Flying car is an effective transport to solve current traffic congestion. The power batteries in flying cars discharge at a high current rate in the takeoff and landing phase, evoking a severe thermal issue. Flat heat pipe (FHP) is a relatively new type of battery thermal management technology, which can effectively maintain the temperature uniformity of the battery pack. We have constructed a resistance‐based thermal model of the batteries considering the impact of the state of charge (SOC), battery temperature, and current on the battery heat generation. The FHP model is developed based on segmental heat conduction model, and integrated into the battery model to form the battery‐FHP‐coupled model for a battery module. Experiments are carried out to verify its accuracy. Then, the battery thermal performance is analyzed under the different discharging conditions including constant discharge rates and dynamic discharge rates for flying cars. Under the condition of the flying cars, the battery maximum temperature appears at the end of takeoff stage, while the maximum temperature difference appears during the forward flight segment. Moreover, different FHP heat dissipation structures are studied to further improve the battery thermal performance. The configuration with the best performance is adopted for the battery pack, and it can meet the heat dissipation requirements of the pack at a discharge rate of 3C or that of flying cars. Finally, the influence of inlet cooling air velocity and temperature on battery thermal performance is investigated. According to the research results, air velocity has little effect on the battery maximum temperature at the discharge rate of flying cars, but it can obviously affect the temperature decrease rate. Besides, the battery maximum temperature and its temperature difference develop linearly with the air temperature.

A novel heat dissipation structure based on flat heat pipe for battery thermal management system

Gear pumps represent the majority of the fixed displacement machines used for flow generation in fluid power systems. In this context, the paper presents a review of the different methodologies used in the last years for the simulation of the flow rates generated by gerotor, external gear and crescent pumps. As far as the lumped parameter models are concerned, different ways of selecting the control volumes into which the pump is split are analyzed and the main governing equations are presented. The principles and the applications of distributed models from 1D to 3D are reported. A specific section is dedicated to the methods for the evaluation of the necessary geometric quantities: analytic, numerical and Computer-Aided Design (CAD)-based. The more recent studies taking into account the influence on leakages of the interactions between the fluid and the mechanical parts are explained. Finally the models for the simulation of the fluid aeration are described. The review brings to evidence the increasing effort for improving the simulation models used for the design and the optimization of the gear machines.

Models for Flow Rate Simulation in Gear Pumps: A Review

Pyrometry measurements of clouds of high-temperature particles require an estimate of the spectral dependence of the particle emissivity. Common assumptions for this dependence range from e λ ~ λ -2 to e λ ~ constant. Depending upon the assumption used, there is uncertainty in the temperature of 100 s to a 1000 K in high-temperature clouds. Such errors are not apparent in goodness of fit of spectral data. A heterogeneous shock tube was used to measure the emissivity of aluminum oxide in an inert environment as a function of temperature (2000-3500 K), wavelength (0.55-0.95 μm), and particle diameter (50 nm-10 μm). In micro-sized alumina particles, the spectral dependence upon temperature transitions from decreasing with wavelength to increasing with wavelength with the dependence being roughly gray at about 3000 K. Because of local minima in the e λ vs λ curve, a power-law (λ n ) dependence is insufficient to describe the emissivity. However, if such a dependence is assumed, n transitions from -1.4 to 0.5 as temperature increases from 2500-3500 K. Nano-sized alumina particles exhibit an even stronger spectral dependence. At 2678 K, n is approximately -1.2 but reaches as high as 2.1 at 3052 K. Considering optical depth issues, there is merit in gray emissivity approximations for high-temperature (~3000-3300 K) particles typical of aluminum particle combustion.

Emissivity of Aluminum-Oxide Particle Clouds: Application to Pyrometry of Explosive Fireballs

Metal powder combustion has traditionally been studied to mitigate the risk of industrial accidents and to determine the contributions of metals as additives to the performance of energetic materials. Recently, there has been growing interest in exploring the potential of metal powders as recyclable, zero-carbon energy carriers as an alternative to the hydrocarbons known to contribute to climate change. The present work introduces, for the first time, a stabilized flat iron flame. The counterflow burner used in this work is comprised of an inverted ceramic nozzle which sits above, and is aligned axially with, a lower nozzle producing a laminar flow of particles suspended in an oxidizing gas. A stabilized methane flame sits inside the top nozzle and the hot combustion products impinge upon the two-phase flow from the bottom nozzle, creating a stagnation plane. Spherical iron powder, with 90% of the particles less than 2.5 µm in size, is pre-loaded into a piston and dispersed using mixtures of 30% and 40% oxygen balanced in argon. Flame speeds are measured using particle image velocimetry (PIV), while flame temperatures are determined using multicolour pyrometry. It is found that flame speeds range between 30 cm/s and 45 cm/s for both oxidizing mixtures. Despite having fuel loadings below stoichiometric concentrations, the observed particle combustion temperatures are close to the adiabatic flame temperature of the stoichiometric mixture, indicating combustion in the diffusion-controlled regime for these small particles. Finally, the independence of the flame speeds with respect to oxygen concentration suggests flame propagation in the discrete regime.

