Environmental Control System Research Articles

Energy-efficiency-oriented optimal control for electrical environmental control system based on advanced neural network

Electric environmental control system (EECS) adopts the unique architecture of electric compressor bleed air and multi-stage expansion refrigeration. The state of EECS is regulated by the electric compressor and multiple regulation valves together, resulting in flow and temperature of each node strongly coupled. Traditional methods use a single valve to control each objective without considering the effect of control scheme on energy efficiency, which will not only lead to poor control effect, but also limit the coefficient of performance (COP) of EECS. This paper proposes an energy-efficiency-oriented optimal control strategy to improve the COP and control performance simultaneously. Part of the regulation valves are regarded as optimization variables and the corresponding control objectives are regarded as constraints to maximize COP. On this basis, an advanced control algorithm is proposed to further improve the control effect. The COP prediction model is developed with an offline trained neural network and the optimal valve openings are solved by the differential evolution algorithm. The controller is developed with another neural network online trained by adaptive learning rate algorithm to adapt to complex conditions. The results show that the COP and control performance of EECS are significantly improved. Compared to other strategies, the optimal control strategy can increase COP by up to 61.14%. This study provides an effective solution to the optimal control problem of systems with similar structure to EECS.

Novel Tribometer for Coated Self-Lubricating Spherical Plain Bearings in a Vacuum

Coated self-lubricating spherical plain bearings (SSPBs) are a fairly key component of the space-swing mechanism. To examine the operation status and tribological properties of coated SSPBs, a tribometer with a temperature control module in a vacuum condition was developed. The tribometer was mainly composed of a fixture system, reciprocating rotational motion system, environment control system, etc. First, the tribometer was verified with the self-made hydrogenated diamond-like carbon (H-DLC) SSPBs. The sensor signals indicated that the tribometer conformed to the design specifications. Then, the influence of friction heat on the tribological properties of H-DLC SSPBs was analyzed. The results showed that friction torque and temperature increased with the overall test time. Although the temperature had reached 48 °C, the frictional heat had little effect on the H-DLC SSPBs’ lifespans. The damage mechanism of H-DLC SSPBs was dominated by abrasive wear and fatigue wear in vacuum conditions.

Model based development of temperature control schemes for fighter aircraft ECS

The performance of Temperature Control System (TCS), a sub-system of an advanced fighter ECS (Environmental Control System) is studied for its operations both in on-ground and in-air conditions. The standard Bootstrap air cycle system is considered with ACM (Air Cycle Machine) as the main component, which consists of a compressor and a turbine, to produce the cold air. ECS, in particular TCS, is responsible in maintaining the required cockpit or cabin temperature. As the fighter aircraft doesn’t require cabin air recirculation, the cabin temperature depends solely on the supply air thermal conditions. The cabin temperature regulation is realized by controlling the supply conditions by maintaining required temperature at ACM outlet and at the entrance duct to the cabin. These temperatures are critical parameters that necessitates appropriate controller to keep the cabin in a good comfortable state. ECS of a fighter aircraft is highly complex and nonlinear than commercial aircraft. The control logics applied, on this system, will drive the actuators or TCVs (Temperature Control Valves) to keep the requisite cabin temperature. The control logics applied on the controller to be simple and appropriate to meet the requirements of fighter aircraft ECS. This shall minimize the control cycle oscillation and subsequent supply air temperature instabilities. This paper explains novel cabin temperature control schemes and their influence on the ECS performance especially during the transient operation. The complete architecture of the control schemes along with system components are modelled in AMESim and the comparison is made for different operating conditions. Finally, a novel variable time-delay based method to control the cabin supply air temperature is proposed.

