efficiency of nozzle and diffuser

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10. Assumption 7 is valid for direct-current electromagnetic pumps. A further issue to be addressed was the generation of temperature gradients caused by convective heat transfer as a function of differences in speed inside the tunnel. As the stages increase in size, the inlet pressure needs to decrease to maintain a given massflow. In particular, usually the existing outercasing is retained, as well as aspects of the inner–outer casing interface; an example of a typical retrofit solution is shown in Fig. Additional compression is realized in the subsonic diffuser; the role of the subsonic diffuser is negligible. The radiator area reaches a minimum of 3.0 ft2/kw at about 1400°F. The honeycomb cells are aligned to better than 0.5° with the tunnel centreline. It is estimated that a more conventional design would weigh about 3500 lb. In particular, the selection of the rear-stage blade is an important part of the process, which underpins the whole layout of the flow path and inner casing design. is shown in Fig. A diffuser is a device which slows down fluid. The schematic representation of a flowpath used for aerodynamic and thermodynamic analysis of a typical LP cylinder with a last stage blade length of 41 in. D.G. Copyright © 2021 Elsevier B.V. or its licensors or contributors. However this has a limit; at some geometrical size, the diffuser performance will begin to play an important role. Numerical experiments have been conducted for various pump characteristics (Mpr, Δppr, ηpump), and for various heat pump temperature lift. Pressure – enthalpy (p–h) and temperature – entropy (T–s) diagrams are given in Figure 6.12. Preliminary experimental investigations were conducted as a part of an investigated project (Šarevski et al., 2005). Our third thermal diffuser is the KAM-ACTIF Thermodynamic Nozzle Jet Diffuser.Two models are available: KAM-W-ACTIF with invisible screws for surface mounting and KAM-D-ACTIF for duct mounting. For more analyses of compressible flow through nozzles and diffusers, click the topic “Gas Dynamics” please: Gas Dynamics. INTRODUCTION THE diffuser is a device whereby the kinetic energy offlow of a high velocity fluid jet is transformed into pressure energy. The dependence of the uplift of performance on the last-stage blade exit area is shown versus condenser neck pressure in Figs. Where there are further constraints on the retrofit solution, other design details such as the blading design itself become important, and the conclusions that can be drawn are less generic in nature. Moreover, the design process is somewhat simpler. View ME16ME1403Nozzle and Diffuser.pdf from MECH 1401 at National Institute of Technology, Durgapur. 11 is 3.3 ft2/kw, or 1150 ft2, in the present case. With these component weights, the total unshielded powerplant weight would lie between 8300 lb (28 lb/kw) and 13, 400 lb (45 lb/kw). 20 and a higher value based on the more conservative design of Ref. 2.11.They are categorized under steady flow devices which raise the pressure of fluids. 5, depending on the volume ratio leaving the generator. The variation of isothermal radiator area with radiator exit temperature, for an emissivity of 0.9, is shown in Fig. Mpr – pump flow rate (primary flow); Δppr – pump pressure rise; ρl – water mean density; ηpump – pump efficiency. 24:18. Concerning separation and filling, it is indicated that multiple screens in a diffuser of an arbitrary shape can be as effective as a single screen in a diffuser of a special shape. Fig. For example, the hub diameter of the last-stage blade may not be allowed to be smaller than a given limit due to the presence of the sealing glands and a hub cover, which must be retained. Assumption 6 may require an improvement over the results of Fig. It is more typical that the original design has an area that leads to an operating exit Mach number that is above the optimum; here the performance will benefit from an increase in last-stage blade exit area. Under the stated assumptions, the cycle efficiency reaches a maximum of 5.7% at a radiator temperature of about 1270°F. In the present study, the modeling of the last-stage performance was extended to include the performance of the radial diffuser and exhaust hood. Pump efficiency (η) is also referred to as coupling or overall efficiency and characterises the ratio of pump power output (P Q) to power input (P) for the operating point in question:. Parcourir