【作者】 杨帆；

【导师】 叶宏；

【作者基本信息】 中国科学技术大学 ， 工程热物理， 2021， 博士

【摘要】 以柴油发动机带动交流电机发电的电源舱是一种可应用于国防领域的厢式发电机组,其红外和噪声特倍受关注。弱红外特征是实现电源舱红外隐身的必要条件,低噪声特征可为人员提供舒适的声学环境。为抑制电源舱红外和噪声特征,我们从红外辐射和声波的产生机理及诱因关系出发,开展了以下工作。电源舱主要由舱壁围合柴油发电机组而成。发电机组主要由发动机本体、进气歧管、排气歧管、排气管、抗性消声器、水箱散热模块和发电机构成。沿气流方向,舱室由隔板分为进风舱和排风舱,舱壁分为进风面、侧面和排风面。为获得电源舱红外和噪声特征,利用热电偶和红外热像仪采集了舱内热源温度和电源舱外壁面红外热像图,分析了热源特性和外壁面红外特征分布;利用噪声频谱分析仪采集了舱内噪声源噪声频谱特性、近场噪声级分布、1m处的噪声频谱和噪声级,并进行了分析。红外实验研究发现,舱内主要热源有排气系统、发动机本体和水箱散热模块;电源舱进风面最高红外辐射温度仅为39℃,红外特征很弱,侧面最高红外辐射温度达65℃,红外特征显著,排风面最高红外辐射温度达73℃,红外特征最显著。噪声实验研究发现,舱内主要有表面振动和空气动力两类噪声源,均表现为宽频的高噪声级。前者包括发动机和发电机,其噪声主要涵盖中高频区间(500～4k Hz),噪声级达97.6～100.0 dB(A);后者包括进气、排气和冷却风扇,其噪声涵盖低中高频区间(63～4k Hz),噪声级达95.0～99.6dB(A)。在这两类噪声源共同作用下,电源舱进风面、侧面和排风面的近场噪声级分别处于 82.0～94.1 dB(A)、81.2～87.8dB(A)和 80.2～91.3 dB(A),高噪声区位于进、排风口处。此外,舱壁对高频噪声抑制效果较为显著,可使距电源舱1m处的平均噪声级从92.2 dB(A)降至81.0 dB(A),高于ISO8528-10规定的噪声限值(75.0 dB(A))。为抑制电源舱红外特征,提出并设计了一种可屏蔽发电机组热特征的冷屏系统,其热负荷通过散热器散向环境,使外壁面趋近环境温度。电源舱侧面拟采用由冷屏模块集成的平板冷屏,排风面可设计为由冷屏模块集成的百叶窗冷屏。构建了电源舱冷屏实验系统,论证了冷屏系统抑制红外特征的可行性。为优化和评估红外抑制效果,采用有限元软件I-DEAS构建了电源舱和冷屏系统仿真模型,优化了平板冷屏和百叶窗冷屏的模块结构和布局,并实验验证和仿真评估了优化后的冷屏系统红外抑制效果。实验研究表明,冷屏系统可有效抑制电源舱红外特征。当采用冷屏系统时,电源舱侧面测点温度与空气温度的最大差值仅为3.9℃,排风面测点温度与空气温度的最大差值可低至8.4℃。仿真研究表明,平板冷屏内侧仅需单排管且只需应用于排风舱侧面,优化后的百叶窗冷屏由5个240 mm宽的模块构成,冷屏模块倾角为48°,管间距为30mm。与原电原舱相比,优化后的冷屏系统可使电源舱侧面与环境空气最大温差从28.6℃降至1.0℃,排风面与环境空气最大温差从34.8℃降至5.2℃,显著抑制了电源舱红外特征。为兼顾噪声和红外特征的抑制,实验分析了电源舱噪声和红外特征的诱因。电源舱噪声和红外特征的诱因多样且紧密关联,产生机械噪声的发动机本体、产生气动噪声的排气系统和水箱散热模块等主要噪声源也是导致红外特征显著的主要热源。为同时实现低噪声和弱红外特征,从关键源项出发,提出将水箱散热模块解耦的设想。为此,将水箱散热器外置,为其匹配了低噪声电控风扇,并为水箱散热模块设计了外壁有风屏的风道,利用浮力驱动的风屏屏蔽水箱风道红外特征。为抑制宽频排气噪声,排气消声系统采用了阻抗消声器。为屏蔽发电机组噪声和红外特征,舱壁设计为由外到内为“不锈钢蒙皮+阻尼垫+吸声隔热棉”的复合层结构,并改进了舱壁进、排风口。采用I-DEAS构建了所设计的电源舱和水箱风道仿真模型,论证了弱红外特征设计的可行性。最后,基于上述设计搭建了电源舱实验系统,实验研究了噪声和红外抑制效果。实验研究表明,经上述设计后,水箱风道近场高噪声级仅位于进、排风口处,分别为74.1 dB(A)和77.3 dB(A),对电源舱噪声无明显贡献。水箱风道与环境空气的最大温差低至10.0℃,有效降低红外特征。采用阻抗两级消声器明显消除了宽频排气噪声,噪声级降低了13.9 dB(A),显著降低了其对电源舱噪声的贡献。设计后的电源舱近场噪声级由顶到底逐渐升高,进风面、侧面和排风面的近场平均噪声级分别从87.5 dB(A)降至 77.5dB(A)、从 84.1 dB(A)降至 76.0dB(A)和从 84.8dB(A)降至 79.5dB(A)。距电源舱1 m处的平均噪声级从81.0 dB(A)降至72.5 dB(A),低于ISO8528-10规定的噪声限值(75.0dB(A))。此外,电源舱侧面与排风面和环境空气的最大温差分别从29℃降至12℃、从37℃降至8.0℃,显著抑制了电源舱红外特征。该设计提供了一种可同时实现电源舱低噪声和弱红外特征的有效抑制方法。基于电源舱产热、传热特性及噪声源频谱、声波传播特性的研究,从热、声源项和舱壁围护结构等角度,提出了针对性的红外和噪声抑制方法,实现了电源舱弱红外和低噪声特征,对机动装备在国防领域的应用具有重要借鉴意义。更多还原

【Abstract】 A power generation cabin,which uses a diesel engine as the prime mover to drive a generator to generate electricity,is a van diesel genset that can be applied to the field of defense.The infrared and noise signatures of the power generation cabin are of great concern.Weak-infrared signature is requisite for achieving infrared stealth of the power generation cabin,and low-noise signature can provide personnel with a comfortable acoustic environment.To suppress the infrared and noise signatures,the following works have been conducted starting from the generation mechanism and inducement relationship of both infrared radiation and sound wave.The power generation cabin is mainly composed of a diesel genset enclosed by a cabin wall.The genset is mainly composed of an engine body,an intake manifold,an exhaust manifold,an exhaust pipe,a reactive muffler,a radiator module and a generator.Along the airflow direction,the cabin is divided into an air-inlet cabin and an air-outlet cabin by a partition,and the cabin wall is composed of the inlet,lateral and outlet sides.To obtain the infrared and noise signatures,the thermocouples and infrared imager were used to collect the heat sources’ temperatures and the infrared images of the outer wall of the power generation cabin,and the heat sources’ characteristics and the infrared signatures’ distribution of the outer wall were analyzed.Also,a noise