• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method of determining a crankshaft rotation angle corresponding to a transient in-cylinder pressure of an engine independently of a rotary encoder, comprising: calculating a crankshaft rotation angle φ 0 corresponding to a maximum value of the pressure increase in a compression stroke; Determining a time sampling frequency of the transient in-cylinder pressure and recording a curve of the transient in-cylinder pressure change with time; Finding the maximum value of the pressure rise during the compression process, the time sampling point where the maximum value is equal to the calculated crankshaft rotation angle φ 0; and wave encoding all transient cylinder internal pressures with the crankshaft rotation angle φ 0 as the base point, finally obtaining a curve of the change of the in-cylinder transient pressure with the crankshaft rotation angle. The present invention does not require the mounting of a rotary encoder and simplifies the measuring system for a combustion process. With only one cylinder pressure sensor, the measurement and shaft coding of the in-cylinder transient pressure can be made, which reduces the difficulty of assembling the combustion process measurement system and reduces the likelihood of potential errors in combustion process measurement and saves system cost.
    公开号:CH713185B1
    申请号:CH00412/18
    申请日:2017-05-22
    公开日:2019-08-15
    发明作者:Wei Lijiang
    申请人:Univ Shanghai Maritime；
    IPC主号:
    专利说明:

    The present disclosure relates to the field of measurement of the internal combustion of cylinders in reciprocating internal combustion engines and in particular to a method for shaft coding of a transient internal cylinder pressure in engines independently of an encoder.
    PRIOR ART The performance and emission properties of a reciprocating internal combustion engine are directly related to the combustion process of fuels in the cylinder, so that analyzes of the combustion process in the cylinder are an important approach when analyzing the performance of the reciprocating internal combustion engine. The main parameters of the in-cylinder combustion process mainly include the in-cylinder transient pressure, the pressure rise, the transient heat release rate and the transient temperature, etc., where the in-cylinder transient pressure is obtained by direct measurement, while all other parameters are obtained by theoretical calculations based on the in-cylinder transient pressure , It can therefore be seen that an accurate measurement of the transient cylinder pressure is the key for the analysis of the combustion process in the cylinder.
    The transient internal cylinder pressure contains a magnitude of the pressure value and a corresponding crankshaft rotation angle, the pressure value being measured by a pressure sensor which is attached to a cylinder cap, and the crankshaft rotation angle which corresponds to the pressure value is given by an encoder. In order to guarantee the stability and accuracy of the measurement of the in-cylinder pressure values, it is generally necessary for the rotary encoder to be arranged on an end face of one end of the crankshaft; it should also be guaranteed that the encoder has a high degree of coaxiality with the crankshaft; meanwhile, the encoder must maintain vibration with the motor at the same time. All this places very high demands on the assembly of the encoder. In addition, the encoder and its mounting brackets must withstand strong vibrations during a work process, and damage to the mounting bracket and the body of the encoder can easily occur. It is therefore very desirable to specify a method for determining a crankshaft angle of rotation corresponding to a cylinder pressure value independently of an encoder, namely a method for shaft coding the transient internal cylinder pressure of engines.
    SUMMARY The present invention provides a method for shaft coding the transient internal cylinder pressure of engines, wherein a measurement and shaft coding of the transient internal cylinder pressure is carried out only with the aid of a cylinder pressure sensor, without the need to install a rotary encoder.
    In order to achieve the above object, the present invention provides a method for shaft coding the transient cylinder pressure of engines, comprising the following steps:
    Step S1: calculating a crankshaft rotation angle φ 0 , which corresponds to a maximum value of the pressure increase in a compression stroke, based on structural parameters of the engine;
    Step S2: determining a time sampling frequency f of the transient cylinder pressure;
    Step S3: measuring and recording a change curve of the transient internal cylinder pressure with time according to the time sampling frequency f, and calculating the pressure rise based on the measured pressure data;
    Step S4: Finding the maximum value of the pressure increase during the compression process from the curve of the pressure increase with time, the time sampling point at which the maximum value lies corresponds to the crankshaft rotation angle φο; and
    Step S5: shaft coding of all transient internal cylinder pressures based on the crankshaft rotation angle φ 0 , finally a curve of the change in the transient internal cylinder pressure depending on the crankshaft rotation angle is obtained.
