Compressor Outlet Research Articles

Mathematical model of turbofan engine weight estimation taking into account the engine configuration and size

The paper presents a new correlation-regression model of estimating the turbofan engine weight considering the effect of the engines design schemes and dimensions. The purpose of this study was to improve the efficiency of the conceptual design process for aircraft gas turbine engines. Information on 183 modern turbofan engines was gathered using the available sources: publications, official websites, reference books etc. The statistic information included the values of the total engine air flow, the total turbine inlet gas temperature, the overall pressure ratio and the bypass ratio, as well as information on the structural layout of each engine. The engines and the related statistics were classified according to their structural layout and size. Size classification was based on the value of the compressor outlet air flow through the gas generator given by the parameters behind the compressor. Depending on the value of this criterion, the engines were divided into three groups: small-sized, medium-sized gas turbine engines, and large gas turbine engines. In terms of the structural layout, all engines were divided into three groups: turbofan engines without a mixing chamber, engines with a mixing chamber and afterburning turbofan engines. Statistical factors of the improved weight model were found for the respective groups of engines, considering their design and size. The coefficients of the developed model were determined by minimizing the standard deviations. Regression analysis was carried out to assess the quality of the developed model. The relative average error of approximation of the developed model was 8%, the correlation coefficient was 0,99, and the standard deviation was 10,2%. The model was found to be relevant and reliable according to Fisher's test. The obtained model can be used to assess the engine weight at the stage of conceptual design and for its optimization as part of an aircraft.

Evaluating R450A as a drop-in replacement for R134a in household heat pump tumble dryers

This paper presents the results of an experimental study evaluating R450A as a possible drop-in replacement for R134a in household heat pump tumble dryers. A heat pump installed in a tumble dryer was equipped with pressure and temperature sensors, and electrical power meters. First, the energy consumption according to the IEC 61121 standard was evaluated using R134a. Then the refrigerant was replaced with R450A and a new optimal charge was determined. The tumble dryer performance was then evaluated again and compared with the previous results. It was found that R450A is a suitable drop-in replacement for R134a in heat pump tumble dryers. The total energy consumption of the tumble dryer decreased by 3.7% and several other benefits such as a better utilized evaporator, and a lower refrigerant temperature at the compressor outlet were observed. Additionally, the refrigerant charge CO2 equivalent was reduced by more than 50%. However, the duration of the drying cycle increased by 4.2%, due to a slightly lower condensing temperature in the heat pump.

Analysis of Timewise Compressor Fouling Phenomenon on a Multistage Test Compressor: Performance Losses and Particle Adhesion1

Abstract The analysis of the performance losses of a multistage compressor concerning the air contaminant is not widespread in literature and, the mutual interactions of particle materials, air humidity, and compressor load are not well studied. The airborne micrometric particles that enter the compressor can deposit on the internal surfaces, causing the loss of performance of the machine. In this paper, several experimental tests have been carried out on a multistage compressor unit. A detailed analysis has been carried out considering soil and soot ingestion, as well as the air relative humidity (RH) (ranging from 50% RH to 80% RH) and compressor rotating velocity. Several combinations of particle diameter, material, and operating conditions have been considered. The amount of contaminant at the compressor outlet has been measured and the capture efficiency of the whole machine has been determined. Over the exposure time, the capture efficiency ranges from 0.2 to 0.6 according to the powder type and compressor inlet conditions. The capability of the compressor to collect particles changes over time as a function of the condition, even if several tested cases appear characterized by an almost constant capture efficiency trend. In addition, the performance degradation has been monitored over time and, with the reference of the particle concentration, the present experimental campaign covers about 500 operating hours of an actual installation. After a detailed evaluation of experimental uncertainty, the performance losses due to particle contamination have been assessed. The losses in the compressor performance have been estimated by means of the pressure ratio of the axial stages. The maximum degradation has been estimated equal to 0.53%/h for the compressor pressure ratio. Soot particles appear stickier, especially in the presence of higher humidity and represent the most detrimental operating conditions for the compressor unit.

