A method for tuning intake pressure waves of opposed piston engines

Abstract

The invention discloses an intake pressure wave tuning method for an opposed piston engine, belonging to the field of engine technology. The method comprises the following steps: step 1, dividing the propagation path of the intake pressure wave of the opposed piston engine into two sections, wherein the first section of the path is simplified to a combination of a first cavity and a first pipeline, and the second section of the path is simplified to a combination of a second cavity and a second pipeline; step 2, calculating the volume of the first cavity and the length of the first pipeline; step 3, taking the volume of the resonance cavity and the length of the intake pipe behind the resonance cavity as adjustment variables, obtaining the equivalent length of the first section of the path; step 4, calculating the volume of the second cavity and the length of the second pipeline; step 5, calculating the equivalent length of the second section of the path; step 6, calculating the propagation speed of the intake pressure wave in the pipeline; step 7, obtaining the time required for the pressure wave to propagate from the air inlet to the compressor and reflect back to the air inlet, making it equal to the time required for the peak of the intake pressure wave to reach the air inlet, and obtaining the relationship between the two adjustment variables.

Description

Technical Field

[0001] The invention belongs to the technical field of engines, and in particular relates to an intake pressure wave tuning method for an opposed-piston engine. Background Art

[0002] The opposed piston two-stroke engine uses the pressure difference between the intake and exhaust to scavenge, and the intake pressure value has a significant impact on its ventilation quality and even the performance of the whole machine. In the engine intake system, the opening and closing of the air port causes pressure fluctuations in the pipeline. This fluctuation will propagate along the pipeline and be reflected and superimposed. By optimizing the phase of the pressure wave, the intake compression wave reaches the intake port during the opening of the air port, which can increase the intake pressure, thereby increasing the scavenging volume and reducing the residual exhaust gas in the cylinder, increasing the air charge, and helping the engine to achieve higher power output. The geometric parameters of the intake pipe system are the main factors affecting the phase of the pressure wave. By reasonably designing the pipe system parameters, the purpose of increasing the engine charge and power can be achieved.

[0003] At present, there is no method for using intake pressure waves to increase the cylinder charge for opposed piston two-stroke engines. The design of pipe system parameters is generally optimized directly with the performance of the whole machine as the goal through one-dimensional or three-dimensional simulation. The implementation process is complex and the amount of calculation is large. When one of the parameters changes, it often needs to be re-optimized. At present, there is a lack of a relatively simple intake pressure wave tuning method for opposed piston engines, which can improve the engine power by adjusting the phase of the intake pressure wave and obtain the corresponding pipe system parameters. Summary of the invention

[0004] The purpose of the present invention is to provide an intake pressure wave tuning method for an opposed-piston engine, taking the volume of the resonance cavity and the length of the intake pipe behind the resonance cavity as adjustment variables, and obtaining a relationship between the two, so that the intake reflected compression wave reaches the intake port during the opening of the intake port, thereby increasing the intake pressure and thereby increasing the engine charge and power.

[0005] To achieve the above object, the present invention provides an opposed-piston engine intake pressure wave tuning method, comprising the following steps:

[0006] Step 1, dividing the propagation path of the intake pressure wave of the opposed piston engine into two sections, the first section of the path is simplified to a combination of a first cavity and a first pipe, and the second section of the path is simplified to a combination of a second cavity and a second pipe;

[0007] Step 2: Calculate the volume of the first cavity and the length of the first pipe ;

[0008] Step 3: The volume of the resonant cavity and the length of the intake pipe after the resonance cavity As a control variable, the equivalent length of the first path is obtained ;

[0009] Step 4: Calculate the volume of the second chamber and the length of the second pipe ;

[0010] Step 5: Calculate the equivalent length of the second path ;

[0011] Step 6: Calculate the propagation speed of the intake pressure wave in the pipe ;

[0012] Step 7: Obtain the time required for the pressure wave to propagate from the air inlet to the compressor and reflect back to the air inlet , so that it is consistent with the time required for the peak of the intake pressure wave to reach the intake port equal to obtain the adjustment variable and The relationship between .

[0013] Preferably, the first path includes the air intake cavity and the air duct, the resonance cavity, and the air intake pipe after the resonance cavity; the first cavity specifically includes the air intake cavity and the air duct and the resonance cavity; and the first pipe is specifically the air intake pipe after the resonance cavity.

[0014] Preferably, the second path includes an intercooler and an air intake pipe after the intercooler; the second cavity is specifically the intercooler, which is simplified as the second pipe is specifically the air intake pipe after the intercooler.

[0015] Preferably, the volume of the first cavity in step 2 is and the length of the first pipe The calculation expression is as follows:

[0016]

[0017]

[0018] In the formula, is the number of engine cylinders, is the cylinder center distance, is the air cavity thickness, Air cavity height, is the airway width, is the airway height, is the volume of the resonant cavity, is the length of the air intake pipe after the resonance cavity.

