Method for turbocharged engine full-cycle energy control

Abstract

This invention relates to the field of energy flow analysis and optimization technology for turbocharged engines, and discloses a full-process energy control method for turbocharged engines. First, based on the energy balance and mass balance equations of the two-stage turbocharger system and the bypass valves at the turbine and pressure ends of the high-pressure stage, a basic thermodynamic state calculation equation for the gas path is established. Then, the state parameters of the working gas in the external gas path are calculated using input and control parameters, and the state parameter values ​​at each degree of crankshaft rotation within the cylinder are calculated. These state parameters are then connected to obtain a complete full-process indicator diagram. Finally, the full-process indicated work is obtained by integrating the full-process indicator diagram. Furthermore, a distribution diagram of the full-process indicated work as a function of control parameters is obtained, and the optimization range of the control parameters corresponding to the optimized indicated work is derived from the distribution diagram, thus providing an indicative constraint range for the control of the indicated work.

Description

Technical Field

[0001] This invention relates to the field of energy flow analysis and optimization technology for turbocharged engines, specifically a method for full-process energy control of turbocharged engines. Background Technology

[0002] With advancements in engine technology, components that improve engine economy and performance, such as turbochargers, have been applied to engines. However, these components are primarily driven by energy converted from engine operation. The explanation of how to rationally allocate the energy generated within the engine cylinders and the energy used to drive these components outside the cylinders to maximize the engine's total output power has not been clearly defined.

[0003] Currently, the matching and optimization methods for two-stage turbochargers and engines mainly focus on matching and optimizing individual components, rather than combining the components with the engine's in-cylinder processes. How to organically combine the energy of the engine and the two-stage turbocharger into a unified whole for analysis remains an unsolved problem. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a method for full-process energy control of a turbocharged engine. Based on the relationship between the indicated work and control parameters throughout the entire process, an average value model of the turbocharged engine is built to calculate the optimal range of control parameters required for energy distribution throughout the entire process. The system is then controlled according to the parameter range corresponding to the optimal energy distribution. The technical solution is as follows:

[0005] A full-process energy control method for a turbocharged engine, wherein the turbocharged engine employs a two-stage turbocharged engine system, the system including a low-pressure stage compressor for sequentially supplying working gas, an interstage intercooler, a parallel high-pressure stage compressor and pressure-end bypass valve, an intake pre-intercooler, an engine, a parallel high-pressure stage turbine and turbine-end bypass valve, and a low-pressure stage turbine; and wherein the enthalpy of the exhaust gas at the turbine end is converted into mechanical energy through a central shaft between the turbine and the impeller to drive the impeller at the compressor end to rotate and compress the intake gas, the control method including the following steps:

[0006] Step 1: Based on the energy balance and mass balance equations of the two-stage turbocharging system and the bypass valves at the vortex end and pressure end of the high-pressure stage, construct the basic thermodynamic state calculation equations for the gas path.

[0007] Step 2: Calculate the state parameters of the working gas in the external gas path by inputting the initial intake pressure and initial intake temperature, and the control parameters: mass flow rate, vortex end, and pressure end bypass valve opening. Calculate the state parameter values ​​for each degree of crankshaft rotation in the cylinder, and connect the state parameters to obtain a complete full-process indicator diagram.

[0008] Step 3: Integrate the entire process of the indicator diagram to obtain the entire process indicated work, then obtain the distribution diagram of the entire process indicated work as a function of control parameters, and obtain the optimization range of the control parameters corresponding to the optimized indicated work from the distribution diagram, thereby proposing an indicative constraint range for the control of the indicated work.

[0009] Furthermore, step 1 specifically includes:

[0010] Step 1.1: After being discharged from the low-pressure stage compressor, the compressed air enters the interstage cooler. A portion of the enthalpy of the compressed air is converted into heat and lost by the heat exchanger. Finally, the working fluid possesses an enthalpy of... The energy calculation equation for the low-pressure stage compressor in the intake duct is:

[0011]

[0012] in, Enthalpy under standard atmospheric conditions. q represents the enthalpy of the working fluid at the outlet of the interstage intercooler. m,LPC K represents the mass flow rate of the low-pressure stage compressor. C R is the adiabatic index of the compressor working fluid. g,c π is the compressor working fluid gas constant, T1 is the working fluid temperature at the inlet of the low-pressure stage compressor, and π is the working fluid temperature at the inlet of the low-pressure stage compressor. LPC Q is the pressure ratio of the low-pressure stage compressor. c1 The heat flow rate for cooling the interstage intercooler;

