マリンエンジニアリング
Online ISSN : 1884-3778
Print ISSN : 1346-1427
ISSN-L : 1346-1427
56 巻, 3 号
選択された号の論文の31件中1~31を表示しています
特集「船舶におけるGHG排出削減・冷媒規制の動向」
序文
報告
解説
論文
  • 井上 順広, 劉 宇飛, 渡邊 和英, 地下 大輔
    2021 年 56 巻 3 号 p. 355-366
    発行日: 2021/05/01
    公開日: 2021/06/02
    ジャーナル フリー

      Research is currently in progress on developing and improving efficiency of high-temperature heat pumps and organic Rankine cycle power systems, both of which generate high-temperature steam by effectively utilizing low-quality heat sources from ship engines and factories for industrial purposes. From an environmental point of view, development efforts are also underway to replace low-pressure working fluids used in these systems with new alternative working fluids with low global warming potentials (GWPs). The purpose of this study is to experimentally clarify the evaporation and condensation flow characteristics of alternative low-GWP working fluids inside two types of horizontal microfin tubes with outer diameters of 9.5 mm. The Hydrofluoroolefin (HFO) working fluids R1336mzz(E) and R1336mzz(Z), both of which are expected to replace the working fluid R245fa that is used widely at present, two pure components and their mixture were used as test fluids in this study. In this experiment, the authors measured the evaporation and condensation heat transfer coefficients and pressure drop under the conditions of 50-300 kg/(m2s) mass velocity, a saturated evaporation temperature of 40 °C and a saturated condensation temperature of 60 °C. The results of the experiment clarified the effects of mass velocity and fin geometries on the evaporation and condensation heat transfer and pressure drop characteristics of R1336mzz(E), R1336mzz(Z) and their mixture working fluid. In addition, comparisons were made between the evaporation and condensation heat transfer coefficients and pressure drop of these working fluids and those of R245fa to highlight differences in their performance. Furthermore, the measured values were correlated with previous correlations for evaporation and condensation heat transfer for microfin tubes to verify the applicability of these predicted correlations.

技術資料
  • 劉 秋生, 柴原 誠, 中村 雄史, 笹井 勇佑
    2021 年 56 巻 3 号 p. 367-372
    発行日: 2021/05/01
    公開日: 2021/06/02
    ジャーナル フリー

    In this study, we focused on the convective heat transfer for water flowing in a small diameter tube. Quasi-steady state and transient heat transfers were measured in vertical small tube with exponentially increasing heat inputs.The heat generation rate was raised through an exponential function. The flow velocities,the inlet liquid temperatures and the inlet pressure were ranging from 2.3 to 24.1 m/s, 285 to 350 K, and 180 to 1262 kPa.The effects of various parameters such as flow velocity, inner diameter of the tube, and e-folding time of heat generation rate were investigated, and the relations between convective heat transfer and these parameters were clarified. It was obtained that the heat transfer coefficient increased with the decreasing of inner diameter of tube.The heat transfer coefficient also increased with decreasing of the e-folding time of the heat generation rate when the e-folding time is smaller than about 1 second. The heat transfer coefficient also increased with an increase in flow velocity.Moreover, the Nusselt number under the quasi-steady state was affected by the Reynolds number and the non-dimensional diameter of tube.

  • 大原 順一
    2021 年 56 巻 3 号 p. 373-378
    発行日: 2021/05/01
    公開日: 2021/06/02
    ジャーナル フリー

    In the present study, the characteristics of heat transfer are experimentally investigated on the falling film evaporation of alternative pure refrigerant HFO1233zd(E) in a plate-fin heat exchanger consisting of serrated-fins. The refrigerant liquid is supplied to the channel through 37 holes of a distributor. The liquid flowing down vertically is heated electrically from the rear wall of the channel and evaporated. The experimental parameters are set as follows: the mass velocities are varied 7.4~55.1 kg/(m2s), the heat fluxes are varied 8.7~50 kW/m2 and the pressures are about 100~150 kPa. In the case of small mass velocity being smaller than 20 kg/(m2s), the heat transfer coefficient decreases monotonously and gradually in accordance with an increase in vapor quality, taking value of 6~1kW/m2K. It is thought that the value of heat transfer coefficient decreases due to dry patch and the spread of a dry part in the downstream region. In the case of mass velocity being larger than 41 kg/(m2s), the values of heat transfer coefficient vary 8~22 kW/m2K in the region with the vapor quality 0~0.3. In the following region, the values are distributed around 10 kW/m2K. The relations between vapor quality and fin efficiency are investigated to examine the effectiveness of fins brazed to the base plate.

