Peak Heating Rate Research Articles

Titan aerogravity-assist maneuvers for Saturn/Enceladus missions

Mission analysis using aerogravity-assist (AGA) maneuver at Titan is presented in this paper. Considering Saturn arrival, Titan encounter, and different post-AGA orbits, the analysis uses vector diagrams to illustrate the relations among all conditions as well as design constraints. The analysis focuses on Enceladus mission concept and also present a summary result for Cassini-type Saturn system missions. Turn angles using AGA maneuver at Titan are quantified via numerical simulation, showing that 25-deg AGA turn angles are achievable with a Titan inbound excess velocity (V∞, IN) of 10–20 km/s. Results show that for an Enceladus mission, V∞, IN of 10 km/s is the minimum velocity required for AGA maneuver to achieve an outbound transfer orbit directly to Enceladus; the corresponding peak g-load is less than 6 g, peak heat rate less than 200 W/cm2, and total heat load of around 25 kJ/cm2. For a Cassini-type Saturn mission, a minimum V∞, IN of 5 km/s can be used for Titan AGA. The results showed are for V∞, IN of 6 km/s; and the corresponding peak g-load, peak heat rate, and total heat load are 1.5 g, 20 W/cm2, and 5 kJ/cm2 respectively.

Feasibility and Mass-Benefit Analysis of Aerocapture for Missions to Venus

A numerical assessment of the feasibility of aerocapture at Venus is presented, and the mass benefit of aerocapture is compared with propulsive orbit insertion. This paper considers constraints imposed by entry corridor, deceleration loads, and aerodynamic heating on aerocapture for two vehicle control techniques: lift modulation and drag modulation. Feasibility charts are presented to graphically visualize the aerocapture design space spanning interplanetary trajectory and vehicle performance. Results indicate lift modulation aerocapture is feasible at Venus using existing blunt-body aeroshells. Drag modulation technique is also feasible and an attractive option for small satellites, but merits an additional study due to small corridor width and heating constraints. The peak heat rate is within the capability of existing thermal protection system materials for both control techniques. Delivered mass fraction using aerocapture is compared with propulsive insertion with and without aerobraking. Aerocapture allows 90–250% increase in delivered mass to a 400 km circular orbit compared with propulsive insertion.

Microstructure and mechanical properties of thermal simulation CGHAZ of DP780 high strength steel

In order to reduce the weight of the vehicle, DP780 high-strength steel is a favorite choice of material in the automobile industry, because of its high strength. However, its coarse-grained heat affected zone (CGHAZ) acts as a deterrent for wider applications, making it necessary to find suitable welding parameters to ensure the reliability of the CGHAZ during operation. The present work focuses on the effects of peak temperature and heating rate on the microstructure and the mechanical properties of DP780 CGHAZ, during thermal simulation of welding. The results show that the microstructure of the CGHAZ is mainly composed of martensite (M), tempered martensite (TM), upper bainite (UB), primary austenite grain boundary (AGB) and ferrite (F). In terms of mechanical properties, the results of the welding simulation showed that, the toughness of the CGHAZ is significantly decreased, the elongation and impact energy are notably degraded; while, at the same time, the Rockwell hardness is improved. It is proven that reducing the heat input to the weld, using a lower peak temperature (1130 °C) and heating rate (65 °C min−1) for welding, has a positive influence on improving the performance of the CGHAZ.

The shift of the thermoluminescence peak maximum temperature versus heating rate, trap filling and trap emptying: Predictions, experimental verification and comparison

The peak maximum temperature (Tmax) at the maximum intensity (Imax) are basic characteristics of a thermoluminescence (TL) peak. It is theoretically predicted and experimentally verified that Tmax shifts to higher temperatures as the readout heating rate increases. It is also predicted theoretically that Tmax shifts to lower temperatures as the radiation dose increases. However, although, experiments of the TL as a function of dose are the most common in TL literature the predicted shift is never unambiguously verified. This discrepancy between theory and experiment is extensively investigated in the present work. The behavior of the Tmax as a function of (a) heating rate, (b) dose (trap filling) and (c) trap decay (trap emptying) was studied in CaSO4:Dy, CaSO4:Tm, LiB4O7:Cu,In, MgB4O7:Dy,Na, Al2O3:C, BeO, and a sample of natural salt un-annealed and annealed at 600 . The results showed that the shift of Tmax as a function of heating rate and trap emptying are experimentally verified. On the other hand the shift of Tmax as a function of radiation dose (trap filling) is not verified experimentally. The results are extensively discussed and the explanations of the three different sources of Tmax shift are attempted.

