Browse Topic: Cold weather
Current lithium-ion batteries should generally only be charged above 0 °C, as charging below this temperature can promote lithium plating and irreversible degradation. However, conventional pack-level heating elements increase system mass and design complexity. In addition, heat is transferred from outside into the cell, causing the temperature inside the cell to rise slowly. This study evaluates internal Joule heating of cylindrical Li-ion cells using a zero-mean square-wave current excitation and quantifies the associated aging impact. LG INR21700-M50L cells were tested at 0 °C, −10 °C, and −20 °C with three excitation frequencies (50 Hz, 1 Hz, 10 mHz) at 5 A amplitude. Each cycle consisted of 30 min heating followed by 60 min cooling; reference capacity-based state of health (SOH) was assessed every 50 cycles up to 400 cycles. A maximum surface temperature rise of 14.3 K was achieved, with larger temperature rise at lower ambient temperature and lower excitation frequency. Capacity fade remained below approximately 1% for most conditions; however, at −20 °C and 10 mHz a pronounced SOH decrease to 87% was observed, indicating a critical operating regime. The results provide practical guidance for pulse-heating parameter selection and highlight the need for safeguards and further diagnostics in extreme low-frequency excitation at very low temperatures. This heating approach is particularly suitable for simpler battery-electric applications without thermal management, such as e-bikes or power tools. However, it may also be relevant for applications with existing thermal management systems, as it simplifies battery pack design.
This paper evaluates the feasibility of Restricted Icing operations for light to medium helicopters, which typically lack Full Ice Protection Systems (FIPS). Current regulations normally prohibit these aircraft from flying in known icing conditions, leading to frequent mission cancellations for HEMS and SAR operators. To address this, Airbus conducted flight test campaigns in Norway (2023, 2025) to characterize a safe icing envelope for "cold blade" operations. Results demonstrate that the H145 was able to sustain continuous flight in icing conditions between 0°C and -3°C and perform time-limited operations (5–10 minutes) down to -6°C without compromising safety, handling, or structural integrity. Safe Restricted Icing operations require an operational framework that ensures proper planning, safe routing, briefing, in-flight decision making, and specialized crew training. The study concludes that a Restricted Icing Clearance could significantly enhance winter flight safety. By providing an IFR alternative to VFR flights in marginal weather within a clear operational framework, the introduction of a Restricted Icing Clearance could ensure the availability of critical life-saving missions in typical winter weather.
Compressor durability is a critical factor for ensuring the long-term reliability of Mobile Air Conditioning (MAC) systems in passenger vehicles. This study presents a software based strategy for enhancing compressor life using Smart Fully Automatic Temperature Control (FATC), requiring no additional hardware. The proposed approach leverages existing inputs from the FATC and Engine Management System (EMS) to intelligently manage compressor operation, with a focus on addressing challenges related to prolonged non-usage. In extended inactivity scenarios such as during cold weather, vehicle exportation, storage, or breakdowns, lubrication oil tends to settle in the compressor sump, leaving internal parts dry. Sudden reactivation at high engine speeds under such conditions can cause increased friction, wear and even compressor seizure. To mitigate this, an intelligent reactivation protocol has been developed and integrated into the Climate Control Module (CCM). This protocol continuously monitors parameters such as ambient and evaporator temperatures, solar load and engine RPM to detect extended inactivity. Upon detection, it initiates a controlled compressor activation sequence involving short duration clutch engagement cycles, allowing gradual lubrication and preventing mechanical stress. The strategy includes a multivariable detection framework and dynamic threshold adaptation that tailors activation logic to real-time environmental and operational conditions. A Smart transition mechanism ensures smooth switching between safe and regular operation modes. Preliminary testing shows that this method effectively minimizes dry starts, reduces mechanical wear and supports long term compressor health. The proposed strategy offers a cost effective and robust solution for improving compressor durability, lowering maintenance costs and enhancing user satisfaction.
The third-generation Nissan Leaf represents the automaker's efforts to bring the world's first mass-market modern EV up to date. This meant making changes to the powertrain - better winter charging, new NACS connectors - while keeping some things the same. SAE Media spoke with Jeff Tessmer, senior manager, R&D engineer, technology planning and research at Nissan Technical Center North America, about these updates.