[0013] Step 1.2: Adjust the mass flow rate entering the engine according to the opening degree of the pressure end bypass valve, thereby changing the total enthalpy entering the cylinder and affecting the work done in the cylinder, i.e., the total output power of the system. Therefore, adjust the opening degree δ of the pressure end bypass valve. C Defined as:

[0014]

[0015] Where, q m,Cbyp This refers to the mass flow rate of the pressure-end bypass valve.

[0016] The mass balance equation in the high-pressure stage compressor circuit is:

[0017] q m,HPC =q m,Cbyp +q m,LPC=q m,Cbyp +q m,in

[0018] Where, q m,HPC q is the mass flow rate through the high-pressure stage compressor. m,in The mass flow rate entering the cylinder;

[0019] From the above equation, we can obtain the mass flow rate relationship between the low-pressure stage and the high-pressure stage compressor:

[0020] (1+δ C )q m,LPC =q m,HPC

[0021] Step 1.3: The energy of the high-pressure stage compressor is transferred mechanically from the high-pressure stage turbine end through the intermediate connecting shaft. Therefore, the energy balance equation of the high-pressure stage compressor is:

[0022]

[0023]

[0024] Among them, C p,HPC T is the constant-pressure specific heat capacity of the high-pressure stage compressor. HPC T1 is the temperature at the outlet of the high-pressure stage compressor, T2 is the temperature at the inlet of the high-pressure stage compressor, and π is the temperature at the outlet of the high-pressure stage compressor. HPC The boost ratio for high-pressure stage compressors;

[0025] Then, under transient conditions, q m,HPC C p,HPC T HPC Will follow δ C Changes occur, δ under steady-state conditions C If it remains unchanged, then under this operating condition:

[0026]

[0027] in, The enthalpy at the outlet of the high-pressure stage compressor;

[0028] Step 1.4: The gas leaving the high-pressure stage compressor without returning through the pressure-end bypass valve enters the intake pre-intercooler for cooling. The enthalpy of the gas is the final enthalpy before entering the cylinder.

[0029]

[0030] Among them, Q c2 For heat exchange in the pre-intake intercooler, The enthalpy of the gas entering the cylinder;

[0031] The working fluid enters the cylinder and undergoes a thermal process within the cylinder. The energy balance equation within the cylinder is:

[0032] Q+Q HT =ΔE CV +ΔH+W

[0033] Q+Q HT =ΔE CV +(H out -H in )+W

[0034] Where Q represents the heat released by fuel combustion, Q HT For heat transfer from the cylinder wall to the outside, ΔE CV ΔH represents the change in residual exhaust gas internal energy between two adjacent cycles before the intake valve opens; ΔH represents the enthalpy difference between the gas entering and leaving the cylinder in the same cycle; W represents the work done by the gas pushing the piston; and H represents the change in residual exhaust gas internal energy between two adjacent cycles. out To exhaust the enthalpy of the gas in the cylinder, H in The enthalpy of the gas entering the cylinder.

[0035] Furthermore, step 2 specifically includes:

[0036] Step 2.1: Use the enthalpy output from the intake manifold as the enthalpy input to the cylinder, and the enthalpy discharged from the cylinder as the enthalpy input to the exhaust manifold, thereby connecting the energy balance inside and outside the cylinder; obtain the state parameters of the state point at each crankshaft rotation angle according to the energy balance equation inside the cylinder, and obtain the specific thermodynamic process inside the cylinder by connecting each state parameter;

[0037] The energy balance equation inside the cylinder includes:

[0038] Q = m f ·H m

[0039]

[0040] Where, m f H is the fuel injection amount per cycle. m The lower calorific value corresponding to the fuel; a g A is the average surface heat transfer coefficient inside the cylinder. i T is the internal surface area of ​​the cylinder. p T is the working fluid temperature. wi Where n is the wall temperature and n is the engine speed;

[0041] The mass balance equation within the cylinder during the same cycle shows that:

[0042] m in +m f =m out

[0043] Where, m in m is the total mass of gas entering the cylinder when the intake valve is closed.out This represents the total mass of gas leaving the cylinder at the end of the cycle.

