Electric Compressor Research Articles

Research on Intelligent Control Technology of Air Conditioning Systems for New Energy Vehicles

With the significant development of science and society at present, the relevant technologies of new energy vehicles are also constantly innovating. As an important component of vehicles, the air conditioning system should also keep up with its developing trend in terms of intelligent control technology, which can meet the reasonable requirements of users' environmentally friendly and comfortable sitting experience, as well as society's demand for energy conservation and efficiency improvement. This paper conducts research on key technologies of intelligent control systems for air conditioning of new energy vehicles. It covers four aspects: heat pump air conditioning technology; fuel cell waste heat utilization; electric compressor control technology; dedicated energy storage and system optimization. A new era of intelligent air conditioning control systems has been summarized to enhance the intelligence level of new energy vehicle air conditioning. The goal is to achieve energy conservation, and emission reduction and improve energy efficiency.

Model-Based Development of Control Strategies for a Fuel Cell Air Supply System and Experimental Verification at Flight-Relevant Conditions

The performance of hydrogen PEM fuel cell systems can be optimized by means of pressurization of the cathode air, especially in aviation, where at in-flight conditions the pressure of the ambient air is significantly lower as at on-ground conditions. To provide the inlet air at optimal conditions (p, T, rH) during flight, an air supply system is required and in an all-electric aircraft the compression should happen by means of an electric centrifugal compressor. A challenge for the operation of a pressurised fuel cell system at high altitudes is the control of the compression system. Any unstable operation like compressor surge has to be avoided, since it can damage both the fuel cell stack and the compressor itself. For the development of such an air supply system, a combined experimental and modeling approach was chosen.A hydrogen PEM fuel cell system was characterized at nominal and at low cathode pressures to obtain the behavior at flight relevant conditions and an experimental air supply system containing electric compressor, intercooler, humidifier, cathode volume and throttle valve at the outlet has been set up and used for the development, parameterization, and validation of a model for the compression system. The model is based on the Greitzer model 1,2, and has been extended to also represent the additional components between the compressor and the throttle valve (intercooler, humidifier, and cathode volume) 3. It is now able to predict the transient response of the entire air supply system to changes in the reference values of compressor speed and valve opening angle and the resulting mass flow changes and pressures within the individual components.The model and the data from the fuel cell system were used for the development of improved control strategies, that make it possible to operate the system safely in a wide range of operating conditions. Unstable situations, like compressor surge, are avoided by these control strategies even in the highly varying conditions during a flight. The developed control strategies are verified on the hardware of the experimental setup and tested under realistic flight conditions in a low-pressure climate chamber.References Greitzer, E. M. Surge and Rotating Stall in Axial Flow Compressors—Part I: Theoretical Compression System Model. Journal of Engineering for Power 98, 190–198 (1976).Gravdahl, J. T. & Egeland, O. Compressor Surge and Rotating Stall. (Springer London, London, 1999). doi:10.1007/978-1-4471-0827-6.Frank, D., Bauer, C. & Willich, C. Modeling of the cathode air supply for a pressurized hydrogen fuel cell system in airborne applications. Proceedings of the Aerospace Europe Conference 2023 (2023) doi:10.13009/EUCASS2023-218.

Target setting and practical Improvement for sound quality of electric vehicles

For electric vehicles, because there is no masking effect of combustion engine noise, the middle frequency and high frequency noise of electric components become distinct and annoying. Electric driven unit, electric compressor, electric pump, and motors of seat adjusting device are always major noise sources for electric vehicles. Some of those noise signals are steady, some are transient and some are time-variable. So only SPL is hard to reflect human's true perception. Psychoacoustic metrics, such as loudness, roughness, sharpness, and tonality, is hard to evaluate all complicated NVH phenomenon of electric vehicles using one metrics. In this paper, the author tested different operation noises of above-mentioned electric components of several popular EVs, and finalized proper psychoacoustic metrics for different operations based on loudness, modulation, tonality and objective evaluation. Furthermore, the author studied target setting for dedicated metrics, and effective improving methods for sound quality of EVs from the point of source and path. For example, effective designing for acoustic encapsulation of EDU and electric compressor, and good insulation performance designing for dash inner and trunk floor trim. Keywords: Sound quality, Psychoacoustic metrics, electric vehicle, objective evaluation, target setting

