Axial Thrust Balancing Research Articles

터보펌프 능동 축추력 발란싱 성능 해석

터보펌프 능동 축추력 발란싱 성능 해석

Numerical Analysis on the Effect of J-groove on Flows in Narrow Gaps between Rotating Disk and Casing

During operation and working of turbo machines, axial thrust balancing is important. To control and balance the axial thrust, a very simple method using shallow radial grooves mounted on the casing wall, called “J-groove”, was proposed, and studied experimentally[1]. This paper presents a numerical study of the effect of J-groove on the flow in the narrow gap along enclosed rotating disks based on open-source CFD software. It is seen that the difference in pressure between the hub and shroud tip is increased with the increasing number, depth, and length of J-groove. But in the case of increasing width of J-groove, the pressure loss along the radius decreases when the ratio of the groove width to the outer radius W is less than 0.2 and increases when W greater than 0.2.

Investigating the Influence of Impeller Axial Thrust Balance Holes on the Flow and Overall Performance of a Cryogenic Liquid Turbine Expander

Abstract An excessive rotor axial thrust in any turbomachine can cause critical operational problems, and rotor axial thrust balancing has always attracted much attention. The present numerical study is focused on axial thrust balancing for a cryogenic liquid turbine expander, whose axial thrust balancing is typically challenging because of its small impeller size and large axial thrust. A computational fluid dynamics (CFD) simulation is conducted in a real turbine expander environment constituted by main and gap flow domains with allowing for the thermodynamic effect of liquefied air. The balance hole influential mechanism on the main and gap flows is explored, and its influence on the expander axial thrust and overall performance is quantified. The results show that the use of balance holes creates a highly swirling gap flow, and the static pressure over the impeller disk back-side surface decreases to produce a small axial component force and axial thrust, but the turbine expander overall efficiency drops by 1.1 and 2.8 points at 100% and 50% design flow, respectively, due to an increased internal leakage loss and distorted impeller flow. In addition, a parametric study is conducted to analyze the effect of balance hole diameter, circumferential position, and radial position on expander axial thrust and overall performance. The results indicate that the axial thrust is sensitive to both the balance hole diameter and circumferential position but less sensitive to its radial position, while the overall efficiency is influenced by all three parameters.

100bar급 담수화용 고압 해수펌프 개발

We developed a 7-stage pump for the seawater desalination. The pump was aimed at the performance-level of 300m³/h, head 700m, and max. pressure 100 bar. In the design, the high pressure, erosion resistance and erosivity are closely considered and the balance-disk axial thrust balancing is used. Three-dimensional flow analysis is performed to evaluate the design, and the test demonstrated the performances of total head, 787m, and efficiency, 85.2%.

Axial Thrust Balancing in High-Temperature Cylinders of Steam Turbines during Transients in Combined-Cycle Units

The effect of magnitude and direction of the axial thrust during steam turbine transients on the starting technology is investigated. The behavior of the axial thrust during start-up of a steam turbine with a combined high/intermediate pressure cylinder operating in a single-bypass or two-bypass thermal cycle is presented. At different stages of start-up, varying steam pressure at the turbine inlet and in its flow path can result in a change in the temperature of thrust bearing pads and the magnitude and direction of the axial thrust acting on them. During start-ups with a two-bypass thermal scheme for steam admission to the turbine and its rotor acceleration, connection of the steam turbine generator to a grid and its initial loading are performed with steam supply through intermediate pressure-control valves. In this case, the high-pressure cylinder (HPC) is under “negative pressure” or “countercurrent” conditions passing steam from the exhaust via the bypasses of the check valves in the “cold” reheat steam lines and removing this steam to the condenser via the drains of high-pressure crossover pipelines and from the high-pressure cylinder casing. Connection of the turbine HPC for normal steam supply and change-over to the once-through scheme of steam admission to the turbine are carried out after connection of the turbine generator to the grid and initial loading of the turbine by partial opening of the HP control valve and full opening of the intermediate pressure (IP) control valves. At the same time, the valves of quick-acting pressure-reducing and cooling units (QAPRCU) BROU-1 and BROU-2 are closed to maintain the specified high and intermediate pressure of steam upstream from them. These process operations change the axial thrust acting on the thrust bearing pads with a corresponding change in the pad temperature. The effect of variable axial thrust on the steam turbine maneuverability is examined. Methods are proposed for balancing the axial thrust during start-ups of steam turbines in combined-cycle units having different thermal schemes.

