Radial Gap

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Toru Masuzawa - One of the best experts on this subject based on the ideXlab platform.

  • an ultradurable and compact rotary blood pump with a magnetically suspended impeller in the Radial direction
    Artificial Organs, 2001
    Co-Authors: Toru Masuzawa, Toshiyuki Kita, Yohji Okada
    Abstract:

    : A magnetically suspended centrifugal blood pump has been developed with a self-bearing motor for long-term ventricular assist systems. The rotor of the self-bearing motor is not only actively suspended in the Radial direction, but also is rotated by an electromagnetic field. The pump has a long lifetime because there are no mechanical parts such as seals and motor bearings. An outer rotor mechanism was adopted for the self-bearing motor. The stator was constructed in the central space of the motor. The rotor shaped thin ring was set at the circumferential space of the stator. Six vanes were extended from the upper surface of the rotor toward the center of the pump to construct an open-type impeller. The outer diameter and the height of the impeller are 63 mm and 34 mm, respectively. The magnetic bearing method and the servomotor mechanism were adopted to levitate and rotate the rotor. Radial movements of the rotor and rotation are controlled actively by using electromagnets in the stator. Axial movement and tilt of the rotor are restricted by passive stability to simplify the control. The Radial Gap between the rotor and the stator is 1 mm. A closed-loop circuit filled with water was used to examine basic performance of the pump. Maximum flow rate and pressure head were 8 L/min and 200 mm Hg, respectively. Maximum amplitude of Radial displacement of the impeller was 0.15 mm. The impeller could be suspended completely without touching the casing wall during the entire pumping process. Power consumption of the pump was only 9.5 W to produce a flow rate of 5 L/min against a pressure head of 100 mm Hg. We conclude that the pump has sufficient performance for the implantable ventricular assist system.

  • magnetically suspended rotary blood pump with Radial type combined motor bearing
    Artificial Organs, 2000
    Co-Authors: Toru Masuzawa, Toshiyuki Kita, Kenichi Matsuda, Yohji Okada
    Abstract:

    : A magnetically suspended centrifugal blood pump is being developed with a combined motor-bearing for long-term ventricular assist systems. The combined motor-bearing actively suspends a rotor in a Radial direction to deal with Radial force unbalance in the pump and rotates the rotor by using the electric magnetic field. Therefore, the pump has no mechanical parts such as bearings of the motor and has a long lifetime. The developed pump consists of a thin rotor with a semi open-type 6 vane impeller and a stator to suspend and rotate the rotor. The rotor has 4-pole permanent magnets on the circumferential surface. The outer diameter and the thickness of the rotor are 60 mm and 8 mm, respectively. Axial movement and tilt of the rotor are restricted by passive stability based on the thin rotor structure. Radial movements of the rotor, such as levitation in Radial direction and rotation, are controlled actively by using electric magnets of the stator. The electric magnet coils to produce levitation and rotation forces are constructed on the periphery stator. The p ± 2-pole algorithm and the synchronous motor mechanism are adopted to levitate and rotate the rotor. The Radial Gap between the rotor and the stator is 1 mm. A closed-loop circuit filled with water was connected to the developed pump to examine the basic performance of the pump and the magnetic suspension system. Maximum rotational speed, flow rate, and head were 2,800 rpm, 11 L/min, and 270 mm Hg, respectively. The rotor with the impeller could be suspended completely during the entire pumping process. We conclude the pump with the combined motor-bearing has sufficient performance for the blood pump.

  • development of design methods for a centrifugal blood pump with a fluid dynamic approach results in hemolysis tests
    Artificial Organs, 1999
    Co-Authors: Toru Masuzawa, H. Takano, Eisuke Tatsumi, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe
    Abstract:

    : The purpose of this study was to examine the relationship between local flow conditions and the hemolysis level by integrating hemolysis tests, flow visualization, and computational fluid dynamics to establish practical design criteria for centrifugal blood pumps with lower levels of hemolysis. The Nikkiso centrifugal blood pump was used as a standard model, and pumps with different values of 3 geometrical parameters were tested. The studied parameters were the Radial Gap between the outer edge of the impeller vane and the casing wall, the position of the outlet port, and the discharge angle of the impeller vane. The effect of a narrow Radial Gap on hemolysis was consistent with no evidence that the outlet port position or the vane discharge angle affected blood trauma in so far as the Nikkiso centrifugal blood pump was concerned. The Radial Gap should be considered as a design parameter of a centrifugal blood pump to reduce blood trauma.

