为探究喷流高总温诱发热效应对超声速欠膨胀喷流流场与声场的影响规律与作用机制，采用大涡模拟（LES）与Ffowcs Williams-Hawkings声学类比（FW-H）相结合的混合方法对马赫数1.95的超声速欠膨胀喷流开展了数值模拟研究。通过对比不同喷流总温条件下的流场与声场数据，分析了热效应对喷流演化及远场辐射噪声的影响：热效应加快喷流剪切层发展，核心区长度缩短14.2%，增强核心区上游出口线处的湍流脉动，增大远场总声压级峰值且使峰值辐射方向往上游偏移，使宽频激波噪声声源位置上移。通过控制喷流参数设计对比工况，揭示了热效应中等速温升效应与等温增速效应对宽频激波噪声的差异化影响：等速温升效应增强核心区上游剪切层湍流，并通过改变喷流马赫数，缩短激波单元长度、削弱激波波系强度，导致宽频激波噪声声压级峰值减小且峰值频率增大；等温增速效应同样增强核心区上游剪切层湍流，但拉伸激波单元、增强激波波系，引起宽频激波噪声的声压级峰值显著增加并降低峰值频率。宽频激波噪声受二者作用，综合变化较小。热效应中等温增速效应对大尺度湍流噪声的作用占主导，强化了大尺度湍流噪声。

To investigate the influence and underlying mechanisms of thermal effects induced by high total temperatures on the flow and acoustic fields of supersonic underexpanded jets, numerical simulations were conducted on a Mach 1.95 supersonic underexpanded jet using a hybrid approach that combines Large Eddy Simulation (LES) with the Ffowcs Williams-Hawkings (FW-H) acoustic analogy. By comparing flow and acoustic data under varying total temperature conditions, the impacts of thermal effects on jet evolution and far-field radiated noise were analyzed. The results indicate that thermal effects accelerate the development of the jet shear layer, shorten the potential core length by 14.2%, and enhance turbulent fluctuations along the nozzle lip line upstream of the potential core. Consequently, thermal effects increase the peak far-field overall sound pressure level (OASPL), shift the peak radiation direction upstream, and move the source locations of broadband shock-associated noise (BBSAN) upstream. Subsequently, by designing comparative cases with controlled jet parameters, the thermal effect was decoupled into a temperature effect (constant-velocity heating) and a velocity effect (constant-temperature accelerating), revealing their differential impacts on BBSAN generation: the temperature effect enhances the shear layer turbulence upstream of the potential core, and by altering the jet Mach number, it shortens the shock-cell length and weakens the shock-wave intensity, leading to a decreased peak sound pressure level (SPL) and an increased peak frequency of the BBSAN; conversely, the velocity effect also enhances the upstream shear layer turbulence, but it elongates the shock cells and strengthens the shock-wave structure, resulting in a significantly increased peak SPL and a decreased peak frequency. Under the combined influence of these two effects, the overall variations in BBSAN are relatively minor. Furthermore, within the thermal effect, the velocity effect dominates the impact on large-scale turbulent mixing noise, thereby significantly enhancing it.