Engine configuration using liquid hydrogen as coolant and fuel and overall design method

Abstract

The invention discloses an engine configuration using liquid hydrogen as a coolant and fuel and an overall design method, and relates to the field of aero-engines, and the engine configuration comprises an air inlet channel, a fan, a precooler, an air compressor, a main combustion chamber, a high-pressure turbine, a low-pressure turbine, a mixing chamber, an afterburner and an exhaust nozzle. Only the inner culvert airflow is cooled, on the basis of solving the difficulty of rotation limitation under the high Mach number working condition of the core engine, the problem of cooling capacity waste generated by precooling the outer culvert airflow is avoided, and the liquid hydrogen amount depends on the combustion amount needed by the main combustion chamber and the afterburner; therefore, the waste problem caused by the fact that the amount of liquid hydrogen needed by pre-cooling is larger than the amount of liquid hydrogen needed by combustion is avoided. According to the overall design of the engine, from the angle of flight / intake / launch integration, the size and performance parameters of an engine body are determined in a ground state based on the take-off task requirement of an aircraft, the size of an intake and exhaust system is determined in a cruise state based on the cruise task requirement of the aircraft, and a control rule is determined by the engine demand flow and the intake passage capture flow.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aero-engines, in particular to an aero-engine using liquid hydrogen as coolant and fuel. BACKGROUND

[0002] With the continuous development of aerospace technology, it is urgent to greatly improve the maximum flight Mach number of the aircraft while ensuring the economic performance in both civil and military aspects. At present, the aero turbine engine is still the main aviation power at present and in the future for a long period of time, but when the speed of the aircraft is greater than Ma2.5, the engine will face the problem of excessively high inlet temperature, resulting in low engine conversion speed, reduced engine work capacity and thrust, and difficulty in further accelerating the aircraft, thereby limiting the further improvement of the engine performance.

[0003] In order to further expand the working speed range of the turbine engine, the air intake pre-cooling technology using liquid hydrogen as coolant becomes a feasible technical route. Liquid hydrogen has high fuel heat value and high physical heat sink, and can be used as fuel and coolant, which is an ideal working medium for fuel heat exchange pre-cooling. For the turbine engine, hydrogen fuel also has many advantages such as good starting performance, less fuel consumption, and large unit thrust / power.

[0004] However, the traditional hydrogen pre-cooling technology generally cools all the incoming flow to ensure the reliable operation of the engine and expand the working range. Such an advantage is simple and reliable, but cooling all the incoming flow consumes a large amount of liquid hydrogen, resulting in that the amount of liquid hydrogen required for pre-cooling is greater than the amount of liquid hydrogen required for combustion, thereby causing fuel waste. For the mixed exhaust turbofan, cooling all the incoming flow means cooling the outer bypass flow, resulting in waste of cold energy.

[0005] Therefore, the control of the pre-cooling amount of the hydrogen pre-cooling technology needs to consider the fuel demand of the engine and the cold energy distribution of the engine. Therefore, the present application proposes a mixed exhaust turbofan engine using liquid hydrogen as a pre-cooling agent to pre-cool only the inner bypass flow, and only uses the hydrogen required for combustion of the engine as a pre-cooling agent, thereby realizing the balance of the pre-cooling and combustion hydrogen flow. SUMMARY

[0006] The purpose of the present application is to solve the above-mentioned problems in the prior art, provide an aero-engine using liquid hydrogen as coolant and fuel, and a general design method, pre-cool only the inner bypass flow to avoid cold energy loss and fuel waste, quickly complete the engine general design parameter calculation, simplify the engine design process, and improve the wide speed range working performance of the engine.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] An engine structure using liquid hydrogen as coolant and fuel, comprising an inlet duct, a fan, a precooler, a compressor, a main combustion chamber, a high pressure turbine, a low pressure turbine, a mixing chamber, an afterburner and a nozzle arranged in sequence; the fan and the low pressure turbine are coaxially connected through a low pressure shaft, and the compressor and the high pressure turbine are coaxially connected through a high pressure shaft; the precooler is arranged in an inner bypass airflow path and located between the fan outlet and the compressor inlet; the precooler is communicated with a hydrogen storage tank, the main combustion chamber and the afterburner through pipelines; the hydrogen storage tank contains liquid hydrogen;

