Electric Turbocompound System Research Articles

Development of a novel dual-loop optimization method for the engine electric turbocompound system based on particle swarm algorithm

Electric turbocompounding (ETC) plays a key role in fuel saving and emission reduction of internal combustion engines. In this paper, a novel dual-loop optimization method is proposed to rapidly obtain highest turbine efficiency and lowest engine BSFC. Firstly, turbine model and the engine cycle model are established and coupled in MATLAB. The predicted engine torque and BSFC are 4.48 % and 5.05 % deviated from the experimental data. The deviations of turbine swallowing capacity and efficiency are within 1 % and 2 %, respectively. Then, particle swarm optimization (PSO) is used to seek for the optimal ETC expansion/pressure ratio in the outer loop and the optimal turbine geometric parameters in the inner loop. It is shown that 3–4 particles are enough to obtain a good solution for the 2-D ETC system optimization and at least 25 particles are required for the 6-D turbine optimization. At last, case studies are carried out to analyze the impacts of ETC mechanical efficiency and back pressure. It is shown that 5 % higher of ETC mechanical efficiency results in 30 % increase in electric power and 10 kPa higher back pressure leads to 18.1 % lower in electric power. The optimized turbine can obtain efficiency higher than 78 % in all cases.

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

As is widely known, internal combustion engines are not able to complete the expansion process of the gas inside the cylinder, causing theoretical energy losses in the order of 20%. Several systems and methods have been proposed and implemented to recover the unexpanded gas energy, such as turbocharging, which partially exploits this energy to compress the fresh intake charge, or turbo-mechanical and turbo-electrical compounding, where the amount of unexpanded gas energy not used by the compressor is dedicated to propulsion or is transformed into electric energy. In all of these cases, however, maximum efficiency improvements between 4% and 9% have been achieved. In this work, the authors deal with an alternative propulsion system composed of a CNG-fueled spark ignition engine equipped with a turbine-generator specifically dedicated to unexpanded exhaust gas energy recovery and with a separated electrically driven turbocompressor. The system was conceived specifically for hybrid propulsion architectures, with the electric energy produced by the turbine generator being easily storable in the on-board energy storage system and re-usable for vehicle traction. The proposed separated electric turbo-compound system has not been studied in the scientific literature, nor have its benefits ever been analyzed. In this paper, the performances of the analyzed turbo-compound system are evaluated and compared with a traditional reference turbocharged engine from a hybrid application perspective. It is demonstrated that separated electric compounding has great potential, with promising overall efficiency advantages: fuel consumption reductions of up to 15% are estimated for the same power output level.

Mechanical and Electromagnetic Analysis of High Speed Motor/Generator for Electric Turbo Compounding System

Background: Recently, environment friendly technologies are being introduced as global warming is rapidly progressing. One of the effective way to reduce the problem, Electric Turbo Compounding System has been researched globally. With this system, about 30% exhaust gas can be recycled as a power source. Therefore, this system is effective for engine systems with purposes such as downsizing and increasing efficiency of the system. Objective & Method: Surface mounted Permanent Magnet Motor is applied to this system due to its high efficiency, power density, small size, and low weight. However, during high speed operation, a retaining sleeve is essential in rotor such as Inconel 718 to satisfy a mechanical safety factor of the rotor. In this paper, through basic theory, the sleeve thickness is predicted according to the permanent magnet dimension and minimum sleeve thickness is determined satisfying mechanical safety factor by mechanical analysis. Furthermore, by electromagnetic analysis output characteristics according to the permanent magnet dimension having same constraints such as volume, current density, current and flux distribution are compared. Result & Conclusion: Based on the results of the electromagnetic analysis and mechanical analysis, the appropriate ratio of electric and magnetic loading is determined with equivalent constraint condition. Consequently, only model 2 satisfies the requirement at rated and maximum speed within the current limit.

Exergy Analysis of Organic Rankine Cycle and Electric Turbo Compounding for Waste Heat Recovery

With such tough legislation on current emission standards, car manufacturers are focusing on increasing the efficiency of their engines with the development of advance waste heat recover (WHR) technology. Organic Rankine Cycle (ORC) and Electric Turbo Compounding (ETC) system have a good potential to be used as exhaust energy recovery. This paper compares the exergy availability and losses between the ORC and the ETC. In this particular study, exhaust data from the Proton 1.6L CamPro CFE turbocharged engine was used. This particular engine already has a main turbocharger, making the added WHR as a secondary recovery system to further increase the engine efficiency. Both systems are coupled to a 1 kW electric generator for ease of comparisons. At first the available exergy is calculated for both WHR technologies. Exergy losses from rotating the generator are analysed to finally determine the thermal efficiency of the overall system. Exergy calculation is simplified to only account for chemical and physical exergy since kinetic and potential energy are negligible in comparison. Available exergy for ORC was significantly high which went up to 12.5 kW with the exergy losses recorded at 9.7 kW. The ETC achieved only 5 kW but had a small loss at 8x10-3 kW. Average thermal efficiency of the ORC systems was 10.7% compared to ETC which was 58.7%. It can be concluded that the complexity of the ORC system contributes to its downfall where multiple components increase its exergy losses compared to the simplistic design of an ETC.