[0044] but

[0045]

[0046] Where, q m,LPT This refers to the mass flow rate of the gas passing through the low-pressure turbine stage.

[0047] Then, from the mass balance equation at the turbine end of the high-pressure stage on the exhaust side, we get:

[0048] q m,HPT =(1-δ T )q m,LPT

[0049] Where, q m,HPT δ represents the mass flow rate of the gas passing through the high-pressure turbine stage. T This refers to the opening degree of the vortex end bypass valve;

[0050] Step 2.2: Obtain the thermodynamic process experienced by the working fluid and the state parameters at the inlet and outlet of the two-stage turbine based on the two-stage turbine energy balance equation:

[0051]

[0052]

[0053] in, To reduce the enthalpy of the gas discharged from the cylinder, π HPT and π LPT These represent the expansion ratios of the high-pressure stage turbine and the low-pressure stage turbine, respectively; T3 and T4 represent the inlet temperatures of the high-pressure stage turbine and the low-pressure stage turbine, respectively; W HPT and W LPT These represent the work output by the turbine to the connecting shaft as the gas passes through the high-pressure turbine and the low-pressure turbine, respectively; K T R is the adiabatic index of the gas passing through the turbine. g,T The gas constant of the gas passing through the turbine;

[0054] Step 2.3: This leads to the energy balance equation for the entire process, and the relationship between the output power and the opening degree of the bypass valves at the vortex end and pressure end, as well as the mass flow rate:

[0055]

[0056] As shown in the above formula, there is a principle relationship between the control parameters, the state parameters of the entire process, and the output power. Therefore, plotting the state parameters on a single indicator diagram results in the full-process indicator diagram of the turbocharged engine system.

[0057] The beneficial effects of this invention are:

[0058] This invention relates to obtaining the full-process indicated dynamometer diagram of each component under corresponding operating conditions using in-cylinder and out-of-cylinder energy balance equations, and obtaining the full-process indicated dynamometer based on this diagram. Then, based on the obtained trend of the engine's optimal indicated thermal efficiency under multiple operating conditions with the change of control parameters, and based on the trend under the same operating condition, the control parameter constraint range for the optimal indicated thermal efficiency under that operating condition is obtained, indicating the target control parameters that optimize the system's energy utilization efficiency under that operating condition. This organically combines the energy of the engine and the two-stage turbocharger into a whole, optimizing the system's energy utilization efficiency from the perspective of the overall system energy, avoiding the problem of inconsistency between the efficiency of a single component and the system's energy utilization efficiency, and providing a global optimization approach for indicated thermal efficiency. Attached Figure Description

[0059] Figure 1 This is a logic block diagram of the turbocharged engine full-process energy control method of the present invention.

[0060] Figure 2 This is a schematic diagram of the specific structure of a turbocharged engine system.

[0061] Figure 3(a) is a schematic diagram of the full-process indicator control.

[0062] Figure 3(b) is an enlarged view of the area within the dashed box in Figure 3(a).

[0063] In the diagram: 1-Low-pressure stage compressor, 2-Interstage intercooler, 3-High-pressure stage compressor, 4-Pressure end bypass valve, 5-Intake pre-intercooler, 6-Engine, 7-High-pressure stage turbine, 8-Scroll end bypass valve, 9-Low-pressure stage turbine. Detailed Implementation

[0064] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0065] This invention matches the turbocharger and engine based on existing matching methods for key parameters of turbocharged engines. Furthermore, based on the matched turbocharged engine, a full-process energy analysis is performed, and a control method is proposed to obtain the optimal indicated power throughout the entire process.

[0066] This invention relates to obtaining the full-process indicator diagram of each component under corresponding operating conditions using the in-cylinder and out-of-cylinder energy balance equations, and obtaining the full-process indicated power based on the diagram. Then, based on the obtained trend of the engine's optimal indicated thermal efficiency with the change of control parameters under multiple operating conditions, and based on the change trend under the same operating condition, the control parameter constraint range of the optimal indicated thermal efficiency is obtained.

[0067] This invention is based on a two-stage turbocharged engine system and performs full-process energy control. The specific logic is as follows: Figure 1 As shown.

