CN107524514A - A kind of high power to weight ratio heavy oil piston engine of two strokes enters pneumatic buffer and its design method - Google Patents
A kind of high power to weight ratio heavy oil piston engine of two strokes enters pneumatic buffer and its design method Download PDFInfo
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- CN107524514A CN107524514A CN201710610303.9A CN201710610303A CN107524514A CN 107524514 A CN107524514 A CN 107524514A CN 201710610303 A CN201710610303 A CN 201710610303A CN 107524514 A CN107524514 A CN 107524514A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B25/00—Engines characterised by using fresh charge for scavenging cylinders
- F02B25/20—Means for reducing the mixing of charge and combustion residues or for preventing escape of fresh charge through outlet ports not provided for in, or of interest apart from, subgroups F02B25/02 - F02B25/18
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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Abstract
Enter pneumatic buffer and its design method applied to the high power to weight ratio heavy oil piston engine of two strokes the invention provides one kind, buffer is located between the gentle cylinder air inlet of scavenging pump discharge, entirety is multiple cavity volumes of a rectangular-shaped group, inside is without other machineries and moving component, pass through the structural section structure design between multigroup cavity volume, engine is efficiently controlled in scavenging and pollution of the combustion gas to fresh inlet air is flow backwards in cylinder, the combustion gas backflowed out of is again pushed into cylinder, scavenging efficiency is higher, coefficient of scavenging is bigger, and the amount of work of per engine cycle is bigger.
Description
Technical field
The present invention relates to piston engine air inlet buffer structure design field, and in particular to a kind of high power to weight ratio weight of two strokes
Oily piston engine charge buffer design method.
Background technology
With the development of General Aviation, two stroke heavy oil piston engines are gradually valued by people.Two-stroke piston
The performance of engine is had a great influence by ventilation quality, a kind of preferable air exchange system, is as far as possible in small excessive scavenging system
On the premise of number, coefficient of scavenging as big as possible is obtained, reduces the residual gas in the exhaust hood of scavenging completion.
For the aviation piston engine of high power to weight ratio requirement, reaching the construction weight of engine target power should use up
May be low, this requires to optimize engine performance in the case where engine structure weight is not significantly increased, and is advantageously implemented hair
The high power to weight ratio of motivation.
Existing anti-down Flow Technique realizes the one-way flow of fluid using the check valve body device of various designs, structure more,
These structures by several components by mechanical linkage, such as micro- resistance spring structure, it is complicated, difficult design, not only can
Increase the construction weight of machinery, can also the flowing of convection body interfere.
The content of the invention
In view of the above the shortcomings that prior art, it is an object of the invention to provide one kind to be directed to two-stroke Gao Gongchong
Proportion oily piston engine blow-through air enters pneumatic buffer and its design method, for solving cylinder gas reflux pollution new charge
Problem, while obtain higher coefficient of scavenging in the case of identical new charge amount.The present invention is obtained by carrying out theoretical calculation
Go out the parameters of structural dimension of buffer, and the cylinder of the buffer structure and engine is the integrated design, with crankcase one
It is easier in technique with casting processing, it is cheaper in processing cost, it is more prone to realize in production.
Complete technical scheme of the invention includes：
A kind of engine charge buffer, described buffer is located between the gentle cylinder air inlet of scavenging pump discharge, and has
There is at least one structure cavity volume, described structure cavity volume is in engine breathing accommodating the combustion gas flow backwards in cylinder.
Described engine is two-stroke heavy oil piston engine.
Described buffer has multiple structure cavity volumes, and hole is provided with the intersection interface of adjacent cavity as appearance intracavity gas
Inlet and outlet, each cavity volume along the area of section in gas flow direction be more than cavity volume disengaging open area so that buffer with
In the intersecting section of air inlet, buffer there is mutation in the intersecting section of each adjacent cavity.
Described buffer includes the first cavity volume, the second cavity volume and the 3rd cavity volume, wherein the 3rd cavity volume and the second cavity volume with
Scavenging pump discharge directly connects, and is connected between the 3rd cavity volume and the second cavity volume by hole, between the second cavity volume and the first cavity volume
It is connected also by hole, first cavity volume one end connects the second cavity volume, outlet of the other end as crank case gases.
