Engine Thermal Management System Research Articles

Modeling and simulating the thermal management system of a hydrogen fuel cell

Abstract Hydrogen energy is an important means of achieving decarbonization goals. Hydrogen fuel cells have broad application prospects due to their high-power output and wide temperature range. To improve the heat dissipation capacity of the fuel cell thermal management system, this paper establishes a simulation model of a 60kw fuel cell. The performance of the fuel cell engine thermal management system model under optimal operating parameters is studied by taking the temperature of the inlet and outlet water of the stack as the observation value. This is significant in improving the thermal environment of the fuel cell engine and ensuring its safe and efficient operation.

An advanced control strategy for engine thermal management systems with large pure time delay

Stable and precise temperature control can effectively improve the engine’s fuel consumption and emissions. An advanced engine thermal management system (AETMS) composed of electric actuators has great potential in increasing the temperature tracking control accuracy and decreasing the system energy consumption. Time-varying disturbance and pure time delay in the system make it challenging to harmoniously control multiple actuators to ensure efficient temperature tracking performance. In addition, a reasonable power distribution of the actuators is beneficial to reduce the parasitic energy consumption of the system and further improve the system efficiency. In this article, an adaptive optimization control strategy consisting of a state predictor, a disturbance estimator, an energy consumption optimization block and a state tracking controller is proposed for the temperature tracking and energy consumption optimization of AETMS. Experimental verification was performed on a range extender bench of an extended-range electric vehicle, and the results show that the system achieves high-precision temperature control and energy consumption near the theoretical optimal value under changing working conditions. The temperature steady-state error is within 0.3 oC, and the temperature adjustment time is within 100 s after the first overshoot.

Multi-Disciplinary Analysis of Working Fluids on Thermal Performance of the High-Power Diesel Engine System

Multi-disciplinary analysis was performed to analyze and investigate the thermal performance during transient operation of a 2 L diesel engine system with two different cooling systems. The multi-disciplinary model consisted of the engine thermal management system (ETMS) comprising a zero-dimensional engine model that can simulate the engine performance, and a one-dimensional flow model for cooling and lubrication systems with a controller. By deploying this approach, we were able to model different physical domains, including mechanical for the engine and the dynamometer and thermodynamic for the heat exchangers. Therefore, the thermal performance of the ETMS could be numerically predicted and analyzed. To develop the ETMS model, the physical properties, the heat transfer model, and the pressure drop were modeled. The base fluid, a 50/50 mixture of water and ethylene glycol (EG), and an Al2O3 nanofluid with a 1.5% volume ratio were modeled based on the thermodynamic properties such as density, dynamic viscosity, thermal conductivity, and specific heat. Nanofluid, with its higher thermal conductivity and higher heat transfer coefficient, absorbed more heat from the combustion chamber through the water-jacket in the engine block. Therefore, the oil temperature for the nanofluid was effectively 2.5 °C less than for the base fluid following the step-load condition. Simulation results showed the better effect of nanofluid on thermal performance. The total flow rate of nanofluid decreased by 2.2 L/min, although the flow rate through the radiator with nanofluid increased by 0.81 L/min to obtain greater heat dissipation. Eventually, the piston and the liner temperatures with the nanofluid were drastically reduced by 7.55 and 8 °C, respectively, compared to those of the base fluid. Finally, when nanofluids was applied in automotive cooling systems, the temperature of the piston decreased by 7.3 °C due to the reduced overall thermal resistance from combustion chambers to outside air. The effect of working fluid on the diesel engine system could be predicted through the multi-disciplinary model.

