Energy Engineering - Internal Combustion Engines

Multiple choice test

03/09/20 Anticipating the EVO: 1) The temperature of the exhaust gases decreases 2) The pressure of the exhaust gases increases 3) The expansion work increases 4) The combustion process is retarded In a SI engine the PFI process: 1) Is achieved by a GDI 2) Causes the liquid film formation on the walls of the intake duct 3) Includes only the pilot injection 4) Requires an actuation pressure of around 2000 bar in the rail The tumble motion is: 1) Important mainly for CI engines 2) Generated by fuel injection in CI engines 3) Generated by a helical port in the head duct 4) Generated during the intake process The common-rail injection system: 1) Has a rail pressure around 20000 bar 2) Can be applied only to Diesel engines 3) Allows to decouple the spray characteristics from the engine speed 4) Is used to inject the urea solution in the SCR system For a typical gasoline fuel at standard ambient conditions, the laminar flame speed: 1) Has a maximum for a slightly lean mixture 2) Has a maximum for a slightly rich mixture 3) Has a maximum for a stoichiometric mixture 4) Does not depend on the air/fuel ratio mixture With the same total displacement, by halving the number of cylinders, the optimum inertial effect occurs: 1) At the same engine speed 2) At a lower engine speed 3) At a higher engine speed 4) At a lower engine speed only if the gulp factor is higher than 1 In a SI engine, the maximum of NO formed during combustion is typically observed for: 1) Slightly rich mixture 2) Slightly lean mixture 3) Stoichiometric mixture 4) Extremely lean mixture The octane number of commercial gasoline: 1) Must be as low as possible for SI engines 2) Is typically higher than 100 3) Is determined with respect to iso-octane properties 4) Is higher than that of natural gas In a three-way catalyst: 1) Platinum can be replaced by lithium to support the oxidation reactions 2) Noble metals react with chemical species to convert the pollutant emissions 3) Chemical reactions are fast at high substrate temperature 4) The ceramic substrate is porous, to allow a cross-flow though the walls The soot emissions from a Diesel engines: 1) Decrease with the increase of the EGR rate 2) Increase with the increase of the EGR rate 3) Does not depend on the EGR rate 4) Depend on the EGR rate but it cannot be said a priori how