Increasingly stringent emission regulations and environmental concerns have propelled the develop... more Increasingly stringent emission regulations and environmental concerns have propelled the development of electrification technology in the transport industry. Yet, the greatest hurdle to developing fully electric vehicles is electrochemical energy storage, which struggles to achieve profitable specific power, specific energy and cost targets. Hybrid energy storage systems (HESSs), which combine energy- and power-optimised sources, seem to be the most promising solution for improving the overall performance of energy storage. The potential for gravimetric and volumetric reduction is strictly dependent on the overall power-to-energy ratio (PE ratio) of the application, packaging factors, the minimum and maximum PE ratio achievable for the system’s energy- and power-optimised sources and the performance of power electronics. This paper presents a simple optimisation methodology that considers these factors and identifies the optimal HESS requirements that may present new opportunities ...
All human drivers can be characterised by their habitual choice of driving behaviours, which resu... more All human drivers can be characterised by their habitual choice of driving behaviours, which results in a wide range of observed driving patterns and manoeuvres. Developing control strategies for autonomous vehicles that address this feature would increase the public acceptance of such vehicles. Therefore, this paper proposes a novel approach to developing rule-based fuzzy logic driver models that simulate different driving styles in the car-following regimes. These driver models were trained with the collected on-road driving data to capture corresponding human drivers’ characteristics. The proposed approach consists of three main components: collecting on-road driving data, developing a vehicle model, and establishing the car-following driver models. Firstly, an instrumented vehicle was used to collect driving data over the same route for three consecutive months. Car-following scenarios during these journeys were extracted, and related data were processed accordingly. Afterwards,...
In regulated two-stage sequential turbocharging systems, a smaller, high pressure (HP), and a lar... more In regulated two-stage sequential turbocharging systems, a smaller, high pressure (HP), and a larger, low pressure (LP), turbocharger are sequentially positioned to recover the energy available in the exhaust gases and deliver acceptable level of boost to the intake of an internal combustion engine. Due to the different sizes of the turbochargers, by-pass valves are placed in the system to control operations. Due to the turbocharging system layout, it is clear that the air pressurized by the LP compressor enters nonuniformly the HP compressor. This is caused by the rotating radial compressor and the interconnecting bends which cause swirl and velocity to scatter, respectively. Furthermore, the heat transfer in the two turbochargers may have an effect on the apparent efficiencies. For these reasons, the standard mapping approach for turbochargers is not able to take into account the effect of non-uniform flow and heat transfer. In this paper, a novel approach for mapping the two-stage turbocharging system is proposed and performed into a monodimensional simulation code. Although, flow non-uniformity and turbochargers heat transfer effects on the performance of the turbocharging system are not considered, at this present time, the study centralizes on the investigation and the validation of the mapping approach. In fact, a two-stage sequential turbocharging system has been considered for the study and a simulation code to investigate the mapping technique has been implemented.
Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissio... more Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissions standards. However, their range of operation is limited for low mass flows by compressor surge. Operation in surge results in pressure and mass flow oscillations that are often damaging to the compressor and its installation. Since surge is a highly complex flow regime, full unsteady 3D models are generally too computationally expensive to run. The majority of current low-dimensional surge models use a cubic compressor characteristic that needs to be fitted to experimental data. Therefore, each time a compressor is studied using these models, costly experimental testing is required. In this paper, a new technique for obtaining an axisymmetric centrifugal compressor characteristic is presented. This characteristic is built using the equations of mass, momentum and energy from first principles in order to provide a more complete model than those currently obtained via experimental data. This approach enables us to explain the resulting cubic-like shape of the characteristic and hence to identify impeller inlet stall as a route into surge. The characteristic is used within a quasi-steady, map-based surge model in order to demonstrate its ability to predict the onset of surge while only providing geometric data as input. Validation is provided for this model by discussion of the qualitative flow dynamics and a good fit to experimental data, especially for low impeller speeds and pressure ratios.
