CN104612834A - Spiral tube heat exchanger suitable for aviation engine - Google Patents

Abstract

The invention discloses a spiral tube heat exchanger suitable for an aero-engine, which comprises a mixing chamber and a stainless steel tube bundle; the mixing chamber includes a primary mixing chamber and a secondary mixing chamber; the primary mixing chamber includes two inline circular tubes , two Z-shaped elbows; the secondary mixing chamber includes N round tubes; two ends of a part of the round tubes are respectively connected to two straight-shaped round pipes, and one end of the straight-shaped round pipes is closed; the two ends of the other part of the round pipes are respectively connected The upper ends of the two Z-shaped elbows, one end of the Z-shaped elbow is closed; the stainless steel tube bundle includes several stainless steel tubes, the stainless steel tubes are spiral tubes, and the stainless steel tubes are arranged radially in a circular ring to form a stainless steel tube bundle; the two parts of the circular tubes correspond up and down , are connected through stainless steel tubes; the heat exchange efficiency of the present invention is greatly improved compared with the heat exchange efficiency of common civilian tube bundle heat exchangers, and the spiral tube of the present invention can absorb the vibration of the engine itself and the impact of the forced vibration during the actual operation of the aero-engine. Damage caused by heat exchanger structure and solder joints.

Description

A spiral tube heat exchanger suitable for aero-engine

technical field

The invention relates to a helical tube heat exchanger suitable for aero-engines, belonging to the technical field of thermal protection for aerospace vehicles.

Background technique

With the continuous development of aero turbine engines, the performance requirements are also increasing. From a thermodynamic point of view, the improvement of engine performance is mainly achieved by increasing the pressure ratio of the compressor and the temperature before the turbine. On the one hand, the increase in the boost ratio of the compressor causes the temperature of the high-temperature turbine cooling air drawn from the subsequent stage to rise, and the cooling quality to decline. Under the premise of ensuring the cooling efficiency, it is necessary to increase the cooling air flow rate, which has caused a negative impact on the efficiency of the engine as a whole. On the other hand, when the temperature resistance of high-temperature materials cannot be greatly improved, the increase in the temperature before the turbine puts forward higher requirements for the cooling of the hot-end parts of the engine. On the other hand, with the continuous improvement of the performance of aero-engines in the future, the temperature in front of the turbine is still rising. It is expected to reach 2200K in 2020, and the pressure ratio will increase to above 30. At this time, the temperature of the bleed air at the compressor outlet may reach 900K. . In order to meet the pressure requirements of the cooling gas used in aero-engines, the cooling gas generally needs to be extracted from the high-pressure compressor, and the air is directly drawn from the compressor outlet to cool the hot-end components (when the boost ratio is 30, the temperature of the compressor outlet gas will reach 900K ), it is bound to be difficult to achieve the desired effect, which brings great challenges to the stable operation of the hot end components of the aero-engine.

Studies have shown that the fuel itself has a great heat-absorbing capacity. In addition to its own physical heat sink, it can also absorb heat through its chemical reaction. Taking the US JP8 military aviation kerosene as an example, as shown in Figure 1, 1kg of this aviation kerosene is heated at room temperature. 298K is heated to 800K, and the heat absorption is as high as 1600kJ. Therefore, scholars have proposed CCA (cooled cooling air) technology, as shown in Figure 2, by installing a heat exchanger in the aero-engine, using the aircraft's own fuel to cool the cooling air, reducing the temperature of the cooling air, and increasing the temperature of the cooling air. cooling quality. As a general-purpose equipment for heat exchange, heat exchangers have a variety of internal structures. From the perspective of civil heat exchangers, shell-and-tube heat exchangers are applicable to a wide range of temperatures and pressures and are the most widely used. However, due to The compactness of the structure is low, and the general civil heat exchanger only obtains a heat exchange area of about 5m ² under the condition of a self-weight of 200kg, and it is difficult to apply it to an aero-engine. However, spiral plate and plate heat exchangers, which are typical representatives of compact heat exchangers, have a small application temperature and pressure range, and cannot meet the requirements of high temperature, high pressure and weight control in aero-engines at the same time, making the traditional heat exchanger structure in There are great difficulties in the direct application in aviation engine.

