Rotational Speed Of Compressor Research Articles

A Reduced Complexity Model for the Compressor Power of an Automotive Turbocharger

Control-oriented models for automotive turbocharger (TC) compressors typically describe the compressor power assuming an isentropic thermodynamic process with fixed isentropic and mechanical efficiencies for power transmission between the turbine and the compressor. Although these simplifications make the control-oriented model tractable, they also introduce additional errors due to unmodeled dynamics. This is especially true for map-based approaches since the manufacture-provided maps tend to be sparse and often incomplete at the operational boundaries, especially at operational conditions with low mass flow rate and low speed. Extrapolation scheme is often used when the compressor is operated outside the mapped regions, which introduces additional errors. Furthermore, the manufacture-provided compressor maps, based on steady-flow bench tests, could be quite different from those under pulsating engine flow. In this paper, a physics-based model of compressor power is developed using Euler equations for turbomachinery, where the mass flow rate and the compressor rotational speed are used as model inputs. Two new coefficients, speed and power coefficients, are defined. As a result, this makes it possible to directly estimate the compressor power over the entire compressor operational range based on a single analytic relationship. The proposed modeling approach is validated against test data from standard TC flow bench tests, standard supercharger tests, steady-state, and certain transient engine dynamometer tests. Model validation results show that the proposed model has acceptable accuracy for model-based control design and also reduces the dimension of the parameter space typically needed to model compressor dynamics.

Exergy assessment of a refrigeration plant using computational intelligence based on hybrid learning methods

In this study, a method to model the exergetic behavior of a refrigeration system using some techniques from computational intelligence is proposed. The input parameters of the model are: the compressor rotation speed, the volumetric flow rates and the temperatures of the secondary fluids. The artificial neural network was trained using a hybrid learning method based on Simulated Annealing and Levenberg Marquardt method. Two independent neural networks were designed to visualize and analyze the exergy destruction and exergy efficiency for each component of a vapor compression system. The relative errors produced during the validation of the model were within ±10%. From the application simulation, it was concluded that the major exergy destruction is located at the compressor and at the condenser. Additionally, it was observed that the parameters that most influence the exergetic behavior of the system are: the compressor rotation speed and the inlet temperatures of the secondary fluids.

Operational Optimization of a Typical micro Gas Turbine

Micro Gas Turbines (mGTs) offer great potential for use in co-, tri or polygeneration applications. In these applications, where the heat from the exhaust gases is used in an efficient way, the mGTs achieve very high efficiencies. To be able to determine the number of units, the nominal parameters of the units and the specific operating strategy of the mGT, it is key to know precisely the performance of these units. Generally in co-, tri- or polygeneration applications with mGTs, this performance is considered to be known and fixed, and is therefore directly used to determine the operational strategy of the network, possibly linked with an economic analysis. In real world operating conditions, the parameters characterizing the operation of the mGT are measured with uncertainties. Depending on the model sensitivity to input parameters, these uncertainties may have a tremendous effect on the performance of the mGT. These uncertainties should be taken into consideration by the designers in an early stage of the design process to achieve a so-called robust design. In this paper, we present the operational optimization of a typical mGT, the Turbec T100 mGT, using a deterministic approach. In this approach, the parameter uncertainties are not taken into account, however, it is an important first step towards a full robust design, since it will set the reference. By varying Turbine Outlet Temperature (TOT) and compressor rotational speed, a Pareto front for maximal electrical power output and electrical efficiency is found. The two objectives are conflicting, making that the maximal electrical efficiency cannot be reached at maximal electrical power output. The results of this optimization will be used in our future study on the design optimization under uncertainties.

Influence of Refrigerant Charge Amount and EEV Opening on the Performance of a Transcritical CO2 Heat Pump Water Heater

Besides compressor rotary speed and parameters of water flowing through gas cooler and evaporator, refrigerant charge amount and electronic expansion valve (EEV) opening are two important parameters that have significant effects on the performance of a transcritical CO2 heat pump system. In this study, the effects of refrigerant charge amount on the performance of a transcritical CO2 heat pump water heater were investigated experimentally at different EEV openings. An optimal coefficient of performance (COP) was found that corresponded to a specific refrigerant charge and a specific EEV opening. Based on the experiment, the COP peaked at charge of 1.8 kg when EEV opening was 40% of full opening. The heating capacity and the COP increased at first, reached peaks and then decreased with increase of charge amount. The COP decreased 14.95% as the CO2 charge amount was reduced by 22.2% from the optimal charge at 50% EEV opening. As EEV opening varied from 40% to 60% at the same charge amount, the heating capacity decreased more than 30%.