Use of an Absorption Heat Pump to Lift the District Cooling Waste Heat Temperature for the District Heating Supply in Tallinn: a Technical and Economic Analysis

Absorption heat pumps can lift a lower temperature waste heat source to a higher temperature useful output. In that process, it uses less electricity as an input compared to heat pumps with electrical compressors. Therefore, in some cases, it can be used to lift a lower temperature waste heat source to a higher temperature useful output with less electricity consumption. Absorption heat pumps are not very widely spread in district heating, mostly because there aren’t many suitable waste heat sources or conditions needed to run them. Tallinn has a district heating system with an annual generation of more than 2 TWh and a goal to make it an entirely carbon neutral district heating system by 2030. Tallinn has also started to develop a district cooling network, and by the end of 2023, the installed capacity was about 6 MW. District cooling capacity is estimated to grow to around 100 MW in 2030. This paper investigates different types of absorption heat pumps and the possibilities of integrating an absorption heat pump to a district cooling plant with the purpose of using waste heat from the cooling plant for renewable heat generation, that can be used in district heating. Different technical aspects are examined to find a suitable production solution, are presented as results. From an economical point of view, the cost of heat to cover peaks with an absorption heat pump is calculated. The effect of reducing fossil fuel use in the Tallinn district heating network with an absorption heat pump is estimated.

Hardware simulator of DC–AC inverters for electric compressors

Hardware simulator of DC–AC inverters for electric compressors

LQTI boost pressure and EGR rate control of a diesel air charge system with eBoost assistance

Turbocharged diesel engines often suffer significant response delay due to so-called turbo-lag, especially engines with large displacement. For this reason, many technologies have been developed to reduce turbo-lag. This paper develops a coordinated control strategy for a diesel engine equipped with an eBoost (electrical compressor) system to significantly reduce turbo-lag. A multiple-input and multiple-output (MIMO) Linear Quadratic Tracking with Integral (LQTI) control strategy, along with its scheduling logic, is developed for the Ford 6.7 L 8-cylinder diesel engine equipped with a variable geometry turbocharger (VGT), exhaust gas recirculation (EGR), and added eBoost along with a bypass valve. Note that the existing production engine does not have an eBoost and bypass valve. Multiple model-based LQTI controllers were designed at different engine operational conditions based on the associated linearized models, and the control outputs are scheduled based upon the engine load condition and bypass valve position. The developed control strategy is validated in both simulation and experimental studies, and the test results show a reduction in engine response time by up to 81.36% in terms of reaching target intake manifold (boost) pressure following a load step-up, compared with the production configuration (without eBoost and bypass valve) with no significant impact on NOx emissions.

Optimal operating conditions for an electric ECS in ground parking status

The Electric Environmental Control System (EECS), which uses an electric compressor to draw in outside air instead of the engine bleed, is under consideration. In this study, the case of EECS operating in a grounded parking status is discussed. The pressure ratios for the electric compressor and the air cycle machine compressor are set as variable parameters. A thermodynamic analysis is performed to clarify the operating conditions of the system, taking dehumidification into account. The coefficient of performance is obtained, and it is found that the maximum value is obtained under the condition where the pressure ratio of the electric compressor is the smallest.

Effect Of AC Compressor Modification on Fuel Consumption in Car

The cooling system is a refrigeration technology that is growing, especially regarding the cooling medium (refrigerant), new vehicles nowadays mostly use air conditioning to condition the air in the vehicle's cabin, but for now, there are still many aspects that have not been given much attention, especially the compressor. Compressor systems in vehicles still rely on the engine as a direct drive resulting in increasingly wasteful fuel consumption and reducing the performance of the vehicle. This study analyzes the results of modifying a conventional compressor into an electric compressor by utilizing a split AC compressor whose supply voltage is obtained from a DC to AC inverter on vehicle fuel consumption and the required electrical energy. Inverter modification is highly recommended in the application of car air conditioners, split AC compressors, and others. The results of this research show that AC compressors using split compressors affect fuel consumption.