Numerical and experimental analysis of rounded fins for high speed air-cooled heat exchangers

The implementation of Surface Air-Cooled Oil Coolers (SACOCs) in new generation of turbofans is becoming more and more common. The main reason behind this is the need of improving the engine thermal management system as lubricants and components are working under increasingly severe demands. The idea of using the cold air from the bypass duct as a cold sink not only can be beneficial to cool down the oil, but because the enthalpy can be released into this flow to enhance the propulsion. However, it is extremely important to maintain the aerodynamic impact of the heat exchanger to its minimum so the propulsive efficiency is not worsened.In this investigation, the effect of rounding the sharp edges of a finned heat exchanger working under realistic conditions of very high Reynolds numbers is addressed. Firstly, a parametric study to determine the blend radius was numerically conducted and then, both geometries were experimentally tested for different Reynolds. The rounded version presented not only better results in terms of heat exchange, but also a considerable reduction in the aerodynamic impact of the fins. A detailed numerical analysis of both cases under nominal conditions showed that rounding the sharp edges enables the airflow to remain better attached to the fins, decreasing thus the aerodynamic impact in terms of velocities and vorticity and improving the thermal performances.

Computing Complexity Reduction for Predictive Control of Engine Thermal Management System

<div class="section abstract"><div class="htmlview paragraph">This paper presents the design, implementation, and performance evaluation of a reduced complexity algorithm for a predictive control which is based on our previously published SAE paper (2021-01-0225) titled, “Model Predictive Control for Engine Thermal Management System.” That paper presented a model predictive control (MPC) design concept and demonstrated energy efficiency improvements by enabling engine pre-cooling based on GPS/Navigation data to recognize future vehicle speed limit and road grade in anticipation of high engine load demand.</div><div class="htmlview paragraph">When compared to conventional control, the predictive control demonstrated considerable energy and fuel savings due to delayed timing of both knock mitigation and activation of radiator cooling fan during high engine load demand. However, this predictive control strategy is much more complicated due to its highly coupled nonlinear behavior. Also, in reality, the previous developed MPC strategies are limited to the computational resources in engine control units (ECU). Therefore, to address these challenges, a reduced-complexity MPC controller for the powertrain thermal system is developed in this paper where, by “reduced-complexity,” it is meant that the MPC controller achieves control objectives and to be executed on a modern ECU within a computation budget.</div><div class="htmlview paragraph">To maximize fuel economy, one of the key control logics in the previously published SAE paper is to use estimated radiator outlet coolant temperature as an indicator to determine when to lower the target engine coolant temperature. Since the heat transfer coefficients (HTC) of the thermal system are time varying, the computation load is high if the inputs to the plant models are physics-based. Therefore, lookup table (LUT)-based and mean value model (MVM) modeling approaches are developed and combined in order to reduce computational burden.</div><div class="htmlview paragraph">The complexity reduction is obtained via lookup tables and mean value models, which lightens the computational load of the algorithm with a minimal loss in precision. Experimental results showed that the proposed approach is able to deliver performance similar to originally proposed approaches. At the same time, the proposed algorithm is able to cut the computational complexity of the physics-based algorithm by an 18% factor.</div></div>

Development of on-line neural network based adaptive fractional-order sliding mode robust controller on electromechanically actuated engine cooling system

The reduction of temperature fluctuations around desired reference and control input energy for cooling actuators are among the most important aims of engine thermal management system. However, maintaining of engine/radiator outlet temperature within certain limits is a challenging process in different engine operating conditions due to unknown in-cylinder variable heat transfer rate in terms of the control theory. For this purpose, the thermodynamic model is obtained by dividing into two subsystems, such as the engine and the radiator subsystem in the presence of unknown heat transfer rate, external disturbance, and uncertainties in this study. To increase system robustness, tracking engine inlet/outlet temperature control of engine cooling components is performed using the adaptive fractional-order sliding mode control structure. Moreover, the disturbances acting on the system and unknown heat transfer dynamics of the system are estimated with a radial basis function on-line neural network estimator. The efficiency of proposed controller strategy for electromechanically actuated engine cooling system is compared by proportional–integral–derivative and classical integral sliding mode control under the NEDC (New European Driving Cycle) and WLTP (Worldwide Harmonized Light Vehicles Procedure) transient operating conditions. The temperature error tracking performance is tested by paying attention integral square error, integral absolute error, integral time-weighted absolute error along to the driving cycles. The obtained results showed that the adaptive fractional-order sliding mode control–based engine cooling system outperforms compared to the optimally gain tuned proportional–integral–derivative and integral sliding mode control schemes in terms of reducing of tracking error and engine cooling actuators energy consumption for all engine operating cycles.