  • computational fluid dynamics analysis to establish the design process of a centrifugal blood pump second report
    Artificial Organs, 1999
    Co-Authors: Yuki Miyazoe, Toru Masuzawa, Tomonori Tsukiya, Takashi Yamane, Balazs Asztalos, Yoshiaki Konishi, Kazuyuki Ito, Toshio Sawairi, Seiko Endo
    Abstract:

    To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the Radial Gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.

  • flow visualization study to improve hemocompatibility of a centrifugal blood pump
    Artificial Organs, 1999
    Co-Authors: M. Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki Konishi
    Abstract:

    A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing Gap widths on the flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small Radial Gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small Radial Gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small Radial Gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small Radial Gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small Radial Gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

Yuki Miyazoe - One of the best experts on this subject based on the ideXlab platform.

  • development of design methods for a centrifugal blood pump with a fluid dynamic approach results in hemolysis tests
    Artificial Organs, 1999
    Co-Authors: Toru Masuzawa, H. Takano, Eisuke Tatsumi, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe
    Abstract:

    : The purpose of this study was to examine the relationship between local flow conditions and the hemolysis level by integrating hemolysis tests, flow visualization, and computational fluid dynamics to establish practical design criteria for centrifugal blood pumps with lower levels of hemolysis. The Nikkiso centrifugal blood pump was used as a standard model, and pumps with different values of 3 geometrical parameters were tested. The studied parameters were the Radial Gap between the outer edge of the impeller vane and the casing wall, the position of the outlet port, and the discharge angle of the impeller vane. The effect of a narrow Radial Gap on hemolysis was consistent with no evidence that the outlet port position or the vane discharge angle affected blood trauma in so far as the Nikkiso centrifugal blood pump was concerned. The Radial Gap should be considered as a design parameter of a centrifugal blood pump to reduce blood trauma.

  • computational fluid dynamics analysis to establish the design process of a centrifugal blood pump second report
    Artificial Organs, 1999
    Co-Authors: Yuki Miyazoe, Toru Masuzawa, Tomonori Tsukiya, Takashi Yamane, Balazs Asztalos, Yoshiaki Konishi, Kazuyuki Ito, Toshio Sawairi, Seiko Endo
    Abstract:

    To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the Radial Gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.

  • flow visualization study to improve hemocompatibility of a centrifugal blood pump
    Artificial Organs, 1999
    Co-Authors: M. Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki Konishi
    Abstract:

    A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing Gap widths on the flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small Radial Gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small Radial Gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small Radial Gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small Radial Gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small Radial Gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

  • computational fluid dynamic analyses to establish design process of centrifugal blood pumps
    Artificial Organs, 1998
    Co-Authors: Yuki Miyazoe, Toru Masuzawa, Takashi Yamane, Yoshiaki Konishi, Kazuyuki Ito, Toshio Sawairi, Koki Takiura, Masahiro Nishida, Yoshiyuki Taenaka
    Abstract:

    To establish quantitative, efficient design theories for centrifugal blood pumps, computational fluid dynamics (CFD) analyses were compared to the results of flow visualization tests and hemolysis tests, mainly on the Nikkiso centrifugal blood pump. The results turned out to coincide in the velocity vector plots. CFD analysis revealed that the smaller the Gap is, the greater the shear stress becomes. This tendency becomes even greater with a Radial Gap change. Hemolysis study also indicated that the smaller the Gap is, the greater the hemolysis. CFD analysis in comparison with hemolysis tests could be a useful index for developing blood pumps in the future.

Seiko Endo - One of the best experts on this subject based on the ideXlab platform.

