RU2834903C1 - Method of determining volume of internal combustion engine crankcase - Google Patents

Abstract

FIELD: mechanical engineering; measuring.

SUBSTANCE: method of determining volume of an internal combustion engine crankcase relates to machine building. Method comprises: during the preparatory stage at the outlet of the receiver with the help of a gas reducer with a closed valve in the crankcase, a pressure of not less than 300 kPa is set, monitoring with the help of a pressure gauge, then providing an air flow rate of not less than 40 l/min, opening the valve to the required value, controlling the air flow meter, after establishing the required air flow mode and switching on the pressure recording system, the process of recording the time and pressure in the crankcase using a pressure sensor is started, at the measurement stage, the air outlet valve is shut off and when the specified pressure is reached for 1 minute, the rate of pressure rise in the crankcase is continued, as per the results of the obtained measurements, the value of air leaks is determined and the volume of the crankcase is calculated using the given formula.

EFFECT: simpler process of measuring volumes of complex shape, such as crankcase of an internal combustion engine, while improving measurement accuracy.

1 cl, 4 dwg, 4 tbl

Description

The invention relates to the field of mechanical engineering and can be used in all areas of the national economy to determine the volume of the crankcase space of internal combustion engines, under industrial production conditions, during their operation and during experimental work, the determination of which is carried out on the basis of information computer systems of numerical control and experimental data.

A method is known for grading a vertical cylindrical tank to determine the capacity corresponding to the height of its filling (RU 2521212 C1), in which a digital vector three-dimensional (3D) model of the outer surface of the tank is constructed when filling it with a calibration liquid in separate fixed doses by scanning the outer surface of the tank using a ground-based laser scanner with a linear scanning step resolution within 2 to 5 mm from at least four scanner stations and in accordance with the operating documentation for the device.

The disadvantages of this invention are the high labor intensity of the process and the use of expensive equipment with a high precision class.

The invention (RU 2698596 C2) describes a method for determining the volume of oil added to the crankcase of an internal combustion engine during vehicle maintenance. The method is based on the use of a standard oil level gauge. The position of the recorded oil level relative to the upper mark on the oil level gauge is found by measuring the distance from the said mark to the recorded oil level. The volume of oil required for adding to the engine crankcase is then determined: the coefficient taking into account the volume of oil in liters per 1 mm of the distance between the upper and lower marks on the oil level gauge is multiplied by the distance in mm measured from the upper mark to the oil level recorded on the oil level gauge.

The disadvantage of this method is the unreliability of the crankcase volume value due to the viscous and lubricating properties of the engine oil, which settles on the engine parts and assemblies.

A method for measuring the internal volume of vessels of various volumes with a complex internal surface and a device for implementing it are known (RU 2787722 C1). The essence of the method lies in the fact that any vessel from the production flow of a given standard size is used as a reference vessel, having previously determined its volume V _e , while the known volume of the reference vessel V _e is compared with the volume of the measured vessel V _u . The reference vessel is installed on the device in the measuring branch of the pneumatic system, the vessel is sealed and the ejection circuit of the measuring and reference branches of the device is evacuated. Then the pressure in both branches is equalized by moving the plunger in the adjustable control tank. When equality of pressures is achieved in both branches, the position of the plunger is fixed. The volume of the reference vessel in the adjustable control tank is fixed. The measured vessel is installed on the device in the measuring branch, the operations are repeated without changing the volume of the control tank of the reference branch. The pressure is equalized by moving the calibration rod in the adjustable capacity of the measuring unit. The difference ΔV in the volumes of the reference and measured vessels is determined by the magnitude of the movement of the calibration rod, and the desired volume of the vessel V _u is determined by the formula: V _u = _Vэ ±ΔV ^cm3 .

A method for determining the volume of a container is known (RU 2664769 C1). In the method for determining the volume of a container, which includes connecting a controlled container with a calibrated container of known volume, the calibrated and controlled containers are filled with gas, for example air, to a certain pressure, this pressure is measured, then the entire volume of gas from the calibrated container is introduced into the controlled container, the steady-state gas pressure in the controlled container is measured, and the desired volume of the controlled container is determined from the increased value of this pressure.