Dynamics and control of a turbocharged solid oxide fuel cell system

• A cold bypass valve control can comply with the fuel cell system constraints. • Four controllers were tested on the system during load variation scenarios. • The cascade controllers with feed-forward approaches are the most promising. • A proportional-integrative cannot control the system properly for quick transients. The purpose of this paper regards the design and testing of control systems for a 30-kW turbocharged solid oxide fuel cell system fuelled with biogas. The adoption of a turbocharger, instead of a micro gas turbine, for the fuel cell stack pressurisation, is an innovative solution that is expected to decrease the capital cost of such systems and to facilitate their penetration into the energy market. However, not being connected to an electric generator, the turbocharger rotational speed, and thus the air mass flow, cannot be directly controlled as in microturbines. The control of turbocharged solid oxide fuel cell systems is a novel topic, characterised by many technical challenges that have not been addressed before. To regulate the stack temperature, a cold bypass valve is included, connecting the compressor outlet to the turbine inlet. A dynamic model of this system was developed in Matlab-Simulink® to analyse the response of the turbocharged solid oxide fuel cell system to a cold bypass valve opening step change. System information obtained from this analysis was used to design and tune four controllers: a conventional proportional integral controller and three different cascade controllers. The controller performance was evaluated under two different scenarios, considering quite aggressive power ramps. The best results were obtained with a cascade controller, where the feedback loop was complemented by a feed-forward contribution based on power demand. This analysis demonstrated that such a control system effectively tracks the fuel cell maximum temperature target, complying with all the system operative constraints.

Dynamic Model of a Transcritical CO2 Heat Pump for Residential Water Heating

This paper presents a distributed mathematical model for a carbon dioxide direct expansion solar-assisted heat pump used to heat bath water. The main components are a gas cooler, a needle valve, an evaporator/collector, and a compressor. To develop the heat exchange models, mass, energy, and momentum balances were used. The model was validated for transient as well as steady state conditions using experimental data. A reasonably good agreement was observed between the predicted temperatures and experimental data. The simulations showed that the time step required to demonstrate the behavior of the heat pump in the transient regime is greater than the time step required for the steady state. The results obtained with the mathematical model revealed that a reduction in the water mass flow rate results in an increase in the water outlet temperature. In addition, when the carbon dioxide mass flow rate is reduced, the compressor inlet and outlet temperatures increase as well as the water outlet temperature.

Effect of system response on partial surge initiated instability in a transonic axial flow compressor

Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region. Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system, which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge. For further verification, a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study. In the first case, an additional test point is set on the wall of the plenum to detect the system response. Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions, the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated. In the second case, a screen is mounted at the compressor outlet to prevent positive feedback from the plenum. The experimental results demonstrate that in the absence of system feedback, it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge. In addition, three flow phenomena in the second case are discussed, including the occurrence of the single pulse, the unstable process during the stall evolution and the switch of instability inception.

Performance analysis and transient simulation of a vapor compression cooling system integrated with phase change material as thermal energy storage for electric peak load shaving

A vapor-compression cooling system utilizing PCM is studied whereby the electricity consumption peak load is shifted. More specifically, the dynamic performance of the cooling system with and without PCM is evaluated and is presented with details on the hottest day of the year in Tehran, Iran. The proposed system uses the cooling energy to freeze or “discharge” the PCM during nighttime when the cooling load is minimally needed and uses the stored cooling energy during the peak load hours by melting or “charging” the PCM. This leads to better performance during the peak load hours when higher cooling loads are required. Oleic acid was chosen as PCM. The simulation was performed in EES software. The system performance was investigated by evaluating several parameters such as coefficient of performance, compressor power consumption, accessible cooling load, melting fraction of PCM, evaporator outlet temperature, compressor outlet temperature, and saturation temperature of the condenser. The effect of different volumes of PCM and different daily temperatures was also investigated. Finally, the economic analysis was performed for different conditions. The results showed that PCM increases the accessible cooling load and decreases the electricity consumption during the peak load hours. For the PCM volume of 154 L, the daily accessible cooling energy, daily energy consumption, and electricity peak load have a 2.9%, 0.9%, and 47% reduction on the hottest day of the year, respectively. Increasing the PCM volume leads to a lower PCM melting fraction but a higher melting time during the peak load hours. For an increase from 38 L to 309 L in PCM volume, the melting time increases by 35%. Also, the daily accessible cooling load and the energy consumption decrease by 6.9% and 4.5%, respectively which leads to a 2.7% reduction in the COP. However, for the same change in the PCM volume, peak shaving increases from 12.7% to 68.7%. The economic analysis showed that depending on the electricity consumption price, the integration of PCM storage can be hugely profitable in terms of economic parameters as it can lead to peak shavings of up to 69%.

