A Breakthrough in Waterjet Propulsion Systems

喷水推进泵选型设计时工作参数和几何参数计算聂建栋;朱朝峰【摘要】作为推进装置中的一个主要部件,喷水推进泵在选型设计上与传统的泵差别很大,其工作参数的确定必须建立在推进系统分析的基础上,由设计航速下系统的最高喷射效率决定最佳喷速比,由额定转速和驼峰阻力处航速对应的工况点的抗空化性能来设定泵设计转速,并且要满足主机功率的要求.在已知设计航速和船体阻力曲线的条件下,引入8个假定参数后,计算得到了泵的5个工作参数值;由比转速和吸口比转速建立工作参数和几何参数之间的联系,进而求得转子进、出口直径和喷口直径等主要设计参数.【期刊名称】《船电技术》【年(卷),期】2015(035)003【总页数】7页(P59-65)【关键词】船舶;喷水推进泵;选型设计;工作参数;几何参数【作者】聂建栋;朱朝峰【作者单位】海军驻武汉四三八厂军事代表室,武汉430061;海军驻武汉四三八厂军事代表室,武汉430061【正文语种】中文【中图分类】TQ040 前言当泵用作船舶推进器时，它应当满足水动力推进器的一般要求：保证船舶推进的设计航速；推进装置总的推进效率尽可能高；巡航航速到设计航速区间推进器效率较高且变化平缓。

