Aircraft Thermal Management System Research Articles

Simulation of an aircraft thermal management system based on vapor cycle response surface model

The modern aircraft Thermal Management System (TMS) faces significant challenges due to increasing thermal loads and limited heat dissipation pathways. To optimize TMS during the conceptual design stage, the development of a modeling and simulation tool is crucial. In this study, a TMS simulation model library was created using MATLAB/SIMULINK. To simplify the complexity of the Vapor Cycle System (VCS) model, a Response Surface Model (RSM) was constructed using the Monte Carlo method and validated through simulation experiments. Taking the F-22 fighter TMS as an example, a thermal dynamic simulation model was constructed to analyze the variation of thermal response parameters in key subsystems and elucidate their coupling relationships. Furthermore, the impact of total fuel flow and ram air flow on the TMS was investigated. The findings demonstrate the existence of an optimal total fuel flow that achieves a balance between maximizing fuel heat sink utilization and minimizing bleed air demand. The adaptive distribution of fuel and ram air flow was found to enhance aircraft thermal management performance. This study contributes to improving modeling efficiency and enhancing the understanding of the thermal dynamic characteristics of TMS, thereby facilitating further optimization in aircraft TMS design.

Integrated Design of a Variable Cycle Engine and Aircraft Thermal Management System

Abstract The integrated design of a variable cycle engine (VCE) and an aircraft thermal management system (TMS) is investigated. The integrated system is designed using the multiple design point approach in order to achieve required performance metrics at points other than the cycle design condition. The VCE architecture is a three stream design where the third stream is split off after the fan, exhausting through a separate third-stream nozzle. The primary air stream passes through a low-pressure compressor before splitting into an inner bypass stream and a core stream. The inner streams mix aft of the low-pressure turbine and exhaust through a core nozzle. The variable cycle engine utilizes variable compressor inlet guide vanes, a variable area bypass injector at the core stream mixing plane, and variable throats in the two exhaust nozzles. The TMS architecture is an air cycle system using air bled from the high-pressure compressor. The effect of integrating the TMS into the engine design loop is investigated. A comparison is made to prior studies where the same TMS architecture was connected to a low bypass ratio turbofan engine. The comparison shows that the variable cycle engine is able to improve heat dissipation capability versus a ram air cooled system, while eliminating the airframe integration impact that comes with a separate ram-air stream. Lastly, the impact of modulating the variable geometry features on overall cooling capability is investigated. Results are presented for individual operating points as well as at the aircraft mission level.

Evaluation of high-speed aircraft thermal management system based on spray cooling technology: Energy analysis, global cooling, and multi-objective optimization

With the increase in aircraft speed, the aerodynamic heating on the aircraft wall has become one of the key factors restricting flight safety. Although passive thermal protection can solve the thermal protection problem of the aircraft body, there will always be some heat transferred into the cabin. And the temperature of the cabin interior environment and cabin wall increases, which reduces safety. The spray cooling system with R134a as a coolant can reduce the cabin wall temperature to 275 K, and the temperature drop rate can reach 1.05 K/s, so that the cabin cooling needs can be realized. The refrigeration system is used to connect the spray system with the fuel loop to form the closed-air spray cooling heat management system of the aircraft. The refrigeration system and the tandem radiator are optimized according to the genetic algorithm. After repeated iterations with different design parameters, the exergy efficiency and COP of the refrigeration system can reach 80 % and 2.36, and the pressure loss and the bottom plate temperature of the microchannel heat exchanger are 0.98 Mpa and 313 K, respectively. According to the analysis of the efficiency of the heat management system, the ejector efficiency, the energy efficiency ratio (EER) of the total system, and the required primary fluid flow rate, the required primary flow rate is at least 0.0027 kg/s to drive the thermal management system, EER of high-speed aircraft thermal management system can reach 15.62 %, exergy efficiency of the refrigeration system and the ejector efficiency can reach 44 % and 1 4% respectively.

