CONCEPT EVALUATION AND DEVELOPMENT OF A NOVEL APPROACH FOR INTEGRATION OF TURBOGENERATION, ELECTRIFICATION AND SUPERCHARGING ON HEAVY DUTY ENGINES

While many technologies such as electrically assisted turbocharging, exhaust energy recovery and mild hybridization have already proven to significantly increase heavy-duty engine efficiency, the key challenge to their widespread adoption has been their cost effectiveness and packaging. This research specifically addresses these challenges through evaluation and development of a novel technology concept termed as the Integrated Turbogeneration, Electrification and Supercharging (ITES) system. The concept integrates a secondary compressor, a turbocompound/expander turbine and an electric motor through a planetary gearset into the engine cranktrain. The approach enables a reduced system cost and space-claim, while maximizing the efficiency benefits of independent technologies. First, an assessment of design alternatives for integration of the identified key engine technologies on a heavy-duty engine was conducted. Once the ITES concept was down selected, the research then focused on model-based optimization and evaluation of the ITES system for a downsized medium heavy-duty diesel engine applied in Class 6-7 urban vocational application. As an outcome of the evaluation, a 1D simulation based sizing methodology of ITES system components was proposed. Furthermore, a novel control strategy for the ITES system was developed that combines equivalent consumption based steady-state offline optimization with functional controls for transient operation and smooth mode switching. The offline optimization method was also extended to evaluate the potential of ITES system in increasing aftertreatment temperature, which is critical for meeting future ultra-low NOx emission standards. Lastly, using 1D simulation of validated models, the efficiency benefit of ITES system on engine certification and vehicle drive cycles was predicted for the Class 6-7 urban vocational application. In comparison to baseline engine, the downsized engine with ITES system predicted an 8.5% reduction in engine fuel consumption on HDFTP cycle, 19.3% increase in fuel economy on ARB Transient cycle and 23.7% increase in fuel economy on a real-world drive cycle

The study on performance of naturally aspirated spark ignition engine equipped with waste heat recovery mechanism

The waste heat from exhaust gases represents a significant amount of thermal energy, which has conventionally been used for combined heating and power applications. This paper explores the performance of a naturally aspirated spark ignition engine equipped with waste heat recovery mechanism (WHRM). The amount of heat energy from exhaust is presented and the experimental test results suggest that the concept is thermodynamically feasible and could significantly enhance the system performance depending on the load applied to the engine. However, the existing of WHRM affects the performance of engine by slightly reducing the power

Decoupling control of electrified turbocharged diesel engines

Engine electrification is a critical technology in the promotion of engine fuel efficiency, among which the electrified turbocharger is regarded as a promising solution for its advantages in engine downsizing and exhaust gas energy recovery. By installing electrical devices on the turbocharger, the excess energy can be captured, stored, and re-used. The control of the energy flows in an electrified turbocharged diesel engine (ETDE) is still in its infancy. Developing a promising multi-input multi-output (MIMO) control strategy is essential in exploring the maximum benefits of electrified turbocharger. In this paper, the dynamics in an ETDE, especially the couplings among multiple loops in the air path are analyzed. Based on the analysis, a model-based MIMO decoupling control framework is designed to regulate the air path dynamics. The proposed control strategy can achieve fast and accurate tracking on selected control variables and is successfully validated on a physical model in simulations

Real-time energy management of the electric turbocharger based on explicit model predictive control

The electric turbocharger is a promising solution for engine downsizing. It provides great potential for vehicle fuel efficiency improvement. The electric turbocharger makes engines run as hybrid systems so critical challenges are raised in energy management and control. This paper proposes a real-time energy management strategy based on updating and tracking of the optimal exhaust pressure setpoint. Starting from the engine characterisation, the impacts of the electric turbocharger on engine response and exhaust emissions are analysed. A multivariable explicit model predictive controller is designed to regulate the key variables in the engine air system, while the optimal setpoints of those variables are generated by a high level controller. The two-level controller works in a highly efficient way to fulfill the optimal energy management. This strategy has been validated in physical simulations and experimental testing. Excellent tracking performance and sustainable energy management demonstrate the effectiveness of the proposed method

Robust control of electrified turbocharged diesel engines

Electrified turbocharger is a critical technology for engine downsizing and is a cost-effective solution for exhaust gas energy recovery. In conventional turbocharged diesel engines, the air path holds strong nonlinearity since the actuators are all driven by the exhaust gas. In an electrified turbocharged diesel engine (ETDE), the coupling is more complex, due to the electric machine mounted on the turbine shaft impacts the exhaust manifold dynamics as well. In distributed single-input single-output control methods, the gains tuning is time consuming and the couplings are ignored. To control the performance variables independently, developing a promising multi-input multi-output control method for the ETDE is essential. In this paper, a model-based multi variable robust controller is designed to control the performance variables in a systematic way. Both simulation and experimental results verified the effectiveness of the proposed controller

Experimental Analysis and 1D Model Simulation of an Advanced Twin Stage Hybrid Boosting System

Due to the increasingly restrictive limits of pollutant emissions, electrification of automotive engines is now mandatory. For this reason, adopting hybrid boosting systems to improve brake specific fuel consumption and time-to-boost is becoming common practice. In this thesis an innovative turbocharging system is analysed, consisting in an electrically assisted radial compressor and a traditional turbocharger. As a first step, the steady-state performance of each component was measured at the University of Genoa test rig. Due to problems related to over temperature, the working time of the e-compressor coupled to the electric motor is limited avoiding an accurate evaluation of compressor efficiency. For this reason a driving system (instead of the electric machine) was designed to provide a more accurate evaluation of the compressor map. Subsequently another experimental campaign was carried out to evaluate the transient response of the entire turbocharging system. Two different layouts were compared: upstream and downstream. In the upstream configuration the electrically assisted compressor was placed in front of the traditional turbocharger, in the downstream configuration the e-compressor was positioned after the traditional turbocharger. The two different coupling configurations, upstream and downstream, were then modelled in 1-D simulation software following the dimensions and characteristics of the experimental line from which the exploited data originates. The models were first validated by emulating the steady-state condition and subsequently the transient response was simulated and analysed. Secondly, the transient response of the two layouts was compared, removing the constraints imposed by the experimental activity

An integrated framework on characterization, control, and testing of an electrical turbocharger assist

Engine downsizing is a promising trend for improving fuel efficiency of conventional powertrain vehicles. The reduced engine capacity can be compensated by better air delivery through electrically assisted boosting systems, while the most critical technology is the electric turbocharger. In this paper, an integrated framework for characterization, control, and testing of the electric turbocharger is proposed. Starting from a physical characterization of the engine, the impact of the electric turbocharger on fuel economy and exhaust emissions are both analyzed, as well as its controllability. A multi-variable robust controller is designed to regulate the dynamics of the electrified turbocharged engine in a systematic approach. To minimize the fuel consumption in real time, a supervisory level controller is designed to update the setpoints of key controlled variables in an optimal way. Furthermore, a cutting-edge experimental platform of a heavy-duty electrified turbocharged diesel engine is built. The demonstrated excellent tracking performance, high robustness, and improvements on fuel efficiency in experimental results prove the effectiveness of both the developed system and the proposed control strategy