[0009] The fan divides the airflow into an outer bypass airflow and an inner bypass airflow; the outer bypass airflow directly enters the mixing chamber without passing through the precooler; the inner bypass airflow sequentially passes through the precooler, the compressor, the main combustion chamber, the high pressure turbine, the low pressure turbine and then enters the mixing chamber, mixes with the outer bypass airflow and then flows into the afterburner, and finally is discharged through the nozzle.

[0010] The precooler functions to exchange heat between the liquid hydrogen delivered by the hydrogen storage tank and the inner bypass airflow, so that the liquid hydrogen absorbs the heat of the inner bypass airflow and is vaporized into gaseous hydrogen, which is delivered to the main combustion chamber and the afterburner through the pipelines for fuel combustion.

[0011] The precooler only cools the inner bypass airflow and does not involve the cooling of the outer bypass airflow.

[0012] The amount of liquid hydrogen used by the precooler is determined by the fuel demand of the main combustion chamber and the afterburner.

[0013] An overall design method of an engine using liquid hydrogen as coolant and fuel, comprising the following steps:

[0014] 1) determining the size and performance parameters of the engine body based on the take-off task requirements of the aircraft, wherein the performance parameters include take-off thrust and exhaust velocity, and the size and performance parameters correspond to the parameters of the fan, the compressor, the main combustion chamber, the high pressure turbine and the low pressure turbine;

[0015] 2) determining the capture area of the inlet duct and the maximum outlet area of the nozzle based on the cruise task requirements of the aircraft;

[0016] 3) determining the engine control law along the flight path by comparing the inlet duct capture flow and the engine demand flow based on the flight path of the aircraft.

[0017] The engine control law is adjusted based on the comparison between the inlet duct capture flow and the engine demand flow, including: when the inlet duct capture flow is greater than the engine demand flow, maintaining the low pressure shaft at 100% relative physical speed, and the excess airflow of the inlet duct is overflowed; when the inlet duct capture flow is less than the engine demand flow, reducing the engine flow demand by reducing the low pressure shaft speed.

[0018] In step 3), the engine control law further comprises: the main combustion temperature is set according to the cycle calculation requirement; the tail nozzle throat is adjustable to adapt to the working condition change; the minimum residual gas coefficient of the afterburner is 1.35, and the maximum temperature limit is 2100K.

[0019] Compared with the prior art, the technical scheme of the present application has the beneficial effects that:

[0020] The present application only cools the core engine to enhance the pre-cooling effect, increase the core engine flow capacity, solve the wide speed flow matching problem, and avoid the external-duct pre-cooling flow loss, thereby improving the high Mach number performance. No turbine / ram mode conversion is involved, and problems such as engine shutdown / restart are not involved, so that the engine rotor can be continuously rotated, and the full speed range meets the demand for aircraft power supply, air supply and the like. In addition, high-temperature liquid hydrogen is used for pre-cooling, and the cooled hydrogen is used for combustion, thereby improving the specific impulse of the engine, and the comprehensive performance of the engine can be improved, and better safety and economy can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a configuration schematic diagram of the present application;

[0022] Figure 2 is an engine schematic diagram determined according to the ground task demand of the aircraft;

[0023] Figure 3 is an air intake and exhaust system schematic diagram determined according to the Ma4 cruise task demand of the aircraft;

[0024] Figure 4 is a relationship diagram of the flow captured along the flight path and the engine demand flow. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical schemes and beneficial effects of the present application more clear, specific embodiments are described in detail below.