Aerodynamic shape optimization of an electric aircraft motor surface heat exchanger with conjugate heat transfer constraint

Electrified aircraft benefit from the versatile ways electric motors can be integrated with an airframe. However, thermal management is needed to move waste heat out of the motors because the heat is not expelled with the exhaust as in a conventional engine. Plate-fin, fin, and surface heat exchangers are incorporated as air-side heat exchangers for electrified aircraft thermal management systems. Typically, analytic tools are used to design heat exchangers within these categories. However, analytic tools lack the fidelity required for detailed shaping and assessment of general heat exchanger configurations. Tools based on first principles, such as finite element analysis or computational fluid dynamics, can verify heat exchanger performance but are too costly to use in a manual design loop. Shape optimization can be used with first-principles-based models to design heat exchangers without limiting the geometry to those previously well studied. In this work, we apply this methodology to design a heat sink for the high-lift motor of an electric technology demonstrator, the X-57 Maxwell. We use a gradient-based optimizer to modify the thickness distribution of the heat sink to find designs that minimize drag while meeting the heat load constraint. To model the heat transfer from the motor, we use both convection-only and conjugate heat transfer models and compare the resulting differences in the optimized shapes. We found that the convection-only model under-predicted heat rejection and thus led to larger than necessary heat sinks when used in optimization. To study the effect of the heat load on the design, we compare the heat sinks designed for the baseline motor and heat sinks designed for less efficient motors. Our study results show how the heat exchanger’s geometry changes from uniformly thick to designs with fins as the heat load increases. Furthermore, we found that the variation in drag across designs is driven by differences in the pressure drag due to flow separation. Finally, we conclude with a comparison of the optimized designs to those representing more simple fin designs and find that the optimized designs have fins that are shifted forward to reduce the adverse pressure gradient, which mitigates separation on the aft part of the fin. The developed shape optimization method could also be applied to improve other heat exchangers, specifically those designed to reject relatively low amounts of heat.

Evaluation of High-Speed Aircraft Thermal Management System Based on Spray Cooling Technology: Energy Analysis, Global Cooling, and Multi-Objective Optimization

Evaluation of High-Speed Aircraft Thermal Management System Based on Spray Cooling Technology: Energy Analysis, Global Cooling, and Multi-Objective Optimization

Design and Analysis of an Aircraft Thermal Management System Linked to a Low Bypass Ratio Turbofan Engine

Abstract The design of an aircraft thermal management system (TMS) that is capable of rejecting heat loads into the bypass stream of a typical low-bypass ratio turbofan engine, or a ram-air stream, is investigated. The TMS consists of an air cycle system, similar to the typical air cycle machines used on current aircraft, both military and commercial. This system turbocharges compressor bleed air and uses heat exchangers in a ram air stream, or the engine bypass stream, to cool the engine bleed air prior to expanding it to low temperatures suitable for heat rejection. In this study, a simple low-bypass ratio afterburning turbofan engine was modeled in numerical propulsion system simulation to provide boundary conditions to the TMS system throughout the flight envelope of a typical military fighter aircraft. Two variations of the TMS system, a ram air cooled and a bypass air cooled, were sized to handle a given demanded aircraft heat load. The ability of the sized TMS to reject the demanded aircraft load throughout several key off-design points was analyzed. It was observed that the maximum load dissipation capability of the TMS is tied to the amount of engine bleed flow, while the level of bleed flow required is set by the temperature conditions imposed by the aircraft cooling system. Notably, engine bypass stream temperatures significantly limit the thermodynamic viability of a TMS designed with bypass air as the heat sink. The results demonstrate the advantage that variable cycle engines (VCEs) may have for future aircraft designs.

Experimental study on operating characteristics of a dual compensation chamber loop heat pipe in periodic acceleration fields

Systematic experiments were firstly designed and conducted to investigate the operating characteristics of a dual compensation chamber loop heat pipe (DCCLHP) under periodic acceleration conditions. A new acceleration test rig was built to generate acceleration magnitude up to 11 g. The heat load ranged from 150 W to 300 W. Three different periodic acceleration patterns, two loading modes and two acceleration directions were used to study their influence on the operating characteristics of the DCCLHP. The results demonstrated that the loop temperature could periodically oscillate with the periodic change of the acceleration. A large acceleration could lead to a high operating temperature. Configuration B could cause the lower operating temperature than configuration A for a fixed case. There were stable operating temperature difference and thermal resistance variation before and after the periodic acceleration acting for the loading mode 1. Temperature overshooting after unloading the periodic acceleration was also confirmed for the loading mode 2. Such phenomena could be explained by the change of the vapour-liquid distribution in the loop and the heat leak from the evaporator to the compensation chambers (CCs). The loop temperature oscillation with different frequency and amplitude might also occur during each periodic acceleration. For the cases of 150 W and configuration A, the acceleration effect could trigger the operating temperature exceeding 60 °C. Our work proves significant phenomena existing in the DCCLHP and presents detailed analysis, which would be of great importance for the development of new generation of loop heat pipe used in aircraft thermal management system.