与陆用水泵相比，喷水推进泵的效率和抗空化性能要求更严。

并且，为了产生尽可能大的推力，泵流量相对较大，尺寸和重量也限制较严，从而使得推进泵比转速较高、功率密度较大。

与该要求相适应的现代船用喷水推进泵主要为单级混流泵或者是比转速更高的轴流泵。

喷水推进泵作为喷水推进装置中的主要部件，其运转参数必须匹配推进装置的运转参数，进而由运转参数所决定的泵的主要设计参数也要兼顾推进装置的结构和布置要求。

本文针对喷水推进泵在设计使用时上述考虑因素，选取计算初始设计阶段泵的运转参数和主要设计参数，为船用喷水推进泵的自主设计迭代程序开发奠定基础。

1 喷水推进泵运转参数确定常见艉板式喷水推进器如图1所示，由进水流道、喷水推进泵、喷口和操舵倒航机构四部分组成。

II. Grammar and VocabularySection ADirections: After reading the passage below, fill in the blanks to make the passages coherent and grammatically correct. For the blanks with a given word, fill in each blank with the proper form of the given word; for the other blanks, use one word that best fits each blank.A Chinese civilian unmanned airship un-intendedly entered US airspace last week due to force majeure and was shot down by the US military on Saturday. For days, US politicians and media have hyped up this incident, claiming it was a spy in the sky. Is this a part of China's surveillance program or an accidental incident overplayed by US politicians and media to smear China?Last Friday, China confirmed that the airship was from China, noting that it was an unitended entry caused by force majeure. According to a Chinese foreign ministry spokesperson, the balloon was a civilian airship used mainly for meteorological research that went off __21__ planned course due to winds and had limited self-steering capability. __22__ the US spotted the airship, the Chinese side informed the US side of the civilian nature of the airship and conveyed that its entry into the US was unexpected. China has actively communicated with the US and worked with the US to properly handle this unexpected situation in a calm, professional, and __23__ (restrain) manner.It is not the first time in the world that balloons for scientific research __24__ (go) out of control. In 1998, a Canadian weather balloon - __25__ (conduct) scientific research for the Canadian Space Agency, Environment Canada, and the University of Denver in the US - went rogue due to a technical malfunction. The balloon failed to come down as planned and drifted across Canada toward the Atlantic Ocean. The balloons drifted in the sky for nine days, __26__ (enter) many countries' airspace, and finally landed on Finland's Mariehamn Island. The current Chinese balloon is a similar style to the Canadian balloon.According to __27__ US official, the balloon's payload - the part under the balloon - is the size of two or three school buses. If the balloon is __28__ the US claimed as "part of an espionage program," it didn't make sense for China to choose such a giant balloon visible to civilians with the naked eye __29__ the US side would easily detect. Also, the US senior defense official acknowledged that the balloon "never posed a military or physical threat to the American people."It is not the first time the US side has made groundless accusations __30__ China of spying. However, the US never provided any substantial evidence to prove their suspicion. As a responsible country, China strictly adheres to international law and respects other countries' sovereignty and territorial integrity.Section BDirections: Fill in each blank with a proper word chosen from the box. Each word can only be used once. Note that there is one word more than you need."Few articles change owners more frequently than clothes. They travel downwards from grade to grade in the social scale with remarkable regularity," wrote the journalist Adolphe Smith in 1877 as he traced a garment's journey.That model is almost __31__ in the era of fast fashion. The average British customer buys four items a month, often at pocket-money prices; though the low cost is a godsend for the hard-up, many purchases are discarded after a few outings, or never worn at all. Clothes Aid reports that 350,000 tonnes of used but still wearable clothing goes to landfill in the UK each year.Yet a gradual revival of the secondhand trade has gathered pace in the last years. At fashion website Asos, vintage sales have risen by 92%. It was once worn out of __32__; then it became the quirky choice of Jarvis Cocker-style misfits and the label of "vintage" gave it cachet. Now it is simply a way of life. Busy families sell cast-off items on eBay, teenagers trade on Depop and fashionistas offer designer labels on V estiaire Collective. __33__, it has become big enough business that mainstream retailers want a slice of the action. Cos, owned by H&M, has launched a resale service on its website. Selfridges already has a vintage channel. Asda announced last week that it would sell secondhand clothing in 50 supermarkets, following a successful __34__ project.For some buyers and sellers, the __35__ to secondhand is born of pandemic-induced financial need. Others have become queasy at working conditions in factories, or the impact of their shopping habit on the planet. But the shift is only a partial solution. One concern is that mainstream brands may "__36__" - using relatively small volumes of secondhand goods to improve their image, rather than engaging more seriously with sustainability. Another worry is that good causes are losing out as people trade rather than __37__ unwanted clothes. The biggest concern may be that people keep buying because they know they can resell goods, still chasing the buzz of the next purchase but with a(n) __38__ conscience and healthier bank balance.A new Netflix series, Worn Stories, documents the emotional resonance that clothes can have, each item "a memoir in miniature", writes Emily Spivack, whose book gave rise to the show. A handbag from a grandmother; a scarf passed on by a father, garment that made people feel confident in their first job - almost everyone has at least one item they cherish. Perhaps we could cultivate such __39__. A love of style is not a bad or trivial thing. But a(n) __40__ relationship is better than a quick fling. Can we learn to appreciate our own old clothes as well as other people's? III. Reading ComprehensionsSection ADirections: For each blank in the following passage, there are four words or phrases marked A, B, C and D. Fill in each blank with the word or phrase that best fits the context.Sounds of Mars wind captured by Nasa's InSight landerThe sound of the wind on Mars has been captured for the first time by Nasa's InSight lander, which was __41__ to Mars and touched down on the red planet 10 days ago.The agency's Jet Propulsion Laboratory (JPL) __42__ a piece of processed audio of the alien wind on Friday evening. InSight collected the low-frequency rumblings during its first week of operations.The wind is __43__ to be blowing at between 10 and 15 mph. These are the first sounds from Mars that are __44__ by human ears, according to the researchers."Capturing this audio was an unplanned __45__," said Bruce Banerdt, the InSight principal investigator at Nasa's lab in California. "But one of the things our mission is __46__ to is measuring motion on Mars and naturally that includes motion caused by sound waves."Nasa presented the sounds at a news conference on Friday. Cornell University's Don Banfield told reporters they __47__ him of "sitting outside on a windy summer afternoon ... in some sense, this is what it would sound as if you were sitting on the InSight lander on Mars."Scientists involved in the project said the sound has a thought-provoking, quality. Thomas Pike of Imperial College London said the rumbling was "rather different to anything that we've experienced on Earth, and I think it just gives us another way of __48__ how far away we are getting these signals."The noise is of the wind blowing against InSight's solar panels and the resulting vibration of the entire spacecraft. The sounds were __49__ by an air pressure sensor inside the lander that is part of a weather station, as well as the seismometer（地震仪）on the deck of the spacecraft.The low frequencies are a result of Mars' very thin air __50__, which is almost entirely made up of carbon dioxide, and, even more so, the seismometer itself, which is meant to detect underground seismic waves that are well below the threshold of human hearing. The seismometer will be moved to the Martian surface in the coming weeks. Until then, the team plans to record more wind noise.The 1976 Viking landers on Mars __51__ spacecraft shaking caused by wind, but it would be a(n) __52__ to consider it sound, said Banerdt.InSight landed on Mars on 26 November. "We're all still on a high from the landing last week ... and here we are less than two weeks after landing, and we've already got some amazing new science," said Nasa's Lori Glaze, the acting director of __53__ science. "It's cool. It's fun."On the surface of Mars, InSight will draw on a suite of instruments to study the planet's internal structure. A seismometer deployed by a robot arm will act as a(n) __54__ to the ground and listen for tremors produced when subterranean rock faces slip past one another along geological fault-lines（断层线）. Scientists expect InSight to record anything from a dozen to 100 Marsquakes of magnitude 3.5 or greater over the lander's two-year mission. The seismometer is so __55__ that it can detect vibrations smaller than the width of an atom.41. A. transferred B. launched C. delivered D. orbited42. A. released B. generated C. advocated D. addressed43. A. realized B. established C. estimated D. identified44. A. distinguishable B. available C. detectable D. accessible45. A. incident B. implication C. trick D. treat46. A. deposited B. arranged C. supposed D. dedicated47. A. informed B. reminded C. deprived D. convinced48. A. figuring out B. dealing with C. thinking about D. working on49. A. screened B. recognized C. interfered D. recorded50. A. density B. concentration C. intensity D. quantity51. A. made up B. caught up C. took up D. picked up52. A. stretch B. illusion C. coincidence D. approach53. A. planetary B. geological C. gravitational D. physical54. A. aid B. ear C. arm D. tool55. A. delicate B. sensible C. accurate D. sensitiveSection BDirections: Read the following two passage. Each passage is followed by several questions or unfinished statements. For each of them there are four choices marked A, B, C and D. Choose the one that fits best according to the information given in the passage you have just read.