[0026] Referring to Figures 1-2 , the engine configuration of the present application comprises a fan, a pre-cooler, a compressor, a main combustion chamber, a turbine (a high-pressure turbine and a low-pressure turbine), a mixing chamber, an afterburner and a tail nozzle arranged in sequence. The pre-cooler is installed between the inner-duct fan and the compressor, the fan and the low-pressure turbine are connected through a low-pressure shaft, and the compressor and the high-pressure turbine are connected through a high-pressure shaft.

[0027] The air flow passes through the fan and is divided into two paths, one of which flows through the outer channel into the mixing chamber, and the other of which flows through the inner channel, sequentially passes through the precooler, the compressor, the main combustion chamber, the high-pressure turbine and the low-pressure turbine, and then mixes with the outer channel air flow in the mixing chamber. After mixing, the air flow enters the afterburner for combustion, and finally is discharged from the tail nozzle. The liquid hydrogen is pumped from the hydrogen storage tank into the precooler to exchange heat with the air flow, and after heat exchange, the liquid hydrogen is vaporized into gaseous hydrogen and introduced into the main combustion chamber and the afterburner for combustion.

[0028] In the present application, the outer channel air flow does not need to pass through the precooler, thereby avoiding the problem of waste of "cold energy" generated by precooling the outer channel air flow. The inner channel air flow exchanges heat with the liquid hydrogen to cool down, and all the precooling agents only precool the inner channel air flow, which is relatively abundant, thereby effectively solving the "limited rotation" problem. The amount of liquid hydrogen used for precooling depends on the amount of combustion required by the main combustion chamber and the afterburner, thereby avoiding the problem of waste caused by the amount of liquid hydrogen required for precooling being greater than the amount of liquid hydrogen required for combustion.

[0029] The overall design method of the engine of the present application comprises the following steps:

[0030] 1) Based on the take-off task requirements of the aircraft, the size and performance parameters of the engine body are determined, the performance parameters including take-off thrust and exhaust velocity, and the size and performance parameters corresponding to the parameters of the fan, the compressor, the main combustion chamber, the high-pressure turbine and the low-pressure turbine;

[0031] 2) According to the task requirements of the aircraft at the cruise point, the capture area of the inlet duct and the maximum outlet area of the tail nozzle are determined;

[0032] 3) Based on the flight path of the aircraft, the engine control law along the flight path is determined by comparing the capture flow of the inlet duct and the flow demand of the engine.

[0033] As shown in Figure 3 , the parameters of the inlet and exhaust systems are determined according to the task requirements of the aircraft at the cruise point Ma4. The design point of the inlet duct is the cruise point Ma4 of the aircraft, and the capture flow of the inlet duct along the full speed domain of the flight path can be calculated according to the capture area of the inlet duct at Ma4, as shown in Figure 4 , which shows a trend of first increasing and then decreasing.

[0034] If the inlet duct is not considered, the engine adopts the following control law: ① the low-pressure shaft is at 100% relative physical rotating speed; ② the main combustion temperature is given according to the cycle calculation requirement; ③ the nozzle throat is adjustable to adapt to the change of engine working condition; ④ the minimum residual gas coefficient of the afterburner is 1.35, and the maximum temperature limit is 2100K. Under this control law, the demand flow of the engine along the flight path is as shown in Figure 4 .

[0035] In the case of Ma2 operating point, the intake passage trapped flow is consistent with the demand flow under the 100% speed control law of the low-pressure shaft of the engine, which is the control law switching point. Above Ma2 operating point, the engine demand flow is higher than the intake passage trapped flow, and the intake passage trapped flow control law is adopted, so the engine reduces the engine flow demand by reducing the speed to avoid the situation that the intake passage trapped flow is difficult to meet the engine demand flow. Below Ma2 operating point, the intake passage trapped flow is greater than the engine demand flow, and the 100% speed control law of the low-pressure shaft of the engine is adopted, and the excess flow of the intake passage is overflowed.