  • development of design methods for a centrifugal blood pump with a fluid dynamic approach results in hemolysis tests
    Artificial Organs, 1999
    Co-Authors: Toru Masuzawa, H. Takano, Eisuke Tatsumi, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe
    Abstract:

    : The purpose of this study was to examine the relationship between local flow conditions and the hemolysis level by integrating hemolysis tests, flow visualization, and computational fluid dynamics to establish practical design criteria for centrifugal blood pumps with lower levels of hemolysis. The Nikkiso centrifugal blood pump was used as a standard model, and pumps with different values of 3 geometrical parameters were tested. The studied parameters were the Radial Gap between the outer edge of the impeller vane and the casing wall, the position of the outlet port, and the discharge angle of the impeller vane. The effect of a narrow Radial Gap on hemolysis was consistent with no evidence that the outlet port position or the vane discharge angle affected blood trauma in so far as the Nikkiso centrifugal blood pump was concerned. The Radial Gap should be considered as a design parameter of a centrifugal blood pump to reduce blood trauma.

  • computational fluid dynamics analysis to establish the design process of a centrifugal blood pump second report
    Artificial Organs, 1999
    Co-Authors: Yuki Miyazoe, Toru Masuzawa, Tomonori Tsukiya, Takashi Yamane, Balazs Asztalos, Yoshiaki Konishi, Kazuyuki Ito, Toshio Sawairi, Seiko Endo
    Abstract:

    To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the Radial Gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.

  • flow visualization study to improve hemocompatibility of a centrifugal blood pump
    Artificial Organs, 1999
    Co-Authors: M. Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki Konishi
    Abstract:

    A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing Gap widths on the flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small Radial Gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small Radial Gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small Radial Gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small Radial Gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small Radial Gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

  • development of design methods of a centrifugal blood pump with in vitro tests flow visualization and computational fluid dynamics results inhemolysis tests
    Artificial Organs, 1998
    Co-Authors: Koki Takiura, H. Takano, Toru Masuzawa, M. Nishida, Eisuke Tatsumi, Yoshiyuki Taenaka, Takashi Yamane, Seiko Endo, Yoshinari Wakisaka, Balazs Asztalos
    Abstract:

    There are few established engineering guidelines aimed at reducing hemolysis for the design of centrifugal blood pumps. In this study, a fluid dynamic approach was applied to investigate hemolysis in centrifugal pumps. Three different strategies were integrated to examine the relationship between hemolysis and flow patterns. Hemolytic performances were evaluated in in vitro tests and compared with the flow patterns analyzed by flow visualization and computational fluid dynamic (CFD). Then our group tried to establish engineering guidelines to reduce hemolysis in the development of centrifugal blood pumps. The commercially available Nikkiso centrifugal blood pump (HPM-15) was used as a standard, and the dimensions of 2 types of Gaps between the impeller and the casing, the axial and the Radial Gap, were varied. Four impellers with different vane outlet angles were also prepared and tested. Representative results of the hemolysis tests were as follows: The axial Gaps of 0.5, 1.0, and 1.5 mm resulted in normalized index of hemolysis (NIH) values of 0.0028, 0.0013 and 0.0008 g/100 L, respectively. The Radial Gaps of 0.5 and 1.5 mm resulted in NIH values of 0.0012 and 0.0008 g/100 L, respectively. The backward type vane and the standard one resulted in NIH values of 0.0013 and 0.0002 g/100 L, respectively. These results revealed that small Gaps led to more hemolysis and that the backward type vane caused more hemolysis. Therefore, the design parameters of centrifugal blood pumps could affect their hemolytic performances. In flow visualization tests, vortices around the impeller outer tip and tongue region were observed, and their patterns varied with the dimensions of the Gaps. CFD analysis also predicted high shear stress consistent with the results of the hemolysis tests. Further investigation of the regional flow patterns is needed to discuss the cause of the hemolysis in centrifugal blood pumps.

Balazs Asztalos - One of the best experts on this subject based on the ideXlab platform.