Gas reflux direction gradually expands during the sectional area scavenging of first cavity volume.
It is described enter pneumatic buffer and crankcase integrated design, enter the crankcase integrally casting of pneumatic buffer and engine into
Type.
The volume size of the structure cavity volume is 2.5 times of the volume of cylinder gas reflux gas.
Two-stroke heavy oil piston engine with described buffer.
Using the described high power to weight ratio heavy oil of two-stroke it is piston-engined enter pneumatic buffer carry out air inlet buffering method,
In the normal intake process of engine, the combustion gas in cylinder is flow backwards, combustion gas along the air intake duct that section is gradually expanded to stream
Go out cylinder, the speed of combustion gas gradually subtracts reduction in flow process；
Combustion gas is flowed through after the outlet that crankcase and cylinders connect enters crankcase, first flows through the cavity volume of buffer first,
The section of first cavity volume is gradually expanded, and makes the speed of refluence combustion gas persistently reduce；Combustion gas flows through the first cavity volume afterwards by first
Hole between cavity volume and the second cavity volume is flowed into the second cavity volume, produces throttle effect by aperture, the pressure of gas reduces, and flows
Dynamic loss increase, gas velocity reduce；
Subsequent gas equally produces throttle effect when flowing into three cavity volumes by the second cavity volume, and the pressure and speed for making gas are entered
One step reduces；
Fresh air flows out from scavenging pump discharge, enters crankcase by the 3rd cavity volume and the second cavity volume, the 3rd cavity volume with
Fresh air in second cavity volume together flows through the first cavity volume, the air intake duct entered by the outlet of crankcase on cylinder, finally
Circulated into cylinder as working medium.
The high power to weight ratio heavy oil of described two-stroke it is piston-engined enter pneumatic buffer design method, including following step
Suddenly：
(1) according to the design requirement of engine, the in-cylinder pressure and engine when engine air cylinder intake valve is opened are determined
The gas pressure of supercharger outlet, and determine the gas pressure difference p of gas port both sides when cylinder intake valve is opened1-p2, wherein p1For
Inner pressure of air cylinder, p2For cylinder external pressure；
(2) simplification of incompressible fluid and Steady Flow is carried out to the differential form equation along fluid flow line direction, it is as follows
Shown in formula：
According to simplified condition：V=const, ρ=const,
The incompressible fluid equation along grain direction is obtained, is shown below：
In formula, ρ is gas density, V1For cylinder interior air-flow speed, V2For cylinder outer gas flow rate speed, z1And z2For air inlet
The gas height of mouth both sides；If z1And z2It is equal；
With reference to the pressure differential p of the air inlet both sides described in step (1)1-p2, because the air velocity of cylinder interior is 0,
If V1Equal to 0, V is obtained according to equation2As flow backwards the average refluence speed of combustion gas；
(3) according to the gas expansion rule in cylinder, mathematical description is carried out to gas isentropic expansion process, it is as follows
Shown in formula：
In above formula, v1Gas specific volume when being opened for inlet valve, v2The gas specific volume terminated for gas reflux, n value model
Enclose for 1.32~1.36.
The Bottom Runby of the piston during gas reflux is obtained according to two gas specific volumes, with reference to the cylinder of engine
Footpath, stroke and rotary speed parameter, obtain the refluence time of combustion gas；And to being refluence amount in gas reflux stage gas in the jar decrement
Carry out preliminary it is assumed that the average speed flow backwards according to the refluence amount of hypothesis and the refluence time being calculated.
(4) by being modified to refluence amount so that the calculating knot in refluence average speed and (2) that step (3) obtains
Fruit is consistent；According to the estimation result described in step (3), and obtain revised cylinder and flow backwards combustion gas quality；
(5) gas reflux that is obtained by cylinder diameter, stroke and the rotary speed parameter of gas specific volume combination engine in step (3)
The average refluence speed that duration and step (2) obtain calculates the distance of gas reflux, in this, as the initial of buffer
Length, by the initial cross-section area for flowing backwards combustion gas quality and calculating buffer obtained after being corrected in step (4)；
(6) according to the quality continuity equation of the air inlet open area of buffer and cylinder, and incompressible fluid:
qm=ρ V2A=const
The refluence speed for flowing backwards combustion gas is modified, afterwards length and section of repeat step (3)-(5) to buffer
Area is modified；Q in formulamMass flow during to flow backwards, i.e., the gaseous mass that the unit interval backflows out of from cylinder, A is slow
Rush the area of section of device.
