Effects Of Wet Compression Research Articles

Theoretical and experimental study on effects of wet compression on centrifugal compressor performance

Through the internal cooling from evaporation of tiny water droplets during the compression process, wet compression can effectively augment the net power output of gas turbine under high ambient temperature condition. In this paper, effects of wet compression on compressor performance were theoretically and experimentally investigated on one of stages of a multistage centrifugal compressor and a new performance correction model for wet compression was proposed. This model is based on corrected similarity criterion and couples with equivalent gas properties of wet compression, droplet evaporation model and droplet dynamics loss. The results show that wet compression can increase pressure ratio and efficiency and reduce specific compression work at same pressure ratio. The effect enhances with the increase of water injection ratio and the decrease of droplet average diameter. The essence of influence on performance is the variation of equivalent isentropic exponent. For this stage, maximum pressure ratio and peak efficiency increase by 4.25% and 0.71% respectively with a water injection ratio of 2% and a droplet average diameter of 10 μm.

Numerical Investigation on the Effect of Dry and Wet Compression on a Linear Low Speed Compressor Cascade

Several techniques are implemented to reduce the temperature rise in multistage compressors, which leads to the noticeable improvement in specific power output of a gas turbine. The objective of the present investigation intends to understand the effect of incidence angles on the aerodynamic performance of the compressor cascade under wet compression. Using large eddy simulations (LES) the effects of wet compression on compressor flow separation and wake formation are investigated. Experimental investigation was performed to validate the numerical results. The study reveals notable flow modifications in the separated flow region under the influence of wet compression and the total loss coefficient reduces significantly at the downstream side of the compressor for positive incidence angles. On the other hand, for negative incidence angles the wet compression enhances the total pressure losses inside the blade passage. Also, in the present investigation, particular emphasis has been given to understand the water film formation at negative and positive incidence angles.

The Effect of Wet Compression on a Centrifugal Compressor for a Compressed Air Energy Storage System

There is an urgent demand to reduce compression power consumption in Compressed Air Energy Storage (CAES) systems. Wet compression has been widely used in gas turbines to reduce compressor power consumption and improve thermal efficiency, but this technology has not been applied yet in the CAES field. In this paper, a centrifugal compressor for CAES was numerically studied to investigate the effect of wet compression on compressor and droplet motion. The results showed that wet compression makes the performance curve shift to a high-pressure ratio/efficiency. Meanwhile, wet compression lowers the stall margin and narrows the stable operation range, and the effect is enhanced with the increase of water injection ratio or the decrease of average droplet diameter. Wet compression can effectively save compressor power consumption during energy storage, and at the designed pressure ratio, the power consumption can be reduced by 1.47% with a water injection ratio of 3% and an average droplet diameter of 5 μm. Influenced by the inertia and secondary flow, the droplets migrate to the impeller pressure and shroud side, thus causing brake loss by impacting on blades. The migration of droplets strengthens with the increase in the average droplet diameter and flow coefficient.

Thermo-fluid simulation of the gas turbine performance based on the first law of thermodynamics

The thermal efficiency of the gas turbine depends on the compression work which is in direct relationship with the working fluid temperature. Amongst various solutions presented to augment gas turbines and combined cycle power plants output, wet compression is known as the most cost-effective method. This paper provides a method of simulating wet compression, based on the first law of thermodynamics. Water droplet evaporation rate, compression work, and the concept of wet compression efficiency are described. Results of first law and second law analyses are compared, and the effect of wet compression on gas turbine performance is indicated. Moreover, the results of the wet compression procedure are compared with both the values obtained for the dry compression process and the results of wet compression analysis using the second law. Finally, it is seen that the first law analysis provides equally consistent results with the experimental data for the cases considered in the paper.

Optimization of wet compression effect on the performance of V94.2 gas turbine

Wet compression has been widely used in recent years for power augmentation and gas turbine efficiency improvement. In order to explore this issue, the paper first focuses on the effects of wet compression, an analytical method based on droplet evaporation. Matching compressor-turbine or typically matching component has been added to this model for the compatibility of mass flow, rotational speed and power. Since this essay advances the idea of optimization, one of the metaheuristic algorithms Cuckoo Search (CS) has been considered. Three variables including droplet diameter, amount of overspray and droplet size have been taken into account. The objective function is turbine output work where compressor will work out of surge and choke domain. The numerical results indicate degradation in compressor inlet air temperature and noticeable power increments.

