A Compressor Volume Flow Model of Diesel Engine Turbocharger in a Marine Engine Simulator

Abstract

The present invention discloses a compressor volume flow model of a diesel engine turbocharger in a marine engine simulator, including a kinetic energy increase module, which is used to obtain the flow velocity of the working medium entering the compressor through a sensor at the compressor inlet, calculate the mechanical energy of the working medium after entering the compressor according to the flow velocity of the working medium, calculate the inlet enthalpy value of the working medium before entering the compressor according to the specific heat capacity at constant pressure and the adiabatic temperature of the working medium, and calculate the total energy of the working medium after entering the compressor according to the mechanical energy obtained by the working medium and the inlet enthalpy value of the working medium; a kinetic energy to internal energy module, which is used to calculate the stagnation temperature and stagnation pressure of the working medium in the compressor according to the total energy of the working medium after entering the compressor; an internal energy to kinetic energy module, which is used to calculate the flow velocity of the working medium at the compressor outlet, calculate the mass flow rate of the working medium per unit time according to the flow velocity, and convert the mass flow rate of the working medium into a volume flow rate. The present invention reduces the dependence on compressor performance measurement data and improves the model accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of marine engine simulators, and particularly to a compressor volume flow model of a diesel engine turbocharger in a marine engine simulator. Background Art

[0002] The full mission marine engine simulator simulates the entire marine engine system of a ship and is a device mainly used for training seafarers. In addition to seafarer training, this simulation system can also be used for scientific research and simulation test verification research such as fault diagnosis, autonomous operation, and energy flow analysis of the marine engine system. The marine engine simulator consists of software and hardware, and its core is a software system that can simulate the entire engine room. The core of the software system is the model system. The model system determines the data representation and parameter coupling degree of each parameter of the marine engine system, and thus determines the credibility of system simulation. The diesel engine model is the core power equipment model in the model system of the marine engine simulator, and the turbocharger is an important component of the diesel engine model. The calculation of the compressor volume flow of the turbocharger is an important parameter in the turbocharger model and determines the amount of air flowing into the diesel engine combustion chamber. The measurement data of the compressor volume flow of marine turbochargers are mainly given by the manufacturer in the form of a map. The volume flow of the compressor at this time can be read from the map through the pressure ratio and speed of the compressor. These compressor performance maps only give the performance data of the compressor under normal operating conditions and do not give the performance data of the compressor in the surge zone and the choke zone.

[0003] In order to use the map data in the diesel engine model of the marine engine simulator, the map data can be read and a two-dimensional lookup table can be established, and then the two-dimensional interpolation method can be used to obtain the flow data at any speed and pressure ratio within the table boundary. The two-dimensional interpolation method only has good accuracy at the interpolation nodes. However, the accuracy is significantly reduced outside the interpolation points, and no data can be obtained when the query point exceeds the table boundary. In addition, the volume flow of the compressor can also be calculated through an empirical model of the compressor volume flow. However, all empirical models require a large amount of measurement data to identify the undetermined parameters of the empirical model. The output accuracy of the empirical model is determined by the undetermined parameters. When the optimization algorithm for identifying the parameters of the empirical model can converge, the output accuracy of the model is relatively high. When the optimization algorithm falls into a local optimum, the output accuracy of the empirical model decreases. When the optimization algorithm cannot converge and there are no identified parameters, the empirical model cannot be used. In addition to the interpolation model and the empirical model, there is also a mechanism model for calculating the compressor volume flow. The mechanism model can be divided into a real-time mechanism model and a non-real-time mechanism model. The non-real-time mechanism model cannot be applied to the model system of the marine engine simulator due to its too long calculation time. Summary of the Invention

[0004] The present invention provides a compressor volume flow model of a diesel engine turbocharger in a marine engine simulator to overcome the above technical problems.

[0005] A compressor volume flow model of a diesel engine turbocharger in a marine engine simulator, comprising:

[0006] A kinetic energy increase module, which is used to obtain the flow velocity of the working medium entering the compressor through a sensor at the compressor inlet, calculate the mechanical energy obtained by the working medium after entering the compressor according to the flow velocity of the working medium, calculate the inlet enthalpy value of the working medium before entering the compressor according to the constant pressure specific heat capacity and adiabatic temperature of the working medium, and calculate the total energy of the working medium after entering the compressor according to the mechanical energy obtained by the working medium and the inlet enthalpy value of the working medium.

