A new formulation for the non-equilibrium allowance in MSF processes

The paper presents a case study focusing on the assessment of the aerothermodynamic and rotordynamic performance to diagnose deposit accumulation on the internals of a centrifugal compressor. The case involves a four-stage gas lift centrifugal compressor powered by a 5.9 MW induction motor and utilizing a fluid coupling to regulate the compressor's rotational speed. The Huntington 4-point method was employed to evaluate the polytropic head and efficiency of the four compressor sections over a 20-month period, with pressure and temperature data sampled every 6 hours. The efficiency model was supported by the GERG-2008 equation of state, used to calculate the necessary thermodynamic properties at intermediate and endpoint states. The aerothermodynamic analysis identified a deterioration in polytropic efficiency in compressor section 3, accompanied by a pressure drop and an increase in discharge temperature. Simultaneously, the rotordynamic response was examined through various vibration plots. Although the increase in the vibration amplitudes was not significant, a notable phase shift was observed. This decline in polytropic efficiency and change in vibration patterns were attributed to severe fouling, which was confirmed during the overhaul of the HP compressor. Root cause investigations revealed the deposit as reactive, leading to the installation of an online washing system. Over a nine-month observation period post-maintenance, the compressor operation was stable with no degradation in its polytropic efficiency.

مهمترین هدف برنامه‌ریزی و مدیریت آبیاری افزایش بهره‌وری و راندمان مصرف آب و در عین حال دارا بودن یک سامانه پایدار تولید است. به منظور بررسی تاثیر انواع خاک‌پوش بر کارایی مصرف آب، شاخص‌های رشدو عملکرد ذرت، پژوهشی به صورت طرح بلوک‌های کامل تصادفی با 6 تیمار و 3 تکرار در سال زراعی 93-94 در مزرعه پژوهشی دانشگاه شهرکرد انجام شد. تیمارها شامل شاهد (بدون پوشش)، پوشش پلاستیک شفاف، پلاستیک سیاه، گونی نخی کناف، گونی سفید و آبی بود. در طول فصل کشت، رطوبت خاک تا عمق توسعه موثر ریشه اندازه‌گیری و آبیاری‌ها بر اساس کمبود رطوبت خاک با تأمین نیاز آبی کامل تعیین و اعمال گردید. در طول فصل رشد نمونه‌برداری برای تعیین میزان ماده خشک برگ، ساقه و میزان آماس نسبی برگ انجام گرفت و در پایان فصل رشد نیز میزان حجم آب مصرفی، میزان دانه تولیدی، اندازه‏گیری و ثبت گردید. نتایج نشان دادکه خاک-پوش‌ها در تمام مراحل اندازه‏گیری تأثیر افزاینده بر محتوای نسبی آب برگ داشته‌اند که این می‌تواند ناشی از تأثیر آن‌ها بر حفظ رطوبت خاک باشد. خاک‌پوش پلاستیک شفاف بیشترین تأثیر را بر شاخص برداشت با مقدار 97/53 درصد داشت که این مقدار متناظر افزایش 32 درصد نسبت به تیمار شاهد بود. بیشترین و کمترین میزان کارایی مصرف آب به ترتیب مربوط به تیمار گونی‌سفید و شاهد با مقادیر 7/2 و 4/1 کیلوگرم وزن خشک دانه بر مترمکعب بدست آمدکه این معادل افزایش 93 درصد میزان کارایی مصرف آب می‌باشد. بنابراین خاک‌پوش گونی‌های سفید وآبی بیشترین تأثیر را بر حفظ رطوبت خاک و عملکرد محصول دارا بودند.

In most compressors the flow is adiabatic, but in low-speed turbochargers, the compression process has both heat transfer and work input. This paper examines different compressor efficiency definitions for such diabatic flows. Fundamental flaws in the use of the isentropic efficiency for this purpose are identified, whereas the polytropic efficiency can be used with or without heat transfer without ambiguities. The advantage of the polytropic approach for a practical application is demonstrated by analyzing the heat transfer in a turbocharger compressor. A simple model of the heat transfer allows a correction for this effect on the polytropic efficiency at low-speed to be derived. Compressor characteristics that have been corrected for this surprisingly large effect maintain a much higher efficiency down to low-speeds.

