SU1509659A1 - Method of measuring counter-pressure in i.c. engine exhaust system - Google Patents

Abstract

The invention relates to the testing of internal combustion engines and allows accelerating testing and reducing their labor intensity. When the engine is operating with exhaust units (neutralizers, gas turbines, etc.), the amplitude of one of the low-frequency components of the spectrum of the sound pressure level of the exhaust noise is measured, and the back pressure is determined from the calibration curve of the back pressure of the output from the specified amplitudes obtained during testing the same engine in the same mode, but without release units, with varying back pressure to release. The method is highly efficient, technologically advanced, and allows measurements to be taken remotely without interfering with the engine operation and without destroying the exhaust system. 2 Il.

Description

The invention relates to the testing of internal combustion engines and can be used to quickly evaluate the flow resistance of an exhaust; thawed gases from the engine exhaust system.

The purpose of the invention is to accelerate and reduce the complexity of the measurements.

FIG. Figure 1 shows the dependence of the release pressure P on the low-frequency component of the sound pressure level at about 0 ° C for the D-120 engine; in fig. 2 - the same for the D-21 engine.

The measurement process is as follows.

A specific type of internal combustion engine (for example, 60 hp at 2000 rpm) is used to remove the calibration curve and the magnitude of the amplitude of one of the low-frequency components of the exhaust spectrum against backpressure. At the same time the engine is installed in the open air or indoors. In measurements, classes 1 and 2 are used with a band-pass electrical filter. The measuring microphone is installed, for example, on a tripod at a distance of 0.25 m from the cut-off of the exhaust pipe at an angle of 60 to the flow. The low-frequency components can be selected octane components with standard geometric mean frequencies of octaves of 63 or 125 Hz, standard third-component components with geometric mean frequencies of diarrhea 40, 50, 63,

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80, 100 or 125 Hz or any narrowband components in the same frequency range. The calibration curve for this type of engine includes an aggregate

You have an unknown resistance and measure the magnitude of the same component of the spectrum. Calibration chart defines this resistance in the desired units of measurement. The installation points of the measurement microphone and the engine operating mode in all measurements remain constant.

Thus, the measurement of the back pressure is carried out indirectly by measuring the magnitude of one of the low frequency components of the sound pressure level generated by the exhaust noise. The magnitude of the resonant decrease in the amplitudes of the low-frequency exhaust systems from the aggregatism is negligible, since the wavelength, for example, the octane component with a standard geometric mean frequency of 63 Hz at the corresponding gases, is 7–10 m. therefore, a resonant decrease in amplitudes does not occur. Frequency reduction of the amplitudes of low-frequency oscillations occurs only due to losses on the resistances included in the engine exhaust system.

These resistances are the depths, spark arresters, ejectors, neutralizers, or any other aggregates installed in the exhaust system.

the resistance of the exhaust tract is measured by a separate piezometer with a 1C1 dim conversion in a unit of pressure. FIG. 1 and 2 are curves for determining the outlet

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The DS path is measured by measuring the low frequency component of the sound pressure level oL of the exhaust noise. An oktavan band with a geometric mean frequency of 62 Hz was chosen as such a component. The calibration charts obtained as a result of processing the data show that the exact value of the path resistance is assigned to any value of the component amplitude in the selected band.

The proposed method is more productive, technologically advanced, and allows measurements to be made remotely, without interfering with the engine operation and without destroying the exhaust system.

Claims (1)

Invention Formula A method for measuring backpressure in an exhaust system of an internal combustion engine, which means that when the engine is operated with an exhaust system equipped with the exhaust aggregates under investigation, parameters characterizing the counterpressure are measured and that testing and reducing labor intensity; As a specific yrimer of the amplitude of one of the low-frequency method, you can take the acoustic component of the emission level level of the D-21A engine and with various exhaust variants. systems (with a neutralizer, with a jamming-pressurization of the release and measurement of amclil, with a spark arrester, etc.),. then, and then on the engine with exploration. The frequency spectrum of the schum is amplified with a. measure the amplitude of the same by the complex of the noise measuring up-component and judging by it the magnitude Parameters that include a recorder of the level of back pressure in the exhaust system, a frequency spectrometer, a microphone. n preamp and cable. Change IU engine with the investigated units. of the components of the output spectrum from the counter-pressure in the exhaust system on the engine without the aggregates under investigation, by changing the value of the counter-pressure in the exhaust system IU engine with the investigated units. LR 9 8 1 6 5 4 Uh ipa "five 110 (rt.f fIS 0 (36 dLiS