(C)Alan Jamieson remembers seeing it for the first time: a small, black fiber floating in liquid. It resembled a hair, but when Jamieson examined it under a microscope, he realized that the fiber was clearly synthetic -- a piece of plastic. And worryingly, his student Lauren Brooks had pulled it from the gut of a small amphipod living in one of the deepest parts of the ocean.For the past decade, Jamieson, a marine biologist at Newcastle University, has been sending vehicles to the bottom of marine trenches（海沟）, which can be as deep as the Himalayas are tall. These landers have collected amphipods -- scavenger relatives of crabs and shrimp that thrive in the abyss. Jamieson originally wanted to know how these animals differ from one distant trench to another. But a few years ago, he decided to analyze their body for toxic, human-made pollutants, which have been banned for decades but which persist in nature for much longer.The team found much PCBs（多氯联苯）. Some amphipods were carrying levels 50 times higher than those seen in crabs from one of China's most polluted rivers. When the news broke, Jamieson received calls from journalists and concerned citizens. And in every discussion, one question kept coming up: What about plastics?The world produces an estimated 10 tons of plastic a second, and between 5 million and 14 million tons sweep into the oceans every year. Some of them washes up on beaches. About 5 trillion pieces currently float in surface waters, mostly in the form of tiny, easy-to-swallow fragments that ends up in the gut of albatrosses, sea turtles, plankton, fish, and whales. But those pieces also sink, snowing into the deep sea and upon the amphipods that live there."It's not a good result," Jamieson said. "I don't like doing this type of work." When he submitted his findings to a scientific journal, the researchers who reviewed the paper reasonably asked how he could tell that the fibers were actually plastic. "Our response was, 'Some of it'spurple!'" Jamieson says."There's bits of pink in there. This doesn't come from animals." To satisfy the critics, his team chemically analyzed a subset of the fibers and found that all of it was synthetic.Other scientists have also found plastic litter in the deep: just last year, one team documented a plastic bag at the bottom of the Mariana Trench. Until now, no one had shown that abyssal animals were actually eating those fragments, but it seems obvious that amphipods would. When a morsel（食物碎屑）hits the ocean floor, amphipods turn up in droves.Food is scarce in the deep, so amphipods eat pretty much anything, which makes them particularly vulnerable to plastics. And since they sit at the bottom of the ocean food webs, t heir appetite can upset entire ecosystems. "They're like bags of peanuts," Jamieson says, "Everything else eats amphipods -- shrimp, fish -- and they'll end up consuming plastics, too. And when the fish die, they get consumed by amphipods, and it goes round and round in circles.""I imagine pollution in the Mariana Trench is an abstract concept for most people, but for those of us living in the Mariana Islands this has consequences for what ends up on our dinner plates," says Angelo Villagomez, from the Mariana Islands who works for the Pew Bertarelli Ocean Legacy Project. "So what can we do? The International Union for the Conservation of Nature recommends we protect 30 percent of every marine habitat to address human impacts, but that will only help if we're also sustainably managing the remaining 70 percent, reducing carbon emissions, and limiting the pollution being dumped in the ocean in the first place."63. The underlined word "abyss" in the passage is closest in meaning to _________?A. bottomless holeB. high peakC. distant areaD. endless pain64. Which of the following is TRUE according to the passage?A. Amphipods begin to produce fibers due to marine pollution.B. Jamieson ended up knowing the difference between animals in different trenches.C. Jamieson has proved the fibers they found were generated by humans.D. Amphipods consume almost everything in oceans and often attack other creatures.65. By saying "their appetite can upset entire ecosystems", the author means _________?A. Amphipods consuming too much marine resources affect the balance of nature.B. Amphipods can produce chain effects since they are food resources of others.C. Amphipods have occupied a lot of ocean space because of their appetite.D. Amphipods' habitat should be protected so as to address human impacts.66. Which of the following can be the best title of passage?A. Amphipods threatened by plastic litterB. Marine pollution - a big problemC. The disturbed ecosystem in the seaD. Most troubling discovery in the deepest ocean.Section CDirections: Read the passage carefully. Fill in each blank with a proper sentence given in the box.Each sentence can be used only once. Note that there are two more sentences than you need."The greatest scientists are artists as well," said Albert Einstein, one of the greatest physicists and an amateur pianist and violinist.For Einstein, insight did not come from logic or mathematics. (67) _________ As he told one friend, "When I examine myself and my methods of thought, I find that the gift of imagination has meant more to me than any talent for absorbing absolute knowledge. All great achievements of science must start from intuitive knowledge. Imagination is more important than knowledge.But how did art differ from science for Einstein? Surprisingly, it wasn't the content of an of an idea, or its subject, that determined whether something was art or science, but how the idea impressed. If what is seen and experienced is described in the language of logic, then it is science. If it is communicated and recognized intuitively, then it is art. (68) _________ That's why he said that great scientists were also artists. Einstein first described his intuitive thought processes at a physics conference in Kyoto in 1922 when he indicated that he used images and feelings to solve his problems and found words, logical symbols or mathematical equations later.(69) _________ "If I were not a physicist," he once said, "I would probably be a musician. I often think in music and I see my life in terms of music. I get most joy in life out of music. Whenever I feel that I have come to the end of the road or into a difficult situation in my work, I would bury myself in music, and that would usually solve all my difficulties."Music provided Einstein with a connection between time and space which both combine spatial and structural aspects. "The theory of relativity occurred to me by intuition and music is the driving force behind this intuition. My parents had me study the violin from the time I was six. (70) _________" said Einstein.第II卷IV. Summary WritingDirections: Read the following three passages. Summarize the main idea and the main point(s) of the passage in no more than 60 words. Use your own words as far as possible.71. Why Do Chinese Parents Prefer Legos to Barbies?Budding engineers cluster around a table-sized model of the China Art Museum, a landmark of Shanghai, adding helipads, carrot patches and other improvements with colorful bricks. Prising a child from Lego's vast shop near People's Square can be like un-sticking two stubborn bits of Lego. Li Yang, visiting for a few days from Shenzhen, has been waiting for her daughter for twohours. Zhu Yunfei, watching his son, marvels at the variety: "Coming here to play with him is making up for my childhood," he says. They drop by every week.Lego's rise in China has been rapid and dramatic. In 2017 it overtook Alpha Group, a local giant, to become the country's leading toy company (not including video games). In the past two years it has opened 89 stores. It wants 50 more by December, which will bring it to 30 cities. Its first Chinese factory started molding bricks in 2016. The toy industry is growing by 9% annually in the country, but the Danish firm's Chinese arm notches up "very strong double digits," says Paul Huang, its boss.It has done so even as the brick maker's global business has looked shakier. In 2017 Lego cut 1,400 jobs and recorded its first drop in revenues and profits in over a decade. But last year both ticked up again, by 4% each. Lego has thus retained its status as the world's biggest toy-maker, taken from Mattel in 2014 -- even as its American rival last year earned its highest revenues in five years from its Barbie dolls.Newly affluent parents in China have helped Lego recover. "We have not maxed out there, by far," says Niels Christiansen, whom Lego brought in as chief executive two years ago. As in the West, the educational merits of bricks appeal to Chinese parents. Last year 98% of those surveyed Lego said that play was essential for their child's well-being, even more than Americans and Danes.V. TranslationDirections: Translate the following sentences into English, using the words given in the brackets.72. 第一部小说就被成功改编成电影，新晋才女作家名利双收。

