Energy Distribution Analysis of Multiple Injectors for the Double Compression Expansion Engine Concept

Abstract

The present study shows the impact of multiple injectors with distinctive spray and injection angles on the engine efficiency, heat transfer, and exhaust losses. It is well known from previous studies that multiple injectors, particularly two-injectors, improve the air-fuel mixing while simultaneously reducing the heat transfer losses by keeping hot reaction zones away from the combustion cylinder walls. However, it is unclear how the spray-to-spray, umbrella, and spray-orientation angles would impact the overall energy distribution in both the combustion cylinder and double compression expansion engine (DCEE) concept. In this study, three-dimensional (3-D) Reynold-averaged Navier-Stokes (RANS) simulations were conducted in a heavy-duty single-cylinder engine, comparing three-injectors and two different side-injectors cases with a baseline case of centrally mounted single-injector. To obtain the baseline case and validate the computational fluid dynamics (CFD) data, the engine was operated at 1200 rpm, and the fuel mean effective pressure (FuelMEP) of 40 bar using conventional diesel fuel was fixed. One-dimensional (1-D) simulations then utilized the CFD-based in-cylinder pressure and rate of heat release (RoHR) traces to analyse the energy distribution of the DCEE concept. The CFD results show that the three-injectors and the best side-injectors case lead to 1.2%-points and 0.2%-points improvement of gross indicated efficiency and heat losses reduction of 1.3%-points and 2%-points, respectively, compared to the baseline single-injector case. This is due to the longer injector-wall distance from the side-injections, thereby reducing the heat transfer losses, compared to the large coverage area of the high-temperature gases for the baseline case. The 1-D results show that a high brake thermal efficiency of 53% and 52.7% can be achieved with the three-injectors and the best sideinjectors case, respectively, compared to 51.9% of the baseline case. This was due to the advanced combustion phasing, lower heat transfer losses, and higher conversion efficiency of exhaust losses from the combustion cylinder into useful work in the expansion cylinder of the DCEE concept, resulting in an overall higher engine efficiency for multiple injectors.

Performance Analysis and In-Cylinder Visualization of Conventional Diesel and Isobaric Combustion in an Optical Diesel Engine

“…As in our previous studies [32][33][34], Woschni GT heat transfer model, that is based on the classical Woschni equation [16], was implemented in the simulations to account for the in-cylinder heat transfer losses. For all tested conditions, the heat transfer coefficient (ranging from 1.0 to 1.5) was adjusted during all four strokes to closely match the in-cylinder pressure and heat release rates.…”

Optical Diagnostics of Isobaric and Conventional Diesel Combustion in a Heavy-Duty Diesel Engine

“…Isobaric combustion has shown the potential of achieving high engine efficiency while improving the individual losses of heat transfer and exhaust when coupled with a heat recovery system such as split-cycle concepts. Isobaric combustion achieved using singleinjector-based multiple injections [11][12][13] or multiple injectors [14][15][16][17][18][19] can effectively control the heat release rate profile while keeping the peak cylinder pressure (PCP) and bulk gas temperature lower than conventional diesel combustion. Due to reduced flame temperature, isobaric combustion has the benefits of lower heat transfer losses with reduced thermal NO formation.…”

Toward Reduced CO2 Emissions from Vehicles: Onboard Capture and Storage System Using Metal-Organic Frameworks

“…The GT-ISE v2022 software was used to model the engine exhaust gas properties, and the Volvo D13 turbocharged engine is the chosen base platform. The simulation is based on the engine performance tutorials provided by GT-ISE [25], and the geometric engine speci cations, diesel injection pro le, and diesel consumption are provided elsewhere [17,18,[20][21][22][23]. Rijpkema et al [24] stated the boundary conditions at the inlet and outlet of the model, representing the turbocharged ow conditions at the compressor outlet and turbine inlet, respectively.…”

“…The exhaust gas properties are based on a Volvo D13 turbocharged diesel engine model platform and a modi ed version of the European Stationary Cycle as driving operation conditions. Both choices are justi ed by their wide data availability in the literature [17][18][19][20][21][22][23][24][25].…”