Experimental research into the methods for controlling the thermal-mechanical characteristics of pulsating gas flows in the intake system of a turbocharged engine model

It is a relevant objective in thermal physics and piston engine construction to develop technical solutions for controlling the gas dynamics and heat exchange of gas flows in the intake system of turbocharged engines in order to improve performance. The article presents other authors’ data on the improvement of processes in the gas exchange systems of piston engines. It also provides a description of experimental set-ups, instruments, measurement tools and research methods for establishing the thermal-mechanical characteristics of pulsating flows in the intake system of a turbocharged engine. The instantaneous values of the gas flow rate and the local heat transfer coefficient were determined using the measured results by applying a constant temperature hot-wire anemometer (H-WA). The article describes technical solutions for influencing the gas dynamics and heat exchange of gas flows by stabilising and turbulising the flow. The regularities of changes in the instantaneous values of the flow velocity, pressure and the local heat transfer coefficient in time for a pulsating gas flow with different intake system configurations are obtained. It is shown that the installation of a levelling grid in the compressor outlet channel leads to the stabilisation of the flow and the suppression of heat transfer in the engine intake system by an average of 15% compared to the base system. It was found that the presence of a channel with grooves in the intake system leads to flow turbulisation and the intensification of heat transfer in the intake system by an average of 25%.

Https://www.scipedia.com/public/Pan_et_al_2021a

The aviation industry found that a number of engine power-loss events were related to the ice crystal icing, and the research on ice crystal icing had gradually attracted the attention of scholars. In this work, the compressor and ice crystals ingested are regarded as study objects, and the trajectories of particles are calculated based on the Lagrangian approach. Moreover, the two-way coupling method is applied to solve the heat and mass transfer process between ice crystals and the flow field. The variation of particle diameter and temperature under different MVD (Medium Volume Diameter), RH (Relative Humidity) and TWC (Total Water Contents), and the variation of temperature, velocity and pressure of internal flow field are also studied. The result indicates that the MVD, RH and TWC play an important role in the ice crystals motion. Moreover, the temperature and velocity of internal flow field are also greatly affected by the three parameters while the pressure is little affected. In addition, without considering the ice crystal icing, the ice crystals ingested by the compressor would reduce the total temperature at the outlet of compressor, and improve the isentropic efficiency and mass flow rate.

Optimization of Cyclic Adsorption Processes and Gas Mixture Separation Plants

The analysis of the cyclic adsorption process and the installation of separation of gas mixtures by the method of pressure swing adsorption as an object of optimization have been carried out. The study found operating (control) variables (the duration of the adsorption stage, the pressure at the compressor outlet, the coefficient of reverse flow for the regeneration of the adsorbent, the program of changes in the opening time of the inlet and outlet valves of the installation); undefined parameters (composition, temperature and pressure of the initial gas-air mixture); output variables of the installation (concentration of oxygen, nitrogen in the product gas flow, the productivity of the installation, the degree of extraction and reduced costs for the production of oxygen with a given purity of 40 - 90 and higher vol.%). A one-stage problem of optimization of the regimes of a stationary periodic process of adsorption separation of atmospheric air and oxygen concentration was formulated and solved by the method of short-cycle adsorption under conditions of partial uncertainty of the initial information in the presence of restrictions on the purity of the product gas, the productivity of the installation and the rate of gas flow in the “frontal layer” of the adsorbent. An iterative algorithm for its solution is proposed.