Current trend on engine downsizing forces engine manufacturers to contemplate powertrains with mo... more Current trend on engine downsizing forces engine manufacturers to contemplate powertrains with more than one boosting device. The presence of these devices leads to complex 1-D engine models which rely on performance maps provided by turbo/supercharger manufacturers. So far, no detailed analysis has been carried out to understand how these maps affect engine performance simulation. As part of the UltraBoost project (65% gasoline engine downsizing), Imperial College tested the boosting components of a turbo-super configuration. The acquired data were used to assess the effectiveness of 1-D engine performance prediction and to contemplate the opportunity to exploit the boosting system and use it as engine charge air cooler in the form of an expander.
Journal of engineering for gas turbines and power, Feb 23, 2017
For an internal combustion engine, a large quantity of fuel energy (accounting for approximately ... more For an internal combustion engine, a large quantity of fuel energy (accounting for approximately 30% of the total combustion energy) is expelled through the exhaust without being converted into useful work. Various technologies including turbocompounding and the pressurized Brayton bottoming cycle have been developed to recover the exhaust heat and thus reduce the fuel consumption and CO2 emission. However, the application of these approaches in small automotive power plants has been relatively less explored because of the inherent difficulties, such as the detrimental backpressure and higher complexity imposed by the additional devices. Therefore, research has been conducted, in which modifications were made to the traditional arrangement aiming to minimize the weaknesses. The turbocharger of the baseline series turbocompounding was eliminated from the system so that the power turbine became the only heat recovery device on the exhaust side of the engine, and operated at a higher expansion ratio. The compressor was separated from the turbine shaft and mechanically connected to the engine via continuous variable transmission (CVT). According to the results, the backpressure of the novel system is significantly reduced comparing with the series turbocompounding model. The power output at lower engine speed was also promoted. For the pressurized Brayton bottoming cycle, rather than transferring the thermal energy from the exhaust to the working fluid, the exhaust gas was directly utilized as the working medium and was simply cooled by ambient coolant before the compressor. This arrangement, which is known as the inverted Brayton cycle (IBC) was simpler to implement. Besides, it allowed the exhaust gasses to be expanded below the ambient pressure. Thereby, the primary cycle was less compromised by the bottoming cycle. The potential of recovering energy from the exhaust was increased as well. This paper analyzed and optimized the parameters (including CVT ratio, turbine and compressor speed and the inlet pressure to the bottoming cycle) that are sensitive to the performance of the small vehicle engine equipped with inverted Brayton cycle and novel turbocompounding system, respectively. The performance evaluation was given in terms of brake power output and specific fuel consumption. Two working conditions, full and partial load (10 and 2 bar brake mean effective pressure (BMEP)) were investigated. Evaluation of the transient performance was also carried out. Simulated results of these two designs were compared with each other as well as the performance from the corresponding baseline models. The system models in this paper were built in GT-Power which is a one dimension (1D) engine simulation code. All the waste heat recovery systems were combined with a 2.0 L gasoline engine.
Dynamic modelling of engine emissions is important because it promises significant improvements o... more Dynamic modelling of engine emissions is important because it promises significant improvements over static modelling for engine calibration through reduced testing and development times. Volterra series and neural network dynamic model structures were trained using transient data from an engine test stand under sinusoidal excitations and the predictive power over the New European Drive Cycle (NEDC) cycle was assessed for a EURO IV specification Diesel engine. Models were identified for oxides of nitrogen (NOx) and carbon dioxide (CO2) emissions concentrations based on engine speed, torque, injection timing, EGR rate and fuel injection pressure. The fit R 2 values for CO2 emissions for Volterra series and Neural networks were 0.92 and 0.99 respectively; for NOx emissions these were 0.92and 0.998. Although this suggests better flexibility from the Neural network to represent the nonlinearity there were large variations in predictive power resulting from the partially random nature of...
Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissio... more Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissions standards. However, their range of operation is limited for low mass flows by compressor surge. Operation in surge results in pressure and mass flow oscillations that are often damaging to the compressor and its installation. Since surge is a highly complex flow regime, full unsteady three-dimensional models are generally too computationally expensive to run. The majority of current low-dimensional surge models use a cubic compressor characteristic that needs to be fitted to experimental data. Therefore, each time a compressor is studied using these models, costly experimental testing is required. In this paper, a new technique for obtaining an axisymmetric centrifugal compressor characteristic is presented. This characteristic is built using the equations of mass, momentum, and energy from first principles in order to provide a more complete model than those currently obtained via ex...
