An Essential Cause of Stall Stagnations in Compressor Surges

Nobuyuki Yamaguchi 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1

The author has proposed in the preceding study on the behaviors of infinitesimal perturbations of surge in simplified compressor systems that the occurrences of stagnations could be closely related with the travelling wave conditions of the surge oscillations through the phase-differences and the propagations along the flowpaths. The concept was applied to real situations of systems of compressors and flowpaths in the present study. It resulted in a non-dimensional parameter named flowpath-average reduced resonance frequency, fRav, which is an equivalent of the phase-propagation parameter proposed in the preceding study. It is finally a product of the resonance frequency of the system and the time required for the fluid particles to pass through the whole flowpath, namely, the total number of excitations that the fluid particles suffer in the time. A number of numerical experiments on compressor surges have demonstrated that the fRav parameter could explain the cause of surge stagnations very simply and clearly. It has values of 1.5 – 3 at the stagnation boundaries for variations in flowpath configurations and compressors having a single-stage to nine stages. It means that the stagnations occur for the total number of the excitation cycles less than 1.5-3. It could be the most essential cause of the stagnations. In other words, deep surges could develop only after the fluid particles have experienced more number of cycles of the excitations in the passing time. In further, the fRav parameter is made more comprehensive by multiplication of the compressor tip Mach number Mt, i.e., fRav×Mt, which gives a nearly constant value of 1.5 over a wide range of flowpath configurations and tip speeds of compressors, for relatively small number of stages. Those parameters not only suggest the essential cause of surge stagnations, but also are the simplest and clearest measurers of stagnation boundaries. It is much easier to apply in real situations of the systems than any of the parameters proposed so far. However, for multi-stage compressors in long delivery flowpaths and in off-design operations, the parameters appear to deviate somewhat from the constant value.

A Comparison of Surge Behaviors in Multi-Stage and Single-Stage Axial Flow Compressors

Yamaguchi, Nobuyuki Korean Society for Fluid machinery 2016 International journal of fluid machinery and syste Vol.9 No.4

Information on the surge behaviors and stall stagnation boundaries for a nine-stage axial flow compressor are summarized on the basis of analytical data in comparison with those for a single-stage one, with attention to the pressure ratio effect. The general trends of the surge loop behaviors of the pressure-mass flow are similar for both compressors including the fact that the subharmonic surges tend to appear very near the stall stagnation boundaries. With respect to the nine-stage compressor, however, the mild loops in the subharmonic surges tend to be very small in size relative to the deep loops, and at the same time, insufficient surge recovery phenomenon, which is a kind of subharmonic surge, appears also far from the stagnation boundary for relatively short delivery flow-paths. The latter is found to be a rear-stage surge caused by unstalling and re-stalling of the rear stages with the front-stages kept in stall in the stalled condition of the whole compressor, which situation is caused by stage-wise mismatching in the bottom pressure levels of the in-stall multi-stage compressor. The fundamental information on the stall stagnation boundaries is given by a group of normalized geometrical parameters including relative delivery flow-path length, relative suction flow-path length, and sectional area-pressure ratio, and by another group of normalized frequency parameters including relative surge frequencies, modified reduced resonance frequencies, and modified reduced surge frequencies. Respective groups of the normalized parameters show very similar tendency of behaviors for the nine-stage compressor and the single-stage compressor. The modified reduced resonance frequency could be the more reasonable parameter suggesting the flow-induced oscillation nature of the surge phenomena. It could give the stall stagnation boundary in a more unified manner than the Greitzer's B parameter.

Genesis of Researches on Surges in Pumping Systems in Japan

Nobuyuki Yamaguchi,Yoshinobu Tsujimoto 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.1

Researches on the mechanism of surging and the surge behaviors in the systems of pumps, or fans or compressors, and the effects of flow-paths had been initiated and had made a great progress in Japan in the decades from the nineteen-forties to the nineteen-sixties. In 1947, the essential cause of the surges, i.e., self-excited oscillation nature of the flow-system, was discovered analytically by Professor Sumiji Fujii of Tokyo University, and most of the characteristic behaviors of the phenomena had been explained clearly. Successive studies by many other Japanese researchers continued to prove experimentally the mechanism, to extend the analytical studies, and to attempt preventing surge occurrence, etc. in the following two decades. The historical information on the early surge studies could be helpful to some concerned people. At the same time, the basic and plain ways of discussions and reasoning about the phenomena in the pioneering researches could give us much to be learned even in the present time of high-power computing systems. Regrettably, many of the original research works have been published only in Japanese. The present review introduces very briefly the situations in memories of the pioneering researchers and engineers.

