A controller for a hydrogen engine controls a hydrogen engine including a selective catalytic reduction (SCR) device installed in an exhaust passage and a urea addition valve that adds urea to exhaust gas flowing through a portion of the exhaust passage upstream of the SCR device. Processing circuitry of the controller executes a reduction process that causes a urea addition amount of the urea addition valve to be smaller when a urea deposition amount of the SCR device is greater than or equal to a prescribed value than when the urea deposition amount is less than the prescribed value. The processing circuitry executes a lean-burn limiting process that sets an air-fuel ratio of an air-fuel mixture to be burned in the hydrogen engine to a value less than or equal to a prescribed lean-burn limiting value while the reduction process is reducing the urea addition amount.

An internal combustion engine in which a hydrocarbon feed valve, exhaust purification catalyst, and NO.sub.X selective reduction catalyst are arranged in an engine exhaust passage. A first NO.sub.X removal method which injects hydrocarbons from the hydrocarbon feed valve within a predetermined range of period and uses the reducing intermediate which is generated due to this so as to reduce the NO.sub.X contained in the exhaust gas and a second NO.sub.X removal method which makes the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst rich with a period longer than this predetermined range are used. When the first NO.sub.X removal method should be used and the amount of adsorbed ammonia at the NO.sub.X selective reduction catalyst is large, use of the first NO.sub.X removal method is stopped.

A reformer system may include a reformer device having a fuel inlet, an air inlet and a gas outlet, a first valve set coupled to the fuel inlet and configured to selectively supply a reformer fuel flow from an engine fuel flow to the fuel inlet, a second valve set coupled to the air inlet and configured to selectively supply a reformer air flow from a compressor outlet air flow to the air inlet, and a controller in electrical communication with the first valve set and the second valve set. The controller may determine a target reformer fuel flow based on a target gas flow, determine a target reformer air flow based on the reformer fuel flow and a target air-to-fuel ratio, adjust the reformer fuel flow according to the target reformer fuel flow, and adjust the reformer air flow according to the target reformer air flow.

A catalyst system comprising a first catalytic composition comprising a homogeneous solid mixture containing at least one catalytic metal and at least one metal inorganic support. The pores of the solid mixture have an average diameter in a range of about 1 nanometer to about 15 nanometers. The catalytic metal comprises nanocrystals.

A fuel reformer includes a reforming-fuel injection valve and a fuel reformer catalyst disposed in an EGR pipe and performs a catalyst recovery control when a preset fuel cut execution condition is satisfied. In the catalyst recovery control, a fuel reforming capacity of the fuel reformer catalyst is recovered by stopping an injection of a main fuel and an injection of a reforming-fuel, while supplying additional air to the catalyst by maintaining both of an EGR valve and a throttle valve in a valve open state. Further, in the catalyst recovery control, temperature and a carbon deposit amount of the fuel reformer catalyst are estimated or detected based on which of an opening of the EGR valve and an opening of the throttle valve are adjusted. As a result, fuel reforming capacity is recovered without decreasing a fuel consumption rate improvement effect and a worsening of exhaust emission or drivability.

A system for reforming a fuel may include a first sensor configured to measure an operating parameter of an engine. The operating parameter may correlate to a NO.sub.x emission level of the engine. The system may also include a controller in communication with the sensor and a reformer. The controller may be configured to determine a target NO.sub.x emission level for the engine. The controller may be also configured to determine a target value of the operating parameter corresponding to the target NO.sub.x emission level. The controller may be further configured to control the reformer to reform at least a portion of the fuel based on a difference between the measured value and the target value of the operating parameter.

An exhaust gas purification system which is capable of purifying exhaust gas without a noble metal being carried, and maintaining exhaust gas purification performance even at high temperatures; a catalyst; and an exhaust gas purification method are disclosed. A foamed metal catalyst which is made of a transition metal element excepting platinum group elements and is formed of a metal having a porosity of not less than 80%, and which reduces NOx by being brought into contact with an exhaust gas having a hydrogen concentration of not less than a predetermined concentration (e.g., 2%) and a temperature of not less than 230 C., is provided in an exhaust gas passage of an internal combustion engine that discharges the exhaust gas.

A method for purifying exhaust gas of an internal combustion engine, including chemically reducing NOx that is contained in the exhaust gas when a concentration of hydrocarbons flowing into an exhaust purification catalyst is made to vibrate within a predetermined range of amplitude and within a predetermined range of period, wherein, during the chemical reduction, the NOx contained in the exhaust gas is reacted with reformed hydrocarbons to produce a reducing intermediate containing nitrogen and hydrocarbons, a reducing action of the reducing intermediate chemically reduces the NOx, and the NOx is chemically reduced without storing nitrates or with storing a fine amount of the nitrates in a basic layer of the exhaust purification catalyst.

A carrier gas supplied from a carrier gas source is injected from a carrier gas injection nozzle. Also, a fuel including a hydrocarbon-based liquid and supplied from a fuel source is supplied to a tip end of the carrier gas injection nozzle, whereby this fuel is atomized with the carrier gas injected from the carrier gas injection nozzle. Furthermore, an inlet of a reforming part that decomposes the atomized fuel and reforms the atomized fuel into a reducing gas including either or both of hydrogen and an oxygen-containing hydrocarbon is provided so as to face the carrier gas injection nozzle and the fuel supply nozzle, and a reducing gas supply nozzle that supplies the reducing gas discharged from an outlet of the reforming part is provided in an exhaust pipe.

The exhaust system of a diesel engine includes components such as a turbocharger and an exhaust manifold which can have very high internal temperatures (e.g., any surface having a temperature above 135 C.). In accordance with the invention the components subject to the high temperatures are coated with at least a first layer of thermally insulating material and a second layer overlying the first layer to provide surface protection. So coated, the temperature of the outer coated surfaces of these components is brought below an undesirably high level. Also, selected ones of the components may be water cooled and/or have a fitted jacket and/or be placed within an explosion proof enclosure. The input fuel line may also include a magnetic explosion proof fuel economizer to control the combustion process and reduce the internal temperature.