Insights into thermodynamic performance of a hypersonic precooled air-breathing engine with a complicated multi-branch closed cycle

An advanced precooled airbreathing engine with a closed Brayton cycle is a promising solution for high-speed propulsion,of which the Synergetic Air Breathing Rocket Engine(SABRE)is a representative configuration.The performance of the latest SABRE-4 cycle was analyzed in this paper.Firstly,a relatively complete engine performance model that considers the characteristics of turbomachinery and heat exchangers was developed.Then,Sobol’global sensitivity analysis of key performance parameters was carried out to identify the most influential design variables.Optimal specific impulses under different target specific thrusts were obtained by particle swarm optimization,of which the thermodynamic parameters corresponding to a specific thrust of 1.12 kN·s·kg^(-1)and a specific impulse of 3163 s were chosen as the design values.Four different control laws were analyzed in contrast,and the charge control method had the strongest ability of thrust regulation as well as maintaining a favorable specific impulse performance.Finally,working characteristics under the charge control and over a typical flight envelope were calculated,in which the average value of the maximum specific impulse was as high as 5315 s.This study would help to deepen the understanding of SABRE-4 thermodynamic characteristics and other precooled airbreathing engine cycles with similar layouts.

Micromanufacturing technologies of compact heat exchangers for hypersonic precooled airbreathing propulsion: A review

The Hypersonic Precooled Combined Cycle Engine(HPCCE), which introduces precooler into traditional hypersonic engine, is regarded as the most promising propulsion system for realizing a single-stage-to-orbit vehicle. The unique demands lead to the application of the compact heat exchangers, which can realize high thrust-to-weight ratio, sufficient specific impulse and high compression ratio. However, it is challenging to accurately manufacture the compact heat exchanger due to its extremely high heat dissipation capacity, remarkable compactness, superior adaptability and harsh operating condition. This review summarizes the precooling schemes of combined cycle propulsions and describes the demands and key issues in the fabrication of a compact heat exchanger for HPCCE. The investigation focuses on the application of various micromanufacturing methods of heat exchangers constructed from tubes of less than 1 mm in diameter and microchannels of less than 200 micrometers. Various micromanufacturing processes, which include microforming, micromachining, stereolithography, chemical etching, 3 D printing, joining and other advanced microfabricating processes, were reviewed. In addition, the technologies are compared in terms of dimensional tolerance, material compatibility, and process applicability. Furthermore, the boundaries of the micromanufacturing constraints are specified as references for the design of compact heat exchangers. Ultimately, the technological difficulties and development trends are discussed for the fabrication of compact heat exchangers for HPCCE.

A refined design method for precoolers with consideration of multi-parameter variations based on low-dimensional analysis

The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods.The latter are based upon assumptions that often reveal to be limited for precooler design.In this paper,a refined design method considering the variations of fluid thermophysical properties,flow area and thermal parameters distortion,was proposed to remediate their limitations.Firstly,the precooler was discretized into a fixed number of sub-microtubes based on a new discretization criterion.Next,in-house one-dimensional(1D)and two-dimensional(2D)segmented models were established for rapid thermal design and precooler rating with non-uniform airflow,respectively.The heat transfer experimental studies of supercritical hydrocarbon fuel were performed to verify the Jackson correlation for precooler design and the in-house models were validated against the reported data from open literature.On this basis,the proposed method was employed for the design analysis of hydrocarbon fuel precoolers for precooled-Turbine Based Combined Cycle(TBCC)engines.The results show that the local performance of precoolers is intrinsically impacted by the aforementioned three variations.In the case study,the local heat transfer performance is drastically affected by coolant flow transition.While the circumferential temperature distortion of airflow is weakened by heat transfer.With consideration of additional parameter variations,this novel method improves design accuracy and shortens the design time.