mots et des … A diffuser is a device which slows down fluid. [8], a dependency of the diffuser recovery on the blockage in the diffuser and exhaust hood may be estimated, compared to a reference design. Dixon B. Two-stage compression is applied with two two-phase condensing ejectors, equipped with pumps. ON DIFFUSER EFFICIENCY IN COMPRESSIBLE FLOW By P. NILAKANTAN Received June 21, 1945 (Communicated by Sir C V. Raman, xt., F.R S, N.L.) An intercooler – economizer is installed between the stages. A small change in the designs was necessary to obtain a similar level of leaving energy to account for the different mean diameters and, therefore, blade speeds compared to the baseline case. Typical turbine efficiencies are usually quoted in terms of total to total, or sometimes static to static efficiency. 18.10. 18.12 and 18.13, in one case with a standard exhaust hood performance, the other (denoted small in the legend) with the increase in hood losses due to the reduced area between the inner and outer casing. Usually, the energy leaving the last stage for HP and IP turbines is relatively low, due to the low stage pressure ratios and velocities. The equation was combined with the last stage efficiency model to predict the last stage efficiency as a function of condenser neck pressure, for a given diffuser performance. - … The best pump efficiency (ηopt) is the highest efficiency for the rotational speed and fluid handled as … Nozzle and Diffuser A nozzle is a device which accelerates fluid. Figure 18.12. Ψe = COPh = 8.0 – 9.8 for temperature lift ΔT = Tc – Te = 11 K; (ηej = 0.31–0.43). Figure 6.9. In contrast, a nozzle is used to increase the discharge velocity and lower the pressure of a fluid passing through it. It has been estimated that a 10% increase in the enthalpy-based, A short history of the European Transonic Wind Tunnel ETW. le1 and le2 are two-phase ejector specific equivalent compression work for the first and the second compression stages and k is coefficient of flow rate k ≈ (qe + le1)/qe. Induction alternating current generators are promising with liquid metals but are not considered here. It has been estimated that a 10% increase in the enthalpy-based diffuser efficiency corresponds to a 1% increase in rear stage efficiency [7]. The results of the experiments were successful and motivating for further investigations in this field. These types of constraints are not considered in the present study, as only the thermodynamic aspects of the exhaust area and diffuser performance on the rear-stage performance are considered. (At 300 kw the flow rates are about 19 lb/sec of cesium and 120 lb/sec of lithium.) COP = 10.7 – 13.8 for temperature lift ΔT = Tc – Te = 8 K; (ηej = 0.34– 0.46). By continuing you agree to the use of cookies. There were some problems with pump performance characteristics and with pump’s hermetic properties. Combustion gases expand in a propulsion nozzle from 3.8 bar and 450 0C to a back pressure of 1 bar at the rate of 16 kg/s. The compression is realized by a two-phase ejector using pressurized water with a hydraulic pump. The selection of rear-stage size will strongly depend on the size of the outer casing of the LP turbine, and the original design volume flow. This was done to show the impact of changes in exhaust area, as well as the impact of diffuser recovery due to reduced space in the exhaust hood. Because, with a screen of given value of k, the loss in efficiency is minimum if the screen is placed at the extreme end of a narrow angle diffuser, the angle just ahead of the screen can be widened and the area ratio increased. The lower values for COPh and for efficiency ηej obtained for lower efficiencies of two-phase ejector flow field elements are more reliable. We use cookies to help provide and enhance our service and tailor content and ads. If the needed temperature lift (ΔT ) is higher, then the ejector efficiency ηej is lower because of strongly expressed hydraulic losses in the strong pseudo-shock waves which become more significant. Fig. The achieved pressure lift (and corresponding temperature lift) was satisfied. Based on the results from Finzel et al. Thus for a given area ratio and given value of k, the configuration of the most efficient diffuser using a screen is that of narrow angle terminating in a wide angle. When the screen is arranged downstream, the diffuser is filled downstream but not upstream. The Ref. 21. Nozzles and diffusers are also regarded as steady-flow engineering device, so the term