ARAI, the Automotive Research Association of India, has developed a 6-cylinder methane/diesel dual-fuel engine using injection technology. ARAI says a six cylinder engine was chosen due to its importance for intercity bus and truck applications. It says the benefits of dual-fuel technology include fuel flexibility, lower emissions, retaining diesel compression ratio, better efficiency and easy conversion of existing diesel engines without major hardware modifications.
Table 1: Comparison of emissions
The dual fuel combustion technology demonstrated by ARAI uses a dual-fuel CNG injection kit, which facilitates CNG single point and multi-point injection with diesel replacement up to 60% for part load conditions. At idling and full load conditions the engine operates solely on diesel fuel. This ensures that there is no power drop as compared to neat diesel operation. This also prevents thermal overloading of the engine. It is observed that dual-fuel operation reduces smoke and PM emissions by approx. 35-40%, CO is marginally reduced and NOx and HC are comparable with diesel operation.
The dual-fuel engine has successfully met BS-III norms with sufficient margin using a suitable low loading oxidation catalyst.
The dual-fuel technology has been evaluated with respect to its effect on engine performance, emissions, ease of commercialization and importance and scope in the Indian context. Given the continuing expansion of CNG infrastructure across India ARAI concludes this technology can be used for all generation of diesel engine technologies.
(This article compiled using information from the ARAI Journal, July 2011)