(7) determine to carry out three cavity volumes of inside after the overall profile size of buffer the division in length, ensure to sweep
The gas of air pump outlet enters as far as possible uniform during crankcase, the length of the design cavity volume of cavity volume the 3rd and the second cavity volume along gas flow
It is equal.
The high power to weight ratio heavy oil piston engine of the two-stroke enters pneumatic buffer design method, using pneumatic principle, with reference to hair
The design parameter of motivation intake and exhaust, by the solution to equation, obtain the structural parameters of buffer.Pass through theoretical calculation and structure
Design, can efficiently control the refluence combustion gas in cylinder to the contaminant capacity of new charge, can effectively improve hair
The ventilation quality of motivation, be advantageous to the performance for improving engine and the high power to weight ratio for realizing aviation piston engine.
As described above, present invention one kind high power to weight ratio heavy oil piston engine of two strokes enters pneumatic buffer design method, have
There is following beneficial effect：
Pollution of the combustion gas to fresh inlet air is flow backwards in cylinder 1. efficiently controlling, improves air mass.
2. the combustion gas backflowed out of is again pushed into cylinder, in the case of identical excess coefficient of scavenging, scavenging is participated in
Gaseous mass increase, the coefficient of scavenging of cylinder is bigger.
3. in the case of identical excess coefficient of scavenging, the scavenging efficiency of cylinder is higher, and the residual gas in cylinder is more
Few, fresh air during air inlet in cylinder is more again, and the amount of work of per engine cycle is bigger.
4. in the case where engine structure weight is not significantly increased, the ventilation quality of engine is lifted, makes engine
Performance boost, be advantageous to the raising of engine power to weight ratio.
In summary, the high power to weight ratio heavy oil piston engine of two strokes of the invention enters pneumatic buffer design method, can make
Engine, which efficiently controls, flows backwards pollution of the combustion gas to fresh inlet air in cylinder, ensure the air mass of cylinder, Er Qie
Gas reflux enters after buffer, and this portion gas can again be pushed into cylinder and together carry out scavenging with scavenging gas, in phase
In the case of same excessive coefficient of scavenging, the gaseous mass increase of scavenging is participated in, the coefficient of scavenging of cylinder is bigger, the scavenging of cylinder
More efficient, the residual gas in cylinder is less, and fresh air during air inlet in cylinder is more again, the acting of per engine cycle
Amount is bigger.Because the buffer of the present invention is one group of square cavity volume of length, inside does not contain other mechanical moving elements, Er Qieqi
For design size under the yardstick of ten a few to tens of millimeters, its construction weight is very light, and engine structure weight is not significantly increased this
In the case of amount, the ventilation quality of engine is lifted, makes the performance boost of engine, is advantageous to carrying for engine power to weight ratio
It is high.
Brief description of the drawings
Fig. 1 is scavenging pump discharge schematic diagram.
Fig. 2 is the enterprising pneumatic buffer schematic diagram of crankcase involved in the present invention.
Fig. 3 is the enterprising pneumatic buffer schematic cross-section of crankcase involved in the present invention.
Fig. 4 is crankcase and cylinder contact surface schematic diagram.
Fig. 5 is structural representation of air cylinder.
In figure：1- scavengings pump discharge, the cavity volume of 2- buffers the 3rd, the second cavity volume of 3- buffers 2, the cavity volume of 4- buffers first
3rd, the outlet of 5- crank case gases, 6- inlet cylinders, 7- cylinders.
Embodiment
The present invention will be further described with reference to the accompanying drawings and detailed description.
As shown in figure 1, the pneumatic buffer that enters involved in the present invention is located at after scavenging pump discharge 1.