Pressure drop of R134a in mini channels with micro pin fins during flow boiling

Flow boiling in mini channel with micro pin fin arrays is a promising technology for thermal management in various fields such as microelectronics, energy utilization and national defence. Understanding its flow characteristics is the pave stone for further structure optimization of two-phase microchannel heat sinks. However, previous studies paid few attentions to the effect of different structural parameters on its flow performance, especially for the application with long channels for practical evaporators in aircraft environmental control systems. In this paper, an experimental system was set up to investigate the flow boiling pressure drops of refrigerant R134a in a 300 mm long channel with micro pin fin arrays. The flow characteristics of staggered diamond pin fin arrays with different channel widths of 1.0, 1.2 and 1.4 mm and fin angles of 30°, 60°and 90° were comprehensively investigated. The pin fins with a height of 0.5 mm were arranged in the rectangular channel through 3D printing. Two-phase pressure drops in the test section were then measured. The test range of vapor quality, mass flux, heat flux and saturation pressure were 0–1, 200–500 kg/m2s, 10.0–37.5 kW/m2 and 390–700 kPa respectively. Experimental results revealed that the smaller channel width and the greater diamond angle resulted in the greater two-phase pressure drops. The heat flux showed an insignificant influence on the two-phase pressure drops. The existing empirical correlations for pressure drops were evaluated and failed to predict the present experimental data. A new one with the consideration of pin fin structure parameters was then developed to improve the prediction accuracy with the maximum mean absolute deviation of 5.4 %. The proposed correlation can illuminate future study on flow boiling in mini channel with pin fin arrays and be beneficial for the practical design of two-phase microchannel heat sinks.

Recent developments in evaluation methods and characteristics of comfort environment in underground subway

In recent years, due to the rapid progress of urbanization, the subway system with the advantages of large transport capacity, punctuality, efficiency, convenience and safety has become one of the main transportation modes in metropolitan areas. With the increase in passenger flow, the comfort of subway passengers has attracted extensive attention from the academic community. In this paper, we begin by analyzing the characteristics of the subway environment and sort out six environmental elements that affect passengers’ comfort, including thermal environment, vibration, noise, lighting, air quality, and air pressure. In addition, the measurement scheme, calculation model, and evaluation method of each element are outlined based on relevant norms and literature. Through reviewing the studies in the past 2 decades, it is found that the in-depth research is still in demand for a comprehensive comfort evaluation model with multi-element coupling. A deep understanding of the subway passengers’ comfort is the basis for the design, development, and operation regulation of the subway environmental control system. Measures to improve comfort, especially the exploitation of energy-saving air conditioning systems, will provide strong support for the sustainable and sound growth of the rail transit industry.

Perancangan dan Implementasi Sistem Pemantauan Suhu dan Ketinggian Air pada Akuarium Ikan Hias berbasis IoT

Environmental monitoring and control systems of various electronic equipment such as sensors, actuators, televisions, lights, and surveillance cameras are one of the essential applications of Internet-of-Things (IoT). The utilization of IoT has also given birth to the smart home concept, which is realized in the form of home automation, where various equipment at home is equipped with a microcontroller and WiFi module such that they can connect to the Internet and interact with each other. One of the equipment at home that can be monitored and controlled using IoT technology is a fish aquarium which is commonly owned by ornamental fish cultivators or people who have a hobby of taking care of ornamental fish. Taking care of ornamental fish requires special attention to the parameters of temperature and water quality such that the fish can grow well. This study aims to design and implement an IoT-based temperature and water level monitoring system in an aquarium. The hardware in this system is implemented using NodeMCU ESP8266 as the central controller and the WiFi module that connects the system to the Internet, temperature sensor DS18B20, ultrasonic sensor HC-SR04, and relays to turn on and off equipment controlled by the system. In addition, Telegram bots are used to give commands to control equipment and receive notifications from the system. The testing results show that the designed system can work according to predetermined specifications. If the water temperature in the aquarium is outside of a specified range (24°C to 32°C), the system will activate a fan or a heater to adjust the water temperature.

An Available-to-Implement Thermal Facility for Dynamic Bleed Air Test of Aircraft Environmental Control System

As a critical system of onboard aircraft equipment, the environmental control system (ECS) has an essential impact on flight safety. The performance of the ECS is usually tested using the thermal test facility. The facility comprises temperature and pressure simulation units to simulate the engine bleed air. Currently, the ECS often fails due to the dynamic and rapid changes in the temperature and pressure of bleed air. To achieve the dynamic bleed air simulation, the most critical problem is to simulate the bleed air’s rapid heating and boost process during the actual engine working process. However, the temperature simulation unit has the characteristics of nonlinear and large inertia. Moreover, temperature and pressure control are strongly coupled. These characteristics usually lead to temperature and pressure dynamic control failure. This paper introduces a novel facility that adopted the hot and cold blending method to realize the rapid response of the temperature. Furthermore, it used a particular system structure to reduce pressure and temperature control coupling. In addition, it adopted the lookup-table-based PID (LPID) controller to acquire the rapid response and good steady-state performance of temperature and pressure control. Experimental control results are presented and discussed. The results showed that the facility could meet ECS’s dynamic and steady-state test requirements. The novel facility makes up for the insufficient dynamic test capacity of the previously developed ECS test facilities.

