| 1. |
- Preuss, Josefine, 1989, et al.
(författare)
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Effect of Injection Strategy and EGR on Particle Emissions from a CI Engine Fueled with an Oxygenated Fuel Blend and HVO
- 2021
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Konferensbidrag (refereegranskat)abstract
- Alcohol-based fuels are a viable alternative to fossil fuels for powering vehicles. As a drop-in fuel, an oxygenated fuel blend containing the C8 alcohol 2-ethylhexanol (isomer of octanol), hydrotreated vegetable oil (HVO) and rapeseed methyl ester (RME) can reduce soot and NOx emissions whilst maintaining engine performance. However, fuel injection strategy significantly affects combustion and hence has been investigated with a view to reducing emissions whilst maintaining engine efficiency. In a single cylinder light-duty compression ignition research engine, the effect of different injection strategies (main, main/post, double pre/main, double pre/main/post injection) and EGR levels (0%, 19%) on specifically NOx, soot emissions and particle size distribution was investigated for three different fuels: fossil diesel fuel, HVO and the oxygenated blend. The blend was designed to have diesel-like combustion properties (cetane number of 52) and had an oxygen content of 5.4% by mass. The crank angle used when measuring MFB50, fuel consumption and IMEP was kept constant. The engine efficiencies were similar for all tested fuels and injection strategies. Heat release analysis revealed a strong influence of the cetane number on main and main/post injection strategy. However, when using double pre-injection, the start of combustion was similar for all fuels. Combustion characteristics, particle mass and number were more affected when using double pre-injection rather than post-injection. With 19% EGR and double pre-injection, soot mass increased as agglomerated particle mode increased in the PSD. Further, the in-cylinder temperature and pressure were lower compared to combustion without EGR, leading to a reduction of NOx emissions by a factor of 2.5 while soot emissions increased by a factor of 10. There were just minor differences in NOx emissions with variations in injection strategy. The PSD moved towards smaller particle diameters without EGR. In conclusion, the soot reduction potential of all fuels tested was coupled to the use of double pre-injection and EGR rather than post-injection.
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| 2. |
- Preuss, Josefine, 1989, et al.
(författare)
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Performance and emissions of renewable blends with OME3-5 and HVO in heavy duty and light duty compression ignition engines
- 2021
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 303
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Tidskriftsartikel (refereegranskat)abstract
- Interest in poly(oxymethylene)dimethyl ether (OME3-5) as an alternative to fossil fuels in compression ignition engines has increased owing to its potential for soot reduction. The high oxygen content of the polymer and lack of carbon–carbon bonds and aromatic structures can help to reduce engine out soot emissions. However, OME3-5 is potentially damaging to engine components, and thus engine modifications are required when using neat OME3-5. In the present study, OME3-5 was blended with hydrotreated vegetable oil (HVO), rapeseed methyl ester and the C8-alcohol 2-ethylhexanol (an isomer of n-octanol) to ensure miscibility. Three blends were designed with an oxygen content of 6.4, 12.8 and 17.8% by mass. Performance and emissions were compared to the reference fuels fossil diesel and HVO in a single cylinder light duty and heavy duty compression ignition engine at different loads. Evaluation of the combustion in both engines showed similar trends: The indicated thermal efficiency was slightly higher for the oxygenated fuel and the combustion duration shorter compared to diesel. Due to the lower heating value of the blends, the indicated specific fuel combustion increased with increasing share of OME3-5 in the blend. For both engines, engine out soot emissions were decreased strongly, whereas NOx emissions were slightly increased. Analysis of the particle size distribution showed a decrease in the particle number of agglomerated particles (>30 nm) for the blends. For the heavy duty engine, an increase in nucleation mode particles (<30 nm) was measured.
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| 3. |
- Rijpkema, Jelmer Johannes, 1982, et al.
