Experience With the TF40B Engine in the LCAC Fleet

Four Textron Lycoming TF40B marine gas turbine engines are used to power the U.S. Navy’s Landing Craft Air Cushion (LCAC) vehicle. This is the first hovercraft of this configuration to be put in service for the Navy as a landing craft. The TF40B has experienced compressor blade pitting, carbon erosion of the first turbine blade and hot corrosion of the hot section. Many of these problems were reduced by changing the maintenance and operation of the LCAC. A Component Improvement Program (CIP) is currently investigating compressor and hot section coatings better suited for operation in a harsh marine environment. This program will also improve the performance of some engine components such as the bleed manifold and bearing seals.

Fault Signatures Obtained From Fault Implant Tests on an F404 Engine

The fault diagnostic process for gas turbine engines can be improved if data acquired by an on-board engine monitoring system (EMS) are utilised effectively. In the commercial transport field, techniques are available to extract engine condition assessment information from steady-state EMS data. In a military environment, steady-state data are not always available, and therefore it is desirable to extract at least some of the information from transient data, such as during take-off. Fault signatures are presented for an F404 engine based on fault implant tests in a sea-level-static (SLS) test-cell. A comparison is then made between the fault coverage capabilities of fault diagnostic techniques based on the use of steady-state engine data with those using transient data. The important conclusions to emerge from this work are that for the range of faults examined, not only is there similar fault information contained within the transient data but the faults can be detected with increased sensitivity using these data.

LV100 AIPS Technology—For Future Army Propulsion

The overall design of and Advanced Integrated Propulsion System (AIPS), powered by an LV100 gas turbine engine, is presented along with major test accomplishments. AIPS was a demonstrator program that included design, fabrication, and test of an advanced rear drive powerpack for application in a future heavy armored vehicle (54.4 tonnes gross weight). The AIPS design achieved significant improvements in volume, performance, fuel consumption, reliability/durability, weight and signature reduction. Major components of AIPS included the recuperated LV100 turbine engine, a hydrokinetic transmission, final drives, self-cleaning air filtration (SCAF), cooling system, signature reduction systems, electrical and hydraulic components, and control systems with diagnostics/prognostics and maintainability features.

Optimization Aspects of an Ejector Type Hypersonic Thrust Nozzle

Hypersonic aircraft projects are highly dependant on efficient propulsion systems. High performance and integration within the airframe play a vital role in the overall concept. Particular attention must be paid to the exhaust system that is submitted to a wide range of operational requirements. An optimization of the nozzle geometry for high flight Mach numbers will lead to a low performance at the transonic flight regime. The additional use of secondary ejector air flow at transonic speeds is one option to improve the thrust behaviour of the nozzle. In the presented paper performance data of single expansion ramp ejector type nozzles are predicted using a calculation model based on a method-of-characteristics algorithm. For optimization purposes the effects of various design parameters on axial thrust coefficient and thrust vector angle are discussed. The geometric parameters investigated are the length of the lower nozzle wall and its deflection angle as well as the ejector slot location and its cross-section.

A Model and State-Space Controllers for an Intercooled, Regenerated (ICR) Gas Turbine Engine

A two-and-one-half spool gas turbine engine was modeled using the Advanced Computer Simulation Language (ACSL), a high level simulation environment based on FORTRAN. A possible future high efficiency engine for powering naval ships is an intercooled, regenerated (ICR) gas turbine engine and these features were incorporated into the model. Utilizing sophisticated instructions available in ACSL linear state-space models for this engine were obtained. A high level engineering computational language, MATLAB, was employed to exercise these models to obtain optimal feedback controllers characterized by the following methods: (1) state feedback; (2) linear quadratic regulator (LQR) theory; and (3) polygonal search. The methods were compared by examining the transient curves for a fixed off-load, and on-load profile.

