Novel approaches of charging and compounding a single-cylinder diesel engine

Conventionally, charging the single-cylinder engine by turbocharging or supercharging has always been technically challenging. Turbocharging the single-cylinder engine reduces performance due to higher pumping losses and the phase lag between the intake and exhaust valves. Although employing a supercharger enhances the potential for extracting higher power output, the higher brake specific fuel consumption is a disadvantage due to the power consumed by the supercharger. Furthermore, the energy in the exhaust gases is inevitably discharged into the atmosphere. Hence, single-cylinder engines have been significantly underpowered and under-utilized for several decades. The work explores three novel approaches to charge and compound a commercial single-cylinder diesel engine. Firstly, a novel concept of turbocharging the single-cylinder engine using an exhaust plenum was studied. Then, a novel supercharging and turbo-compounding of the test engine is explored, followed by an impulse turbine compounding. All three novel approaches were simulated with a 1D model developed using the commercial 1D simulation software AVL BOOST. Experiments were carried out on the naturally aspirated, supercharged, and turbocharged single-cylinder engine, while simulated results were used on the impulse turbine. Results showed that with the first novel approach, the turbocharged single-cylinder engine delivered 33% higher brake power output with a 345 basis points (3.45% points) improvement in brake thermal efficiency compared to the base naturally aspirated (NA) engine. With the second approach, the supercharged and impulse turbine compounded engine generated 15 kW of power, 47% higher, with 700 basis points (7% points) of improved brake thermal efficiency compared to the base naturally aspirated (NA) engine. The third novel approach delivered 11% higher engine brake power output with 354 basis points improvement (3.54% points) in brake thermal efficiency compared to the base naturally aspirated (NA) engine. All three novel approaches also delivered reduced emissions levels except for oxides of nitrogen (NOx) emissions.