(författare)
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Exhaust waste heat recovery from a heavy-duty truck engine: Experiments and simulations
- 2022
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- Waste heat recovery using an (organic) Rankine cycle is an important and promising technology for improving engine efficiency and thereby reducing the CO2 emissions due to heavy-duty transport. Experiments were performed using a Rankine cycle with water for waste heat recovery from the exhaust gases of a heavy-duty Diesel engine. The experimental results were used to calibrate and validate steady-state models of the main components in the cycle: the pump, pump bypass valve, evaporator, expander, and condenser. Simulations were performed to evaluate the cycle performance over a wide range of engine operating conditions using three working fluids: water, cyclopentane, and ethanol. Additionally, cycle simulations were performed for these working fluids over a typical long haul truck driving cycle. The predicted net power output with water as the working fluid varied between 0.5 and 5.7 kW, where the optimal expander speed was dependent on the engine operating point. The net power output for simulations with cyclopentane was between 1.8 and 9.6 kW and that for ethanol was between 1.0 and 7.8 kW. Over the driving cycle, the total recovered energy was 11.2, 8.2, and 5.2 MJ for cyclopentane, ethanol, and water, respectively. These values correspond to energy recoveries of 3.4, 2.5, and 1.6%, respectively, relative to the total energy requirement of the engine. The main contribution of this paper is the presentation of experimental data on a complete Rankine cycle-based WHR system coupled to a heavy-duty engine. These results were used to validate component models for simulations, allowing for a realistic estimation of the steady-state performance under a wide range of operating conditions for this type of system.
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| 4. |
- Rijpkema, Jelmer Johannes, 1982, et al.
(författare)
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Experimental investigation and modeling of a reciprocating piston expander for waste heat recovery from a truck engine
- 2021
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 186
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Tidskriftsartikel (refereegranskat)abstract
- Waste heat recovery using an (organic) Rankine cycle has the capacity to significantly increase the efficiency of heavy-duty engines and thereby reduce fuel consumption and CO2 emissions. This paper evaluates a reciprocating piston expander used in a Rankine cycle for truck waste heat recovery by quantifying its performance on the basis of experimental results and simulations. The experimental results were obtained using a setup consisting of a 12.8 L heavy-duty Diesel engine connected to a Rankine cycle with water and are used to calibrate a semi-empirical expander model. At an engine power between 75 and 151 kW, this system recovered between 0.1 and 3 kW, resulting in an expander filling factor between 0.5 and 2.5, and a shaft isentropic effectiveness between 0.05 and 0.5. The calibrated model indicated that the heat loss (16%), mechanical loss (6–25%), pressure drop (13–42%), and leakage (25–75%) all contributed significantly to the expander performance loss. A simulation study with acetone, cyclopentane, ethanol, methanol, and R1233zd(E), showed that a change of working fluid significantly impacts the expander performance, with the filling factor varying between 0.5 and 2.2 and the effectiveness between 0.01 and 0.5, depending on the working fluid, expander speed, and pressure ratio. The results of the optimization of the built-in volume ratio and inlet valve timing during a typical long haul driving cycle showed that acetone and R1233zd(E) provided the highest available power around 3 kW absolute, or 2.2% relative to the engine. The main contributions of this paper are the presentation of experimental results of an engine coupled to a Rankine cycle, and the quantification of performance losses and the effect of working fluid variation using an adapted semi-empirical expander model, which allows for a selection of the working fluid and geometrical modifications giving optimal performance during a long haul driving cycle.
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| 5. |
- Rijpkema, Jelmer Johannes, 1982, et al.
(författare)
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Experimental study of an organic Rankine cycle with R1233zd(E) for waste heat recovery from the coolant of a heavy-duty truck engine
- 2021
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904. ; 244
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Tidskriftsartikel (refereegranskat)abstract
- Waste heat recovery is an effective method for improving engine efficiency. While most research on waste heat recovery from heavy-duty engines focuses on the high-temperature heat sources, this paper investigates the performance of a low-temperature system. The experimental setup features an organic Rankine cycle with R1233zd(E) as the working fluid recovering heat from the coolant of a heavy-duty Diesel engine. Experiments at multiple engine operating points indicated a maximum operating cycle pressure of 8 bar and temperature of 92 °C. Between 0.1 and 0.7 kW net shaft power was achieved with a thermodynamic efficiency between 1.1 and 1.8%, resulting in a maximum expander power of 0.7% relative to the engine power. A simple empirical model based on the experimental results indicated that approximately 0.7% of the engine's energy could be recovered during a driving cycle, rising to 1.3% if a high efficiency pump and expander are used. The main contribution of this paper lies in the presentation of the experimental setup and experimental results specifically dedicated to recovering the heat from the engine coolant, which permits realistic evaluation of the performance.