In the invention (RU 2494352 C1), the method for measuring the volume of a vessel and the device for implementing it change the volume of the vessel by the value ΔV and determine the change in gas pressure in the vessel before and after changing the volume, on the basis of which the desired volume of the vessel V ₀ is determined. In this case, the pressure in the hermetically sealed vessel is first equalized with the environment. By moving the rod, its volume is changed by the value ΔV ₁ and the pressure ΔP ₁ inside the vessel is measured in relation to the external environment. Then it is verified that it does not change over time. The volume of the vessel is changed by the value ΔV, the pressure in the vessel is equalized with the environment, the volume of the vessel is changed again by the value ΔV ₂ , the pressure ΔP ₂ inside the vessel is measured in relation to the external environment and it is again verified that it does not change over time. The required volume of the vessel V ₀ is determined by the formula: V ₀ = (ΔV⋅k⋅ΔP ₂ /ΔV ₂ )/(ΔP ₂ /ΔV ₂ -ΔP ₁ /ΔV ₁ ), where k = 1 if the volume of the vessel is reduced and k = -1 if it is increased.

The disadvantage of these methods is that before taking measurements, the volume of the measured vessel is reduced by a known value, and the true volume is determined as the sum of the measured and introduced volumes into the vessel, which is why these methods do not allow measurements of a non-hermetic measured container.

In the method (RU 2026533 C1), excess pressure is created in the measured non-hermetic container, the pressure source is disconnected, the change in pressure over time is recorded, and the time constant is calculated. The measured container is connected to the reference container, observing the condition of free gas flow. The time constant of the system consisting of the measured and reference containers is determined. Based on the values of the time constants of the measured container and the system, the volume of the container is determined.

The disadvantage of the proposed invention is its high labor intensity due to the selection of pipelines of a size (cross-sectional area and length) such that its resistance to gas flow is two orders of magnitude less than the resistance to flow that the measured capacity has due to leakage.

A method is known (RU 2018790 C1) in which a fixed amount of indicator gas is introduced to determine the capacity, the pressure of the mixture, the concentration of indicator gas in it are measured, and the measurement results are processed.

The disadvantages of this method are the high labor intensity of the preparatory work associated with mixing the indicator gas in the test container, as well as determining the values of the change in the volume of the non-hermetic container during operation.

The closest to the claimed technical solution is the method for determining the volume of a non-hermetic container (RU 2601615 C1), which consists of increasing the pressure in the container being tested, disconnecting the pressure source, and recording the change in pressure over time.

However, the disadvantage of this invention is the high labor intensity of obtaining the desired result.

An analysis of known technical solutions has shown that the technical problem in this area is the need to create methods used to determine the volume of a container of complex shape, a closed non-hermetic space, in particular the volume of the crankcase space.

The technical result that the proposed invention is aimed at achieving is the simplification of the process of measuring volumes of complex shape, such as the crankcase of an internal combustion engine, while increasing the accuracy of the measurement.

The technical result that provides a solution to the specified problem consists in reducing the number of operations in the process of measuring the volume of a container and eliminating special substances from the process, in simplifying the interrelationship of functional and measuring operations and in replacing the principle of indirect measurement with the direct principle of measuring the volume of a container.

In order to solve the specified problem and obtain the stated technical result in the method for determining the crankcase volume of an internal combustion engine, at the preparatory stage at the outlet of the receiver using a gas reducer with the valve closed, a pressure of at least 300 kPa is set in the crankcase, monitoring using a pressure gauge, then an air flow rate of at least 40 l/min is ensured by slightly opening the valve to the required value, monitoring with an air flow meter, after establishing the required air flow mode and turning on the pressure recording system, the process of recording the time and pressure in the crankcase is turned on using a pressure sensor, at the measuring stage the air outlet valve is closed and upon reaching the specified pressure, the rate of pressure increase in the crankcase is continued to be recorded for 1 minute, and based on the results of the measurements obtained, the amount of air leaks is determined and the crankcase volume is calculated using the formula:

where V _k is the crankcase volume;

ΔV - volume of air entering the crankcase;

Δp - pressure drop in the crankcase depending on the amount of incoming air;

p ₂ - crankcase pressure.