Navier-Stokes Computation on a Pivoting Doors Thrust Reverser and Comparison With Tests

An engine thrust reverser must meet different aerodynamic requirements to take into account the engine and airplane integration. These requirements are: - Control of the exit area in order to assess a convenient engine compatibility during the reverser operation. - Generation of reverse thrust meeting the level specified by the airframe in order to slowdown the airplane. - Mimization of the reversed flow field interaction with the airplane structure such as wing and shutters. - Avoid the flow reingestion by the engine fan. In order to reduce the tests number, to decrease the development delay and to improve aerodynamic performance, SNECMA group (SNECMA and HISPANO-SUIZA) has decided to develop a CFD method adapted to pivoting doors thrust reverser aerodynamic calculation. This method uses a Navier-Stokes 3D solver (PHOENICS code) well adapted to complex geometry and complex flow field. The mesh is generated with an analytical method and only one domain is used. The computation has been completed assuming laminar viscosity. The numerical data got with this method have been compared to static test realized on a model similar to actual CFM56-5C four doors reverser. The comparison parameters are the static pressure on the doors, the flow rate and the axial reverse thrust.

Development of a Gas Turbine Generator On-Board Electric Power Source for MAGLEV Trains

We have been jointly developing an on-board electric power source for MAGLEV trains by applying a 30kW generator for gas turbine hybrid passenger cars. Operating the generator on a test model apparatus simulating the generator installed in a MAGLEV train, we investigated its electrical and mechanical characteristics with the location close to superconducting coils. The effects of magnetic field on the generator’s characteristics are investigated and described in this paper. MAGLEV trains require about a 50kW on-board power supply per car. At present, we are designing a 50kW gas turbine generator on the basis of the 30kW gas turbine generator.

Influence of a Thermal Barrier Coating on the Performance of a Turboprop Engine

Under the sponsorship of the Canadian Department of National Defence, the Engine Laboratory of the National Research Council of Canada has evaluated the influence of applying a thermal barrier coating on the performance of a gas turbine engine. The effort is aimed at quantifying the performance effects of a particular ceramic coating on the first stage turbine vanes. The long term objective of the program is to both assess the relative change in engine performance and compare against the claimed benefits of higher possible turbine inlet temperatures, longer time in service and increased time between overhauls. The engine used for this evaluation was the Allison T56 turboprop with the first stage turbine nozzles coated with the Chromalloy RT-33 ceramic coating. The issues addressed in testing this particular type of hot section coating were; 1) effect of coating thickness on nozzle effective flow area; 2) surface roughness influence on turbine efficiency; This paper describes the project objectives, the experimental installation, and the results of the performance evaluations. Discussed are performance variations due to coating thickness and surface roughness on engine performance characteristics. As the performance changes were small, a rigorous measurement uncertainty analysis is included. The coating application process, and the affected overhaul procedures are examined. The results of the pre- and post-coating turbine testing are presented, with a discussion of the impact on engine performance.

Hypersonic Flow Separation in Shock Wave Boundary Layer Interactions

This work presents an assessment of the experimental data on separated flow in shock wave turbulent boundary layer interactions at hypersonic and supersonic speeds. The data base consist of selected configurations where the only characteristic length in the interation is the incoming boundary layer thickness. It consists of two dimensional and axisymmetric interactions in compression corners or cylinder-flares, and externally generated oblique shock interactions with boundary layers over flat plates or cylindrical surfaces. The conditions leading to flow separation and the empirical correlations for incipient separation are reviewed. The effects of Mach number, Reynolds number, surface cooling and the methods of detecting separation are discussed.

The Effect of Compressor Rotor Tip Crops on Turboshaft Engine Performance

The results from an experimental study into the effect of compressor rotor tip clearance changes on the steady-state performance and stability margins of a free-power turbine turboshaft engine are presented and discussed. This work was directed at the development of methods to diagnose engine condition from gas path measurements. It was found that the normal production suite of engine instrumentation was able to measure the deterioration in engine performance due to the implanted compressor degradation and the resultant deviations in the measured parameters from their respective nominal baselines do provide useful indicators of engine condition.