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| 6. |
- Singh, Vikram, et al.
(författare)
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On the effects of increased coolant temperatures of light duty engines on waste heat recovery
- 2020
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 172
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, an investigation is done into the potential of increasing the coolant temperature of an engine to maximize the powertrain efficiency. The study takes a holistic approach by trying to optimise the combined engine and waste heat recovery system. The work was done experimentally on a Volvo 4-cylinder light duty diesel engine in combination with Rankine cycle simulations. For the study, the coolant temperature was swept from 80 °C to 160 °C at different operating points. It was seen that with increased coolant temperatures, the brake efficiency of the engine increased by up to 1 percentage point due to reduced heat losses. An optimum coolant temperature was observed, dependent on the operating point, for maximizing coolant recoverable power. An expansive study was done simulating 48 working fluids for a dual loop waste heat recovery system. From the working fluids simulated, cyclopentane was seen as the best for coolant waste heat recovery, whereas methanol and acetone were better for the exhaust gases. The gain in efficiency seen, was up to 5.2 percentage points, with up to 1.7 percentage points as the effect due to recovered power from the coolant.
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| 7. |
- Singh, Vikram, et al.
(författare)
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Optimization and Evaluation of a Low Temperature Waste Heat Recovery System for a Heavy Duty Engine over a Transient Cycle
- 2020
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Ingår i: SAE Technical Papers. - : SAE International. - 0148-7191 .- 2688-3627.
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Tidskriftsartikel (refereegranskat)abstract
- Powertrain efficiency is a critical factor in lowering fuel consumption and reducing the emission of greenhouse gases for an internal combustion engine. One method to increase the powertrain efficiency is to recover some of the wasted heat from the engine using a waste heat recovery system e.g. an organic Rankine cycle. Most waste heat recovery systems in use today for combustion engines use the waste heat from the exhaust gases due to the high temperatures and hence, high energy quality. However, the coolant represents a major source of waste heat in the engine that is mostly overlooked due to its lower temperature. This paper studies the potential of using elevated coolant temperatures in internal combustion engines to improve the viability of low temperature waste heat recovery. The paper first uses engine experiments and multi-linear regression analysis to model the indicated efficiency and recoverable power for a Scania D13 heavy duty engine across a range of engine loads, speeds and coolant temperatures. The recoverable power is obtained from simulations of a dual loop waste heat recovery system using ten working fluids as potential candidates for recovering heat from the exhaust gases and the coolant. The paper then investigates the maximum potential fuel consumption benefit by using elevated coolant temperatures for the Scania engine running on the World Harmonized Transient Cycle. From the simulation results, it was seen that cyclopentane and methanol were the best performing working fluids for the coolant and exhaust gas heat sources respectively. From the analysis on the World Harmonized Transient cycle, when using the best performing working fluids and elevated coolant temperatures, a potential net reduction in fuel consumption of 9% could be obtained.
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| 8. |
- Zhang, Tankai, 1988, et al.
(författare)
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Effects of a wave-shaped piston bowl geometry on the performance of heavy duty Diesel engines fueled with alcohols and biodiesel blends
- 2020
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 148, s. 512-522
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Tidskriftsartikel (refereegranskat)abstract
- The effects of a new wave-shaped piston bowl design on combustion characteristics and engine out emissions were tested in a heavy duty Diesel engine fueled with conventional Diesel and fossil-free blends containing n-butanol, n-octanol, 2-ethylhexanol, hydrotreated vegetable oil, and rapeseed methyl ester. The compositions of the blends were chosen such that their cetane numbers matched that of fossil Diesel. Engine experiments were performed at four operating points from the European Stationary Cycle, with no modification of engine settings when switching between different fuels. A standard piston with omega geometry was tested using fossil Diesel and the fossil-free nBu30H (30% n-butanol and 70% hydrotreated vegetable oil by volume) blend, and the results obtained were compared to those achieved with the wave piston. In general, the fossil-free blends yielded significantly lower soot emissions than fossil Diesel but slightly higher NOx emissions. Relative to the standard piston, the wave piston accelerated the combustion of both Diesel and fossil-free blends, especially the diffusion combustion. The wave piston's positive effects on thermal efficiency and soot emissions were more pronounced for conventional Diesel fuel than for oxygenated nBu30H.
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