A MATLAB Simulink Based Co-Simulation Approach for a Vehicle Systems Model Integration Architecture

<div class="section abstract"><div class="htmlview paragraph">In this paper, a MATLAB-Simulink based general co-simulation approach is presented which supports multi-resolution simulation of distributed models in an integrated architecture. This approach was applied to simulating aircraft thermal performance in our Vehicle Systems Model Integration (VSMI) framework. A representative advanced aircraft thermal management system consisting of an engine, engine fuel thermal management system, aircraft fuel thermal management system and a power and thermal management system was used to evaluate the advantages and tradeoffs in using a co-simulation approach to system integration modeling. For a system constituting of multiple interacting sub-systems, an integrated model architecture can rapidly, and cost effectively address technology insertions and system evaluations. Utilizing standalone sub-system models with table-based boundary conditions often fails to effectively capture dynamic subsystem interactions that occurs in an integrated system. Additionally, any control adjustments, model changes or technology insertions that are applied to any one of the connecting subsystems requires iterative updates to the boundary conditions. When evaluating a large set of trade studies, the number of boundary condition models and time to generate these models becomes intractable and affects capturing the results accurately. A single interconnected model of all the subsystems may be impractical and using additional external packages may be prohibitive in terms of cost or compatibility. This general approach requires no additional MATLAB toolboxes. Two different data interchange mechanisms are presented. A dynamic vehicle system integrated model was developed to enable customizability and flexibility. The developed co-simulation approach was combined with this flexible architecture to enable system evaluation. Example applications using the vehicle system model integrated architecture with the co-simulation approach are discussed.</div></div>

Integrated Aircraft Thermal Management System Modelling and Simulated Analysis

In order to improve the thermal energy utilization efficiency of aircraft, an integrated thermal management system model using endothermic fuel has been created in AMESIM. The system includes several thermal subsystems such as environment control system, the hydraulic equipment and power equipment cooling system, and anti-icing/de-icing system. The fuel oil was chosen for heat sink and it could cool the exothermic thermal system and transmit the energy to anti-icing/de-icing system in case of icing. Several simulation examples including three atmospheric conditions were accomplished. The results indicated that the present system had the ability to reuse the waste heat meanwhile all the thermal system worked normally. The anti-icing/de-icing didn’t need additional energy which realized less energy consumption. In addition, the model has the ability to facilitate the analysis and optimization of thermal systems on board.

Control Architecture Study Focused on Energy Savings of an Aircraft Thermal Management System

The next generation of aircraft will face more challenging demands in both electrical and thermal loads. The larger thermal loads reduce the propulsion system efficiency by demanding bleed air from the main engine compressor or imposing a shaft load on the high or low pressure shaft. The approach adopted to power the thermal management system influences the overall fuel burn of the aircraft for a given mission. To assess these demands and to explore conceptual designs for the electrical and thermal management system, a dynamic vehicle level tip-to-tail (T2T) model has been developed. The T2T model captures and quantifies the energy exchanges throughout the aircraft. The following subsystems of the aircraft are simulated in the T2T model: air vehicle system, propulsion system, adaptive power thermal management system, fuel thermal management system, electrical system, and actuator system. This paper presents trade studies evaluating the impact of various approaches in power take-off from the main engine and approaches in control strategy. The trade studies identify different control strategies resulting in significant fuel savings for a given mission profile.

Coke Removal in Fuel-Cooled Thermal Management Systems

In hydrocarbon fuel cooling technology, the coke deposits, which may form in heat exchangers and reactors and on the inside surfaces of fuel system components, degrade heat-transfer, catalyst activity, and fuel-flow characteristics and can lead to system failure. Therefore, in situ regeneration of fouled surfaces was investigated as a practical approach for reducing the impact of coke formation on aircraft thermal management systems. Various surface regeneration techniques, such as carbon burnoff in air or oxygen and carbon gasification using CO 2 or steam, were investigated. The most practical technique for in situ surface regeneration of the heat exchangers is the carbon burnoff method. Although the burnoff method is simple and cost-effective, care must be taken to control strong exothermic reactions. For this reason, a kinetic model has been developed and its successful application to regenerate a fouled multiple-channel heat-exchanger/reactor panel from a scramjet test engine is discussed in the paper.