Optimization of Gas Turbine Combustor Stoichiometry for Expanded Operating Regime

The superior performance of an advanced turbine engine propulsion system depends upon the stability, performance, and reliability of the engine combustion system which must satisfy a number of stringent design requirements. In order to meet these requirements using a single combustion device, it has been necessary in the past to make performance tradeoffs. Satisfactory design compromises have been reached; however, in many cases there remain unresolved deficiencies. Variable combustor geometry represents a new degree of freedom in turbine engine design which can be drawn upon to correct many of the common deficiencies of fixed geometry combustion systems. In this program variable combustor geometry is being applied to a high-temperature-rise combustor. There are several areas that need improvement in which variable geometry techniques can be profitably applied. These include anticipated deficiencies in altitude relight, smoke, ground start capability, and the need to reduce chemical emissions without compromising engine performance. It should be noted, however, that these potential improvements must be traded off against possible penalties in weight, cost, and control system complexity before a final system selection is made. The objective of the program is to conduct a combined analytical and experimental investigation for the purpose of identifying, evaluating, and demonstrating techniques involving the use of variable combustor geometry to achieve improved operating characteristics. The first phase concerns the analytical determination of the concepts meeting the stringent design criteria. The three concepts chosen show that two-position mechanism controlling front-end airflow will provide sufficient stoichiometry control.