Approaches to the Prevaporized-Premixed Combustor Concept for Gas Turbines

An experimental investigation was performed to evaluate a combustor concept which is applicable to gas turbine engines and is believed to offer valuable pollution control advantages relative to the conventional liquid-fuel-spray approach. It involves fuel prevaporization, premixing and lean combustion and may be applied to the design of combustors for aircraft, industrial or automotive powerplants. Two types of bluff-body flameholders, viz. porous-plate and drilled-plate, were evaluated for use as flame stabilizers within the combustor. Tests were conducted under sets of steady-state operational conditions corresponding, respectively, to applications in a low-pressure regenerative-cycle and high-pressure nonregenerative-cycle automobile gas turbine engines. The data acquired can be used to design gas turbine combustors having predicted performance characteristics which are better than those required to meet the most stringent automobile emissions regulations of the Federal “Clean Air Act.” Fuel prevaporization can be accomplished either externally, prior to admission into the engine airstream, or internally by the airstream itself. In support of the prevaporization concept, the feasibility of vaporizing No 2 fuel oil in a heat exchanger which is external to the engine was investigated. Tests conducted at representative operating conditions indicated that a deposit of 0.01 0-in. thickness was collected on the vaporizer wall after 50 hr of operation. A much shorter period of cleaning with hot air was sufficient to remove the deposit.