Investigation of axial thrust deviation between the theory and experiment for high-speed mine submersible pump

In this article, three types of high-speed mine submersible pumps were designed and experimented. During the reliability performance test, the axial thrust balancing device of GFQ150-700 was overloaded and damaged due to an unsuitable designed value of axial thrust. The designed hydraulic axial thrust with the actual value is compared in this article, and the reason for axial thrust deviation is discussed. Results show that axial thrust of the theoretical calculation is close to the numerical simulation value at a certain extent. GFQ100-1000 obtains the maximum theoretical axial thrust, while the maximum simulated value is produced in GFQ150-700, and that is corroborated by experiments. The axial blade force is related to the pump stage and area differences between the blade suction and pressure surface. Due to the increasing stage in GFQ100-1000, the axial blade force increases to a remarkable value in an opposite direction with respect to GFQ150-700. The opposite blade force offsetting other hydraulic forces in GFQ100-1000 is responsible for the maximum hydraulic axial thrust emerges in GFQ150-700 instead of GFQ100-1000.

Laboratory Measurements the Rise in Power Consumption Resulting from the Use of a Finned Rotating Disc at a Centrifugal Water Flow

The pump structure may involve using fins on the impeller discs to reduce axial thrust. The fins are also used to reduce pressure acting on the discharge-side stuffing box, throw mechanical impurities away and protect the seal against mechanical impurities at the pump impeller inlet. Extensive laboratory tests were performed on finned discs at the water centrifugal flow for different fin widths and gaps between fins and the casing and for different water flow rates. The resulting change in power consumption was determined compared to unfinned discs. The analysis results indicate that fitting the disc with fins involves an increase in power consumption. The consumption rise depends on the centrifugal volumetric flow rate, the fin width and the size of the gap. The dependence of power consumption on the gap size is non-monotonic—the gap can be optimized to minimize power consumption. The determination of the rise in the consumption of power resulting from fitting the disc with fins and depending on the centrifugal volumetric flow rate is an original outcome of the analysis presented in this paper. The dependence was defined for fins with different values of width and for different sizes of gap. The presented results of the testing can be used in the analysis of power consumption of both finned and unfinned rotating discs. The analysis of power consumption in the impeller pump axial thrust balancing system using balancing vanes is another example of the application of the obtained results.

Experimental laboratory tests of the pressure drop resulting from the liquid flow through orifices in a rotating disc

The article presents experimental laboratory tests aiming to determine the pressure drop occurring as a liquid flows between two spaces through orifices in a rotating disc.A one-dimensional flow model was proposed to establish a dimensionless coefficient of discharge. A dimensional analysis of the problem was conducted for orifices spaced at a certain diameter in a rotating disc, i.e. characterized by a certain transportation velocity. An original testing station as well as a measuring system were designed and installed, and extensive laboratory tests were performed.The dimensional analysis results prove that the coefficient of discharge through orifices in a rotating disc depends on the Strouhal number referred to the orifice. This dependence was confirmed by laboratory tests performed for a water flow. The testing resulted in a formula which proved convenient for engineering applications and which defines the coefficient of discharge through orifices depending on their transportation velocity and the liquid velocity in them. The finding of this dependence is an original result of the testing.The obtained experimental dependence allows a calculation of the pressure drop occurring as the liquid flows through orifices in a rotating disc. A particular instance of the dependence application is designing an axial thrust balancing system based on balancing orifices in impeller pumps, which makes it possible to correctly design the axial thrust balancing system and determine volumetric losses.

Stability of an Axial Thrust Self-Balancing System

Rocket pumps are characterized by high speed and high delivery pressure. Therefore, balancing of axial thrust acting on the rotor assembly is one of the most important factors. To realize complete axial thrust balancing, a balance piston-type axial-thrust self-balancing system is often used in rocket pumps. This axial thrust balance system acts dynamically as if it were a mass and spring system, although there is no mechanical spring. Sometimes, large amplitude axial vibration is observed in a liquid hydrogen turbopump. Too much vibration in the axial direction causes metal-to-metal rubbing, resulting in fatal accidents of rocket turbopumps. However, the cause of the vibration has not yet been clarified. In the present study, the self-balancing system was modeled by combining the mechanical structure and the fluid system in a calculation program of one-dimensional multidomain system analysis software. Stability of the system was investigated using this program and the possibility of existence of self-excited vibration was confirmed. Effects of geometry, fluids, viscous damping, radial pressure drop in the chamber, and orifice flow coefficients on the stability of the balance piston system were examined. As a result, it was concluded that large compressibility of liquid hydrogen was the cause of the large amplitude axial vibrations. With the results of analyses, methods to stabilize the system in order to suppress the axial vibration were suggested.