[0019] Preferably, the equivalent length of the first path in step 3 is The calculation expression is as follows:

[0020]

[0021] In the formula, is the diameter of the air intake pipe after the resonance cavity.

[0022] Preferably, the volume of the second chamber in step 4 is and the length of the second pipe The calculation expression is as follows:

[0023]

[0024]

[0025] In the formula, is the number of intercooler flow channels, is the cross-sectional area of ​​each flow channel, is the length of the intercooler, is the length of the intake pipe after the intercooler.

[0026] Preferably, the equivalent length of the second path in step 5 is The calculation expression is as follows:

[0027]

[0028] In the formula, is the diameter of the intake pipe after the intercooler.

[0029] Preferably, the propagation speed of the intake pressure wave in the pipeline in step 6 is The calculation expression is as follows:

[0030]

[0031] In the formula, is the specific heat ratio, ; is the average intake pressure; Environmental pressure; is the ambient sound speed, Calculate, where is the air gas constant, , is the ambient temperature.

[0032] Preferably, in step 7, the time required for the pressure wave to propagate from the air inlet to the compressor and reflect back to the air inlet is obtained. , so that it is consistent with the time required for the peak of the intake pressure wave to reach the intake port equal to obtain the adjustment variable and The specific content of the relationship between is as follows:

[0033] The time it takes for a pressure wave to travel from the inlet to the compressor and reflect back to the inlet for:

[0034] According to the three-peak and three-trough characteristics of the intake pressure wave, the time required for the peak of the intake pressure wave to reach the intake port is calculated. for:

[0035]

[0036] In the formula, is the engine speed;

[0037] according to , get the adjustment variable and The relationship is:

[0038]

[0039] in, The value of and is an integer.

[0040] Therefore, the present invention adopts the above-mentioned opposed-piston engine intake pressure wave tuning method, which has the following beneficial effects:

[0041] (1) The design of the resonant cavity volume and the length of the intake pipe behind the resonant cavity can be realized, and one parameter can be determined based on the other parameter under the limitation of the actual layout space of the engine;

[0042] (2) The phase of the reflected compression wave is adjusted by using the volume of the resonance cavity and the length of the intake pipe behind the resonance cavity so that it reaches the intake port during the ventilation period, thereby increasing the intake pressure and thus increasing the engine charge and power;

[0043] (3) There is no need for complex one- or three-dimensional modeling, simulation, and optimization calculations; the steps are simple and the calculation cost is low.

[0044] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is an overall flow chart of an opposed piston engine intake pressure wave tuning method of the present invention;

[0046] Figure 2 The propagation path of the intake pressure wave and a simplified schematic diagram of an embodiment of the present invention;

[0047] Figure 3 A schematic diagram of the air cavity and airway dimensions of an embodiment of the present invention;

[0048] Figure 4 Schematic diagram of the time required for the wave crest to return to the air inlet according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] See also Figure 1-4 , a method for tuning intake pressure waves of an opposed piston engine, comprising the following steps:

[0051] Step 1: Divide the propagation path of the intake pressure wave of the opposed piston engine into two sections, the first section is simplified to the combination of the first cavity and the first pipe, and the second section is simplified to the combination of the second cavity and the second pipe; the first section includes the intake cavity and the airway, the resonance cavity, and the intake pipe after the resonance cavity; the first cavity specifically includes the intake cavity and the airway and the resonance cavity; the first pipe is specifically the intake pipe after the resonance cavity. The second section includes the intercooler and the intake pipe after the intercooler; the second cavity is specifically simplified to the intercooler, and the second pipe is specifically the intake pipe after the intercooler.

[0052] Step 2: Calculate the volume of the first cavity and the length of the first pipe ; The specific expression is as follows:

[0053]

[0054]

[0055] In the formula, is the number of engine cylinders, is the cylinder center distance, is the air cavity thickness, Air cavity height, is the airway width, is the airway height, is the volume of the resonant cavity, is the length of the air intake pipe after the resonance cavity.

[0056] Step 3: The volume of the resonant cavity and the length of the intake pipe after the resonance cavity As a control variable, the equivalent length of the first path is obtained ; The specific calculation expression is as follows:

[0057]

[0058] In the formula, is the diameter of the air intake pipe after the resonance cavity.

[0059] Step 4: Calculate the volume of the second chamber and the length of the second pipe ; The specific calculation expression is as follows:

[0060]

[0061]

[0062] In the formula, is the number of intercooler flow channels, is the cross-sectional area of ​​each flow channel, is the length of the intercooler, is the length of the intake pipe after the intercooler.

[0063] Step 5: Calculate the equivalent length of the second path ; The specific calculation expression is as follows:

[0064]

[0065] In the formula, is the diameter of the intake pipe after the intercooler.

[0066] Step 6: Calculate the propagation speed of the intake pressure wave in the pipe ; The specific calculation expression is as follows:

[0067]

[0068] In the formula, is the specific heat ratio, ; is the average intake pressure; Environmental pressure; is the ambient sound speed, Calculate, where is the air gas constant, , is the ambient temperature.