Stabilized, flat iron flames on a hot counterflow burner

Urban air mobility (UAM), is an effective solution to the current ground traffic congestion dilemma in the near future Electric power and propulsion system is one of the key technologies for commercial applications of flying cars Therefore, it is essential to study the power battery operating characteristics under typical flight mission profiles for flying cars This paper summarizes the relevant researches on the power battery operating performance under the vertical takeoff and landing (VTOL) mission profile and builds up the theoretical model of the flying car Based on the MATLAB Simulink, the simulation and analysis of power batteries are carried out under the designed mission profile for flying cars After simulation, it’s found that the power and discharge rate at the end of the vertical climb acceleration segment are the highest in the entire mission profile, where the discharge rate reaches 64C And the speed, acceleration and climb height have an important impact on the characteristics of the power battery and the recharge mileage of the flying car

Simulation and analysis of operating characteristics of power battery for flying car utilization

Modelling Approach on a Gerotor Pump Working in Cavitation Conditions

Negative effects of greenhouse gas emissions from internal combustion engines has motivated a global trend towards electrification of transportation powertrains. Additionally, electrification of vehicle prime movers has enabled novel powertrain configurations such as electric distributed propulsion. Electric vertical take-off and landing (eVTOL) aircraft are a novel transportation mode developed at a confluence of emerging technologies including electric powertrains. eVTOLs are poised to institute a major change to urban mobility by increasing the speed and efficiency of urban travel. To facilitate safe and reliable operations, eVTOL battery packs must reliably provide adequate electrical power for mission requirements while sustaining pack health and cycle life over the course of hundreds of missions. These packs are under considerable thermal stress during flight, and must be designed to meet the challenges caused by these thermal stresses, including keeping individual battery cells below temperature limits. Using system simulation can be instrumental in providing optimal design of battery pack layouts and thermal management strategies. A multi-physics system simulation model has been constructed to predict the electrical-thermal-fluid performance of the A3 Vahana eVTOL battery pack with comparison to test data derived from a notional eVTOL mission profile. The model predicts outputs including individual cell currents, cell temperatures, cell voltage, environmental temperatures, and impact of different thermal management strategies on eVTOL battery pack design. The thermal profile predicted during flight is then passed to a predictive model for battery life using GT-SUITE simulation software. The model is then configured to simulate a thermal runaway event, where one cell is heated to the point of runaway, and response of the pack is predicted under different cooling strategies.

Using Multi-physics System Simulation to Predict Battery Pack Thermal Performance and Risk of Thermal Runaway During eVTOL Aircraft Operations

Thermal emission from burning aluminium droplets in solid propellants has been analysed using radiative transfer theory and infrared intensity measurements from emission images of burning droplets at 1–5 atm. Below 5 atm, infrared emission is dominated by the burning droplet, not the detached flame zone around the droplet. Each droplet consists of a molten metal portion and a molten oxide (cap) portion. Emission from the metal portion of the droplet surface is spatially uniform and corresponds with opaque surface theory. Emission from the oxide cap portion of the droplet surface is spatially non-uniform and corresponds with volumetric emission from a non-opaque surface. The oxide cap was approximated as a truncated section of a sphere. The burning droplet temperature was found to be approximately 300 K below the metal boiling point. Account was also taken for non-isothermal particulate emission by the sub-micron oxide smoke cloud formed in the detached flame zone around the droplet. The analysis was able ...

Analysis of thermal radiation from burning aluminium in solid propellants

Modeling Gerotor Oil Pumps in 1D to Predict Performance with Known Operating Clearances

There is a growing interest in accidental fires involving solid-propellant rocket motors Many solid rocket motors are aluminized, and whether it is a large-scale launch booster or a smaller satellite orbital-transfer motor, fire spread in such situations would be significantly augmented by radiation from burning aluminium in the propellant Thus, there is a need for simple, accurate models of thermal emissions properties of burning aluminium that can be incorporated in computational simulations of combustion of aluminized solid propellant

Simple Model of Thermal Emission from Burning Aluminum in Solid Propellants

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