Internal Flow and Axial Thrust Balancing of a Rocket Pump

Large axial thrust is produced on the rotor assembly of high-pressure rocket pumps. Thus, to ensure the reliability of bearings supporting the high rotational speed rotor, precise axial thrust balancing is essential. To realize complete axial thrust balancing, the back shroud of the main impeller is employed as the balance piston of a self-balancing type axial thrust balancing system in which the rotor assembly moves axially to compensate unbalance axial force. In this balancing system, which is often applied, complicated internal flow characteristics and pressure distributions are very important for predicting the precise characteristics of the axial thrust produced by the system. In the present study, a calculation method for analyzing the internal flow system taking into account effects of boundary layer conditions and angular momentum change in the impeller side-chambers is applied to the system combining the balance piston and grooves on the casing wall of the balance piston chamber. The analysis program is able to detect phenomena which could not be captured in past calculations and is effective for calculating internal flow characteristics much faster than possible with CFD analysis. A combination of balance piston and grooves on the casing wall of the balance piston chamber was confirmed to be suitable for extending the dynamic range of axial thrust balancing although installation of the grooves increased the leakage flow rate and friction torque at the same time.

저비속도 원심 회전차 외경가공에 따른 축추력 불균형을 감쇄시키기 위한 평형 피스톤 수정방안에 관한 고찰

회전차 외경 가공에 따른 축추력 평형 및 체적 효율 변화에 대하여 고찰하였다. 평형장치로 평형 피스톤이 장착된 저비속도 다단 원심 펌프를 연구 대상으로 해석을 수행하였다. 수평축 다단 펌프와 2종의 수직축 다단 펌프에 대해 해석 수행을 한 결과, 회전차 외경 가공에 의해 펌프 전방으로 추가적인 축추력이 발생하였다. 이러한 축추력 불균형은 수평축 펌프보다 수직축 펌프에서 크게 발생하였다. 축추력 불균형을 방지하기 위해 평형피스톤의 외경을 증가시키는 방안을 제시하였고, 이를 위해 필요한 평형피스톤의 직경 변화율을 산출하였다. 피스톤의 직경 변화량은 회전차 외경 가공률에 비례하여 증가 하였다. 피스톤 직경 변화량이 클수록 틈새 면적 증가로 인해 체적효율이 감소하므로, 피스톤의 길이를 함께 증가시켜 체적 효율의 감소를 방지하는 것이 효과적이다.

J051041 ロケット用ポンプ内部流れの動特性解析([J05104]流体機械の研究開発におけるEFD/CFD(4))

Internal flow of a cryogenic rocket turbopump is rather complicated compared to ordinary pumps. In order to design stable axial thrust balancing system, dynamic analyses of the internal flow system is essential. In the present study, analysis program to analyze dynamic characteristics of leakage flow through the axial thrust balancing system was developed. In the program, structure of the balance piston type axial thrust balancing system and the internal flow passages are combined. Pressure perturbation was imposed on the inlet of the balancing system and the dynamic response of the axial thrust balancing system was evaluated. Calculated results showed that the system has resonant frequencies which depend on the fluids and the other parameters of the system.

ＬＥ‐７液酸ターボポンプの軸推力釣合わせ

A self-balancing type axial-thrust balancing system referred to as “balance piston” was applied to the LE-7 LOX turbopump, the discharge pressure of which exceeds 30MPa. A research model turbopump showed that pressure distribution in the balancing chamber deviated greatly from the predicted distribution and that the axial clearance of the balancing-chamber inlet orifice became too small to maintain safety. Consequently, we attempted to determine the cause of these phenomena and to find methods of ensuring sufficient axial clearance of the inlet orifice. Two methods were attempted. In the first method, balancing holes directly connecting the balancing chamber and the main impeller inlet were made. In the second method, grooves were made on the casing wall facing the main impeller front shroud.

Paper 4: Development of High-Pressure Boiler Feed Pumps in Britain during the Last Decade

This paper traces the evolution of the high-pressure feed pump in this country over the last decade, concentrating on its application in land-based, steam power plant. The influence of the choice of feed system and the effect of mounting feed water flow rates, pressure, and temperature on the design of the feed pump is discussed. Advantages and disadvantages of the various methods of driving a feed pump are enumerated and attention given to the reasons for the adoption of higher running speeds, and the means whereby high-speed pumps have been accommodated in view of their higher net positive suction head requirements. Material selection and component design is also considered in the light of the changing requirements brought about by larger size, more onerous operating conditions, and higher running speed. Glands, axial thrust balancing devices, impeller mountings, controls, and high-pressure joints, are each briefly discussed.