Improved Local Scale Generic Cycle Model for Aerothermodynamic Simulations of Gas Turbine Engines for Propulsion

A local scale Aerothermodynamic Generic Cycle Model (AGCM) is proposed. The AGCM accounts for several improvements not considered in similar models, such as compressor bleed extraction for aircraft Environmental Control System (ECS), parasitic shaft power extraction, and the enthalpy of the fuel entering the combustor. The AGCM is intended for steady-state Design Point (DP) and Off-Design (OD) performance analyses. The underlying physics is presented for the DP model. The turbomachinery component maps scaling and the system of nonlinear equations necessary to define the OD model are thoroughly discussed. The AGCM is compared with an equivalent model developed in the Numerical Propulsion System Simulation (NPSS). The comparisons were performed considering a DP envisioned to approximate a General Electric CF34-8C5B1 engine. The average errors found in these comparisons for the Specific Fuel Consumption (SFC) and net thrust were −0.111% and 0.193%, respectively. Finally, the predictions of the absolute levels of performance intended for the -8C5B1 engine are compared with empirical correlations derived from a comprehensive turbofan engine database. It was found that the predictions of the AGCM are in agreement with the empirical correlations; the errors found in SFC and net thrust at cruise flight condition were −0.43% and 2.06%, respectively.

Comparison of mean-line design methods on matching characteristics of three coaxial-impellers in an aircraft environmental control system

High-speed turbo-cooler of coaxial expander-compressor is a promising solution for reverse Brayton cycle refrigeration systems to improve compactness, power recovery and efficiency. The performance curves of coaxial impellers are crucial for their matching characteristics as well as the system efficiency under off-design conditions. In this paper, three mean-line methods for the design of high-speed turbo-coolers are evaluated by comparing the matching characteristics of three coaxial-impellers, including the specific speed and characteristic ratio (SS-CR) approach, the power ratio (PR) approach and velocity coefficient (VC) approach. A coupling model is established to predict the off-design performance of turbo-cooler and the system size. The results show that the rotating speed and mass flow rate by all three methods lie within 2% of each other. At the design point, SS-CR approach gives 84.0% expander efficiency compared to 83.0% by PR approach and 80.9% by VC approach, but the PR approach has better performance at speeds below 35 krpm. The system volume is the lowest at the aspect ratio of 1.5 of the heat exchanger designed with all the three methods. However, SS-CR gives 6.0% advantage in system volume 5.6% over VC approach and 3.7% over PR approach. When the cooling capacity is controlled at 2000 W, SS-CR approach gives 79.3% expander efficiency compared to 78.9% by PR approach and 76.4% by VC approach.

Precise Phenotyping for Improved Crop Quality and Management in Protected Cropping: A Review

Protected cropping produces more food per land area than field-grown crops. Protected cropping includes low-tech polytunnels utilizing protective coverings, medium-tech facilities with some environmental control, and high-tech facilities such as fully automated glasshouses and indoor vertical farms. High crop productivity and quality are maintained by using environmental control systems and advanced precision phenotyping sensor technologies that were first developed for broadacre agricultural and can now be utilized for protected-cropping applications. This paper reviews the state of the global protected-cropping industry and current precision phenotyping methodology and technology that is used or can be used to advance crop productivity and quality in a protected growth environment. This review assesses various sensor technologies that can monitor and maintain microclimate parameters, as well as be used to assess plant productivity and produce quality. The adoption of precision phenotyping technologies is required for sustaining future food security and enhancing nutritional quality.