  • development of design methods for a centrifugal blood pump with a fluid dynamic approach results in hemolysis tests
    Artificial Organs, 1999
    Co-Authors: Toru Masuzawa, H. Takano, Eisuke Tatsumi, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe
    Abstract:

    : The purpose of this study was to examine the relationship between local flow conditions and the hemolysis level by integrating hemolysis tests, flow visualization, and computational fluid dynamics to establish practical design criteria for centrifugal blood pumps with lower levels of hemolysis. The Nikkiso centrifugal blood pump was used as a standard model, and pumps with different values of 3 geometrical parameters were tested. The studied parameters were the Radial Gap between the outer edge of the impeller vane and the casing wall, the position of the outlet port, and the discharge angle of the impeller vane. The effect of a narrow Radial Gap on hemolysis was consistent with no evidence that the outlet port position or the vane discharge angle affected blood trauma in so far as the Nikkiso centrifugal blood pump was concerned. The Radial Gap should be considered as a design parameter of a centrifugal blood pump to reduce blood trauma.

  • computational fluid dynamics analysis to establish the design process of a centrifugal blood pump second report
    Artificial Organs, 1999
    Co-Authors: Yuki Miyazoe, Toru Masuzawa, Tomonori Tsukiya, Takashi Yamane, Balazs Asztalos, Yoshiaki Konishi, Kazuyuki Ito, Toshio Sawairi, Seiko Endo
    Abstract:

    To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the Radial Gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.

  • flow visualization study to improve hemocompatibility of a centrifugal blood pump
    Artificial Organs, 1999
    Co-Authors: M. Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki Konishi
    Abstract:

    A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing Gap widths on the flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small Radial Gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small Radial Gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small Radial Gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small Radial Gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small Radial Gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

  • development of design methods of a centrifugal blood pump with in vitro tests flow visualization and computational fluid dynamics results inhemolysis tests
    Artificial Organs, 1998
    Co-Authors: Koki Takiura, H. Takano, Toru Masuzawa, M. Nishida, Eisuke Tatsumi, Yoshiyuki Taenaka, Takashi Yamane, Seiko Endo, Yoshinari Wakisaka, Balazs Asztalos
    Abstract:

    There are few established engineering guidelines aimed at reducing hemolysis for the design of centrifugal blood pumps. In this study, a fluid dynamic approach was applied to investigate hemolysis in centrifugal pumps. Three different strategies were integrated to examine the relationship between hemolysis and flow patterns. Hemolytic performances were evaluated in in vitro tests and compared with the flow patterns analyzed by flow visualization and computational fluid dynamic (CFD). Then our group tried to establish engineering guidelines to reduce hemolysis in the development of centrifugal blood pumps. The commercially available Nikkiso centrifugal blood pump (HPM-15) was used as a standard, and the dimensions of 2 types of Gaps between the impeller and the casing, the axial and the Radial Gap, were varied. Four impellers with different vane outlet angles were also prepared and tested. Representative results of the hemolysis tests were as follows: The axial Gaps of 0.5, 1.0, and 1.5 mm resulted in normalized index of hemolysis (NIH) values of 0.0028, 0.0013 and 0.0008 g/100 L, respectively. The Radial Gaps of 0.5 and 1.5 mm resulted in NIH values of 0.0012 and 0.0008 g/100 L, respectively. The backward type vane and the standard one resulted in NIH values of 0.0013 and 0.0002 g/100 L, respectively. These results revealed that small Gaps led to more hemolysis and that the backward type vane caused more hemolysis. Therefore, the design parameters of centrifugal blood pumps could affect their hemolytic performances. In flow visualization tests, vortices around the impeller outer tip and tongue region were observed, and their patterns varied with the dimensions of the Gaps. CFD analysis also predicted high shear stress consistent with the results of the hemolysis tests. Further investigation of the regional flow patterns is needed to discuss the cause of the hemolysis in centrifugal blood pumps.

Takashi Yamane - One of the best experts on this subject based on the ideXlab platform.

  • development of design methods for a centrifugal blood pump with a fluid dynamic approach results in hemolysis tests
    Artificial Organs, 1999
    Co-Authors: Toru Masuzawa, H. Takano, Eisuke Tatsumi, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe
    Abstract:

    : The purpose of this study was to examine the relationship between local flow conditions and the hemolysis level by integrating hemolysis tests, flow visualization, and computational fluid dynamics to establish practical design criteria for centrifugal blood pumps with lower levels of hemolysis. The Nikkiso centrifugal blood pump was used as a standard model, and pumps with different values of 3 geometrical parameters were tested. The studied parameters were the Radial Gap between the outer edge of the impeller vane and the casing wall, the position of the outlet port, and the discharge angle of the impeller vane. The effect of a narrow Radial Gap on hemolysis was consistent with no evidence that the outlet port position or the vane discharge angle affected blood trauma in so far as the Nikkiso centrifugal blood pump was concerned. The Radial Gap should be considered as a design parameter of a centrifugal blood pump to reduce blood trauma.

