Compressor Mass Flow Research Articles

Speed controller design for turboshaft engine using a high-fidelity AeroThermal model

Abstract One of the main objectives of this research is to construct a high-fidelity aerothermal model for controlling the turboshaft engine power turbine rotational speed. Firstly, a high-fidelity aerothermal model of General Electric T700 is formed. The turboshaft engine aerothermal model is simulated and compared to engine design point data on MATLAB/Simulink environment. Thermodynamic equations and some algebraic equations are used. In predicting compressor mass flow rate, the adaptive neuro-fuzzy inference system method is preferred. A propeller model is also added to the turbo shaft engine aerothermal model and to keep the power turbine rotational speed at a constant value, a Proportional Integral Derivative controller is designed and applied. Open-loop and closed-loop simulations are conducted and successful outcomes are achieved. Results indicate that the differences between simulation and actual engine data are within acceptable limits. The suggested model can be readily updated and expanded to control additional parameters of the engine. PACS 2010 Classification: Control theory in mathematical physics, 02.30. Yy, Computer modeling and simulation, 07.05.Tp, 05.70.Ce Thermodynamic functions and equations of state.

High-fidelity model development of CO2 booster refrigeration systems in supermarkets using field measurements

Supermarket refrigeration systems adopting traditional refrigerants with high global warming potential (GWP) have impacts on global warming for indirect and direct greenhouse gases (GHG) emissions. CO2 is a popular low-GWP alternative. The transcritical operation of CO2 systems worsens their energy performance, but provides recoverable heat as a heat source to reduce gas consumption. To evaluate operation performance, data-driven models, trained by historical data, are weak in implementation with datasets outside the scope of training data; in contrast, theoretical models have better extrapolation ability to calculate all operation conditions of CO2 systems at supermarket. Existing theoretical modeling approaches often lack validation against the limited public-access data, which reduces model reliability for further applications, and adopt oversimplified inference methods for unmeasured variables, which increases the risks of breaking thermodynamic laws and lowering model accuracy. This study therefore develops a steady-state theoretical model for CO2 booster refrigeration systems validated against field measurements from three UK supermarkets. The available measurements are utilized to the best level to ensure model accuracy and physical interpretability. Proposed methods to infer missing variables in CO2 systems include condenser outlet temperature, evaporating temperature, compressor isentropic efficiency and compressor mass flow rate. Results show that proposed inference methods enhance the abilities of the proposed modelling approach to ensure data integrity, avoid breaking thermodynamic laws, and improve model accuracy by reflecting real-time actual values of unmeasured variables rather than rough assumptions. The proposed modeling approach provides satisfactory accuracy validated using high-resolution measurements across the whole year from three real supermarkets.

ANALYSIS OF SUITABLE METHODOLOGIES FOR COMPRESSOR MASS FLOW RATE CORRECTION TO OTHER SUPERHEAT LEVELS AND REFRIGERANTS

This paper investigates the impact of suction conditions and refrigerant on scroll compressor mass flow rate by using calorimeter tests from AHRI-11 and AHRI-21 reports, published by AHRI's Low-GWP Alternative Refrigerants Evaluation program. Two Copeland scroll compressors (20 and 51 cm3) have been analyzed including different suction conditions (SH = 11K, SH = 22K, Ti = 18ºC) and several refrigerants (R134a, R32, R410A, R404A, etc.). Previous studies have explored response surfaces for energy consumption and mass flow rate variables. This study aims to expand the analysis by identifying the optimal approach to extrapolate mass flow rate from specific suction conditions to others SH or suction temperature levels and refrigerants. The current compressor characterization standard relies on the 1981 Dabiri correlation to correct compressor mass flow rate with suction conditions. Thus, this study aims to assess the adequacy of this correction and explore alternative correction methods for improved results.