In the practical application of aero-engines, there are extremely strict requirements on the structural weight, because the weight will directly determine the thrust-to-weight ratio of the engine. In addition, in aerospace applications, there are strong requirements for the conformal characteristics of the heat exchanger. The so-called follow-up means that the physical structure can be adjusted according to the environment and space, so as to facilitate installation, disassembly and cleaning. Traditional plate-fin heat exchangers and shell-and-tube heat exchangers do not have this feature.

In the existing engine structure, by adding an air/air heat exchanger (Russian 31-F) in the outer duct, the engine outer duct air is used to cool the cooling air, and a certain effect has been achieved, but its cooling capacity is small, and The pressure loss of the external air is caused, which affects the overall performance of the engine.

Contents of the invention

The purpose of the present invention is to solve the above problems, and propose a high-compact heat exchanger with spiral tube bundle structure, which is arranged in the annular channel outside the engine combustion chamber, without involving the adjustment of the overall structure and aerodynamic characteristics of the engine. Optimizing the cooling quality of aero-engine cooling air. The invention utilizes the self-contained fuel of the aero-engine as a cold source to exchange heat with the turbine cooling gas, thereby reducing the temperature of the turbine cooling air and improving the cooling efficiency of the cooling air. At the same time, it enhances the fuel atomization effect, improves the combustion efficiency of the combustion chamber, and due to the substantial increase in its enthalpy, it can effectively increase the outlet temperature of the combustion chamber under the premise of a certain fuel-gas ratio in the combustion chamber.

A spiral tube heat exchanger suitable for aero-engines, comprising a mixing chamber and a stainless steel tube bundle;

The mixing chamber includes a primary mixing chamber and a secondary mixing chamber;

The primary mixing chamber includes two straight round tubes and two Z-shaped elbows;

The secondary mixing chamber includes N circular tubes;

The two ends of a part of the round tubes are respectively connected with two in-line round tubes, and one end of the in-line round tubes is closed;

The two ends of the other part of the circular pipe are respectively connected to the upper ends of the two Z-shaped elbows, and one end of the Z-shaped elbow is closed;

The stainless steel tube bundle includes several stainless steel tubes, the stainless steel tubes are spiral tubes, the stainless steel tubes are arranged radially in a circular ring to form a stainless steel tube bundle, and the arrangement between the spiral tubes is a cross arrangement;

The two parts of the circular tubes correspond up and down, and are connected through stainless steel tubes;

The fuel enters through the fuel inlet at one end of the straight pipe, passes through the primary mixing chamber, enters the secondary mixing chamber at the bottom, enters the secondary mixing chamber at the top through the stainless steel tube bundle, then enters the Z-shaped elbow, and passes through the Z-shaped elbow The fuel outlet at one end is discharged, and the high-temperature air flows from the top of the heat exchanger to the bottom of the heat exchanger, and the heat exchanger cools down the high-temperature air.

The advantages of the present invention are:

(1) The fuel itself has a great heat-absorbing capacity, in addition to its own physical heat sink, it can also absorb heat through its chemical reaction;

(2) The heat exchange efficiency of the heat exchanger designed with structural parameters of the present invention is greatly improved compared with the heat exchange efficiency of common civilian tube bundle heat exchangers, and the structural design of the present invention is compact, and can be completely embedded in the inner ring of the combustion chamber, and A heat exchange area of ^10m2 is obtained under the condition that the total weight does not exceed 15kg, making the application of heat exchangers in aero-engines a reality;

(3) Because what the present invention adopts is a helical tube, its unique flexible feature can absorb the damage caused by the engine's own vibration and forced vibration to the heat exchanger structure and solder joints in the actual operation of the aero-engine;