The Effects of Wet Compression by the Electronic Expansion Valve Opening on the Performance of a Heat Pump System

In this study, by controlling the Electronic Expansion Valve opening, the influence of wet compression on a heat pump system was experimentally investigated in different heating conditions. The results demonstrate that the discharge temperature decreased and the mass flow rate increased, due to quality of the rising liquid droplets. It was also found that the heating capacity and power input of wet compression increased more than that of dry compression, with a superheat of 10 °C. The maximum COP (Coefficient of Performance) exists at a specific quality of ca. 0.94 to 0.90, as the power input in the region of wet compression is proportionally larger than the increase in the heating capacity, according to the decreasing quality. When the Entering Water Temperature of the Outdoor Heat Exchanger was 10 °C, 5 °C, and 0 °C, the COP increased by a maximum of ca. 12.4%, 10.6%, and 10.2%, respectively, in comparison to the superheat of 10 °C. In addition, the superheat at the discharge line is proposed as a proper controlling parameter to adjust the quality at the suction line, by varying the opening of the expansion valve during wet compression.

The Effect of Wet Compression on a Multistage Subsonic Compressor

In this paper, wet compression effect on an eight-stage axial subsonic compressor is simulated by steady numerical methods. Special attention is paid to the compressor design operating condition and rotating stall boundary to contrast and analyze the changes, such as the compressor performance and the flow-field characteristics under dry and wet conditions. The motions of water droplets are also simulated and analyzed. The results indicate that wet compression could weaken or eliminate the flow separation; improve the flow capacity, efficiency, and pressure ratio of this compressor; and make the compressor operating near the rotating stall boundary enter into the normal working condition.

Effects of Wet Compression on Performance of Regenerative Gas Turbine Cycle with Turbine Blade Cooling

When water is injected at an inlet of compressor, wet compression occurs due to evaporation of water droplets. In this work, the effects of wet compression on the performance of regenerative gas turbine cycle with turbine blade cooling are analytically investigated. For various pressure ratios and water injection ratios, the important system variables such as ratio of coolant flow for turbine blade cooling, fuel consumption, specific power and thermal efficiency are estimated. Parametric studies show that wet compression leads to significant enhancement in both specific power and thermal efficiency in gas turbine systems with turbine blade cooling.

The Effects of Wet Compression and Blade Tip Water Injection on the Stability of a Transonic Compressor Rotor

The rotor blade tip leakage flow and associated formation of the tip leakage vortex and interaction of the tip leakage vortex with the shockwave, particularly in the case of a transonic compressor rotor have significant impact on the compressor performance and its stability. Air injection upstream of the compressor rotor tip has been shown to improve compressor performance and enhance its stability. The air required for rotor blade tip injection is generally taken from the later stages of the compressor thus causing penalty on the gas turbine performance. In this study, effects of water injection at the rotor tip with and without the wet compression on the compressor performance and its stability have been examined. To achieve the stated objectives, the well tested transonic compressor rotor stage, NASA rotor stage 37, has been numerically simulated. The evaluation of results on various performance parameters, such as total pressure ratio, inlet flow capacity, and adiabatic efficiency combined with contours of total pressure losses, entropy, Mach number, and temperature including limiting streamlines, shows that the blade tip water injection could help in reducing low energy region downstream of the shockwave and strength of the tip leakage vortex with the compressor operating at its rotating stall boundary condition. The extent of reduction depends on the droplet size, injection flow rate, and its velocity. Furthermore, results show that combined case of the blade tip water injection and the wet compression could provide better stall margin enhancement than the blade tip water injection case.

Setup of an Experimental Facility for the Investigation of Wet Compression on a Multistage Compressor

At present, inlet fogging and wet compression are two of the most widely used approaches to enhance gas turbine performance, especially during hot seasons. However, potentially negative effects of these practices on long-term operational integrity of gas turbines should be evaluated carefully; in particular, wet compression may lead to the erosion of first compressor stages due to the impact of water droplets within the flow at compressor intake. This issue is still controversial in technical literature since only limited historical field operating data and information are available. Therefore, a test facility was specifically set up in the laboratories of the University of Ferrara, to evaluate the effects of wet compression on a small-size compressor. This paper presents the experimental facility developed for wet compression investigation and some preliminary results.

