CN1302200C - Combustion chamber - Google Patents

Abstract

A combustion chamber assembly for use in a diesel engine includes a combustion chamber (14) being defined in a crown (12) of a piston (10), the piston (10) having a central axis (16, 18, 518, 524), the combustion chamber (14) having a center portion defining a post, the center portion being defined at least in part by a portion of a sphere, the sphere having a radius, the origin of the radius lying on the piston central axis (16, 18, 518, 524) and the combustion chamber (14) further having a plurality of curved surfaces having smooth tangential transitions between adjacent smooth surfaces, the smooth surfaces including the spherical center portion and at least one annular surface, the combustion chamber (14) being symmetrical with respect to a combustion chamber longitudinal axis (16, 216, 316, 416). A piston (10) incorporating the aforementioned combustion chamber (14) and a method of forming the combustion chamber (14) are further included.

Description

combustion chamber

Technical field

The invention relates to a combustion chamber designed for a compression ignition (diesel) internal combustion engine. More specifically, the invention relates to a piston having a combustion chamber formed in its top.

Background of the Invention

Attempts have been made to create an ideal flow pattern for the air and fuel charge within the combustion chamber of an internal combustion engine. Effects that must be considered include, but are not limited to, providing adequate power generation, minimizing NOx entrained in the engine exhaust, and minimizing the amount of soot particulate entrained in the engine exhaust.

It is well known that a variety of variables in engine design/operation, such as engine compression ratio, combustion chamber shape, fuel injection spray pattern, and others, changes in any of these variables can have an effect on emissions and power produced.

Unsightly amounts of soot are emitted in the engine exhaust, creating public pressure to clean up diesel engines. Furthermore, the amount of soot entrained within the engine lubricating oil can have a detrimental effect on engine reliability. Soot is very abrasive and can cause high engine wear.

In addition, there is substantial pressure to reduce NOx emissions from engines. Increasingly stringent regulatory requirements have enacted decrees to reduce NOx levels. Generally, a combustor design has been found to be effective in reducing NOx levels while increasing soot levels, and vice versa. Additionally, doing any of the foregoing generally reduces engine torque and power output.

There are many examples of combustion chambers formed on top of pistons. Despite these prior art designs, there remains a need to reduce NOx and reduce entrained soot while maintaining or increasing engine torque and power output.

Summary of Invention

The piston of the present invention substantially satisfies the aforementioned industrial needs. Combustion chambers formed on the piston crown have been shown to reduce soot entrainment and NOx emissions while slightly increasing engine power output. Pistons have been shown to be effective for cylinder heads with two or more valves. Another advantage of the combustion chamber of the present invention is that the combustion chamber is symmetrical with respect to the central axis of the piston, and that the combustion chamber is relatively easy to form at the top of the piston.

The present invention is a combustion chamber assembly for a diesel engine comprising a combustion chamber formed on top of a piston having a central axis, the combustion chamber having a central portion forming a cylinder at least partially formed by a A portion of a sphere is formed, the sphere has a radius, the center of which falls on the central axis of the piston, and the combustion chamber also has a plurality of curved surfaces with smooth tangential transitions between adjacent smooth surfaces comprising a spherical central portion and at least one annular On the other hand, the combustion chamber is symmetrical with respect to the longitudinal axis of the combustion chamber. The invention also includes a piston having the aforementioned combustion chamber assembly and a method of forming the aforementioned combustion chamber.

A brief description of the drawings

Fig. 1 is the sectional view of piston of the present invention;

Figure 2 is a graphical representation of the power of the prior art piston and combustion chamber compared to the power of the piston and combustion chamber of the present invention;

Figure 3 is a graphical representation of the comparison of NOx produced by prior art pistons and combustion chambers and the piston and combustion chamber of the present invention;

Figure 4 is a graphical representation of the comparison of the soot produced by the prior art piston and combustion chamber and the soot produced by the piston and combustion chamber of the present invention;

Fig. 5 is the sectional view of the piston of the second embodiment of the present invention;

Figure 6 is a graphical representation of the comparison of the power of the prior art piston and combustion chamber with the power of the piston and combustion chamber of the second embodiment of the present invention;

FIG. 7 is a graphical representation of the comparison of NOx produced by the piston and combustion chamber of the prior art and the NOx produced by the piston and combustion chamber of the second embodiment of the present invention;

Figure 8 is a graphical representation of the comparison between the soot produced by the prior art piston and combustion chamber and the soot produced by the piston and combustion chamber of the second embodiment of the present invention;

9 is a cross-sectional view of a piston of a third embodiment of the present invention;

FIG. 10 is a graphical representation of the comparison of NOx produced by the piston and combustion chamber of the prior art and the NOx produced by the piston and combustion chamber of the third embodiment of the present invention;

Fig. 11 is a graphical representation of the comparison between the soot generated by the prior art piston and combustion chamber and the soot generated by the piston and combustion chamber of the third embodiment of the present invention;

12 is a sectional view of a piston and a combustion chamber of a fourth embodiment of the present invention;