Increasingly stringent emission regulations and environmental concerns have propelled the develop... more Increasingly stringent emission regulations and environmental concerns have propelled the development of electrification technology in the transport industry. Yet, the greatest hurdle to developing fully electric vehicles is electrochemical energy storage, which struggles to achieve profitable specific power, specific energy and cost targets. Hybrid energy storage systems (HESSs), which combine energy- and power-optimised sources, seem to be the most promising solution for improving the overall performance of energy storage. The potential for gravimetric and volumetric reduction is strictly dependent on the overall power-to-energy ratio (PE ratio) of the application, packaging factors, the minimum and maximum PE ratio achievable for the system’s energy- and power-optimised sources and the performance of power electronics. This paper presents a simple optimisation methodology that considers these factors and identifies the optimal HESS requirements that may present new opportunities ...
All human drivers can be characterised by their habitual choice of driving behaviours, which resu... more All human drivers can be characterised by their habitual choice of driving behaviours, which results in a wide range of observed driving patterns and manoeuvres. Developing control strategies for autonomous vehicles that address this feature would increase the public acceptance of such vehicles. Therefore, this paper proposes a novel approach to developing rule-based fuzzy logic driver models that simulate different driving styles in the car-following regimes. These driver models were trained with the collected on-road driving data to capture corresponding human drivers’ characteristics. The proposed approach consists of three main components: collecting on-road driving data, developing a vehicle model, and establishing the car-following driver models. Firstly, an instrumented vehicle was used to collect driving data over the same route for three consecutive months. Car-following scenarios during these journeys were extracted, and related data were processed accordingly. Afterwards,...
In regulated two-stage sequential turbocharging systems, a smaller, high pressure (HP), and a lar... more In regulated two-stage sequential turbocharging systems, a smaller, high pressure (HP), and a larger, low pressure (LP), turbocharger are sequentially positioned to recover the energy available in the exhaust gases and deliver acceptable level of boost to the intake of an internal combustion engine. Due to the different sizes of the turbochargers, by-pass valves are placed in the system to control operations. Due to the turbocharging system layout, it is clear that the air pressurized by the LP compressor enters nonuniformly the HP compressor. This is caused by the rotating radial compressor and the interconnecting bends which cause swirl and velocity to scatter, respectively. Furthermore, the heat transfer in the two turbochargers may have an effect on the apparent efficiencies. For these reasons, the standard mapping approach for turbochargers is not able to take into account the effect of non-uniform flow and heat transfer. In this paper, a novel approach for mapping the two-stage turbocharging system is proposed and performed into a monodimensional simulation code. Although, flow non-uniformity and turbochargers heat transfer effects on the performance of the turbocharging system are not considered, at this present time, the study centralizes on the investigation and the validation of the mapping approach. In fact, a two-stage sequential turbocharging system has been considered for the study and a simulation code to investigate the mapping technique has been implemented.
Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissio... more Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissions standards. However, their range of operation is limited for low mass flows by compressor surge. Operation in surge results in pressure and mass flow oscillations that are often damaging to the compressor and its installation. Since surge is a highly complex flow regime, full unsteady 3D models are generally too computationally expensive to run. The majority of current low-dimensional surge models use a cubic compressor characteristic that needs to be fitted to experimental data. Therefore, each time a compressor is studied using these models, costly experimental testing is required. In this paper, a new technique for obtaining an axisymmetric centrifugal compressor characteristic is presented. This characteristic is built using the equations of mass, momentum and energy from first principles in order to provide a more complete model than those currently obtained via experimental data. This approach enables us to explain the resulting cubic-like shape of the characteristic and hence to identify impeller inlet stall as a route into surge. The characteristic is used within a quasi-steady, map-based surge model in order to demonstrate its ability to predict the onset of surge while only providing geometric data as input. Validation is provided for this model by discussion of the qualitative flow dynamics and a good fit to experimental data, especially for low impeller speeds and pressure ratios.
