Efficiency Advantages of the Separated Electric Compound Propulsion System for CNG Hybrid Vehicles

Pipitone, Emiliano; Caltabellotta, Salvatore

doi:10.3390/en14248481

Cited by 5 publications

(11 citation statements)

References 30 publications

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“…Considering the isentropic transformation, the static pressure at nozzle outlet was evaluated as: (13) where the isentropic enthalpy drop is obtained as the sum of the actual enthalpy drop (Equation ( 12)) and the volute loss (Equation ( 7)):…”

Section: Analysis Of the Volutementioning

confidence: 99%

“…Moreover, since the rotational speed of the turbine is independent from the engine and from the compressor, it can be optimally controlled and set to the best value acting through the connected generator. In their preliminary studies [13,14], the authors demonstrated that this system is very promising, as it may achieve overall vehicle efficiency advantages up to 15% with respect to a reference hybrid propulsion system of the same nominal overall output power (73.5 kW) equipped with a traditional turbocharged engine. Furthermore, the authors showed that the contribution of the turbogenerator may reach an impressive 33.9% share of the total power generated by the whole system, with maximum power delivered of 20 kW; in this regard, it must be pointed out that in their previous works, the exhaust gas turbine considered was supposed to be optimized for steady-state operation, since in a hybrid propulsion system the thermal engine undergoes small speed and load variations.…”

Section: Introductionmentioning

confidence: 99%

“…These values are substantially higher than the efficiency of a common turbocharging turbine on account of the more favourable working condition already mentioned, which allows a design strategy aimed at maximizing the efficiency in steady operation, and also permits the control module of the electric generator to operate the turbine at its best efficiency speed ratio, regardless of the power produced. It is also worth noting that in the preliminary evaluations performed [13,14], the efficiency of the electric motor (0.90) employed to drive the supercharger was considered in the evaluation of the power drained by the compressor, since it constitutes an ancillary device, which burdens the overall energy balance of the engine; instead, concerning the turbine, the efficiencies of the electric generator and of the battery charging were not considered coherently with the approach followed for the main thermal engine, whose power output was not reduced by generator efficiency or by battery-charging efficiency; the reason for this approach is that the engine power split (i.e., part to the generator and part to the wheels) should depend on the particular mechanical transmission adopted and was not defined in the evaluation carried out. Moreover, both the generator and the battery-charging efficiency can also be considered the same for the comparative hybrid propulsion system equipped with the traditional turbocharged engine; on account of this, the authors decided to fairly base the comparison on the overall mechanical output power produced.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, the authors focused on radial turbines instead of multistage axial turbines with a view to a good compromise between efficiency and overall machine size [18][19][20]. As the first step, the authors evaluated the Mass Flow Parameter (MFP) that resulted in one of the preliminary studies [13], in order to identify the most suitable kind of turbine to employ in this application.…”

Section: Introductionmentioning

confidence: 99%

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Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 1: Radial Turbine Modelling and Design

et al. 2023

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The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the energy of the exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered by means of a properly designed turbogenerator and employed for vehicle propulsion; previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% by employing a 20 kW turbine on a 100 HP rated power thermal unit. The innovative thermal unit here proposed is composed of a supercharged engine endowed with a properly designed turbogenerator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In these two parts, the realistic efficiency of the innovative thermal unit for hybrid vehicle is evaluated and compared to a traditional turbocharged engine. In Part 1, the authors present a model for the prediction of the efficiency of a dedicated radial turbine, based on a simple but effective mean-line approach; the same paper also reports a design algorithm, which, owing to some assumptions and approximations, allows a fast determination of the proper turbine geometry for a given design operating condition. It is worth pointing out that, being optimized for quasi-steady power production, the exhaust gas turbine considered is quite different from the ones commonly employed for turbocharging application; for this reason, and in consideration of the required power size, such a turbine is not available on the market, nor has its development been previously carried out in the scientific literature. In the Part 2 paper, a radial turbine geometry is defined for the thermal unit previously calculated, employing the design algorithm described in Part 1; the realistic energetic advantage that could be achieved by the implementation of the turbogenerator on a hybrid propulsion system is evaluated through the performance prediction model under the different operating conditions of the thermal unit. As an overall result, it was estimated that, compared to a reference traditional turbocharged engine, the turbocompound system could gain vehicle efficiency improvement between 3.1% and 17.9%, depending on the output power level, while an average efficiency increment of 10.9% was determined for the whole operating range.