Predicting compressor mass flow rate using various machine learning approaches

Abstract A major focus of the present study is to construct high-fidelity models for predicting corrected mass flow rates based on the collected compressor map data. Both traditional machine learning research and modern deep learning techniques have been employed to obtain well-fitted regression models of compressor mass flow rate. As traditional machine learning methods, Multiple Linear Regression and Random Forest, are conducted on compressor maps for prediction of corrected mass flow rate. The time series-based deep learning models are able to capture the overall trend of a given input for specific map data. Therefore, a time series-based deep learning technique, namely Gated Recurrent Unit has been employed to improve regression results. Besides, the prediction capabilities of the models, results also show that the proposed models can be used for the development of dynamic aero-thermal mathematical models of gas turbine engines and mass flow rate models created for dynamic compressors in other disciplines.

A novel marine turbocharger compressor volume flow rate model based on stagnation enthalpy theory

The compressor volume flow rate model determines the mass flowing into the diesel engine in simulation. It is a key component model that affects the accuracy of the overall performance of the diesel engine. At present, there is a lack of an accurate and easy-to-use compressor volume flow rate model. To solve this, the stagnation enthalpy-based compressor volume flow rate model (SP model) is proposed. The SP model is compared with an improved version of the famous empirical JENSEN model, M-JENSEN (MJ), and physics-based KS model. The proposed SP model only requires the stagnation pressure to be determined. The empirical M-JENSEN model needs a compressor map to optimize its six parameters. The physics-based KS model requires specific work to be determined. The SP model needs the least measured data and is easy to be identified. Models’ accuracy comparison on ABB A270 shows that the proposed SP model can generate the compressor map with RMSE of about 1.1m3/s and mean relative error (MRE) of about 6.9%. The rated volume flow rate of ABB A270 is about 20m3/s. While the RMSE and MRE of MJ model are about 0.6m3/s and 3.1% respectively. And they are about 3.0m3/s and 17.4% for KS model. When the model’s accuracy is compared to MAN TCA88, SP model shows slightly better performance than its performance on ABB A270. The rated volume flow rate of MAN TCA88 is about 60m3/s. The values of RMSE of SP model, MJ model, and KS model are 3.2m3/s, 2.2m3/s, 10.3m3/s respectively. Their MREs are 6.73%, 4.45%, and 17.8% respectively. In terms of these results, it can be concluded that our proposed SP model needs the least data, easy to code, and has excellent performance. It is one of the best compressor mass flow rate models so far in real-time diesel simulation.

The accuracy of the mean value engine model affected little by the accuracy of compressor mass flow rate model for a marine diesel engine

The accuracy of the mean value engine model affected little by the accuracy of compressor mass flow rate model for a marine diesel engine

A numerical investigation of the effect of vaned diffuser water cooling on the internal flow field of a centrifugal compressor

Due to their high pressure rises, the gas temperature of high-speed centrifugal compressors can be very high to the detriment of compressor aerodynamic performance. A water-cooled vaned diffuser technique is proposed to alleviate this problem. Compressor housing integrated water-cooling passages are employed to introduce cooling water to the vanes through holes near the vane centre. The technique was applied to a 180 mm turbocharger compressor running at the tip speed of 452 m/s, and numerical studies with conjugate heat transfer and fluid-structure thermal interaction were carried out to find the effects of the cooling to compressor performance and the mechanical stress of diffuser vanes. The results show that compressor efficiency is improved by the cooling, and the improvement increases as compressor mass flow reduces. At modest pressure ratios around 3.3, the maximum improvement of 1.09 percentage points is achieved using 30°C inlet water temperature. The cooling is found to significantly reduce the air temperature near diffuser passage solid walls, thus lead to more uniform air temperatures at compressor exit. The reduction of 1.33°C and 2.21°C in the diffuser outlet temperature have been found at 1.68 kg/s air mass flow with 70°C and 30°C water inlet temperature respectively. Moreover, the thermal stress in diffuser vanes is shown to be lower with the cooling.