Modelling and optimal control of energy-saving-oriented automotive engine thermal management system

The thesis simulates the engine?s installation and uses conditions in the whole vehicle, such as the water tank, fan, the engine?s arrangement in the engine room, accessories and pipe-line connections, etc. to build a test bench for the engine thermal management system. According to the thermal management simulation analysis software KULI modelling, the article designs the bench test conditions according to the parameter input requirements of the thermal management simulation analysis software. The accuracy of the model is verified by comparing simulation and test data, and the NEDC driving cycle is used to simulate the performance of the vehicle cooling system to guide the selection and matching of thermal management system components.

Application of the phase-averaged pre-processing method in identification of oscillatory two-phase flow patterns based on textural features

Oscillatory two-phase flow as a common two-phase flow occurs extensively within the engine's thermal management system. However, it is found that the oscillatory two-phase flow patterns at the same location have different flow states caused by the strong turbulence under fast moving speed conditions, making it difficult to propose systematic identification and judgement criteria. Common image processing methods applied to tube flow are unsuitable for the analysis of oscillatory two-phase flow with particularly complex flow patterns. To solve this problem, this paper presents a study aiming to determine common rules from the instantaneous flow patterns by eliminating the random variability and making the oscillatory two-phase flow pattern images more representative. Applying the phase-averaged pre-processing and textural feature method to the instantaneous oscillatory two-phase flow patterns, which are captured by the designed visualized test bench, the lowest identification results based on the Support Vector Machine (SVM) could achieve an accuracy of 92.5%. The results suggest that the study presented in this paper offers an effective method for the analysis and identification of oscillatory two-phase flow patterns. Visualized experimental results in the related fields of two-phase flow will be more comprehensive with objective descriptions and representative flow pattern images.

Model Order Reduction for Control of Engine Thermal Management Systems using Singular Perturbation

Improvements in engine efficiency are required to meet the increasingly rigorous regulation standards. To achieve this goal, more efficient procedures for modeling system, simulations and model-based control are required. In this paper we propose a methodology to simplify complex engine thermal management models for control purposes. A direct analysis of a complex physics-based model for the engine thermal management system is used to provide a first level of approximation. Singular perturbation is then used to further decrease the complexity of the model without losing prediction performance. The reduced model is then compared to the complete model and simulation results confirm the validity of the approach.

Assessment of engine thermal management through advanced system engineering modeling

A physically based approach to model vehicle dynamics, transient engine performance and engine thermal management system is presented. This approach enables modeling dynamic processes in the individual components and is the dynamic interaction of all relevant domains. The modeling framework is based on a common innovative solver, where all processes are solved using tailored numerical techniques suited to account for characteristic time scales of individual domains. This approach enables achieving very short computational times of the overall model. The paper focuses on the integration of cooling and lubrication models into the framework of a vehicle dynamics simulation including transient engine performance demonstrated on a modern passenger car featuring split cooling functionality. A validated model with a mechanically driven coolant pump provides the base for analyzing the impact of introducing an electrically driven coolant pump. Analyses are performed for two drive cycles featuring significantly different velocity profiles to reveal their influences on the operational principles of the powertrain components and their interaction. The results show for both drive cycles fuel saving due to the application of the electric water pump is relatively small and amounts between 0.75% and 1.1%. However, it is important to address that application of the electric coolant pump results in higher turbine outlet temperatures and thus in faster catalyst heat-up. Detailed analyses of the interaction between vehicle dynamics, transient engine performance and engine thermal management system provide insight into the underlying mechanisms. This is made possible by the application of physically based system level model.

