Reliability Analysis Of EMUs Air Condition System Considering Environmental Factors

The principle of “people first” is the paramount principle governing the operation of high-speed railway in our country.In the process of high-speed railway operation,it is not only important to ensure the safety and efficiency of the EMUs,but also to emphasize the enhancement of passenger comfort.As one of the vital systems responsible for regulating the interior environment of the EMU passenger compartment,the air conditioning system plays a crucial role.Its safety and reliability not only directly affect passengers’ travel experience but also indirectly impact the operational safety of other systems.Lanzhou-Urumqi High-speed Railway is deployed across vast regions with complex external environmental conditions.The air conditioning system operates for long durations throughout the year,irrespective of seasons.Due to high equipment loads and prolonged operation,the system is prone to failures.While some components of the air conditioning system are fully exposed to the external environment,others require gas exchange with the surroundings.The complex and ever-changing service environment results in diverse types and frequencies of failures,exhibiting a strong correlation with the external climatic conditions.Therefore,analyzing the shock of complex external service environments on air-conditioning system failures and system reliability,while reducing operational costs in actual maintenance processes without compromising safety requirements,is one of the urgent issues to be addressed.In this thesis,the following works were carried out:(1)A reliability model for the air conditioning system of EMU based on environmental factors is constructed from a data perspective: Based on the fault repair data of the air conditioning system in the EMU and the environmental monitoring data of the operating area,a grey correlation analysis is conducted to assess the correlation between external environmental factors and air conditioning system failures.The impact of each environmental factor on the air conditioning system is determined using an environmental hazard mat rix.On this basis,the environmental factors of the air conditioning system in the actual operating environment relative to the ideal operating environment are determined.This enables a comprehensive evaluation of the reliability of the air conditioning system in the actual operating environment.Furthermore,the influence of external environmental factors on the system reliability is quantified based on the environmental monitoring data.(2)The environmental shock degradation model is constructed from the perspective of mechanism: Environmental impacts can result in damaging shocks and lethal shocks,with the former leading to the degradation of shocks and the natural degradation of the system,ultimately causing the performance degradation and failure of the EMU’s air conditioning system.Simultaneously,the extreme environmental shocks pose a fatal impact on the system,resulting in sudden failures.These two failure modes compete with each other,leading to a time-variant reliability expression of the air conditioning system under the combined effects of environmental shocks and degradation,subject to certain performance threshold conditions.To validate the effectiveness of this model,fitting analysis is performed using failure data from the air conditioning system of the Lanzhou-Urumqi High-speed Railway.Furthermore,variations in environmental conditions are utilized to verify the accuracy and applicability of the constructed model,facilitating a quantitative assessment of the impact of environmental factors on the reliability of the air conditioning system.(3)A multi-level preventive maintenance strategy is realized based on time-varying reliability: To address the issues of excessive and insufficient maintenance caused by the current planned maintenance approach,a multi-level preventive maintenance strategy is introduced for equipment maintenance.This strategy yields a time-variant reliability function for the air conditioning system of the EMU within a single replacement cycle.Based on the existing maintenance models and assuming that the equipment reliability requirements are met,an optimized maintenance strategy is proposed from a cost-effectiveness perspective.This optimization aims to minimize the operational and maintenance costs of the air conditioning system within a preventive replacement cycle.The results obtained can provide valuable insights for localized operation and maintenance of the EMU fleet.