    [0006] Step S1 specifically comprises the following steps:
    Match the compression process of the reciprocating internal combustion engine to the adiabatic process of a closed system, and match the air in the cylinder to an ideal gas, then create an equation (1):
    where P is the transient cylinder pressure, V is the transient volume of the cylinder, γ is the specific heat ratio, K is a constant, and P and V are both functions of the crankshaft rotation angle φ;
    Deriving according to the crankshaft rotation angle φ on both sides of equation (1), from which it follows:
    dP _ Ky dV d <p V y + l άφ (2) set z (^) = dV άφ so that equation (2) can be written as:
    (3) computing the maximum value of the pressure rise during the compression process, namely evaluating the maximum value in the equation (3); Set R '= 0;
    namely, __Vi (φ) - (/ + l) ï 2 ((Z>) y 7 + 2 = 0 (4);
    Obtaining an equation
    V1 (φ) - (/ + (5) In equation (5), y -P2L l + iλ cos · φ) 180
    (6) (7) where D is an engine cylinder diameter, S is a piston stroke, ε is a compression ratio of the engine, and λ = L is a ratio of a crankshaft radius r to a connecting rod length L;
    By inserting the expressions (6) and (7) into the equation (5), an equation around φ can be obtained, by directly solving or indirectly solving this equation the crankshaft rotation angle φ 0 , which is the maximum value of the pressure increase in the compression process corresponds, can be obtained.
    The indirect resolution of equation (5) in step S1 is given below:
    7- = 17'O) - (r + l) put r 2 (<p) (g) ;
    Insert equations (6) and (7) into equation (8), where T is a function of φ, so that the change curve of T can be obtained with the crankshaft rotation angle φ, the intersection of the curve with the straight line y = 0 in the compression process represents the solution to equation (5).
    [0012] The time sampling frequency f of the transient internal cylinder pressure in step S2 can be calculated by using equation (9):
    / _ 6 « 7 (9) where n is the number of revolutions after the stable running of the engine, and j is a predetermined crankshaft rotation angle interval width for coding the transient cylinder pressure.
    [0013] In step S3, the pressure increase can be calculated using a centered first-order difference method:
    P (i) = [/> (/ + 1) - P (i -1)] / 2 ,; = ! ™ (10) where i represents the i-th time sampling point.
    [0014] The present invention simplifies a measurement system for combustion processes. Only with a cylinder pressure sensor can the measurement and shaft coding of the transient internal cylinder pressure take place, which reduces the difficulty of installing the combustion process measuring system and reduces the probability of potential errors in the combustion process measurement and saves system costs.
    Brief Description of the Drawing [0015]
    1 shows a flow diagram of the present invention.
    2 shows a typical diagram of a transient internal cylinder pressure and a pressure increase as a function of the crankshaft rotation angle.
    3 shows a curve of the T value as a function of the crankshaft angle.
    4 shows a curve of the change in the transient internal cylinder pressure as a function of time.
    FIG. 5 shows a curve of the pressure rise, which is calculated according to the change in the transient cylinder pressure as a function of time.
    FIG. 6 shows a comparison diagram between the curves of the transient internal cylinder pressure detected with a rotary encoder and the transient internal cylinder pressure recorded without a rotary encoder.
    Detailed Description of the Embodiments Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to Figs. 1 to 6.
