The paper by Mr T. DATE et al. reported on the principle of the Compound Vortex Controlled Combustion (CVCC) engine regarding the emission characteristics depending on the construction of the engine and the fuel composition. The performance of the engine is influenced by geometrical and operating factors. Important is the ratio of the auxiliary combustion chamber volume Va to the overall clearance volume Vc and the ratio of the torch nozzle area Ft to the auxiliary combustion chamber volume Va. The operating factors of major influence are the fuel-weight ratio between the auxiliary and both the combustion chambers, the air-fuel ratio of the auxiliary combustion chamber, and the total air-fuel ratio.
Fuel consumption and exhaust emissions vary considerably with the geometrical factors. Small values of Va/Vc and Ft/Va lead to increased fuel consumption as well as HC and NO, emissions. With intermediate values fuel consumption and emissions are lowest.
The optimum value of fuel ratio Gf,/GfT regarding best fuel consumption and lowest exhaust emissions under idling conditions is about 40 %, for 50 mph it is about 25 %.
Emissions of vehicles with CVCC engines with displacements of 91, 119, 140 and 350 cubic inches under the LA-4 mode test procedures were within the 1975 US original statutory emission levels.
For fuel aromatic contents of O%, 24% and 53 %, the HC emissions decrease slightly with increasing aromatic content under idling conditions. At 50 mph, this effect was not noticeable. At either load the HC emissions of the CVCC engine were very low compared with those of conventional engines. In conventional and CVCC engines, NO, emissions increase with increasing fuel aromaticity, particularly at 50 mph. Again NO, emission levels of the CVCC engine were much lower than those of the conventional engine.
The fuel distillation characteristic had practically no influence on CO, HC and NO, emissions in the cold stabilised and hot transient phases of the LA-4 mode test procedure. The CVCC engine seems to be one possibility to meet stringent 1975 original exhaust emission levels by stable combustion of the overall lean mixture, with good fuel economy. The aromaticity and the distillation characteristics of the fuel seem to have little effect on the exhaust emissions.
Dr A. REITER (Esso Italiana, Italy) underlined the effects of fuel composition on the mass and type of hydrocarbons emitted by a CVCC vehicle. K. C.
BACHMANN, E. L. KAYLE and E. E. WIGG have recently shown that no significant effect of fuel composition exists on the mass of CO, hydrocarbons or NO, emitted by a 1500 ccm CVCC engine vehicle.
The exhaust hydrocarbon composition for the CVCC was of the same type of relationship of fuel composition as for a 1970 350 CID V-8 conventional engi