This project belongs to the field of aerospace science and technology. The power system is the heart of the aircraft. As an important component of the power system, the auxiliary power unit (APU for short) is a high-speed small gas turbine engine that continuously provides electricity and gas source to the aircraft, supplies power to airborne equipment, and supplies air to the environment. Gas supply to the control system and starting the main engine are the key to the aircraft's secondary power system, ensuring the aircraft's self-sufficiency and flight safety. This project is aimed at the urgent needs of major national large passenger aircraft science and technology projects. With the support of the Ministry of Industry and Information Technology's Civil Aircraft Project and the Civil Aviation Administration's Airworthiness and Safety Project, it focuses on the system integration of key core equipment to improve the safety and reliability of the auxiliary power unit system., maintainability and economy, this project studies key technologies for the integrated design of APU installation packages, including the design of air intake system, ventilation and cooling system, exhaust system, installation system and drainage system. It has broken through the technical problems of high reliability, low noise, lightweight and high precision of the APU system, and achieved the following innovative results: 1 For the first time, the intensive design method for APU installation was proposed on domestic civil aircraft, and the integration of intake and ventilation cooling was used for the first time. Integrated design technology invented an integrated intake and exhaust muffler device. 2 For the first time in domestic civil aircraft, a design scheme for APU installation bars based on damage safety was adopted. A method for decomposing and matching multiple flexible interface offsets was proposed, forming a collaborative adjustment technology for statically indeterminate complex bars, which significantly improved APU safety and usability. 3. An APU reachability evaluation method based on virtual maintenance technology is proposed, which further forms a set of APU maintainability solutions applied to narrow cabins, significantly shortening the maintenance time of cabin equipment such as route replaceable units (LRUs). 4 A hoisting mechanism that can adjust the attitude of the APU was invented, which solved the problem that the APU can only be disassembled by jacking, and greatly saved the APU disassembly time on the route. At the same time, the project overcame technical difficulties such as high-temperature space heat dissipation, composite material fire protection, high-frequency noise suppression, and three-dimensional error adjustment, and solved the problems such as the APU cannot operate after a mounting rod fails and the APU lubricating oil radiator cannot be replaced in situ. The design and application of a highly reliable, highly integrated and lightweight APU installation package has been completed, achieving a 2 dB reduction in noise indicators compared with ICAO requirements, a 30kg reduction in weight, and a reduction in maintenance time from 60 minutes in the original plan to 30 minutes. Reducing the weight of 1kg will save the fuel cost of the single machine by 4298 yuan/year, shorten the replacement time, avoid flight delays caused by the failure of the APU oil radiator and APU body, and save the maintenance cost of the single machine by 1296 yuan/year. As of February 26, 2018, the number of orders for 815 C919 aircraft has been received. Conservative consideration of the aircraft's operation for 20 years, this project will help airlines save fuel costs and maintenance costs by at least 2.12 billion yuan. This project authorizes 5 invention patents, 4 utility models, 1 software copyright registration, formulates 20 corporate standards and specifications, and publishes 20 papers, including 5 SCI/EI, and won the first prize for scientific and technological achievements of the Shanghai Aerospace Institute. It belongs to the domestic leader and internationally advanced, and has carried out many exchanges and sharing in peer exchanges in the aviation industry. The results of this project have been applied to ARJ21 - 700 aircraft and C919 large passenger aircraft, passed laboratory verification, and test flight tests have been carried out. The results have been promoted and applied to the design of long-range wide-body passenger aircraft, which has a significant effect on improving the system integration of airborne equipment in the aviation industry. It can significantly reduce aircraft weight, reduce airport noise pollution, reduce fuel consumption, save maintenance costs, and effectively drive the development of the domestic civil aircraft industry. It has promoted the development of the domestic aviation industry, driven the development of high-end equipment manufacturing, and achieved obvious economic and social benefits.