As shown in Figure 2,3, the pneumatic buffer that enters involved in the present invention includes three gas cavity volumes, i.e. the first cavity volume 4,
Two cavity volumes 3 and the 3rd cavity volume 2.Wherein the 3rd cavity volume 2 and the second cavity volume 3 directly contact with scavenging pump discharge, and the He of the 3rd cavity volume 2
Connected between second cavity volume 3 by a perforate, the second cavity volume 3 is connected with the first cavity volume 4 also by a hole.The cavity volume of gas first
4 one end connect the second cavity volume 3, outlet of the other end as crank case gases.
As shown in Figure 4,5, crankcase outlet 5 is connected with cylinder 7 by the air intake duct 6 of cylinder, realizes the inflow of gas.
In the normal intake process of engine, fresh air flows out from scavenging pump discharge 1, passes through the 3rd cavity volume 2 and
Two cavity volumes 3 enter crankcase, and the fresh air in the 3rd cavity volume 2 and the second cavity volume 3 together flows through the first cavity volume 4, passes through bent axle
The outlet 5 of case is entered the air intake duct 6 on cylinder, is finally entered in cylinder 7 and is circulated as working medium.
When engine works, if expecting preferable cylinder scavenging effect, increase valve overlap is highly effective
Method, after the opening time of preadmission door, pressure ratio admission pressure when can open cylinder intake valve in cylinder is high, in cylinder
Combustion gas can flow backwards.If not using buffer, the combustion gas in cylinder 7 enters crankcase by air intake duct 6, and then continues dirty forward
Contaminate fresh air.Involved in the present invention enters multiple expansion and contraction of the pneumatic buffer using runner in gas flow, makes
The pressure and speed for flowing backwards combustion gas are reduced rapidly, and the combustion gas to outflow is limited in certain area by the cavity volume of certain volume
In domain, slow down the speed that air inlet is polluted forward in combustion gas, so as to control the pollution level to new charge.
When the combustion gas in cylinder 7 is flow backwards, combustion gas is flowed along the air intake duct 6 that section is gradually expanded to outflow cylinder
The speed of combustion gas gradually subtracts reduction during dynamic.It is first after the entrance of outlet 5 crankcase that crankcase connects with cylinders is flowed through in combustion gas
The first cavity volume of buffer 4 is first flowed through, as shown in figure 3, the section of the first cavity volume 4 can so fire refluence also in gradually expansion shape
The speed of gas persistently reduces.Combustion gas is flowed through flows into the after the first cavity volume 4 by the hole between the first cavity volume 4 and the second cavity volume 3
In two cavity volumes 3, as shown in figure 3, throttle effect is produced by aperture when gas flows into the second cavity volume 3 by the first cavity volume 4, gas
Pressure reduces, and flow losses increase, and gas velocity reduces.Similarly, when gas flows into three cavity volumes 2 by the second cavity volume 3
Throttle effect can be produced, the pressure and speed for making gas further reduce.When gas flows through three cavity volumes, speed, pressure can be by
Level reduces.
Illustrate the high power to weight ratio heavy oil piston engine of a kind of two stroke as described herein below by way of specific design procedure
Enter pneumatic buffer design method.Those skilled in the art can be understood the present invention's easily as the content disclosed by this specification
Other advantages and benefit, the present invention can also be embodied or applied by other different embodiments, this specification
In every details can also be based on different viewpoints in application, without departing from the spirit of the present invention carry out various modifications or change
Become.
Fig. 1-5 is referred to, it is necessary to which explanation, diagram presented herein only illustrate according to the present invention in a schematic way
The design method of middle discussion be designed after result.