[0007] A kinetic energy to internal energy module, communicating with the kinetic energy increase module, which is used to calculate the stagnation temperature and stagnation pressure of the working medium in the compressor according to the total energy of the working medium after entering the compressor.

[0008] An internal energy to kinetic energy module, communicating with the kinetic energy to internal energy module, which is used to calculate the flow velocity of the working medium at the compressor outlet according to the stagnation temperature and stagnation pressure of the working medium in the compressor, calculate the mass flow rate of the working medium per unit time according to the flow velocity, and convert the mass flow rate of the working medium into a volume flow rate.

[0009] Preferably, calculating the stagnation temperature and stagnation pressure of the working medium in the compressor according to the total energy of the working medium after entering the compressor is to calculate the stagnation temperature of the working medium according to formula (1) and calculate the stagnation pressure of the working medium according to formula (2).

[0010]

[0011]

[0012] wherein, T * is the stagnation temperature of the working medium, T1 is the adiabatic temperature of the working medium, U s is the flow velocity of the working medium entering the compressor, C p is the constant pressure specific heat capacity of the working medium, p * is the stagnation pressure of the working medium, p1 is the absolute pressure of the working medium, and k is the specific heat ratio of the working medium.

[0013] Preferably, calculating the flow velocity of the working medium at the compressor outlet according to the stagnation temperature and stagnation pressure of the working medium in the compressor includes calculating the flow velocity U2 of the non-critical state of the working medium according to formula (3).

[0014]

[0015] When the relationship between p2 and p * satisfies condition (4), the flow velocity of the working medium reaches the critical state.

[0016]

[0017] Calculate the flow velocity U2 at the critical state according to formula (5).

[0018]

[0019] where c p is the specific heat capacity at constant pressure of the working fluid, T * is the stagnation temperature of the working fluid, p2 is the absolute pressure of the working fluid at the compressor outlet, p * is the stagnation pressure of the working fluid, k is the specific heat ratio of the working fluid, and U2 is the flow velocity of the working fluid.

[0020] Preferably, calculating the mass flow rate of the working fluid per unit time according to the flow velocity includes calculating the mass flow rate of the working fluid per unit time in the non-critical state according to formula (6).

[0021]

[0022] Calculate the mass flow rate of the working fluid at the critical state per unit time according to formula (7).

[0023]

[0024] where dm is the mass flow rate of the working fluid, dt is the unit time, dm / dt is the mass flow rate of the working fluid per unit time, μ is the flow coefficient, A is the equivalent flow area, p * is the stagnation pressure of the working fluid, T * is the stagnation temperature of the working fluid, R is the gas constant corresponding to the working fluid, p2 is the absolute pressure of the working fluid at the compressor outlet, and k is the specific heat ratio of the working fluid.

[0025] Preferably, converting the mass flow rate of the working fluid into a volume flow rate is carried out according to formula (8).

[0026]

[0027] where dV is the volume flow rate, dm is the mass flow rate, R is the gas constant corresponding to the working fluid, T is the standard temperature, and p is the standard pressure.

[0028] Preferably, the stagnation pressure of the working fluid can also be estimated according to formula (9).

[0029] p * = p s + Δp (9)

[0030] where p s is the scavenging main pipe pressure value of the turbine simulator, and Δp is the difference between the stagnation pressure of the working fluid and the scavenging main pipe pressure.

[0031] The present invention provides a compressor volume flow model for a diesel engine turbocharger in a marine engine simulator. The compressor volume flow model is simple and easy to use and can be used in a marine engine simulator. According to the compressor volume flow model, the volume flow of the compressor can be directly calculated, improving the measurement accuracy. Compared with the existing empirical model of the compressor, the volume flow of the compressor in the critical state and non-critical state can be calculated, reducing the dependence on the compressor map data and the measurement data. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 is the model structure diagram of the present invention;

[0034] Figure 2 is the process diagram of the model construction of the present invention;

[0035] Figure 3 are the experimental results of the present invention;

[0036] Figure 4 are the experimental results of the KS model;

[0037] Figure 5 are the experimental results of the MJ model;

[0038] Figure 6 are the relative errors of the experimental results of the three models. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0040] Figure 1 is the model structure diagram of the present invention. As Figure 1 shown, this embodiment may include: a compressor volume flow model for a diesel engine turbocharger in a marine engine simulator, including

[0041] A kinetic energy increasing module, which is used to obtain the flow velocity of the working medium entering the compressor through a sensor at the compressor inlet, calculate the mechanical energy obtained by the working medium after entering the compressor according to the flow velocity of the working medium, calculate the inlet enthalpy value of the working medium before entering the compressor according to the specific heat capacity at constant pressure and the adiabatic temperature of the working medium, and calculate the total energy of the working medium after entering the compressor according to the mechanical energy obtained by the working medium and the inlet enthalpy value of the working medium.