特集「Global Sulphur Cap 2020(SOx 0.5%規制)への対応とEGCSの最新動向」
序文
解説
技術資料
  • 稲葉 祥梧, 篠野 雅彦, 須藤 拓, 浦 環
    2021 年 56 巻 3 号 p. 449-456
    発行日: 2021/05/01
    公開日: 2021/06/02
    ジャーナル フリー

      A major advantage of Autonomous Underwater Vehicles (AUVs) is that it is possible to operate a greater number of them simultaneously thanks to their autonomous and cable-less characteristics. However, the more AUVs are operating at the same time, the more difficult it becomes to control them. One of the solutions to this problem is to use an Autonomous Surface Vehicle (ASV) and this allows the mother ship to focus on ASV operations and emergency response.

      In 2017, National Maritime Research Institute (NMRI) developed an ASV for AUV control and operated it with multiple AUVs for a seafloor resources survey. In this operation, the ASV collected data on the AUV's status and transmitted it in radio communication, making it possible the mother ship to focus on launch and recovery operations. In this paper, we introduce the results of the ASV operation to control the AUVs along with the development and sea trials of the ASV.

論文
  • 川内 智詞, 高木 正英
    2021 年 56 巻 3 号 p. 457-464
    発行日: 2021/05/01
    公開日: 2021/06/02
    ジャーナル フリー

    The aim of this paper is to investigate the relationship between fuel/air mixture formation and ignition processes of a two component fuel spray using a one-dimensional diesel spray model. The model, which was originally proposed by Musculus and Kattke, was modified in order to allow evaporation process of a transient diesel spray to be taken into account. The calculation model was validated against pressure history data measured in a combustion experiment and showed good agreement with decreased pressure in the combustion chamber which represents heat absorption process of the spray. This model was applied to predictions of mixture formation process of two-component fuels which are composed of Hexadecane(C16H34) and 1-methyl-naphthalene(C11H10). Based on the calculation results, reasons why cetane number and fuel injection duration influence the ignition delay were closely discussed.

  • 今井 康雄, 高木 正英, 川内 智詞
    2021 年 56 巻 3 号 p. 465-472
    発行日: 2021/05/01
    公開日: 2021/06/02
    ジャーナル フリー

      The IMO sulphur limit for ships' fuel oils has just started since 2020. In order to reduce sulphur concentration, it is predicted that LCO (Light Cycle Oil) fuels will be more commonly used as low sulphur base materials. However, aromatics in LCO fuel affect not only self-ignition but also combustion characteristics, especially soot emission. Therefore, it is important to evaluate combustion characteristics of aromatics in a simplified manner.

      In this study, the authors measured temporal and spatial C2 and OH radical luminous distributions, which contribute to soot formation and oxidation process respectively, to evaluate combustion and soot emission characteristics of aromatic contents. Then the authors proposed a new method for soot estimation using luminous intensity and time of C2 and OH radicals. The results of the study showed that the soot estimation mostly corresponded to soot emission experimental data.

  • 三原 悠, 浅野 一朗, 段 智久, 岡村 秀雄, 松村 千里, 羽賀 雄紀, 中坪 良平
    2021 年 56 巻 3 号 p. 473-483
    発行日: 2021/05/01
    公開日: 2021/06/02
    ジャーナル フリー

      As a way to improve the combustion characteristics of wood tar which is highly viscous and flame retardant, the authors blended it with liquefied dimethyl ether (DME), which can improve fuel fluidity, ignitability and spray atomization. Moreover, heavy fuel oil (bunker-c oil) was added to increase the heating value of this fuel sample. The sample, which has the blending ratio of 35 % wood tar, 30% DME and 35% bunker-c by weight, was used in a combustion test with a three-cylinder in-direct injection diesel engine. Additionally, the authors also investigated particulate matter (PM) produced after burning four samples that mixed liquefied DME with flame retardant fuels in the same engine to analyze its environmental and biological impacts. The four samples prepared for the experiment were (1) 70% distillate oil (bunker-a) and 30% DME; (2) 85% bunker-c and 15% DME; (3) 70% bunker-c and 30% DME; (4) 35 % bunker-c, 30% DME and 35% wood tar.

      The results of the engine test suggested the possibility that wood tar could become more combustible by optimizing the flow rate of fuel and the blend ratio of liquefied DME and bunker-c. In the (4) case, PM showed no high mutagenic potentials and there were lower concentrations of such inorganic substances as vanadium and nickel. Polycyclic aromatic hydrocarbons (PAHs) concentrations in PM decreased by blending liquefied DME with bunker-c, whereas did not decrease for the wood tar.

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