SU758197A1 - Device for simulating piston engine - Google Patents

Description

The invention relates to analog computing and can be used, for example, when setting up, calibrating and calibrating devices intended for automated control of operating parameters of piston engines.

A simulator is known which contains a constant-source source. | θ voltage, variable capacitor with an electric motor, simulating a crankshaft, a capacitor that simulates the amount of dead space of a compressor, a delay unit, diodes and resistors [1]. This device is not

allows you to simulate simultaneously the function of pressure and displacement of the piston from the top dead center.

The closest solution to the invention ^τθχ λη is a device ^ί for modeling a piston engine that contains an adder, a clock generator, a ring pulse distributor to η outputs, input 25 of which is connected to the output of the clock generator, a reference voltage source, a block of weight resistors connected by an input with a reference voltage source, block

2

from η keys, informational inputs of which are connected to the outputs of the weight resistors unit, control inputs to the corresponding outputs of the ring pulse distributor, and outputs to the first input of the adder [2}. This device allows you to simulate a given function by setting the output voltage, proportional to the values of the weighting function of the simulated object, at discrete equidistant moments of time. This is achieved by pre-setting the resistance values of the resistors that specify the weight part of the function, while preparing the task. However, this device also does not allow to simulate the working process in the cylinder of a piston engine.

The aim of the invention is to expand the functionality of the device by reproducing the functions of pressure and displacement of the piston in the cylinder of a piston engine and register with the extreme positions of the piston.

This is achieved by the fact that a device for simulating a piston engine, containing an adder, gene3

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clock pulse, ring pulse distributor to η outputs, the input of which is connected to the output of the clock pulse generator, operative voltage source, weight resistors block, connected to the output of the voltage source, a block of n keys, information inputs of which are connected to the outputs of the weight resistors block , control inputs - with the corresponding outputs of the ring pulse distributor, and outputs - with the first input of the adder, additionally contains two single vibrators, an additional unit of weight resistors, an additional block of η keys, a controlled voltage divider, an additional adder, to the inputs of which constant and variable scale resistors are connected, the input of the additional block of weight resistors is connected to the output of the reference voltage source, and its outputs are connected to the information inputs of the additional key block the inputs of which are connected to the corresponding outputs of the ring pulse distributor, the outputs' s 1 through η / 2-nd - with the free output of a constant large-scale resistor , and outputs p / 2 + 1 to p-th - with a free output of variable scale resistor, the output of the additional adder is connected to the input of a controlled voltage divider, the output of which is the output of pressure modeling in the cylinder of the piston engine of the device, η and η / 2 the outputs of the ring pulse distributor through the first and second one-shot are connected respectively to the second and third inputs of the adder, the output of which is the output of the simulation of the displacement of the piston of the device.

Figure 1 shows the functional diagram of the device; figure 2 - timing charts of his work.

The device contains a clock pulse generator 1, a ring pulse distributor to η outputs 2, an adder 3, a key block 4, an additional block of keys 5, a block 6 of weight resistors, an additional block 7 of weight resistors, a reference voltage source 8, a controlled voltage divider 9, an additional adder

10, permanent large-scale resistor

11, variable scale resistor

12, first and second one-shot 13

and 14.

The device works as follows. ·

In the study of the characteristics of the engine or to maintain its technical and economic indicators during operation, it becomes necessary to measure the average indicator pressure P; , indicator

power максимально ,, maximum, ιό combustion pressure Р ₂ and crankshaft rotation speed η, as the main parameters of the engine, most fully reflecting its working process.

To find these parameters, the following dependencies are usually used:

^p (ψ) ρ (4>) ό φ ⁽¹⁾

about (2)

ν, -α.ρ-and

where Ρ (φ) is the current value of the gas pressure in the engine cylinder;

Agsopy! - Coefficient, taking into account the design features of the engine

[and (φ) = & ίη φ + - ^ - 5 <η2φ- Function,

linking the displacement of the piston from the top dead center (VMt.) with the angle of rotation of the crankshaft.

Depending the value of L

there is a ratio of the radius of the crank to the length of the connecting rod.

Devices for measuring P, M; η are mainly electronic computing units that implement dependencies (1) and (2). Original

information for them is usually provided by signals from pressure sensors installed in engine cylinders, which display Ρ (φ), and a piston stroke sensor, which simulates the function ρ (φ) in electrical form.

So that these devices really display the real values of P; or other indicators of the engine, you must adjust or ottarirovat accordingly. For this, it is necessary to have standardized (normalized) signals equivalent to the values of [n (φ) and Ρ (ψ),

For the simulation of which the proposed device is designed, which operates as follows.