An experimental investigation of internal heat transfer in an automotive turbocharger compressor

An experimental investigation developed on a small turbocharger compressor for automotive application is presented. The study focuses on the effects of internal heat transfer on compressor efficiency, evaluated for different values of inlet pressure, mass flow rate and compressor rotational speed. Infrared thermography has been used to evaluate the heat transfer rate from the turbine to the compressor and to correct the measured compressor diabatic efficiency. The approach has been validated by performing additional measurements under quasi-adiabatic conditions, avoiding map distortion due to heat transfer. Simple relationships for the prediction of internal heat transfer, validated against the measured values, have been proposed. The practical significance of the results, with reference to turbocharger compressor performance, is outlined.

Experimental evaluation of system modifications to increase R1234ze(E) cooling capacity

The GWP limitations are being progressively introduced in Europe through Regulation EU No 517/201, phasing out R134a in most of its refrigeration and air conditioning applications. Pure hydrofluoroolefins are proposed to substitute this fluid, however generally system modifications are needed to achieve a good performance. In the case of R1234ze(E), the cooling capacity is always much below that of R134a in drop-in or light retrofit substitutions.This work performs an experimental comparison using R1234ze(E) and R134a under different refrigeration operating conditions. R1234ze(E) is tested considering the use or not of an internal heat exchanger, and R134a at the same or lower compressor rotation speed. Results show that the use of R1234ze(E) with an open-type compressor 43% larger and an internal heat exchanger of 25% effectiveness, leads to a cooling capacity augmentation, enough to reach R134a cooling capacity in the different conditions tested. For R450A, it is sufficient only with the IHX activation.

Comparative evaluation of R1234yf, R1234ze(E) and R450A as alternatives to R134a in a variable speed reciprocating compressor

A comparative energetic evaluation of R1234yf, R1234ze(E) and R450A as alternatives to R134a in a variable speed compressor is carried out. A compressor model based on dimensionless numbers was obtained using the Buckingham π-theorem, which was validated with experimental data; showing that the prediction error of the model is lower than ±10% and ±2 K for temperature. The experimental data were obtained by testing R134a, R1234yf, R1234ze(E) and R450A for a wide range of operating conditions. Results obtained with the validated model, show that the dimensionless approach provides a similar estimation of energy parameters compared with the experimental results, such as power consumption, refrigerant mass flow rate, cooling capacity, COP, discharge temperature and compressor efficiencies for each refrigerant tested using the dimensionless approach proposed. The comparative evaluation of the compressor predictions shows a reduction in the cooling capacity obtained with R1234yf, R450A and R1234ze(E), in comparison with R134a. Also, COP values for R1234yf, R450A, and R1234ze(E) are lower than those obtained from R134a. Finally, results shows that the dimensionless correlation compressor model can be used to predict the performance of other reciprocating compressors, at similar operating conditions for a wide range of compressor rotation speed, with a reasonable accuracy.

Numerical simulation and experimental investigation on suction heating of a BOG compressor

One of the key components of a liquefied natural gas (LNG) receiving terminal is the boil-off gas (BOG) compressor, which is used to pump out the BOG from the LNG storage tank to ensure safety in the transportation and receiving systems. Owing to the ultra-low suction temperature, the heat exchange between the intake gas and the cylinder, piston, and cylinder cover cannot be ignored as in normal conditions. This paper presents an investigation focusing on suction heating of the BOG compressor. A finite element model with dynamic mesh was established to simulate the suction process. At the same time, a performance test rig was built to study the characteristics of the BOG compressor under low suction temperature conditions and verify the numerical model. Consequently, the results of the simulation were in good agreement with experimental results. Both results implied that the temperature of cylinder surface increased starting from the cylinder cover to the crankcase. In addition, at lower suction temperature, the temperature difference between various points on the cylinder surface and cylinder cover was much larger than that at higher suction temperature. With increasing suction temperature, the temperature coefficient increased markedly, and the difference between gas temperatures at the beginning and end of the suction process, as well as the compressor flow rate, decreased significantly; however, the volumetric efficiency increased first and then decreased. Furthermore, the temperature coefficient clearly increased when the compressor rotational speed increased from 250rpm to 3000rpm, and it decreased from 0.81 to 0.66 as the pressure ratio increased from 3.0 to 6.0.

Virtual test bench as a complement to study thermal area application in vapor compression systems

This paper describes an educational simulator developed in the software Engineering Equation Solver to simulate the behavior of a vapor compression system. The application is focused on educational purposes, specifi cally for handling skills in refrigeration facilities by students in engineering careers. Using this simulator, the students are able to analyze easily the infl uence of the measured parameters (such as the compressor rotation speed, volumetric fl ow rates and temperature of the secondary fl uids) on the energy performance of the facility and its components. The virtual test bench consists of a primary screen showing a general scheme of the vapor compression facility with input and output parameters. From this primary screen, the performance of the main components can be analyzed. Finally, this virtual test bench was tested by engineering students, concluding that the simulator is an interesting tool as improvement and support for learning in different subjects.

