Experimental Study on CNG Engine with Different Ventury Configuration

Abstract

Low carbon to hydrogen ratio of compressed natural gas (CNG) is counted as one of the better potential as an alternate fuel instead of conventional fuel for an internal combustion engine. CNG engines have very low particulate emission and lower brake specific fuel consumption compared to conventional fuelled IC engines. Design of carburetion system plays vital role in both conventional CNG engines as well as in dual fuel engines in consideration of better performance and emissions. The restriction barrel named venturi governs the crucial operation of the carburetor. In the presented study, main intention was to achieve an optimum ratio by suitably designing a venturi type gas mixer which mixes the CNG gas with incoming air. Fulfilling the design need, three venturi type gas mixer were designed by varying number of holes, hole size and throat diameter. A four stroke, single cylinder, VCR research engine was used to trial with different venturi configuration for engines carburetion system and their performance as well as exhaust emissions were compared. According to the experimental results, venturi 2 with 23 mm throat diameter and 8 numbers of holes was resulted the most optimal venturi design. During the experimentation at full load, air–fuel equivalence ratio was found close to 1 and equivalence ratio to 0.88, which is the need of CNG engines to run smoothly. This satisfies the venturi type gas mixer design requisite for CNG engine. It is also observed that optimized number of holes improves the engine performance and emission as well.