Simulation and verification of a non-equilibrium thermodynamic model for a steam catapult’s steam accumulator

et al. 2020

Mechanics & Industry

In view of the shortcomings of the existing hot spinning process technology of the accumulator shell, a method for optimizing the multi-spinning process parameters is proposed. The Johnson-Cook constitutive model of the accumulator shell material – 34CrMo4 alloy steel − was established with its parameters obtained experimentally. The finite element simulation was carried out for the hot spinning and closing process. Based on which, three parameters with the greatest influence on the spinning formation were studied: spinning temperature, spindle speed and friction coefficient. Combined with the central composite test, the response surface model and the mapping relationship between the three parameters and the maximum mises stress as well as the maximum wall thickness increment of the shell were established. The Pareto optimized solution set was obtained through multi-objective optimization. Under the condition of not affecting product quality, the optimized solution with low spinning temperature and high spindle speed is selected to reduce energy loss and improve work efficiency. The results indicate that the optimized process is experimentally verified to reduce the process temperature by nearly 30 °C, and the efficiency is increased by 25%.

Section: Introductionmentioning

confidence: 99%

Study on optimization of thermal spinning process of accumulator shell

et al. 2020

Mechanics & Industry

“…The steam-powered catapult's [1][2][3] wet steam accumulator is similar to steam accumulators [4] which are used in industry. The wet steam accumulator is a core device in the steam-powered catapult, and it can provide the catapult energy for catapult launches of carrier-based aircraft.…”

Section: Introductionmentioning

confidence: 99%

“…For example, Slavin [2] did research on the dry accumulator and wet steam accumulator. In order to overcome the defects of the equilibrium wet steam accumulator model, the non-equilibrium thermodynamic models were developed [3,5]. Lucas [6] established catapult criteria for carrier-based aircraft basing on catapult tow force functions, and the forcing functions [7] are presented as catapult force versus catapult stroke.…”

Section: Introductionmentioning

confidence: 99%

Multi-Parameter Optimization for the Wet Steam Accumulator of a Steam-Powered Catapult

Yang

et al. 2019

Energies

Selecting the optimal parameters for wet steam accumulator of steam-powered catapult is an important task, due to launching safety. There is no literature on the topic of the parameters optimization for wet steam accumulator of steam-powered catapult. The genetic algorithm (GA) was used to determine the optimal wet steam accumulator in this article. The sink-off-the-bow (SOB), angle of attack and rate of climb were used to create the objective function. The multi-objective optimization can be converted to single-objective optimization, which is subject to angle of attack and rate of climb. Moreover, the simulation model of the steam catapult system was built by creating a thermodynamics model of steam-powered catapult, a mathematical model of traction release device, a statics model of tensioning, a statics model of full takeoff power, a mathematical model of catapult force build-up with holdback, a model of release, a dynamics model of power stroke, a dynamics model of free deck run and a dynamics model of fly away. Finally, the optimal combination of the wet steam accumulator was obtained via numerical simulation. The GA method can effectively find the optimal parameters of wet steam accumulator, and its optimized parameters can increase the safety of catapult launch process.Steam-powered catapult launch system for carrier-based aircraft is mainly made up of steam-powered catapult, the traction release device and aircraft, and its simplified model is shown in Figure 1. A steam-powered catapult consists of a wet steam accumulator, a launch valve, two cylinders, two pistons, a shuttle, a water brake and a retraction system. The traction release device mainly consists of a launch bar and holdback bar.

“…The main role of the launch bar is to transmit the catapult force [1][2][3] to the aircraft, allowing the aircraft to accelerate while taxiing before reaching a safe catapult end airspeed within the limited length deck. At the end of the catapult [4][5][6], the launch bar pops out of the shuttle. The launch bar, which is in the air, needs a mechanism for controlling and overcoming other damping torque.…”

Section: Introductionmentioning

confidence: 99%

Launch Bar Dynamics Character Analysis of Carrier-Based Aircraft Catapult Launch

Yang

et al. 2019

Applied Sciences

The launch bar is a unique device of carrier-based aircraft, which is connected to the nose gear and shuttle. In order to avoid the launch bar striking the flight deck after the launch bar pops out of the shuttle, it is very important to research the dynamics performance of the launch bar. This paper establishes a staged mathematical model of catapult launch including the launch bar, a steam-powered catapult, a holdback bar, and a carrier-based aircraft. This article studied the effect of the mass of the launch bar, restoring moment of the launch bar, and center of gravity position of the launch bar on the dynamics performance of the launch bar. The results showed the following: (1) we could reduce the risk collision of the launch bar and deck by reducing the mass of the launch bar, increasing the restoring moment, and shifting the center of gravity position of the launch bar; (2) under the working condition of this article, we changed the center of gravity position of the launch bar to control the sink of the launch bar end, having the most obvious effect, and we reduced the mass of the launch bar, having the least effect on controlling the sink of the launch bar end; however, reducing the mass of the launch bar could also greatly reduce the risk collision of the launch bar and deck; (3) in order to avoid the launch bar striking the flight deck, the restoring moment of the launch bar must overcome the sum of other moments. The study results can give a theoretical reference for designing and testing the launch bars of carrier-based aircraft. It can also give a theoretical reference for designing and testing the launch bar’s driving mechanisms.