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doctoral, 創造科学技術大学院, 乙第160号

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1530050000, レポート番号: JAXA-RM-15-010

資料番号: PA1610061000

人は誰しも「邪念」, 「欲望」そして「無知」と「うっかり」により, ｢ヒューマンエラー｣を引き起こす危険因子を内に孕んでいる．これまで約35 年に渡りLE-5/LE-7, ターボポンプの開発に携わり, その中で自身が見聞きした「判断ミス」について事例を挙げて検証する．ここに示す「ヒューマンエラー」は遠い他人事ではなく, 誰でもいつでも当事者になりえるものであり, 決断を迫られたときにミスに導かないよう他山の石としていただければ幸いである．, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0065219000, レポート番号: JAXA-RM-11-022

We are developing a novel, general purpose isotropic-3D PET detector X'tal cube which has high spatial resolution in all three dimensions. The research challenge for this detector is implementing effective detection of scintillation photons by covering six faces of a segmented crystal block with silicon photomultipliers (SiPMs). In this paper, we developed the second prototype of the X'tal cube for a proof-of-concept. We aimed at realizing an ultimate detector with 1.0 mm^3^ cubic crystals, in contrast to our previous development using 3.0 mm^3^ cubic crystals. The crystal block was composed of a 16 x 16 x 16 array of lutetium gadolinium oxyorthosilicate (LGSO) crystals 0.993 x 0.993 x 0.993 mm^3^ in size. The crystals were optically glued together without inserting any reflector inside and 96 multi-pixel photon counters (MPPCs, S10931-50P, i.e. six faces each with a 4 x 4 array of MPPCs), each having a sensitive area of 3.0 x 3.0 mm^2^, were optically coupled to the surfaces of the crystal block. Almost all 4096 crystals were identified through Anger-type calculation due to the finely adjusted reflector sheets inserted between the crystal block and light guides. The reflector sheets, which formed a belt of 0.5 mm width, were placed to cover half of the crystals of the second rows from the edges in order to improve identification performance of the crystals near the edges. Energy resolution of 12.7% was obtained at 511 keV with almost uniform light output for all crystal segments thanks to the effective detection of the scintillation photons.

世界で二例目となる極低温キャビテーションの直接可視化に成功したことで，水キャビテーションとはキャビティの形態が全く異なることが明らかとなった。これまで理論的に進められてきた極低温流体の熱力学的効果は，「直接見る」ことによりキャビティの抑制が吸込性能を向上させていることが検証された。また低流量域を高速度撮影による可視化を行った結果，キャビティの量的な変化をもたらす変性領域が存在することが確認された。, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0064964000, レポート番号: JAXA-RM-11-001

本報告では，「極低温流体中でインデューサに発生するキャビテーションの直接可視化(その1：耐低温樹脂の特性検証試験結果)」で行った要素試験のデータを基に，更に極低温透視管に改良を加え，目標耐圧圧力7MPaを目指した検証試験について述べる。(その1)でネジ強度に課題のあったポリカーボネートは，ネジ山形の設計変更を行い，シールは新たにスプリング荷重式テフロンシールを選定し，シール構造にも改良を加えることで目標とする耐圧7MPaを達成することができた。また，ポリカーボネート樹脂の懸念材料であった低温脆性の劣化についても，熱サイクル試験を行うことで素材の潜在能力の高さを確認できた。これらの経緯と試験結果について報告する。, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0064609000, レポート番号: JAXA-RM-09-009

本報告は，平成19年度の「先端・萌芽研究」の一環として行った，極低温インデューサに発生するキャビテーションの可視化装置の設計・試作に必要なデータ取得のために行った要素試験の結果である。極低温流体のキャビテーションを直接可視化するためには，耐低温性，加工性，透明性に優れた素材の選択が不可欠である。透視管材料には，筆者らが見いだし，極低温可視化装置(-196度、0.97MPa 以下)に実績があったポリカーボネート樹脂を選定し，これまでに経験したことがない高圧極低温領域における強度，特性データを取得した。また，ポカーボネート樹脂の耐化学性および金属部のシール性の検証を行ったので，その結果を報告する。, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0064608000, レポート番号: JAXA-RM-09-008