The technical result is achieved due to the fact that the measurement of the crankcase volume is determined by supplying air at a specified flow rate into a closed crankcase and recording the rate of pressure increase in it.

As a result of the piston movement at a speed of c _n, the volume occupied by crankcase gases V _k changes (the pumping action of the piston), which affects the change in pressure P _kg .

When the removal of crankcase gases from the crankcase through the crankcase ventilation system ceases, the pressure P _kg in the crankcase will change over time, and the rate of change of this pressure will depend on the flow rate of crankcase gases G _g , their temperature T _kg , the volume occupied by the crankcase gases V _k and the influence of the movement of the engine pistons on this volume.

The volume of crankcase space occupied by gases depends on the design of the engine crankcase, the volume of oil in the crankcase, and also on the position of the piston, which depends on the angle of rotation of the crankshaft.

The implementation of the method is shown in the drawings:

Fig. 1 shows the calculation scheme of the crankcase space;

Fig. 2 shows a diagram of the installation for measuring the volume of the crankcase space;

Fig. 3 is a graphical representation of the process of changing the pressure in the crankcase during measurement;

Fig. 4 shows the dependence of the results of measurements of the crankcase volume on the flow rate of the supplied air.

The installation diagram for measuring the crankcase volume includes a compressed air source 1, a gas reducer 2, a pressure gauge 3, an air flow valve 4, for monitoring the air pressure in the crankcase - a pressure gauge 5, a valve 6, a pressure sensor 7, a flow meter 8 recording the gas flow from the receiver, a recording system 9.

Fig. 1 shows the calculation scheme of the crankcase space.

Denoting the volume of the crankcase of the engine unfilled with engine oil with the piston at the top dead center V _к0 and the volume of oil poured into the engine crankcase _Vм , and also taking into account the change in volume due to the movement of the piston _Vп , we obtain the volume of the crankcase space occupied by gases _Vк in the form:

To determine the volume of the crankcase occupied by crankcase gases in accordance with dependence (1), the volume of the crankcase of an engine not filled with engine oil with the pistons in the top dead center position V _к0 remains unknown.

The measurement process can be described as follows. Air is supplied from compressed air source 1 through gas reducer 2, the pressure of which is controlled by pressure gauge 3 and the flow rate is regulated by valve 4. Gas flow rate from receiver with valve 6 open is recorded by flow meter 8 and regulated if necessary by valve 2. Air pressure in crankcase is controlled by pressure gauge 5. Change in air pressure in crankcase during measurement is recorded by pressure sensor 7 and recording system 9.

The measurement process is carried out in the following order.

1. At the outlet of receiver 1, using gas reducer 2 with valve 4 closed, a pressure of at least 300 kPa is established, which is monitored by pressure gauge 3.

2. Open valve 6 to release air from the crankcase through flow meter 8.

3. Valve 4 is opened to the required value to ensure the specified flow rate, which is controlled by flow meter 8.

4. After establishing the required flow mode (the flow meter readings 8 are stabilized and the flow rate corresponds to the required one) and turning on the pressure recording system 9, the installation is ready to take measurements.

5. The process of recording time and pressure in crankcase 9 is activated using pressure sensor 7.

6. Close the air outlet valve 6.

7. When the set pressure, recorded by pressure gauge 5, is reached, valve 2 is closed and the pressure change in the crankcase is recorded by measuring system 9 for approximately 1 min. This allows the amount of air leakage through leaks to be assessed.

8. Based on the results of the measurements obtained, the following are determined: the initial pressure in the crankcase P ₁ , the time for the pressure to increase to P ₂ (no more than 25 kPa), the amount of air entering the crankcase during this time ΔV, the pressure drop in the crankcase during the same time ΔP _y and the crankcase volume is calculated.

When setting the excess pressure at the outlet after the reducer to 300 kPa and increasing the pressure in the crankcase during the measurements to the excess pressure level of 25 kPa, the ratio of the absolute pressures at the inlet and outlet of valve 4 will be 2.39, which is greater than the critical pressure drop for air equal to 1.89. Thus, the gas flow regime in valve 2 will be critical and will not depend on the change in air pressure in the crankcase. The process of changing the pressure is shown in Fig. 3, where t ₁ , t ₂ , t ₃ are the moments of the beginning and end of air supply and the end of pressure recording, respectively; p ₁ , p ₂ , p ₃ are the air pressure corresponding to the moments t ₁ , t ₂ , and t ₃ ; Δp _y = p ₂ - p ₃ is the pressure drop after the end of air supply.