    As shown in FIG. 1, the present invention provides a method for shaft encoding a transient internal cylinder pressure of an engine, comprising the following steps:
    Step S1: calculating a crankshaft rotation angle φ 0 , which corresponds to a maximum value of the pressure increase in a compression stroke, based on structural parameters of the engine;
    As shown in Fig. 2, the pressure rise when a reciprocating internal combustion engine performs a compression stroke even though the transient cylinder pressure gradually increases as the piston moves upward, has a maximum value P'max, and the crankshaft rotation angle φ 0 , which corresponds to the maximum value , can be calculated based on structural parameters of the engine. The calculation principle is given below:
    Approximating the compression process of the reciprocating internal combustion engine to the adiabatic process of a closed system, and approximating the air in the cylinder to an ideal gas, so that an equation (1) is created:
    ν ' γ (D where P is the transient cylinder pressure, V is the transient volume of the cylinder, γ is the specific heat ratio, K is a constant, and P and V are both functions of the crankshaft rotation angle φ;
    Deriving according to the crankshaft rotation angle φ on both sides of equation (1), from which it follows:
    dP Κγ dV άφ Γ γ + 1 d <p (2)
    P dp . dV
    Set K = --- d. (P) = - άφ άφ so that equation (2) can be written as:
    Y / Y + 1
    (3) calculating the maximum value of the pressure rise in the compression process, namely evaluating the maximum value in the equation (3); Set R '= 0;
    namely,
    (4);
    Get an equation
    VÏ (φ) - (/ + 1) ϊ 2 {φ) = 0
    In equation (5),
    r / πΰ 2 S 5 , 1 , π 1 1V = ------- - Η-- 1 + - - cos (---  φ) - J 1 - / Γ sin “! --- · φ) > 4 μ- - 1 2 λ 180 180
    (6)
    (7) where D is an engine cylinder diameter, S is a piston stroke, ε is a compression ratio of the engine, and
    L is a ratio of a crankshaft radius r to a connecting rod length L;
    Inserting the expressions (6) and (7) into the equation (5) so that an equation around φ can be obtained to obtain the crankshaft rotation angle φ 0 , which corresponds to the maximum value of the pressure increase during the compression process ,
    In addition to the direct approach, an indirect approach to equation (5) is also possible, which is given below:
    Set T = Kr '(p) - (r + l) z 2 (p) (g) ; and
    Insert equations (6) and (7) into equation (8), where T is a function of φ, so that the change curve of T can be obtained with the crankshaft rotation angle φ. As shown in Fig. 3, the intersection of the curve with the straight line y = 0 during the compression process is the solution to equation (5). The indirect approach to solving equation (5) is preferred in the present invention;
    Step S2: Determining a time sampling frequency f of the transient cylinder pressure:
    When measuring the working state of the transient internal cylinder pressure, the engine speed n is recorded when the engine is running steadily; if j is a predetermined crankshaft rotation angle interval width for coding the transient cylinder pressure, the time sampling frequency f of the transient cylinder pressure can be calculated by the equation (9):
    (9).
    Step S3: Measuring and recording a change curve of the in-cylinder pressure with time according to the time sampling frequency /, and calculating the pressure rise based on the measured pressure data:
    As shown in equation (10), the pressure increase is calculated by a centered first order difference method:
    '(/) = [/> (/ + 1) - P (i -1)] / 2 t = i ... (10) } where i represents the i-th time sampling point.
    Step S4: Find the maximum value of the pressure increase during the compression process in the curve of the pressure increase with time, the time sampling point at which the maximum value is located corresponds to the crankshaft rotation angle φ 0 ; and step S5: shaft coding of all transient internal cylinder pressures based on the crankshaft rotation angle φ 0 in conjunction with an interval width j of the crankshaft rotation angle defined in step S2, finally a curve of the change in the transient internal cylinder pressure with the crankshaft Angle of rotation is obtained.
    [0028] The preferred embodiments of the present disclosure are described in more detail below by way of example.
    Example 1 When the cylinder diameter of a certain type of reciprocating internal combustion engine is 126 mm, the crankshaft radius is 65 mm, the connecting rod length is 219 mm and the compression ratio of the engine is 17, based on these parameters in connection with the expressions ( 6), (7) and (8), as shown in Fig. 3, a graph of the change in the value T depending on the crankshaft rotation angle can be obtained; from this it can be calculated that the crankshaft rotation angle, which corresponds to the maximum value of the pressure increase in the compression process, is φ 0 = -13.9 ° CA.