(4) Adopting the heat exchanger of the present invention can adapt to the requirements of the annular cavity structure of the aero-engine, so that the structure of the engine itself does not need to be changed, and can be applied on high-performance aero-engines, and can also be directly applied on existing engines Extend the life of the existing engine without changing the structure;

Description of drawings

Fig. 1 is the heat sink of JP-8 aviation kerosene used by the U.S. military;

Figure 2 is a schematic diagram of the CCA technology system;

Fig. 3 is a schematic diagram of the installation position of the heat exchanger of the present invention on an aero-engine

Fig. 4 is a schematic diagram of a heat exchanger unit of the present invention;

Fig. 5 is a schematic diagram of the arrangement of the spiral tubes of the heat exchanger of the present invention;

Fig. 6 is a schematic diagram of a spiral tube of a heat exchanger of the present invention;

Fig. 7 is a schematic diagram of the counterbore of the boss of the secondary mixing chamber of the present invention.

Detailed ways

The present invention will be further described in detail with reference to the accompanying drawings and embodiments.

The present invention is a spiral tube heat exchanger suitable for aero-engines. As shown in Figure 4, the heat exchanger includes a mixing chamber at the inlet and outlet and stainless steel tube bundles arranged radially in a circular ring. The stainless steel tube bundle is composed of a diameter of about 2- 3mm, wall thickness 0.2-0.3mm stainless steel tubes are arranged in a circular radial arrangement, in order to ensure that the parameters such as fluid pressure and temperature in each heat exchange tube are basically consistent, a circular mixing chamber is designed for the inlet and outlet of the heat exchange tube; working When the temperature is higher, the air with a higher temperature flows through the heat exchanger tube bundle and conducts convective heat exchange with the outer wall of the heat exchange tube. Through the heat conduction of the heat exchange tube and the convective heat exchange between the inner wall of the heat exchange tube and the aviation fuel, the air transfers heat to the inside Aero-engine fuel with a lower temperature, so as to realize the cooling of the engine cooling air.

As shown in Figure 5, the single heat exchange tube is in the form of a spiral tube with a pitch of 7 mm and a spiral diameter of 20 mm. The inlet and outlet of the heat exchange tube have straight sections with a length of 5 mm, which is convenient for brazing with the secondary mixing chamber. , the adjacent helical tubes are left-handed helical tubes and right-handed helical tubes respectively. In order to make the structure of the heat exchanger compact, the helical tubes of each row of helical tube bundles are arranged in a cross, that is, the left-handed helical tubes are inserted into the right-handed helical tubes from the side. Between the pitch gaps of the tubes, they are arranged in descending order, as shown in Figure 5. As shown in Figure 4, the mixing chamber of the heat exchanger is divided into a primary mixing chamber and a secondary mixing chamber. The two thick round tubes at the inlet and outlet are used as the primary mixing chamber, and N The slightly thinner round tube is used as the secondary mixing chamber (N is determined according to the demand), and the stainless steel spiral tube of the heat exchanger body in the middle is connected with the fine mixing chamber. The diameter of the primary mixing chamber is two or three times the diameter of the secondary mixing chamber, and the diameter of the secondary mixing chamber is two or three times the diameter of the stainless steel spiral pipe. The diameter is a straight tube with small holes on the side. Both the mixing chamber and the spiral tube are connected by brazing. In addition, the reason why two thick mixing chambers are welded at the inlet and outlet respectively, and the oil inlet method is adopted at both ends is to make the distribution of fuel more even, and the outlet first-stage mixing chamber is made into a Z-shaped elbow to make it compatible with the inlet first-stage mixing chamber. At the same level, easy to install. The aviation fuel is first divided into the secondary mixing chamber through the primary mixing chamber, and then further divided into each spiral tube to participate in cooling air, and finally the fuel is collected together and transported to the combustion chamber through the same mixing chamber for combustion. The connection between the spiral pipe and the mixing chamber in the present invention adopts brazing technology. Considering that the brazing material may flow into the spiral pipe to block the pipe during the brazing process, the structure of the fine oil collecting pipe is specially improved, and the boss counterbore is added. structure, as shown in Figure 6. After the unit body is processed, it needs to be pressed to check whether there is any air leakage; moreover, in order to check whether the unit body is blocked, hot water is passed through the main oil collection pipe at one end, and the blockage is detected by infrared thermal imager observation Condition.

