Е-Публикации
Технически университет - София

Abstract: This study investigates some of the performance parameters of a single-cylinder spark-ignition engine powered by compressed natural gas (CNG), used to drive an electrical generator under varying load conditions. The engine was tested at constant speed of 3000 min-1 and different load conditions (brake mean effective pressures). The results show that hourly fuel consumption increases with load, while brake specific fuel consumption decreases substantially - from approximately 850g/kWh at no load to 310g/kWh at full load. Correspondingly, the effective thermal efficiency improves logarithmically, reaching up to 24 %. Temperature measurements on the cylinder head, walls, and exhaust indicate significant thermal rise at higher loads. Acoustic levels increase moderately with load but remain primarily governed by engine speed. Importantly, the cost of electricity generation decreases with load, reaching values as low as 0.34 €/kWh, making highload operation economically favorable. Exhaust emission analysis indicates a strong decrease in carbon monoxide (CO) and unburned hydrocarbons (CH) with increasing load. CO levels drop from 1.6 % to 0.28 %, while CH emissions fall from 11 to 7ppm. CO2 levels remain relatively stable (∼ 2.4-2.7%), and oxygen (O2) content rises slightly with load. These findings underscore the potential of CNG-fueled generator engines for efficient and cost-effective energy production, provided they are operated within their optimal load range.

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