Wet compression performance of a transonic compressor rotor at its near stall point

In order to study the effects of wet compression on a transonic compressor, a full 3-D steady numerical simulation was carried out under varying conditions. Different injected water flow rates and droplet diameters were considered. The effect of wet compression on the shock, separated flow, pressure ratio, and efficiency was investigated. Additionally, the effect of wet compression on the tip clearance when the compressor runs in the near-stall and stall situations was emphasized. Analysis of the results shows that the range of stable operation is extended, and that the pressure ratio and inlet air flow rate are also increased at the near-stall point. In addition, it seems that there is an optimum size of the droplet diameter.

Understanding Effects of Wet Compression on Separated Flow Behavior in an Axial Compressor Stage Using CFD Analysis

The effects of wet compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry compression. Under different operating conditions and with wet compression, this study presents the changes in the extent of separated region on the flow channel surfaces, compression efficiency, pressure ratio and specific compression work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level.

Prediction of Evaporative Effects Within the Blading of an Industrial Axial Compressor

The results of a compressor flow-analysis code calibration study for estimating the effects of water evaporation within the blade rows of industrial axial compressors are presented. In this study, a mean-line code was chosen for the calibration tool due to its accepted use during preliminary design studies, at which time during the compressor design process one would logically consider power augmentation through wet compression. The calibrated code features a nonequilibrium thermodynamic single-droplet evaporation model augmented with an empirical splashing model, which, as input, uses measurements of droplet spectra data taken on water injection nozzles in an intake rig configured with realistic length scales. In addition, a wetted-airfoil-surface flow-angle deviation model is applied to predict changes in compressor stage characteristics, which, in turn, affect the inlet mass flow of the compressor. The test vehicle for calibration was a 50 Hz Alstom industrial gas turbine. Once calibrated, the code was successfully utilized to predict wet-compression effects for three additional like-family Alstom gas turbines operating at constant speed while under full load. The effects modeled by the code include bleed supply pressure suck-down and bleed temperature cool-down effects, as well as compressor inlet mass flow and power consumption effects.

Application of a Computational Code to Simulate Interstage Injection Effects on GE Frame 7EA Gas Turbine

This paper investigates effects of interstage water injection on the performance of a GE Frame 7EA gas turbine using aerothermodynamic modeling. To accomplish this objective, a computational code, written in FORTRAN 90 language and developed by DIEM University of Bologna, has been used. The calculation procedure considers effects of evaporation of injected water within the compressor including droplets dynamics, which are necessary in order to fully evaluate effects of wet compression on the gas turbine performance. The robustness of the computational code is demonstrated by evaluating stage-by-stage compressor performance and the overall gas turbine performance in the presence of inlet evaporative fogging, overspray fogging, and interstage water injection. The presented results show that water injection location influences compressor stage loading redistribution differently. The plausible explanations to the observed trends of various performance parameters are presented in this paper.

The wet compression technology for gas turbine power plants: Thermodynamic model

This paper examines from a thermodynamic point of view the effects of wet compression on gas turbine power plants, particularly analysing the influence of ambient conditions on the plant performance. The results of the mathematical model, implemented in “Matlab” software, have been compared with the simulation results presented in literature and in particular the values of the “evaporative rate”, proposed in Araimo et al. [L. Araimo, A. Torelli, Thermodynamic analysis of the wet compression process in heavy duty gas turbine compressors, in: Proceedings of the 59th ATI Annual Congress, Genova, 2004, pp. 1249–1263; L. Araimo, A. Torelli, Wet compression technology applied to heavy duty gas turbines – GT power augmentation and efficiency upgrade, in: Proceedings of the 59th ATI Annual Congress, Genova, 2004, pp. 1265–1277] by “Gas Turbines Department” of Ansaldo Energia S.p.A., have been taken into account to validate the model. The simulator permits to investigate the effects of the fogging and wet compression techniques and estimate the power and efficiency gain of heavy duty gas turbines operating in hot and arid conditions.