Development of a Simulation Method of Surge Transient Flow Phenomena in a Multistage Axial Flow Compressor and Duct System

Yamaguchi, Nobuyuki Korean Society for Fluid machinery 2013 International journal of fluid machinery and syste Vol.6 No.4

A practical method of surge simulation in a system of a high-pressure-ratio multistage axial flow compressor and ducts, named SRGTRAN, is described about the principal procedures and the details. The code is constructed on the basis of one-dimensional stage-by-stage modeling and application of fundamental equations of mass, momentum, and energy. An example of analytical result on surge behaviors is included as an experimental verification. It will enable to examine the transient flow phenomena caused by possible compressor surges and their influences on the system components in plant systems including high-pressure-ratio axial compressors or gas turbines.

Surge Phenomena Analytically Predicted in a Multi-stage Axial Flow Compressor System in the Reduced-Speed Zone

Yamaguchi, Nobuyuki Korean Society for Fluid machinery 2014 International journal of fluid machinery and syste Vol.7 No.3

Surge phenomena in the zone of reduced speeds in a system of a nine-stage axial flow compressor coupled with ducts were studied analytically by use of a surge transient simulation code. Main results are as follows. (1) Expansion of apparently stable, non-surge working area of the pressure vs. flow field beyond the initial stage-stall line was predicted by the code in the lower speed region. The area proved analytically to be caused by significantly mismatched stage-working conditions, particularly with the front stages deep in the rotating stall branch of the characteristics, as was already known in situ and in steady-state calculations also. (2) Surge frequencies were found to increase for decreasing compressor speeds as far as the particular compressor system was concerned. (3) The tendency was found to be explained by a newly introduced volume-modified reduced surge frequency. It suggests that the surge frequency is related intimately with the process of emptying and filling of air into the delivery volume. (4) The upstream range of movement of the fluid mass having once passed through the compressor in surge was found to reduce toward the lower speeds, which could have caused additionally the increase in surge frequency. (5) The concept of the volume-modified reduced surge frequency was able to explain, though qualitatively at present, the behaviors of the area-pressure ratio parameter for the stall stagnation boundary proposed earlier by the author.

A Study on the Fundamental Surge Frequencies in Multi-Stage Axial Flow Compressor Systems

Nobuyuki Yamaguchi 한국유체기계학회 2014 International journal of fluid machinery and syste Vol. No.

Surge phenomena in multi-stage axial flow compressors were studied with attention to the frequency behaviors. A new parameter “volume-modified reduced surge frequency” was introduced, which took into consideration the essential surge process, i.e., emptying and filling of the working gas in the delivery plenum. The behaviors of the relative surge frequencies at the stall stagnation boundaries, compared with the corresponding duct resonance frequencies, have demonstrated the existence of two types of surges; i.e., a near-resonant surge and a subharmonic surge. The former, which has fundamentally a near-resonance frequency, occurs predominantly at the stall stagnation boundary for the short-and-fat plenum delivery flow-path and the long-and-narrow delivery duct flow-path, and possibly in the intermediate conditions. The latter, which has a subharmonic frequency of the fundamental near-resonant one and occurs mainly in the inter-mediate zone, is considered to be caused by the reduced frequency restricted to a limited range. In relation with those dimensionless frequencies at the stall stagnation boundary, the surge frequency behaviors in more general situations away from the boundaries could be estimated, though very roughly.

Surge Phenomena Analytically Predicted in a Multi-stage Axial Flow Compressor System in the Reduced-Speed Zone

Nobuyuki Yamaguchi 한국유체기계학회 2014 International journal of fluid machinery and syste Vol. No.