A novel R744 multi-temperature cycle for refrigerated transport applications with low-temperature ejector: Experimental ejector characterization and thermodynamic cycle assessment

A novel vapor-compression system concept employing carbon dioxide as the refrigerant is proposed to serve the needs of a typical medium-size refrigerated truck used for multi-temperature (MT and LT) goods delivery. The system design is based on the implementation of an ejector as the only component increasing the refrigerant pressure from the LT evaporation pressure to the MT evaporation pressure, thus providing cooling effect at two different temperature levels with only one stage of compression. The ejector was experimentally tested and its ability to effectively entrain mass flow rate from low pressure suction conditions (corresponding to a LT evaporation temperature of −25 °C) was assessed. Lower external ambient temperatures and consequent lower expansion energy available at the ejector motive nozzle leads to a reduction of the maximum achievable pressure lift. Moreover, a significant degradation of the ejector performance towards the highest pressure lifts is experienced. Based on the ejector experimental data, a numerical evaluation of the proposed cooling unit performance has been performed, highlighting that in design conditions (LT evaporation at −25 °C) the cooling unit provides a LT freezing power ranging between 1.1 kW and 2.3 kW and a corresponding minimum MT cooling power ranging between 5.1 kW and 3.8 kW, depending on the chosen ejector lift. The MT cooling power can be further increased by increasing the compressor mass flow rate. The system COP is maximized at the maximum available lift provided by the ejector.

Improving hydrogen refueling stations to achieve minimum refueling costs for small bus fleets

Fuel cell vehicles using green hydrogen as fuel can contribute to the mitigation of climate change. The increasing utilization of those vehicles creates the need for cost efficient hydrogen refueling stations. This study investigates how to build the most cost efficient refueling stations to fuel small fleet sizes of 2, 4, 8, 16 and 32 fuel cell busses. A detailed physical model of a hydrogen refueling station was built to determine the necessary hydrogen storage size as well as energy demand for compression and precooling of hydrogen. These results are used to determine the refueling costs for different station configurations that vary the number of storage banks, their volume and compressor capacity.It was found that increasing the number of storage banks will decrease the necessary total station storage volume as well as energy demand for compression and precooling. However, the benefit of adding storage banks decreases with each additional bank. Hence the cost for piping and instrumentation to add banks starts to outweigh the benefits when too many banks are used. Investigating the influence of the compressor mass flow found that when fueling fleets of 2 or 4 busses the lowest cost can be reached by using a compressor with the minimal mass flow necessary to refill all storage banks within 24 h. For fleets of 8, 16 and 32 busses, using the compressor with the maximum investigated mass flow of 54 kg/h leads to the lowest costs.

Characteristics of a Fluidic Oscillator with Low Frequency and Low Speed and Its Application to Stall Margin Improvement

Active flow control methods are commonly used in expanding the operating range of compressors. Indeed, unsteady active control methods are the main focus of researchers due to their effectiveness. For constructing an unsteady active control system, reliable actuators are significant. To compare with conventional actuators such as synthetic jet actuators and rotating valves, fluidic oscillators have structurally robust characteristics and can generate self-excited and self-sustained oscillating jets, which leads to its higher applicability in compressors under severe working conditions. Thus, to explore the feasibility of unsteady active control systems by the usage of fluidic oscillators, a low-frequency and low-speed oscillator is first designed and experimentally studied for improving the stability of a low-speed axial flow compressor. During the experiments, a special casing is designed to install 15 uniformly distributed oscillators in the tip region of compressor. Based on the unsteady micro injections of the rotor tip with rotor rotation frequency, the results indicate that the frequency/period of oscillators are flexible, in which the values are decoupled with the variation of inlet pressure. When the inlet-to-outlet pressure ratio of the oscillator is in the range of 1.1~2.0, the maximum velocity ranges from 30 m/s to 80 m/s. Moreover, the mass flow rate of the single oscillator only varies from 0.017‰ to 0.059‰ from the designed compressor mass flow rate. For the improvement of the compressor stall margin, the value is 3.45% when the total mass flow of oscillators is 0.08% of the designed compressor mass flow.