One kind high power to weight ratio heavy oil piston engine of two strokes of the invention enters pneumatic buffer design method, including following step
Suddenly：
The high power to weight ratio heavy oil of two-stroke it is piston-engined enter pneumatic buffer design method, it is characterised in that including as follows
Step：
(1) according to the design requirement of engine, the in-cylinder pressure and engine when engine air cylinder intake valve is opened are determined
The gas pressure of supercharger outlet, and determine the gas pressure difference p of gas port both sides when cylinder intake valve is opened1-p2, wherein p1For
Inner pressure of air cylinder, p2For cylinder external pressure；
(2) simplification of incompressible fluid and Steady Flow is carried out to the differential form equation along fluid flow line direction, it is as follows
Shown in formula：
Simplified condition：V=const, ρ=const,
The incompressible fluid equation along grain direction is obtained, is shown below：
In formula, ρ is gas density, V1For cylinder interior air-flow speed, V2For cylinder outer gas flow rate speed, z1And z2For air inlet
The gas height of mouth both sides；If z1And z2It is equal；
With reference to the pressure differential p of the air inlet both sides described in step 11-p2, because the air velocity of cylinder interior is 0, if
V1Equal to 0, V can be obtained according to equation2As flow backwards the average refluence speed of combustion gas；
(3) according to the gas expansion rule in cylinder, mathematical description is carried out to gas isentropic expansion process, it is as follows
Shown in formula：
In above formula, v1Gas specific volume when being opened for inlet valve, v2The gas specific volume terminated for gas reflux, n value model
Enclose for 1.32~1.36.
In the exhaust period of engine, the gas pressure in cylinder is constantly reducing, according to the public affairs provided in step (3)
Formula, the original state opened from inlet valve terminate to gas reflux, and the gas pressure in cylinder is gradually decreased down equal to scavenging pressure.
Corresponding to IO Intake Valve Opens and two states terminated are flow backwards, there is corresponding gas specific volume under respective state respectively, and gas ratio
Hold it is relevant with volume of cylinder, i.e., with descent of piston distance dependent.It can be obtained in combustion gas according to the gas specific volume under two states
The Bottom Runby of piston during refluence,
With reference to the cylinder diameter, stroke and rotary speed parameter of engine, you can obtain the refluence time of combustion gas.With reference to being fallen in combustion gas
Stream stage gas in the jar decrement preliminary is it is assumed that duration to gas reflux and averagely flowing backwards speed and estimating；Tool
Body is first assumes the refluence amount of a cylinder, and such as the 10% of combustion gas total amount, the amount is modified again afterwards.According to vacation
If the average speed that can be flow backwards of refluence amount and refluence time for being calculated.
(4) by repeatedly being assumed refluence amount so that what the 3rd step obtained flows backwards in average speed and second step
Result of calculation is consistent.According to the estimation result described in step (3), the refluence combustion gas quality to cylinder carries out primary Calculation；
(5) gas reflux that is obtained by cylinder diameter, stroke and the rotary speed parameter of gas specific volume combination engine in step (3)
The average refluence speed that duration and step (2) obtain calculates the distance of gas reflux, in this, as the initial of buffer
Length, by the initial cross-section area for flowing backwards combustion gas quality and calculating buffer obtained after being corrected in step (3)；
(6) according to the quality continuity equation of the air inlet open area of buffer and cylinder, and incompressible fluid:
qm=ρ V2A=const
The refluence speed for flowing backwards combustion gas is modified, afterwards length and section of repeat step (3)-(5) to buffer
Area is modified；Q in formulamMass flow during to flow backwards, i.e., the gaseous mass that the unit interval backflows out of from cylinder, A is slow
Rush the area of section of device
(7) determine to carry out three cavity volumes of inside after the overall profile size of buffer the division in length, ensure to sweep
The gas of air pump outlet enters as far as possible uniform during crankcase, the length of the design cavity volume of cavity volume the 3rd and the second cavity volume along gas flow
It is equal.
Pass through above-mentioned technology, cylinder can be efficiently controlled ventilation quality, and by improving changing for engine
Makings amount makes the overall performance of engine get a promotion, so that engine is simple and light, is advantageous to engine reality
Existing high power to weight ratio.
It is described above, only it is presently preferred embodiments of the present invention, not the present invention is imposed any restrictions, it is every according to the present invention
Any simple modification, change and the equivalent structure change that technical spirit is made to above example, still fall within skill of the present invention
In the protection domain of art scheme.
Claims (10)
1. a kind of engine charge buffer, it is characterised in that described buffer is located at the gentle cylinder air inlet of scavenging pump discharge
Between, and there is at least one structure cavity volume, described structure cavity volume flows backwards in engine breathing to accommodate in cylinder
Combustion gas.
2. the engine charge buffer described in claim 1, it is characterised in that described engine is the high power to weight ratio of two-stroke
Heavy oil piston engine.