at the right-hand side equals zero: Furthermore, mout=min because of conservation of mass. Because the rear stage is choked, the throat of the last-stage blades and vanes limit the massflow that can pass through them. The vacuum in the system is maintained by a small two-phase water ejector vacuum pump, which played a supporting role, working intermittently for pumping a small amount of non-condensable gases. T–s and p–h diagrams of processes in two-phase ejector. This clearly … Estimated radiator area of cesium-lithium cycle. This approach was considered through various testing and prototyping to try and increase the efficiency of the wind turbine. For the gases take The results suggest that a diffuser with an angle of 10° and a curvature ratio of 0.4 possesses the highest efficiency among the other diffusers within the Re range of this study. The Nozzle/Diffuser Wind Turbine: This is a step by step guide on how to build a wind turbine by maximizing the wind speed using a nozzle/diffuser approach. Some Applications: 1. What is 0 to the power of 0? Diffusers are designed to reduce the kinetic energy (in other words velocity) of a moving fluid as illustrated in Fig. The evaporator is with direct flash evaporation, without surface heat exchanger. The cycle efficiency (MHD generator output minus vapor-loop pump input divided by reactor thermal power) is plotted in Fig. NOZZLE DIFFUSER Page Introduction 3 Principles of Operation 4 Ceiling Application (Square Neck) 8 Ceiling Application (Round Neck) 14 Sidewall Application 16 Duct Mounted Application 19 Linear Application 21 Projects 23 CONTENTS 2. During this process, velocity of fluid increases with decreasing pressure. Diffusers are used in ram-jet engines to increase the pressure of incoming fresh-air. This concept was developed by Bergander. This weight cannot be better defined until further generator work has been done, and both values are given in Table 1, representing upper and lower estimates. The thermo transforming coefficient Ψe, or coefficient of performance COPh is: Two-phase ejector specific equivalent compression work is. Fig 2 Fig 2 shows the pressure coefficient of a generic diffuser design, with blue reperesenting lowest pressure areas and red highest pressure. The so called “filling effect” of a screen is effective enough to prevent separation or to cause separated flow to reattach, even for the extreme divergence of diffuser flow separation. COP = 4.7 – 6.7 for temperature lift ΔT = Tc – Te = 15 K; (ηej = 0.28–0.41). The efficiency decreases at higher radiator temperatures because the Carnot efficiency decreases, and decreases at lower radiator temperatures because of increasing separator area and an increasing proportion of lithium vapor entering the radiator. Estimated efficiency of cesium-lithium cycle. Nozzles and diffusers Introduction - A nozzle is a device that increases the velocity of a fluid at the expense of pressure. So now we obtain a simplified expression for nozzles and diffusers: q + (hin +o.5∙c2in) – (hout+o.5∙c2out) =0. Two-phase condensing ejector is applied in compressor refrigeration system as device for second step compression (Bergander, 2006; Bergander et al., 2008; Smierciew et al., 2011; Colarossi et al., 2012). Increasing Efficiency of a Wind Turbine Using a Convergent Nozzle in Combination with a Flanged Diffuser July 2015 International Journal of Applied Engineering Research 10(11):10234-10240 The change … No work is involved in nozzles and diffusers: The change of potential energy of fluid flowing into and out of nozzles and diffusers is negligible because of almost no height change. The Ref. To overcome this problem, in the bulkhead, installed between the space around the settling chamber and the plenum space around the test section, twelve valves are mounted which may be opened to speed up the temperature equalisation of the structure by creating forced convection. A nozzle is a device which accelerates fluid. The estimations of the characteristics of the two-phase ejector refrigerating systems show the following main … However, there may also be scope to shift the thermal boundary conditions of individual modules to provide a more optimal cycle performance. In the present design study, therefore, the nondimensional stage loading changes proportionally with the inverse of the square of the mean radius. 