第一章公共用语口述题1。

Please say something about your hometown. 请评价一下你的家乡例一（简单)(1) My hometown is Dalian. Dalian is a beautiful city. 我的家乡是大连。

大连是一座美丽的城市。

It is in the Liaoning Province，facing the Bohai Sea. 它是在辽宁省,面对渤海.There are about 5 million people in the city. 大约有500万人在城市。

(2） It is a famous tourist coastal city in China。

Its climate around the year is suitable and comfortable for living. 它是著名的旅游沿海城市，整年的气候很合适,舒适对于的生活。

The sky is blue and the air is clean. There are many famous spots attracting many tourists every year. 天空是蓝色的，空气是那么清新。

有许多著名的景点每年吸引了很多游客。

(3) The specialties of Dalian is the seafood。

There are many good restaurants providing delicious seafood。

大连特色是海鲜。

有很多好的餐厅提供可口的海鲜.例二(稍难）I come from Zhoushan我来自舟山Zhoushan is a city in Zhejiang province舟山是浙江省一个城市It is a small city with a population of about 100,000. 这是一个小城市的人口大约10万It is located by the sea。

射流泵喷嘴收缩角的取值吕忠斌;王洋;刘洁琼;曹璞钰;李贵东【摘要】为了研究喷嘴收缩角对射流泵性能的影响,采用数值计算和试验研究相结合的方法,对浙江某公司生产的XDPm255A型射流泵进行了研究.根据Fluent的数值模拟结果,在射流泵不同面积比下,分析不同的喷嘴收缩角对射流泵内部流场以及外特性的影响.通过数据拟合,进一步得到面积比在2.01 ～5.06时射流泵喷嘴收缩角在高效区取值的拟合趋势线,并对其进行试验验证.结果表明:当射流泵的面积比一定时,对应不同的喷嘴收缩角均存在1个最优流量比,其可使射流泵的效率达到最高;当面积比增大时,最优流量比也随之增大;射流泵高效区喷嘴收缩角取值拟合趋势线是可靠的.【期刊名称】《江苏大学学报（自然科学版）》【年(卷),期】2015(036)003【总页数】7页(P281-287)【关键词】射流泵;喷嘴收缩角;数值计算;面积比;流量比【作者】吕忠斌;王洋;刘洁琼;曹璞钰;李贵东【作者单位】江苏大学流体机械工程技术研究中心,江苏镇江212013;江苏大学流体机械工程技术研究中心,江苏镇江212013;江苏大学流体机械工程技术研究中心,江苏镇江212013;江苏大学流体机械工程技术研究中心,江苏镇江212013;江苏大学流体机械工程技术研究中心,江苏镇江212013【正文语种】中文【中图分类】TH311射流泵是利用射流紊动扩散作用来传递质量和能量的一种流体机械［1］.其本身没有运动部件，具有密封性好、工作可靠和安装维护方便等优点.因此，射流泵被广泛应用于电力、冶金、水利、化工、环境保护以及航空航天等领域［2-5］.但是，由于内部漩涡、流动摩擦以及液流扩散带来的损失，射流泵的效率普遍偏低［6-7］.尽管国内外学者已经就射流泵的喷嘴直径、喉管直径、喉管长度和喉嘴距等方面对射流泵性能的影响进行了大量研究［8-11］，目前工程上喷嘴收缩角取值范围较大，往往缺乏一定的确定性，对射流泵性能的影响较大，于是喷嘴收缩角的研究价值凸显.笔者采用数值计算和试验研究相结合的方法，就XDPm255A型射流泵喷嘴收缩角对射流泵性能的影响进行研究.根据数值计算结果，在不同面积比时，分析不同喷嘴收缩角下射流泵的内部流动特性以及外特性.通过数据拟合，试图得到一定面积比范围内喷嘴收缩角取优的拟合趋势线.再通过试验研究，验证拟合趋势线的可靠性并应用于工程实践.1 研究对象1.1 射流泵量纲一参数通常在描述射流泵的性能、基本性能方程及相似定律时，均采用量纲一参数.射流泵的主要量纲一参数如下:1)研究时的设定参数面积比为式中:F2为喉管断面面积，m2;F1为喷嘴出口断面面积，m2.2)数值计算或试验时的设定值流量比为式中:Qs为被抽送流体流量，m3·h-1;Q1为工作流体流量，m3·h-1.3)数值计算或试验所得值扬程比为式中:H2为射流泵出口扬程，m;Hs为被抽送流体扬程，m;H1为工作流体扬程，m.4)数值计算或试验研究的目标值效率为式中:ρ为密度;g为重力加速度.1.2 射流泵基本参数及建模XDPm255A型射流泵整机的性能参数:泵最大流量Qmax=4.5 m3·h-1;泵最高扬程Hmax=60 m;喷嘴处最高扬程Hsmax=25 m;泵功率P=6.5 kW.其射流部分的主要设计参数:喷嘴收缩角α=33.2°;喷嘴出口直径d0=6 mm;喉管入口段收缩角β=49.5°;喉管直径d3=8.7 mm;喉嘴距Lc=12.5 mm;喉管长度Lh=45 mm;喷嘴出口圆柱段长度l=3 mm;出口扩散角θ=5.8°.采用Pro/E软件构建射流泵计算区域的3维水体模型如图1所示.图1 计算区域3维模型图1.3 网格划分计算模型采用Fluent前处理软件GAMBIT进行网格划分，划分时采用适应性较强的四面体非结构网格［12］.为了确定最佳网格数，选取网格数为65万到200万的6组模型进行数值计算.对数值计算结果进行比较后发现，在网格数达到150万后，效率波动稳定在0.5%以内.因此，综合考虑计算机性能，最终选取计算模型的最佳网格数为150万.1.4 边界条件等相关软件设置采用RNG k-ε模型［13］对该射流泵进行数值模拟计算.进口边界条件中高压水进口和低压水进口(如图1所示)均采用速度进口;出口边界条件采用自由出流;壁面边界条件为在固壁处采用无滑移边界条件，近壁区采用标准壁面函数修正湍流模型. 压力和速度的耦合方式采用SIMPLE算法.在四面体网格中，采用2阶中心差分格式离散控制方程组的源项和扩散项，并用2阶迎风格式离散控制方程组的对流项.松弛因子先保持默认值，然后根据计算情况做适当的调整.计算收敛精度为10-4. 收敛判据:所有残差均小于10-4;出口压力值稳定，不再随着迭代次数的增加而变化.1.5 性能曲线将模拟和试验值根据式(2)-(4)进行计算，得出的射流泵外特性模拟结果和试验结果进行对比分析，绘出的性能对比曲线如图2所示.图2 原泵性能曲线对比图图2中，数值模拟计算得到的扬程比和效率值均与试验结果较为接近.经进一步计算，模拟所得扬程比平均相对误差约为1.78%，效率平均相对误差约为2.39%，则模拟计算精度较高，对该射流泵的数值模拟计算是可靠的.2 数值计算与分析在实际工程应用中，XDPm型射流泵常用的面积比为2.01～5.06.而锥直形喷嘴［14］在30倍大气压下时，多采用15.0°～45.0°的喷嘴收缩角.结合XDPm255A型射流泵的结构要求与实际工艺水平，并考虑收缩角过小引起的流速太快可能带来其他不利影响，工程上XDPm255A型射流泵常用的喷嘴收缩角为25.0°～35.0°.选取面积比为 2.01，3.01，3.48，4.01 和 5.06的射流泵进行研究，在每个面积比下对喷嘴收缩角分别为25.0°，27.5°，30.0°，32.5°和35.0°这5 种不同结构形式的模型进行各工况下的数值模拟计算.文中着重对面积比为2.01，3.48和5.06的射流泵进行分析.2.1 面积比为2.01时的数值计算结果分析当面积比为2.01时，对5种不同喷嘴收缩角下的射流泵进行定常数值计算.再选取喷嘴收缩角为25°，30°和35°时的射流泵进行着重分析.在 R=2.01时，相应的模拟效率曲线如图3所示.图3 流量比与效率关系曲线(R=2.01)从图3可以看出:在不同流量比下，喷嘴收缩角为25.0°时射流泵的效率值最高，喷嘴收缩角为35.0°时，射流泵的效率值最低;在不同喷嘴收缩角下，射流泵的效率曲线分布趋势基本一致;每个喷嘴收缩角都存在一个最高效率点和其对应的最优流量比.选取流量比为0.49时射流泵的数值计算结果进行分析.静压分布如图4所示.图4 静压分布图从图4可以看出:对于面积比一定的射流泵，当喷嘴收缩角为25.0°时，喷嘴出口的压力较小;随着射流泵喷嘴收缩角的增大，喷嘴出口处压力逐渐增大;且当喷嘴收缩角为30.0°和35.0°时，2种结构下射流泵的静压分布情况基本一致.速度分布如图5所示.图5 速度分布图从图5可以看出:对于面积比一定的射流泵，当喷嘴收缩角较小时，流场中速度较快且衰减较慢;随着喷嘴收缩角的增大，喷嘴出口速度减小，流体的压力恢复较快.面积比为2.01时不同喷嘴收缩角下的射流泵效率尽量取最高值后的效率-喷嘴收缩角连线(简称取高效率连线)如图6所示.图6 取高效率连线(R=2.01)结合图3，从图6可以看出:随着喷嘴收缩角的增大，射流泵的整体效率逐渐降低.参照文献［15］以最高效率下降3%来确定射流泵的高效区，由图6可知:面积比为2.01时，射流泵高效区的效率为26.97%～27.8%，相应的较优喷嘴收缩角取值范围为25.0°～34.8°，即为喷嘴收缩角的取优范围.因此，可以得出:面积比为2.01时，射流泵在高效区可取的喷嘴收缩角最大值为34.8°.2.2 面积比为3.48时的数值计算结果分析当面积比为3.48时，数值模拟计算及分析方法与2.01时相同，相应的效率曲线如图7所示.