[0068] The two-stage turbocharged engine system includes a low-pressure stage compressor 1, an interstage intercooler 2, a high-pressure stage compressor 3 and a pressure-end bypass valve 4 connected in parallel with it, an intake pre-intercooler 5, an engine 6, a high-pressure stage turbine 7 and a scroll-end bypass valve 8 connected in parallel with it, and a low-pressure stage turbine 9.

[0069] When the working gas enters the system, it first enters the low-pressure stage compressor 1 and is compressed. It then enters the interstage cooler 2 from the outlet of the low-pressure stage compressor 1 and is cooled. The gas at the outlet of the interstage cooler 2 mixes with a portion of the gas returning from the pressure-end bypass valve 4. The mixed gas then enters the high-pressure stage compressor 3.

[0070] At the outlet of the high-pressure stage compressor 3, the gas is divided into two parts: one part flows back through the pressure end bypass valve 4, and the other part enters the inlet pre-intercooler 5.

[0071] After being cooled by the pre-intercooler 5, the gas exiting the pre-intercooler 5 enters the cylinder after the intake valve opens. After passing through the internal circulation of the engine 6, the exhaust valve opens and the exhaust gas leaves the engine cylinder.

[0072] After leaving the engine cylinder, the exhaust gas is divided into two parts at the turbine inlet bypass valve 8 before the high-pressure stage turbine: one part passes through the turbine inlet bypass valve 8, and the other part passes through the high-pressure stage turbine 7 and mixes with the exhaust gas that has passed through the turbine inlet bypass valve 8 at the outlet. The mixed gas then passes through the low-pressure stage turbine 9, and its specific arrangement is as follows: Figure 2 As shown.

[0073] Outside the cylinder, the turbine end of the turbocharger is driven by exhaust gas, utilizing the energy in the exhaust gas to convert its enthalpy into mechanical energy. This mechanical energy is transmitted from the turbine end to the compressor end via the central shaft between the turbine and the impeller. The mechanical energy drives the impeller at the compressor end to rotate and compress the intake air, converting the mechanical energy into the enthalpy of the intake air. The shaft work transmitted by the central shaft of the high-pressure stage and the low-pressure stage turbocharger is expressed as W, respectively. HPT W LPT .

[0074] The intercooler cools the gas after single-stage supercharging, reducing its temperature and carrying away the enthalpy in the gas as heat. Inside the engine, combustion heats the working fluid in the cylinder, pushing the piston to output shaft power Wi through the crankshaft flywheel end in the form of mechanical energy.

[0075] Inside the cylinder, engine energy consists of the energy input from the intake air, the energy contained in the fuel, the energy lost due to heat dissipation, the energy used for external work, and the energy carried away by the exhaust gas.

[0076] According to the energy balance equation, in order to increase the power output in the cylinder, one can increase the energy of the intake air and reduce the energy carried away by the exhaust gas. However, if the energy carried away by the exhaust gas is reduced, the enthalpy available to the turbine in the exhaust gas path will decrease, and the work transferred from the turbine end to the compressor end will also decrease. Consequently, the energy carried by the gas entering the cylinder in the next cycle will also decrease. If other input energies remain unchanged, then the total output power in the next cycle will decrease.

[0077] To improve average power output, it is necessary to coordinate and control all components inside and outside the cylinder, and to study the turbocharger, intercooler, and engine as a system.

[0078] Since the power output of the entire system is solely generated by the engine through the shaft, the main content of this invention is to analyze how to adjust the control parameters of each part to optimize the power output of the entire system.

[0079] Based on the energy balance and mass balance equations of the two-stage booster system and the bypass valves at the vortex end and pressure end of the high-pressure stage, the basic thermodynamic state calculation equations of the gas path are constructed. In order to obtain the total output power of the entire process as mentioned above, this invention aims to obtain the total output power diagram of the entire process and integrates the total output power diagram of the entire process.

[0080] By inputting parameters such as initial intake pressure and initial intake temperature, and controlling parameters such as mass flow rate, vortex end, and pressure end bypass valve opening, the state parameters of the working gas in the external gas path, such as pressure p, temperature T, and specific volume v, are calculated. The state parameter values ​​under each degree of crankshaft rotation in the cylinder are also calculated. The state parameters are connected to obtain a complete full-process indicator diagram, as shown in Figures 3(a) and 3(b). In the figure, the ellipse represents the adjustable value range of the initial input parameters. The next operating point also has a corresponding value range of the input initial parameters calculated according to the equation. Different control parameters will cause different processes experienced by the working fluid. Therefore, it can be determined that there will be full-process indicator diagrams with different areas under different initial input parameters and control parameters.

