在什么情况下容易出现虚假水位，调节时应注意些什么？
参考答案：汽包水位的变化不是由于给水量与蒸发量之间的物料平衡关系破坏所引起，而是由于工质压力突然变化，或燃烧工况突然变化，使水容积中汽泡含量增多或减少，引起工质体积膨胀和收缩，造成的汽包水位升高或下降的现象，称为虚假水位。①在负荷突然变化时，负荷变化速度越快，虚假水位越明显；②如遇汽轮机甩负荷；③运行中燃烧突然增强或减弱，引起汽泡产量突然增多或减少，使水痊瞬时升高或下降；④安全阀起座时，由于压力突然下降，水位瞬时明显升高；⑤锅炉灭火时，由于燃烧突然停止，锅水中汽泡产量迅速减少，水位也将瞬时下降。在运行中出现水位明显变化时，应分析变化的原因和变化趋势，判明是虚假水位或是汽包水位有真实的变化，及时而又妥当地进行调节。处理不当，可能会引起缺不满水事故。
James’s New Bicycle James shook his money box again. Nothing! He carefully __36__ the coins that lay on the bed. $24.52 was all that he had. The bicycle he wanted was at least $90! __37__ on earth was he going to get the __38__ of the money? He knew that his friends all had bicycles. It was __39__ to hang around with people when you were the only one without wheels. He thought about what he could do. There was no __40__ asking his parents, for he knew they had no money to __41__. There was only one way to get the money, and that was to __42__ it. He would have to find a job. __43__ who would hire him and what could he do? He decided to ask Mr. Clay for advice, who usually had __44__ on most things. “Well, you can start right here,” said Mr. Clay. “My windows need cleaning and my car needs washing.” That was the __45__ of James’s odd-job business. For three months he worked every day after finishing his homework. He was amazed by the __46__ of jobs that people found for him to do. He took dogs and babies for walks, cleared out cupboards, and mended books. He lost count of the __47__ of cars he washed and windows he cleaned, but the __48__ increased and he knew that he would soon have __49__ for the bicycle he longed for. The day __50__ came when James counted his money and found $94.32. He __51__ no time and went down to the shop to pick up the bicycle he wanted. He rode __52__ home, looking forward to showing his new bicycle to his friends. It had been hard __53__ for the money, but James knew that he valued his bicycle far more __54__ he had bought it with his own money. He had __55__ what he thought was impossible, and that was worth even than the bicycle.
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