Fig. 13 is the pressure B0 of the crank angle for the prior art engine empirical data (a simulation of the same engine to show the validity of the simulation), and a simulation B44a of an engine with the piston and combustion chamber of the fourth embodiment of the present invention icon of

Fig. 14 is a graphic representation of the comparison of NOx produced by the prior art B0 piston and combustion chamber and the NOx produced by the piston and combustion chamber of the fourth embodiment B44a of the present invention;

Fig. 15 is a graphical representation of the comparison between the soot produced by the prior art B0 piston and combustion chamber and the soot produced by the piston and combustion chamber of the fourth embodiment B44a of the present invention;

16 is a sectional view of a piston and a combustion chamber of a fifth embodiment of the present invention;

Fig. 17 is the B0 of Nox produced for the crank angle of prior art engine empirical data (a kind of simulated B0 of the same engine to embody simulation effectiveness, substantially overlapping empirical data), and a fifth embodiment of the present invention An illustration of a simulated B27 of an engine with pistons and combustion chambers; and

Figure 18 is a graphical representation of the comparison of the soot generated by the piston and combustion chamber of the prior art B0 and the soot generated by the piston and combustion chamber of the fifth embodiment B27 of the present invention.

Detailed description of the attached drawings

first embodiment

The piston of the present invention is shown generally at "10" in FIG. 1 . The top 12 portion of the piston 10 forms the top margin of the piston 10 . The combustion chamber 14 of the present invention is formed within the roof 12 . It should be noted that the combustion chamber 14 is symmetrical with respect to the longitudinal axis 16 and that the longitudinal axis 16 coincides with the central axis of the piston 10 . The various radii (R), diameters (D) and heights (H) described below are clearly shown in the depiction of FIG. 1 .

The piston 10 of the present invention is primarily designed for use in heavy duty diesel engines, but is also suitable for use in lighter duty diesel engines. Piston 10 can use 2-valve or multi-valve heads. Ideally, the fuel is injected near the center of the piston and the injection pattern is radially symmetrical. In a preferred embodiment, the injector emits a fuel spray having six fine sprays exiting equiangularly with respect to the axis 16 .

The combustion chamber 14 formed in the crown 12 of the piston 10 is composed of curved surfaces including spherical surfaces and toroidal surfaces. A spherical surface is represented by radius RS, and a toroidal surface is represented by radius R. Combustion chamber 14 has no flat surfaces. There is a smooth, tangential transition between the various curved surfaces forming the combustion chamber 14, as will be described in more detail below.

In general, the combustion chamber 14 is composed of two spherical surfaces RS1 and RS2, the spherical surface RS1 forming a central sphere 17 . The two spherical surfaces RS1 and RS2 are connected by an annular surface R1 at the bottom of the combustion chamber 14 . The spherical surface RS2 transitions to the piston top 12 from two annular surfaces R2, R3, the annular surfaces have a relatively small curvature and form a cavity connection with the top 12. The diameter dimension is shown as D and the height dimension as H.

There are a number of parameters that control the geometry of the combustion chamber 14, thereby controlling diesel engine combustion performance as well as NOx and soot emissions. A portion of the spherical surface formed by the radius RS1 is located in the central space (central portion) of the combustion chamber 14 . The center 18 of the spherical surface RS1 lies on the central axis 16 of the piston 10 . The distance between the center 18 of the spherical surface RS1 and the intersection of the axis 16 and the bottom surface 20 of the combustion chamber 14 is equal to or greater than 0 and should be less than 0.25D2. As depicted in FIG. 1 , the center of the sphere 18 is at the intersection 22 of the axis 16 of the combustion chamber 14 and the bottom surface 20 of the combustion chamber 14 . In other words, the center of the ball 18 coincides with the point of intersection 22 . This is the preferred disposition of the center 18 at the intersection 22 of the axis 16 of the combustion chamber 14 and the bottom surface 20 of the combustion chamber, but there may also be a vertical height distance between the center 1 and the intersection 22 .

The second spherical surface with radius RS2 is located outside the first (central part) spherical surface RS1 and forms partly an outer margin of the combustion chamber 14 . The outer margin sphere RS2 has a center 23 on the central axis 16 . The distance between the corresponding two centers 22, 23 of the central partial sphere RS1 and the outer margin sphere RS2 is equal to or greater than 0.0 and less than ±2 (R1). Preferably, said distance is zero, and the two centers of spheres 22 , 23 are concentric, and preferably located at the intersection of the central axis 16 of the combustion chamber 14 and the bottom surface 20 . It should be noted that the distance value is positive when the ball center 23 is raised relative to the ball center 22, and FIG. 1 shows a positive distance H1. In addition, the ratio of RS2/RS1 is equal to or greater than 1.0 and less than 3.0. RS2/RS1 is preferably about 2.0, especially 2.073.

