CN112325334A

CN112325334A - Premixing fuel nozzle with isolating layer

Info

Publication number: CN112325334A
Application number: CN202011043486.9A
Authority: CN
Inventors: 丁珏; 杨小权; 翁培奋; 雷知迪
Original assignee: Shanghai Institute Of Applied Mathematics And Mechanics
Current assignee: Shanghai Institute Of Applied Mathematics And Mechanics
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2021-02-05

Abstract

The invention discloses a premixing fuel nozzle with an isolating layer, wherein a plurality of fuel nozzles are respectively arranged at an inlet of a combustion chamber of a rotary detonation engine, and a plurality of inert gas nozzles are arranged on two sides of each fuel nozzle. The invention can reduce the contact surface area of the premixed fuel and the high-temperature product by feeding the premixed fuel and the inert gas in a layered manner under the condition that the high-temperature combustion product exists in the detonation combustion chamber, thereby reducing the proportion of the fuel in the detonation combustion and improving the heat efficiency and the propulsion stability.

Description

Premixing fuel nozzle with isolating layer

Technical Field

The invention relates to a premix fuel nozzle with a barrier layer.

Background

In a rotary detonation combustor, the fuel should be organized to combust as much as possible in detonation form in order to meet the design objectives. However, at the interface of fresh fuel and detonation products, there is a deflagration combustion phenomenon, which has a thermal efficiency lower than that of the detonation of the isochoric combustion process, since the deflagration combustion behavior is close to that of the isobaric combustion process. Therefore, the fuel knocking phenomenon will lower the thermal efficiency of the engine. In particular, it is possible to induce a change in the propagation mode of the detonation waves, causing great instability of the thrust of the engine. By using inert gas to isolate fresh fuel from detonation products, the occurrence of deflagration phenomena can be effectively reduced. As such, a premix fuel nozzle with a barrier layer may improve overall stability and thermal efficiency.

The rotary detonation engine, also called continuous rotary detonation engine or rotary detonation engine, is a new type of detonation engine which is proposed in recent years for perfecting detonation propulsion technology. The working principle of a rotary detonation engine is based on the continuous propagation of a rotary detonation wave in a disk-like or annular cavity, the combustion chamber of which is usually a coaxial annular cavity, as shown in fig. 1-1 (a is the fuel, b is the detonation products, c is the combustion chamber outlet, d is the annular combustion chamber, e is the fuel supply outlet). 1-2, A is a rotating detonation wave propagating circumferentially against the air intake interface; b is oblique shock wave induced by detonation wave; g is the fresh fuel bed. The rotating detonation wave has no motion component propagating toward the outlet of the combustion chamber, and is therefore confined in the annular combustion chamber and rotates around the shaft. The detonation products expand along the axial direction and deviate from the wave-rear area of the guided shock wave, so that the synchronous injection of the fresh combustible gas is possible, the wave front of the detonation wave is always filled with unburned gas, and the continuous propagation of the detonation wave is further maintained. The high-pressure detonation product is ejected along the axial direction to generate thrust. Since the detonation wave continues to propagate in the combustion chamber, high velocity incoming flow and high frequency ignition are not required.

In fig. 1-2, the combustion chamber is filled with detonation products of high temperature and pressure, except for the region indicated by the fresh fuel G, which is affected by this and will undergo combustion, which takes the form of a deflagration, before the detonation wave sweeps over the fresh fuel. The premixed combustion is divided into two forms of deflagration and detonation, wherein the detonation process has rapid chemical reaction, is similar to an isochoric reaction process, and has the advantages of small entropy increase, high thermal cycle efficiency and the like. As the proportion of fuel within a detonation engine combustion chamber that reacts in a deflagration increases, the combustion chamber thermal cycle efficiency decreases.