The change in air pressure in the crankcase Δp=(p ₂ -p ₁ ) from the amount of incoming air can be described by an expression in accordance with the equation of state of an ideal gas:

where: ΔV=Q _in ⋅Δt is the volume of air entering the crankcase;

Q _in - volumetric flow rate of incoming air;

Δt=(t ₂ -t ₁ ) - time of the air supply process to the crankcase;

ρ _in - air density;

V _k - crankcase volume;

R - gas constant;

T _kg is the temperature of gases in the crankcase.

The change in pressure Δp=(p ₂ -p ₁ ) in the crankcase from the amount of incoming air can be described by an expression in accordance with the equation of state of an ideal gas:

where: ΔV=Q _в ⋅Δt is the volume of air entering the crankcase; Q _в is the volumetric flow rate of incoming air; Δt=(t ₂ -t ₁ ) is the time of the air supply process to the crankcase; ΔV _y is air loss due to leaks; V _к is the crankcase volume.

Taking into account that in expression (2) the product (ρ _in ⋅R⋅T _kg ) represents the air pressure in the crankcase at the end of the measurements p ₂ , then after transformations we obtain an expression for the crankcase volume:

If air leaks occur during the measurement process, the crankcase pressure will decrease after valve 4 is closed (air supply is stopped) (section after moment t ₂ ). During the time (t ₃ -t ₂ )=(t ₂ -t ₁ ), the crankcase pressure will decrease by the value Δр _y (Fig. 3). To take into account the amount of leaks on the measurement result, we will make a correction to the recorded value Δр.

At the beginning of the process of air supply to the crankcase (time t ₁ ), the pressure in the crankcase p ₁ is practically equal to the ambient pressure and the leaks are zero. At the pressure in the crankcase p ₂ , the value of the leaks leads to a decrease in pressure by Δр _y . Assuming the growth of leaks is proportional to the growth of excess pressure in the crankcase, the average value of leaks will be proportional to half the pressure loss at p ₂ or will be 0.5⋅Δр _y . Then the calculation of the volume of the crankcase space will be calculated using the expression:

Using this dependence, it is possible to determine the volume of the crankcase space of any configuration and use the obtained value in further research.

Example of implementation of the method.

1. From a compressed air source 1 through a gas reducer 2 (with a pressure gauge 3, air is supplied, the flow rate of which Q _kg is recorded by a gas flow meter 8) and is regulated by a valve 4.

2. After establishing the flow mode and recording the flow rate by the flow meter 8, the system for recording 9 the time and pressure in the crankcase is switched on using the pressure sensor 7.

3. Close the air outlet valve 6.

4. When the set pressure, recorded by pressure gauge 5, is reached, valve 4 is closed and the recording of the change in pressure in the crankcase (the presence of gas leaks from the space) continues by measuring system 9 for ≈1 min.

5. Open valve 6 and release excess pressure from the measured volume.

6. Based on the results of the measurements obtained, the following are determined:

- initial pressure in the crankcase P ₁ ;

- time Δt of pressure increase to P ₂ ;

- the amount of air entering the crankcase during this time ΔV=Q _kg ⋅Δt;

- pressure drop in the crankcase ΔP _y after closing valve 4 for the same time Δt;

- the crankcase volume is calculated using formula (4).

At the beginning of the tests, the calibration of the pressure sensor was checked. For this purpose, air of a given excess pressure p was supplied to the measuring cavity, the value of which was recorded by a pressure gauge and a pressure sensor. The values of the pressure sensor signal in the form of voltage V (V) in each mode were recorded by the measuring system. The pressure value from units of measurement mm Hg to kPa was converted based on the relationship:

760 mm Hg = 101.325 kPa

To check the measurement technique for the reliability of the obtained results, measurements of a container of known volume were carried out. A 20-liter water container was used as the volume of the measured space. The diagram of the measuring system is shown in Fig. 2, where a 20-liter container was connected instead of the engine crankcase. The tests were carried out at three values of the flow rate of air entering the container at an excess pressure at the outlet of the reducer of 350 kPa, which made it possible to have a critical outflow and a constant air flow rate when the excess pressure in the measured volume changed to 140 kPa. The results of recording the change in pressure in the system are presented in Table 1.