Biochar from pyrolysis of biological sludge from wastewater treatment

It was studied the production of biochar by pyrolysis of biological sludge from wastewater treatment in the pulp and paper industry. The pyrolysis process was conducted in bench-scale fixed-bed reactor using distinct operating conditions of heating rate (2, 10, 20 and 30 ºC/min) and peak temperature (300, 375, 450, 525, and 600 ºC). The biochar yield is in the range 0.40 to 0.73 kg/kg dry sludge, and decreases with increasing peak temperature and heating rate. The organic matter content of the biochar is in the range 55.9 to 75.3%wt. (dry basis). Both the temperature increase and the heating rate increase promote the decrease of biochar volatile matter content within values between 14.4 and 48.4%wt. (dry basis). The biochar ash content increases with peak temperature and heating rate, and it has values in the range 24.7 to 44.1%wt. (dry basis). The corresponding fixed carbon content is between 26.2 and 42.4%wt. (dry basis), and increases with an increase in the peak temperature. The carbon concentration in the biochar is in the range 42.8 to 47.0%wt. (dry basis). The biochar pH is in the range 6.9 to 11.2, and the electrical conductivity (EC) is in the range 2.2 to 5.0 mS/cm.

Thermo-mechanical behaviour of granite during high-speed heating

Fire accident is a common and serious damage phenomenon affecting tunnels, historical sites, buildings, monuments, etc. However, the understanding of the thermo-mechanical behaviour of rocks during fire and the corresponding damage on the rocks is still limited. In this study, the thermo-mechanical behaviour of Eibenstock granite under the temperature of 400 °C and 800 °C was studied applying heating rates of 5 °C/min, 200 °C/min, 300 °C/min, and according to ISO 834 standard fire curve. A supersonic frequency induction heating system was used to conduct the required heating scenarios and to perform uniaxial compression tests under the desired temperatures. A threshold modulus Ec obtained from dividing peak axial stress by the peak axial strain is defined to characterize the stiffness of the sample at various temperatures. Both tangent Young's modulus and threshold modulus are greatly influenced by maximum temperature, while the influence of heating rate is relatively small. The maximum temperature has the dominant impact on the uniaxial strength of granite sample, while the influence of heating rates is again negligible. The peak axial strain increased obviously with rising temperature. It first increases at 200 °C/min heating rate and then reduces slightly in scenarios with heating rate of 300 °C/min or heating according to ISO 834. The observed failure modes after uniaxial compression tests are influenced by peak temperature and heating rates. The granite specimen can be crushed in the shape of blocks, fragments or powder. The deduced friction angle for various heating scenarios is more or less consistent, while the cohesion shows a strong temperature-dependent characteristic. Although the cooling process can lead to an increase in crack density, UCS, peak axial strain and cohesion are enhanced at lower temperatures. The presented results help to understand the damage mechanisms of granite caused by fire, and can be used to develop guidelines for repair and maintenance as well as assessment of risks of tunnels and historical buildings after fire accidents.