Hamamatsu SHR74000 is a newly designed full three-dimensional (3D) whole body positron emission tomography (PET) scanner with small crystal size and large field of view (FOV). With the improvement of sensitivity, the scatter events increase significantly at the same time, especially for large objects. Monte Carlo simulations help us to understand the scatter phenomena and provide good references for scatter correction. In this paper, we introduce an effective scatter correction method based on single scatter simulation for the new PET scanner, which accounts for the full 3D scatter correction. With the results from Monte Carlo simulations, we implement a new scale method with special concentration on scatter events from outside the axial FOV and multiple scatter events. The effects of scatter correction are investigated and evaluated by phantom experiments; the results show good improvements in quantitative accuracy and contrast of the images, even for large objects.

資料番号: PA0810094000

資料番号: ARDS06307000

The component of shaft vibration, which rotates 2.5 times faster than shaft rotation, was observed during a Lox turbopump test. From the spectrum analyses of dynamic pressure around the inducer, the shaft vibration was assumed to be caused by the clouds of cavitation in backflow vortices. In this study, some visual observations around inducer were conducted and discussed about relationship of the shaft vibration and the clouds of cavitation in backflow vortices., 資料番号: AA0049500015, レポート番号: JAXA-SP-06-006

The effects of the inlet casing configurations on unsteady cavitation were examined with a 3-bladed inducer. The inlet flow and cavitation pattern in two different casings were visualized using PIV (Particle Image Velocimetry) and high-speed video. It was found that the rotating cavitation would be suppressed when the tip clearance at the inducer inlet was increased. The vortex cavitation in tip leakage flow and cavitation in back flow is considered to affect the appearance of the rotating cavitation by the inlet casing configuration., 資料番号: AA0049056007, レポート番号: JAXA-SP-05-010

PET scanner are an important component in functional brain imaging devices. Several PET scanners have been developed during the last two decades for brain research studies. We are developing a high-performance brain PET scanner, jPET-D4.This scanner is designed to achieve not only high spatial resolution but also high sensitivity using four-layered depth-of-interaction (DOI) detectors. The scanner has five block detector rings with the ring diameter of 390 mm and each blockdetector ring consists of 24 DOI detectors. In previous work, we have demonstrated that 3 mm FWHM uniform spatial resolution within the field-of-view could be realized. In this paper, we describe the jPET-D4 system and evaluate its performance. The average energy resolution for 120 DOI detectors is optimized to 16 % +/- 1.0 %. The scater fraction for this system is 40 % with an energy window of 400-600 keV. The sensitivity for the point source is 102 kcps/MBq (10.2 %) with a 400 keV LLD. Maximum noise equivalent count rate (NECR) is 154 kcps at 11 kBq/ml with a 10 ns coinsidence time window. We evaluated scatter fraction and NECR following procedures based on NEMA NU-2-1994. These first evalution measurements indicate the jPET-D4 has good performance.

資料番号: ARDS05144000, レポート番号: A120

第49回宇宙科学技術連合講演会(平成17年11月9-11日, アステールプラザ), 広島市, 資料番号: ARDS05181000, レポート番号: 1G02

LOX Turbo Pump (OTP) is equipped with H-2A 1st stage engine (LE-7A) and it has already been made sure that it satisfies all the demand for flight. But it is also understood that supersynchronous shaft vibrations, with a frequency of about 1.0 to 1.2 times of the OTP shaft rotational speed are increased under the flight condition, those are caused by rotating cavitation in the inducer. In order to improve the reliance and to suppress the rotating cavitation, the cavitation tests were performed using improved inducer liner. Tests were conducted using water as working fluid. As a result, the improved inducer liner was very effective to suppress the rotating cavitation., 資料番号: AA0033392040

