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A novel method of analyzing and controlling hybrid systems has been developed. Utilizing engine operating maps along with hybrid electrical system efficiency data, the actual cost or savings of fuel related to the generation or usage of electric energy can be calculated. These calculations can be used to analyze a vehicle’s operation, or they can produce optimized Electric Fuel Savings (EFS) or Electric Fuel Cost (EFC) maps which can be used for the supervisory control of a hybrid propulsion system. This method is similar in concept to the well-known Equivalent Consumption Minimization Strategy (ECMS) but has some unique attributes. The operating strategy is less computationally demanding than ECMS and tends to be more intuitive which lends itself well to system analysis and calibration.

This paper proposes a real-time capable augmented control scheme for a parallel evaporator organic Rankine cycle (ORC) waste heat recovery system for a heavy-duty diesel engine, which ensures efficient and safe ORC system operation. Assuming a time constant separation between the thermal and pressure dynamics, a nonlinear model predictive control (NMPC) is designed to regulate the mixed working fluid (WF) outlet temperature and the differential temperature between the two parallel evaporator outlets. Meanwhile, the evaporator pressure is regulated by an external PID control. The NMPC is designed using a reduced order, moving boundary control model of the heat exchanger system. In the NMPC formulation, state feedback is constructed from the estimated state via an unscented Kalman filter based on temperature measurements of the exhaust gas and WF at the evaporator outlet. The performance of the proposed control scheme is demonstrated in simulation over an experimentally validated, high fidelity, and physics-based ORC plant model during a transient constant speed and variable load engine drive cycle. The performance of the proposed control scheme (NMPC plus PID) is further validated via comparison with a conventional, multiple-loop PID controlling both the mixed evaporator outlet WF temperature, and the evaporator pressure. The simulation results demonstrate that the proposed control scheme outperforms a multiple-loop PID control in terms of both safety and total recovered thermal energy by up to 12% and 9%, respectively.

Organic Rankine Cycle (ORC) waste heat recovery systems offer promising engine fuel economy improvements for heavy-duty on-highway trucks. An ORC test rig with parallel evaporators to recover both tailpipe and EGR waste heat from a 13L heavy duty diesel engine was developed and used in this work to demonstrate a novel control strategy based on Model-Predictive Control (MPC). The main control objectives for the ORC system are: (i) regulation of working fluid temperature, (ii) safe turbine operation - away from 2-phase region, and (iii) maximization of waste heat recovery. The MPC uses a built-in moving boundary evaporator model to predict future system response and generate optimal actuator reference commands. Two variants of MPC were considered in this work: an adaptive linear MPC (LMPC) and a nonlinear MPC (NPMC). Compared with the traditionally used PID controller, MPC demonstrates more accurate temperature control and improved disturbance rejection in simulation. Finally, the LMPC and NMPC controllers were implemented on the ORC test rig and showing promising initial test results.

The flow field at the inlet of a turbocharger compressor has been studied through stereoscopic particle image velocimetry (SPIV) experiments under different operating conditions. It is found that the flow field is quite uniform at high mass flow rates; but as the mass flow rate is reduced, flow reversal from the impeller is observed as an annular ring at the periphery of the inlet duct. The inception of flow reversal is observed to occur in the mid-flow operating region, near peak efficiency, and corresponds to an incidence angle of about 15.5 deg at the inducer blade tips at all tested speeds. This reversed flow region is marked with high tangential velocity and rapid fluctuations. It grows in strength with reducing mass flow rate and imparts some of its angular momentum to the forward flow due to mixing. The penetration depth of the reversed flow upstream from the inducer plane is found to increase quadratically with decreasing flow rate.

Understanding the velocity field at the inlet of an automotive turbocharger is critical in order to suppress the instabilities encountered by the compressor, extend its map and improve the impeller design. In the present study, two-dimensional particle image velocimetry experiments are carried out on a turbocharger compressor without any recirculating channel to investigate the planar flow structures on a cross-sectional plane right in front of the inducer at a rotational speed of 80 krpm. The objective of the study is to investigate the flow field in front of a compressor blade passage and quantify the velocity distributions along the blade span for different mass flow rates ranging from choke (77 g/s) to deep surge (13.6 g/s). It is observed that the flow field does not change substantially from choke to about 55 g/s, where flow reversal is known to start at this speed from earlier measurements. While the tangential velocity is less than 8 m/s, the radial velocity increases along the span to 17–20 m/s near the tip at high flow rates (55–77 g/s). As the mass flow rate is reduced below 55 g/s, the radial component starts decreasing and the tangential velocity increases rapidly. From about 5 m/s at 55 g/s, the tangential velocity at the blade tip exceeds 50 m/s at 50 g/s and reaches a maximum of about 135 m/s near surge. These time-averaged distributions are similar for different angular locations in front of the blade passage and do not exhibit any substantial azimuthal variation.