[0036] To calculate the engine performance of each point on the flight path, the following calculation method is adopted in the present application: in line with the conventional method, the core components of the hydrogen pre-cooling engine are modeled by the component method, and based on the component performance simulation, each component is packaged, the object-oriented whole machine performance modeling method is adopted, the whole engine modeling is completed by the logical connection relationship between components, and the working state and performance of the engine are determined by solving the working point of the engine. The difference lies in that the present application takes the pre-cooling amount and the combustion amount as the balance equation to realize the hydrogen pre-cooling-combustion flow balance. The model is programmed, and the sub-function is built in Matlab to realize it, and the engine working parameters and atmospheric conditions are set, and the program solves and outputs the state parameters of each component and the overall performance parameters of the engine under the corresponding working condition.

Claims

1. An engine configuration using liquid hydrogen as coolant and fuel, characterized in that: The system comprises an air inlet, a fan, a precooler, a compressor, a main combustion chamber, a high-pressure turbine, a low-pressure turbine, a mixing chamber, an afterburner and a tail nozzle, which are arranged in sequence; the fan and the low-pressure turbine are coaxially connected via a low-pressure shaft, and the compressor and the high-pressure turbine are coaxially connected via a high-pressure shaft; the precooler is arranged in the internal air flow path and is located between the fan outlet and the compressor inlet; the precooler is connected to the hydrogen storage tank, the main combustion chamber and the afterburner through pipelines; the hydrogen storage tank is filled with liquid hydrogen; Among them, the fan divides the incoming airflow into an outer airflow and an inner airflow; the outer airflow directly enters the mixing chamber without passing through the precooler; the inner airflow flows through the precooler, compressor, main combustion chamber, high-pressure turbine, and low-pressure turbine in sequence before entering the mixing chamber, mixing with the outer airflow and then flowing into the afterburner, and finally discharged through the tail nozzle.

2. The engine configuration using liquid hydrogen as coolant and fuel as claimed in claim 1, characterized in that: The function of the precooler is to exchange heat between the liquid hydrogen transported by the hydrogen storage tank and the inner air flow, and the liquid hydrogen absorbs the heat of the inner air flow and vaporizes into gaseous hydrogen, which is transported to the main combustion chamber and the afterburner through the pipeline to be burned as fuel.

3. The engine configuration using liquid hydrogen as coolant and fuel according to claim 1, characterized in that: The precooler only cools the inner airflow and does not involve the cooling of the outer airflow.

4. The engine configuration using liquid hydrogen as coolant and fuel according to claim 1, characterized in that: The amount of liquid hydrogen used by the precooler is determined by the fuel requirements of the main combustion chamber and the afterburner.

5. A method for designing an engine using liquid hydrogen as a coolant and fuel, applied to the engine configuration according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) Based on the aircraft's takeoff mission requirements, determine the engine's dimensions and performance parameters, including takeoff thrust and exhaust velocity. These dimensions and performance parameters correspond to the parameters of the fan, compressor, main combustion chamber, high-pressure turbine, and low-pressure turbine. 2) Determine the capture area of ​​the inlet and the maximum exit area of ​​the tail nozzle based on the aircraft's cruise mission requirements; 3) Based on the aircraft trajectory, compare the captured inlet flow rate with the engine demand flow rate to determine the engine control law along the trajectory.

6. The overall design method according to claim 5, characterized in that: The engine control law is adjusted based on the comparison between the intake duct captured flow and the engine required flow, including: when the intake duct captured flow is greater than the engine required flow, maintaining the low-pressure shaft at 100% relative physical speed and overflowing the excess airflow in the intake duct; when the intake duct captured flow is less than the engine required flow, reducing the engine flow demand by reducing the low-pressure shaft speed.

7. The overall design method according to claim 5, characterized in that: In step 3), the engine control rules also include: the main combustion temperature is set according to the cycle calculation requirements; the tail nozzle throat can be adjusted to adapt to changes in operating conditions; the minimum residual gas coefficient of the afterburner is 1.35, and the maximum temperature is limited to 2100K.

Images