[0042] Applying the law of conservation of energy, it is obtained that the inlet enthalpy value of the working medium and the mechanical work obtained from the compressor impeller are equal to the total energy of the working medium. Calculate the total energy obtained by the working medium according to formula (1). The total energy of the working medium is equal to the total enthalpy of the working medium. Calculate the total enthalpy of the working medium according to the formula.

[0043]

[0044]

[0045] Among them, E is the total energy of the working medium, C p is the specific heat capacity at constant pressure of the working medium, T1 is the adiabatic temperature of the working medium, E shaft is the mechanical work done by the compressor impeller on the working medium, U s is the flow velocity of the working medium, h * is the total enthalpy of the working medium.

[0046] A kinetic energy to internal energy module, which communicates with the kinetic energy increasing module, and is used to calculate the stagnation temperature and stagnation pressure of the working medium in the compressor according to the total energy of the working medium after entering the compressor. After the working medium enters the compressor, it enters a stagnation state. Calculate the stagnation temperature and stagnation pressure of the working medium in the stagnation state according to the total energy. Calculate the stagnation temperature of the working medium according to formula (3), and calculate the stagnation pressure of the working medium according to formula (4).

[0047]

[0048]

[0049] Among them, T * is the stagnation temperature of the working medium, T1 is the adiabatic temperature of the working medium, U s is the flow velocity of the working medium, C p is the specific heat capacity at constant pressure of the working medium. p * is the stagnation pressure of the working medium, p1 is the absolute pressure of the working medium, and k is the specific heat ratio of the working medium.

[0050] For the stagnation pressure of the working medium, it can be fine-tuned by the interpolation method. The stagnation pressure of the working medium is obtained according to formula (5).

[0051] p * =p s +Δp (5)

[0052] Among them, p s$p$ is the scavenging main pipe pressure value of the marine engine simulator, $\Delta p$ is the difference between the stagnation pressure of the working fluid and the scavenging main pipe pressure, and the stagnation pressure and stagnation temperature can be obtained according to the actual working environment of the compressor.

[0053] The internal energy to kinetic energy module, which communicates with the kinetic energy to internal energy module, is used to calculate the flow velocity of the working fluid at the outlet of the compressor according to the stagnation temperature and stagnation pressure of the working fluid in the compressor, calculate the mass flow rate of the working fluid per unit time according to the flow velocity, and convert the mass flow rate of the working fluid into a volume flow rate.

[0054] The calculation of the flow velocity of the working fluid at the outlet of the compressor includes calculating the non-critical flow velocity $U_2$ of the working fluid according to formula (6).

[0055]

[0056] When the relationship between $p_2$ and $p$ * satisfies condition (7), the flow velocity of the working fluid reaches the critical state.

[0057]

[0058] Calculate the critical flow velocity $U_2$ according to formula (8).

[0059]

[0060] Among them, $c$ p is the specific heat capacity at constant pressure of the working fluid, $T$ * is the stagnation temperature of the working fluid, $p_2$ is the absolute pressure of the working fluid at the outlet of the compressor, $p$ * is the stagnation pressure of the working fluid, $k$ is the specific heat ratio of the working fluid, and $U_2$ is the flow velocity of the working fluid.

[0061] The calculation of the mass flow rate of the working fluid per unit time according to the flow velocity includes calculating the mass flow rate of the working fluid per unit time in the non-critical state according to formula (9).

[0062]

[0063] Calculate the mass flow rate of the working fluid in the critical state per unit time according to formula (10).

[0064]

[0065] Among them, $dm$ is the mass flow rate of the working fluid, $dt$ is the unit time, $dm / dt$ is the mass flow rate of the working fluid per unit time, $\mu$ is the flow coefficient, $A$ is the equivalent flow area, $p$ * is the stagnation pressure of the working fluid, $T$ * is the stagnation temperature of the working fluid, $R$ is the gas constant corresponding to the working fluid, $p_2$ is the absolute pressure of the working fluid at the outlet of the compressor, and $k$ is the specific heat ratio of the working fluid.