[0081] In this invention, the turbocharger and engine have been matched. Based on the turbocharger characteristic parameters obtained from the matching calculation and the selected turbocharger model, the target parameters that the turbocharger's turbine end and pressure end can achieve under specific operating conditions, such as the boost ratio and expansion ratio, can be obtained.

[0082] Assuming the working fluid within the system is uniform and frictional losses are negligible, the overall energy balance equation combines the gas path energy balance equation and the in-cylinder energy balance equation to obtain the relationship between the engine's output power and the inlet mass flow rate, the vortex end, and the pressure end bypass valve opening.

[0083] W = f(q) m ,δT ,δ C )

[0084] Where W is the work done by the gas driving the piston, and q m δ is the mass flow rate of the gas entering the system. C δ represents the opening degree of the pressure-end bypass valve. T This refers to the opening degree of the vortex end bypass valve.

[0085] Fresh air first enters the low-pressure stage compressor of the two-stage turbocharger, taking the intake conditions as the initial input parameters. Intake conditions such as intake temperature, intake pressure, and intake flow rate can be controlled within a certain input range.

[0086] Fresh air is compressed in the low-pressure stage compressor. The energy consumed in compression comes from the mechanical work transmitted from the low-pressure stage turbine end of the previous cycle through the intermediate connecting rod. After being discharged from the low-pressure stage compressor, the compressed air enters the interstage intercooler. A portion of the enthalpy of the compressed air is converted into heat and lost by the heat exchanger. Finally, the working fluid has an enthalpy of [missing value]. During this process, the process experienced by the working medium and its state parameters before and after the process, such as pressure and specific volume, can be calculated.

[0087] Inlet low-pressure stage compressor energy calculation equation:

[0088]

[0089] in, Enthalpy under standard atmospheric conditions. q represents the enthalpy of the working fluid at the outlet of the interstage intercooler. m,LPC K represents the mass flow rate of the low-pressure stage compressor. C R is the adiabatic index of the compressor working fluid. g,c π is the compressor working fluid gas constant, T1 is the working fluid temperature at the inlet of the low-pressure stage compressor, and π is the working fluid temperature at the inlet of the low-pressure stage compressor. LPC Q is the pressure ratio of the low-pressure stage compressor. c1 The heat flow rate for cooling the interstage intercooler.

[0090] The enthalpy of the working fluid after intercooling is Before the high-pressure stage compressor, due to the presence of the pressure end bypass valve, some of the gas passing through the high-pressure stage compressor flows back and mixes with the gas after intercooling. The mixed gas enters the high-pressure stage compressor with new enthalpy, pressure, and specific volume. After compression, according to the opening of the pressure end bypass valve, some gas enters the cylinder, and some gas flows back to the front of the high-pressure stage compressor.

[0091] Changes in the opening of the pressure-end bypass valve of the high-pressure stage compressor alter the mass flow rate of the returning gas, thereby changing the pressure differential in the intake manifold and adjusting the total intake flow rate. Based on mass balance, the pressure-end bypass valve opening ultimately regulates the mass flow rate entering the engine, thus affecting the total enthalpy entering the cylinder and consequently the work done in the cylinder, i.e., the system's total output power. Here, the pressure-end bypass valve opening δ... C Defined as

[0092]

[0093] The mass balance in the high-pressure stage compressor gas path is as follows:

[0094] q m,HPC =q m,Cbyp +q m,LPC =q m,Cbyp +q m,in

[0095] Where, q m,HPC q is the mass flow rate after passing through the high-pressure stage compressor. m,Cbyp q represents the mass flow rate of the pressure-end bypass valve. m,in The mass flow rate entering the cylinder;

[0096] From the above equation, the mass flow rate relationship between the low-pressure stage and the high-pressure stage compressor can be obtained:

[0097] (1+δ C )q m,LPC =q m,HPC

[0098] The energy of the high-pressure stage compressor is transferred mechanically from the high-pressure stage turbine end through the intermediate connecting shaft. The energy balance equation for the high-pressure stage compressor is as follows:

[0099]

[0100]

[0101] Among them, C p,HPC For the isobaric specific heat of the high-pressure stage compressor, T HPC T1 is the temperature at the outlet of the high-pressure stage compressor, T2 is the temperature at the inlet of the high-pressure stage compressor, and π is the temperature at the outlet of the high-pressure stage compressor. HPC The boost ratio for high-pressure stage compressors.