A modified discrete grey model with improved prediction performance for indoor air temperatures in laying hen houses

The accurate prediction of indoor air temperatures is vital for the timely control of thermal environments in livestock buildings. However, ensuring the accuracy of air temperature predictions is challenging due to the uncertainty introduced by external factors and periodic fluctuations. New approaches are required to improve the prediction accuracy of models for indoor air temperatures. A discrete model is developed that incorporates time-period groups (TPGs), the group buffered rolling (GBR) mechanism, and TPG factors. The measured temperature data were divided into four TPGs in chronological order, and the GBR mechanism with TPG factors eliminated fluctuations and periodicity from the time-series data. The efficacy of the proposed model was verified by comparing its results with those of two existing models (the grey model and discrete grey model) and filed experiments in layer hen houses. The traditional model only reflected the increasing trend of original air temperature data, but did not reflect periodic fluctuations. The mean absolute percentage error (APE) was >10% in the traditional model. The GBR mechanism and TPG factors allowed the new model to reflect deviations in the original time-series at each time point in real-time, thus minimizing the APE and improving the prediction performance. The modified model was superior to the traditional models, exhibited higher accuracy and reliable performance (APE < 10%), and accurately captured the periodic fluctuations in air temperature. It is a helpful tool for predicting indoor air temperatures, and may help in the development of improved control strategies for the indoor thermal environment. • A new discrete grey model modified with the group buffered rolling mechanism. • The GBR-DGM shows improved prediction performance for indoor air temperature. • Accurately predicts temporal fluctuations in air temperatures in a layer hen house. • Applications include the development of improved environmental control systems.

Cross-administrative and downscaling environmental spatial management and control system: A zoning experiment in the Yangtze River Delta, China

Promoting the downscaling and integration of zonal management and control of various environmental pollution sources is an effective way to systematically deal with the current high-intensity and complex environmental problems. Through single-factor and comprehensive pollutant emission intensity evaluation and cluster analysis, we built a full-coverage and cross-scale environmental spatial management and control system for pollution sources, then proposed environmental zoning patterns and pollution control strategies at three scales in the Yangtze River Delta (YRD), China. At the grid scale, the reclassified 7 types of pollution source spaces can be divided into 5 levels based on pollution emission intensity, and the most urgent environmental control subjects can be determined accordingly. Up to the county scale, combined with emission intensity and regional functions, 305 counties can be divided into 5 control intensity zones, which directly correspond to different environmental control intensity, requirements and policies. Finally, at the city scale, 41 cities can be clustered into 7 pollution control zones, which are classified and named as the three-level form of geographic location, development orientation and pollution source characteristics. Fully using the zoning units at different scales of cities, counties and grids can break the limitation of inherent administrative boundaries and allow environmental integration policies to be implemented across departments and regions, also let differentiated policies be more accurately implemented to different administrative levels and pollution source, and then truly improve the efficiency of environmental management.

Innovative PLF Tool to Assess Growing-Finishing Pigs’ Welfare

The main goal of the AWARTECH project (Animal Welfare Adjusted Real Time Environmental Conditions of Housing) was to develop an innovative precision livestock tool that will support and reinforce the pig value chain, through the management of solutions based on monitoring, analysis and control of environmental, physiological, behaviour and animal performances parameters. Environmental data was collected by sensors of temperature, relative humidity, air velocity and gas concentration, which are integrated in an environmental control system (Webisense) and in a platform (Nidus). Webisense controlled the ventilation system, the cooling system and the heating system. The rectal and body surface temperatures were registered manual and automatically. In order to monitor the behaviour of the animals, video cameras were installed. An individual feeding machine equipped with a scale has been also installed. This equipment allow, through an RFID system, the individual monitoring and control of the amount of food supplied and ingested; the number and duration of visits; and the animal’s weight. The development of the AWARTECH platform resulted from the integration of data provided by Webisense, Nidus, feeding machine and video analytics as well as physiological data. This platform allows the control the environmental conditions based on welfare indicators promoting animal welfare.

