NOVELTY - A hydrogen-generating apparatus comprises a thermal combustor including a combustion zone, a cooling zone, and an enriching zone; a catalytic combustor; and a catalytic reformer. The thermal combustor produces an enriched exhaust stream that is fed to the catalytic combustor. The catalytic combustor produces second exhaust stream that is fed into the catalytic reformer.    USE - For producing hydrogen from hydrocarbon fuels.    ADVANTAGE - The inventive apparatus can handle transient operational demands while suppressing or eliminating carbon formation, allowing the apparatus to operate at levels between pure steam reformer and pure autothermal reformer modes. It provides rapid cold start/operation modes and a normal operation mode.    DETAILED DESCRIPTION - A hydrogen-generating apparatus comprises a thermal combustor (2) including a combustion zone, a cooling zone, and an enriching zone; a catalytic combustor (3); and a catalytic reformer. The combustion zone has a first fuel inlet and a first gas inlet for introducing a ratio of first hydrocarbon fuel and first oxygen-containing gas, and an ignition source for inducing combustion of first hydrocarbon fuel and first oxygen-containing gas to produce an exhaust stream that flows from the combustion zone into the cooling zone. The ratio is controllable to provide combustion of first hydrocarbon fuel within the combustion zone. The cooling zone has inlet(s), e.g. a first water inlet and/or a second gas inlet through which fluid(s) is injected into the exhaust stream to produce a cooled exhaust stream that is fed into the enriching zone. The enriching zone has a second fuel inlet for introducing a second hydrocarbon fuel into the cooled exhaust stream to produce an enriched exhaust stream that is fed into the catalytic combustor. The catalytic combustor has a first catalytic substrate on which a first catalyst is supplied. The first catalyst is selected to combust a portion of enriched exhaust stream and to produce a second exhaust stream that is fed into the catalytic reformer. The catalytic reformer includes an inlet for receiving a gaseous feed mixture of third hydrocarbon fuel, second oxygen-containing gas, and steam into an enclosed catalytic region that is heated by the second exhaust stream and provides a second catalytic substrate on which a second catalyst selected to reform the feed mixture to produce a hydrogen-containing reformate stream is supplied; an outlet for removing the reformate stream from the catalytic region; and an exhaust outlet for removing the second exhaust stream from the catalytic reformer. An INDEPENDENT CLAIM is also included for a multimode method of operating a fuel processor comprising a first operational mode that includes mixing first hydrocarbon fuel and first oxygen-containing gas to form a lean combustion mixture, feeding the lean combustion mixture into a thermal combustor, igniting the lean combustion mixture to produce an exhaust stream, mixing the exhaust stream with fluid(s), e.g. water or air to produce a cooled exhaust stream, mixing the cooled exhaust stream with a second hydrocarbon fuel without inducing auto-ignition to produce an enriched exhaust stream, feeding the enriched exhaust stream into a catalytic reactor, reacting a portion of the enriched exhaust stream in the catalytic combustor to produce a hydrogen (H2)-enriched exhaust stream, feeding the H2-enriched exhaust stream into a quasi-autothermal reactor (5) to heat reformer tubes, and removing the H2-enriched exhaust stream from the quasi-autothermal reactor; and a second operational mode that includes feeding a fuel cell exhaust stream into the catalytic combustor, reacting a portion of the fuel cell exhaust stream to produce a second exhaust stream, feeding the second exhaust stream into the quasi-autothermal reactor to heat reformer tubes, removing the second exhaust stream from the quasi-autothermal reactor, forming a process gas mixture of air, third hydrocarbon fuel and steam in air-fuel-stream mixer, feeding the process gas mixture into the reformer tubes, reacting the process gas mixture to produce a H2-enriched reformate, and removing the H2-enriched reformate from the reformer tubes and the quasi-autothermal reactor.    DESCRIPTION OF DRAWING(S) - The figure is a cross-sectional view of hydrogen-generating apparatus.    Fuel processor (1)    Thermal combustor (2)    Catalytic combustor (3)    AFS mixer (4)    Quasi-autothermal reactor (5)