Development of a water-injected twin-screw compressor for mechanical vapor compression desalination systems

The water-injected twin-screw compressor is a key component in the mechanical vapor compression (MVC) desalination system, which is a promising technology for small and medium scale water production. This paper presents an experimental study on a water-injected twin-screw compressor. A prototype is developed and applied in a 50 m3/day double-effect MVC system. The effect of important parameters (including compressor rotation speed, water injection flow rate and compressor inlet temperature) on the compressor performance is experimentally investigated. It is found that the volumetric flow rate and power consumption of the compressor increases almost linearly with the rise in compressor rotation speed. Results also show that the compressor inlet temperature only affects the power consumption of the twin-screw compressor. It has minor effect on the volumetric flow rate, and volumetric and isentropic efficiencies of the compressor. Study further shows that water injection substantially reduces the compressor discharge temperature. As the water injection flow rate increases, the vapor compression process more closely approaches saturation vapor compression and hence the isentropic efficiency of the twin-screw compressor increases. The analyses demonstrate that the water-injected twin-screw compressor can be reliably operated in the MVC system with satisfactory system performance.

Minimization of Power Usage in a Compressor Station with Multiple Compressors

AbstractIn natural-gas transmission, a compressor station often consists of multiple types of compressors. For any given suction pressure, discharge pressure, and total mass flow, an operation manager needs to decide the set of compressors to work, the rotation speed of each working compressor, and the natural-gas flow allocation among all the working compressors. In this paper, two solution approaches are investigated and compared: mixed-integer linear programming and dynamic programming. Both approaches require the discretization of actual volumetric flow. Numerical results reveal that when the discrete interval is 0.1 m3/s, dynamic programming takes less computation time than mixed-integer linear programming does. However, this order is reversed when the discrete interval is 0.01 or 0.001 m3/s.

Experimental study on the heat pump system using R134a refrigerant for zero-emission vehicles

The aim of this paper is to investigate the possibility of using an R-134a heat pump system with a conventional air-conditioning system for zero-emission vehicles. A heat pump system is one solution to heating the cabin and defrosting the windshield while consuming little energy. The system components consist of an internal heat exchanger, external heat exchanger, electrically driven compressor, electric expansion valve, and refrigerant flow change valves. Cooling capacity was examined by varying vehicle driving conditions and the compressor’s rotational speed. Heating performance for the heat pump system was investigated with various outside air temperatures and compressor rotational speeds. The experimental results using a heat pump system could provide thermal comfort in the cabin with smaller energy consumption than a direct electrical heating system. Heating capacity and air discharge temperature are up to 4.9 kW and 41.7°C, respectively, at an outside air temperature of 0°C and 7000 rpm compressor rotational speed. The power consumption of the heat pump system is about one third that of the electric PTC heating system at the same heating capacity.

A comparison between the modeling of a reciprocating compressor using artificial neural network and physical model

This article presents the development, validation, and comparison of two methods for modeling a reciprocating compressor. Initially, the physical mode is based on eight internal sub-processes that incorporate infinitesimal displacements according to the piston movement. Next, the analysis and modeling of the compressor through the application of artificial neural networks are presented. The input variables are: suction pressure, suction temperature, discharge pressure, and compressor rotation speed. The output parameters are: refrigerant mass flow rate, discharge temperature, and energy consumption. Both models are validated with experimental data for the refrigerants R1234yf and R134a; computer simulations show that mean relative errors are below ±10% with the physical model, and below ±1% when artificial neural networks are used. Additionally, the performance of the models is evaluated through the computation of the squared absolute error. Finally, these models are used to compute an energy comparison between both refrigerants.

Statistical analysis of the energy performance of a refrigeration system working with R1234yf using artificial neural networks

This paper presents the application of an artificial neural network to carry out a statistical analysis of the energy performance for a compression vapor system operating with R1234yf as working fluid. The main contribution of this work is the creation of 3D plots for visualization of energy performance and its variability when changes in the input operating parameters are present. These parameters are: compressor rotation speed, the temperature and volumetric flow of the secondary fluids.Furthermore, frequency histograms to represent the variability of the energy performance of the refrigeration system were estimated and analyzed. Computer simulations employing neural networks were used to understand the energy performance behavior, and observe the best performance of the installation. In the same way, these simulations were used to statistically analyze the variability of the energy performance.