Moderating effect of carbon accounting systems on strategy and carbon performance: a CDP analysis

Carbon emissions bring significant risks and opportunities, and organisations have responded by adopting different strategies and environmental control systems, such as carbon accounting systems (CASs). However, it remains unclear whether a CAS can help reduce emissions, and what role is played by a CAS in the relationship between carbon strategy and carbon performance. Therefore, this paper analyses the strategy-accounting-performance nexus by drawing on 1672 firm-year observations of firms participating in the CDP in 2014 and 2015. The results suggest that the quality of a CAS is influenced by strategic choices; with a proactive carbon strategy being associated with a higher quality CAS. Further, proactive strategies and CASs are found to be associated with carbon savings and emissions reduction. The results indicate a moderating role of CASs on the strategy-performance relationship, with carbon strategy enabling higher carbon savings and lower emissions intensity in the presence of a high-quality CAS. Our findings suggest that formulation of carbon strategies and establishment of carbon measures can drive effective carbon mitigation.

Trace of Chemical Reactions Accompanied with Arrhenius Energy on Ternary Hybridity Nanofluid Past a Wedge

Heat transfer is a vital fact of daily life, engineering, and industrial mechanisms such as cryogenic systems, spaceborne thermal radiometers, electronic cooling, aircraft engine cooling, aircraft environmental control systems, etc. The addition of nanoparticles helps to stabilize the flowing of a nanofluid and keeps the symmetry of the flowing structure. Purpose: In this attempt, the effect of endothermic/exothermic chemical reactions accompanied by activation energy on a ternary hybrid nanofluid with the geometry of a wedge is taken into consideration. The mathematical form of PDEs is obtained by Navier–Stokes equations, the second law of thermodynamics, and Fick’s second law of diffusion. The geometric model is therefore described using a symmetry technique. Formulation: The MATLAB built-in Lobatto III A structure is utilized to find the computational solution of the dimensionless ODEs. All computational outcomes are presented by graphs and statistical graphs in order to check the performance of various dimensionless quantities against drag force factor and Nusselt quantity. Finding: the addition of tri-hybridizing nanomolecules in the standard liquid improves the thermic performance of the liquid much better in comparison to simple hybrid nanofluids. Wedge angle parameter α brings about a decrement in fluid velocity and augmentation in thermal conductivity ϵ, thermal radiation Rd, thermophoresis parameter Nt and endothermic/exothermic reaction Ω, and fitted rate constant n accelerates the heat transmission rate. Novelty: The effect of tri-hybridizing nanomolecules along with endothermic/exothermic reactions on the fluid past a wedge have not been investigated before in the available literature.

HEPA filters for airliner cabins: State of the art and future development.

The airliner cabin environment is very important to the health of passengers and crew members, and the use of high-efficiency particulate air (HEPA) filters for recirculated air in the environmental control systems (ECS) is essential for the removal of airborne particles such as SARS CoV-2 aerosols. A HEPA filter should be high efficiency, low-pressure drop, high dust-holding capacity (DHC), lightweight, and strong for use in aircraft. We conducted an experimental study on 23 HEPA filters with glass fiber media that are used in different commercial airliner models. The tested filters had a median filtration efficiency of >99.97% for particles with a diameter of 0.3-0.5 μm, a pressure drop of 134-412 Pa at rated airflow rate, and a DHC of 32.2-37.0 g/m2 . The use of nanofiber media instead of glass fiber media can reduce the pressure drop by 66.4%-94.3% and significantly increase the quality factor by analysis of literature data. The disadvantages of poor fire resistance and small DHC can be overcome by the use of flame-retardant polymers and fiber structural design. As a new lightweight and environmentally friendly filter material, nanofiber media could be used as air filters in ECS in the future.

Buddy System: An Adaptive Mental State Support System Based on Active Inference and Free-Energy Principles

To support a healthy human mental state, controlling the environment is one of the best-known solutions. However, it is difficult to design an environmental control system because of the uniqueness of individual preferences and mental state fluctuations. Here, we propose “Buddy system” as an adaptive mental state support solution that controls devices in the environment, depending on the recognized user’s mental state at the time and how it could be improved, serving a role similar to a “buddy” to individuals. The recognition of mental states and the locus of actions to control one’s surrounding environment are implemented on the basis of a brain-derived theory of computation known as active inference and free-energy principles, which provide biologically plausible computations for perceptions and behavior in a changing world. For the generation of actions, we modify the general calculations of active inference to adjust to individual environmental preferences. In the experiments, the Buddy system sought to maintain the participants’ concentration while a calculation task was conducted. As a result, the task performance for most of the participants was improved through the aid of the Buddy system. The results indicated that the Buddy system can adaptively support to improve the mental states of individual users.