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Section: Analysis Of the Volutementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 1: Radial Turbine Modelling and Design

et al. 2023

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“…These values are higher than the efficiency of turbines commonly used for turbocharging, on account of the more favorable working condition already mentioned, which allows a design strategy for the best efficiency under steady operation, and also permits the electric generator to control the turbine speed of rotation, maximizing its efficiency, apart from the power produced. Some preliminary evaluations made by the same authors [2][3][4] showed that the separated electric compound engine has good potential, since vehicle fuel economy increments up to 15% may be obtained in comparison to a reference hybrid propulsion system endowed with a traditional turbocharged engine with equal maximum output power (73.5 kW). It was also found that the turbo-generator could contribute to vehicle traction by about 34% of the overall power generated for the propulsion, with a maximum delivered power of about 20 kW.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 2: Numerical Simulation Results

et al. 2023

Self Cite

View full text Add to dashboard Cite

The efficiency of hybrid electric vehicles may be substantially increased if the energy of exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered using a properly designed turbo-generator and employed for vehicle propulsion. Previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% employing a 20 kW turbine on a 100 HP-rated power thermal unit. The innovative thermal unit proposed here is composed of a supercharged engine endowed with a properly designed turbo-generator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In this two-part work, the realistic efficiency of the innovative thermal unit for hybrid vehicles is evaluated and compared to a traditional turbocharged engine. In Part 1, the authors presented a model for the prediction of the efficiency of a dedicated radial turbine, based on a simple but effective mean-line approach; the same paper also reports a design algorithm, which, thanks to some assumptions and approximations, allows fast determination of the right turbine geometry for a given design operating condition. It is worth pointing out that, being optimized for quasi-steady power production, the exhaust gas turbine here considered is quite different from the ones commonly employed for turbocharging applications; for this reason, and in consideration of the required power size, such a turbine is not available on the market, nor has its development been previously carried out in the scientific literature. In this paper, Part 2, a radial turbine geometry is defined for the thermal unit previously calculated, employing the design algorithm described in Part 1; the realistic energetic advantages that could be achieved by the implementation of the turbo-generator on a hybrid propulsion system are evaluated through the performance prediction model under different operating conditions of the thermal unit. As an overall result, it was estimated that, compared to a reference traditional turbocharged engine, the turbo-compound system could gain vehicle efficiency improvement between 3.1% and 17.9%, according to the output power delivered, with an average efficiency increment of 10.9% evaluated on the whole operating range.

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Review of Methods for Improving the Energy Efficiency of Electrified Ground Transport by Optimizing Battery Consumption

et al. 2023

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The article reviews the existing methods of increasing the energy efficiency of electric transport by analyzing and studying the methods of increasing the energy storage resource. It is grouped according to methods, approaches, and solutions. The most effective methods and ways of their implementation are identified. General methods of increasing energy efficiency, methods of increasing recuperation during braking, methods of energy-efficient energy consumption, the use of energy-saving technologies, and improving the energy efficiency of the traction drive are considered. The purpose of this work is to identify the main operating factors on the basis of a critical review of existing methods for assessing the technical condition of batteries and experimental results on the degradation of lithium-ion batteries. Using the great experience of the research group in the field of modeling, diagnostics, and forecasting of life of electric cars, as well as their intellectual management, the new theoretical and practical methods of integrated assessment of the parameters of the traction battery and state of charge, which are operated in the heavy forced regenerative regimes of electric traction, are created and proposed. A great role is played by the construction of the transport model. The development is based on physical laws that passengers and vehicle owners are unaware of. For each model there is a different area of application, and what is suitable for one object may not be suitable for another. The overview shows that there is no one-size-fits-all way to improve energy efficiency. It is necessary to make a choice among several proposed models after a thorough feasibility study.

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Efficiency Advantages of the Separated Electric Compound Propulsion System for CNG Hybrid Vehicles

Cited by 5 publications

References 30 publications

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 1: Radial Turbine Modelling and Design

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 1: Radial Turbine Modelling and Design

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 2: Numerical Simulation Results

Review of Methods for Improving the Energy Efficiency of Electrified Ground Transport by Optimizing Battery Consumption

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