    A speed of the engine for measuring the combustion process in the cylinder is preferably chosen as 1500 r / min, the crankshaft rotation angle interval width for coding the transient cylinder pressure being 0.1 ° CA. According to equation (9) it can be calculated that the time sampling frequency of the transient cylinder pressure is 90 kHz. The curve that recorded the change in transient in-cylinder pressure with time at this frequency is shown in FIG. 4, and the curve of the pressure rise calculated based on the measured transient in-cylinder pressure is shown in FIG. 5. It can be seen from this that the point of the sampling time, which corresponds to the maximum value of the pressure increase during the compression process, is 3468, i.e. point 3468 corresponds to the crankshaft rotation angle of -13.9 ° CA. With -13.9 ° CA as the base point, according to the setting of the interval width of 0.1 ° CA between each sampling point, the entire curve of the transient internal cylinder pressure can be encoded with the crankshaft rotation angle, as shown in FIG. 6. In FIG. 6, the transient internal cylinder pressure obtained by the present invention is also compared with the transient internal cylinder pressure obtained by an assembled rotary encoder, where they essentially coincide and there is only a difference of 0.7 ° CA between the corresponding crankshaft angles. It can be seen that the method according to the invention not only achieves the goal of removing the rotary encoder, but also has sufficient accuracy.
    [0031] Although the content of the present invention has been described in detail by the above preferred embodiments, it should be recognized that the above description should not be construed as limiting the present invention. Various modifications and additions to the present invention will become apparent to those skilled in the art after reading the above contents. Therefore, the scope of the present disclosure is limited by the appended claims.
    claims
    权利要求:
    Claims (3)
    [1]
    1. A method for determining a crankshaft rotation angle corresponding to a transient internal cylinder pressure of an engine, independently of a rotary encoder, comprising the following steps:
    Step S1: calculating a crankshaft rotation angle φ 0 , which corresponds to a maximum value of a pressure increase in the compression process, based on structural parameters of the engine;
    Step S2: determining a time sampling frequency f of the transient cylinder pressure;
    Step S3: measuring and recording the transient cylinder pressure according to the time sampling frequency f, and calculating the pressure rise based on the measured transient cylinder pressure;
    Step S4: find the maximum value of the pressure increase during the compression process from the curve of the calculated pressure increase, the time sampling point at which the maximum value lies corresponds to the crankshaft rotation angle <p 0 ; and
    Step S5: shaft coding of all transient internal cylinder pressures based on the crankshaft rotation angle φ 0 , finally the variation of the transient internal cylinder pressure P depending on the crankshaft rotation angle φ is obtained, so that no encoder was used in the process.
    [2]
    2. A method for determining a crankshaft rotation angle corresponding to a transient internal cylinder pressure of engines independently of a rotary encoder according to claim 1, wherein step S1 specifically comprises the following steps:
    Approximating the compression process of a reciprocating internal combustion engine to the adiabatic process of a closed system, and approximating the air in the cylinder to an ideal gas, then creating an equation (1) based on these assumptions:
    K p = - vy (1) where P is the transient cylinder pressure, V is the transient volume of the cylinder, y is the specific heat ratio, K is a constant, and P and V are both functions of the crankshaft rotation angle <p;
    Derive according to the crankshaft rotation angle φ on both sides of equation (1), from which it follows:
    dP dcp
    Set Κγ dV (2) so that equation (2) can be written as:
    Κγ yf + l (3);
    Calculating the maximum value of the pressure rise during the compression process, namely evaluating the maximum value in equation (3); Set R '= 0;
    namely, (6)
    Obtaining an equation in equation (5), ί (φ) = y = 'P.
    π / fs
    180
    8 x 180 where D is an engine cylinder diameter, S is a piston stroke, ε is a compression ratio of the engine, and 1 - f is the ratio of the crankshaft radius r to the connecting rod length L; and
    Insert the expressions (6) and (7) into the equation (5) so that an equation around φ is obtained, whereby by directly solving or indirectly solving this equation the crankshaft rotation angle φ 0 , which is the maximum value of the pressure increase in the compression process corresponds, is obtained.
    [3]
    3. A method for determining a crankshaft rotation angle corresponding to a transient internal cylinder pressure of engines independently of an encoder according to claim 2, wherein the indirect solution of equation (5) is given in step S1 below:
    Set T = Kz '(ç ) - (/ + 1) z 2 (Ç9) (8) ; and
    Insert equations (6) and (7) into equation (8), where T is a function of φ so that a curve of the change in T with the crankshaft rotation angle φ is obtained, and an intersection of the curve with the straight line T = 0 during the compression process represents the solution to equation (5).
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    法律状态:
    优先权:
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