Engineering topics

May-Fun Liou

Publications and source records attributed to May-Fun Liou.

5 records

NASA NTRSDate not supplied

Benefit and Critical Factors for the Performance of the Boundary Layer Ingesting Propulsion

The benefit of the boundary layer ingestion (BLI) is described in the perspective of the propulsion and engine development. A power saving map of the BLI engines is derived based on the correlation of the shape factor of the ingested boundary layer and the propulsive efficiency. The ratio of the mass flow rate between BLI and non-BLI propulsors is introduced to quantify the power saving of the BLI engine relative to a corresponding clean inlet flow engine that generates the same amount of net thrust. The wake recovery factor from the jet flow is applied to find the optimum sizing of the engine for the given design requirement. The effects of the fan pressure ratio of the propulsor toward the power saving are also investigated to seek out the feasible range of the BLI propulsor design. The derived correlation is validated with CFD analyses. Simulation models using variously sized engines relative to an influencing body are developed so that a numerical experiment is carried out with the various shape factors. The effect of the propulsion airframe integration toward the aerodynamic forces on the fuselage and nacelle is investigated via parametric study of the engine sizing and fan pressure ratio for the wake ingestion models. The propulsor efficiency is quantified toward the saving in the actual shaft power and correlated with the efficiency penalty of the BLI propulsor. The correlation is also validated via comparison of the turbo-machinery CFD results for BLI2DTF and conventional transonic fan stages.

Boundary Layer Ingestion↗

NASA NTRSDate not supplied

Prediction of Turbulent Diffusing Flows Using FUN3D

The FUN3D code was used to perform Reynolds-averaged Navier-Stokes (RANS) simulations to compute subsonic flow in an S-duct diffuser and transonic flow in a two-dimensional diffuser using the Speziale-Sarkar-Gatski/Launder-Rodi-Reece (SSG/LRR) Reynolds stress model (RSM). For comparison purposes, additional simulations were run with the one-equation Spalart-Allmaras (SA) and the two-equation Menter Shear-Stress Transport (SST) turbulence models. Each model was run with and without the quadratic constitutive relation (QCR) for computing the turbulent stresses. It was shown that the simulations that utilized the RSM had better overall predictions of the diffusive flow fields compared to the simulations that utilized the one and two equation turbulence models.

Inlet Distortion↗

NASA NTRSDate not supplied

Conceptual Design of Propulsors for the SUSAN Electrofan Transport Aircrafts

Conceptual designs of the propulsor modules for the SUSAN electro-fan aircraft are sought after. Shaft power requirement is reduced by using boundary layer ingesting propulsion technology. There are several obstacles to designing feasible BLI propulsion systems such as inlet distortion, flow blockage from ingesting low-momentum flow, strong coupling between airframe and propulsion systems. Thus, the high fidelity CFD tool is indispensable to assess the performance of the propulsion systems and evaluate the inlet profiles during the design process. Consequently, the CFD data is used to update the inputs for the NPSS model from the initial stage of the system design. Hence, the inlet sizing, fan design, and estimation of the power saving are carried out. Various installation concepts of the mail-slot nacelle, such as under-/over-wing and trailing edge configurations, are investigated for the wing-mounted turbo-electric distributed propulsor module, and their power-saving is evaluated. As for the tail-mounted turbofan engine, the fan diameter and inlet captured area is determined based on the CFD profiles. An appropriate area ratio of the bypass and core ducts is derived from meeting the target bypass ratio from the system design. The baseline fan stage is analyzed by full annulus URANS CFD to assess the efficiency penalty due to the ingested pressure and swirl distortions.

Electric Aircraft↗

NASA NTRSDate not supplied

Design and Analysis of A Jet Stretcher for High-Altitude Supersonic Free Jet Testing

A jet stretcher can be used to extend the region of clean flow for a test article in a supersonic free jet. The device acts to shield the article from shock waves reflected from the free jet shear layer. It can also allow for overexpanded nozzle operation through blocking shocks emanating from the nozzle lip, enlarging the potential test envelope. The FUN3D computational fluid dynamics solver was used to test a design process for developing jet stretchers. The inner surface of the axisymmetric jet stretcher was obtained from a streamline extracted from a free flight simulation around a notional test article at the intended test condition of Mach 3.2, 53,000 ft. The test article and jet stretcher were then simulated in a free jet nozzle exhaust, and the flowfield within a notional inlet aperture was compared between the installed and free flight calculations. Ambient pressure was increased until separation within the free jet nozzle finally induced disturbances at the inlet. The jet stretcher was shown to provide clean flow to the inlet at cell pressure ratios up to 2.8. A process for trimming the axisymmetric jet stretcher was also tested. This was intended to provide blockage relief for complex test articles, aiding with starting, as well as reducing weight and fabrication cost. The trimmed jet stretcher performed identically to the axisymmetric model at slightly-overexpanded conditions, but at cell pressure ratios above 1.3 allowed disturbances from the trailing edge to reach the inlet.

free jet↗

NASA NTRSDate not supplied

Design and Analysis of A Jet Stretcher for High-Altitude Supersonic Free Jet Testing

A jet stretcher can be used to extend the region of clean flow for a test article in a supersonic free jet. The device acts to shield the article from shock waves reflected from the free jet shear layer. It can also allow for overexpanded nozzle operation through blocking shocks emanating from the nozzle lip, enlarging the potential test envelope. The FUN3D computational fluid dynamics solver was used to test a design process for developing jet stretchers. The inner surface of the axisymmetric jet stretcher was obtained from a streamline extracted from a free flight simulation around a notional test article at the intended test condition of Mach 3.2, 53,000 ft. The test article and jet stretcher were then simulated in a free jet nozzle exhaust, and the flowfield within a notional inlet aperture was compared between the installed and free flight calculations. Ambient pressure was increased until separation within the free jet nozzle finally induced disturbances at the inlet. The jet stretcher was shown to provide clean flow to the inlet at cell pressure ratios up to 2.8. A process for trimming the axisymmetric jet stretcher was also tested. This was intended to provide blockage relief for complex test articles, aiding with starting, as well as reducing weight and fabrication cost. The trimmed jet stretcher performed identically to the axisymmetric model at slightly overexpanded conditions, but at cell pressure ratios above 1.3 allowed disturbances from the trailing edge to reach the inlet.

free jet↗