The biography of Henrich Focke is well known and documented. During a small period from October 1954 to February 1956 he held lectures at the Technical University of Stuttgart during the winter semester. In the summer period he returned to Brazil for continuation of his contract work on the "Convertiplane" (a quad-tiltrotor aircraft) and the "Bei-jaflor" (a small single rotor helicopter). The topic of Focke's lecture in the winter semester 1954-55 was "Design of Fixed-Wing Aircraft", but the lecture manuscript of it is unavailable. In the following period 1955-56 Focke lectured about "Helicopter Design" and the manuscript was recently found in the central archive of DLR. It covers 123 pages of text with sketches and graphs and provides deep insights into the helicopter design philosophy of Henrich Focke.
Civil and military rotorcraft operators desire enhanced capabilities from their vehicles in terms of mission efficiency, effectiveness, productivity, and availability. A critical element of this challenge is associated with providing cold weather availability. Currently, cold weather operations are enabled by regulatory actions leading to Limited Approvals, Qualifications, Clearances, and Restrictions. Cold weather certification (clearance of a new aircraft) and continuing airworthiness (maintaining effectiveness of fielded aircraft) are data driven processes. This work provides guidance on an Icing Encounters Survey (IES) based data gathering method supporting continuing airworthiness organizations in improving fleet safety and capabilities during cold weather operations.
Improving the efficiency of Battery Electric Vehicles (BEVs) is crucial for enhancing their range and performance. This paper explores the use of virtual tools to integrate and optimise various systems, with a particular focus on thermal management. The study considers global legislative drive cycles and real-world scenarios, including hot and cold weather conditions, charging cycles, and towing. A virtual vehicle model is developed to include major contributors to range prediction and optimisation, such as thermal systems. Key components analysed include high voltage (HV) and low voltage (LV) consumers (compressors, pumps, fans), thermal system performance and behaviour (including cabin climate control), thermal controllers, and thermal plant models. The emergent behaviour resulting from the interaction between hardware and control systems is also examined. The methodology involves co-simulation of hardware and control models, encompassing thermal systems (coolant, refrigerant, cabin) and the vehicle propulsion domain (driveline, powertrain). This is achieved using a combination of 1D thermos-fluid simulation tools, multi-domain simulation, model-based design block diagram environments, and virtual ECU simulation platform models. The approach can run the entire vehicle operating range and capturing the main HV and LV consumers. The findings demonstrate that integrating thermal system plant and controls through virtual tools can significantly enhance BEV efficiency, providing a comprehensive framework for future developments in electric vehicle technology.
A glow plug is generally used to assist the starting of diesel engines in cold weather condition. Low ambient temperature makes the starting of diesel engine difficult because the engine block acts as a heat sink by absorbing the heat of compression. Hence, the air-fuel mixture at the combustion chamber is not capable of self-ignition based on air compression only. Diesel engines do not need any starting aid in general but in such scenarios, glow plug ensures reliable starting in all weather conditions. Glow plug is actually a heating device with high electrical resistance, which heats up rapidly when electrified. The high surface temperature of glow plug generates a heat flux and helps in igniting the fuel even when the engine is insufficiently hot for normal operation. Durability concerns have been observed in ceramic glow plugs during testing phases because of crack formation. Root cause analysis is performed in this study to understand the probable reasons behind cracking of the glow plug when it is subjected to in-operation conditions and design optimization is also suggested to reduce the risk of cracking. Multiphysics based simulation methodology is developed to capture the overall behavior of glow plug during manufacturing and in-operation conditions. Rapid heating of glow plug by passing of electricity is captured using a coupled electro-thermal simulation approach and the stress developed due to thermal gradient is also captured by a thermo-structural analysis. Effect of different operational parameters over the directional stresses are studied using the developed simulation approach to optimize the glow plug design. Stress comparison results between the existing model and the proposed optimized model is also presented in this paper to demonstrate the improvement in durability behavior of the optimized design compared to the initial design of glow plug. The overall analysis approach, described in this paper can be used as a decision-making tool during initial design stages of glow plug to come up with robust designs.