One of the main mechanisms of loss of propulsion performance of a rotary detonation engine is that the propellant is prematurely consumed in the form of detonation before the detonation wave passes through, the early combustion of the fuel results in a reduction in engine specific impulse and may induce a shift in the mode of propagation of the detonation wave, which in turn results in severe fluctuations in the flow field. In order to improve the engine propulsion performance, it is necessary to suppress advanced combustion of fuel, and therefore a fuel stratified injection technique is proposed. The technology can effectively reduce the proportion of fuel consumed by deflagration phenomenon in the combustion chamber by isolating high-temperature detonation products which cause advanced combustion of the fuel, thereby improving the thermal cycle efficiency of the engine. Meanwhile, the inert gas used for protecting the fresh fuel can also play a role in cooling the flow field, and the temperature in the combustion chamber and at the outlet can be effectively reduced.

It can be seen that there is a desire to improve the thermal efficiency and stability of detonation engines. Such improved fuel nozzle designs should accommodate and/or eliminate the associated losses caused by detonation combustion. A reduction in the fuel detonation ratio should improve overall performance and efficiency.

Disclosure of Invention

One of the main mechanisms of loss of propulsion performance of a rotary detonation engine is that the propellant is prematurely consumed in the form of detonation before the detonation wave passes through, the early combustion of the fuel results in a reduction in engine specific impulse and may induce a shift in the mode of propagation of the detonation wave, which in turn results in severe fluctuations in the flow field. To improve engine propulsion performance, it is desirable to suppress pre-combustion of the fuel, and the present invention proposes a premix fuel nozzle with a barrier layer.

The invention can be realized by the following technical scheme:

a plurality of premixed fuel nozzles with isolation layers are arranged at the inlet of a combustion chamber of a rotary detonation engine respectively, and a plurality of inert gas nozzles are arranged on two sides of each fuel nozzle.

Further, the plurality of fuel nozzles are equally spaced and separated by the inert gas nozzle.

Further, the inert gas nozzle includes a central premix fuel passage, and a peripheral inert gas passage.

Further, the inert gas channel may be divided into several.

Further, the premix fuel passages and the inert gas passages include, but are not limited to, an equal straight type, a convergent type, a divergent type, or a convergent-divergent type.

Further, in the layout, the inert gas flowing in from the inert gas nozzle wraps the premixed fuel inside; functionally, the inert gas separates the fresh premixed fuel from the detonation products of the previous cycle, namely: the inert gas flowing in from the inert gas nozzle separates the premixed fuel at two sides.

Further, when the inert gas nozzle is opened, a fuel layered injection mode is adopted; a fuel gap injection mode when the inert gas nozzle is closed.

Advantageous effects

The invention can effectively reduce the proportion of fuel consumed by deflagration phenomenon in the combustion chamber by isolating high-temperature detonation products which cause advanced combustion of the fuel, thereby improving the thermal cycle efficiency of the engine. Meanwhile, the inert gas used for protecting the fresh fuel can also play a role in cooling the flow field, so that the temperature inside and at the outlet of the combustion chamber is effectively reduced, and the structure is simple and easy to realize.

Drawings

FIG. 1-1 is a schematic view of a combustion chamber configuration;

FIGS. 1-2 are schematic views of flow field configurations;

FIG. 2 is a schematic view of a fuel distribution in a flow field resulting from a premix fuel nozzle without a barrier layer;

FIG. 3 is a schematic view of a flow field fuel distribution resulting from a premix fuel nozzle with a barrier layer;

FIG. 4 is a top view of a premix fuel nozzle with a barrier layer;

FIG. 5 is a cross-sectional view A-A of a premix fuel nozzle with a barrier layer;

FIG. 6 is a graph of combustion chamber pressure versus time during a steady state operating phase;

FIG. 7(a) is a graph of hydrogen mass flow rate versus time;

FIG. 7(b) is a graph of combustion chamber thrust over time;

FIG. 7(c) is a graph of specific impulse over time based on fuel hydrogen;

FIG. 8 is an enlarged partial view of thrust oscillation;

FIG. 9 is a graph of average temperature at the combustion chamber interior and exit interface over time.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification.

Referring to fig. 3, 4 and 5, a plurality of premixed fuel nozzles with a separation layer according to the present invention are P fuel nozzles, which are respectively disposed at an inlet of a combustion chamber R of a rotary detonation engine, and a plurality of inert gas nozzles D are disposed at both sides of each fuel nozzle P (wherein fig. 2 is a schematic diagram of a fuel distribution in a flow field caused by the premixed fuel nozzles without the separation layer, fig. 3 is a schematic diagram of a fuel distribution in a flow field caused by the premixed fuel nozzles with the separation layer, and M is a contact surface of fuel and a high-temperature detonation product).