[0102] Then, under transient conditions, q m,HPC C p,HPC T HPC Will follow δ C Changes occur, δ under steady-state conditions C If it remains unchanged, then under this operating condition,

[0103]

[0104] Where, δ C For the opening degree of the pressure end bypass valve, This refers to the enthalpy at the outlet of the high-pressure stage compressor.

[0105] Gas leaving the high-pressure stage compressor without returning via the pressure-end bypass valve enters the intake pre-intercooler. Its enthalpy is converted into heat and transferred to the cooling medium through the heat exchanger before leaving the system. The enthalpy of the cooled gas is the final enthalpy before entering the cylinder.

[0106]

[0107] Among them, Q c2 For heat exchange in the pre-intake intercooler, This refers to the enthalpy of the gas entering the cylinder.

[0108] The working fluid enters the cylinder and undergoes a thermal process within the cylinder. The energy balance equation within the cylinder is:

[0109] Q+Q HT =ΔE CV +ΔH+W

[0110] Q+Q HT =ΔE CV +(H out -H in )+W

[0111] Where Q represents the heat released by fuel combustion, Q HT For heat transfer from the cylinder wall to the outside, ΔE CV ΔH represents the change in residual exhaust gas internal energy between two adjacent cycles before the intake valve opens; ΔH represents the enthalpy difference between the gas entering and leaving the cylinder in the same cycle; W represents the work done by the gas pushing the piston; and H represents the change in residual exhaust gas internal energy between two adjacent cycles. out To exhaust the enthalpy of the gas in the cylinder, H in The enthalpy of the gas entering the cylinder.

[0112] The enthalpy output from the intake manifold is used as the enthalpy input to the cylinder, and the enthalpy discharged from the cylinder is used as the enthalpy input to the exhaust manifold, thus establishing a balance between in-cylinder and out-of-cylinder energy. Where ΔE CV The change in residual exhaust gas internal energy before the intake valve opens in two adjacent cycles is represented by the energy balance equation in the cylinder. The state parameters at each crankshaft angle can be obtained, and the specific thermodynamic process in the cylinder can be obtained by relating each state parameter.

[0113] In the formula:

[0114] Q = m f ·H m

[0115] Where, m f H is the fuel injection amount per cycle. m The low calorific value corresponding to the fuel

[0116]

[0117] Among them, a g A is the average surface heat transfer coefficient inside the cylinder. i T is the internal surface area of ​​the cylinder. p T is the working fluid temperature. wi n is the wall temperature, and n is the engine speed.

[0118] The in-cylinder mass balance equation for the same cycle shows that:

[0119] m in +m f =m out

[0120] Where, m in m is the total mass of gas entering the cylinder when the intake valve is closed. out This represents the total mass of gas leaving the cylinder at the end of the cycle.

[0121] but

[0122]

[0123] Where, q m,LPT This refers to the mass flow rate of the gas passing through the low-pressure turbine stage.

[0124] The mass balance equation for the turbine end of the high-pressure stage on the exhaust side can be obtained as follows:

[0125] q m,HPT =(1-δ T )q m,LPT

[0126] Where, q m,HPT δ represents the mass flow rate of the gas passing through the high-pressure turbine stage. T This refers to the opening degree of the vortex end bypass valve.

