Discretized Miller approach to assess effects on boundary layer ingestion induced distortion

The performance of propulsion configurations with boundary layer ingestion (BLI) is affected to a large extent by the level of distortion in the inlet flow field. Through flow methods and parallel compressor have been used in the past to calculate the effects of this aerodynamic integration issue on the fan performance; however high-fidelity through flow methods are computationally expensive, which limits their use at preliminary design stage. On the other hand, parallel compressor has been developed to assess only circumferential distortion. This paper introduces a discretized semi-empirical performance method, which uses empirical correlations for blade and performance calculations. This tool discretizes the inlet region in radial and circumferential directions enabling the assessment of deterioration in fan performance caused by the combined effect of both distortion patterns. This paper initially studies the accuracy and suitability of the semi-empirical discretized method by comparing its predictions with CFD and experimental data for a baseline case working under distorted and undistorted conditions. Then a test case is examined, which corresponds to the propulsor fan of a distributed propulsion system with BLI. The results obtained from the validation study show a good agreement with the experimental and CFD results under design point conditions

Numerical investigation of highly curved turbulent flows in centrifugal compressors and in a simplified geometry

Curvature effects are investigated in terms of a recently developed curvature corrected turbulence model in turbomachinery applications. Two centrifugal compressor stages and a curved geometry modelled after a centrifugal impeller are simulated using the curvature corrected SST (SST-CC) turbulence model. This work improves the understanding of how the SST-CC model predicts curvature effects. An analysis of the SST-CC production multiplier in both centrifugal cases reveals that the model is appropriately accounting for curvature effects, showing increased production near concave surfaces and decreased production near convex surfaces. This correlates well with the simplified geometry results and demonstrates that the simplified geometry is successfully capturing the curvature effects of the centrifugal stages. A detailed investigation of turbulence quantities in the simplified geometry further demonstrated how curvature effects are predicted by the SST-CC model. Future work will include experimentation on the 1C stage and further comparison with numerical results

STOVL aircraft simulation for integrated flight and propulsion control research

The United States is in the initial stages of committing to a national program to develop a supersonic short takeoff and vertical landing (STOVL) aircraft. The goal of the propulsion community in this effort is to have the enabling propulsion technologies for this type aircraft in place to permit a low risk decision regarding the initiation of a research STOVL supersonic attack/fighter aircraft in the late mid-90's. This technology will effectively integrate, enhance, and extend the supersonic cruise, STOVL and fighter/attack programs to enable U.S. industry to develop a revolutionary supersonic short takeoff and vertical landing fighter/attack aircraft in the post-ATF period. A joint NASA Lewis and NASA Ames research program, with the objective of developing and validating technology for integrated-flight propulsion control design methodologies for short takeoff and vertical landing (STOVL) aircraft, was planned and is underway. This program, the NASA Supersonic STOVL Integrated Flight-Propulsion Controls Program, is a major element of the overall NASA-Lewis Supersonic STOVL Propulsion Technology Program. It uses an integrated approach to develop an integrated program to achieve integrated flight-propulsion control technology. Essential elements of the integrated controls research program are realtime simulations of the integrated aircraft and propulsion systems which will be used in integrated control concept development and evaluations. This paper describes pertinent parts of the research program leading up to the related realtime simulation development and remarks on the simulation structure to accommodate propulsion system hardware drop-in for real system evaluation

Seal inlet disturbance boundary conditions for rotordynamic models and influence of some off-design conditions on labyrinth rotordynamic instability

Systematic parametric studies were performed to better understand seal-inlet rotordynamics. A CFD-perturbation model was employed to compute the seal-inlet flow disturbance quantities. Seal inlet disturbance boundary condition correlations were proposed from the computed seal-inlet quantities using the important parameters. It was found that the cosine component of the seal-inlet swirl velocity disturbance W1C has a substantial impact on the cross-coupled stiffness, and that the correlations for W1C and W1S should be used to replace the historical guess that seal inlet W1C = 0 and W1S = 0. Also, an extremely precise relationship was found between the swirl disturbance W1C and the seal-inlet swirl velocity (ÃÂRsh â ïW0). Thus, the number of experiments or computer runs needed to determine the effect of spin speed, shaft radius and/or inlet swirl velocity on the cross-coupled stiffness is greatly reduced by plotting the simplified relationship of the cross-coupled stiffness against the swirl slip velocity. The benefits of using the new seal-inlet boundary condition correlations were assessed by implementing them into a CFD-perturbation model. Consistently improved agreement with measurements was obtained for both liquid annular seals and gas labyrinth seals. Further, the well-established CFD-perturbation model with new boundary condition correlations was employed to investigate the rotordynamics of two off-design situations. The first case considered the influence of labyrinth seal teeth damage on the performance and the rotordynamic characteristics of impeller eye seals in centrifugal compressors. The second case considered the influence of rotor-axial-shifting on rotordynamic forces for high-low labyrinth seals in steam turbines during the start-up and shut-down process. The results should provide useful information for labyrinth seal design and fault diagnosis of stability problems in turbines and compressors