日本のLE-7(液体ロケットエンジン)エンジン用液酸ターボポンプの開発時に液体酸素ターボポンプの回転非同期振動と旋回キャビテーションとの間に密接な関係があることが見いだされた。この旋回キャビテーションに伴う回転非同期振動はインデューサライナの設計変更により抑制が可能となった。これに伴って旋回キャビテーションの理論的な取り扱いも可能となった。また、各国の高性能ロケット用ターボポンプにおいても旋回キャビテーション現象が報告され、旋回キャビテーションはロケット用ターボポンプのインデューサに共通の問題であることが明らかとなった。この旋回キャビテーションに関してキャビテーションタンネルを用いた試験を実施してきた中で、理論的に存在が指摘されていた羽根車の回転の逆回りモードと考えられる旋回キャビテーションによる振動が観察された。この現象は高速度カメラの画像解析および軸振動などの解析により、逆回りモードであることが確認された。本研究は、この逆回りモードの旋回キャビテーションの発生の確認およびその挙動について述べるものである。, During the development of a liquid oxygen turbopump for the LE (Liquid rocket Engine)-7 engine of the H-2 rocket, super synchronous vibrations (1.0-1.3 omega) in the inducer were frequently observed. From research on the vibration performance of the inducer, it was concluded that shaft vibrations of this type were caused by rotating cavitation in the inducer, and it was also demonstrated that a moderately increased diameter of the pump inlet was most effective in suppressing these shaft vibrations. In the light of previous theoretical analysis, it was predicted that rotating cavitation had two unstable modes, a forward rotating cavitation and a backward rotating cavitation, which had not hitherto been observed in experiments. In the suction performance test of the inducer using the cavitation tunnel, a shaft vibration of higher frequency than the forward rotating cavitation was observed. From a study using a high-speed photograph analyzer and the spectrum analysis of the shaft vibration, it was concluded that the vibration was caused by the backward rotating cavitation. This paper provides details on the occurrence of backward rotating cavitation in the inducer and its performance., 資料番号: AA0001973000, レポート番号: NAL TR-1382

LE-7(液体ロケットエンジン-7)用液酸ターボポンプの開発過程において問題となった、インデューサに発生する旋回キャビテーションは、ケーシング形状を変更することで解決できた。しかし、その発生過程を可視化などにおいて明らかにすることは実機ターボポンプでは困難であった。そこで、ターボポンプ試験において旋回キャビテーションの抑制を試みた代表的な3種類のケーシングを、航技研のキャビテーションタンネルを使用して可視観察を行い、ケーシング形状がキャビテーションに与える影響について調べた。実機ターボポンプにおいて問題となった従来型ケーシングではやはり広い流量範囲で旋回キャビテーションが生じ振動レベルも大きく、さらに低周波の振動も発生することが判明した。ストレート型ならびに改良型ケーシングは抑制効果が見られ、さらに改良型ケーシングは振動の軽減や低周波振動にも効果があることが確認された。これらの観察の結果、実機ターボポンプにおいて採用された改良型ケーシングの有効性が明らかになった。, Some observations of rotating cavitation in a rocket turbopump inducer were made with three types of casing: a modified, an original and a straight casing. Rotating cavitation was observed with the original casing at the design flow rate, but was not observed with the modified or the straight one. The region of occurrence of rotating cavitation with the modified or the straight casing seemed to be shifted to a higher flow rate range, which might be caused by the backflow at the inducer inlet. It is also reported that the low cycle oscillation that occurred after attached cavitation is related to rotating cavitation and attached cavitation., 資料番号: AA0001076000, レポート番号: NAL TR-1325

Objective: The X'tal cube is our new PET detector, which is being developed to achieve isotropic 3D positioning detectability. The X'tal cube is based on a segmented 3D crystal block for which all surfaces are covered with photo-detectors. We have shown that the X'tal cube can achieve isotropic intrinsic resolution with the Anger-type calculation even at the block edges. In this work, we developed a new one pair prototype system to simulate a ring-type scanner, and evaluated imaging performance of the X'tal cube detector. Methods: The developed system consisted of two X'tal cube detectors, two rotating stages, and a 192-channel data acquisition system. The X'tal cube consisted of the LYSO cubic crystal block of (18 mm)3 in which the 3D grids of 2 mm pitch were fabricated by the internal laser processing. 4 x 4 arrays of multi pixel photon counters (MPPCs) were optically coupled to each surface of the crystal block. The detector positions were automatically controlled to simulate a ring-type PET of 14.6 cm in diameter. Data were collected for assumed all detector positions and then a sinogram was obtained. The data were reconstructed using the filtered backprojection. Results: We successfully obtained uniform spatial resolution less than 2 mm over the FOV. Conclusion: We developed one pair prototype system for the X'tal cube detector, and we confirmed its potential for high-resolution imaging, SNM2012 Annual Meeting