图7 流量比与效率曲线(R=3.48)从图7可以看出:不同喷嘴收缩角下，射流泵的效率曲线分布趋势基本一致;在流量比为0.7时，喷嘴收缩角为30.0°和35.0°的射流泵的效率值几乎相等.在R=3.48时取高效率连线如图8所示.参照面积比为2.01时射流泵喷嘴收缩角取优的方法，从图8可以看出:面积比为3.48时，射流泵在高效区可取的喷嘴收缩角最大值为31.4°，最小值不变.图8 取高效率连线(R=3.48)2.3 面积比为5.06时的数值计算结果分析当面积比为5.06时，数值模拟计算及分析方法亦相同，相应效率曲线如图9所示. 图9 流量比与效率关系曲线(R=5.06)从图9可以看出:喷嘴收缩角为25.0°和35.0°时，射流泵的效率曲线分布趋势基本一致;喷嘴收缩角为30.0°时，效率曲线分布不规律，且此时当流量比为1.96时，射流泵的效率最低.同样参照面积比为2.01时射流泵喷嘴收缩角取优的方法，从图10可以得出:面积比为5.06时，射流泵在高效区可取的喷嘴收缩角最大值为26.9°.图10 取高效率连线(R=5.06)从图3，7，9中可以得出:当射流泵的面积比一定时，对应不同的喷嘴收缩角均存在一个最优流量比，使射流泵的效率达到最高;而当面积比增大时，射流泵的最优流量比也随之增大.这一点对于提高射流泵的效率具有重要的理论与实际意义.2.4 面积比为3.01和4.01时的喷嘴收缩角取优面积比为3.01和4.01时不同喷嘴收缩角下射流泵取高效率的连线分别如图11，12所示.参照面积比为2.01时射流泵喷嘴收缩角取优的方法，可以得出:面积比为3.01时，射流泵在高效区可取的喷嘴收缩角最大值为33.6°;面积比为4.01时，其最大值为29.1°.图11 取高效率连线(R=3.01)图12 取高效率连线(R=4.01)2.5 拟合曲线综合以上分析可知:5种面积比结构形式下的射流泵，均存在使其一直处于高效区的喷嘴收缩角.当面积比为2.01，3.01，3.48，4.01 和5.06 时，对应喷嘴收缩角取优范围的最大值分别为34.8°，33.6°，31.4°，29.1°和26.9°，最小值为25.0°不变.使用Excel软件拟合5种面积比结构形式下射流泵喷嘴收缩角取优的上下限值如图13所示，可以得到面积比在2.01～5.06的范围内时，图13中阴影部分的射流泵较优喷嘴收缩角的取值范围，而范围上限曲线即为射流泵在不同面积比下高效区喷嘴收缩角最大可取值的拟合趋势线.图13 数值计算结果拟合曲线从图13可以看出:随着面积比增大，喷嘴收缩角在高效区的取值范围呈逐渐缩小的趋势，这对于实际工程应用具有一定参考价值.同时，高效区喷嘴收缩角最大取值随着面积比而循着拟合趋势线变化，这种规律对于工程应用中需要尽量取大喷嘴收缩角的情况具有较大指导意义.3 试验验证3.1 试验装置选取面积比为3.48，喷嘴收缩角分别为25.0°，27.5°，30.0°，32.5°和35.0°的射流泵进行试验研究，射流泵试验装置简图如图14所示.图14 射流泵试验装置简图当试验装置稳定运行时，控制调节阀，依次测量流量比为0.70，0.92，1.12和1.36时每个射流泵的外特性.3.2 试验结果及分析对不同喷嘴收缩角的射流泵进行试验，选取喷嘴收缩角为25.0°，30.0°和35.0°时的试验进行着重说明.相应的射流泵效率试验值与模拟值对比曲线如图15所示.图15 流量比与效率对比曲线将试验所得效率曲线与模拟值的效率曲线进行比较分析，发现相应流量比下射流泵的效率值偏差在3%以内.再次证明，数值计算较为真实地反映了射流泵的流动特性. 图16为面积比等于3.48时不同喷嘴收缩角下射流泵试验所得的取高效率连线与模拟所得的对比图，可以发现两条曲线的趋势基本一致.用与前文数值计算结果分析时相同方法可求得，射流泵在高效区可取喷嘴收缩角的试验最大值为32.1°，而由数值计算结果求得的最大值为31.4°，二者十分接近，从而间接验证了前文所得拟合趋势线的可靠性.图16 试验所得的取高效率连线与模拟值对比图4 结论1)根据数值计算结果，在不同面积比下，分析不同的喷嘴收缩角对射流泵效率的影响.研究表明:面积比一定时，对应不同的喷嘴收缩角均存在最优的流量比使效率最高;随着面积比的增大，射流泵的最优流量比也逐渐增大.2)通过数据拟合，得到面积比在2.01～5.06时，射流泵喷嘴收缩角的取优范围及高效区收缩角最大取值的拟合趋势线.由拟合趋势线可以看出:随着面积比的增大，射流泵高效区的喷嘴收缩角最大可取值循着趋势线变化.这对射流泵的设计和工程应用意义重大.3)对面积比一定的射流泵进行试验分析，验证了拟合趋势线的准确性.4)本研究成果已应用于XDPm系列产品中，为射流泵的进一步研究和实际工程应用中喷嘴收缩角的合理取值提供了指导.参考文献(References)【相关文献】［1］曾庆龙，龙新平，肖龙洲，等.环形射流泵结构优化设计［J］.排灌机械工程学报，2014，32(2):98-102.Zeng Qinglong，Long Xinping，Xiao Longzhou，et al.Structure optimization of annular jet pumps［J］.Journal of Drainage and Irrigation MachineryEngineering，2014，32(2):98-102.(in Chinese)［2］Wu Xiongjun，Jin-Keun C，Sowmitra S，et al.Experimental and numerical investigation of bubble augmented waterjet propulsion ［J］.Journal of Hydrodynamics，2012，24(5):635-647.［3］Zhang Fenghua，Liu Haifeng，Xu Junchao，et al.Experimental investigation on 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Maximum performanceat minimum weightKongsberg Maritime is improving and streamlining its steel serieswaterjets, further raising the unit efficiency as well as loweringthe cost of ownership. A modular system provides a choice ofinlet materials and installation strategies.Kamewa steel series waterjets provides the best pump efficiency on themarket, for each operational profile and purpose. The efficiency is improvedover the whole speed range, and matches the increased demand of vesselseven below 30 knots. This translates into reduced fuel consumption for agiven workload and consequently reduced CO2 emissions, as well asincreased range. Environmental benefits are achieved not only by increasingefficiency, the inboard hydraulics also reduce the risk of oil spill.Improved from the bestThe steel series incorporates numerous improvements made possible byadvanced design calculation methods and testing and production techniques.The compact reversing bucket and steering nozzle enables superior positionkeeping and manoeuvrability at low and high speed. This reduces fuelconsumption and lowering noise and emissions in harbour manoeuvring, aswell as saving time and increasing safety. In high speed turns the steel seriesmaintains speed very efficiently, which is a highly appreciated benefit forpatrol vessels and others alike.Low and high speed performance in the same packageAt the heart of the waterjet is the fully stainless steel mixed flow pump.There are different impellers depending on application. Efficiency