Full Load Investigation of CNG—Diesel Dual-Fuel Heavy-Duty Engine with Selective Catalytic Reduction on Engine Performance and Emissions for Its Potential Use

The application of compressed natural gas (CNG) as fuel for compression ignition (CI) engines under dual-fuel (DF) mode operation is not attempted in countries like India for commercial purposes. A commercial heavy-duty turbocharged six-cylinder common-rail direct-injected diesel engine has been converted into a DF mode of operation using CNG and diesel for its potential usage and study on its performance along with Selective Catalytic Reduction (SCR). CNG is inducted through the intake manifold at varying energy substitution rates (ESR) with a flow rate of 0.67-1.54 kg/h while diesel fuel is controlled through the engine electronic control unit (ECU). For a maximum ESR of 10.2% with CNG, an increase in power by 8.9% and a 5.8% increase in torque were observed. While there was an increase in brake thermal efficiency (BTE), volumetric efficiency marginally decreased, therefore, to have higher brake power with a DF engine, a dedicated turbocharging system is necessary. The brake-specific energy (BSEC)/fuel consumption (BSFC) has marginally reduced by 1%, and optimum engine speed for better fuel economy was in the range of 1250-2250 rpm. The brake-specific carbon monoxide (BSCO) and carbon dioxide (BSCO₂) emissions have considerably reduced while brake-specific non-methane hydrocarbon (BSNMHC), oxides of nitrogen (BSNOx), and methane (BSCH₄) emission was marginally higher with CNG substitution; however, within Euro 4 emission norms. Unregulated emissions like ammonia (NH₃), propane, and sulfur dioxide (SO₂) have reduced while formaldehyde, acetylene, ethylene, and formic acid have marginally increased. SCR has been useful in reducing mass emissions out from the diesel engine and in conversion.