Development and experimental study of the characteristics of a prototype miniature vapor compression refrigerator

This paper develops a practical miniature and portable vapor compression refrigerator. The dimensions of the refrigerator are 190mm×190mm×100mm and its weight is 2.75kg. It integrates a miniature variable speed rotary compressor with a miniature electronic expansion valve (EXV) operating in pulse width modulation (PWM) mode. Besides, a new type of miniature microchannel plate-fin evaporator is developed with vacuum bonding technology and a brazed aluminum parallel flow microchannel condenser is applied. Experiments are conducted to explore the operating performance of the prototype miniature refrigerator, especially the effects of EXV duty cycle and working conditions on the cooling performance. Experiments find that the operation of the system is smooth and reliable; the results show that it has a cooling capacity of 260W which is high enough for cooling one person with moderate working load, where the ambient temperature is as high as 50°C and the inlet cold water temperature of the evaporator is 24°C, respectively. Under these operation conditions, the system COP can reach 1.62 and the reversible efficiency is 0.324.

고이득 관측기가 적용된 터보제트엔진의 인공신경망 PID 제어기 설계

In this paper, controller propose to prevent compressor surge and improve the transient response of the fuel flow control system of turbojet engine. Turbojet engine controller is designed by applying Artificial Neural Network PID control algorithm and make an inference by applying Levenberg-Marquartdt Error Back Propagation Algorithm. Artificial Neural Network inference results are used as the fuel flow control inputs to prevent compressor surge and flame-out for turbojet engine for UAV. High Gain Observer is used to estimate to compressor rotation speed of turbojet engine. Using MATLAB to perform computer simulations verified the performance of the proposed controller. Response characteristics pursuant to the gain were analyzed by simulation.

Performance optimization of a cascade multi-functional heat pump in various operation modes

A multi-heat pump has been widely used to provide cooling and heating in a building. In addition, the demands for a cascade heat pump water heater have been increased due to its higher energy efficiency with high water temperature. In this study, a cascade multi-functional heat pump, which combines a multi-heat pump using R410A for air heating and cooling with a cascade heat pump using R134a for water heating, is considered to provide simultaneous air heating, air cooling, and water heating in a building. The performance of the cascade multi-functional heat pump was measured and analyzed in four operation modes: full-heating hot water, heating-main hot water, full-cooling hot water, and cooling-main hot water. The performance of the cascade multi-functional heat pump in each of the four operation modes was optimized by adjusting control parameters such as the compressor rotation speed and EEV opening and by modifying the refrigerant flow path.

항공전자기기용 냉각시스템의 대체냉매 적용에 관한 실험적 연구

항공전자기기의 정상적인 동작을 위해서는 내부에서 발생되는 열부하를 적절히 처리해야 하기 때문에 냉각시스템의 장착이 요구된다. 본 연구에서는 항공용 냉각시스템으로의 대체냉매 적용 가능성을 분석하기 위하여 증기압축 사이클 방식의 밀폐 공기순환 냉각시스템을 설계·제작하였다. 대체냉매로 가장 유력한 R236fa를 냉각시스템에 적용하여 냉매 충전량, 팽창밸브 개도, 그리고 압축기 운전회전수 변화에 따른 성능특성을 실험적으로 고찰하였다. 또한, 실험결과를 기존 냉매인 R124의 실험결과와 비교·평가를 수행하여, R236fa가 대체냉매로서 적용 가능함을 확인하였다. 최종적으로 R236fa를 적용한 냉각시스템의 효율 향상을 위한 설계 개선안을 제시하였다.

Dynamic analyses for the rotor-journal bearing system of a variable speed rotary compressor

In the rotary compressor, the rolling piston and the contacted rotor-journal bearing system are main moving components. They suffer very large periodically varying loads introduced by the inertia force, the contact force and the gas force. These loads change rapidly with speed variation of the compressor. They always lead to serious vibration of the system, and then result in abrasion and performance reduction. In this paper, the dynamic behavior of the rotor-journal bearing system were calculated by solving three-dimensional numerical model using finite element method, and the vibration characteristics of the system were investigated according to the calculation results. The natural frequencies and vibration modes were obtained. The stress, displacement and axis orbit of the rotor center were calculated considering the speed variation of the motor. Via the established numerical model, vibration characteristics of a newly designed compressor can be predicted, and optimization can be done to reduce the vibration.

Experimental investigation on the scroll refrigeration compressor with external cooling

To improve the performance of scroll refrigeration compressor, an external cooling structure scroll compressor was designed and researched. A prototype with cooling structure was developed and tested. The thermodynamic model including the leakage, heat transfer, and friction was set up to simulate the working process of scroll compressor with external cooling. Experimental results show that coefficient of performance value of the prototype is improved by 0.31, the cooling capacity increases by 1281 W (12.9 per cent) and the discharge temperature reduces by 44 °C (41 per cent) maximally when the water cooling is used. Increasing the water flowrate improves the volumetric efficiency and enhances the heat transfer between water and scroll compressor. When the rotational speed of compressor goes up, the volumetric efficiency increases remarkably while the quantity of heat transfer rises slowly. The simulated results have good coincidence with the experimental ones.