  • computational fluid dynamics analysis to establish the design process of a centrifugal blood pump second report
    Artificial Organs, 1999
    Co-Authors: Yuki Miyazoe, Toru Masuzawa, Tomonori Tsukiya, Takashi Yamane, Balazs Asztalos, Yoshiaki Konishi, Kazuyuki Ito, Toshio Sawairi, Seiko Endo
    Abstract:

    To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the Radial Gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.

  • flow visualization study to improve hemocompatibility of a centrifugal blood pump
    Artificial Organs, 1999
    Co-Authors: M. Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki Konishi
    Abstract:

    A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing Gap widths on the flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small Radial Gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small Radial Gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small Radial Gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small Radial Gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small Radial Gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

  • development of design methods of a centrifugal blood pump with in vitro tests flow visualization and computational fluid dynamics results inhemolysis tests
    Artificial Organs, 1998
    Co-Authors: Koki Takiura, H. Takano, Toru Masuzawa, M. Nishida, Eisuke Tatsumi, Yoshiyuki Taenaka, Takashi Yamane, Seiko Endo, Yoshinari Wakisaka, Balazs Asztalos
    Abstract:

    There are few established engineering guidelines aimed at reducing hemolysis for the design of centrifugal blood pumps. In this study, a fluid dynamic approach was applied to investigate hemolysis in centrifugal pumps. Three different strategies were integrated to examine the relationship between hemolysis and flow patterns. Hemolytic performances were evaluated in in vitro tests and compared with the flow patterns analyzed by flow visualization and computational fluid dynamic (CFD). Then our group tried to establish engineering guidelines to reduce hemolysis in the development of centrifugal blood pumps. The commercially available Nikkiso centrifugal blood pump (HPM-15) was used as a standard, and the dimensions of 2 types of Gaps between the impeller and the casing, the axial and the Radial Gap, were varied. Four impellers with different vane outlet angles were also prepared and tested. Representative results of the hemolysis tests were as follows: The axial Gaps of 0.5, 1.0, and 1.5 mm resulted in normalized index of hemolysis (NIH) values of 0.0028, 0.0013 and 0.0008 g/100 L, respectively. The Radial Gaps of 0.5 and 1.5 mm resulted in NIH values of 0.0012 and 0.0008 g/100 L, respectively. The backward type vane and the standard one resulted in NIH values of 0.0013 and 0.0002 g/100 L, respectively. These results revealed that small Gaps led to more hemolysis and that the backward type vane caused more hemolysis. Therefore, the design parameters of centrifugal blood pumps could affect their hemolytic performances. In flow visualization tests, vortices around the impeller outer tip and tongue region were observed, and their patterns varied with the dimensions of the Gaps. CFD analysis also predicted high shear stress consistent with the results of the hemolysis tests. Further investigation of the regional flow patterns is needed to discuss the cause of the hemolysis in centrifugal blood pumps.

  • computational fluid dynamic analyses to establish design process of centrifugal blood pumps
    Artificial Organs, 1998
    Co-Authors: Yuki Miyazoe, Toru Masuzawa, Takashi Yamane, Yoshiaki Konishi, Kazuyuki Ito, Toshio Sawairi, Koki Takiura, Masahiro Nishida, Yoshiyuki Taenaka
    Abstract:

    To establish quantitative, efficient design theories for centrifugal blood pumps, computational fluid dynamics (CFD) analyses were compared to the results of flow visualization tests and hemolysis tests, mainly on the Nikkiso centrifugal blood pump. The results turned out to coincide in the velocity vector plots. CFD analysis revealed that the smaller the Gap is, the greater the shear stress becomes. This tendency becomes even greater with a Radial Gap change. Hemolysis study also indicated that the smaller the Gap is, the greater the hemolysis. CFD analysis in comparison with hemolysis tests could be a useful index for developing blood pumps in the future.