Application of an expert system shell in the preliminary design of offshore supply vessels

This paper presents the application of expert system programming in preliminary ship design with particular emphasis on offshore supply vessels. Instead of using one of the conventional programming expert system languages, the system is developed using an expert system shell, Leonardo. The design program is written in such a way that it is user friendly as well as giving the user full control over the progress of the design. The algorithms developed in this system are based on extensive research on existing offshore supply vessels

Large-Scale Advanced Prop-Fan (LAP) pitch change actuator and control design report

In recent years, considerable attention has been directed toward improving aircraft fuel consumption. Studies have shown that the high inherent efficiency previously demonstrated by low speed turboprop propulsion systems may now be extended to today's higher speed aircraft if advanced high-speed propeller blades having thin airfoils and aerodynamic sweep are utilized. Hamilton Standard has designed a 9-foot diameter single-rotation Large-Scale Advanced Prop-Fan (LAP) which will be tested on a static test stand, in a high speed wind tunnel and on a research aircraft. The major objective of this testing is to establish the structural integrity of large-scale Prop-Fans of advanced construction in addition to the evaluation of aerodynamic performance and aeroacoustic design. This report describes the operation, design features and actual hardware of the (LAP) Prop-Fan pitch control system. The pitch control system which controls blade angle and propeller speed consists of two separate assemblies. The first is the control unit which provides the hydraulic supply, speed governing and feather function for the system. The second unit is the hydro-mechanical pitch change actuator which directly changes blade angle (pitch) as scheduled by the control

Investigation of advanced counterrotation blade configuration concepts for high speed turboprop systems, task 1: Ducted propfan analysis

The time-dependent three-dimensional Euler equations of gas dynamics were solved numerically to study the steady compressible transonic flow about ducted propfan propulsion systems. Aerodynamic calculations were based on a four-stage Runge-Kutta time-marching finite volume solution technique with added numerical dissipation. An implicit residual smoothing operator was used to aid convergence. Two calculation grids were employed in this study. The first grid utilized an H-type mesh network with a branch cut opening to represent the axisymmetric cowl. The second grid utilized a multiple-block mesh system with a C-type grid about the cowl. The individual blocks were numerically coupled in the Euler solver. Grid systems were generated by a combined algebraic/elliptic algortihm developed specifically for ducted propfans. Numerical calculations were initially performed for unducted propfans to verify the accuracy of the three-dimensional Euler formulation. The Euler analyses were then applied for the calculation of ducted propfan flows, and predicted results were compared with experimental data for two cases. The three-dimensional Euler analyses displayed exceptional accuracy, although certain parameters were observed to be very sensitive to geometric deflections. Both solution schemes were found to be very robust and demonstrated nearly equal efficiency and accuracy, although it was observed that the multi-block C-grid formulation provided somewhat better resolution of the cowl leading edge region

A numerical simulation of the inviscid flow through a counter-rotating propeller

The results of a numerical simulation of the time-averaged inviscid flow field through the blade rows of a multiblade row turboprop configuration are presented. The governing equations are outlined along with a discussion of the solution procedure and coding strategy. Numerical results obtained from a simulation of the flow field through a modern high-speed turboprop will be shown

The design of a rotor blade test facility

The Mechanical and Aerospace Engineering Department has developed a need for test facilities related to rotorcraft, specifically facilities capable of testing scaled rotorcraft models and experimental propellers and rotors. A design was completed to fill these needs.;The design included several factors; aerodynamic conditions during operation, flexibility of application, ease and cost of construction, and safety. The aerodynamic conditions involved in the testing of rotors or propellers in static conditions were investigated. Other testing involving downwash impingement on wings was considered and incorporated into the design.;In addition, the design of the power transmission components was completed. This included the power requirements for testing, drivetrain components, and selection of electric motor and controller for use. Finite element analysis of the facility\u27s frame in static loading conditions was completed in Pro/Mechanica to determine response to operational loads

Generalized Advanced Propeller Analysis System (GAPAS). Volume 2: Computer program user manual