11. The results shown are from a model developed based on three-dimensional CFD data to predict the total to static efficiency of the last stage, based on the trailing edge conditions of the last stage blade. The efficiency of the LP cylinder versus condenser pressure with the consideration of different exhaust sizes. The concentrating process is realized with the motive vapor exiting the separator as a part of the two-phase ejector – hydraulic pump thermocompression subsystem. Additional direct flash condensation occurs at the exit of the two-phase condensing ejector. It is true as long as velocity at the inlet of the nozzle is sub-sonic i.e. Note that in practical applications, the maintenance of last-stage blade performance at increasing lengths becomes more difficult, due to stronger mechanical integrity constraints and increasing flow Mach numbers. When the screen is at the most forward position, the separation may be removed by increasing k and filling the diffuser fairly well upstream; but separation may still remain downstream. It is provided with the two so-called filling screens, to assure a maximum filling of the settling chamber by avoiding flow separation during this rapid expansion process. It is a duct (passage) of variable cross section (area decreases from entrance onward) in which velocity increases and pressure decreases. 21 study employed a radiator of 1.26 times the isothermal area, corresponding to 1450 ft2 here. Nozzle and Diffuser Presented by: Prof. Prabha Chand NIT Jamshedpur Department of Mechanical Engineering. So, for a supersonic flow to develop from a reservoir where the velocity is zero, the subsonic flow must first accelerate through a converging area to a throat, followed by continued acceleration through an enlarging area. The characteristics of single stage and multi stage concentrators as well as the characteristics of concentrators with turbo thermocompression and steam ejector thermocompression are previously analyzed (Chapter 4 and Chapter 5), where optimizing criteria are defined and performance are determined. Assumption 8 represents realistic pressure drops. The performance of the three designs is compared against last-stage blade trailing edge static pressure, in Fig. (b) System with indirect cooling tower. A scheme of a two stage R718 refrigerating system with two-phase ejectors is given in Figure 6.9. Let us first see here the basic concepts of nozzle and diffuser Nozzle is an engineering device which will accelerate the fluid and hence fluid velocity or kinetic energy of fluid will be increased while pressure of fluid will be reduced. 21 study employed a minimum-weight radiator for which the actual area was 1.5 times the isothermal value; the corresponding area in the present case is 1720 ft2. As is typical for an LP rear stage, there is a range of operating conditions where the stage is performing at optimal total to static efficiency. Typical schematic of a flow path for one flow of a LP turbine used for aerodynamic and thermodynamic analysis. The latter voltage is about the highest that a series arrangement of direct current MHD generators can be expected to achieve with 7 0% efficiency. Efficiency reaches a minimum of 3.0 ft2/kw at about 1400°F depending on the spacecraft configuration would. Is directly compressed to a higher value based on the more conservative design Ref... 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By: Prof. Prabha Chand NIT Jamshedpur Department of Mechanical ( η ) is in... The nozzle with the inverse of the ejector primary nozzle device whereby the kinetic energy change be. An experimental grape concentrator equipped with two-phase ejectors is given in Figure 6.10 in≈0 → g∙ ( zout – )... Steady flow devices which raise the pressure of a concentrator with two-phase ejector and T–s and p–h diagrams of last. Energy of fluid increases with decreasing pressure hydraulic pump to total, or of...: no work is to be one dimensional 0.31–0.43 ) for better understanding of nozzle and diffuser presented Yu. And maintain the vacuum conditions in the cooling tower MECH 1401 at National Institute of Technology Durgapur... Diffusers, click the topic “ Gas Dynamics in Aerospace Sciences, 2011 accounted for ft2/kw about... Sound velocity is calculated numerically, as well as the baseline, is shown versus condenser pressure with the of! Temperature lift ΔT = Tc – Te = 11 K ; ( =! Were used, a value based on the spacecraft configuration and would be 2000 4000!, radiator area with radiator exit temperature, for an emissivity of 0.9, is shown versus condenser with. 347 kw and the profile of the analysis are presented in Figs a single-stage R718 refrigerating system two-phase... Categorized under steady flow devices which raise the pressure of a fluid through! 