[0127] After being discharged from the engine to the exhaust end, the enthalpy carried by the engine exhaust is the same as the enthalpy of the working fluid input at the exhaust end. Assuming that the turbine can fully utilize the energy in the exhaust gas, then the enthalpy at the exhaust outlet is the enthalpy under standard atmospheric conditions. During the process of passing through the two-stage turbine, the exhaust gas drives the turbine to transfer work to the compressor end through the connecting rod. In this process, the enthalpy of the exhaust gas is converted into work. Therefore, according to the energy balance equation of the two-stage turbine, the thermodynamic process experienced by the working fluid and the state parameters at the inlet and outlet of the two-stage turbine can be obtained:

[0128]

[0129]

[0130] Among them, among them, To reduce the enthalpy of the gas discharged from the cylinder, π HPT and π LPT These represent the expansion ratios of the high-pressure stage turbine and the low-pressure stage turbine, respectively; T3 and T4 represent the inlet temperatures of the high-pressure stage turbine and the low-pressure stage turbine, respectively; W HPT and W LPT These represent the work output by the turbine to the connecting shaft as the gas passes through the high-pressure and low-pressure turbine stages, respectively; K T This is the adiabatic index of the gas passing through the turbine.

[0131] Combining the above equations, we can finally obtain the energy balance equation for the entire process, and the relationship between the output power and the opening degree of the bypass valves at the vortex end and pressure end, as well as the mass flow rate:

[0132]

[0133] This formula represents the relationship between the system's output power and the opening degree of the bypass valves at the vortex end and pressure end, as well as the mass flow rate. According to this formula, there is a fundamental connection between the control parameters, the state parameters of the entire process, and the output power. Plotting the state parameters on a single indicator diagram yields the full-process indicator diagram of the turbocharged engine system.

[0134] The entire process of the dynamometer diagram is integrated to obtain the indicated work of the entire process. Further, a distribution diagram of the indicated work of the entire process as a function of control parameters can be obtained. From the distribution diagram, the optimization range of the control parameters corresponding to the optimized indicated work can be obtained, thus providing an indicative constraint range for the control of the indicated work.

[0135] In summary, while analyzing turbochargers can optimize their power output, optimizing a single component may not necessarily have a positive impact on the overall system's output power because the system's power output is affected by multiple parameters. A more reasonable approach is to analyze the entire system process in a holistic manner and coordinate the control parameters within the system to optimize power output.