The inert gas nozzles D are added around the individual fuel nozzles P so that the fuel ejected from the fuel nozzles P is surrounded by the inert gas. Fig. 4 is a plan view of the nozzle, fig. 5 is a sectional plan view of the nozzle a-a, and the inert gas nozzle D includes: inert gas outlet interface 1, premixed fuel outlet interface 2, intermediate premixed fuel channel 4 and peripheral inert gas channel 3. In the layout, the inert gas flowing into the inert gas nozzle D wraps the premixed fuel inside; functionally, the inert gas separates the fresh premixed fuel from the detonation products of the previous cycle, i.e., the inert gas flowing in from the inert gas nozzle D separates the premixed fuel on both sides. In FIG. 5, the fuel passages and the inert gas passages are all of an equal straight configuration, and the fuel passages deliver premixed fuel. In practice, the fuel passages may be replaced by multiple nozzles, even with separate oxidant and reductant passages (i.e., non-premixed fuel). Further, the configuration of the channel may be changed to a contractible, expandable or contractible-expandable type as necessary. The inert gas passage may be one or a plurality of passages arranged around the fuel passage.

By adopting the technical scheme, the invention can reduce the contact surface area of the premixed fuel and the high-temperature product by feeding the premixed fuel and the inert gas in a layered manner under the condition that the high-temperature combustion product exists in the detonation combustion chamber, thereby reducing the proportion of the fuel in the detonation combustion and improving the heat efficiency and the propulsion stability.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Based on the concept of the premixed fuel nozzle with the isolating layer (also called layered injection), the physical model of the combustion chamber used for design comparison is shown in FIG. 3, wherein the axial length of the combustion chamber is 100mm, the inner diameter is 45mm, the outer diameter is 50mm, and the width of the combustion chamber is 5 mm. The 50 fuel nozzles are equally spaced at the inlet interface and are separated by inert gas nozzles. When the inert gas nozzle is opened, the fuel is injected in a layered mode. When the inert gas nozzle is closed (set as a glide wall), the fuel gap injection mode is used. The average width of the fuel nozzles was 4mm and the average width of the inert gas nozzles was 2 mm. The fuel nozzle is connected with an air storage tank with constant total pressure through a contraction type spray pipe to provide premixed fuel for the combustion chamber. The total injection pressure is 1MPa, and the total temperature is 600K. The fuel nozzle injects premixed gas of hydrogen, oxygen and nitrogen, and the molar ratio is 2: 1: 7.3. argon is used as the inert gas, and the total injection pressure and the total temperature of the argon are the same as those of the fuel. The engine is started by adopting a direct detonation method, and the number of initial detonation points is 1.

The process from ignition start to smooth running of the engine in the two injection modes is compared and researched. In both injection modes, the engine stably operates in the single-wave propagation mode, and the pressure-time curve of the combustion chamber in the stable stage is shown in FIG. 6. Fluctuations in the pressure within the combustion chamber may be used to characterize the stability of the engine. And (4) counting the peak pressure of the stable stage, wherein the average value of the peak pressure in the layered injection mode is 3.94MPa, the maximum offset is 0.34MPa, and the fluctuation percentage is 8.6%. The peak pressure in the spaced injection mode had an average of 3.07MPa, a maximum offset of 0.53MPa, and a percent fluctuation of 17.3%. Thus, the stratified injection mode may reduce instability caused by the fuel injection process and the detonation wave propagation process coupling with each other.

Thrust and specific impulse are important indexes for evaluating the propelling performance of the engine. Fig. 7(a), (b), (c) show the engine performance parameters over time for two injection modes. As can be seen from the figure, the engine generated 496.2N thrust at the interval injection and the engine thrust at the stratified injection was slightly reduced to 493.6N. The average mass flow of hydrogen in the stratified injection mode was 14.35g/s, and the specific impulse based on fuel hydrogen was 3510.2 s. The average mass flow of hydrogen in the split injection mode was 16.80g/s and the specific impulse based on fuel hydrogen was 3013.8 s. The stratified injection mode is improved by 16.5 percent compared with the impact.