Multi-scale thermal stability study of commercial lithium-ion batteries as a function of cathode chemistry and state-of-charge

This paper takes a critical look at the materials aspects of thermal runaway of lithium-ion batteries and correlates contributions from individual cell components to thermal runaway trends.An accelerating rate calorimeter (ARC) was used to evaluate commercial lithium-ion cells based on LiCoO2 (LCO), LiFePO4 (LFP), and LiNixCoyAl1-x-yO2 (NCA) at various states of charge (SOC). Cells were disassembled and the component properties were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and temperature-resolved X-ray diffraction (TR-XRD).The whole cell thermal runaway onset temperature decreases and peak heating rate increases with SOC due to cathode destabilization. LCO and NCA cathodes are metastable, with NCA cells exhibiting the highest thermal runaway rates. By contrast, the LFP cathode is stable to >500 °C, even when charged. For anodes, the decomposition and whole cell self-heating onset temperature is generally independent of SOC. DSC exotherm onset temperatures of the anodes were generally within 10 °C of the onset of self-heating in whole cell ARC. However, onset temperatures of the cathodes were typically observed above the ARC onset of whole cell runaway. This systematic evaluation of component to whole cell degradation provides a scientific basis for future thermal modeling and design of safer cells.

(Invited) The Scalability of Accelerating Rate Calorimetry (ARC) with State of Charge and Capacity

Sandia National Laboratories has used Accelerating Rate Calorimetry (ARC) as a means to evaluate and compare the total energies of thermal runaway. This has been an invaluable tool for evaluating the behavior of new chemistries as they become available in commercial and prototype cells. However, this testing has typically been performed in 18650 cells of ~1-1.5 AH and on cells at 100% state of charge. This has been invaluable for the evaluation and comparison of the thermal runaway of different lithium ion battery chemistries, however it leaves open questions as how changes to energy density, cell size and state of charge impact the results from calorimetry testing. This work examines the results of accelerating rate calorimetry testing on different lithium ion cathode chemistries (LCO, NCA, NMC, LFP) different formats (18650, pouch, large format cylindrical) and states of charge to understand how ARC results are impacted by both energy density and total energy. Also studied are how thermal runaway is impacted by energy in general, looking at both the total energy release during thermal runaway as well as the peak heating rates observed. While the total energy release is expected to correlate with the stored energy of the cell, the peak heating rates will impact how cells might behave in a variety of conditions. This has implications for battery design, as data suggests that even cells at relatively low states of charge may be hazardous if sufficiently insulation allows self-heating to occur even at relatively low rates; figure 1 shows data collected on 14 AH pouch cells summarizing the observed runaway energies and peak heating rates. This shows a relatively linear response as the stored energy increases, however an exponential response is observed with respect to state of charge. While this affirms the conventional wisdom that low state of charge cells are unlikely to go into thermal runaway in most environments, we can still see significant stored energy even at relatively low states of charge. The right conditions may still make these cells hazardous, making it important to fully understand the thermal decomposition of cells under a wide variety of conditions. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. Figure 1 Comparison of total enthalpy observed during runaway of a 14 AH pouch cell to the peak heating rates at various states of charge. Figure 1

Thermal Stability Study of Commercial Lithium-Ion Batteries As a Function of Cathode Chemistry and State-of-Charge

The safety of lithium-ion batteries is mainly quantified by thermal runaway characteristics such as onset temperature, peak heating rate (HR), and maximum pressure release. This talk evaluates the materials aspects of thermal runaway of commercial lithium-ion batteries by correlating the contributions from individual cell components to thermal runaway trends. An accelerating rate calorimeter was used to define the thermal runaway behavior of three commercial 18650 lithium-ion batteries (LiCoO2, LiFePO4, and LiNixCoyAl1-x-y­O2) at various states of charge (SOC). Cells were also disassembled and the thermal properties of their component materials was evaluated by thermogravimetric analysis, differential scanning calorimetry, and temperature-resolved X-ray diffraction. Broadly, lithium-ion battery thermal runaway process begins with solid-electrolyte interface and negative active material decomposition followed by the positive active material breakdown. The experimental results show that the onset temperature is generally independent of SOC and peak HR increases with SOC as a result of cathode destabilization. Overall, LiNixCoyAl1-x-yO2 decomposes readily, and charged LiCoO2 is also metastable, although it decomposes more gradually than LiNixCoyAl1-x-y. Contrary to the layered transition metal oxides, LiFePO4 is stable to > 500oC, even when charged. The results are aimed at informing future engineering and fire protection of commercial lithium-ion batteries. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2018-3360 A

Measuring Enzymatic Stability by Isothermal Titration Calorimetry.