[0069] Step 7: Obtain the time required for the pressure wave to propagate from the air inlet to the compressor and reflect back to the air inlet , so that it is consistent with the time required for the peak of the intake pressure wave to reach the intake port equal to obtain the adjustment variable and The relationship between them is as follows:

[0070] The time it takes for a pressure wave to travel from the inlet to the compressor and reflect back to the inlet for:

[0071] According to the three-peak and three-trough characteristics of the intake pressure wave, the time required for the peak of the intake pressure wave to reach the intake port is calculated. for:

[0072]

[0073] In the formula, is the engine speed;

[0074] according to , get the adjustment variable and The relationship is:

[0075]

[0076] in, The value of and is an integer.

[0077] Example

[0078] The object of this embodiment is a three-cylinder opposed piston two-stroke engine, , air cavity thickness , air cavity height , airway width , airway height , the volume of the first chamber is obtained as , the first pipe length The diameter of the air intake pipe after the resonance cavity is , the equivalent length expression of the first path is .

[0079] Number of flow channels of intercooler , flow channel cross-sectional area , intercooler length , and the volume of the second chamber is obtained . Length of the air intake pipe after the intercooler , get the second pipe length . Diameter of the air intake pipe after the intercooler , get the equivalent length of the second path .

[0080] In this embodiment, the average intake pressure , environmental pressure , ambient temperature , specific heat ratio , air gas constant , calculate the ambient sound speed , the propagation speed of the intake pressure wave in the pipe .

[0081] The engine speed is , so that the intake compression wave reaches the intake port during the ventilation period, and the resonance cavity volume is obtained and the length of the intake pipe after the resonance cavity The relationship between , , and then get and The relationship between: When the engine layout space limits the length of the intake pipe after the resonance cavity , the resonant cavity volume can be selected .

[0082] Therefore, the present invention adopts the above-mentioned intake pressure wave tuning method of an opposed-piston engine, takes the volume of the resonance cavity and the length of the intake pipe behind the resonance cavity as adjustment variables, and obtains the relationship between the two, so that the intake reflected compression wave reaches the intake port during the opening of the intake port, thereby increasing the intake pressure and thereby increasing the engine charge and power.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for tuning intake pressure waves of an opposed piston engine, characterized in that: The following steps are involved: Step 1, dividing the propagation path of the intake pressure wave of the opposed piston engine into two sections, the first section of the path is simplified to a combination of a first cavity and a first pipe, and the second section of the path is simplified to a combination of a second cavity and a second pipe; The first path includes the air intake cavity and the airway, the resonance cavity, and the air intake pipe after the resonance cavity; the first volume cavity specifically includes the air intake cavity and the airway and the resonance cavity; the first pipe specifically is the air intake pipe after the resonance cavity; The second path includes an intercooler and an air intake pipe after the intercooler; the second cavity is specifically the intercooler, and the second pipe is specifically the air intake pipe after the intercooler; Step 2: Calculate the volume of the first cavity and the length of the first pipe ; Volume of the first chamber and the length of the first pipe The calculation expression is as follows: In the formula, is the number of engine cylinders, is the cylinder center distance, is the air cavity thickness, Air cavity height, is the airway width, is the airway height, is the volume of the resonant cavity, is the length of the air intake pipe after the resonance cavity; Step 3: The volume of the resonant cavity and the length of the intake pipe after the resonance cavity As a control variable, the equivalent length of the first path is obtained ; The equivalent length of the first path The calculation expression is as follows: In the formula, is the diameter of the air intake pipe after the resonance cavity; Step 4: Calculate the volume of the second chamber and the length of the second pipe ; The volume of the second chamber and the length of the second pipe The calculation expression is as follows: In the formula, is the number of intercooler flow channels, is the cross-sectional area of ​​each flow channel, is the length of the intercooler, is the length of the air intake pipe after the intercooler; Step 5: Calculate the equivalent length of the second path ; The equivalent length of the second path The calculation expression is as follows: In the formula, is the diameter of the air intake pipe after the intercooler; Step 6: Calculate the propagation speed of the intake pressure wave in the pipe ; The propagation speed of the intake pressure wave in the pipe The calculation expression is as follows: In the formula, is the specific heat ratio, ; is the average intake pressure; Environmental pressure; is the ambient sound speed, Calculate, where is the air gas constant, , is the ambient temperature; Step 7: Obtain the time required for the pressure wave to propagate from the air inlet to the compressor and reflect back to the air inlet , so that it is consistent with the time required for the peak of the intake pressure wave to reach the intake port equal to obtain the adjustment variable and The relationship between Moderating variables and The specific content of the relationship between is as follows: The time it takes for a pressure wave to travel from the inlet to the compressor and reflect back to the inlet for: According to the three-peak and three-trough characteristics of the intake pressure wave, the time required for the peak of the intake pressure wave to reach the intake port is calculated. for: In the formula, is the engine speed; according to , get the adjustment variable and The relationship is: in, The value of and is an integer.

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