The arithmetic mean value of the measured volume is 20.1 l and the spread of values for three experiments does not exceed 2% of the measured value, which allows this method to be used to measure the crankcase volume of an internal combustion engine.

The engine crankcase volume was measured with the engine stopped and air supplied from the compressor receiver under excess pressure of 350 kPa. The oil level in the crankcase corresponded to the maximum value mark on the dipstick. Air leaks through the oil filler hole, the dipstick hole, the high-pressure fuel pump and the compressor installed on the engine were eliminated. The possibility of air leakage supplied to the engine crankcase remained through piston rings and unclosed valves in some engine cylinders, depending on the position of the crankshaft during the measurements.

The results of recording the pressure of the supplied air in the crankcase space of the D-240 engine No. 248100 as part of the MTZ-80 tractor are shown in Table 2 at different flow rates of the supplied air.

The results of recording the pressure of the supplied air in the crankcase space of the D-240 engine No. 393170 installed on a brake test stand are shown in Table 3 at different flow rates of the supplied air.

The results of recording the pressure of the supplied air in the crankcase space of the D-243 No. 213436 engine installed on a brake test stand are shown in Table 4 at different flow rates of the supplied air.

The obtained results of measurements of the crankcase volume of the D-240 and D-243 engines show that the measured volume changes from 41.1 l to 51.8 l, and the measured volume depends on the flow rate of the supplied air. This dependence is shown in Fig. 4. It is evident from the presented graph that at an air flow rate of less than 40 l/min, the spread of the obtained values increases and the average value decreases. This nature of the change in the measurement results can be explained by the influence of air leaks from the crankcase, the consideration of which is primitive for the simplicity of calculations, and as a result, at low air flow rates, this assumption leads to a large error.

To reduce the calculation error, it is proposed to use in the analysis only measurements at the flow rate of the supplied air more than 35 l/min. As a result, the average values of the measured volume are obtained:

- for engine D-240 No. 248100 V _k = 48.7 l

- for engine D-240 No. 393170 V _k = 49.8 l

- for engine D-243 No. 213436 V _k = 50.4 l

The spread of the obtained values of the measured crankcase volume is in the range of 48.3…51.8 l. The average value of the volume based on the results of all measurements with the flow rate of the supplied air of more than 35 l/min is V _кcp = 49.95 l. The standard deviation of the results is S _v = 0.88 l. For the significance level of α=0.05, the confidence interval is 0.50 l. Thus, the volume of the measured crankcase space for the studied engines with a probability of 95% is:

V _k = 49.95±0.5 l.

The obtained results on measuring the volume of the crankcase space show that the proposed invention will allow determining the crankcase volume with a probability of 95% and an error of ±1%. Therefore, in the future, when processing the data on determining the consumption of crankcase gases by measuring the pressure in a closed crankcase, the value of the crankcase volume V _c = 50 l was used.

Compared with the prototype, the proposed method will significantly reduce the complexity of the process of measuring volumes of complex shapes, such as the crankcase of an internal combustion engine, and the accuracy of the measurement.

Claims (6)

A method for determining the crankcase volume of an internal combustion engine, characterized in that during the preparatory stage, at the outlet of the receiver, using a gas reducer with the valve closed in the crankcase, a pressure of at least 300 kPa is established, monitoring using a pressure gauge, then an air flow rate of at least 40 l/min is ensured by opening the valve to the required value, monitoring with an air flow meter, after establishing the required air flow mode and turning on the pressure recording system, the process of recording the time and pressure in the crankcase is turned on using a pressure sensor, at the measuring stage, the air outlet valve is closed and upon reaching the specified pressure within 1 minute, the rate of pressure increase in the crankcase is continued to be recorded, based on the results of the measurements obtained, the amount of air leaks is determined and the crankcase volume is calculated using the formula , where V _k is the crankcase volume; ΔV - volume of air entering the crankcase; Δp - pressure drop in the crankcase depending on the amount of incoming air; p ₂ - crankcase pressure.