Contrasts between classes of assets in fixed investment panel equations as a way of testing real option theory

This paper reports estimation of investment equations for two classes of fixed assets: plant & machinery and building for a large sample of UK manufacturing industries. It exploits the different degree of irreversibility that characterises these assets to test the power of real options theory to explain investment under uncertainty. Additionally, the paper uses a specially constructed industry-specific measure of irreversibility for plant and machinery investment to test for real options effects within that class of investment.Investment, Industry, Irreversibility, Real Options, Uncertainty

Coating for prevention of titanium combustion

A limited number of coating options for titanium gas turbine engine components were explored with the objective of minimizing potential combustion initiation and propagation without adversely affecting component mechanical properties. Objectives were met by two of the coatings, ion-plated platinum plus electroplated copper plus electroplated nickel and ion vapor deposited aluminum

Screening of energy efficient technologies for industrial buildings' retrofit

This chapter discusses screening of energy efficient technologies for industrial buildings' retrofit

CFD Primer: What Do All Those Colors Really Mean?

TutorialThis tutorial provides a general overview of computational fluid dynamics (CFD). It is not intended for CFD experts but rather for those seeking answers to questions such as: What is the role of CFD in the design / analysis process? What is CFD? What benefits can be derived from CFD? What are the typical deliverables from CFD? In addition to answering the above questions, the session will also offer several sample cases illustrating some practical applications of CFD in day-to-day design, analysis and trouble-shooting processes

Energy Efficient Engine Program: Technology Benefit/Cost Study, Volume II

The Benefit/Cost Study portion of the NASA-sponsored Energy Efficient Engine Component Development and Integration program was successful in achieving its objectives: identification of air transport propulsion system technology requirements for the years 2000 and 2010, and formulation of programs for developing these technologies. It is projected that the advanced technologies identified, when developed to a state of readiness, will provide future commercial and military turbofan engines with significant savings in fuel consumption and related operating costs. These benefits are significant and far from exhausted. The potential savings translate into billions of dollars in annual savings for the airlines. Analyses indicate that a significant portion of the overall savings is attributed to aerodynamic and structure advancements. Another important consideration in acquiring these benefits is developing a viable reference technology base that will permit engines to operate at substantially higher overall pressure ratios and bypass ratios. Results have pointed the direction for future research and a comprehensive program plan for achieving this was formulated. The next major step is initiating the program effort that will convert the advanced technologies into the expected benefits

Numerical Simulation of Air Flow in Aeroengine Compressors

The performance of an aeroengine is influenced by the performance of the compressor system. A typical compressor consists of multistage axial compressors followed by a centrifugal stage. Here, a high-speed centrifugal and an axial stage are investigated in terms of turbulence modelling, flow blockage and rotor-stator (R-S) gap using the commercial software ANSYS CFX. The curvature corrected Shear stress transport (SST-CC) model of Smirnov and Menter is investigated for the first time in a high-speed centrifugal stage in terms of curvature and rotation effects. The SST-CC predictions are compared with the standard SST, Speziale, Sarkar, and Gatski Reynolds stress model (RSM-SSG) and the experimental data in terms of the global performance as well as the velocity profiles at the impeller-diffuser interface. The comparisons show that SST-CC has the best agreement with the experiments at choke condition while SST has better performance at the stall condition. The production term shows the expected sensitivity to the convex and concave curvatures. A new method to quantify blockage for both axial and centrifugal compressors is developed. Both steady and unsteady simulations are used to examine the flow blockage in the axial transonic stage. The variation of the rotor tip blockage with respect to the blade loading shows good agreement with previous studies. The total planar blockage indicates that stall might initiate at the stator trailing edge. The differences between the steady and unsteady predictions are mainly attributed to the local differences in the total pressure profiles at the inlet guide vanes–rotor interface. It was previously argued that reducing the R-S gap improves the efficiency of axial compressors due to reduced viscous mixing of the rotor wake. However, the current simulations show that the smallest R-S gap has the highest levels of total pressure losses within the stator passage and the highest levels of unsteady stator forces at reduced mass flow rates. The unsteadiness in the stator flow field is attributed to the larger stator suction surface boundary layer separation associated with the smallest gap. The smallest R-S gap reduces the viscous mixing of the wake at the expense of the efficiency