Performance analysis of automotive air conditioning systems with electric compressors using R1234yf refrigerant: Insights into power consumption, cooling capacity, and energy efficiency

R1234yf, a low global warming potential (GWP) refrigerant, offers a promising alternative to traditional refrigerants like R134a. This study analyzes automotive air conditioning systems (AAC) equipped with electric compressors and utilizing R1234yf refrigerant. The interrelationships between refrigerant charge, compressor speed, power consumption, cooling capacity, and energy efficiency are examined. The results show that increasing refrigerant charge and compressor speed leads to higher power consumption due to increased compressor work. However, higher refrigerant charges and compressor speeds improve cooling capacity in line with heat transfer principles. As refrigerant charge and compressor speed increase, the energy efficiency, measured by the Coefficient of Performance (COP), tends to decrease, indicating a trade-off between cooling capacity and energy efficiency. Optimizing refrigerant charge and compressor speed is crucial to strike a balance between cooling performance and energy efficiency. R134a outperforms R1234yf, with an average percent difference in COP approximately 25% higher at all compressor speeds. This study contributes to the understanding of AAC system performance and guides the development of energy-efficient automotive air conditioning. Future research can further explore system components and conditions to enhance energy efficiency and advance air conditioning technology.

Analysis of interference of electromagnetic noise in an electric compressor for vehicle air‐conditioning systems with an integrated mechanical and electrical structure

AbstractSince a motor drive system contains an inverter (high‐voltage circuit) and gate drive circuits (low‐voltage circit) with a switching regulator, electromagnetic noise is generated in each of these two circuits, and noise interference between these circuits can occur. This paper discusses noise interference between the high‐ and low‐voltage circuits of an electric compressor system with an integrated mechanical and electrical structure. Analysis using LTspice shows that the experimental and analytical results are in good agreement when a very small stray capacitance occurs between the high‐ and low‐voltage circuits. An experiment using an actual compressor showed that conducted noise above 20 MHz can be reduced by up to 10 dB by reducing the effect of stray capacitance between these circuits.

Accelerated Degradation Test on Electric Scroll Compressor Using Controlled Continuous Liquid Slugging

Refrigerant-based electric scroll compressors are known for their reliability, efficiency, and quiet operation. They are often used in heat pump systems due to their ability to efficiently handle varying levels of load conditions, both for heating and cooling modes of operation. As electric compressors are considered the heart of the heat pump system, being able to determine degradation of compressors prior to failure is of paramount importance for the health of this system. Typical failures for electric scroll compressors range from electrical faults, refrigerant leaks, to mechanical failures and overheating. Specifically, one of the primary failure modes for an electric scroll compressor is mechanical damage due to the high stress effects of refrigerant liquid slugging. These stresses are due to excessively high internal pressures exhibited on the compressor scrolls, which are generated by compressing liquid refrigerant at the suction side of the compressor. This paper provides a new testing methodology that introduces liquid slugging at various degrees of refrigerant quality to degrade a compressor to near the end of useful life. Furthermore, this test aims to determine specific operating conditions and signals that can indicate early compressor degradation. This fault injection configuration consists of a modified heat pump system with the addition of two low pressure heat exchangers added in parallel (with respective electronically controlled expansion valve for each heat exchanger) used to control the refrigerant quality during compressor operations. For a given refrigerant quality, the heat pump system was operated at a fixed compressor performance conditions to sustain liquid slugging for a fixed duration. Afterwards, refrigerant was controlled to be pure vapor at the compressor suction side and the compressor was controlled at several different performance conditions (i.e., fixed compressor suction superheat temperature and compressor pressure ratios, at various compressor speeds), so as to duplicate conditions known to us from the compressor component data sheet for an ideal electric scroll compressor. Through these tests, the results show that the severity of scroll failures depend heavily on the refrigerant quality and the amount of liquid slugging exposure time. Furthermore, symptoms of compressor degradation are detected using the following signals: i) temperature and pressure at the compressor suction side, ii) temperature and pressure at the compressor discharge side, and iii) electric compressor speed and power consumption. To further aid in determining the compressor degradation ground truth, complete compressor teardown was performed to identify sections within the compressor that exhibited significant amounts of wear as compared to a stock compressor.