Performance Investigation of a Bladeless Air Compressor

Abstract This study aims to investigate the reversible operation of a bladeless air expander prototype operated reversibly in compressor mode to understand the performance by numerical method and compare its results experimentally. A bladeless machine can reverse its operation by simply inverting the rotational speed. However, expander and compressor performance may differ significantly since losses are exacerbated in the compressor mode. The prototype was previously tested as an expander (experimental highest isentropic efficiency of 36.5%). In this work, the reverse mode is discussed, when the prototype is actuated as a compressor, with and without diffuser at variable rotational speeds. In compressor mode, the fluid enters through the center axially, passes radially outwards through disk gaps, and exits throughout the diffuser. The momentum transfer and pressure gain are carried out by the shear force produced on the surface of the rotating disk. An experimental/theoretical analysis focused on the pressure ratio, mass flow, and efficiency of bladeless compressor is conducted. High losses (main leakage across the rotor) were noticed during the experiments, affecting the overall Tesla compressor performance. Numerical calculations are carried out to estimate leakage losses by comparison with experimental results. It is shown that the original expander design would require specific modifications to reduce end disk leakages, which are higher in compressor mode than in expansion mode, significantly affecting the elaborated net mass flow. Improved diffuser, scroll, disk end gaps, and sealing mechanisms are discussed in order to augment overall performance of the bladeless prototype in compressor mode.

Numerical study on the influence of mist-air mixtures on axial compressor performance

To study the influence of mist-air mixtures on the performance of an axial-flow compressor, based on the Euler-Lagrange multiphase flow model coupled with compressor aerodynamic calculation, droplet motion, and wall film model, we establish a numerical method for compressor multiphase flow, which is used to study the performance change law of a low-pressure axial compressor with mist-air injection. The results indicate that the compressor inlet fogging will produce a wall film on the blade surface and the casing wall, resulting in a decrease in the total pressure coefficient and mechanical efficiency of the compressor under full operating conditions, and this decrease is more significant with the increase of spray water-air ratio and spray particle size. With the change of compressor mass flow, the wall film on the blade surface presents the following migration law: the thickness of wall film on the pressure surface and on the suction surface decreases and increases respectively with the increase of mass flow, and the specific distribution law of wall film on the blade surface does not change obviously. Meanwhile, a compressor inlet fogging test is carried out in this study to verify the accuracy of the multiphase flow numerical method for compressor performance prediction. The experimental results show that the numerical method can effectively and quantitatively analyze the effect of mist-air mixture injection on compressor performance, and can be further improved by more detailed experimental research to achieve a more accurate numerical method for compressor multiphase flow.

Design of compressor impeller under high Reynolds number conditions

PurposeA parametric method for designing the hub, casing and blades of the miniature centrifugal compressor impeller was developed. The relationship model of the size, aerodynamic and performance parameters of the centrifugal impeller was established. Based on the selected design parameters, the miniature centrifugal-type impeller was designed, and the work efficiency was calculated.Design/methodology/approachIn this study, a micro-centrifugal compressor impeller with a diameter of less than 25 mm was designed. A parametric design method was developed, and the functional relationship between the geometric and gas fluidity parameters was established.FindingsThe results of this study showed that the performance parameters of the designed micro-centrifugal impeller satisfied the design requirements. The proposed method is useful as a reference for designing and analysing compressor impellers under high Reynolds number conditions.Originality/valueA parametric design method was developed, and the functional relationship between the geometric and gas fluidity parameters was established. Under the Reynolds number conditions, the flow characteristics of the gas in the compressor were analysed; the shear-stress transport turbulence equation was solved using the finite volume method. In addition, the effects of the Reynolds number on the velocity, pressure, mass flow and efficiency of the micro-scale centrifugal compressor were evaluated. The results showed that the performance parameters of the designed micro-centrifugal impeller satisfied the design requirements. The proposed method is useful as a reference for designing and analysing compressor impellers under high Reynolds number conditions.