The Generalized Advanced Propeller Analysis System (GAPAS) computer code is described. GAPAS was developed to analyze advanced technology multi-bladed propellers which operate on aircraft with speeds up to Mach 0.8 and altitudes up to 40,000 feet. GAPAS includes technology for analyzing aerodynamic, structural, and acoustic performance of propellers. The computer code was developed for the CDC 7600 computer and is currently available for industrial use on the NASA Langley computer. A description of all the analytical models incorporated in GAPAS is included. Sample calculations are also described as well as users requirements for modifying the analysis system. Computer system core requirements and running times are also discussed

Design and engineering methods for open-rotor nacelle shaping

Due to the growing transport needs in emerging economies and recent success of the low-cost airlines, the demand for short/medium-haul aeroplanes is increasing. Within the next twenty years, the existing single-aisle aircraft are likely to be replaced by new models mounting new propulsion systems. One promising con- figuration being considered is the open-rotor, which is a revision of the propfan. However, further progress has to be done in order to transform propfan engines, whose technology dates back to the 1980s, into viable and feasible open-rotor con- cepts. Among the aspects yet to be investigated in su ficient depth is the de finition of a methodology for the open-rotor nacelle design. The aim of the present research is to help enhance the knowledge in this area. Even if there are a number of important fields of investigation for open-rotor designs, this work is limited to the analysis of the pusher architecture with no exhaust impingement through rotors. The research is initially performed combining both a graphical and a compu- tational approach, investigating the mathematical and physical aspects involved in the de finition of appropriate nacelle pro files, boundary conditions for the CFD analysis and simplifi ed rotor modelling. The first simulations are mainly focused on a typical propfan nacelle, which is taken as a reference model: the computations provide useful results for evaluating its aerodynamic features ... [cont.]

Computation of the tip vortex flowfield for advanced aircraft propellers

The tip vortex flowfield plays a significant role in the performance of advanced aircraft propellers. The flowfield in the tip region is complex, three-dimensional and viscous with large secondary velocities. An analysis is presented using an approximate set of equations which contains the physics required by the tip vortex flowfield, but which does not require the resources of the full Navier-Stokes equations. A computer code was developed to predict the tip vortex flowfield of advanced aircraft propellers. A grid generation package was developed to allow specification of a variety of advanced aircraft propeller shapes. Calculations of the tip vortex generation on an SR3 type blade at high Reynolds numbers were made using this code and a parametric study was performed to show the effect of tip thickness on tip vortex intensity. In addition, calculations of the tip vortex generation on a NACA 0012 type blade were made, including the flowfield downstream of the blade trailing edge. Comparison of flowfield calculations with experimental data from an F4 blade was made. A user's manual was also prepared for the computer code (NASA CR-182178)

The Design of Pumpjets for Hydrodynamic Propulsion

A procedure for use in the design of a wake adapted pumpjet mounted on the aft end of a body of revolution is presented. To this end, a pumpjet is designed for the Akron airship. The propulsor mass flow is selected to minimize kinetic energy losses through the duct and in the discharge jet. The shaft speed and disk size are selected to satisfy specified limits of cavitation performance and to provide acceptable blade loading. The streamtubes which pass through a propulsor mounted on a tapered afterbody follow essentially conical surfaces. A method is provided for defining these surfaces as a function of shroud geometry, rotor head distribution, and the energy distribution of the ingested mass flow. The three-dimensional effects to which the conical flow subjects the cylindrical blade design sections are described and a technique is presented which permits incorporation of these effects in the blade design procedure

Design of pumpjet propulsors using RANS-based multi-objective optimization

The design of linear pumpjets is addressed through a simulation-based design optimization approach based on RANS analyses in the case of rotor/stator (i.e., post swirl) configurations, characterized by 5 rotor blades and 5 or 10 stator blades. The optimal geometries from a multi-objective optimization process aimed at maximizing the propulsive efficiency at the lowest possible cavitation inception index are compared to a reference ducted propeller with decelerating nozzle, which served as baseline during the activity. A significant increase of propulsive efficiency with a reduced risk of cavitation is observed. Fully unsteady cavitating analyses are used to assess the reliability of the design activity, which is necessary build upon some simplifying assumptions (i.e., rotor/stator coupling through a mixing plane) needed for an affordable numerical process. Detached Eddy Simulations (IDDES) are finally carried out to highlight, in addition to the performance improvements provided by the pumpjets, also the influence of the rotor/stator/nozzle interaction on the vortical structures shed by the propulsors