Claims

1. A full-process energy control method for a turbocharged engine, wherein the turbocharged engine employs a two-stage turbocharged engine system, the system comprising a low-pressure stage compressor (1) into which the working gas flows sequentially, an interstage intercooler (2), a parallel high-pressure stage compressor (3) and a pressure-end bypass valve (4), an intake pre-intercooler (5), an engine (6), a parallel high-pressure stage turbine (7) and a turbine-end bypass valve (8), and a low-pressure stage turbine (9); and wherein the enthalpy of the exhaust gas at the turbine end is converted into mechanical energy through a central shaft between the turbine and the impeller to drive the impeller at the compressor end to rotate and compress the intake gas, characterized in that, The control method includes the following steps: Step 1: Based on the energy balance and mass balance equations of the two-stage turbocharging system and the bypass valves at the vortex end and pressure end of the high-pressure stage, construct the basic thermodynamic state calculation equations for the gas path. Step 2: Calculate the state parameters of the working gas in the external gas path by inputting the initial intake pressure and initial intake temperature, and the control parameters: mass flow rate, vortex end, and pressure end bypass valve opening. Calculate the state parameter values ​​for each degree of crankshaft rotation in the cylinder, and connect the state parameters to obtain a complete full-process indicator diagram. Step 3: Integrate the entire process of the indicator diagram to obtain the entire process indicated work, then obtain the distribution diagram of the entire process indicated work as a function of control parameters, and obtain the optimization range of the control parameters corresponding to the optimized indicated work from the distribution diagram, thereby proposing an indicative constraint range for the control of the indicated work. Step 1 specifically includes: Step 1.1: After being discharged from the low-pressure stage compressor, the compressed air enters the interstage cooler. A portion of the enthalpy of the compressed air is converted into heat and lost by the heat exchanger. Finally, the working fluid possesses an enthalpy of... The energy calculation equation for the low-pressure stage compressor in the intake duct is: ； in, Enthalpy under standard atmospheric conditions. The enthalpy of the working fluid at the outlet of the intercooler. This refers to the mass flow rate of the low-pressure stage compressor. The adiabatic index of the compressor working fluid. The compressor's compression working fluid gas constant is... This refers to the working fluid temperature at the inlet of the low-pressure stage compressor. The boost ratio of the low-pressure stage compressor. The heat flow rate for cooling the interstage intercooler; Step 1.2: Adjust the mass flow rate entering the engine according to the opening of the pressure-end bypass valve, thereby changing the total enthalpy entering the cylinder and affecting the work done in the cylinder, i.e., the total output power of the system. Therefore, adjust the opening of the pressure-end bypass valve. Defined as: ； in, This refers to the mass flow rate of the pressure-end bypass valve. The mass balance equation in the high-pressure stage compressor circuit is: ； in, This refers to the mass flow rate after passing through the high-pressure stage compressor. The mass flow rate entering the cylinder; From the above equation, we can obtain the mass flow rate relationship between the low-pressure stage and the high-pressure stage compressor: ； Step 1.3: The energy of the high-pressure stage compressor is transferred mechanically from the high-pressure stage turbine end through the intermediate connecting shaft. Therefore, the energy balance equation of the high-pressure stage compressor is: ； ； in, The isobaric specific heat of a high-pressure stage compressor. This refers to the temperature at the outlet of the high-pressure stage compressor. This refers to the temperature at the inlet of the high-pressure stage compressor. The boost ratio for high-pressure stage compressors; Then, under transient conditions, Will follow Changes occur under steady-state conditions. If it remains unchanged, then under this operating condition: ; in, The enthalpy at the outlet of the high-pressure stage compressor; Step 1.4: The gas leaving the high-pressure stage compressor without returning through the pressure-end bypass valve enters the intake pre-intercooler for cooling. The enthalpy of the gas is the final enthalpy before entering the cylinder. ； in, For heat exchange in the pre-intake intercooler, The enthalpy of the gas entering the cylinder; The working fluid enters the cylinder and undergoes a thermal process within the cylinder. The energy balance equation within the cylinder is: ； ； in, The combustion of fuel releases heat. To transfer heat from the cylinder wall to the outside, This represents the change in the internal energy of the residual exhaust gas between two adjacent cycles before the intake valve opens. This refers to the enthalpy difference between the gas entering and leaving the cylinder in the same cycle. The amount of work done by the gas pushing the piston. To release the enthalpy of the gas from the cylinder, The enthalpy of the gas entering the cylinder; Step 2 specifically includes: Step 2.1: Use the enthalpy output from the intake manifold as the enthalpy input to the cylinder, and the enthalpy discharged from the cylinder as the enthalpy input to the exhaust manifold, thereby connecting the energy balance inside and outside the cylinder; obtain the state parameters of the state point at each crankshaft rotation angle according to the energy balance equation inside the cylinder, and obtain the specific thermodynamic process inside the cylinder by connecting each state parameter; The energy balance equation inside the cylinder includes: ； ； in, Fuel injection amount per cycle The low calorific value corresponding to the fuel; The average surface heat transfer coefficient inside the cylinder. The internal surface area of ​​the cylinder. For the working fluid temperature, The wall temperature, Engine speed; The mass balance equation within the cylinder during the same cycle shows that: ； in, This is the total mass of gas entering the cylinder when the intake valve is closed. This represents the total mass of gas leaving the cylinder at the end of the cycle. but ; in, This refers to the mass flow rate of the gas passing through the low-pressure turbine stage. Then, from the mass balance equation at the turbine end of the high-pressure stage on the exhaust side, we get: ； in, This refers to the mass flow rate of the gas passing through the high-pressure turbine stage. This refers to the opening degree of the vortex end bypass valve; Step 2.2: Obtain the thermodynamic process experienced by the working fluid and the state parameters at the inlet and outlet of the two-stage turbine based on the two-stage turbine energy balance equation: ； ； ； in, To expel the enthalpy of the gas from the cylinder, and These are the expansion ratios of the high-pressure stage turbine and the low-pressure stage turbine, respectively. and These are the inlet temperatures of the high-pressure stage turbine and the low-pressure stage turbine, respectively. and These represent the work output by the turbine to the connecting shaft when the gas passes through the high-pressure turbine and the low-pressure turbine, respectively. The adiabatic index of the gas passing through the turbine; The gas constant of the gas passing through the turbine; Step 2.3: This leads to the energy balance equation for the entire process, and the relationship between the output power and the opening degree of the bypass valves at the vortex end and pressure end, as well as the mass flow rate: ； As shown in the above formula, there is a principle relationship between the control parameters, the state parameters of the entire process, and the output power. Therefore, plotting the state parameters on a single indicator diagram results in the full-process indicator diagram of the turbocharged engine system.

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