NASA’s Johnson Space Center is offering an innovative freeze-resistant hydration system for licensing. The technology substantially improves on existing hydration systems because it prevents water from freezing in the tubing, container, and mouthpiece, even in the harshest conditions on Earth.
Chris and Julie Ramsey covered more than 33,000 km (20,505 miles) across three continents in an all-electric passenger vehicle from 1823's magnetic North Pole to the South Pole in a world-first expedition. The Scottish adventurers joyfully recounted their 10-month long globetrotting feat during an interview with SAE Media at the 2024 Chicago Auto Show. The Ramseys' four-wheel transporter was a production 2022 Nissan Ariya e-4ORCE crossover SUV with no changes to the drivetrain, suspension system or 87-kWh lithium-ion battery system. “We wanted to keep the modifications minimal to prove the reliability of a standard EV,” Julie Ramsey said.
Many owners of electric vehicles worry about how effective their battery will be in very cold weather. Now a new battery chemistry may have solved that problem.
ABSTRACT As a continuation of previous collaborative efforts between several US Army organizations and industry leaders which led to the procurement of a National Stock Number (NSN) for a near commercial-off-the-shelf winter tire/wheel assembly for the High Mobility Multipurpose Wheeled Vehicle (HMMWV), this study investigates a low-cost, postproduction modification known as ‘siping’ which may incrementally improve standard tires deployed on the Joint Light Tactical Vehicle (JLTV) in cold regions. Data from engineering tests will quantify performance differences as well as driver feedback from the 11th Airborne Division Soldiers in Alaska show moderate improvement from cutting razor-thin grooves known as ‘sipes’ on conventional winter tire sets. However, Army winter performance specifications developed in 2021 from HMMWV testing quantify greater available improvement to traction available, necessitating further development for winter traction in the JLTV family of tire sets as well as future procurements for additional Tactical Vehicles. Providing Soldiers with state-of-the-art winter tires which are effective at decreasing roll-over and other loss of control incidents increases safety and mobility in northern operations and is the objective of this research. Citation: Witte, C., et al., “Modifying Military Tires for Improved Winter Traction,” In Proceedings of the Ground Vehicle Systems Engineering and Technology Symposium (GVSETS), NDIA, Novi, MI, Aug. 15-17, 2023.
ABSTRACT Cold regions are becoming increasingly more important for off-road vehicle mobility, including autonomous navigation. Most of the time, these regions are covered by snow, and vehicles are forced to operate under active snowfall conditions. In such scenarios, realistic and effective models to predict performance of on-board sensors during snowfalls become of paramount importance. This paper describes a stochastic approach for two-dimensional numerical simulation of dynamic snow scenes that eventually will be used for driving condition visualization and vehicle sensor performance predictions. The model captures realistic snow particle size distribution, terminal near-surface particle speeds, and adequately describes interactions with wind. Citation: S. N. Vecherin, M. E. Tedesche, M. W. Parker, “Dynamic Snowfall Scene Simulations for Autonomous Vehicle Sensor Performance”, In Proceedings of the Ground Vehicle Systems Engineering and Technology Symposium (GVSETS), NDIA, Novi, MI, Aug. 15-17, 2023.
Considerable amounts of water accumulate in aircraft fuel tanks due to condensation of vapor during flight or directly during fueling with contaminated kerosene. This can result in a misreading of the fuel meters. In certain aircraft types, ice blocks resulting from the low temperatures at high altitude flights or in winter time can even interfere with the nozzles of the fuel supply pipes from the tanks to the engines. Therefore, as part of the maintenance operations, water has to be drained in certain intervals ensuring that no remaining ice is present. In the absence of an established method for determining residual ice blocks inside, the aircraft operator has to wait long enough, in some cases too long, to start the draining procedure, leading potentially to an unnecessary long ground time. A promising technology to determine melting ice uses acoustic signals generated and emitted during ice melting. With acoustic emissions, mainly situated in the ultrasonic frequency range, a very high number of events can be recorded to characterize stress relaxation processes that occur during conversions from ice to water. In the present paper, in addition to the case of the fuel tank, the icing of a fuselage panel is also considered. The results obtained provide evidence that it is possible to determine the moment when all ice has melted. However, it is not possible to give exact figures on the amount of ice remaining or melted, which is not a limitation in practice.