Determining the Mechanical Power of the Air Conditioning Compressor

Generate mechanical power with low cost and less emissions is great challenge for mechanical engineers overall the world in our contemporary time. Mechanical power is the main reason for excessive fuel consumption and increased CO2 emissions problems as compensation from the overlay of air conditioning systems. Therefore, this article presents various methods to overcome the problem. Ways to find new different resources for the mechanical energy reduce fuel consumption and reduce CO2 emissions are achieved through the application of VCC and an absorption system. This study also deals with Alternative control methods for air conditioning systems such as electric compressors and shows power consumption as a function of speed of a conventional compressor and an electric compressor. As a result, it turned out that the electric compressor consumes less power compared to a conventional compressor by up to 18%. This is because there is less load on the car coming from the compressor and energy efficiency is improved. Increasing the internal heat load will increase the fuel supply to both systems.

Nonlinear model predictive control for efficient and robust airpath management in fuel cell vehicles

The fuel cell airpath multivariable control problem of optimally coordinating the electric compressor motor and the back-pressure valve to achieve efficient and safe conditions, for both steady state and transient operation, has not been completely addressed in the literature. This paper proposes a nonlinear model predictive control strategy, implemented via the Garrett Motion proprietary NMPC toolbox, to regulate the oxygen stoichiometry and the cathode pressure of an automotive fuel cell airpath system, while avoiding compressor surge and air starvation. The controller set-points are optimized, using the nonlinear model, to achieve the maximum system power as a function of the operating stack condition. The effectiveness and robustness of the proposed control strategy have been validated by means of a simulated World harmonized Light-duty vehicles Test Cycle (WLTC), under both state feedback and model parameters uncertainties.

Optimization of the air loop system in a hydrogen fuel cell for vehicle application

Hydrogen fuel cells are a potential route to decarbonize the automotive sector due to the zero CO2 tailpipe emissions, faster re-fuelling, and higher energy density than their direct competitor, the battery-electric powertrain. One of the key challenges is to find the best air path configuration to achieve high efficiency in a system level. This work aims to optimize, setup, and demonstrate a highly efficient Proton Exchange Membrane fuel cell system (PEMFC). This powerplant is hydrogen fuelled and scalable to achieve the required power output for different vehicles. This work evaluates a PEMFC by a 1D-numerical approach. The fuel cell is modelled, validated, and later studied under different air inlet conditions. The main goal is the evaluation of different air path layouts to achieve the highest system efficiency. Numerical simulations of electric compressor and coupled and de-coupled electrically assisted turbocharging are performed with different component sizes and cathode pressures. Therefore, this work provides an overview of our initial findings that will outline the key modelling challenges for fuel cell systems and then present a comparison of different air-path architectures. The coupled electrically assisted turbocharger is determined to be the best layout with an improvement of 10% of the delivered power at a high current load. The e-turbocharging optimized by the proposed methodology allows reduction of the peak electric machine electric power by 60%.

How vulnerable are US natural gas pipelines to electric outages?

Gas-electric interdependencies have contributed to several major electric system emergencies. Natural gas pipelines use both gas-powered and electric-powered compressor units; power outages at the latter can cause gas shortages. We make the first rigorous identification of the number of US electric compressor stations, finding that 10% are electric. California, the Midwest, the Gulf Coast, and the East have high installed electric compressor capacity. New hydraulic models, verified by past events, show that disrupting power to a single compressor station can force a loss greater than 2 GW of downstream gas generators. Such an outage can be larger than the most severe single-cause failure currently considered in electric reliability planning. Electric utilities should immediately incorporate the identified facilities into critical facility lists. Establishing a federal gas reliability organization, comparable to what is now done for electric power, could improve gas reliability by establishing appropriate reliability reporting, incident investigation, and minimum industry standards.

