SU728026A1 - Stand for testing internal combustion engine - Google Patents

Description

The invention relates mainly to automated systems for bench testing of engines. There are known test benches, internal combustion engines containing a shaft rotational frequency sensor and a load device, connected to the motor of the test engine. Measurement in such stands The complexity developed by the engine is carried out with the necessary moment of development of the engine, which requires a complicated stand, leading to an increase in its cost, especially when Application under factory conditions for type acceptance tests. / Stands containing are known. A shaft rotation frequency sensor and a load device made in the form of an electric machine with a phase or short-circuited rotor connected to the shaft of the motor under test; the active power meter, mechanical loss meter connected to the shaft rotation frequency sensor and digital recorder are connected to the stator circuit. When measuring the power being developed by the motor under test, supplied to the shaft of an electric machine operating in a generator mode, the active power meter measures the power recovered into the network by the stator of the electric machine. The signal from its output is summed with the output signals of the stator and rotor loss meters and the mechanical loss meter. The total signal, proportional to the motor test, is fed to the recording device. The device also makes it possible to measure the cranking power of the crankshaft (mechanical losses) of the test internal combustion engine when the electric machine is operating in motor mode. However, when the voltage of the power supply of the electric machine due to the dependence of the output signal of the loss meter in the rotor circuit on the magnitude

At the voltage of the electric machine, the power measurement error increases. Additionally, the error of power measurement appears inversely. It is proportional to the synchronous rotational frequency when the frequency of the power supply network of the electric machine is changed, which can vary by up to ± 1% depending on the frequency of the power supply network. The aim of the invention is to increase the accuracy of measuring the power of the motor under test by taking into account the deviation of the frequency of the current of the supply network. .

 This goal is achieved by the fact that the stand is additionally equipped with a transducer of mechanical power as a function of the rotational speed

shaft and frequency mains, made in the form of a frequency shaper, a scale unit, two multipliers and an adder, the frequency driver being connected to the network directly to the recorder through the first multiplication unit and an adder, to which the scale unit is also directly connected. through the second multiplication unit connected to the shaft rotation frequency sensor, the frequency driver, the first multiplication unit and the scale unit are connected in parallel to the active power meter. , .

On. FIG. 1 shows a functional layout of the stand; Fig. 2 is a mechanical power conversion circuit.

 The bench contains a load device made in the form of an asynchronous 1-phase electric machine. Or a short-circuited rotor connected to the shaft of the engine under test 2. The sensor 3 of the shaft rotation frequency is installed in the bulk of the electric machine. An active power meter 4 is connected to the stator circuit of the electric machine, the output of which is connected to the first input of the converter 5 of the mechanical power as a function of the shaft rotation frequency and the mains frequency. The second input of the mechanical power converter is connected to the shaft rotation frequency sensor, and the third input is connected to the mains. In series with the output of the converter 5 and the digital recorder 6, the output of the mechanical loss meter 7 is connected, the input of which is connected to the output of the sensor 3 of the shaft rotation frequency.

The mechanical power converter 5 contains multipliers 8 and 9 (FIG. 2), the outputs of which are connected to the first and second inputs of the adder 10. The first input of the multiplication unit 8 is connected to a frequency driver 11 proportional to the frequency of the mains supply connected to the power supply.

network. To the second input of the block-8 receives a signal of active power. The inputs of the multiplication unit 9 receive signals of the shaft rotation frequency and the active power signal scaled by the scale unit 12. 5 To the third entrance of cyMNiaTopa 10

connected to the second output of the scale unit.

When the engine is tested, the electric 1 operates in the generator mode. The active power of the OC recuperated by an electric machine into the network is measured by meter 4, which implements the formula

.

(one)

where and is the mains voltage; 0 - stator current; If is the angle between the current and stator voltage.

