Patent GB-1461090-A (GB)
Title: Method and arrangement for supplying a combustible cracked gas mixture to an internal combustion engine
IPC: F02D37/00
Filed: 1974-01-25
Abstract: 1461090 Cracking hydrocarbons SIEMENS AG 25 Jan 1974 [7 Feb 1973] 03649/74 Heading C5E [Also in Division F1] An internal combustion engine is operated using a cracked gas generator for converting initially liquid hydrocarbon fuel, in admixture with a predetermined amount of air and/or exhaust gas, into a combustible cracked gas mixture containing methane, carbon monoxide and/or hydrogen for supply to the engine, by (1) injecting an amount of the liquid fuel into the gas generator proportional to a predetermined relationship which is in part a function of the cracked gas requirement of the engine: (2) supplying the predetermined amount of air and/or exhaust gas to the generator to convert the fuel at an elevated temperature relative to ambient temperature into cracked gas, the supply being such that: (a) the proportion air mixed with vapourized fuel is between 0À05 and 0À5 times the stoichiometric ratio when no exhaust gas is supplied: (b) the proportion of exhaust gas mixed with vapourized fuel (when no air is supplied) is equivalent to the air proportion between 0À05 to 0À5 times the stoichiometric ratio: or (c) the proportion of air, and the proportion of exhaust gas equivalent to air (when both gases are present) is each between 0À05 and 0À5 times the stoichiometric ratio: (3) supplying the cracked gas to the engine: (4) mixing a quantity of air with the cracked gas such that the proportion of air is at least equal to the stoichiometric ratio. The fuel admitted to the generator is mixed with air and/or exhaust gas to achieve an air proportion for the conversion between 0À07 to 0À3 times e.g. 0À09 to 2À0 times, the stoichiometric ratio and not to permit the exhaust gas to fall outside the exhaust gas volume equivalent of the air proportion range. Only as much air may be mixed prior to admission to the combustion chamber of the i.e. engine as will allow the overall air proportion for conversion in the generator and subsequent combustion in the i.e. engine to become at least equivalent to two times e.g. 1À0 to 1À3 times, the stoichiometric ratio. The liquid fuel is injected in an amount at least approx. proportional to the prevailing demand of the i.e. engine, e.g. the amount of fuel is reduced in the high speed range to suit the decreasing charging rate of the engine, into vaporising apparatus downstream of a reaction chamber of the generator, the amount being proportional to the engine throttle control position and speed of the i.c. engine and inversely proportional to the absolute temperature of the air to be mixed with the combustible gas mixture; the number of injection operations is proportional to the i.c. engine speed and the duration of each injection operation is proportional to the throttle control position and inversely proportional to the absolute temperature of the air. The amount of air sucked through the generator is not raised when a specific engine load is exceeded but more liquid fuel is admitted e.g. by injection into the combustible gas mixture leaving the generator, to reduce the air proportion e.g. to 0À2 to 0À1 times the stoichiometric ratio, for conversion in the generator and to increase the calorific value of the generated combustible gas. The temperature in the reaction chamber of the generator may be regulated e.g. may be held approx. constant, by varying the ratio of exhaust gas: air supplied to the generator. Fuel is supplied to the generator corresponding to the proportion of exhaust gas in the exhaust gas-air mixture, less fuel being supplied than under exclusive air admission. A starter set is used for starting the generator and i.e. engine; fuel is ignited to create a flame in the starter set arranged upstream of the generator, the gas resulting from the combustion is sucked by the i.e. engine through a reaction chamber of the starter set containing a small quantity of catalyst relative to the quantity of catalyst in the generator, and continues right through the generator until the starter set catalyst has reached the temperature required for generating a combustible gas mixture containing methane, carbon monoxide, and/or hydrogen, fuel is admitted to the reaction chamber of the starter set, the flame is subsequently extinguished and with a reduced air rate in the reaction chamber of the starter set compared to that required for creation of the flame, a combustible gas mixture is produced which is passed through the generator to heat the latter and, after admixing with more air, is passed to the combustion chambers of the i.e. engine until such time as the generator catalyst has reached the temperature necessary for producing the combustible gas mixture, and upon reaching this temperature, the generator itself is supplied with the requisite amounts of fuel and air and/or exhaust gas for producing the combustible gas mixture which is supplied to the i.e. engine and the starter set is switched off. The fuel admitted is only partially consumed by appropriate proportioning of the amount of air supplied to the starter set, the unburnt flame gases being passed for combustion in the combustion chambers of the internal combustion engine after sweeping through the catalyst of the starter set and the cracked gas generator and after admixture with further air. The amount of air admixed during the starting process prior to combustion in the i.e. engine and sucked in from the engine is less than that required for normal running. An arrangement for supplying an i.e. engine with the combustible cracked gas mixture comprises a cracked gas generator; means for supplying air to a mixing chamber of the generator; means for supplying initially liquid hydrocarbon fuel in vapour form to the mixing chamber in an amount proportional to a predetermined relationship which is in part a function of the cracked gas requirements of the engine; means for supplying recycled exhaust gases to the mixing chamber; a reaction chamber provided in the generator and containing a catalyst for converting the gaseous mixture supplied to the reaction chamber from the mixing chamber at an elevated temperature relative to ambient temperature into a cracked gas mixture; outlet means for supplying the cracked gas mixture to the cylinders of an i.e. engine; and means for mixing a quantity of air with the cracked gas mixture in the outlet means such that the proportion of air is at least equal to the stoichiometric ratio; and means for controlling the supply of fuel, air and/or exhaust gas to the mixing chamber in the proportion defined above. The arrangement may also comprise a fuel evaporating device arranged downstream of the reaction chamber of the generator; a chamber for mixing fuel vapour with air and/or exhaust gas; an air line to the mixing chamber; a combustible gas line from the reaction chamber to the air inlet manifold of the i.e. engine; a combustible gas-air mixing device fitted in the air inlet manifold having a pressure loss characteristic corresponding to that of the generator; a sensor for monitoring the incoming air supply temperature: means for controlling the quantity of fuel to be injected into the evaporating device as a function of the i.e. engine speed, throttle control position and incoming air supply temperature; a sensor for detecting the temperature in the reaction chamber; and a regulator for varying the mixing ratio of the air-exhaust gas mixture admitted to the mixing chamber as a function of the initial signal of the reaction chamber temperature sensor. The regulator controls an element arranged at or close to the connection of an exhaust gas recycling pipe to an air supply pipe for the generator which in turn controls the proportion of exhaust gas supplied to the air supply pipe, and also a fuel injection monitoring device. The combustible gas line is connected between an inlet opening of the air inlet manifold and a throttle valve in the manifold operable by the throttle control, and a spring biased air valve which is the combustible gas-air mixing device is located between the combustible gas line connection and the inlet opening. A starter set for starting the generator and i.e. engine is located upstream of the generator and is actuated by a starting control which after bringing the reaction chamber of the generator up to a predetermined temperature, connects the fuel supply to the generator and switches off the starter set. The starting control may also operate means for decreasing the free flow cross section of the air valve whilst the starter set is operating. A control electronic control and regulating unit may comprise the starting control, a fuel quantity control for monitoring the position of the throttle control, engine speed, suction air temperature and optionally the exhaust gas-air ratio, for controlling operation of the fuel injection apparatus, the regulator unit controlling the composition of the exhaust gas-air mixture to the generator as a function of the reaction chamber temperature.