SU1191773A1 - Bed for diesel testing - Google Patents

Abstract

A DIESEL TEST BENCH, containing a generator, generator excitation setting unit, exciter, exciter control system, generator current and voltage sensors, inverter, power setting unit, separating device, current regulator and inverter control system, the generator connected to the diesel shaft , the generator excitation winding is connected to the exciter, the excitation reference unit, the exciter control system and the exciter are connected in series, the inputs of the generator current sensors and eg 13 13 rf.K :; ,,. : -SICJti CTciiA of the generator is connected to each other, the inverter input and the generator core, the dividing device input is connected to the output of the generator voltage sensor, the first input of the current regulator is connected to the output of the dividing device, the second to the output of the generator current sensor, and the output the current controller through the inverter control system is connected with the control width of the latter, the output of which is connected to the network, characterized in that, in order to improve the accuracy of maintaining the test mode, an additional device (O Differentiator, multiplying device, scale with link, diode, comparison element, connected in series between voltage sensor and power setting unit, the differentiator communicating with multiplying device is connected through the first input from the last, the second input of multiplying device is connected The reference element is connected to the second input of the separator from the device.

Description

eleven

The invention relates to mechanical engineering, in particular to the diesel engine industry, and can be used for testing internal combustion engines.

The purpose of the invention is to improve the accuracy of maintenance mode.

FIG. 1 shows the block diagram of the proposed stand; in fig. 2 is a graph of changes in the angular frequency of CO from time t; in fig. 3 is a plot of angular acceleration versus time t.

The bench contains a generator excitation unit 1, an exciter control system 2 and an exciter 3 connected in series. The output of the exciter 3 is connected to the winding A of the generator 5, whose shaft is mechanically connected to the shaft of the test diesel 6. The anchor winding of the generator 5 is connected to the inputs of the generator 7 voltage generator and the generator current sensor 8 and | inverter 9, the output of the inverter is connected to the network 10 .

The output of the generator current sensor 8 is connected to the second input of the dividing device 11, the input of the differentiator 12 and the first input of the multiplying device 13. The splitter dividing device 11 is connected to the first input of the current regulator 14, the second input of the current regulator 14 is connected to the output of the voltage sensor 7 generator, and the output of the current regulator through the control system 15 is connected to the control bus of the inverter 9. The output of the multiplying device 13 is connected to the input of the scale link 16, and the output of the scale link 16 via diode 17 is connected to the subtractor input m element

18 Comparison. The summing input of the comparison element 18 is connected to the unit.

19, and the output of the element is connected to the first input of the splitter device 11.

The stand works as follows.

The supply of the driving signal from the excitation unit 1 to the input of the system 2 of the control of the exciter 3 leads to the flow in the excitation winding 4 of the generator 5. For a given frequency of rotation of the diesel 6, this leads to a voltage on the core winding of the generator 5, the value of which is determined by formula

TO

 p CO

(ABOUT

coefficient of proportionality, taking into account the parameters of the generator;

IB is the drive current; W is the angular velocity of the generator shaft.

When a signal appears at the output of the power setting unit 19, a signal appears at the output of the comparison element 18 and, therefore, at the first input of the dividing device 11. As generator 5 produces a voltage, the signal at the output of the sensor 7 of the generator voltage acts on the second input - a lithe device 11, the latter generates a signal equal to the ratio of the power setting to the voltage of the generator and arriving at the first input of the current regulator 14 causes the voltage on the control bus of the inverter 9 to appear and, as a result The flow of the load current of the generator 5 through the inverter 9 into the network 10. This leads to the appearance of a signal at the output of the generator current sensor 8 and at the second input of the regulator 14 current. Since this signal is subtracted from the signal at the first input in the current controller 14, the occurrence of the generator load current reduces the output voltage of this controller, reduces the output signal of the control system 15 and reduces the load current of the generator 5. As a result, the current sensor output signal generator decreases, and the voltage at the output of the control system .15 and the control bus of the inverter 9 increases, increasing the load current of the generator 5, the load current rises until the sensor output 7 no infinitely close to the output signal of the dividing device 11. The described processes stop when an equilibrium state occurs, in which the amount of power on the diesel engine shaft 6 (the product of the generator 5 voltage and the load current corresponds to the output signal value of the comparison element 18). the angular velocity of the diesel is constant, then the voltage of the generator, the derivative of this voltage 3 is constant, is equal to zero, as a result of which the output signal of the differentiator 12 is zero, the voltage on the output of multiplier 13 is zero since its second input is zero), the signal at the output of scale link 16 is zero, the diode 17 is closed and the i18 element does not receive a signal. Thanks; the last signal at the output of the comparison element 18 is equal to the signal of the power setting unit 19, and the magnitude at diesel power 6, which in this case coincides with the power of generator 5, corresponds to the specified value. When the setpoint of the mop-head changes, for example, when it is increased, the output voltages of the comparison element 18, divider device II, current regulator 14 and control system 15 increase, as a result of which the load current of the generator 5 flowing through the inverter 9 to the network 10 increases increase in the signal of the generator current sensor 8 The latter leads to a certain decrease in the output voltage of current regulator I4 and ultimately a decrease in the generator load current, which in turn causes a decrease in the signal from sensor 8, an increase in the output voltage of current regulator 14, an increase in load current, etc. The process of changing the load current and all other signals at the inputs and outputs of the elements of the stand is stopped when an equilibrium state occurs in which the power at the shaft of a diesel engine 6 (equal to the generator power 5 and the product of the generator current to the generator voltage) corresponds to the output signal of the comparison element 18 and (since the rotational speed is unchanged) the signal of the power setting unit 19.

