4 and 6, the pure scramjet mode is switched on, whereas both the ejector and the scramjet paths are open for a moderate Mach number between 2 and 4 with a larger throat area guaranteeing the inlet startability. In the low flight speed range with Mach number below 2, the additional turbojet path will be turned on to supply air for the turbine engine, whereas the other two paths remain open for spillage. Numerical simulations under different operation modes have proven the feasibility and good performance of the designed inlet, e.g., a nearly full mass flow ratio and a total pressure recovery around 0.5 can be achieved at the cruise speed. Meanwhile, the inlet works properly at low flight speeds which overcomes the typical starting problem of similar inlet designs. In the near future, wind tunnel experiments will be carried out to validate our inlet design and its performance.

Unsteady shock interactions on V-shaped blunt leading edges

The unsteady dynamics of shock interactions on the crotch of two typical V-shaped blunt leading edges have been investigated numerically and experimentally with a freestream Mach number 6 for different ratios (R), defined as the rounding radius at the crotch to the blunt radius at the leading edge. The primary flow features observed in the shock tunnel experiments are reproduced by the large-eddy simulations. The time-averaged flow structures in the crotch are clearly shown as counterrotating vortices originating from the collision of jets near the stagnation point. These jets and vortices undergo unsteady motions coupled with the dynamics of shock interactions. Of great interest, two typical global oscillations, i.e., swing oscillation and arch-recover oscillation corresponding to the two values of R, are identified. The coherent structures of the oscillations are analyzed using the proper orthogonal decomposition technique. It is demonstrated that the swing oscillation and arch-recover oscillation are characterized by an antisymmetric pattern and a symmetrical pattern, respectively. These two oscillations are also characterized by the energetic middle-frequency components of the broadband wall pressure spectra. Two feedback models are proposed for the prediction of such middle-frequency components. The results show that the swing oscillation causes much more severe pressure load, and the local impingement of the transmitted shock on the crotch is responsible for the peak value of the pressure fluctuation. This study illustrates that the geometry of R has a key impact on the unsteady shock interactions and, therefore, should be considered critically in practical applications, such as the cowl lip of a hypersonic inward-turning inlet.

Aerodynamic configuration integration design of hypersonic cruise aircraft with inward-turning inlets

In this work, a novel airframe/propulsion integration design method of the wing-body configuration for hypersonic cruise aircraft is proposed, where the configuration is integrated with inward-turning inlets. With the help of this method, the major design concern of balancing the aerodynamic performance against the requirements for efficient propulsion can be well addressed. A novel geometric parametrically modelling method based on a combination of patched class and shape transition (CST) and COONs surface is proposed to represent the configuration, especially a complex configuration with an irregular inlet lip shape. The modelling method enlarges the design space of components on the premise of guaranteeing the configuration integrity via special constraints imposed on the interface across adjacent surfaces. A basic flow inside a cone shaped by a dual-inflection-point generatrix is optimized to generate the inward-turning inlet with improvements of both compression efficiency and flow uniformity. The performance improvement mechanism of this basic flow is the compression velocity variation induced by the variation of the generatrix slope along the flow path. At the design point, numerical simulation results show that the lift-to-drag ratio of the configuration is as high as 5.2 and the inlet works well with a high level of compression efficiency and flow uniformity. The design result also has a good performance on off-design conditions. The achievement of all the design targets turns out that the integration design method proposed in this paper is efficient and practical.

Design of shape morphing hypersonic inward-turning inlet using multistage optimization

To make a compromise between compression efficiency and aerodynamic performance, a novel multistage optimization approach is proposed to improve the design of the shape morphing hypersonic inward-turning inlet. In the first stage, a parent flow inside an internal cone shaped from a special dual-inflection-point generatrix is optimized for the improvements of total pressure recovery and flow uniformity. The second stage is established to design the inlet lip shape via a single-objective optimization aiming to minimize the inviscid drag of the inlet. For rapidly predicting the inlet inviscid drag, we propose a streamline integral method characterized by high levels of computational efficiency and accuracy. The last stage is auxiliary to improve the practicability, mainly including an algebraic shape transition to regulate the inlet exit shape. Numerical results demonstrate that both the flow non-uniformity and the total pressure loss of the optimized parent flow are decreased significantly compared with the baseline parent flow. With the optimized lip shape, the inlet inviscid drag per unit mass flow rate is decreased as well. A simple quadratic function is the best choice to achieve the shape transition, which is beneficial to improve the inlet practicability with a less performance loss. With the multistage optimization framework, the improvements of the compression efficiency and the aerodynamic performance are both achieved and the balance between them is carefully manipulated as well. All the above demonstrates that the proposed optimization approach for the design of the shape morphing hypersonic inward-turning inlet is practical and efficient.