Surge Fault Detection of Aeroengines Based on Fusion Neural Network

Aeroengine surge fault is one of the main causes of flight accidents. When a surge occurs, it is hard to detect it in time and take anti-surge measures correctly. Recently, people have been applying detection methods based on mathematical models and expert knowledge. Due to difficult modeling and limited failure-mode coverage of these methods, early surge detection cannot be achieved. To address these problems, firstly, this paper introduced the data of six main sensors related to the aeroengine surge fault, such as, total pressure at compressor (high pressure rotor) outlet (Pt3), high pressure compressor rotor speed (N2), power level angle (PLA), etc. Secondly, aiming at preprocessing of data sets, this paper proposed a data standardization preprocessing algorithm based on batch sliding window (DSPABSW) to build a training set, validation set and test set. Thirdly, aeroengine surge fault detection fusion neural network (ASFDFNN) was provided and optimized to improve the detection accuracy of aeroengine surge faults. Finally, the experimental results showed that the model achieved 95.7%, 93.6% and 94.7% in precision rate, recall rate and F1_Score respectively and consequently it can detect the aeroengine surge fault 260 ms in advance.

Determination of Fuel Gas Flow Rate in Gas Pumping Unit With Gas Turbine Drive and Centrifugal Supercharger

An algorithm for calculating the flow rate of fuel natural gas in a gas pumping unit (GPU) (GPU drive) and for several identical gas pumping units operating together in compressor shop or compressor station. The flow calculation model takes into account thermal characteristics, operating modes and limitations of GPU parameters. Main task when determining consumption fuel gas is the calculation of the capacity of compressor shops and GPU. Power calculation takes into account compression ratio and flow rate of gas pumped by compressors. After calculation of GPA working capacity GPA drives efficiency factor is determined and fuel gas flow rate in GPU (GPU drive) is calculated. Exact values and limitations of thermal parameters (allowable pressures, temperatures, pumped gas flow rates, efficiency factors of compressors and drives). At the same time, the parameters of the GPU will depend on its operating mode of the GAP. The algorithm takes into account four limitations of GPU parameters: minimum flow rate of pumped gas in GPU compressor, minimum drive power of the GPU compressor, maximum gas temperature at the outlet of the GPA compressor, maximum gas compression ratio in the compressor. Without taking into account these restrictions, the calculation of fuel gas may be incorrect, since the impossible operation mode of the GPU will be taken into account. Developed algorithm takes into account all necessary characteristics and limitations of GPU parameters, simulates real robot modes of existing and designed GPU.

Performance assessment of a two-stage CO2 small scale MT refrigerator

F-GAS regulation has introduced important limitations in the use of refrigerants in the small size commercial refrigeration sector, with a maximum GWP=150 since 2022, forbidding the use of R404A. Among alternatives, there are propane, low-GWP HFC/HFO mixtures or pure HFOs: each of them can be considered as an option depending on the refrigerant charge limit for the application or by the total cost accepted by customer. In case of remotely connected units with potential refrigerant leakages, such as condensing units, the use of CO2 is considered as an option, due to the its safety indexes (no toxic and no flammable) which enables the use of larger amount of refrigerant. Being the CO2 refrigerant cycle trans-critical in warm climates, it may have low COPs and not fulfil the limits imposed by Ecodesign rules. In this paper, a condensing unit working with R744 is experimentally tested to assess the performance according to EN13215:2016. To limit high temperature at the compressor outlet, a two-stage system working with an inverter-driven hermetic rolling piston compressor is considered with intercooler and flash gas removal at intermediate pressure. It has been verified that seasonal energy performance ratio (SEPR) can be over the threshold value of 2.3 applied since 2018.

Situation awareness and security risk mitigation for integrated energy systems with the inclusion of power‐to‐gas model

Power-to-gas (P2G) and gas-fired generation units (GFGUs) enable the bidirectional energy flow of integrated energy systems (IESs). The static security of IES should be analysed considering the interdependence between energy systems. In this study, the static security of IES is analysed, and a novel static security control strategy to improve the security of IES after N−1 contingency is proposed considering P2G. First, electricity–gas IES model is presented, and the multi-energy flow of IES is solved by the Newton–Raphson method. Then, N − 1 static security analysis is carried out for the electricity system and natural gas system. Based on the obtained Jacobian matrix during the energy flow calculation process after N − 1 contingency, variable sensitivity matrixes of voltage, gas pressure, branch power flow and pipeline flow to control variables are derived. Furthermore, a static security control strategy for IES based on the sensitivity matrices is developed to regulate operation statuses of P2G and GFGU and compressor outlet pressure to mitigate the violation of security constraints. The performance of the proposed analysis method and control strategy is evaluated by IES 4-12 and IES 118-48 test systems. The results demonstrate that the proposed control strategy can mitigate security risks of IES after N − 1 contingencies.

