Guobiao Cai

Optimization of System Parameters for Liquid Rocket Engines with Gas-Generator Cycles

System design of liquid rocket engines must consider engine performance, weight, cost, and reliability requirements. A general design optimization framework has been developed in this paper to select the best system parameters for liquid rocket engines with gas-generator cycles. The object is to maximize the specific impulse and vacuum thrust-to-weight ratio of the engine with given system requirements and design assumptions by changing thrust-chamber pressure and mixture ratio. The system analysis, along with the engine weight estimation, is based on a modular scheme. Multidisciplinary design optimization formulations including multidisciplinary feasible and collaborative optimization are used, evaluated, and compared during the optimization process. Several techniques of multi-objective processing are also used to identify the Pareto frontier and the optimal compromise solutions. A proposed cryogenic-propellant engine using liquid oxygen and hydrogen with a gas-generator cycle is studied as a specific example. Moreover, uncertainties in the engine operation, such as thrust-chamber pressure and mixture ratio, are taken into account as random variables in the reliability-based optimization. Results are presented to illustrate the tradeoff between the engine performance and reliability requirements.

Multi-field coupling dynamic modeling and simulation of turbine test rig gas system

Abstract On the basis of early research on the 38-component system, this paper extends the established finite volume model to the multi-field coupling numerical system which can describe flow, heat transfer, combustion and rotation, and conducts, based on the experiment, dynamic modeling and simulation research on the turbine test rig gas system which includes turbine and load. The comparison among the simulation results, test data and early simulation results indicates the 42-component system established by this paper has made improvements against many weaknesses of the Previous simulation in an all-round way. Accordingly, it can be concluded that the case setting and algorithm improvement are effective. It is also found that the modeling of module with chemical reaction, the spool throttling modeling of various regulator valves, the modeling of the turbine characteristics and the modeling of wall heat transfer are four key factors which affect simulation accuracy, and that the coupling modeling of flow and combustion is the key factor which affects simulation stability.

Generic Optimization of System Parameters for Liquid Rocket Engine with Gas Generator Cycle

Generic simulation and optimization software of system parameters for the engine with gas generator cycle was developed to design and optimize rocket engines of different structural forms. For this paper, the engine with gas generator cycle was decomposed into several principal components, such as the thruster chamber, turbopumps, and gas generators. Numerical simulation codes were developed for each component and the system. According to different relationships between the components, these modular codes could be integrated arbitrarily. Chemical equilibrium analysis for the bipropellants types in the system had been built into the simulation model. A generic optimization procedure of system parameters for the engine with gas generator cycle was developed to maximize the engine specific impulse and the thrust to weight ratio. The Multidisciplinary Design Optimization (MDO) approaches such as Multidisciplinary Feasible (MDF) method and Collaborative Optimization (CO) method were employed during the optimization process. Several methods of multi-objective processing were also investigated for the design of a particular hydrogen- oxygen rocket engine to obtain the Pareto frontier as well as the relative optimal solutions. In addition, uncertainties in the engine operation were considered. Results of reliability - based optimization presented illustrate the tradeoff between the engine performance and the design reliability.

Development of a coupled NS-DSMC method for the simulation of plume impingement effects of space thrusters

A coupled NS-DSMC method possessing adapted-interface and two-way coupling features is studied to simulate the plume impingement effects of space thrusters. The continuum-rarefied interface is determined by combining KnGL and Ptne continuum breakdown parameters. State-based coupling scheme is adopted to transfer information between continuum and particle solvers, and an overlapping grid technique is investigated to combine structured-grid NS code and Cartesian-grid DSMC code to form the coupled solver. Flow problem of a conical thruster plume impinging on a cone surface is simulated using the coupled solver, and the simulation result is compared with experimental data, which proves the validity of the proposed method. Plume flow while the ascent stage of lunar module lifting off in lunar environment is also computed by using the present coupled NS-DSMC method to demonstrate its capability. The whole flow field from combustion chamber to the vacuum environment is obtained, and the result reveals that special attention should be paid to the plume aerodynamic force at the early stage of launching process.

Modeling of Lunar Dust Spray Using the DSMC method

To study the interaction of nozzle plume and lunar dust, the plume‐dust two‐phase flow simulation is implemented on the self‐developed DSMC workstation. The momentum and energy transfer to lunar dust particle from the rarefied gas flow was computed. Particle‐particle collision is considered as hard sphere collision. The dust particles are accelerated by the gas and a lunar crater is formed.