The pulses of the generator 1 with a repetition rate (see Fig.2A) come

to the input of the pulse distributor 2, alternately distributing these pulses to the control inputs of the key blocks 4 and 5, which under their action are alternately closed, as a result, during the closure of the keys of blocks 4 and 5, the voltage from the voltage source 8 goes to the outputs of the pressure and piston displacement modeling devices. In one case, the voltage at the device output goes through the circuit: voltage source 8 - -block 7 - keys of block 5 - resistors 11 or 12, adder 10 - divider 9 device output on channel Ρ (φ), and in the second case, on the circuit: source . voltage 8 - block 6 - keys of block 4 - adder 3 - output of the device via channel / and (φ).

five

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Figure 2 in and d shows the simulated functions P (ίο) and p ((p). The repetition period of these functions corresponds to one revolution of the crankshaft, and the functions themselves are quantized through equal angles Df determined by the repetition rate of clock pulses ί _τ . The magnitude of Df is selected on the basis of obtaining the required accuracy of modeling, calculating the resistance value of the resistors of blocks b and 7 at each quantization point in accordance with the law of change of the ψ (ψ) or / and (φ) function, it is possible to realize a piecewise - step approximation of the function P (\ p) and Ν ί

As can be seen from figure 2, the function D) (φ! Is symmetric about the abscissa axis, therefore its integral value per cycle (360 °) is 0. It follows that the value of P according to expression (1) is determined by the value of P (), and it is precisely its symmetry about the axis of ordinates.When the left and right half of the ordinates are relative to the ID, ie, the compression and expansion lines of the function Ρ (ψ), the average indicator pressure is 0.

This corresponds to the operation of the engine with the fuel supply turned off. Consequently, by changing the amplitude of the expansion line, it is possible to simulate the operation of the engine, i.e. change the value of P ₍ -,

N, or P,. In the proposed device, this is achieved as follows. The voltage source 8 is fed to the input of the additional adder 10 from N. m.t. to v.m. through the resistor 11, and from the v.m. BC Nm. through the resistor 12. If the resistance values of these resistors are equal, then the input signal of the compression and expansion lines is equally attenuated, i.e.

R. * = ^p p (see Fig. 2c), which corresponds to the value P) = 0. When reducing the resistance of the resistor 12 decreases. the weakening of the output pressure signal at the expansion section, i.e. from vm BC Nm. Thus, by changing the resistance value of the resistor 12, you can set the desired value of the average indicator pressure P,. The signal proportional to P (f) comes from the output of the additional adder 10 to the output through a controlled voltage divider 9, with which, by changing the attenuation of the output signal, you can change the amplitude P (f), simulating the value of P <or P, (see figure 2c).

To register the extreme positions of the piston, one-shot vibrators 14 and 13 are used, which, when pulses appear at the output η / 2 and η of the pulse distributor 2, form short pulses arriving at the input of the adder 3 and registering at the output of the piston displacement modeling

devices in the form of instantaneous bursts (smfg.2g).

Thus, the proposed device allows to simulate periodic pressure signals P (ψ] and piston displacements (k (c>) simultaneously and synchronously. At the same time, by changing the scale of variable resistor 12, you can set the required value p ·, changing the transfer coefficient of the divider 9 - P _with or P ^, and by changing the frequency) of the repetition of clock pulses повтор _τ ~ the frequency of repetition of the functions <u (f) and P () depending on the type of engine being modeled.

The proposed simulator favorably differs from the prototype, because it allows you to simultaneously generate pressure signals and piston displacements with their previously known law of change, which allows you to simulate real signals from the indicator process of piston machines and use them as standards when setting up instruments for measuring workflow in an engine .

Claims (1)

Claim A device for simulating a piston engine, containing an adder, a ring pulse distributor to η outputs, whose input is connected to the output of a clock generator, a block of weight resistors, connected to the output of a reference voltage source, a block of η keys, whose information inputs are connected to the outputs of the block weight resistors, the control inputs with the corresponding outputs of the ring pulse distributor, and the outputs with the first input of the adder, which is the fact that, in order to expand Opportunities due to the reproduction of the functions of pressure and displacement of the piston and registration of its extreme positions in the cylinder of a piston engine, it contains two single-vibration additional weight resistors, an additional block of key, a controlled voltage divider, an additional adder, the inputs of which are connected respectively and variable scale resistors, the input of the additional block of weight resistors is connected to the output of the reference voltage source, and its outputs - with information by the inputs of an additional key block, the control inputs of which are connected to the corresponding outputs of the ring pulse distributor, outputs 1 through η / 2-nd with a free output of a constant large-scale resistor, and outputs with n / 2 + 1 on the nth - with a free output re7 758197 eight a large-scale resistor, the output of an additional adder is connected to the input of a controlled voltage divider; the output of which is the simulation of pressure in the cylinder of the piston engine of the device, p and η / 2-nd outputs of the ring pulse distributor through the first and second one-oscillators are connected respectively with the second and third inputs of the adder, the output of which is the output of the simulation of the displacement of the piston of the device.