3. the engine charge buffer described in claim 1, it is characterised in that there are described buffer multiple structures to hold
Chamber, hole is provided with the intersection interface of adjacent cavity as the inlet and outlet for holding intracavity gas, each cavity volume is along in gas flow direction
Area of section be more than the disengaging open area of cavity volume so that each adjacent appearance in section that buffer intersects with air inlet, buffer
Mutation be present in the intersecting section of chamber.
4. the engine charge buffer described in claim 1, it is characterised in that described buffer includes the first cavity volume, the
Two cavity volumes and the 3rd cavity volume, wherein the 3rd cavity volume and the second cavity volume directly connect with scavenging pump discharge, and the 3rd cavity volume and second
Connected by hole between cavity volume, be connected between the second cavity volume and the first cavity volume also by hole, first cavity volume one end connection second
Cavity volume, outlet of the other end as crank case gases.
5. the engine charge buffer described in claim 4, it is characterised in that fired during the sectional area scavenging of first cavity volume
Gas backflow direction gradually expands.
6. the engine charge buffer described in claim 1, it is characterised in that it is described enter pneumatic buffer and bent axle it is case integrated
Design, enter the crankcase integrally casting shaping of pneumatic buffer and engine.
7. the engine charge buffer described in claim 1, it is characterised in that it is characterized in that：The appearance of the structure cavity volume
Product size is more than 2.5 times of the volume of cylinder gas reflux gas.
8. the high power to weight ratio heavy oil piston engine of two-stroke with the buffer described in claim any one of 1-5.
9. using the high power to weight ratio heavy oil of two-stroke described in claim any one of 1-7 it is piston-engined enter pneumatic buffer carry out
The method of air inlet buffering, it is characterised in that：In the normal intake process of engine, the combustion gas in cylinder is flow backwards, combustion gas edge
The air intake duct gradually expanded in section to outflow cylinder, the speed of combustion gas gradually subtracts reduction in flow process；
Combustion gas is flowed through after the outlet that crankcase and cylinders connect enters crankcase, first flows through the cavity volume of buffer first, and first
The section of cavity volume is gradually expanded, and makes the speed of refluence combustion gas persistently reduce；Combustion gas flows through the first cavity volume afterwards by the first cavity volume
Hole between the second cavity volume is flowed into the second cavity volume, produces throttle effect by aperture, the pressure of gas reduces, and flows damage
Increase is lost, gas velocity reduces；
Subsequent gas equally produces throttle effect when flowing into three cavity volumes by the second cavity volume, makes the pressure of gas and speed further
Reduce；
Fresh air flows out from scavenging pump discharge, enters crankcase, the 3rd cavity volume and second by the 3rd cavity volume and the second cavity volume
Fresh air in cavity volume together flows through the first cavity volume, the air intake duct entered by the outlet of crankcase on cylinder, finally enters
Circulated in cylinder as working medium.
10. a kind of high power to weight ratio heavy oil of two-stroke described in any one of claim 1-7 it is piston-engined enter pneumatic buffer
Design method, it is characterised in that comprise the following steps：
(1) according to the design requirement of engine, the in-cylinder pressure and engine booster when engine air cylinder intake valve is opened are determined
The gas pressure of device outlet, and determine the gas pressure difference p of gas port both sides when cylinder intake valve is opened1-p2, wherein p1For cylinder
Interior pressure, p2For cylinder external pressure；
(2) simplification of incompressible fluid and Steady Flow is carried out to the differential form equation along fluid flow line direction, such as following formula institute