According to the principle of heat transfer, under the same conditions, since the fluid flows in the curved flow that alternately shrinks and expands between the tubes in the fork row, the flow disturbance is more severe than that in the parallel row, and the heat transfer is generally stronger than that in the straight row. For the space and quality requirements of the heat exchanger, the heat exchange tubes are arranged in a fork row; the average temperature and pressure of the countercurrent flow is the largest, and the average temperature and pressure of the downstream flow is the smallest. The countercurrent arrangement is adopted, that is, the flow direction of aviation fuel and air is opposite.

As shown in Figure 3, the heat exchanger can be installed before the inlet of the combustion chamber and can be embedded in the combustion chamber. After exchanging heat with cooling air, the temperature of aviation fuel can be increased from 400K to 750K. Under the pressure of 5MPa in the pipeline of the aeroengine, the aviation fuel will reach a supercritical state. Under supercritical conditions, the atomization and combustion performance of kerosene will be greatly improved. Compared with traditional combustion chambers, the use of supercritical combustion chambers is very conducive to fuel atomization.

Table 1 is based on the parameters of a certain type of engine, and the preliminary parameter design is carried out for the shell-and-tube air/oil heat exchanger. After calculation and experimental verification, it is shown that the engine cooling air temperature can be reduced from 900K to 700K by using the air-oil heat exchanger At the same time, the aviation fuel at the inlet of the combustion chamber is heated from 400K to 750K, and the total weight of the air-oil heat exchanger does not exceed 15kg, which achieves the expected goal.

Table 1 Design parameters of a heat exchanger structural part

name design structure Heat exchanger type shell and tube Heat Exchange Tube Shape spiral tube Arrangement of tube rows Fork row heat exchanger flow countercurrent Heat exchange tube outer diameter mm 2.6 Heat exchange tube wall thickness mm 0.3 Helix diameter of spiral tube mm 20 Spiral pipe pitch mm 7 Heat exchange tube spacing S1,mm 10

It is worth mentioning that, based on the design concept of the present invention, the shape of the heat exchanger may not be limited by the disclosure of the present invention, and other structures are within the protection scope of the present invention.

Claims (1)

1. be applicable to a spiral tube heat exchanger for aeroengine, comprise mixing chamber and stainless steel tube bank;

Mixing chamber comprises one-level mixing chamber and secondary mixing chamber;

One-level mixing chamber comprises two yi word pattern pipes, two zigzag bend pipes;

Secondary mixing chamber comprises N root pipe;

Part pipe two ends UNICOM's two yi word pattern pipes respectively, one end of yi word pattern pipe is closed;

The upper end of another part pipe two ends difference UNICOM two zigzag bend pipes, one end of zigzag bend pipe is closed;

Stainless steel tube bank comprises several Stainless Steel Tubes, and Stainless Steel Tube is volute, and Stainless Steel Tube is that annulus radiate arranges the tube bank of composition stainless steel, adopts cross arrangement between volute;

Two-part pipe is corresponding up and down, between be communicated with by Stainless Steel Tube;

Fuel oil is entered by the fuel inlet of yi word pattern pipe one end, through one-level mixing chamber, enter the secondary mixing chamber of bottom, the secondary mixing chamber at top is entered by stainless steel tube bank, then zigzag bend pipe is entered, discharged by the fuel outlet of zigzag bend pipe one end, high temperature air is from heat exchanger overhead stream to exchanger base, and heat exchanger is lowered the temperature to high temperature air.