spectrum analyzer was used to collect the noise spectrums of the noise sources,the near-field noise levels,the noise spectrums and levels at a 1 m distance from the cabin,and the results were analyzed.It is found through experimental investigation on infrared signature that,the main heat sources are the exhaust system,the engine body and the radiator module.The maximal infrared temperature of the inlet side is only 39℃,showing a weak infrared signature,while the the maximal infrared temperature of the lateral and outlet sides are 65℃ and 73℃ respectively,showing a prominent infrared signature.It is found through experimental investigation on noise signature that,there are mainly the surface vibration noise sources and the aerodynamic ones,all of which show a high noise levels with a wide frequency band.The former includes engine and generator,which noises mainly cover the mid and high frequency range(500～4k Hz),with the noise levels of 97.6～100.0 dB(A).The latter includes intake,exhaust and cooling fan,which noises cover the low,mid and high frequency range(63～4k Hz),with the noise levels of 95.0～99.6 dB(A).Because of the effects of the two types of noise sources,the near-field noise levels on the inlet,lateral,and outlet sides are 82.0～94.1 dB(A),81.2～87.8 dB(A)and 80.2～91.3 dB(A)respectively,among which the high near-field noise levels locate at the inlet and outlet.Additionally,the cabin wall has a more significant suppression effect on the high-frequency noise,which can reduce the average noise level from 92.2 dB(A)to 81.0 dB(A)at a 1 m distance,higher than the noise limit of 75.0 dB(A)specified by ISO8528-10.To suppress the infrared signature,we proposed and conceived a cold plate system to shield the thermal characteristics of the genset.The heat load of the cold plate is dissipated to the ambient air through a radiator,enabling the outer wall temperature to approach the ambient temperature.In this system,a flat cold plate integrated by the cold plate modules were adopted as the lateral sides,while a louvered cold plate integrated by the cold plate modules was designed as the outlet side of the power generation cabin.Based on the above conception,the power generation cabin with the cold plate system was constructed,and its feasibility to suppress infrared signature was experimentally demonstrated.To optimize and evaluate the infrared suppression effect,the simulation models of the power-generation cabin and that with the cold plate system were established by a finite element software I-DEAS to optimize the module structure and layout of the flat cold plate and the louvered cold plate.Finally,the infrared suppression effect of the optimized cold plate system was experimentally validated and evaluated by simulation.It is experimentally confirmed that the cold plate system can effectively suppress the infrared signature of the power generation cabin.When adopting the cold plate system,the maximal temperature difference of the measuring points on the lateral and outlet sides with the ambient air is only 3.9℃ and 8.4℃,respectively.It is found through simulation that only the lateral sides for the air outlet cabin need the flat cold plates with a 1-row tube to suppress the infrared signatures,and the optimized louvered cold plate is composed of 5 blades with a 240 mm width,a 48° inclination angle and a 30 mm tube spacing.Compared with the original power generation cabin,the optimized cold plate system can reduce the maximal temperature difference of the lateral and outlet sides with the ambient air from 28.6℃ to 1.0℃ and from 34.8℃ to 5.2℃,significantly suppressing the infrared signature