Current trend on engine downsizing forces engine manufacturers to contemplate powertrains with mo... more Current trend on engine downsizing forces engine manufacturers to contemplate powertrains with more than one boosting device. The presence of these devices leads to complex 1-D engine models which rely on performance maps provided by turbo/supercharger manufacturers. So far, no detailed analysis has been carried out to understand how these maps affect engine performance simulation. As part of the UltraBoost project (65% gasoline engine downsizing), Imperial College tested the boosting components of a turbo-super configuration. The acquired data were used to assess the effectiveness of 1-D engine performance prediction and to contemplate the opportunity to exploit the boosting system and use it as engine charge air cooler in the form of an expander.
Journal of engineering for gas turbines and power, Feb 23, 2017
For an internal combustion engine, a large quantity of fuel energy (accounting for approximately ... more For an internal combustion engine, a large quantity of fuel energy (accounting for approximately 30% of the total combustion energy) is expelled through the exhaust without being converted into useful work. Various technologies including turbocompounding and the pressurized Brayton bottoming cycle have been developed to recover the exhaust heat and thus reduce the fuel consumption and CO2 emission. However, the application of these approaches in small automotive power plants has been relatively less explored because of the inherent difficulties, such as the detrimental backpressure and higher complexity imposed by the additional devices. Therefore, research has been conducted, in which modifications were made to the traditional arrangement aiming to minimize the weaknesses. The turbocharger of the baseline series turbocompounding was eliminated from the system so that the power turbine became the only heat recovery device on the exhaust side of the engine, and operated at a higher expansion ratio. The compressor was separated from the turbine shaft and mechanically connected to the engine via continuous variable transmission (CVT). According to the results, the backpressure of the novel system is significantly reduced comparing with the series turbocompounding model. The power output at lower engine speed was also promoted. For the pressurized Brayton bottoming cycle, rather than transferring the thermal energy from the exhaust to the working fluid, the exhaust gas was directly utilized as the working medium and was simply cooled by ambient coolant before the compressor. This arrangement, which is known as the inverted Brayton cycle (IBC) was simpler to implement. Besides, it allowed the exhaust gasses to be expanded below the ambient pressure. Thereby, the primary cycle was less compromised by the bottoming cycle. The potential of recovering energy from the exhaust was increased as well. This paper analyzed and optimized the parameters (including CVT ratio, turbine and compressor speed and the inlet pressure to the bottoming cycle) that are sensitive to the performance of the small vehicle engine equipped with inverted Brayton cycle and novel turbocompounding system, respectively. The performance evaluation was given in terms of brake power output and specific fuel consumption. Two working conditions, full and partial load (10 and 2 bar brake mean effective pressure (BMEP)) were investigated. Evaluation of the transient performance was also carried out. Simulated results of these two designs were compared with each other as well as the performance from the corresponding baseline models. The system models in this paper were built in GT-Power which is a one dimension (1D) engine simulation code. All the waste heat recovery systems were combined with a 2.0 L gasoline engine.
Dynamic modelling of engine emissions is important because it promises significant improvements o... more Dynamic modelling of engine emissions is important because it promises significant improvements over static modelling for engine calibration through reduced testing and development times. Volterra series and neural network dynamic model structures were trained using transient data from an engine test stand under sinusoidal excitations and the predictive power over the New European Drive Cycle (NEDC) cycle was assessed for a EURO IV specification Diesel engine. Models were identified for oxides of nitrogen (NOx) and carbon dioxide (CO2) emissions concentrations based on engine speed, torque, injection timing, EGR rate and fuel injection pressure. The fit R 2 values for CO2 emissions for Volterra series and Neural networks were 0.92 and 0.99 respectively; for NOx emissions these were 0.92and 0.998. Although this suggests better flexibility from the Neural network to represent the nonlinearity there were large variations in predictive power resulting from the partially random nature of...
Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissio... more Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissions standards. However, their range of operation is limited for low mass flows by compressor surge. Operation in surge results in pressure and mass flow oscillations that are often damaging to the compressor and its installation. Since surge is a highly complex flow regime, full unsteady three-dimensional models are generally too computationally expensive to run. The majority of current low-dimensional surge models use a cubic compressor characteristic that needs to be fitted to experimental data. Therefore, each time a compressor is studied using these models, costly experimental testing is required. In this paper, a new technique for obtaining an axisymmetric centrifugal compressor characteristic is presented. This characteristic is built using the equations of mass, momentum, and energy from first principles in order to provide a more complete model than those currently obtained via ex...
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