In most compressors the flow is adiabatic, but in micro-compressors, and in turbochargers at low speeds, the compression process has both heat transfer and work input. The classical adiabatic efficiency definition found in most text books is then incorrect. This paper extends the text book definitions of compressor efficiency to diabatic flows. The paper explains different compressor efficiency definitions in a logical way and identifies fundamental flaws in the use of isentropic efficiency for a diabatic flow. It shows that the polytropic efficiency can be used with or without heat transfer without ambiguities. Other significant advantages of the polytropic efficiency are also summarized, as they are not fully covered in any turbomachinery text books. The advantages of the polytropic approach for a practical application are demonstrated by analyzing the heat transfer in a turbocharger compressor. A simple model of the heat transfer allows a correction for this effect on the polytropic efficiency at low speed to be derived. Compressor characteristics that have been corrected for this surprisingly large effect maintain a much higher efficiency down to low speeds.

A method for modelling compressor bleed in gas turbine analysis software

The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a backward curved impeller of 500 mm tip diameter and 24.5 mm width and its design flow coefficient is ϕd=0.0535. Three different low solidity diffuser vane shapes namely uncambered aerofoil, constant thickness flat plate and circular arc cambered constant thickness plate were chosen as the variants for diffuser vane shape and all the three shapes have the same thickness to chord ratio (t/c=0.1). Flow coefficient, polytropic efficiency, total head coefficient, power coefficient and static pressure recovery coefficient were chosen as the parameters for evaluating the effect of diffuser vane shape on the stage performance. The results show that there is reasonable improvement in stage efficiency and total head coefficient with the use of the chosen diffuser vane shapes as compared to conventional vaneless diffuser. It is also noticed that the aero foil shaped LSD has shown better performance when compared to flat plate and circular arc profiles. The aerofoil vane shape of the diffuser blade is seen to be tolerant over a considerable range of incidence.

Hydrocarbon based energy sources such as coal, oil and natural gas have been diminishing in an increasing speed. Instead of finding alternative energy sources, we have to use the available sources more effectively. By means of the irreversibility analysis, we can determine the factors or conditions that cause the inefficiencies in any energy system. In this study, irreversibility analysis of a compression cascade refrigeration cycle that consists of a high and low temperature cycles is presented. In the high temperature cycle, the refrigerants from different classes, namely R12 (CFC), R22 (HCFC), R134a (HFC) and R404a (Azeotropic) are selected as working fluids. In the low temperature cycle, R13 is only used as a working fluid. Irreversibility analysis of refrigerant pairs, namely R12-R13, R22-R13, R134a-R13, and R404a-R13 are carried out in a compression cascade refrigeration cycle by a computer code developed. The effects of evaporator temperature, condenser temperature, and the temperature difference between the saturation temperatures of the lower and higher temperature cycles in the heat exchanger (ΔT) and the polytropic efficiency on irreversibility of the system are investigated. The irreversibility of the cascade refrigeration cycle decreases as the evaporator temperature and polytropic efficiency increase for all of the refrigerant couples considered while the irreversibility increases with the increasing values of the condenser temperature and ΔT. In the whole ranges of evaporator temperature (−65°C / −45°C), condenser temperature (30–50°C), ΔT (2–16K) and polytropic efficiency (%50/%100), the refrigerant pair R12-R13 has the lowest values of irreversibilities while the pair R404a-R13 has the highest ones. At the lower condenser temperature (<30°C) and higher polytropic efficiencies (85%–95%), the refrigerant couples except for R404a-R13 have approximately the same values of irreversibility.

ABSTRACTThis paper is a numerical simulation that was made in the three-dimensional flow, carried out in a modified centrifugal compressor, having vaned diffuser stage, used as an auto-motive turbo charger. Moreover, the performance of the centrifugal compressor was dependent on the proper matching between compressor impeller and vaned diffuser, influencing significantly surge and the efficiency of centrifugal compressor stages. In addition, a modified compressor impeller, coupled with vane and vaneless diffuser, has been found to have similar internal flow patterns for both the vaneless and vaned diffuser design. The vaned diffuser effect has been paid particular attention in terms of better analysis where the diffuser was designed for high sub-sonic inlet conditions. Another aim of this research was to study and simulate the effect of vaned diffuser on the performance of a centrifugal compressor. The simulation was undertaken by using a commercial software, the so-called ANSYS CFX, to predict numerically the performance in terms of pressure ratio, poly tropic efficiency and mass flow rate for the centrifugal compressor stage. The results were generated from CFD and were analyzed for better understanding of the fluid flow through centrifugal compressor stage. Conclusively, it was observed that the effect of the vaned diffuser is to convert the kinetic energy into a high static pressure after analyzing the results of the simulation.