This work demonstrates a new method for measuring the stability of enzyme activity by isothermal titration calorimetry (ITC). The peak heat rate observed after a single injection of the substrate solution into an enzyme solution is correlated with enzyme activity. Multiple injections of the substrate into the same enzyme solution over time show the loss of enzyme activity. The assay is autonomous, requiring very little personnel time, and is applicable to most media and enzymes.

Salt content dependent dielectric properties of pistachios relevant to radio-frequency pasteurization

This study was conducted to investigate the effect of salt content during radio-frequency (RF) heating on rate of temperature increase, dielectric properties (DPs), and reduction of pathogens in pistachios. Also, the effect of RF heating on pistachio quality of varying salt content was determined. Pistachios of different salt content (0, 100, and 330 mg sodium/serving) were inoculated with Salmonella enterica and treated in a 27.12-MHz RF heater. The RF heating rate increased when salt content was in the range of 0–100 mg sodium/serving, but there were no significant (P > 0.05) differences in the rate of temperature rise after salt content reached to 100 mg sodium/serving. Both dielectric constant and dielectric loss factor of pistachios increased with rising salt content. Along with increased salt content, RF treatment time required to reduce this pathogen by 4 log CFU/g decreased first and then remained the same above an upper limit of salt content corresponding to the peak heating rate. RF treatment did not significantly (P > 0.05) cause changes in the color and level of lipid oxidation of pistachios. The results of the current study imply that RF heating may be a potential intervention for inactivating foodborne pathogens in pistachios and that the effect of pasteurization is influenced by dielectric loss factor relative to salt content.

Hadronic Interactions of Energetic Charged Particles in Protogalactic Outflow Environments and Implications for the Early Evolution of Galaxies

We investigate the interactions of energetic hadronic particles with the media in outflows from star-forming protogalaxies. These particles undergo pion-producing interactions which can drive a heating effect in the outflow, while those advected by the outflow also transport energy beyond the galaxy, heating the circumgalactic medium. We investigate how this process evolves over the length of the outflow and calculate the corresponding heating rates in advection-dominated and diffusion-dominated cosmic ray transport regimes. In a purely diffusive transport scenario, we find the peak heating rate reaches $10^{-26}\;\! {\rm erg~cm}^{-3}\;\! {\rm s}^{-1}$ at the base of the outflow where the wind is driven by core-collapse supernovae at an event rate of 0.1 $\text{yr}^{-1}$, but does not extend beyond 2 kpc. In the advection limit, the peak heating rate is reduced to $10^{-28}\;\! {\rm erg~cm}^{-3}\;\! {\rm s}^{-1}$, but its extent can reach to tens of kpc. Around 10% of the cosmic rays injected into the system can escape by advection with the outflow wind, while the remaining cosmic rays deliver an important interstellar heating effect. We apply our cosmic ray heating model to the recent observation of the high-redshift galaxy MACS1149-JD1 and show that it could account for the quenching of a previous starburst inferred from spectroscopic observations. Re-ignition of later star-formation may be caused by the presence of filamentary circumgalactic inflows which are reinstated after cosmic ray heating has subsided.

Arc-Jet Testing of a Variable-Transpiration-Cooled and Uncoated Carbon–Carbon Nose Cone

The last decade has witnessed a considerable effort in the development of materials and structures for reusable thermal protection systems with the final goal of enabling long-duration hypersonic flights and more affordable access to space by multiple reuse of recoverable rocket stages. While the development of materials such as carbon-based and silicon-based ablators has extended the typical lifespan of heat shields for extremely high heating-rate environments, the limited reusability yet prevents their use for the aforementioned applications and, therefore, active cooling techniques have to be considered to preserve the thermostructural integrity of thermal protection systems. For all of these reasons, active cooling of thermal protection systems is required and transpiration cooling has been demonstrated to be one of the most promising cooling strategies in terms of coolant mass saving and minimum disturbances of the external flow. The prototype heat shield used for the experiment on variable transpiration cooling is an axisymmetric uncoated carbon–carbon cone having tailored porosity and variable thickness prescribed at the manufacturing level in order to reproduce a variable blowing profile. The high-enthalpy test demonstrated the capability of transpiration cooling to preserve the cone, characterized by a 0.25-in. radius of curvature, for approximately 92 s while being exposed to a peak heating rate of 637 (stagnation region). Heat shield failure was detected after 92 s due to a high-temperature flow leak inside the sheeting sleeve of the coolant line upstream the sample.