hasbeen achieved by using the latest computational fluid dynamics (CFD)techniques combined with extensive testing in the cavitation tunnels at theKONGSBERG Hydrodynamics Research Centre. The steel series waterjets canbe individually optimised and selected based on boat design requirementsand operational profile.The lightest and most compact jet on the marketThe saving in weight has been achieved by integrating the hydraulics into thewaterjet.Heavy duty stainless steel pump unitThe steel series is as always equipped with a duplex stainless steel pumpunit providing the best possible durability under any circumstances. Best inclass components are used, providing long life and reliable service. These areenabling up to 15,000 h or 5 year time service/replacement of wear parts.Bollard pull capability closing the gap to conventional propulsorsKamewa waterjets have a new inlet duct design as standard, providingextremely good low and mid speed performance. In practice this meansincreased bollard pull thrust comparable to conventional propulsors. Highspeed inlets are available for speeds exceeding 45 knots.05.Waterjet-1 of 2-20.11.20Modularisation by customer choiceThe new Kamewa waterjet are designed for ease of installation and maintenance as well as meeting a variety of customer needs, such as hull material, hull design and forms and optimised inlet ducts.Skid versionInitially available between 25 to 63 steel series. As a standard steel series has inlets made of marine grade weldable aluminium as an integral part of waterjet unit. Larger sizes can optionally have inlets in material specified by customer. This alternative means quick and cost effective installation at the shipyard. Stand alone installation withseparate inlet ductAvailable from 56 to 200 steel series.Waterjets with inlet duct suppliedas loose item. Supplied in materialspecified by customer.This enablesoptimised performance, yet reduceslabour at the yard.Stand alone installation withinlet drawingAvailable from 56 to 200 steel series.Waterjets supplied with drawing ofhydrodynamic design of inlet duct.This enables optimal performanceand hull stiffness when building inFRP.Switchboard: +47 815 73 700Global support 24/7: +47 33 03 24 07E-mailsales:*********************.comE-mailsupport:************************Kongsberg MaritimeP.O.Box 483, NO-3601Kongsberg, Norway05.Waterjet-2 of 2-20.11.20TECHNICAL DATAWaterjet sizeS56-3S63-3S71-3S80-3S90-3S100-3S112-3S125-3S140-3*S160-3*S180-3*S200-3*Max power3440430051206500830010200128001590020000260003300041000TECHNICAL DATAWaterjet sizeS25-3/CAS28-3/CAS32-3/CAS36-3/CAS40-3/CAS45-3/CAS50-3/CAS56-3/CAS63-3/CAMax power45057075095013201670206025802600TECHNICAL DATAWaterjet sizeS56-4S63-4S71-4S80-4S90-4S100-4S112-4Max power2300280036004600580072008900DELIVERY PROGRAMME – STEEL SERIES WATERJETSThe diagram shows the three ways of delivering the waterjet to suit yard or owner preferences.Aluminium inletRemote control systemsKongsberg Maritime can supply a number of different control systems, ranging from rugged, standardised systemsand up to multi station, custom design systems. Skid version waterjets could even come with factory mountedand pre-calibrated control box. Functionality such as Interceptor trim can be included in the controls, while the Interceptor hardware installation is prepared on the waterjets. Modular bolt installation enables easy retrofitting.The interceptor trim system improves acceleration and low speed characteristics, in addition to trim angle adjustment. Other functionality such as berthing assistance and “stay on spot” can also be provided as extended options to a joystick system.KAMEWA WATERJET PROPULSION,SIZE 63-125 STEEL SERIES35030025020015010050Netthrust[kN]Shipresistanceperjet0 10 20 30 40 50Ship speed [knots]KAMEWA WATERJET PROPULSION,SIZE 25-56 STEEL SERIES70605040302010Netthrust[kN]ShipresistanceperjetShip speed [knots]10 20 30 40 50The final data is subject to application and to be confirmed by Kongsberg Maritime.S-3/CACOMPLETE SKID MOUNTED DELIVERYS-3 AND S-4DELIVERED AS SEPARATE UNITSS-3 AND S-4JET + INLET DRAWING* on request。