Show：
<mrow>
<mfrac>
<mrow>
<mo>&part;</mo>
<mi>V</mi>
</mrow>
<mrow>
<mo>&part;</mo>
<mi>t</mi>
</mrow>
</mfrac>
<mi>d</mi>
<mi>s</mi>
<mo>+</mo>
<mfrac>
<mrow>
<mi>d</mi>
<mi>p</mi>
</mrow>
<mi>&rho;</mi>
</mfrac>
<mo>+</mo>
<mi>V</mi>
<mi>d</mi>
<mi>V</mi>
<mo>+</mo>
<mi>g</mi>
<mi>d</mi>
<mi>z</mi>
<mo>=</mo>
<mn>0</mn>
</mrow>
According to simplified condition：V=const, ρ=const,
The incompressible fluid equation along grain direction is obtained, is shown below：
<mrow>
<mfrac>
<msub>
<mi>p</mi>
<mn>1</mn>
</msub>
<mi>&rho;</mi>
</mfrac>
<mo>+</mo>
<mfrac>
<msubsup>
<mi>V</mi>
<mn>1</mn>
<mn>2</mn>
</msubsup>
<mn>2</mn>
</mfrac>
<mo>+</mo>
<msub>
<mi>z</mi>
<mn>1</mn>
</msub>
<mo>=</mo>
<mfrac>
<msub>
<mi>p</mi>
<mn>2</mn>
</msub>
<mi>&rho;</mi>
</mfrac>
<mo>+</mo>
<mfrac>
<msubsup>
<mi>V</mi>
<mn>2</mn>
<mn>2</mn>
</msubsup>
<mn>2</mn>
</mfrac>
<mo>+</mo>
<msub>
<mi>z</mi>
<mn>2</mn>
</msub>
<mo>=</mo>
<mi>c</mi>
<mi>o</mi>
<mi>n</mi>
<mi>s</mi>
<mi>t</mi>
</mrow>
In formula, ρ is gas density, V1For cylinder interior air-flow speed, V2For cylinder outer gas flow rate speed, z1And z2For air inlet both sides
Gas height；If z1And z2It is equal；
With reference to the pressure differential p of the air inlet both sides described in step (1)1-p2, because the air velocity of cylinder interior is 0, if V1
Equal to 0, V is obtained according to equation2As flow backwards the average refluence speed of combustion gas；
(3) according to the gas expansion rule in cylinder, mathematical description is carried out to gas isentropic expansion process, such as following formula institute
Show：
<mrow>
<msub>
<mi>p</mi>
<mn>1</mn>
</msub>
<msubsup>
<mi>v</mi>
<mn>1</mn>
<mi>n</mi>
</msubsup>
<mo>=</mo>
<msub>
<mi>p</mi>
<mn>2</mn>
</msub>
<msubsup>
<mi>v</mi>
<mn>2</mn>
<mi>n</mi>
</msubsup>
</mrow>
In above formula, v1Gas specific volume when being opened for inlet valve, v2The gas specific volume terminated for gas reflux, n span are
1.32~1.36.
The Bottom Runby of the piston during gas reflux is obtained according to two gas specific volumes, cylinder diameter with reference to engine, OK
Journey and rotary speed parameter, obtain the refluence time of combustion gas；And to being that refluence amount is carried out in gas reflux stage gas in the jar decrement
Tentatively it is assumed that the average speed flow backwards according to the refluence amount of hypothesis and the refluence time being calculated.
(4) by being modified to refluence amount so that the result of calculation one in refluence average speed and (2) that step (3) obtains
Cause；According to the estimation result described in step (3), and obtain revised cylinder and flow backwards combustion gas quality；
(5) gas reflux that is obtained by cylinder diameter, stroke and the rotary speed parameter of gas specific volume combination engine in step (3) continues
The average refluence speed that time and step (2) obtain calculates the distance of gas reflux, in this, as the initial length of buffer,
By the initial cross-section area for flowing backwards combustion gas quality and calculating buffer obtained after being corrected in step (4)；
(6) according to the quality continuity equation of the air inlet open area of buffer and cylinder, and incompressible fluid:
qm=ρ V2A=const
The refluence speed for flowing backwards combustion gas is modified, afterwards length and area of section of repeat step (3)-(5) to buffer
It is modified；Q in formulamMass flow during to flow backwards, i.e., the gaseous mass that the unit interval backflows out of from cylinder, A is buffer
Area of section.
(7) determine to carry out three cavity volumes of inside after the overall profile size of buffer the division in length, ensure scavenging pump
The gas of outlet enters as far as possible uniform during crankcase, the length phase of the design cavity volume of cavity volume the 3rd and the second cavity volume along gas flow
Deng.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118309629A (en) * | 2024-06-11 | 2024-07-09 | 耐力股份有限公司 | Piston type air compressor |
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