The effect of inlet guide vanes (IGVs) on the acoustic and performance characteristics of an automotive centrifugal compressor is studied on a steady-flow turbocharger experimental facility. Broadband noise accompanying flow separation occurs as the flow rate of the compressor is reduced and the incidence angle of the flow relative to the leading edge of the inducer blades increases. The addition of IGVs upstream of the inducer imparts a tangential (swirl) velocity component in the same direction of impeller rotation, which improves the incidence angle particularly at low to mid-flow rates. In the present study, experimental data is compared for three compressor inlet geometries, including a no-swirl baseline along with two different IGV configurations. IGVs were shown to slightly improve the surge line at the highest rotational speed considered in this study, while compromising the maximum flow rate at all rotational speeds. In the high-flow range, IGVs are observed to increase compressor inlet noise levels over a wide frequency range. At the more common low to mid-flow range, however, broadband whoosh noise is reduced with the addition of IGVs in the 5-12 kHz band.

This paper discusses the control challenges of a parallel evaporator organic Rankine cycle (ORC) waste heat recovery (WHR) system for a diesel engine. A nonlinear model predictive control (NMPC) is proposed to regulate the mixed working fluid outlet temperature of both evaporators, ensuring efficient and safe ORC system operation. The NMPC is designed using a reduced order control model of the moving boundary heat exchanger system. In the NMPC formulation, the temperature difference between evaporator outlets is penalized so that the mixed temperature can be controlled smoothly without exceeding maximum or minimum working fluid temperature limits in either evaporator. The NMPC performance is demonstrated in simulation over an experimentally validated, high fidelity, physics based ORC plant model. NMPC performance is further validated through comparison with a classical PID control for selected high load and low load engine operating conditions. Compared to PID control, NMPC provides significantly improved performance in terms of control response time, overshoot, and temperature regulation.

This paper presents steady state power optimization for an Organic Rankine Cycle (ORC) waste heat recovery (WHR) system in heavy-duty diesel (HDD) applications and examines attainable power levels. Both recirculated and tail pipe exhaust gas streams are utilized as heat sources via a parallel evaporator configuration. A dynamic, physics-based ORC model is utilized to determine optimized net power production. The optimization variables include: working fluid pump speed, mass flow distribution ratio for the parallel evaporators, turbine speed, and the pump speed of condenser cooling fluid. A sensitivity analysis is conducted for all optimization variables. Working fluid pump speed and expansion turbine speed are demonstrated as the most sensitive variables. Sensitivity results indicate increasing system power production as the working fluid mass flow rate increases. A map is developed to identify optimal and safe ORC operating regions for a given engine cycle. Based on the sensitivity analysis working fluid pump speed is selected as the variable of interest in the steady state optimization and results indicate that system power generation could be improved by as much as 25%. Analysis of two quasi steady operational cycles, a multi-mode and a constant speed variable load are conducted. ORC power results indicate that a speed-constrained, mechanically coupled turbine expander operates in its peak efficiency zone to produce maximum power output for the steady-state cycles tested. These steady state power optimization results can be used for future power optimization during engine transients.

The significant growth forecasted in gasoline boosted engines and the more challenging regulatory requirements for emissions and fuel economy are leading to an aggressive engine downsizing trend. Two technology leaders have partnered in order to offer an optimized design in dual boosting systems which combine superchargers and turbochargers. The result is an air delivery boosting system that can accommodate high BMEP at all engine speeds without compromising transient response. Combining the skills of both companies, the advanced engineering groups joined efforts to perform an extensive simulation study over the course of a year aimed at defining a superior system design methodology. This study explored and analyzed the benefits of each boosting device. Two main configurations were considered based on the relative sequence of each device in the air path, namely: supercharger (SC) + turbocharger (TC) and TC + SC.

Vehicle thermal management faces increased importance since a higher efficiency of ICE powered vehicles is requested. The fuel consumption benefits from thermal management is linked to two areas: By using the coolant pump and fan according to the real demand and improving their efficiency the auxiliary losses can be reduced and secondly: by operating the engine in an optimal temperature range regarding friction and combustion the overall powertrain efficiency can be increased. At cold start, the fast warm up of the engine and the transmission is important. During normal operation, the cooling system has to keep the engine in a temperature range that friction is minimized, protect the engine from overheating and create minimum auxiliary losses.