The work is devoted to the development of an integrated approach to the aerodynamic improvement of the blade vanes of multistage axial compressors of gas turbine engines. One of the features of the studies carried out to optimize the blade vanes was to take into account the mixing effects by various sources of losses. Thus, minimization of losses sources in compressor blade vanes during their profiling is achieved due to the account of the complex three-dimensional vortex nature of the flow and the use of modern software systems for solving the Navier-Stokes equations. Calculations of the three-dimensional viscous flow in the work are performed with ANSYS software. The profiling of the multi-stage compressor blades is carried out with “Kompress 2.0” software package, the feature of which is the use of parametric models of rotor and stator blade vanes, adapted for their aerodynamic optimization, as well as taking into account the radial unevenness of the incident flow when selecting the tangential blades shape of the stator vanes. As a result, a complex methodology for the optimal design of the blades of a multi-stage compressor with the use of "controlled" diffusivity, S-shaped profiles, lean, and chord variation is developed, with simultaneous variation of geometric parameters according to special plans and the use of the compressor efficiency as an integral efficiency criterion, “Kompress 2.0” for the blades profiling, ANSYS for the calculation of threedimensional viscous flow. Multi-stage axial compressors have been designed, numerically and experimentally investigated. Based on the results of experimental studies of multistage axial compressors, new generalizing relationships are established, that establish a relationship between the geometric parameters of the profiles and their gas dynamic characteristics to take into account the features of the spatial shape of the flow at the stage when solving the inverse design problem. The results of the research were used in the design and improvement of the elements of the flow paths of the ZM multistage compressors. Test aerodynamic optimization of the blade systems of experimentally studied multistage compressors with the use of the proposed approaches made it possible to obtain the efficiency of high-pressure compressor stages at the level of 0.92 ... 0.93 and to increase the efficiency of multistage axial compressors by 1.0-2.4%. The efficiency of the 10-stage compressor is 0.8% (to the level of 0.853), the efficiency of the 6-stage compressor is 1.1% (to the level of 0.825), the efficiency of the 3-stage compressor is 2.4% (to the level of 0.885), and the efficiency of an 8-stage axial compressor is 1.6% (to the level of 0.879).

The present investigation is undertaken to study the performance of an existing stage of an industrial centrifugal compressor with a vaneless diffuser and is aimed at improving the efficiency of the compressor stage through the use of a low-solidity (LSD) vaned diffuser. The experiments were conducted at a tip Mach number of 0.35. The LSD vane is formed from a standard aerofoil profile with marginal modification in the trailing edge region. The study was conducted at a solidity ratio of 0.81, which is considered as the optimum for the chosen stage. The overall stage performance for different diffuser vane setting angles was evaluated in terms of flow coefficient, head coefficient, polytropic efficiency and static pressure recovery coefficient. The performance parameters are normalized with respect to those of the vaneless diffuser at design flow. Improvement in performance as well as static pressure recovery was observed with LSD vanes as compared with a vaneless diffuser configuration. Variation in blade loading was studied from measurements of static pressure on the pressure and suction surfaces of LSD vanes at different vane setting angles. It was observed that the vane setting angle has a significant effect on stage performance and also on the blade loading.

Polytropic change of state calculations are used within many thermodynamic cycle analysis tasks for turbomachinery like gas turbines or compressors. The typical approach is using formulas, which are theoretically valid for ideal gas conditions only. But often gases are used, which do certainly not behave like ideal gases. This is motivation to check how and which polytropic change of state algorithms can be used for real gases or corresponding mixtures. There is a vast experience on polytropic efficiencies achievable with existing turbomachinery. Manufacturers calibrate their performance analysis with real test results for compensating potential deviations from their analysis approach. But they normally do not disclose their approaches for the thermodynamic calculation and the corrections made based on their test results. But for investigations of new thermodynamic cycles before the stage of development with an available demonstrator a best possible prediction of the performance is desired. In this paper the assumptions and formulas for calculating polytropic changes of state and polytropic efficiencies are gathered from literature. The most fundamental assumption is based on a constant dissipation rate during the polytropic change of state. It could be tracked back to Zeuner, Stodola and Dzung. A numerically convenient approximation is the “polytropic exponent approach”. It fulfills the first assumption for an ideal gas but it is only an approximation for real gases. The temperature after a polytropic change of state is defined by its initial condition, the pressure ratio and the polytropic efficiency. Three different calculation algorithms are compared here: The recursive “constant dissipation rate algorithm” suggested by the author, the most used “ideal gas formula” and the “polytropic exponent formula” as the most used approximation for real gases. Numeric results for compression from 1bar to up to 100bar are shown for dry air, Argon, Neon, Nitrogen, Oxygen and CO2. The deviations of the different calculation approaches are considerable.

