Supercharging with Turbo-Compounding - A Novel Strategy to Boost Single Cylinder Diesel Engines

Self Cite

The benefits of turbocharged internal combustion engines are well established in the literature and mass production. Despite the numerous advantages of turbocharging, commercial single-cylinder engines are generally not turbocharged. This is due to intermittent exhaust gas flow to the turbine, typical for a single-cylinder engine. The current work proposes a novel layout wherein a supercharger boosts the engine to reap the benefits of charging the single-cylinder engine. An impulse turbine salvages part of the exhaust energy from the pulsated flow. A one-dimensional simulation study of the novel supercharged and turbo-compounded single-cylinder engine was carried out, and critical parameters of an impulse turbine were designed. CFD simulation study was carried out to validate the performance of the impulse turbine and the novel layout. This study modified a light-duty naturally aspirated (NA) diesel engine currently in mass production into the supercharged version. A positive displacement supercharger was mechanically coupled to the base NA engine with a suitable belt drive, and steady-state experiments were performed with NA and supercharged versions. One-dimensional AVL boost simulation models were validated for the NA and supercharged engines for brake power, air flow rate and BSFC within a 3% deviation. Nozzles of varying exit diameters were employed at the exhaust pipe. One-dimensional simulations were conducted to predict the supercharged engine performance and the kinetic energy rate available at the exhaust nozzle exit. An optimal nozzle exit diameter was chosen. Base calculations for the impulse turbine were performed with the output from the 1D simulation tool to design the critical features of the blade and the power turbine. The designed impulse turbine was further simulated using a commercially available CFD simulation tool, CONVERGE. CFD results showed that the impulse turbine generated about 1.55 kW of power, equivalent to 39% turbine efficiency. Experimental analysis was conducted on the supercharged engine with the optimal nozzle and the simulated impulse turbine. Results showed significantly improved engine performance with the supercharged and impulse turbine compounded version compared to the base NA version. The brake power output and brake thermal efficiency increased by 34% and 3.8%, respectively. Soot and carbon monoxide (CO) emissions were 80% lower, while unburned hydrocarbon (HC) emissions were 45% lower. However, NOx emissions were 60% higher, which can be curtailed by established NOx reduction strategies. Thus, the proposed method of employing a supercharger and compounding an impulse turbine for a single-cylinder diesel engine proved beneficial with improved performance, reduced brake specific fuel consumption and reduced emissions except for NOx.

Section: Impulse Turbine Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…6,11–13 Hence, turbocharging the single-cylinder engine remains technically challenging, and few research attempts have been made so far. 8–10…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A novel layout to charge a single cylinder diesel engine using supercharging and impulse turbo-compounding

Ramkumar

Krishnasamy

Ramesh

2023

Self Cite

Design of a novel impulse turbine for exhaust energy recovery in a commercial load carrier single cylinder diesel engine

Ramkumar,

Krishnasamy,

Ramesh

2024

A significant fraction of the fuel energy supplied in a diesel engine is wasted into the atmosphere through the exhaust gases. Although most modern-day diesel engines are turbocharged, a few remain naturally aspirated. Due to technical challenges, single-cylinder engines are not turbocharged and remain naturally aspirated (NA). The intermittent and pulsated exhaust gas flow tends to choke the turbine and increase the back pressure. On the other hand, supercharging a single-cylinder engine leads to superior performance at the expense of fuel efficiency, as a significant fraction of the energy is wasted in the exhaust. The current study employs a novel crank shaft coupled impulse turbine for effective exhaust energy recovery in a supercharged, high-speed, commercial single-cylinder diesel engine. This novel impulse turbo-compounded and supercharged engine layout was simulated using a 1D model developed using AVL BOOST software. Based on the results of the 1D model, the impulse turbine design was carried out. A CFD simulation of the impulse turbine was carried out using commercially available CONVERGE. The major design parameters, including blade profile, blade width, nozzle shape, size and angle, blade angles, blade speed, number of blades, and turbine outlet port opening, were optimized using the CFD software. The simulated results showed that the designed impulse turbine generated 2.67 kW of power, enhancing the power output of the supercharged engine by 21% at the rated operating condition. The turbine efficiency was 68%, considering the available kinetic energy at the exhaust. Simulation results indicate that the impulse turbine compounded supercharged engine could generate 15.4 kW of power, 45% higher than the base NA engine brake power output.

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

Ramkumar,

Anand,

Ramesh

2024

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.