FIG. 8 is a partial enlarged view of the steady-state thrust oscillation showing that the maximum magnitude of the thrust force from its mean value is about 17.3% in the spaced jet mode; in the stratified injection mode, the maximum amplitude of the thrust force from its mean value is about 8.3%. Therefore, the amplitude of the thrust fluctuation of the stratified injection mode is smaller.

The increased temperature of the rotating detonation combustor will increase the high temperature requirements of the materials of manufacture and also increase the pressure on the cooling system, which is detrimental to the long-term operation of the engine. The average temperature at the interface between the interior of the combustion chamber and the outlet over time is shown in FIG. 9. As can be seen from the graph, the average temperatures inside and at the outlet of the combustion chamber after the formation of the rotating detonation wave hardly change with time. During the interval injection of fuel, the average temperature of the inner part of the combustion chamber is 1648.3K, and the average temperature of the outlet of the combustion chamber is 1710.1K. When stratified injection is used, the average temperature inside the combustion chamber is 1310.2K, and the average temperature at the outlet of the combustion chamber is 1382.7K. The use of stratified injection reduced the average temperature inside the combustion chamber by 338.1K, with a 20.5% reduction. The average outlet temperature was reduced by 327.4K, which was a 19.1% reduction.

In summary, after the premixed fuel nozzle with the isolating layer is adopted, the advanced combustion rate of the fuel is reduced from 33% to 5%, and the specific impulse of the engine is increased from 3013.8s to 3510.2 s. After deducting the thrust boost caused by the additional argon injection, the specific impulse was 3147.3s, which is a 4.4% boost. Indicating that the stratified injection mode improves engine propulsion efficiency. Analysis of the pressure curve oscillation process shows that the layered injection mode is more favorable for smooth establishment of the rotating detonation wave, and instability caused by mutual coupling of the fuel injection process and the detonation wave propagation process can be reduced. The research on the oscillation process of the thrust curve shows that the thrust fluctuation amplitude of the layered injection mode is smaller, and the propulsion performance is more stable. Studies of the average combustor temperature and the average exit temperature have shown that the use of stratified injection techniques results in significant reductions in combustion product temperatures. Compared with the average temperature of the engine outlet when the engine is not used, the average temperature of the engine outlet is reduced by 327.4K and is reduced by 19.1 percent. Therefore, the layered injection technology is beneficial to controlling the temperature of the combustion chamber, and brings convenience for additionally installing equipment such as a turbine and the like in the later period.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. The utility model provides a premix fuel nozzle with isolation layer which characterized in that, fuel nozzle is a plurality of, sets up respectively in the entrance of rotatory detonation engine combustion chamber, and every fuel nozzle both sides are equipped with a plurality of inert gas nozzle.

2. The premix fuel nozzle with the barrier layer as in claim 1, wherein the plurality of fuel nozzles are equally spaced and separated by the inert gas nozzle.

3. The premix fuel nozzle with the barrier layer as in claim 1, wherein the inert gas nozzle comprises a central premix fuel passage, and a peripheral inert gas passage.

4. The premix fuel nozzle with a barrier layer as in claim 3, wherein the inert gas passage is divisible into a number.

5. The premix fuel nozzle with the barrier layer of claim 4, wherein the premix fuel passage and the inert gas passage comprise, but are not limited to, an iso-straight type, a convergent type, a divergent type, or a convergent-divergent type.

6. The premix fuel nozzle with a barrier layer as in any of claims 1-5, wherein in the layout, the inert gas flowing in from the inert gas nozzle wraps the premix fuel inside; functionally, the inert gas separates the fresh premixed fuel from the detonation products of the previous cycle, namely: the inert gas flowing in from the inert gas nozzle separates the premixed fuel at two sides.

7. The premix fuel nozzle with a barrier layer as in any of claims 1-5, wherein when said inert gas nozzle is open, a fuel stratified injection mode; a fuel gap injection mode when the inert gas nozzle is closed.