Techno-economic and environmental performance assessment of a MSW to energy plant for Indian urban sectors

Energy, exergy, environmental and economic (4-E) performance analyses along with an optimization study of a MSW fired combined cycle plant, conceived for an Indian city is reported here. The proposed plant consists of a MSW fired topping indirect-heated air turbine (AT) block and a bottoming reheat-steam turbine (ST) block. MSW generated from the city, after segregation, is allowed to burn in a combustor-heat exchanger (CHR) combined unit to transfer heat to the cycle in indirect manner. It is observed from the study that (in base case scenario), for a compressor outlet pressure (r) of 4 bar, air turbine inlet temperature (ATIT) of 1000 °C, and hot end temperature difference (HETD) of 100 °C for the heat exchanger (HX) of the CHR unit; overall electrical efficiency of the plant is about 44%. It is also observed that at base case, the plant delivers a net electrical output of about 2777 kWe. Exergy analysis at the base case revels that, maximum exergy destruction occurs at the CHR unit. The environmental analysis suggests a sustainability index (SI) of 1.62 and the net annual savings of about $ 78,303 in environmental damage cost, when compared to land-filling. Unit cost of electricity value is found to be about INR 8/kWh (0.1235$/kWh) at the base case. An optimization study is also attempted by considering varying plant design and operating parameters to find out the favourable performance of the plant in all aspects.

Development and comparison of control schemes for the off-design operation of a recompression supercritical CO2 cycle with an intercooled main compressor

Four control schemes with different main compressor outlet pressure control modes and/or parametric optimization options are developed for the off-design operation of a supercritical carbon dioxide cycle with an intercooled main compressor. The cycle performance under four control schemes is first evaluated under possible off-design conditions and then compared with two case studies on annual performance. The off-design results indicate that the parametric optimization can simplify the main compressor control during the off-design operation regarding the surge risk control. The results also indicate that parametric optimization under different pressure control mode results in significant differences regarding the cycle performance improvement. The parametric optimization under the variable pressure control mode leads to more noticeable cycle efficiency improvement (0.02%–23.1%) than under the fixed pressure mode (0.02%–16.7%), but also larger reductions in net output power and temperature differential compared to those with the latter scheme (8.4–47.7 MW and 6.1–26.1 °C). The hybrid scheme of these two modes is recommended to accommodate different operating scenarios. The optimum annual cycle efficiency with an efficiency improvement up to 11% is obtained with the parametric optimization under the variable pressure control mode at the design-point main compressor inlet temperature of 41 °C.

Thermodynamic analysis of an air conditioner using R22/HC blend with TiO2/Mineral oil nanolubricant to retrofit R22/POE oil

This research was performed experimentally and determined the first and second law performance (energetic and exergetic) of a split type air conditioner. A blend of R22 and R600a (80:20 by mass) was used as a refrigerant with TiO2/Mineral oil (MO) as a lubricant for a varied concentration of TiO2 (0.1–0.4%) as a drop-in replacement of R22/POE. The obtained data were analyzed to investigate the thermodynamic performance including compression work, compressor discharge temperature, cooling effect, coefficient of performance (COP), and exergy destroyed in the compressor, total exergy destruction, sustainability, and exergy efficiency. The analysis was based on temperature, pressure readings recorded from the appropriate gauge, and the physical and thermal properties of the refrigerants were extracted from REFRPROP 7.0 software. Experimental outcomes showed that both energetic and exergetic performance was improved for a blend with nanolubricants compared to R22. The compressor outlet temperature was found to be decreased by 15 ​°C for the blend with 0.4% TiO2/MO nanolubricant. Again, COP was improved by 10–19.5% for the various concentration of nanolubricant. The exergetic performance was also increased with the increase of concentration of nanolubricants and exergy destruction was reduced by 20.1–37.4% for the nanolubricant. It was found that exergy efficiency was also increased by 38–42.88% compared to R22. Also, exergy destruction and entropy generation were found to be maximum for the compressor compared to other components. Based on this experimental work, it can be concluded that nanolubricant and refrigerant blends worked safely without any modification in this system.