Preliminary Integrated Design of Hypersonic Vehicle Configurations Including Inward-Turning Inlets

AbstractA design method employed for preliminary integration of a hypersonic vehicle airframe configuration with its propulsion flow path is described. This method is primarily based on the integration of the variable cross section inward-turning inlet and the airframe. Three typical configurations include lifting body, sim-waverider, and semi-axisymmetric cone. Rectangular-to-circular, erose-to-circular, and sector-to-circular shape transition Busemann inlets are designed to integrate these three vehicle bodies, respectively. The results of numerical simulations show that the aerodynamic performance of these configurations, coupled with the propulsion flow path, inherits the characteristics of their original airframe shapes, such as the high lift/drag ratio of sim-waverider and the low-drag performance of semi-axisymmetric cone configuration. The computed results also demonstrate that the inward-turning inlets integrate smoothly with their respective vehicle airframes and that the design method is viable.

Three-Dimensional Analysis of a Supersonic CombustorCoupled to Innovative Inward-Turning Inlets

Three-dimensional simulations are employed to examine the effect of inlet distortion and model fidelity with Reynolds averaged Navier-Stokes or large eddy simulation approaches for a generic circular cross-sectional supersonic combustor at a flight condition of Mach 6 and an altitude of about 24.2 km. To examine inlet distortion effects on combustion, frozen and finite rate chemistry simulations are performed on combustors connected to two different types of streamline-traced inlets (denoted and Jaws) with the Wilcox k-ω turbulence model. For comparison, uniform inflow boundary condition to the combustor is also simulated. The metrics employed include qualitative assessments related to flow structure as well as quantitative values offuel combustion efficiency and thrust ratios. The results indicate a complex overall effect of distortion due to inlet design. For Jaws, the increased pressure loss associated with distortion is mitigated slightly by improved combustion efficiency and better thrust performance. The Scoop inlet has lower distortion and better recovery, but the combustion coefficient is lower than Jaws. In the second part ofthis study, finite rate chemistry results with unsteady Reynolds averaged Navier-Stokes are compared with those from large eddy simulation with an uniform inflow profile. Differences in transient processes include the manner in which large- and small-scale structures originate and evolve in the cavity recirculation and downstream regions. The finer details observed with the large eddy simulation model have significant consequences on the overall field, including the unsteady position of the shock structure arising from the interaction of the incoming flow with the cavity shear layer, combustion processes, and injection jet interactions.

Comparison of Horizontally and Vertically Launched Airbreathing and Rocket Vehicles

A design study was performed to define and compare the parameters of horizontal- and vertical-takeoff reusable launch-vehicle systems to identify promising configurations for further developmental emphasis. The investigation considered both two-stage rockets and single-stage airbreathing ramjet/scramjet-powered vehicles, thus representing next-generation and third-generation configurations, respectively. The payload requirement for each vehicle was 20,000 Ib delivered to a 100-n mile circular Earth orbit launched easterly from Kennedy Space Center. All vehicles were first analyzed using liquid hydrogen for the entire trajectory and then reanalyzed with liquid hydrocarbon fuel for the first stage, if a rocket, or for the low-speed trajectory segment to ramjet start for the airbreathers. The vertical-takeoff airbreathing vehicles were found to have the lowest empty weights and gross takeoff weights of all of the vehicle configurations, with three-dimensional inward-turning inlets outperforming two-dimensional inlets, and the use of hydrocarbon fuel outperforming hydrogen fuel for the launch propulsive segment to ramjet start. The best horizontal takeoff vehicle is the all-hydrogen inward-turning airbreather. For the two-stage rockets, the lightest empty weight was achieved with the use of hydrocarbon fuel in the booster and hydrogen fuel in the orbiter.