备考2023年高考英语二轮专题：阅读理解（自然与环保）一、阅读理解(共40题；共80分)阅读下列短文，从每题所给的四个选项（A、B、C 和D）中，选出最佳选项。

Curtin University research has found a simple and affordable method to determine which chemicals and types of metals are best used to store and supply energy, in a breakthrough for any battery-run devices and technologies relying on the fast and reliable supply of electricity, including smart phones and tablets.Lead author Associate Professor Simone Ciampi from Curtin's School of Molecular and Life Sciences said this easy, low-cost method of determining how to produce and keep the highest energy charge in a capacitor (电容器) could be of great benefit to all scientists, engineers and start-ups looking to solving the energy storage challenges of the future."All electronic devices require an energy source. While a battery needs to be recharged over time, a capacitor can be charged instantly because it stores energy by separating charged ions (离子), found in ionic liquids, " Ciampi said.There are thousands of types of ionic liquids, a type of "liquid salt", and until now, it was difficult to know which would be best suited for use in a capacitor. What our team has done is designing a quick and easy test, able to be performed in a basic lab, which can measure both the ability to store charge when a solid electrode touches a given ionic liquid—a simple capacitor—as well as the stability of the device when charged."The simplicity this test means anyone can apply it without the need for expensive equipment. Using this method, researchers found that charging the device for 60 seconds produced a full charge, which did not ‘leak' (渗漏) and begin to diminish for at least four days, " Mr Belotti said.The next step is to use this new screening method to find ionic liquid with an even longer duration in the charged state and larger energy density.1．（2分）What can the new method be used to do in the future?A．Help to choose smart phones.B．Find materials used as energy.C．Research energy sources of the future.D．Settle the problem of storing energy.2．（2分）What was the challenge in making a capacitor?A．Choosing the best ionic liquid.B．Figuring out the storing ability.C．Devising a quick and easy test.D．Recharging a battery instantly.3．（2分）What does the underlined word "diminish" in paragraph 5 probably mean?A．Charge.B．Develop.C．Decrease.D．Expand.4．（2分）What would be a suitable title for the text?A．The Importance of Selecting Ionic LiquidB．A Good Method to Seek Perfect Ionic LiquidC．Types of Ionic Liquids for Use in a CapacitorD．A Simple and Affordable Battery阅读短文，回答问题When a chunk of ice fell from a collapsing glacier(冰川)on the Swiss Alps' Mount Eiger in 2017, part of the long deep sound it produced was too low for human ears to detect. But these vibrations held a key to calculating the ice avalanche's(崩塌)critical characteristics.Low-frequency sound waves called infrasound that travel great distances through the atmosphere are already used to monitor active volcanoes from afar. Now some researchers in this field have switched focus from fire to ice: dangerous blocks snapping off glaciers. Previous work has analyzed infrasound from snow avalanches but never ice, says Boise State University geophysicist Jeffrey Johnson. "This was different," Johnson says. "A signature of a new material has been detected with infrasound."Usually glaciers move far too slowly to generate an infrasound signal, which researchers pick up using detectors that track slight changes in air pressure. But a collapse—a sudden, rapid breaking of ice from the glacier's main body—is a prolific infrasound producer. Glacial collapses drive ice avalanches, which pose an increasing threat to people in mountainous regions as rising temperatures weaken large fields of ice. A glacier "can become detached from the ground due to melting, causing bigger break— offs," says University of Florence geologist Emanuele Marchetti, lead author of the new study. As the threat grows, scientists seek new ways to monitor and detect such collapses.Researchers often use radar to track ice avalanches, which is precise but expensive and can monitor only one specific location and neighboring avalanche paths. Infrasound, Marchetti says, is cheaper and can detect break—off events around a much broader area as well as multiple avalanches across a mountain. It is challenging, however, to separate a signal into its components (such as traffic noises, individual avalanches and nearby earthquakes) without additional measurements, says ETH Zurich glaciologist Malgorzata Chmiel. "The model used by Marchetti is a first approximation for this," she says. Isolating the relevant signal helpsthe researchers monitor an ice avalanche's speed, path and volume from afar using infrasound.Marchetti and his colleagues are now working to improve their detectors to pick up more signals across at-risk regions in Europe, and they have set up collaborations around the continent to better understand signals that collapsing glaciers produce. They are also refining their mathematical analysis to figure out each ice cascade's physical details.5．（2分）What can we learn from Paragraph 2 and Paragraph 3?A．Infrasound has a major role to play in discovering new materials.B．Ice avalanches are a bigger threat to people than volcanic eruptions.C．Researchers are trying to use infrasound in detecting ice avalanches.D．Scientists employ infrasound more in mountain areas than in other places.6．（2分）Which is an advantage of infrasound over radar?A．The combination with other relevant signals.B．The accuracy in locating a certain avalanche.C．The ability in picking up signals in wider areas.D．The sensitivity in tracking air pressure changes.7．（2分）The underlined word "this" in Paragraph 4 refers to________.A．distinguishing different components of a signalB．detecting multiple avalanches at the same timeC．calculating the speed and path of ice avalanchesD．monitoring the specific location of ice break—offs8．（2分）Which of the following would be the best title for the passage?A．From Fire to Ice B．Glacier WhispersC．Nature is Warning D．Secret of Ice Avalanches阅读理解Hoping to live on the moon one day? Your chances just got a tiny bit better. Researchers found that lunar pits and caves reach stable temperatures, making them potentially suitable for human life.Planetary scientists at the University of California, Los Angeles have been doing the research. Although much of the moon's surface temperatures ranges from as high as 260 degrees during the day to as low as 280 degrees below zero at night, the moon has pits and caves where temperatures stay at roughly 63 degrees Fahrenheit, making human habitation a possibility, according to their new research.For perspective, a day or night on the moon equals a little over two weeks on the earth—making long-term research and habitation difficult with such extremely hot and cold temperatures. Researchers say these stable spots could transform the future of lunar exploration and long-term habitation. The shadowed areas of these pits could also offer protection from harmful elements, such as solar radiation, universal rays and micrometeorites (微小陨石).About 16 of the over 200 discovered pits most likely come from collapsed lava tubes—tunnels that form from cooled lava or crust, according to Tyler Horvath, a UCLA doctoral student and head of the research. The researchers think overhangs inside of these lunar pits, which were initially discovered in 2009, could be the reason for the stable temperature.The research team also includes UCLA professor of planetary science David Paige and Paul Hayne at the University of Colorado Boulder. "Humans evolved living in caves, and to caves we might return when we live on the moon," said Paige in a UCLA press release.There are still plenty of other challenges to establishing any sort of long-term human residence on the moon—including growing food and providing enough oxygen. The researchers made clear that NASA has no immediate plans to establish a base camp or habitations there.9．