Analytical Assessment of Drag-Modulation Trajectory Control for Planetary Entry

Discrete-event drag-modulation trajectory control is assessed for planetary entry using the closed-form Allen-Eggers solution to the equations of motion. A control authority metric for drag-modulation trajectory control systems is derived. Closed-form analytical relationships are developed to assess range divert capability and to identify jettison condition constraints for limiting peak acceleration and peak heat rate. Closed-form relationships are also developed for drag-modulation systems with an arbitrary number of stages.

Extremely Large Extreme-ultraviolet Late Phase Powered by Intense Early Heating in a Non-eruptive Solar Flare

Abstract We analyzed and modeled an M1.2 non-eruptive solar flare on 2011 September 9. The flare exhibited a strong late-phase peak of extreme-ultraviolet (EUV) warm coronal emissions (∼3 MK), with peak emission over 1.3 times that of the main flare peak. Multiple flare ribbons are observed, whose evolution indicates a two-stage energy release process. A nonlinear force-free field extrapolation reveals the existence of a magnetic null point, a fan-spine structure, and two flux ropes embedded in the fan dome. Magnetic reconnections involved in the flare are driven by the destabilization and rise of one of the flux ropes. In the first stage, the fast ascending flux rope drives reconnections at the null point and the surrounding quasi-separatrix layer (QSL), while in the second stage, reconnection mainly occurs between the two legs of the field lines stretched by the eventually stopped flux rope. The late-phase loops are mainly produced by the first-stage QSL reconnection, while the second-stage reconnection is responsible for the heating of main flaring loops. The first-stage reconnection is believed to be more powerful, leading to an extremely strong EUV late phase. We find that the delayed occurrence of the late-phase peak is mainly due to the long cooling process of the long late-phase loops. Using the model enthalpy-based thermal evolution of loops, we model the EUV emissions from a late-phase loop. The modeling reveals a peak heating rate of 1.1 erg cm−3 s−1 for the late-phase loop, which is obviously higher than previous values.

Re-entry trajectory optimization using pigeon inspired optimization based control profiles

In this paper, the entry trajectory optimization problem of lifting type re-entry vehicle with path constraints is solved using Pigeon Inspired Optimization (PIO). Entry trajectory optimization problem involves finding the control profiles, bank angle, and angle of attack to guide the vehicle safely to the destination. The proposed approach parametrizes the bank angle to be a linear function of energy while the angle of attack is considered to be a monotonic function of Mach number. Thus, the problem of finding control profiles is transformed into three parameter search problem. The PIO algorithm is used to find the values of these parameters that minimizes the objective function. The terminal heading angle offset is minimized using traditional bank reversal logic. A new approach is proposed in which the bank angle is modulated to eliminate the oscillations observed in the altitude profile of an entry vehicle with a high lift to drag ratio (L/D). A methodology to satisfy the given load factor constraint is also proposed, as an alternative to traditional penalty factor approach used for incorporating path constraints in PIO algorithm. The proposed approach is further validated by considering sub-cases with different load factor limits and bank angle as the only control variable. The angle of attack profile obtained from the previous case is considered as the nominal profile. The proposed trajectory optimization strategy using PIO algorithm is simulated for Common Aero Vehicle with high L/D ratio (CAV-H) with different load factor constraint limits. The results show that the obtained angle of attack profile minimizes the peak heat rate experienced by the vehicle and bank angle modulation eliminates the oscillations in the altitude profile as well as makes the entry trajectory satisfy the load factor constraint.