Rotor-Alone Tones in the Outflow Noise of a Centrifugal Compressor

Abstract This article investigates the generation of rotor-alone tones and their contribution to the outflow noise of a transonic centrifugal compressor stage with vaneless diffuser and volute by means of unsteady full-annulus computational fluid dynamics (CFD) simulations. The aerodynamic field and the generation and propagation of sound were simulated simultaneously using the unsteady Reynolds-averaged Navier–Stokes (URANS) approach of the solver trace and a numerical grid consisting of 170 M cells. To assess the accuracy of the predicted fluctuations, the investigation compares the simulated diffuser flow field to measured flow angles and pressure fluctuations obtained from experiments conducted on a large-scale test rig. The analysis explains the different sound generation mechanisms responsible for tonal components in the acoustic spectrum at the compressor outlet based on the Fourier decomposition of the pressure fluctuations in diffuser and volute. Furthermore, this article analyzes the modal structure of the simulated sound field at the volute outlet by means of a radial mode analysis and discusses the influence of changing operating conditions on the sound power emitted. The analyses reveal that supersonic flow phenomena occurring at choked operating conditions cause a significant increase in noise emissions. Furthermore, the investigation shows that the sound field at the volute outlet is dominated by few low-order modes, a fact that justifies the analysis using methods based on the compressed sensing in future experimental investigations.

Development of technology for repair of shaped elements of pipeline systems in hard-to-reach places

It is proposed that erosion or corrosion worn out bends of pipeline systems in hard-to-reach places be repaired by trenchless methods by pulling a sleeve or a flexible composite pipe with a piston. The possibility of implementing such an idea is confirmed by theoretical and experimental studies. Mathematical modeling of the process of pulling a sleeve by a piston by a pipeline that contains a defective tap is performed. Formulas are derived for determining all resistance forces acting on a mobile system, patterns of pressure changes at the compressor outlet during such work are determined. A technique has been developed for calculating the friction force between the sleeve and the inner wall of the pipeline at the outlet, due to the pressing of the sleeve through a change in the direction of pulling. The dependence of the required pressure for the piston to extend the sleeve only with a defective bend on the bend angle of the bend is determined. An experimental setup has been developed and built to study the dynamics of the sleeve pulling by a piston. As a result of the experimental tests, it was found that it is possible to extend the sleeve through a pipeline with a piston that contains bend. The resistance forces acting on the moving system, the patterns of pressure change at the beginning of the pipeline in time when the sleeve is pulled by the piston, are experimentally determined. The experimental results are compared with the results of theoretical calculations and the reliability of theoretically derived dependencies is confirmed. The technique and technology for repairing defective pipe bends in hard-to-reach places has been developed by pulling a sleeve or a flexible composite pipe with a piston. The piston moves under the pressure of the air supplied to the piston space by the compressor. A drum with a wound sleeve or flexible composite pipe is placed in a cylindrical sealed chamber. A special supporting device has been developed to place a flexible composite pipe wound into a bay in a cylindrical sealed chamber.

Modeling and Economic Analysis of MED-TVC Desalination with Allam Power Plant Cycle in Kish Island

In this paper, a system consisting of the Allam cycle and Multi-effect Distillation- thermal vapor compression) MED-TVC( desalination was proposed to reduce the amount of carbon dioxide in the atmosphere. It uses wasted energy for the simultaneous production of freshwater and power. Firstly, analysis of the Allam cycle delineated that the heat capacity suitable for the desalination cycle is estimated to be 100 MW, the amount of heat from the outlet of the compressor. The MED-TVC desalination system, one of the most suitable and the most economical desalination systems, is used to combine the Allam cycle and desalination in the Kish Island, located in the south of Iran. The results of this research indicate that the proposed cycle has a desirable economic performance, and the results of economic analysis using the net present value (NPV) method and internal rate of return (IROR) show the Payback period in this plan is 4.8 years.