With the growing demand in passenger comfort and enhanced safety and high competitiveness in the automotive segment, automotive manufacturers are keen to launch the product flawlessly within short period of time. In that regard one of the areas related to safety of passengers which is windshield deicing, requires lot of attention and to be developed and certified well before the product launch. Computational fluid dynamics (CFD) helps in this regard to come up quickly with a feasible design solution. But with the conventional method of doing deicing requires lot of time and high cell count. Hence there is a requirement of developing a methodology which will shorten the simulation time and thus leading to shorter development time. One such development took place is in the multiphase models in CFD. The present study focuses in introducing a novel methodology for predicting the transient deicing pattern in an automotive windshield. Simcenter STAR-CCM+ version 2021.2.1 was used for the analysis. The new method integrated two multiphase models ‘Fluid Film Melting and Solidification’ and ‘Volume of Fluid (VOF)’. The ice-water region on the windshield, taken as 3D shell, was modeled as a Fluid Film model whereas the ambient air region outside the vehicle in-contact with the ice-water layer was modeled as Volume of Fluid. A multiphase interaction was created between them. The primary application of this phase interaction model was to ensure when a fluid film can accumulate in particular areas of the geometry to form pools. In those areas, the accumulated fluid was modeled as a VOF phase rather than as a fluid film. The new methodology was correlated with the conventional methodology where the ice-water layer was modeled as 3D solid under the multiphase model of ‘Volume of Fluid’. The new methodology was found to reduce the mesh count by 45% of the original, leading to a reduction of computational time to a near 30%. The simulation results also found to be a near exact with transient ice pattern observed from wind-tunnel test result.
It is widely known that different factors, such as cold properties of a fuel as well as a vehicle design, affect the cold operability limit of vehicles. In this study, the aim was to get a better understanding of the properties of modern Light Duty Diesel (LDD) vehicles (2014-2020) that define their cold operability temperature limit. Moreover, the aim was to find out what a responsible fuel producer can do, in addition to providing a proper fuel that meets the specification, to ensure that a vehicle stays operable at cold temperatures. Similar study was done 10 years ago by Neste with the LDD vehicles of that time [1]. Therefore there was a need to update the info to concern the modern LDD vehicles. In this study the operability limit difference between the worst and the best operating LDD vehicle was >10°C (nbr of LDD vehicles = 5) with the same fuel. The limits were determined in a cold chamber using a chassis dynamometer. This operability variance indicates a significant effect of vehicle design on the vehicle’s cold operability limit. The results showed no correlation between diesel fuel’s cold filter plugging point (CFPP) or the surface area of the fuel filter and vehicle cold operability. Therefore, fuel producers should continue the fuel testing using real vehicles to ensure that the produced fuels are suitable for the specific conditions. Moreover, it is good to keep in mind that the results of this study, which demonstrated significant differences in LDD vehicles’ cold operability, were obtained using only one fuel having a specific CFPP, so further studies on this topic are needed.
ABSTRACT To advance development of the off-road autonomous vehicle technology, software simulations are often used as virtual testbeds for vehicle operation. However, this approach requires realistic simulations of natural conditions, which is quite challenging. Specifically, adverse driving conditions, such as snow and ice, are notoriously difficult to simulate realistically. The snow simulations are important for two reasons. One is mechanical properties of snow, which are important for vehicle-snow interactions and estimation of route drivability. The second one is simulation of sensor responses from a snow surface, which plays a major role in terrain classification and depends on snow texture. The presented work describes an overview of several approaches for realistic simulation of snow surface texture. The results indicate that the overall best approach is the one based on the Wiener–Khinchin theorem, while an alternative approach based on the Cholesky decomposition is the second best. Citation: S. Vecherin, A. Meyer, J. Desmond, K. Dunn, B. Quinn, T. Letcher, M. Parker, “Simulation of Snow Roughness for Autonomous Vehicle Numerical Modeling,” In Proceedings of the Ground Vehicle Systems Engineering and Technology Symposium (GVSETS), NDIA, Novi, MI, Aug. 16-18, 2022.
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