**Abstract:**This paper presents a numerical study on the aerodynamics loss reduction characteristics after the leading-edge (LE) optimization in a low-pressure turbine linear cascade. The LE was optimized with a simple and practical method of “Class Function/Shape Function Transformation Technique” (CST). The simulation conditions, covering the whole working range, were independently determined by incidence, Reynolds number and Mach number. Quantitative loss analyses were carried out with a loss breakdown method based on volumetric integration of entropy production rates. To understand the reason of loss reduction, the local sources at different operating points were identified with entropy production rates. The results showed that LE optimization with the CST method played a positive role in decreasing the total losses, and the working range with lower loss was extended. The profile loss and the endwall loss were significantly reduced by the LE optimization, which were also verified to be the major causes of the total loss reduction by loss breakdown. The decrease of profile loss can be attributed to the boundary layer near the LE region and the boundary layer of downstream at off-design incidence. The reduction mostly came from the pressure side at negative incidence, while came from the suction side at the positive incidence. The endwall loss was decreased markedly about 2.5%–5% by the LE optimization at the incidence of ‒12°, which was 1% at the incidence of 12°. The mechanism for the endwall loss reduction at different incidences was different from each other. At negative incidence, the LE optimization diminished the corner separation vortex on the pressure side. While at positive incidence, the benefits came from three aspects, i.e., reduced suction LE separation bubbles close to the endwall, reduced passage vortex strength, and weakened shear process between passage vortex and trailing shed vortex. The loss of the downstream zone was relatively lower than that of the profile losses and the endwall losses. The effect of LE optimization on the loss of the downstream zone at different conditions was complex and it depended both on the profile boundary layer behavior at the suction trailing edge and on the passage vortex strength. 本文以低压涡轮直列叶栅为研究对象，采用数值模拟的方法对前缘优化前后全工况的叶栅损失特性进行相应研究。前缘几何构建基于一种简单的具有工程实用价值的技术——“形状变换函数技术”(CST)。研究工况由马赫数、雷诺数和攻角独立确定。损失特性的定量分析主要由熵产率体积积分的方式展开，在此基础上对叶栅流道内不同区域进行损失拆分，并进一步确定各工况条件下损失变化的局部位置和机理。结果显示：CST方法优化的前缘有利于降低叶栅总损失，使得叶栅在较宽的工作范围内具有相对较低的气动损失。其中，叶型损失和端区损失的降低是总损失降低的两个主要因素。在非设计攻角下，叶型损失降低主要来源于前缘局部区域以及下游的边界层的变化。负功角时，叶型损失降低主要发生在压力侧的边界层区域，相反，正攻角时，叶型损失的降低主要位于吸力侧的边界层区域。在攻角为-12°时，端区损失降低约2.5% ~ 5%，而攻角为12°时，端区损失降低1.0%。不同攻角条件下端区损失减小背后的机理是不同的：负功角条件下，端区损失降低的原因是前缘优化显著削弱了前缘压力侧的角区分离涡；正攻角条件下，端区损失降低的原因主要来自于三个方面：减小的吸力侧前缘分离泡，降低的通道涡的强度和削弱的通道涡和尾缘脱落涡的剪切过程。下游区域的损失变化程度相对前两者较小，并且前缘优化对下游区域损失的影响略复杂，其主要是受吸力侧尾缘边界层的特性和通道涡的强度共同决定的。

**Keywords:**low pressure turbine, leading edge, loss breakdown, loss audit, boundary layer, entropy production rates