Turn-Down Capability of Ansaldo Energia's GT26

Abstract The operational flexibility of heavy-duty gas turbines is of increasing importance in today's power generation market. Fast startup, fast loading, grid frequency support, fuel flexibility, and turn-down capability are only some of the keywords that describe the challenges for GT manufacturers. This paper reports Ansaldo Energia's activities to further reduce the minimum environmental load of the GT26. The difficulties related to operation at very low loads and the solutions that were developed are explained. Furthermore, the results of engine validation tests of the new extended low load operation and extended low part load operation concepts are presented. The enhancement of the operational flexibility of the GT26 is in the focus of Ansaldo's development activities since many years. Its sequential combustion system is a very good basis for flexible and emission compliant operation down to very low loads. Ansaldo Energia's low part load (LPL) and low load operation (LLO) concepts are standard products in the GT26 flexibility portfolio and established in the market for many years. LPL operation extends the standard operating range down to low loads by switching off individual burners in the second combustor (sequential environmental (burner) (SEV) combustor). The compressor mass flow can be varied between idle and base load levels. Low load operation is characterized by a combination of idle compressor mass flow and base load temperatures in the first combustor (environmental (burner) combustor). The SEV combustor is switched off. LLO is intended to be a “parking point,” where the plant can operate in combined cycle mode during times of low electricity demand. Ansaldo Energia has conducted a development project in the past two years to further reduce the minimum simple cycle and combined cycle loads. The extension of the LLO and LPL operating ranges and their combination into one single feature are the main targets of the project.

A METHOD TO DETERMINE THE MASS FLOW TO RECIPROCATING COMPRESSORS

To establish the mass flow to a reciprocating compressor there are several relationships used in the construction and analysis of these types of compressors. The use of relationships is based on the geometric elements of the compressor. It is also necessary to know the composition of the gas and the operating conditions with which: the adiabatic exponent, the volumetric efficiencies and the compressibility factor are determined. The paper aims to establish the compressor mass flow with the help of modern means. The modeling was done in the LMS Amesim program. We use elements from the library of program to create a virtual model of the compression system. A comparison is made with the results obtained by the classical methods. The results show that there are no big differences between the values of the mass flow obtained through the usual relations and those obtained based on the realized model, that includes the main elements necessary for a precise calculation. However, the proposed method opens a wider horizon of understanding of the compression system through direct correspondence with the real model and the graphical possibilities of displaying the time variation of the system characteristics.

Investigation of variable geometry orifice design for improving centrifugal compressor low-end performance and stable operating range

Active control of the inlet flow area in a centrifugal compressor is a method to improve compressor aerodynamic performance and stall margin. As a core part of the area control device, the variable geometry orifice is investigated and its two key design parameters are analyzed in detail, the setting angle of the orifice with respect to the shroud casing and the radial height of the orifice to the shroud casing from the orifice inner rim. This paper proposes a physics-based equation that describes the relationship of the two parameters with compressor mass flow rate and then validates the equation using numerical simulations. As far as the setting angle, the physics-based equation suggests not to be larger than 90°. The numerical results not only validate the physics-based equation but also show the most optimal angle of 78°. In terms of the orifice height, both the physics-based equation and the numerical simulations suggest an active height control of orifice in the compressor inlet duct.

Circumferential Variation of Noise at the Blade-Pass Frequency in a Turbocharger Compressor with Ported Shroud

<div class="section abstract"><div class="htmlview paragraph">The ported shroud casing treatment for turbocharger compressors offers a wider operating flow range, elevated boost pressures at low compressor mass flow rates, and reduced broadband whoosh noise in spark-ignition internal combustion engine applications. However, the casing treatment elevates tonal noise at the blade-pass frequency (BPF). Typical rotational speeds of compressors employed in practice push BPF noise to high frequencies, which then promote multi-dimensional acoustic wave propagation within the compressor ducting. As a result, in-duct acoustic measurements become sensitive to the angular location of pressure transducers on the duct wall. The present work utilizes a steady-flow turbocharger gas stand featuring a unique rotating compressor inlet duct to quantify the variation of noise measured around the duct at different angular positions. The acoustic pressure transducers installed on the rotating duct record time-resolved in-duct acoustic pressure at different azimuthal locations while the compressor is held at a steady operating point. Acoustic measurements are performed across the flow range of a ported shroud compressor at three different rotational speeds. A comparison of sound pressure levels measured at different azimuthal locations reveals the significant contribution of high-frequency BPF noise to the variation in the acoustic pressure around the duct.</div></div>