The signal from the meter 4 active power. Enters the input of the converter 5 mechanical power. Its second input receives a signal 5 from the sensor 3 of the shaft rotation frequency, the third - the supply voltage. The mechanical power converter implements the formula

. Rllh-a - L ()

where 1 2 constant coefficients

proportionality; I - shaft rotation frequency; th -, -. the frequency deviation of the supply voltage from the nominal value

M. (3)

where / LL electromagnetic moment; (jt) - the angular velocity of the rotor.

-

where

M,

f l; (4)

where РЗ / А ЗЕ Ч - electromagnetic power, whereЕ. EMF of the stator winding; Lti - С-ГС f- angle s.korost vrasheni magnetic flux of the stator, au / 2ТГп, (, get

(6)

MX

The value of mechanical power, calculated by the formula (6) without taking into account the frequency deviation of the supply network, differs from the value of the mechanical power calculated by the shape of formula (6), taking into account the frequency deviation of the supply network fj in the range of 11%, by

 V, Vc, S,, „

Claims (2)

Therefore, the final expression for determining the mechanical power will take the form of formula (2). To determine the power of the dricker, taking into account the mechanical losses in the electric machine, the formula,., G, where is the mechanical losses in the electric machine, is used. The composition of the reptile and formula (8) is obtained at the output of block 8 multiplication. Formula (7) for convenience of implementation is presented in the form of LR lx 2 otN The first term of this formula is implemented by block 9 at the knife, at the input of which the active power signal enters through scale unit 12, and its output signal is fed to sum 10. that the .onsfe second component of formula (9) is implemented by scale unit 12 and from the second ;. its output enters the UM 10 C output of the adder and a signal 1 is taken proportional to the mechanical power corresponding to the formula (). The total signal from the output of the converter 5 of the mechanical power and the meter 7 of the mechanical losses is fed to the digital recorder 6. When determining the power of cranking: the engine crankshaft, the electric machine operates in the propulsion mode and the polarity of the output signal of the meter 4 is reversed. The polarity of the output power of the mechanical power converter also changes accordingly. The difference between the signals of the converter 5 and the meter 7, i.e. power given by the shaft of the electric machine. The polarity of the signal at the input of the recorder changes in this case. The result is indicated with a sign (minus). The presence in the proposed stand of a mechanical power converter as a function of the shaft rotation frequency and the mains frequency and connecting it according to the formula to other units distinguishes the booth from the known solution, since they allow to increase the accuracy of the motor power measurement by taking into account the mains frequency deviation and exclude from loss bodies in the rotor circuit, the output signal of which depends on the magnitude of the supply voltage. The implementation of the stand does not present any difficulties, since it uses serial devices produced by domestic industry (for example, an 748 active ms meter, a 7025 measuring amplifier, and a 4830 digital voltmeter). P1 multiplication units can be performed on Mr. capacitor frequency converters having simple circuits. Invention Stand for testing an internal combustion engine containing a shaft speed sensor and a load device made in the form of an electric machine with a phase or short-circuited rotor connected to the motor under test, the active power meter, a mechanical pressure meter connected to the sensor, is connected to the stator circuit shaft rotation frequency, and a digital recorder, characterized in that, in order to improve the accuracy of measuring engine power by taking into account the frequency deviation, the current supply network, the stand is additionally equipped with a mechanical conditioner transducer as a function of shaft rotation frequency and mains frequency, made in the form of a frequency generator, a scale unit, two multiplication units and an adder, the frequency driver connected to the network directly and to the recorder through the first intelligent and the adder to which the scale block n. In particular, through the second multiplication unit, connected to the shaft rotation frequency sensor, the frequency driver, the first multiplication unit and the scale unit are connected in parallel to the active cable meter. Sources of information taken into account in the examination 1. Onproject of the company On Sokki, Automated stand for measuring indicators of toxicity of ICE, Japan, 1975. 2. USSR author's certificate number 558194, cl. G ai M 15/00, 1976 (prototype). fig}