Thermal Stability Study of Commercial Lithium-Ion Batteries As a Function of Cathode Chemistry and State-of-Charge

The safety of lithium-ion batteries is mainly quantified by thermal runaway characteristics such as onset temperature, peak heating rate (HR), and maximum pressure release. This talk evaluates the materials aspects of thermal runaway of commercial lithium-ion batteries by correlating the contributions from individual cell components to thermal runaway trends. An accelerating rate calorimeter was used to define the thermal runaway behavior of three commercial 18650 lithium-ion batteries (LiCoO2, LiFePO4, and LiNixCoyAl1-x-y­O2) at various states of charge (SOC). Cells were also disassembled and the thermal properties of their component materials was evaluated by thermogravimetric analysis, differential scanning calorimetry, and temperature-resolved X-ray diffraction. Broadly, lithium-ion battery thermal runaway process begins with solid-electrolyte interface and negative active material decomposition followed by the positive active material breakdown. The experimental results show that the onset temperature is generally independent of SOC and peak HR increases with SOC as a result of cathode destabilization. Overall, LiNixCoyAl1-x-yO2 decomposes readily, and charged LiCoO2 is also metastable, although it decomposes more gradually than LiNixCoyAl1-x-y. Contrary to the layered transition metal oxides, LiFePO4 is stable to > 500oC, even when charged. The results are aimed at informing future engineering and fire protection of commercial lithium-ion batteries. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2018-3360 A

Feasibility Assessment of Aerocapture for Future Titan Orbiter Missions

Numerical simulation is used to perform parametric analysis to assess the feasibility of aerocapture at Titan over arrival of , vehicle lift-to-drag ratio of 0–1, and vehicle ballistic coefficient of 90 and . Aerodynamic forces, peak heat rate, and total heat load are evaluated. It is shown that aerocapture at Titan requires a lifting vehicle with a minimum lift-to-drag ratio of 0.2 and an arrival of , an equivalent propulsive of about , which is higher than what is realistically possible. Results show that aerocapture requires different interplanetary trajectories from propulsive options, and aerocapture with a vehicle of lift-to-drag ratio of 0.3 enables an arrival of and higher. The peak heat rate is well within the capability of the state-of-the-art technologies of thermal protection system materials. In addition, the vehicle can achieve an inclination change up to 20 deg via an aerocapture maneuver.

Global Aeroheating Measurements of Shock–Shock Interactions on Swept Cylinder

The effects of the fin leading-edge radius and sweep angle on peak heating rates due to shock–shock interactions were investigated in the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel. The cylindrical leading-edge models, with radii varied from 0.25 to 0.75 in., represent wings or struts on hypersonic vehicles. A planar oblique shock at 16.7 deg to the flow intersected the fin bow shock, producing a shock–shock interaction that impinged on the fin leading edge. Three fin sweep angles were tested: 0, , and (swept forward). Global temperature data were obtained from the surface of the fused silica fins using phosphor thermography. Metal oil-flow models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features of the shock–shock interactions. The temperature data were analyzed using one-dimensional semi-infinite and one- and two-dimensional finite-volume methods. These results were compared to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction. The dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite one-dimensional method.

Factors affecting the mechanics of carbonized wood: literature review

The influence of wood properties, such as basic density, moisture content, dimensions of the pieces, chemical composition, anatomy, as well as parameters of the carbonization process, like final peak temperature, heating rate and pressure on the mechanics of charcoal used as a reductant in iron blast furnaces, was reviewed. The quality of charcoal for steelmaking is directly related to the wood quality from which it originated. The adoption of a homogeneous raw material allows a more regular behavior of the furnace, thus increasing the efficiency of the reduction process and consequently decreasing product consumption. The control of pyrolysis parameters such as the final temperature, the heating rate and the pressure contributes to an increase in the mechanical resistance of charcoal, thus improving the efficiency of the thermoreducer and contributing to a better use of energetic forests. A significant increase in the mechanics of charcoal is achieved by carbonization at a final temperature above 500 °C. Future research should focus on operating conditions of pressure and heating rate as a means of optimizing the mechanics of charcoal from wood.