A Stream Function Relaxation Method for Solving Transonic S1 Stream Surface With Pre-Determination of the Density

On the basis of Prof. Wu’s 3-D flow theory (ref.1, 2, 3, 4, 5), a general streamfunction equation in non-orthogonal curvilinear coordinates is developed. The equation can be used to calculate subsonic or transonic flows on S1 or S2 stream surfaces of turbomachinery. In this paper streamlines coordinates and a mixed difference scheme are adopted in solving the stream function equation. A procedure for pre-determination of the density is developed and used to determine the unique-value of density from the known value of the stream function. Numerical examples are given.

General Curved Surface Fitting and Calculation of Flow Along Arbitrarily Twisted Stream Surface

This paper consists of two parts. (1) General curved surface fitting and grid refining. A method of fitting a set of given discrete points on several stream lines to give a smooth and arbitraily twisted stream surface was developed. Based upon the small deformation theory for thin plate, the Kirchhoff’s Equation was solved and twofold transformations were incorporated. The first step is the transformation from physical surface into computational surface and the second is affine transformation. The accuracy of the result is about 0.004% and the CPU time needed is reasonable for engineering application. Then the refined computational grid and the calculation for the geometrical quantities of the grid are carried out on the fitted surface. (2) Calculation of the flow along the fitted stream surface. Employing non-orthogonal curvilinear coordinate system, the fitted stream surface is selected as a coordinate surface, so that there are only two velocity components even when the stream surface is arbitrarily twisted, and it is very convenient to define the stream function. The general equation for the quasi-linear stream function governing the flow along the fitted stream surface was employed. This was solved with the method of direct decomposition of matrix. The numerical examples are also included in this paper. The present method can be used for S1 and S2 stream surfaces and other engineering calculations.

A General Program for the Prediction of the Transient Performance of Gas Turbines

The paper describes a general program which has been developed for the prediction of the transient performance of gas turbines. The program is based on the method of continuity of mass flow. It has been applied successfully to a wide range of aero gas turbines, ranging from single to three-spool and from simple jet to bypass types with or without mixed exhausts. The results for three of these engine types are illustrated. Computing times are reasonable, increasing with the complexity of the engine. A parallel paper describes the inclusion of thermal effects in the prediction program.

F-14 Re-Engining With the F110 Engine

The advantages of re-engining the F-14 aircraft with the F110 engine is presented. The areas of improvement and the engine development philosophy are explained. A summary description of the pertinent engine design features of the F110 are presented. The flight test results on inlet/engine compatability, afterburner operation, airplane performance, and maintainability/reliability/durability are interpreted. Finally, a description of the proposed version of the F110 engine for the F-14 is presented.

Improvement of Pump Performance at Off-Design Conditions

Industrial pumps are generally used in a wide range of operating conditions from almost zero mass flow to mass flows larger than the design value. It has been often noted that the head-mass flow characteristic, at constant speed, presents a negative bump as the mass flow is somewhat smaller than the design mass flows. Flow and mechanical instabilities appear, which are unsafe for the facility. An experimental study has been undertaken in order to analyze and if possible to palliate these difficulties. A detailed flow analyzis has shown strong three dimensional effects and flow separations. From this better knowledge of the flow field, a particular device was designed and a strong attenuation of the negative bump was obtained.

Status of the AGT 100 Advanced Gas Turbine Program

Recent activities on the AGT 100 Advanced Gas Turbine Program have included engine testing, aerodynamic component development, and ceramic material and component development. Engine testing has progressed in total hours and hours per build, without a major failure. A special mechanical loss test was conducted. Aerodynamic component activity has included the compressor, combustor and regenerator. Ceramic development was continued in areas of basic materials, processing, component fabrication and evaluation, and engine testing.

3-D Design of Turbine Airfoils

With modern turbines operating at a high level of efficiency, sophisticated design techniques are needed for further improvements. With the aid of computers 3-D aspect like end wall contouring and airfoil stacking can be integrated into the design process. The possibilities presented by the latter to control reaction, loading and secondary flow effects are analyzed and compared with experimental results. The implications for the resulting airfoil geometry are shown and limitations are discussed.

A Comparison Between Full and Simplified Navier-Stokes Equation Solutions for Rotating Blade Cascade Flow on S1 Stream Surface of Revolution

A method for solving the Navier-Stokes equations of the rotating blade cascade flow on S1 stream surface of revolution is developed in the present paper. In this paper a complete set of full and simplified Navier-Stokes equations is given which includes stream-function equation, energy equation and entropy equation, equation of state for a perfect gas, formula for estimating density and formulas for calculating viscous forces, work done by viscous force, dissipation function and heat-transfer term. A comparison between the full and the simplified Navier-Stokes equations is made. The viscous terms of both full and simplified Navier-Stokes equation solutions are also compared in the present paper. The comparison shows that the simplified Navier-Stokes equations are applicable.

Production and Development of Secondary Flows and Losses Within a Three Dimensional Turbine Stator Cascade

Using five-hole pitot tubes, detailed flow measurements were made before, within and after a low-speed three-dimensional turbine stator blade row to obtain quantitative information on the aerodynamic loss mechanism. Qualitative flow visualization tests and endwall static pressure measurements were also made. An analysis of the tests revealed that many vortical flows promote loss generation. Within a large part of the cascade, a major loss process could be explained simply as the migration of boundary layer low energy fluids from surrounding walls (endwalls and blade surfaces) to the blade suction surface near the trailing edge. On the other hand, complexity exists after the cascade and in the vortical flows near the trailing edge. The strong trailing shedding vortices affect upstream flow fields within the cascade. Detailed flow surveys within the cascade under the effects of blade tip leakage flows are also included.

Power Dense Gas Turbine APUs

Future high performance aircraft will require more compact, lighter weight, and self-sufficient secondary power equipment capable of faster starting and delivering high specific powers over wider operating envelopes of inlet temperatures and altitudes. Meeting these requirements may not be entirely compatible with improving thermal efficiency, particularly for the small air-breathing gas turbine since optimum cycle conditions differ for maximum specific power and specific fuel consumption. Further conflict lies in the necessity to provide faster start times with a limited capacity of stored on-board start energy, because compressor and turbine inertias must be minimized although compressor and turbine airflow-swallowing capacity must be maximized. This paper discusses the numerous design disciplines which constrain power density for small gas turbine auxiliary power units. Several potentially profitable development avenues are suggested for continuing the improvement of aircraft system performance.