Thermodynamic effects on cavitation occurred in a nozzle flow were experimentally investigated with liquid nitrogen. The aspect visualization of cavitating flows shows that the quantity of cavity bubbles increased gradually with the decrease of cavitation number but the size of cavity bubbles did not so change then. And, the temperature measurement of cavitating flows shows that the temperature depression in the cavitating point increased with the decrease of cavitation number. It can be cleared that the temperature of the cavitating point decreases and decreases due to the evaporative latent heat of the increasing cavity bubbles. Furthermore, the size distribution obtained by image analysis on the visualized images shows that cavity bubbles did not grow up easily in the contracted section of the nozzle when the cavitation number is small. However, it also shows that the cavity bubbles did not shrink easily in the diverging section then. These features can be considered because the thermodynamic effects become strong due to the dramatic growth of bubbles at the beginning of cavitation., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0064963000, レポート番号: JAXA-RM-10-018

Cavitation in cryogenic fluids, e.g., propellants of rocket engines, has a thermodynamic effect because of thermal imbalance around the cavity. The thermodynamic effect on cavitation is beneficial in that it improves cavitation performances due to the delay of cavity growth. In the present work, two experiments were conducted on a three-bladed cavitating inducer in which liquid nitrogen and cold water as working flow were used in order to confirm the thermal effects. Aspects of the cavitation in the inducer were observed by direct optical visualization both in liquid nitrogen and water. The bubbles of the tip vortex cavitation were very fine, and the thickness of the cavitation on the blade surface was very thin in liquid nitrogen compared with those in cold water. The growth of the cavity length along the blade was much suppressed as decrease the cavitation numbers in liquid nitrogen., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0064645000, レポート番号: JAXA-RM-09-010

To clarify the thermodynamic effects on cavitation in cryogenic propellants, new Cryogenic Cavitation Tunnel (CCT) was constructed in the Cryogenic Inducer Test Facility at the Kakuda Space Center of JAXA. Liquid nitrogen is used as the working fluid for experiments of the thermodynamic effects on cavitation. The performance of the tunnel was confirmed to be well-satisfied from the verification test by using a cavitating orifice. In this article, the results of the verification test and the future program are presented., 形態: カラー図版あり, 資料番号: AA0064234000, レポート番号: JAXA-RM-08-008

Turbopump inducer, which is actually a high-precision, high-speed, sophisticated rotating impeller, is one of the key components of a liquid propellant rocket engine. On the other hand, the thermodynamic effect on cavitation is a favorable phenomenon in cryogenic fluids. It suppresses the growth of cavity since thermal imbalance appears around the cavity due to heat transfer for evaporation. Therefore, cavitation performance in cryogenic fluids is improved. In this article, some highlights about the thermodynamic effects on cavitating inducer carried out during the years 2004-2006 through the Cryogenic Inducer Test Facility in JAXA are presented., 形態: カラー図版あり, 著者人数: 14人, 資料番号: AA0064231000, レポート番号: JAXA-RM-08-005

高速回転／高流量のロケット用インデューサでは、旋回キャビテーションによる過大な軸振動が問題となった。このキャビテーションによる不安定現象を解明するために、キャビテーションタンネル試験設備において実機インデューサケーシング形状を模擬した透明ケーシングと高速度カメラを用いて、インデューサに発生するキャビテーションの可視化観察を行った。この可視化において、従来から知られている定常非対称キャビテーション(回転同期)よりもキャビテーション係数が高い領域に発生する前回りモード(回転速度の1.1〜1.3倍程度で旋回する)の旋回キャビテーション(回転非同期)のほか、逆回りモードの旋回キャビテーションや低周波モード、さらにキャビテーション係数の低い領域においても前回りモードの旋回キャビテーションが観察された。, Different forms of oscillating cavitation (rotating cavitation, attached cavitation and low cycle oscillations) were very common and posed serious problem for liquid rocket engine turbopumps. In this study, visual observations of these phenomena were made using a high speed camera. The following results were obtained; (a) Backward traveling rotating cavitation was identified experimentally for the first time. (b) The low cycle oscillations have a relationship with rotating cavitation. (c) A forward traveling rotating cavitation dissimilar to conventional rotating cavitation was found at lower cavitation number., 資料番号: AA0063532000, レポート番号: JAXA-RR-06-035