1, Pinyin Rules: In Chinese Pinyin, "I" and "u" are two different vowel phonemes. According to the rules of pinyin, "iu" should be pronounced as [i? ], not [u]. So the pronunciation of "Liu" transliterated into "Liu" is [Li? ], not [Lu].
2. Historical reasons: The transliteration of place names in China is usually influenced by historical and cultural factors. In the process of transliteration of place names, the particularity of place names and the influence of local dialects are sometimes considered. Taking Lu 'an as an example, its pronunciation of "Lu" may be related to the local dialect or historical tradition.
3. Standardize Pinyin: Although the pronunciation [lu] of "Liu" does not conform to the normal pronunciation in the Pinyin Rules, it is a widely accepted transliteration method and has become the official Pinyin of Lu 'an, so this transliteration is adopted in formal occasions and signs.
Lu 'an City, Anhui Province, located in the east of China, is a prefecture-level city under the jurisdiction of Anhui Province. The reason why it is pronounced as "Lü ā n" in Pinyin, rather than directly transliterated as "Lü uā n", is that there are certain Pinyin rules and historical background in Chinese Pinyin, which leads to the transliteration of some place names not completely corresponding to the pronunciation of Chinese characters.
To sum up, the reason why Anhui Lu 'an is pronounced as "Lü ā n" instead of "Lü uā n" is based on the rules of pinyin and historical and cultural traditions. This transliteration method has been widely accepted and used by the society, and it is the official pinyin of place names.