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.

Fuel Cell Powered Electric Propulsion for HALE Aircraft

Electrical energy sources offer some interesting possibilies for aircraft propulsion. Of particular interest are electric propulsion systems developed for aircraft that are designed for high altitude, long endurance (HALE) missions. This class of aircraft would greatly benefit from an aircraft propulsion system which minimizes thermal energy rejection and environmental pollutants. Electric propulsion systems may prove viable for the HALE mission, if reliable energy sources can be developed that are both fuel and weight efficient. Fuel cells are a possible energy source. This paper discusses the thermodynamic cyclic analysis of a fuel cell powered electric propulsion system. In particular, phosphoric acid and polymer electrolyte fuel cells are evaluated as possible energy sources.

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.

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.

Aircraft Engine Integration for the M88-RAFALE Couple

As all other comparable programs, the couple RAFALE-M88 has to be a fully optimized multirole weapon system with the highest level of integration; a key factor for that purpose is the very good prebuilt integration of the engine within the aircraft. After a short description of the main historical milestones of the aircraft and engine programs development and integration, the paper will first summarize the rigourous procedures which are used by aircraft and engine manufacturers, official services and future Air Force and Navy users. Then, the paper will detail the main points where aircraft engine integration as to be lead precisely and carefully; these points are: -at first, the electronical links which are establised between the aircraft and the engine, due to the high complexity of flight softwares who have to work and talk with each others; -secondly, the aerodynamical subjects, including air intake and exhaust nozzle installation; -thirdly, the mechanical integration (geometry, mechanical behaviour, …); -then all kinds of fluid circuits or equiments.

Thrust Vectoring/Reversing Tactics in Air-to-Air Combat

Considerable effort is now underway to develop technologies for enhancing fighter maneuvering limits. This has in part been motivated by the capabilities of advanced air-to-air missiles. One approach to enhanced combat effectiveness involves flight envelope expansion and improved controllability via engine thrust-vectoring and thrust-reversing. The complexity of fighter combat, however, makes it difficult to perform engineering analyses for assessing potential technological enhancements and risks. This paper describes a digital simulation that has been used to identify benefits associated with improved maneuverability. The Navy/Grumman F-14 aircraft provides the flight characteristics database. Combat tactics are developed as part of the solution process and are based solely on characteristics of the combatants and weapons employed. Head-on and co-directional neutral start combat engagements are used to illustrate study results.

A Compact, Intercooled and Regenerated Gas Turbine for HALE Applications

A mechanically coupled, two spool, intercooled and regenerated gas turbine engine designed for a high altitude, long endurance (HALE) mission is described. The design philosophy was based on minimization of total energy expended using a two stage optimization process utilizing a multivariate regression and optimization technique. This optimization process addressed the impact of the propulsion system as installed on an air vehicle, including all installation effects. Weight and drag of the complete nacelle as they were affected by the characteristics of the engine was included. A brake specific fuel consumption (BSFC) of 0.262 lb/hr/hp (0.159 kg/hr/kw) and mission average specific fuel consumption (MSFC) of 0.266 lb/hp-hr (0.160 kg/kW-hr) was estimated for the bare engine and an MSFC of 0.327 lb/hp-hr (0.199 kg/kW-hr) was estimated for the fully installed engine, including the nacelle drag penalty, where MSFC is defined as the total fuel required to complete the mission divided by the total energy expended during the mission. A comparison with other gas turbine and reciprocating engines currently considered as candidates for HALE applications is also presented.

Expert Systems for the Simulation of Gas Turbine Engines

The paper deals with the possibility to develop effective Expert Systems for the simulation, the monitoring and the diagnostics of engines. The work concerns with the development of suitable Knowledge Bases and Expert Systems for different activities. The approach to the problem deals with Expert Systems for engine simulation. These Systems give the operating limits of the engine and the required control laws for reaching assigned values of performance. Other Expert Systems have been developed for fault simulation. The matrices of influence have proved to be suitable for constructing effective Knowledge Bases. Finally Expert Systems for engine diagnostics have been set-up. The paper shows in full detail the methods, the techniques and several applications of the developed codes.