（2分）What did the researchers find?A．Humans like the life on the moon.B．People lived in lunar pits and caves.C．Steady temperature exists somewhere on the moon.D．Temperatures in caves and pits vary a lot on the moon.10．（2分）What do the shadowed areas act as protection against?A．Solar heat.B．Harmful liquids.C．Universal gases.D．Micrometeorites.11．（2分）What does the underlined word "evolved" probably mean in paragraph 5?A．Appeared.B．Developed.C．Hunted.D．Escaped.12．（2分）Why does NASA not establish any habitation there at present?A．It has no such plans.B．Food there tastes bad.C．Many challenges exist.D．There is no oxygen.阅读理解A new study combining linguistic, genetic and archaeological evidence has traced the origins of thefamily of languages including modern Japanese, Korean, Turkish and Mongolian and the people who speak them to millet (粟) farmers who inhabited a region in northeastern China about 9, 000 years ago.The findings detailed on Wednesday document a shared genetic ancestry for the hundreds of millions of people who speak what the researchers call Transeurasian languages across an area stretching more than 8, 000 kilometers.The findings illustrate how humankind's embrace of agriculture following the Ice Age powered the movements of some of the world's major language families. Millet was an important early crop as hunter-gatherers transitioned to an agricultural lifestyle.There are 98 Transeurasian languages. This language family's beginnings were traced to millet farmers in the Liao River valley, an area including parts of the Chinese provinces of Liaoning and Jilin and the region of Inner Mongolia. As these farmers moved across northeastern Asia, the descendant languages spread north and west into Siberia and east into Korea and over the sea to Japan over thousands of years.The research stressed the complex beginnings for modern populations and cultures."Accepting that the roots of one's language, culture or people lie beyond the present national boundaries is a kind of surrender of identity, which some people are not yet prepared to make," said comparative linguist Martine Robbeets, lead author of the study published in the journal Nature."Powerful nations such as Japan, Korea and China are often pictured as representing one language, one culture and one genetic profile. But a truth is that all languages, cultures and humans, including those in Asia, are mixed," Robbeets added.The origins of modem Chinese languages arose independently, though in a similar fashion, with millet also involved. While the ancestors of the Transeurasian languages grew millet in the Liao River valley, the originators of the Sino-Tibetan language family farmed millet at roughly the same time in China's Yellow River region, paving the way for a separate language expansion.13．（2分）What is the new study mainly about?A．The migration routes of millet farmers.B．The ancient origins of a large language family.C．The different ancestries of Transeurasian speakers.D．The shared features of some neighboring languages.14．（2分）What fueled the spread of Transeurasian languages?A．The transition of power.B．The diversity of lifestyles.C．The interaction of cultures.D．The adoption of farming.15．（2分）According to Robbeets, who may feel uncomfortable about the new findings?A．Those from agricultural countries.B．Those who deny their cultural identity.C．Those with a strong sense of nationalism.D．Those who are afraid to cross boundaries.16．（2分）What is the main function of the last paragraph?A．To draw a conclusion.B．To present likely consequences.C．To highlight the theme.D．To offer additional information.阅读理解A "secretive" new species of frog has been discovered on the forest floor in India's Western Ghat mountain range. Named the starry dwarf frog after the markings on its dark brown back, it is just 2 centimeters long.The frog, whose closest relatives are a group of species native to India and Sri Linka, is the only member of an ancient lineage (血统) dating back to millions of years ago, according to researchers from India and the US. It is unclear whether the species is descended from African or Asian frogs.A group of Indian and US researchers first came across the local species hidden in leaf-litter as part of a wider project to look for new frogs, lizards and snakes in the richly biodiverse region and stored it in a jar for later study. Genetic testing and a closer look at its shape, colouring and other features has shown that it doesn't match any existing species.Kartik Shanker of the Indian Institute of Science, who helped design the study, says while it is common to find new frogs in India, this one needs to be noticed. "This particular species not just is a new species, but also belongs to a new genus (属), and that makes it a little more special, " says Shanker.The number of known species of frog identified in India has climbed from around 200 to above 400 over the past two decades. While many species new to science are frequently immediately sorted as endangered, it is too early to say whether the starry dwarf frog is threatened. "They are very secretive," says Shanker, adding that the team didn't know the size of its population. The frog is active at night and lives near water.Habitat loss is a serious risk to frogs in tropical forests around the world, alongside threats such as a deadly fungus (真菌) that has been killing off amphibians (两栖动物) for the past four decades. But the newspecies was found in a reserved forest, meaning it will enjoy a degree of protection by Indian government agencies.17．（2分）What can we learn from paragraph 3?A．The species was discovered by tourists.B．The species was found in a rich region.C．The species was finally set free.D．The species was further studied.18．（2分）What can we say about the new frog?A．It is in small quantities.B．It is an endangered species.C．It is well worth attention.D．It is related to African or Asian frogs.19．（2分）What can be inferred from the last paragraph?A．Habitat loss is the chief threat to frogs.B．The new species may face less dangers.C．Tropical forests in India are all under protection.D．The Indian government determines to save frogs.20．（2分）Which of the following is a suitable title for the text?A．A rare frog species protected in IndiaB．A rise in species of frog seen in IndiaC．A secretive frog species discovered in IndiaD．A risk of habitat loss for frogs removed in India阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项。