Evaluation of an electric turbo compound system for SI engines: A numerical approach

In a medium term scenario hybrid powertrain and Internal Combustion Engine (ICE) downsizing represent the actual trend in vehicle technology to reduce fuel consumption and CO2 emission. Concerning downsizing concept, to maintain a reasonable power level in small engines, the application of turbocharging is mandatory both for spark ignited (SI) and compression ignited (CI) engines. Following this aspect, the possibility to couple an electric drive to the turbocharger (electric turbo compound) to recover the residual energy of the exhaust gases is becoming more and more attractive, as demonstrated by several studies around the world and by the current application in the F1 Championship.The present paper shows the first numerical results of a research program in collaboration between the Universities of Pisa and Genoa. This first study is focused on the evaluation of the benefits resulting from the application of an ETC (Electric Turbo Compound) to a small twin-cylinder SI engine (900cm3). Starting from the experimental maps of two turbines and one compressor, the complete model of a turbocharged engine was created using the AVL BOOST one-dimension code. The numerical activity then moves to the whole vehicle/powertrain modelling, considering three driving cycles and two different vehicle configurations, in order to verify the effectiveness of the proposed ETC solution.Results show that the adoption of ETC is not advantageous if used for a conventional turbocharger turbine, if the target is to optimize the overall efficiency in one specific operating point of the ICE, like in the case of range-extended electric vehicles. Besides, ETC can slightly improve the average overall efficiency when the ICE must provide variable power output, as in the case of conventional or hybrid vehicles. However, the major benefits coming from ETC are the boost range extension in the lowest engine rotational speed region and a possible reduction of turbo lag, which are key points in parallel-hybrid and especially in conventional vehicles.Concerning the whole vehicle/powertrain simulation, first results show that the ETC does not improve fuel economy of the smaller vehicle, especially when employed in urban cycles. The ETC is much more advantageous in the case of the larger vehicle, particularly when extra-urban roads or motorways are considered.

Simulation Study on Electric Turbo-Compound (ETC) for Thermal Energy Recovery in Turbocharged Internal Combustion Engine

Exhaust gas heat utilization in the form of Thermal Energy Recovery (TER) has attracted a major interest due to its potentials with Internal Combustion Engines (ICE). Recovering useful energy, for example in the form of electrical power from the engine exhaust waste heat could benefit in the form of direct fuel economy or increase in the available electric power for the auxillary systems. The methodology in this paper includes the assessment of each waste heat recovery technology based on the current research and development trends for automotive application. It also looked into the potential for energy recovery, performances of each technology and factors affecting its implementation. Finally, the work presents an Electric Turbo Compounding (ETC) simulation using a Ford Eco-Boost as a baseline engine modeled with the 1-Dimensional AVL Boost software. A validated 1-D engine model was used to investigate the impact on the Brake Specific Fuel Consumption (BSFC) and Brake Mean Effective Pressure (BMEP) at full load. This paper presents some reviews on the turbo-compounding method and also the modelling efforts and results of an electric turbo-compounding system. Modelling shows that the turbo-compounding setup can be more beneficial than turbo-charging alone.

Heavy-duty engine electric turbocompounding

This paper analyses the performance of a heavy-duty engine when integrating a turbocompound system including a low-pressure-ratio turbine. The main feature of the low-pressure-ratio turbine is that of achieving efficiencies greater than 75% at very low pressure ratios (of approximately 1.1). The engine performance is predicted by a one-dimensionanl simulation model of a 10 l heavy-duty engine. An electric turbocompound system with a low-pressure-ratio turbine is fitted downstream of the main turbocharger to extract the exhaust gas energy. This additional energy supplies the electronic units and batteries. A method to scale an existing low-pressure-ratio turbine, designed for a 1.0 l gasoline engine, is defined and the changes in the turbine losses and the blade stresses are discussed. Low-pressure-ratio turbines of different sizes are analysed and compared in order to obtain the greatest benefit. In all cases the sum of the engine power and the turbocompound power is matched to the baseline engine power output. The full-load results show a power output from the low-pressure-ratio turbine of up to 15.8 kW, an improvement in the brake specific fuel consumption of the engine of up to 4% and a reduction in the brake mean effective pressure of up to 5%. The recovered exhaust gas energy is higher than the engine power required to balance the increased back pressure due to the additional component within the exhaust system. The electrical power produced is sufficiently high to replace the alternator.

Simulation of a heavy-duty diesel engine with electrical turbocompounding system using operating charts for turbocharger components and power turbine

In diesel engines, approximately 30–40% of the energy supplied by the fuel is rejected to the ambience through exhaust gases. Therefore, there is a potentiality for further considerable increase of diesel engine efficiency with the utilization of exhaust gas heat and its conversion to mechanical or electrical energy. In the present study, the operational behavior of a heavy-duty (HD) diesel truck engine equipped with an electric turbocompounding system is examined on a theoretical basis. The electrical turbocompounding configuration comprised of a power turbine coupled to an electric generator, which is installed downstream to the turbocharger (T/C) turbine. A diesel engine simulation model has been developed using operating charts for both turbocharger and power turbine. A method for introducing the operating charts into the engine model is described thoroughly. A parametric analysis is conducted with the developed simulation tool, where the varying parameter is the rotational speed of power turbine shaft. In this study, the interaction between the power turbine and the turbocharged diesel engine is examined in detail. The effect of power turbine speed on T/C components efficiencies, power turbine efficiency, exhaust pressure and temperature, engine boost pressure and air to fuel ratio is evaluated. In addition, theoretical results for the potential impact of electrical turbocompounding on the generated electric power, net engine power and relative improvement of brake specific fuel consumption (bsfc) are provided. The critical evaluation of the theoretical findings led to the basic conclusion that there is a significant potential for bsfc improvement of HD diesel truck engines with the proposed electrical turbocompounding concept, which reaches up to 4% at full engine load. The improvement of bsfc with electric turbocompounding appears to be more attractive solution in terms of technical complexity and installation cost against other competitive heat recovery technologies such as Rankine cycle systems.