Vulnerabilities of the Open Platform Communication Unified Architecture Protocol in Industrial Internet of Things Operation

Recently, as new threats from attackers are discovered, the damage and scale of these threats are increasing. Vulnerabilities should be identified early, and countermeasures should be implemented to solve this problem. However, there are limitations to applying the vulnerability discovery framework used in practice. Existing frameworks have limitations in terms of the analysis target. If the analysis target is abstract, it cannot be easily applied to the framework. Therefore, this study proposes a framework for vulnerability discovery and countermeasures that can be applied to any analysis target. The proposed framework includes a structural analysis to discover vulnerabilities from a scenario composition, including analysis targets. In addition, a proof of concept is conducted to derive and verify threats that can actually occur through threat modeling. In this study, the open platform communication integrated architecture used in the industrial control system and industrial Internet of Things environment was selected as an analysis target. We find 30 major threats and four vulnerabilities based on the proposed framework. As a result, the validity of malicious client attacks using certificates and DoS attack scenarios using flooding were validated, and we create countermeasures for these vulnerabilities.

Optimal design of supply chain inventory information forecasting and control system in cloud environment for biomedical instruments

With the rapid development of Internet technology, the network information data is exploding, and society has entered the era of cloud data. Cloud data provides a lot of data support for people's life and work, but because of its large number, multifarious types and huge value, there are some problems such as private data leakage and abuse of sensitive information. Stocking of biomedical material at one place only, can cause delay in sending important lifesaving material to needy patients. On the one hand, it is an important content of engineering scheduling theory and method; On the other hand, in medical field, a lot of materials are usually consumed to protect the life of patients. Biomedical informatics and computer vision techniques have been combined in a variety of inter-multidisciplinary disciplines during the past few decades. We are all aware that inadequate or insufficient cloud access management and controls can expose a corporation to a range of issues. The work that follows offers intelligent supply chain, an upgraded service management control telephone network architecture. If we can acquire according to the patient demands and retain the ideal inventory such that the patient requirement and interest can be safe, the overall cost will be lowered greatly. The experimental results show that R1 orders 31 times, and the total cost is 1,259,520 CNY. R2 ordered 24 times, with a total cost of 982,034 CNY; R3 orders 22 times, and the total cost is 990,146 CNY. Finally, the optimal solution of the total cost after schedule optimization is 3,231,700 CNY. It is proved that the optimal cost finally obtained by forecasting supply chain inventory information based on cloud data environment is also more practical for engineering practice.

Проблема разграничения компетенции федеральных и региональных органов государственного экологического контроля(надзора)

Introduction. The article is devoted to the problem of delimitation of competence for carrying out control and supervisory activities vertically – between federal and regional executive authorities that implement the function of environmental control (supervision). Theoretical analysis. The delimitation of the powers of federal and regional authorities in the field of state environmental control (supervision) is rather vague. The transfer of a large amount of such powers has led to the complication of the system of state environmental control (supervision). The objects of regional state environmental supervision are determined according to the residual principle without the mandatory fixing their list. At the same time, the legislation does not provide for the possibility of transferring the powers of regional executive authorities in the field of environmental protection to federal authorities. Empirical analysis. In practice, there is often duplication of control and supervision powers in the environmental sphere between federal executive authorities and executive authorities of the constituent entities of the Russian Federation, as well as local governments, which negatively affects their performance. In the constituent entities of the Russian Federation there are no specialized bodies exercising the implementation of the powers transferred by the Russian Federation. Results. It is concluded that there is no effective interaction between environmental control (supervision) bodies at all levels of government due to insufficient regulation of this issue in the legislation. In order to eliminate legal conflicts, simplify the interaction between subjects, the article substantiates the necessity of adoption of the Federal Law “On Environmental Control (Supervision)”; development and adoption of administrative regulations for the interaction of federal and regional environmental control (supervision) bodies; conclusion of agreements on the “reverse delegation” of powers from the executive authorities of the constituent entities of the Russian Federation to the federal bodies of state environmental control (supervision).