[0066] The conversion of the mass flow rate of the working fluid into the volume flow rate is carried out according to formula (11).

[0067]

[0068] Wherein, dV is the volume flow rate, dm is the mass flow rate, R is the gas constant corresponding to the working fluid, T is the standard temperature, and p is the standard pressure.

[0069] Figure 2 It is the process diagram of the model construction of the present invention. p1, T1, p2, and T2 represent the inlet and outlet thermodynamic states of the compressor. Based on this thermodynamic state, kinetic energy increase process, stagnation process, and isentropic flow, a model is established to obtain the volume flow rate of the compressor, as well as the change curves of the working fluid temperature, total energy of the working fluid, and velocity of the working fluid of the compressor.

[0070] Through the comparative experiment of the model of this embodiment with the KS model and the MJ model, wherein, the KS model is a model for calculating the volume flow rate of the compressor proposed by Kang Song. This model belongs to the same type of model as this embodiment and is a simple real-time calculation model based on mechanism. Compared with the model proposed in this embodiment, the KS model is more complex and requires more geometric parameters. It can also be seen from the comparison diagram that its accuracy is lower.

[0071] The JENSEN model is an empirical model of the compressor volume flow rate. The MJ model is a modified version of the JENSEN model. Compared with the JENSEN model, the MJ model has higher accuracy. The JENSEN model requires a complete compressor map to work. Its calculation process is as follows:

[0072] (1) Obtain the compressor volume flow rate Q with a corresponding relationship according to the compressor map v , compressor pressure ratio Π, and supercharger speed N tc .

[0073] (2) Obtain the dimensionless head Ψ, normalized volume flow rate φ, and compressor tip Mach number M with a corresponding relationship.

[0074] (3) According to the data obtained in the second step, taking the JENSEN model as the objective function and formula, perform global optimization on the JENSEN model and identify the undetermined parameters.

[0075] (4) Substitute the identified undetermined parameters into the formula to obtain the JENSEN model.

[0076] From the solution process of the JENSEN model, after obtaining the MJ model, when it is necessary to solve the compressor volume flow rate at a specific rotational speed and specific pressure ratio, it is necessary to preprocess the rotational speed and pressure ratio according to the formula first, then substitute them into the MJ model for solution, and then use the formula to obtain the compressor volume flow rate. Although the MJ model has high accuracy, it requires a complete compressor map, which is exactly the data most lacking in compressor modeling. On the other hand, the identification effect of the MJ model is related to its initial value and optimization algorithm, and it cannot guarantee that the optimization process will definitely converge. When the optimization algorithm fails to converge, the accuracy of the MJ model drops significantly and it may even become unusable. In terms of computational complexity, the MJ model also has a higher computational complexity than the present invention.

[0077] At the same time, the commonly used RMSE evaluation index in the modeling field is used as the criterion for judging the quality of the model performance. RMSE is the root mean square error, and the calculation method is shown in formula (12).

[0078]

[0079] Among them, y i is the measured data of the compressor volume flow rate, is the compressor volume flow rate calculated by each model. n is the number of data points.

[0080] In order to analyze the error situation of the sample points, three parameters MAXE, R, and MAXR are defined, and their calculation methods are shown in formula (13) to formula (15). MAXE represents the maximum error value among all the compressor volume flow rate data points, and R represents the magnitude of the relative error of this maximum error value. MAXR represents the maximum value among all the relative errors.

[0081]

[0082] R = MAXE / y i *100% (14)

[0083]