Dual-output PID transient control of an electric-assisted air charge system

Turbo-compressor assembly (also called turbocharger) is added to diesel engines to increase their power density and improve performance. However, during power step-up operations, the added turbocharger system could lead to a significant delay of engine response (also called turbo-lag) which negatively impact drivability. In this paper, an external electric compressor (eBoost) is added to a turbocharged, large displacement diesel engine to significantly reduce turbo-lag, along with a bypass valve. Now, the air charge system has two control targets (boost (intake manifold) pressure and rate of exhaust-gas recirculation (EGR)) but with four control actuators including EGR valve, variable geometry turbo (VGT) vane position, eBoost speed and bypass valve, making it challenge for developing the associated control scheme. In this paper, a dual-output PID (proportional-integral-derivative) controller is proposed for controlling the boost pressure using the VGT and eBoost to reduce turbo-lag, and a transition logic is also devised to detect transient operating conditions to activate the eBoost, along with the closing and opening of the bypass valve, with maximum benefit. The EGR rate PID control remains unchanged. The addition of the eBoost is shown to improve transient response time by up to 55% and reduce transient NOx emissions by up to 42% during transitional operations without negatively impacting steady-state engine performance or emissions. Note that transient performance can be further improved for production implementation when a single engine control module is used by eliminating communication delay among multiple control systems.

Development of an Air Electric Compressor for a No-Bleed Environmental Control System of an Advanced Regional Aircraft

BACKGROUND: Aircraft designers strive to increase the fuel efficiency of aircrafts, including increasing the efficiency of aviation environmental control systems (ECS) by introducing an autonomous source of compressed air with an electric drive as part of aircraft.
 AIM: The present paper aimed to consideration of the results of research work (RD) of the technologies demonstrator for the electric compressor of the aircraft electric ECS and estimation of the performance and compliance of the simulated and experimental characteristics of this electric compressor.
 MATERIALS AND METHODS: Comparison of the simulated and experimental characteristics of the electric compressor of the electric ECS of the aircraft was carried out by confirming the compliance of the operating parameters of the technologies demonstrator for the electric compressor with those specified in the request for proposals (RFP), and by comparing the simulated and experimental values of the compression ratio of the compressor stage, isentropic coefficient of performance (COP), obtained during RD study.
 RESULTS: Information about the technical characteristics and design of the electric compressor is given and discussed. A comparative analysis of the presented simulated and experimental characteristics of the electric compressor has been carried out.
 CONCLUSIONS: Conclusions are drawn on the compliance of the compressor characteristics with the characteristics specified in the RFP; on the achieved level of readiness of the technology of the electric compressor for the electric ECS of the aircraft, on the need for experimental design work on the electric compressor, taking account of external influencing factors typical for an application as part of aviation equipment.

Thermodynamic analysis of power recovery of marine diesel engine under high exhaust backpressure by additional electrically driven compressor

Marine diesel engines can be exposed to high backpressure conditions, because various aftertreatment systems and waste heat recovery devices have been applied to reduce emissions and some exhaust outlets are below sea level. The engine performance deteriorates sharply under high backpressure. This paper aims to study power recovery method under high backpressure based on thermodynamic analysis. Firstly, thermodynamic model is established and validated by experimental data. Next, effects of turbocharger efficiency and turbine area on power recovery are studied. The results show that feasible turbine performance are limitations for power recovery. If energy of compressor can be increased without changing turbine area, limitations can be overcome. Thirdly, additional electrically driven compressor as a solution is proposed to recover engine power. A comparative study of different electrically driven compressor schemes is carried out. The most suitable scheme is the series scheme at low-pressure stage because operating points for original compressor and electrically driven compressor are within a reasonable range. Finally, research on power recovery is carried out on optimal electric compressor scheme. The results show that when backpressure is 0.65 bar, engine net power can be increased by 49.4% and exhaust temperature drops by about 77 K, which largely reduces turbine thermal load.

Analysis of Modification of Car AC Compressor to Split AC Compressor on Cooling Rate

Refrigeration or cooling technology is increasing, especially regarding the coolant, almost all new vehicles now use air conditioning to condition the air in the vehicle cabin, but there are still many aspects that currently have not been paid much attention, especially to compressors, compressors for now still rely on the engine as a direct driver which makes fuel consumption more wasteful and reduces the performance of the vehicle. The purpose of this research is to modify a conventional compressor into an electric compressor by utilizing a split ac compressor. The research method uses the direct experimental method, can a split ac compressor replace a conventional compressor. Testing without changing a lot of the cooling system on the car, only changing the compressor without any other changes. The results of the research on split ac compressors can be applied to cars, but the cooling rate is slower than car ac compressors.

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.