of the power generation cabin.To consider the noise and infrared suppression,the causes of both signatures are analyzed based on the experimental results.The inducements of the noise and infrared signatures of the power generation cabin are diverse and closely interrelated.The main noise sources,such as the engine generating mechanical noise,the exhaust system and radiator module generating aerodynamic noise,are also the main heat sources that lead the infrared signature of power generation cabin to be significant.To achieve low-noise and weak-infrared signatures simultaneously,starting from the key source items,we propose a conception of decoupling the radiator module from the power generation cabin.To this end,the built-in radiator was modified as an external one and a low-noise cooling fan with an electronic control unit was configured for the radiator,and an independent airduct with a wind screen was designed for the radiator module,shielding the infrared signature by the airduct wall with a buoyancy-driven air curtain.To suppress the wideband aerodynamic noises of the exhaust,an impedance composite muffler was adopted.To shield the noise and infrared signatures of the genset,a multi-layer structure with "steel sheet+damping blanket+insulation cotton" from outside to inside was designed as the cabin wall,and the dimensions and position of the inlet and outlet were improved.Then,the simulation models of the designed power generation cabin and the radiator airduct were construced by I-DEAS to demonstrate the feasibility of the weak-infrared signature design.Finally,the experimental system was built based on the above design,and the noise and infrared suppression effects of the new design were experimentally evaluated.It is found through experimental investigation with the new design that,the high near-field noise levels of the radiator airduct only locate at its inlet and outlet of airduct,with levels of 74.1 dB(A)and 77.3 dB(A),respectively,making an insignificant contribution to the noise of power generation cabin.Also,the maximal temperature difference of the radiator.airduct wall with the ambient air is as low as 10℃,effectively lowering the infrared signature.Adopting the impedance muffler can eliminate the wideband exhaust noise level by 13.9 dB(A),significantly reducing its contribution to the noise of power generation cabin.After the design,the near-field noise levels of the power generation cabin gradually increase from top side to bottom one,and the average near-field noise levels of the inlet,lateral and outlet sides decrease from 87.5 dB(A)to 77.5 dB(A),from 84.1 dB(A)to 76.0 dB(A)and from 84.8 dB(A)to 79.5 dB(A),respectively.The average noise level dropped from 81.0 dB(A)to 72.5 dB(A)at a 1 m distance,reaching the noise limit of 75.0 dB(A)specified by ISO8528-10.Also,the maximal temperature differences of the lateral and outlet sides with the ambient air drop from 29℃ to 12℃ and from 37℃ to 8℃,respectively,significantly suppressing the infrared signature.This design provides an effective solution to simultaneously achieve a low-noise and weak-infrared power generation cabin.Based on the investigations on the themal characteristics of the heat sources,heat transfer characteristics,the frequency spectrums of the noise sources as well as noise propagation characteristics,targeted solutions to the infrared and noise suppression are proposed from the aspects of the heat,sound sources and the cabin wall,realizing a weak-infrared and low-noise power generation cabin.This work has an important reference value for the application of mobile equipment in the field of defense.更多还原