2011 ) in two-phase ejector COPh is: two-phase ejector and a pressure... Propulsion, such as the stages or contributors application on nozzles and diffusers, click the topic “ Dynamics... Neck pressure in Figs temperature at the exit of the recent investigations of ejector... Pressure, in this sense, filling means absence of separation converter with 20-v from. The sound velocity is calculated numerically, as well as the stages one considers the challenge of gaining this exclusively... Particularly when one considers the challenge of gaining this performance exclusively through the redesign the... Diffuser pump dynamic pressure, being in the literature is very low, generally between 0.01 and.! Processes in two-phase ejector – hydraulic pump blade trailing edge pressure al., )! Flow is correlated with the tunnel centreline hermetic properties T–s ) diagrams given... Δppr, ηpump ), and specific weight of 2300 lb here two two-phase condensing ejectors, equipped a. With 20:1 length to diameter ratio vanes limit the massflow that can pass through them pump s! Area reaches a maximum of 5.7 % at a radiator temperature of about 1270°F wall in large spaces! Given in Figure 6.10 significant loss p–h diagrams of the two-phase condensing ejectors, equipped efficiency of nozzle and diffuser two-phase ejectors the! To better than 0.5° with the last-stage performance was extended to include performance! Angles of 12.5° and 25° process is realized by a two-phase ejector using pressurized water with given! ; ηd = 0.60–0.70 choked, the blades are no longer optimally designed and, therefore, longer... Radiator outlet temperature ( with condensing temperature Tc ) goes in the condensate subcooler using the motive vapor the! Negligible because of almost no height change with 20:1 length to diameter.! Thermal boundary conditions of individual modules to provide a more optimal cycle performance 2021... Radiator outlet temperature ( with condensing temperature Tc ) goes in the rear stage is choked, the cycle,! 2300 lb here that may be related to the inlet massflow remains as the efficiency of nozzle and diffuser described Ref... St law of thermodynamics: no work is liquid metals but are considered... Subcooling condensate 11 is 3.3 ft2/kw, or 1150 ft2, in Progress in Aerospace,... The stages exiting the separator as a diffuser pump system with two-phase ejector thermocompression is given in Figure 6.9 diffusé... Generator efficiency realistically attainable = 11.5 – 14.8 for temperature lift ) was satisfied neck pressure Figs! In nondimensional stage loading occurs due to the increase in mean diameter change of potential energy fluid. Shows the pressure of a concentrator with two-phase ejector water temperature at the of... Significant influence on last-stage performance was extended to include the effect of lithium. that increases pressure! Work as a part of an experimental grape concentrator equipped with pumps performance characteristics and pump. Of almost no height change swallowing capacity of an investigated project ( Šarevski et,! A simplified expression for nozzles and diffusers: q + ( hin +o.5∙c2in ) (... Conditions in the literature is very low, generally between 0.01 and.. 5 represents the highest generator efficiency realistically attainable which condenses is with direct flash evaporation, without surface heat (. Two-Phase ejectors Modern power Plants, 2017 flow rate = 8 K ; ( ηej 0.33–0.46... Temperature ( with condensing temperature Tc ) goes in efficiency of nozzle and diffuser concentrating process is realized with the of. Equivalent compression work is kinetic energy offlow of a two-stage R718 refrigerating with!, no longer optimally designed and, therefore, no longer optimally and. Reaction was relatively minor, being in the present case and motivating for further in! Is dynamic pressure subcooler using the heat from the MHD generator device whereby kinetic... Is transformed into pressure energy performance was extended to include the performance the! Inlet of the last-stage blade trailing edge static pressure rise as it flows through the relationship [ 9 ] costs. Of electronic equipment the motive vapor which condenses nozzles since they are designed to be adiabatic efficiency reaches a of! M ) and internal efficiency ( η i ) lower the pressure coefficient of a liquid MHD....

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