Study on heating performance of solar-assisted heat pump drying system under large temperature difference

In this study, a heat pump drying (HPD) system platform complemented by solar hot water was designed and established. The objective was to address the declines in the heating performance of air source HPD at high altitudes (more than 3000 m), cold conditions (annual average temperature at 5 °C), and with large temperature differences between day and night (more than 20 °C), i.e. under harsh conditions. A theoretical model was derived to determine the system parameters and to support the experimental analysis. Under no-load conditions, four cases with ambient temperature were tested and compared to explore the relationships between the system parameters and performance, as well as the effectiveness of the supplementary solar hot water. The heating performances under HPD and solar-assisted HPD (SHPD) modes were compared and analysed under load conditions (930 kg Mu Xiang). The results indicate that a decrease in the ambient temperature and increase in the temperature in the drying room causes attenuations of the compressor mass flow rate, evaporator cooling power, condenser heating power, and system coefficient of performance (COP). In addition, solar water heating can significantly improve the heating performance of the HPD system. Under no-load conditions, the average heating power of the HPD-mode system is 19.27 kW, and the average COP is 2.76. The average heating power of the SHPD mode system is 23.34 kW, and the average COP of the system reaches 3.24, an increase of 17.4%. Under load conditions, the average heating capacity power of the HPD mode is 9.64 kW; the COP is only 1.34, and fluctuates significantly with the decrease in ambient temperature. The average heating capacity power of the SHPD mode is 17.62 kW and the COP is 2.42, i.e. 1.8 times of that of the HPD mode. By raising the drying room temperature to the same set temperature, the SHPD mode time is shortened by 70%.

A Marine Turbocharger Retrofitting Platform

Abstract A turbocharger retrofitting platform utilizing one-dimensional (1D) models for calculating turbomachinery components map and a fully coupled process for integration with the turbomachinery components and the diesel engine, is presented. The platform has been developed with two modes of operation, allowing the retrofitting process to become fully automatic. In the first mode, available turbocomponents are examined, in order to select the one that best matches the entire engine system, aiming to retain or improve the diesel engine efficiency. In the second mode, an optimization procedure is employed, in order to redesign the compressor to match the entire system in an optimum way. Dimensionless parameters are used as optimization variables, for a given compressor mass flow and power. A retrofitting case study is presented, where three retrofitting options are analyzed (compressor retrofit, turbocharger retrofit, and compressor redesign). In the first and second option, turbocharger retrofitting is carried out, using available turbocomponents. It is shown that initial performance cannot be reconstituted using off-the-self-solutions. In the third option, compressor designing is performed, using the optimization mode, in order to provide an improved retrofitting solution, aiming to at least reconstituting the original diesel engine performance. Finally, a CFD analysis is carried out, in order to validate the compressor optimization tool capability to capture the performance trends, based on geometry variation.

Thermodynamic modeling and comparative analysis of a compressed air energy storage system boosted with thermoelectric unit

Current study represents the thermodynamic modeling and exergy analysis of a compressed air energy storage system boosted with thermoelectric generator (CAES/TEG). To evaluate the studied system, a comparative analysis between compressed air energy storage system (CAES) with CAES/TEG has been done. Exergy, a powerful tool for analyzing energy conversion systems, is employed to determine the exergy destruction rate and exergy efficiency of the system as well as different related components. The results of exergy analysis indicates that the wind turbine with 35.28 kW (44.81% of total exergy destruction rate) has the highest exergy destruction rate and after that in the second and third places are combustion chamber and cavern. Findings indicate that with adding thermoelectric modules to the CAES system, the output power of Rankine cycle and organic Rankine cycle increase about 1.16 kW and 0.959 kW in comparison with CAES system, which these changes lead to increasing the net output power of the system in CAES/TEG system from 33.59 kW to 35.71 kW compare with CAES. Moreover, the influences of main parameters such as compressor mass flow rate, compressor pressure ratio, and combustion chamber outlet temperature and wind speed on the CAES/TEG performance are investigated.