This research was conducted in Toroq Experimental field station, Mashhad, Iran, for two successive cropping seasons (2000-2002), using split plot experimental design based on complete randomized blocks with three replications. Moisture stress treatments (at seven levels) were assigned to main plots, including: D1 ( full irrigation), D2 (no irrigation from one-leaf to double ridge) stage, and in other treatments, no irrigation and preventing rainfall as: D3 (from one-leaf to floral initiation stage), D4 (from floral initiation to the commencement of stem elongation or Terminal spikelet), D5 ( from commencement of stem elongation to flag leaf emergence), D6 (from flag leaf emergence to anthesis) and D7 (from anthesis to the soft dough), and four wheat cultivars, namely: Roshan, Qods, Marvdasht and Chamran, were sown in sub plots. The results of combined analysis of variance showed that the effect of moisture stress was significant. Applying D5, D6 and D7 treatments reduced the grain yield in comparison with control (D1) by 36.7, 22.8 and 45.6, respectively. Severe moisture stress treatments (D5 and D7) caused a reduction in water use efficiency (WUE) and radiation use efficiency (RUE), due mainly to reduction of dry matter. Based on these results, grain filling (D7) and fast growing (D5) stages of wheat were more sensitive to moisture stress. Genotypic differences were also observed with respect to concerned characteristics. Chamran had a higher moisture tolerance, therefore, greater grain yield as compared with the other cultivars. Keywords: Moisture stress; Developmental Stages; Water Use Efficiency; Radiation Use Efficiency; Grain yield

The objective of the present study was to determine the importance of the pre-flowering growth stage for common bean yield. In two assays, the common bean BRS-Pérola, BRS-Valente and Jalo Precoce cultivars were sown at five different dates, from April to August, in 2001 and 2002, at Embrapa Arroz e Feijão, in Santo Antônio de Goiás, Goiás State, Brazil. The experiments were carried out under conventional tillage, in a randomized split-plot block design, with four repetitions. Physiological parameters related to common bean plant growth, development and yield were correlated with temperatures and solar radiation incidence, during the pre-flowering plant growth period. Increases of minimum temperature, solar radiation, and N absorption rate, and decrease in N efficiency use, up to the third trifoliolate leaf stage, were correlated with yield reduction. The phenological period between emergence and third trifoliolate leaf is the most important one for common bean yield determination, when compared with the total pre-flowering period. KEY-WORDS: Phaseolus vulgaris; common bean development; temperature; solar radiation.

Objetivou-se verificar a importância do período da emergência à pré-floração, na produtividade do feijoeiro. Em dois ensaios, as cultivares BRS-Pérola, BRS-Valente e Jalo Precoce foram semeadas em cinco épocas, entre abril e agosto de 2001 e 2002, em área experimental da Embrapa Arroz e Feijão, em Santo Antônio de Goiás, GO, próxima a uma estação meteorológica. Os ensaios foram instalados em sistema convencional de preparo de solo, em delineamento experimental de blocos ao acaso, com parcelas subdivididas e quatro repetições. Características fisiológicas relacionadas a crescimento, desenvolvimento e produtividade foram correlacionadas com temperaturas e radiação solar incidentes no período. Aumentos na temperatura mínima, radiação solar e na taxa de absorção de N e diminuição na eficiência do uso de N, até o terceiro trifólio, foram correlacionados com redução na produtividade. Na fase de pré-floração, o subperíodo entre a emergência e o terceiro trifólio é o mais importante para a determinação do rendimento de grãos do feijoeiro.

The only additional material here over that in chapter 4 is that it is convenient in the velocity diagrams to specify angles δ and γ for trigonometric purposes and polytropic stage efficiency is of importance since axial compressors, which are usually multistage machines are mostly designed on the basis of one stage with an assumed constant stage efficiency at least in elementary calculations.