Since in the bench under consideration, the electrical power produced by generator 5 is fed to the network via inverter 9 (the network voltage being lower than the generator voltage, the change in network voltage is a disturbance that disrupts the system balance. So, when the network voltage decreases As the generator and network grows, the load current of the General Scale link 16 transmits the received signal to the diode 17, which passes only the positive part of the signal and does not pass the negative part. link is

1,6-K, eLH g 3 -K85G

- coefficient of transfer

The link 16. 73.4 torus initially also increases, increasing the signal of the current sensor 8, reducing the voltage at the output of current regulator 14 and reducing the signal on the control bus of the inverter 9. The latter leads to a decrease in the generator load current and setting its value at this level in which his product on the generator voltage coincides with the task of power. In the cases described, the operation of the proposed stand is no different from the operation of the prototype test bench. Let us consider the work of the stand with an increase in the rotational speed of the diesel 6 and the constant setting of the power and voltage of the network. Since the excitation current of the generator 5 is set using the excitation setting unit 1 and does not depend on the generator rotation frequency, an increase in the rotation frequency leads to an increase in the generator voltage according to formula (l) and an increase in the output signal of the generator voltage sensor 7 supplied to the second input dividing device 11, the input of the differentiator 12 and the first input of the multiplying device 13. At the output of the differentiator 12 and the second input of the multiplying device, there is a signal equal to the derivative of the output voltage of the sensor 7 dUr d (KK, Ie (0) QC T and ,, i dt dt where dt is the time differential; K is the conversion factor of sensor 7 (the ratio of the sensor output signal to the generator voltage 5). In accordance with this, the output signal of the multiplying device 13 is determined by the expression ti:, U, U ,,. KK.IeCOkK, i, if.k, i; co; In the case under consideration, the frequency of rotation of the diesel increases, so that the right part of the expression (4) is positive, the voltage U | g positively and passes through the diode 17 to the subtractive input of the comparison element 18, and therefore the output signal of this element turns out to be equal to K ,,) §g K , К | 8- (9-.6 where P is the power task produced by block 19; K. „- block 19 conversion coefficient. At the same time, during rotation frequency of diesel 6, the output of dividing device 11 contains a signal Kt9Po-JMii KgKv, the value of which is less than in the initial steady state because the denominator became higher due to an increase in angular velocity as well as due to the occurrence of a positive value of j (odw / dt in the numerator of formula (6). Reducing the signal at the first input of the controller 14 leads to a decrease in its output signal, a decrease in the signal on the control bus of the inverter 9 and ultimately to lower The load current of the generator is the same as described above, while the load current has a value such that the output signal of sensor 8 is infinitely close to the output signal of the splitter device 11. The specified value is equal to (JCO K., Po-ico-K, Kg, JH J KK.IgWKg KKjKgleQJ () t Kl where K, is the conversion factor of the generator current sensor 8. Find the electrical power of generator 5, which is transmitted by inverter 9 to network 10, taking into account the formulas Cl and (7) YP If J,. Ju When accelerating the rotation of the internal combustion engine that drives the generator, the diesel power is determined by the formula a taking into account the formula (8 - as follows: When choosing the conversion factor of the power setting unit 19, equal to the product of the conversion factors of the sensors 7 and 8, i.e. at K ,, the last expression takes the form PoK7 Kg 3 Expression (9y shows that in a transient mode, in the process of increasing the rotational speed of a diesel engine, its power 6 coincides with the specified value P, and the power of the generator 5, as can be seen from expression (8), There are fewer tasks depending on the moment of inertia of the diesel generator system, the angular velocity of the shaft and the time derivative of this speed. In the prototype stand, there is no accounting for jwdo / dt, resulting in generator power equal to and diesel power equal to V t. E. More task. Therefore, as can be seen from the comparison of formulas (9) and (10), when testing a diesel engine on the proposed stand, the accuracy of maintaining the required power on its shaft in accordance with the signal of the power setting unit 19 is higher than when using the prototype stand . In fact, the deviation of diesel power from a predetermined value in the first case is zero, and in the second it is JGjdw / dt. Since a certain amount of fuel is supplied