[0084] (1) A comparative experiment is conducted on the model of this embodiment, the KS model, and the MJ model, and the experimental results are as Figures 3 - 6 shown, Figure 3 are the experimental results of the present invention, Figure 4 are the experimental results of the KS model, Figure 5 are the experimental results of the MJ model, Figure 6is the relative error of the experimental results of three models. Compared with the existing compressor mechanism models, the present invention has higher accuracy and its model parameters are easier to obtain. The compressor volume flow rate model of this embodiment is simple and easy to use and can be used in a turbine simulator. According to the compressor volume flow rate model, the volume flow rate of the compressor can be directly calculated, improving the measurement accuracy. Compared with the existing compressor empirical models, it can calculate the volume flow rate of the compressor in the critical state and the non-critical state, reducing the dependence on compressor map data and measurement data.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compressor volume flow model of a diesel engine turbocharger in a turbine simulator, characterized in that, including a kinetic energy increasing module configured to obtain the flow velocity of the working fluid entering the compressor through a sensor at the compressor inlet, calculate the mechanical energy obtained by the working fluid after entering the compressor based on the flow velocity of the working fluid, calculate the inlet enthalpy value of the working fluid before entering the compressor based on the specific heat capacity at constant pressure and the adiabatic temperature of the working fluid, and calculate the total energy of the working fluid after entering the compressor based on the mechanical energy obtained by the working fluid and the inlet enthalpy value of the working fluid a kinetic energy to internal energy module communicating with the kinetic energy increasing module and configured to calculate the stagnation temperature and stagnation pressure of the working fluid in the compressor based on the total energy of the working fluid after entering the compressor an internal energy to kinetic energy module communicating with the kinetic energy to internal energy module and configured to calculate the flow velocity of the working fluid at the compressor outlet based on the stagnation temperature and stagnation pressure of the working fluid in the compressor, calculate the mass flow rate of the working fluid per unit time based on the flow velocity, and convert the mass flow rate of the working fluid into a volume flow rate 2. The compressor volume flow model of the diesel engine turbocharger in the marine engine simulator according to claim 1, wherein The calculation of the stagnation temperature and stagnation pressure of the working fluid in the compressor based on the total energy of the working fluid after entering the compressor is to calculate the stagnation temperature of the working fluid according to formula (1) and calculate the stagnation pressure of the working fluid according to formula (2). Among them, T * is the stagnation temperature of the working fluid, T1 is the adiabatic temperature of the working fluid, U s is the flow velocity of the working fluid entering the compressor, C p is the specific heat capacity at constant pressure of the working fluid, p * is the stagnation pressure of the working fluid, p1 is the absolute pressure of the working fluid, and k is the specific heat ratio of the working fluid.

3. The compressor volume flow model of the diesel engine turbocharger in a marine engine simulator according to claim 2, wherein The calculation of the flow velocity of the working fluid at the compressor outlet based on the stagnation temperature and stagnation pressure of the working fluid in the compressor includes calculating the flow velocity U2 of the working fluid in the non-critical state according to formula (3). When the relationship between p2 and p * satisfies condition (4), the flow velocity of the working fluid reaches the critical state. Calculating the flow velocity U2 in the critical state according to formula (5). where c p is the specific heat at constant pressure of the working fluid, T * is the stagnation temperature of the working fluid, p2 is the absolute pressure of the working fluid at the compressor outlet, p * is the stagnation pressure of the working fluid, k is the specific heat ratio of the working fluid, and U2 is the flow velocity of the working fluid.

4. The compressor volume flow model of the diesel engine turbocharger in a marine engine simulator according to claim 3, characterized in that, The calculation of the mass flow rate of the working fluid per unit time based on the flow velocity includes calculating the mass flow rate of the working fluid per unit time in the non-critical state according to formula (6). Calculating the mass flow rate of the working fluid in the critical state per unit time according to formula (7). Among them, dm is the mass flow rate of the working fluid, dt is the unit time, dm / dt is the mass flow rate of the working fluid per unit time, μ is the flow coefficient, A is the equivalent flow area, p * is the stagnation pressure of the working fluid, T * is the stagnation temperature of the working fluid, R is the gas constant corresponding to the working fluid, p2 is the absolute pressure of the working fluid at the compressor outlet, and k is the specific heat ratio of the working fluid.

5. The compressor volume flow model of the diesel engine turbocharger in a marine engine simulator according to claim 4, wherein The conversion of the mass flow rate of the working fluid into a volume flow rate is performed according to formula (8). where dV is the volume flow rate, dm is the mass flow rate, R is the gas constant corresponding to the working fluid, T is the standard temperature, and p is the standard pressure.

6. The compressor volume flow model of the diesel engine turbocharger in a marine engine simulator according to claim 2, characterized in that The stagnation pressure of the working fluid can also be estimated according to formula (9). p * = p s + Δp (9) Among them, p s is the scavenging main pipe pressure value of the marine engine simulator, and Δp is the difference between the stagnation pressure of the working medium and the scavenging main pipe pressure.

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