Approaches to the Prevaporized-Premixed Combustor Concept for Gas Turbines

Abstract

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 stringer: 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 0.010-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.

Conversion of Liquid to Gaseous Fuels for Lean Premixed Combustion

“…The feasibility of vaporizing fuel oil No. 2 in a heat exchanger which is external to the engine was investigated (Spadaccini and Szetela, 1975). Tests indicated that a black, hard, brittle deposit which gradually increased in thickness as the fuel progressed along the tube was formed on the vaporizer wall during operation.…”

A Study of External Fuel Vaporization

“…Because sulfur was found on the walls of the tubes used in fuel vaporization experiments (Ref. 16), sulfur corrosion must be considered to be a potential problem. Early tests in that program appeared to show slight indications of intergranular attack in type 304 stainless steel tubes.…”

Coke Removal in Fuel-Cooled Thermal Management Systems

“…In previous work, UTRC has also shown that different elements (e.g., carbon and sulfur) are burned off at different temperatures and that further development of the regeneration process is required. 5 It is important to note that there have been many books, papers, and patents on coke deposition research as well as coke removal and surface regeneration from catalyst surfaces. [6][7][8][9][10][11] The objective of this study is to investigate and assess the practicality of various in situ surface regeneration techniques for realistic passage sizes and to develop a safe, simple, and cost-effective in situ surface regeneration technique for hydrocarbon fuel-cooled thermal management systems.…”

“…United Technologies Research Center (UTRC) has performed catalyst regeneration by carbon burnoff with the reactor installed in the test apparatus (simulating in situ maintenance) and without affecting the surface structure or chemical composition. In previous work, UTRC has also shown that different elements (e.g., carbon and sulfur) are burned off at different temperatures and that further development of the regeneration process is required . It is important to note that there have been many books, papers, and patents on coke deposition research as well as coke removal and surface regeneration from catalyst surfaces. − …”