High-temperature fuel flow regulator valve repair, how to do? Jiangyin Oulei Si regulating valve repair plant, first you talk about the high-temperature fuel flow regulator valve repair characteristics of hypersonic ramjet is a ramjet engine, speed into the engine combustion chamber for the supersonic and fuel characteristics in supersonic temperature combustion. It is a new type of high temperature stamping technology as the core engine technology, countries in this area in the study, of which Russia and the United States in the forefront, and preliminary molding products come out. Ramjet combustion chamber, inlet, nozzle. Works for engine head-flow (air flow) first enters the inlet, the inlet part of the stream speed into pressure energy to complete the compression process. Stagnation to a certain speed of the airflow into the combustion chamber, and rapidly mixed with the injected fuel in the combustion is performed under conditions of equal pressure. The high-pressure, high-temperature combustion gas by the convergent - divergent nozzle accelerated ejected to produce thrust. The ramjet general applied to the flight Mach number is higher than the 6 aircraft, such as hypersonic cruise missiles, hypersonic aircraft and space plane.
In order to accurately control the flow to the engine airflow velocity and pressure, and adjusting the flow rate of the fuel into the combustion chamber, and its accurate release of heat, so the design in accordance with the need to allocate a large flow of fuel flow regulator valve, and plays a key role in the ramjet .
Based on Laval tubular high temperature valve port design is the Laval tube characteristics used in the design of the valve port, so as to achieve the purpose of accurate control of the flow through the valve port gas. This valve design is as follows:
(1) Spool poppet valve, Laval tube characteristics, the gas from the bottom of the cone valve into the outflow along the cone valve tip, the purpose of this control method is formed at the valve port Laval tubular structure, control of gas flow.
(2) of the spool with hydraulic power provided by the drive piston, can achieve the purpose of fast response.
1 structure and working principle
The spool with the form of a cone valve, the piston driven by the drive the tapered spool control valve opening in the loop, the fuel fluid through the the leftmost valve port into the main valve, and by a tapered valve body to control the flow size. The degree of opening of the spool is driven by a hydraulic servo valve drive piston to control.
The electro-hydraulic servo valve control to drive the piston rod and move around, so as to control the size of the main valve spool displacement, regulating the flow of fuel through the main valve port. Valve port design draws Laval tube characteristics and shape considerations, so that to meet the requirements of the valve port at the outlet gas stream of supersonic, but also achieve the purpose of the gas flow rate remains unchanged in the different pressure, improving high temperature characteristics of the valve. dedecms.com
2 Laval the tubular valve port mathematical model and design
Preval nozzle is a first contraction after the expansion of the pipeline. Its main features is specified Mach number supersonic flow in the pipe outlet. In the case of the same area ratio, the inlet total pressure and outlet anti-pressure ratio is not the same, show different flow state of the gas in the tube. The normal operating conditions of the Laval nozzle is: the pipe before and after the pressure ratio is greater than the critical value; adapt the outlet cross-sectional area of the minimum cross-sectional area ratio with a specified supersonic Mach number.
The flow characteristics of the Laval nozzle is: the same temperature, under the conditions of inlet pressure, the gas flow through the nozzle, i.e., only with the throat area and the exit area ratio. Such flow characteristics conducive to high temperatures for gas flow control, since within a certain range from before and after the impact of the pressure change, easy to achieve a stable flow. Laval pipe to work properly, the minimum cross-section at Mach number is a critical state, the stream parameter is the critical parameter, the operator relatively simple. Therefore, generally by calculating flows through the method of the minimum cross-section of the gas flow to determine the gas flow pipe by Laval. Accordingly, the Laval tube gas flow equation can be written as:
(1) Km - heat coefficient P0 * - the imports total gas pressure (Pa) T0 * - total inlet gas temperature (K) At - throat area (m2)
Can be seen from the formula, at a minimum cross section at a Mach number of a critical state, the gas flow only Laval tube only depends on the total pressure and total temperature and the minimum cross-section of the pipeline inlet gas.
P0 * for the import total pressure, to 10MPa. Inlet pressure P0 * = 10MPa, the outlet pressure Pe = 1MPa preliminary design.
(2) (3) λ - gas velocity coefficient further look-up table to determine the λ = 1.75, q (λ) = 0.4961
(4) q (λ) - gas relative density of the flow is considered, according to throat area ratio, and processing technology, determining the valve opening structure shown in Figure 4.
3 based on FLUENT valve port flow field simulation
Valve port flow field at using FUENT software simulation analysis of valve port flow characteristics and pressure and velocity distribution.
The specific simulation steps are as follows:
1) CAMBIT to build computational domain and specify the type of boundary conditions; completely symmetrical due to the shape of the valve port to simplify the calculation, it is in the process of simulation can take advantage of the two-dimensional graphics instead of the three-dimensional simulation mesh as shown in Figure 5.
2) Using the FLUENT solver.
In the calculation of the process fluid and the boundary conditions are as follows:
1, the fluid is entirely gaseous, compressible gas, nitrogen analog can be used in the experiment, therefore the ideal gas approximation simulation available.
2 spalart a Anmaras of turbulence model, this model is easy to convergence.
Valve inlet temperature, simulation using experimental conditions 600 ° C, the export 500 ℃.
4, the inlet and outlet, respectively, to the pressure inlet and pressure outlet boundary conditions, and the rest for the wall contact. The inlet pressure and the outlet pressure were changed to make the simulation results.
The 4 flow field simulation results
According to Laval tube modeling thinking, using the FLUENT software simulation of the design of the main valve port. Entrance to 10MPa, export SMpa, the valve port displacement when 8.Omm simulation results.
The fuel gas in the valve opening at the minimum sectional reach the speed of sound, after the gases continue to accelerate becomes supersonic. Figure 9, Figure 10 can be seen, stability is reached, the flow of gas in the valve inlet and the valve outlet flat. This is in line with the Laval tube characteristic flow regulation mechanism.
Constant inlet pressure of the valve port (10MPa), by changing the outlet pressure of the valve port, make a set of simulation results, obtained under different outlet pressure gas as shown in Figure 10 flow through the valve port. Similarly, when the outlet pressure of the valve port is maintained unchanged (1MPa), varying inlet pressure value, to obtain the flow results
Simulation results: the shape of the valve port is fixed, when the outlet pressure is less than a certain value (7MPa), inflow and outflow of the valve port of the gas flow and is independent of the outlet pressure, and only depends on the inlet pressure (10MPa). Instant, the traffic is only associated with the inlet total pressure (10MPa) and approximate linear relationship.
Changing the spool displacement x or changing the disc shape can be obtained similar to the simulation results, this longer discussed.
5 Conclusion
The comparison of simulation results with mathematical models can draw the following conclusions:
1) of the valve port of the high temperature valve Laval tube shape design scheme, when the valve opening is constant, before and after the pressure in a certain ratio range before and after passing through the valve port, the gas flow rate remains substantially constant, with the theoretical analysis the results match.
2) gas flow rate in the throat of the valve port velocity, further accelerated to a supersonic speed into the valve port, the mathematical properties of the simulation results with the Laval tube adapted.
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