改型前 meaning in English

pre modification
premodification

Remodeling the front rounds
改型前围
The results indicated that the efficiency of turbine was enhanced obviously , the efficiency curve overcasts the unchanged one completely . given the same output , the efficiency after retrofit design was higher than that before retrofit design , which was more distinct in high load area
结果表明，水轮机效率特性明显增加，其效率曲线完全包络改造前的效率以上区域，在发出相同效率的情况下，改型后效率均比改型前高，在高负荷区表现尤为明显。