per unit of diesel power, the mass of fuel consumed by the motor at a greater power than at a lower power, i.e. when testing a diesel engine at a known stand in the process of increasing its rotational speed, the fuel consumption is greater than when testing a proposed stand. At the end of the transient process when testing a diesel engine on the proposed stand and establishing a constant rotational speed of -G-o. as a result, as seen from form (8) and (9), i.e. diesel power is equal to the generator capacity and coincides with the task of power. In the known stand, the generator electric power is equal to the power set by the power setting unit. When disturbances appear that violate the indicated equilibrium, for example, as the rotational speed increases, the voltage and current of the generator crust winding increase, the output signals of the generator current sensors and the generator voltage also increase, the output signal of the dividing device drops, Therefore, the output voltage of the current regulator decreases. The latter ultimately leads to a decrease in the current delivered by the inverter to the network, and a decrease in the current of the generator core circuit to such a level that the product of this current and the voltage of the generator cores coincides with the task of power. However, the power of the tested engine coincides with the power of the generator only in the established speed mode, and in the case considered, although the electrical power of the generator coincides with the task, it remains less than the engine power, i.e. power on the shaft is two bbmie generator powers and therefore more power setting. This is due to the fact that, when the rotational frequency of the motor-generator system changes, a dynamic moment occurs, which is determined according to the d'Alembert principle from equation J. i-f-V. where j is the moment of inertia of the rotating masses of the engine-generator system; M (3j, - engine torque 738 M - generator torque. If you multiply both sides of the equation by the angular velocity OJ, you get the power ratio in the transition mode CO jdO / dt OMe-uM Pj - Pp. Ignoring component (ojd (0 / dt causes low accuracy in engine maintenance with changes in engine speed during tests. Since positive accelerations increase engine power compared to its steady state value, the engine consumes more fuels during tests with increasing engine speed. which, in steady state, with the same generator power and the test efficiency is low. This disadvantage is exacerbated when testing a diesel with gas turbine supercharging, since the increasing mass of diesel fuel supplied to the cylinders burns insufficiently due to a shortage of charge air due to the considerable inertia of the turbocharger. Consequently, to obtain the required diesel MODjHocTH, the fuel supply to its cylinders ensured by the built-in The speed limit is greater than for a naturally aspirated diesel, and the test efficiency is even lower. Thus, in comparison with the known, the proposed stand provides higher accuracy of maintaining diesel power and efficiency of its tests, since with a constant setting of power, the diesel power coincides with the task not only in the established high-speed mode of its operation, but also in transition , and since the magnitude of this power is less than during tests on the prototype stand, the fuel consumption is lower, and the efficiency of the tests is higher.

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Claims (1)

STAND FOR A DIESEL TEST, comprising a generator, a generator excitation task unit, an exciter, an exciter control system, generator current and voltage sensors, an inverter, a power set unit, a divider, a current regulator and an inverter control system, the generator being connected to the diesel shaft , the excitation winding of the generator is connected to the exciter, the excitation task unit, the exciter control system and the exciter are connected in series, the inputs of the generator current sensors and the generator voltage are connected each other, the inverter input and the generator winding, the first input of the dividing device is connected to the output of the generator voltage sensor, the first input of the current regulator is connected to the output of the dividing device, the second to the output of the generator current sensor, and the output of the current regulator through the inverter’s control system ' connected to the control bus of the latter, the output of which is connected to the network, which is due to the fact that in order to increase the accuracy of maintaining the test mode, a differentiator is added to the stand, a multiplier for a device, a scale link, a diode, a comparison element connected in series between the voltage sensor and the power setting unit, and the differentiator is connected to the multiplier via the first input of the last, the second input of the multiplying device is connected to the voltage sensor, the comparison element is connected to the second input of the dividing device. SU <. "1191773 1 1191773