Thermal Management System Analysis of Marine Diesel Engine

A lumped parameter model is developed to study performance of marine diesel engine thermal management system. One dimensional flow equations combined with classical Webie combustion model and Woschni heat transfer model are employed to describe diesel's flow characteristic. Modeling results of heat release from diesel engine is validated against experimental data. Cooperated with experimental data based models of water pump and heat exchangers, thermal management system performance is analyzed while engine fresh cooling water outlet temperature is controlled to achieve a certain value by a PID temperature regulating valve. The results shown that inlet seawater temperature variation has relatively little effect on opening of regulating valve, but engine power output variation results in notably regulating valve opening fluctuation. Modeling results would be employed in an advanced submarine diesel engine system design. 

Control-Oriented Modeling of an Automotive Thermal Management System

The design of control strategies for advanced powertrains and related thermal management systems requires the development of models to characterize their steady-state and transient behavior. Such models have to be simple enough to allow for control design, however complex and accurate enough to capture the relevant dynamics.This work presents a lumped-parameter model of an advanced engine thermal management system, whose objective is to characterize steady-state and dynamic system behavior for system analysis, optimization and control design. The system was modeled starting from individual components, namely the engine block thermal dynamics, radiator, thermostat, engine oil heater/cooler, transmission oil heater, and cabin heater core. Each model was calibrated on steady-state components data, and the complete thermal system model was then validated on a drive cycle conducted on a test vehicle, comparing the coolant and engine oil temperature traces during the warm-up phase.The results obtained show the model ability to accurately track the warm-up dynamics of the fluids with real-time computational capabilities, hence suggesting potential applications to system analysis and optimization for control design.

Predictive Control Allocation for a Thermal Management System Based on an Inner Loop Reference Model—Design, Analysis, and Experimental Results

This paper addresses the challenge of controlling an overactuated engine thermal management system where two actuators, with different dynamic authorities and saturation limits, are used to obtain tight temperature regulation. A modular control strategy is proposed that combines model predictive control allocation (MPCA) with the use of an inner loop reference model. This results in an inner loop controller that closely matches a dynamic specification for input-output performance while addressing actuator dynamics and saturation constraints. This paper presents the design and implementation strategy and illustrates the effectiveness of the proposed solution through real-time simulation and experimental results.

Parameters setting parameters and simulation of transient state model in engine thermal management based on KULI

On a basis of a heavy-duty diesel engine the cooling system model was established using KULI software,and the temperature of coolant and oil was simulated at transient state.The paper mainly described that how to set engine model parameters in a transient state model with KULI software.The results show that using the engine model,the simulated results are in good accordance with experimental data,so the model is reliable and the principle of parameters setting provides a method for setting engine thermal management transient model which can be used to other engines.The engine model supplies appropriate thermal boundary environment for Engine Thermal Management System(ETMS),and it can be used to simulate the whole ETMS.

An Advanced Engine Thermal Management System: Nonlinear Control and Test

Internal combustion engine thermal management system functionality can be enhanced through the introduction of smart thermostat valves and variable speed electric pumps and fans. The traditional automotive cooling system components include a wax based thermostat valve and crankshaft driven water pump. However, servo-motor driven valves, pumps, and fans can better regulate the engine's coolant fluid flow to realize fuel economy gains and tailpipe emission reductions. To study these cooling system actuators, with accompanying nonlinear control strategy, a scale experimental system has been fabricated which features a smart valve, electric coolant pump, radiator with electric fan, and immersion heater. In this paper, mathematical models will be presented to describe the system's behavior. A nonlinear controller will then be designed for transient temperature tracking. Representative experimental results are presented and discussed to demonstrate the smart valve's operation in maintaining the temperature within a neighborhood of the target value for various scenarios including highway mode, full power with load disturbance, and quick heat.