Surge phenomena in the zone of reduced speeds in a system of a nine-stage axial flow compressor coupled with ducts were studied analytically by use of a surge transient simulation code. Main results are as follows. (1) Expansion of apparently stable, non-surge working area of the pressure vs. flow field beyond the initial stage-stall line was predicted by the code in the lower speed region. The area proved analytically to be caused by significantly mismatched stage- working conditions, particularly with the front stages deep in the rotating stall branch of the characteristics, as was already known in situ and in steady-state calculations also. (2) Surge frequencies were found to increase for decreasing compressor speeds as far as the particular compressor system was concerned. (3) The tendency was found to be explained by a newly introduced volumemodified reduced surge frequency. It suggests that the surge frequency is related intimately with the process of emptying and filling of air into the delivery volume. (4) The upstream range of movement of the fluid mass having once passed through the compressor in surge was found to reduce toward the lower speeds, which could have caused additionally the increase in surge frequency. (5) The concept of the volume- modified reduced surge frequency was able to explain, though qualitatively at present, the behaviors of the area- pressure ratio parameter for the stall stagnation boundary proposed earlier by the author.

Development of a Simulation Method of Surge Transient Flow Phenomena in a Multistage Axial Flow Compressor and Duct System

Nobuyuki Yamaguchi 한국유체기계학회 2013 International journal of fluid machinery and syste Vol.6 No.4

A practical method of surge simulation in a system of a high-pressure-ratio multistage axial flow compressor and ducts, named SRGTRAN, is described about the principal procedures and the details. The code is constructed on the basis of one-dimensional stage-by-stage modeling and application of fundamental equations of mass, momentum, and energy. An example of analytical result on surge behaviors is included as an experimental verification. It will enable to examine the transient flow phenomena caused by possible compressor surges and their influences on the system components in plant systems including high-pressure-ratio axial compressors or gas turbines.

Genesis of Researches on Surges in Pumping Systems in Japan

Yamaguchi, Nobuyuki,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2016 International journal of fluid machinery and syste Vol.9 No.1

Researches on the mechanism of surging and the surge behaviors in the systems of pumps, or fans or compressors, and the effects of flow-paths had been initiated and had made a great progress in Japan in the decades from the nineteen-forties to the nineteen-sixties. In 1947, the essential cause of the surges, i.e., self-excited oscillation nature of the flow-system, was discovered analytically by Professor Sumiji Fujii of Tokyo University, and most of the characteristic behaviors of the phenomena had been explained clearly. Successive studies by many other Japanese researchers continued to prove experimentally the mechanism, to extend the analytical studies, and to attempt preventing surge occurrence, etc. in the following two decades. The historical information on the early surge studies could be helpful to some concerned people. At the same time, the basic and plain ways of discussions and reasoning about the phenomena in the pioneering researches could give us much to be learned even in the present time of high-power computing systems. Regrettably, many of the original research works have been published only in Japanese. The present review introduces very briefly the situations in memories of the pioneering researchers and engineers.

Analytical Surge Behaviors in Systems of a Single-stage Axial Flow Compressor and Flow-paths

Nobuyuki Yamaguchi 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.1

Behaviors of surges appearing near the stall stagnation boundaries in various fashions in systems of a single-stage compressor and flow-path systems were studied analytically and were tried to put to order. Deep surges, which enclose the stall point in the pressure-mass flow plane, tend to have either near-resonant surge frequencies or subharmonic ones. The subharmonic surge is a multiple-loop one containing, for example, in a (1/2) subharmonic one, a deep surge loop and a mild surge loop, the latter of which does not enclose the stall point, staying only within the stalled zone. Both loops have nearly equal time periods, respectively, resulting in a (1/2) subharmonic surge frequency as a whole. The subharmonic surges are found to appear in a narrow zone neighboring the stall stagnation boundary. In other words, they tend to appear in the final stage of the stall stagnation process. It should be emphasized further that the stall stagnation initiates fundamentally at the situation where a volume-modified reduced resonant-surge frequency becomes coincident with that for the stagnation boundary conditions, where the reduced frequency is defined by the acoustical resonance frequency in the flow-path system, the delivery flow-path length and the compressor tip speed, modified by the sectional area ratio and the effect of the stalling pressure ratio. The real surge frequency turns from the resonant frequency to either near-resonant one or subharmonic one, and finally to stagnation condition, for the large-amplitude conditions, caused by the non-linear self-excitation mechanism of the surge.