Abstract: A process for burning fuel includes the following steps: burning a fuel; putting an inner shell formed in a course of soot formation into contact with other components in a combustion gas to promote a chemical reaction of the other components in the combustion gas prior to the formation of an outer shell; and at the same time, inhibiting the formation of the outer shell around the inner shell. By this process, the discharged NO.sub.x gas is reduced and the amount of discharged soot is decreased.

Abstract: The process and apparatus for reducing soot in soot-containing gases, such as exhaust gases from a Diesel engine, by applying thereto an alternating or pulsating voltage to promote oxidation of soot and to change the character of soot. The resultant gas may be contacted with active medium, such as a heated net of metal or an oxidation catalyst, to oxidize the remaining soot.

Abstract: A spark plug for an internal combustion engine comprises (a) an insulator surrounding a central electrode and (b) a housing having a grounded electrode and disposed on the periphery of the insulator. A taper-nose portion of the insulator, which is designed to be exposed to unburnt carbon in combustion gases of a combustion chamber, is modified to facilitate carbon removal from the taper-nose portion and to maintain excellent electrical insulation. The modification comprises a coating of a mixture of vanadium oxide and zirconium oxide in the form of a porous layer or a sponge-like porous layer having an irregularly-shaped structure with pores; it is fixed to the exposed surface of the taper-nose portion to improve the self-cleaning ability of the spark plug without decreasing the degree of electrical insulation provided by the insulator.

Abstract: A spark plug, wherein a central electrode is electrically insulated from an uter electrically-conductive casing (ground to an internal combustion engine when in use) by an insulator sealed in the casing, separating the central electrode from the casing and having a taper-nose portion which is designed to be exposed to unburnt carbon in combustion gases of a combustion chamber, is modified to facilitate carbon removal from the taper-nose portion. Discrete isolated particles or isolated aggregates of particles of vanadium oxide are adhered over the exposed surface of the taper-nose portion to improve the self-cleaning ability of the spark plug without decreasing the degree of electrical insulation provided by the insulator. The particles of vanadium oxide are formed from a suspension which is applied to the surface of the taper-nose portion of the spark plug. The resulting coating is then dried in situ.