Browse Topic: Thermodynamics
Since proportion of wall heat loss takes as high as 20-30% of the total engine heat loss, the reduction of wall heat loss is considered as an effective way to improve the engine thermal efficiency. The heat transfer near the wall boundary layer plays a significant role on the exploration about the mechanism of wall heat transfer which contributes to figuring out the approach to the reduction of wall heat loss. However, the near wall characteristics of heat transfer are still unclear. In this study, the premixed lean methane flame propagation was captured by the high-speed schlieren and the flame behavior in the near-wall region was investigated by the micro CH* chemiluminescence. The temporal histories of the wall temperature and the heat flux are measured by the co-axial thermocouple. The factors including the convective heat transfer coefficient and non-dimensionless numbers, Nusselt number and Reynolds number, were used to characterize the near wall characteristics. Also, the
This paper presents an advanced control system design for an engine cooling system in an internal combustion engine (ICE) vehicle. Building upon our previous work, we have derived models for crucial temperatures within the engine, including combustion wall temperature, coolant-out temperature, block temperature, as well as temperatures in external components such as heat exchangers and radiator. To accurately predict these temperatures in a rapid manner, we have utilized a lumped parameter concept with a mean-value approach. This approach allows for precise temperature estimation while maintaining computational efficiency. Given the complexity of the cooling system, we have proposed a linear time-varying (LTV) model predictive control (MPC) system to regulate the temperatures. This control system linearizes the model at each time step and applies linear MPC over the control and prediction horizons. By doing so, we effectively control the highly nonlinear and time-delayed system
Battery cell aging and loss of capacity are some of the many challenges facing the widespread implementation of electrification in mobility. One of the factors contributing to cell aging is the dissimilarities of individual cells connected in a module. This paper reports the results of several aging experiments using a mini-module consisting of seven 5 Ah 21700 lithium-ion battery cells connected in parallel. The aging cycle comprised a constant current-constant voltage charge cycle at a 0.7C C-rate, followed by a 0.2C constant current discharge, spanning the useful voltage range from minimum to maximum according to the cell manufacturer. Charge and discharge events were separated by one-hour rest periods and were repeated for four weeks. Weekly reference performance tests were executed to measure static capacity, pulse power capability and resistance at different states of charge. All diagnostics were normalized with respect to their starting numbers to achieve a percentage change
Charging a battery electric vehicle at extreme temperatures can lead to battery deterioration without proper thermal management. To avoid battery degradation, charging current is generally limited at extreme hot and cold battery temperatures. Splitting the wall power between charging and the thermal management system with the aim of minimizing charging time is a challenging problem especially with the strong thermal coupling with the charging current. Existing research focus on formulating the battery thermal management control problem as a minimum charging time optimal control problem. Such control strategy force the driver to charge with minimum time and higher charging cost irrespective of their driving schedule. This paper presents a driver-centric DCFC control framework by formulating the power split between thermal management and charging as an optimal control problem with the goal of improving the wall-to-vehicle energy efficiency. Proposed energy-efficient charging strategy
Alpha Engineered Composites’ thin profile textile composite heat shields provide thermal protection through several thermodynamic mechanisms including: radiation reflection; heat spreading; and finally heat transfer resistance. Typical under the hood automotive applications require heat shield average operational temperature up to 225°C, but newer internal combustion engines are being designed for higher operational temperatures to: increase efficiency through higher compression cycle ratios and lean burning; boost power through turbocharging; increase energy density; and support advanced emissions controls like EGR that can increase average operational temperature up to 300°C. Unfortunately, thermo-oxidative degradation mechanisms negatively impact the polymer structural adhesive within a heat shield textile composite and degrade thermal protection mechanisms. High average operational temperature degradation of traditional versus next generation textile composite heat shields is
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