The following ratios define certain parameters of the combustion chamber 14 .

a. The ratio of RS1/D2 is greater than 0.10 and less than 0.45, and preferably 0.253.

b. The ratio of D2/D1 is greater than 0.45 and less than 0.85, and preferably 0.619.

c. The ratio of D3/D2 is greater than 0.75 and less than 0.95, and preferably 0.849.

d. The ratio of H/D2 is greater than 0.15 and less than 0.45, and preferably 0.337.

e. The ratio of R1/D2 is greater than 0.11 and less than 0.45, and preferably 0.136.

f. The ratio of R2/D2 is greater than 0.0 and less than 0.35, and preferably 0.11.

g. The ratio of R3/D2 is greater than 0.0 and less than 0.2, and preferably 0.14.

The combustion chamber 14, as previously described, is composed of a combination of spherical and toroidal surfaces. It should be noted that the transition between RS1 and R1 is smooth and tangential, the transition between R1 and RS2 is smooth and tangential, the transition between RS2 and R2 is smooth and tangential, and the transition between R2 and R3 The transitions between are smooth and tangential. Therefore, there is no flat surface to form the combustion chamber 14 . The curves and smooth transitions as previously described promote smooth flow within the combustion chamber 14 and serve to reduce heat loads within the combustion chamber 14 . Furthermore, the combustion chamber 14 is symmetrical with respect to the axis 16 . Thus, it is much easier to turn the combustion chamber 14 than an asymmetrical combustion chamber formed within a piston.

It should also be appreciated that the radii R2, R3 where they intersect the roof 12 form a concave combustion chamber 14, distinct from the open combustion chambers described in some prior art.

The improvement in combustion performance and the reduction in pollutant emissions are shown in Figures 2-4. Referring to Figure 2, the power output is the area under each curve. A first actual experiment with a known combustion chamber is shown by curve 24 . Near the peak of curve 24 , simulated trajectories for known combustion chambers result in curve 24 closely overlapping curve 24 . Trace 26 closely overlapping curve 24 confirms the correctness of the simulation. Next, this same simulation was used to simulate the performance of the combustor 14 . A simulation of combustion chamber 14 is shown by curve 28 . It should be noted that the area below curve 28 is slightly larger than the area below curve 24, indicating that the output from the combustion chamber 14 is slightly greater than the known power output of the combustion chamber.

Figure 3 shows the NOx produced by a known combustor (shown as line 26) and the simulation results for NOx produced by the combustor 14 of the present invention (shown as line 28). It should be noted that the NOx produced by the combustor 14 of the present invention is significantly less than the NOx produced by the known combustor shown by line 6 .

FIG. 4 shows simulated soot generated by a known combustor (shown as line 26 ) compared to simulated soot generated by the combustor 14 of the present invention (shown by line 28 ). It should be noted that the soot produced by the combustor 14 of the present invention is significantly less than that produced by known combustors. It should be clearly noted with reference to Figures 2-4 that the combustor 14 results in an increase in power output while reducing the NOx and soot produced by the combustor compared to known combustors.

second embodiment

The piston of the present invention is shown generally at "210" in FIG. The top 212 portion of the piston 210 forms the top margin of the piston 210 . The combustion chamber 214 of the present invention is formed in the top 212 . It should be noted that the combustion chamber 214 is symmetrical about the longitudinal axis 216 and that the longitudinal axis 216 coincides with the central axis of the piston 210 . The various radii (R), diameters (D) and heights (H) described below are clearly shown in the depiction of FIG. 5 .

The piston 210 of the present invention is primarily designed for use in heavy duty diesel engines, but is also suitable for use in lighter duty diesel engines. Piston 210 can use 2-valve or multi-valve heads. Ideally the fuel is sprayed near the center of the piston and the spray pattern is radially symmetrical. In a preferred embodiment, the injector emits a fuel spray having six fine sprays that discharge equiangularly with respect to the axis 216 .

The combustion chamber 214 formed in the top 212 of the piston 210 is composed of curved surfaces including spherical surfaces and annular surfaces. Combustion chamber 214 has no flat surfaces. There is a smooth, tangential transition between the various curved surfaces forming the combustion chamber 214, described in more detail below.

There are a number of parameters that control the geometry of the combustion chamber 214, thereby enabling control of diesel engine combustion performance as well as NOx and soot emissions. A part of the spherical surface formed by the radius R1 is located in the central space of the combustion chamber 214 and forms a central sphere 217 . The center 218 of the spherical surface R1 is located on the central axis 216 of the piston 210 . The distance between the center 218 of the spherical surface R1 and the intersection of the axis 216 and the bottom surface 220 of the combustion chamber 214 is equal to or greater than 0, and should be less than 0.2D. As depicted in FIG. 5 , the center of the sphere 218 is at the intersection 222 of the axis 216 of the combustion chamber 214 and the bottom surface 220 of the combustion chamber 214 . In other words, the center of the sphere 218 coincides with the intersection point 222 . This is the preferred placement of the center of sphere 218 at the intersection 222 of the axis 216 of the combustion chamber 214 and the bottom surface 220 of the combustion chamber, but there may also be a vertical height distance between the center of sphere 218 and the intersection 222 .

The following ratios define certain parameters of the combustor 214 .

a. The ratio of D1/D is greater than 0.49 and less than 0.81, and preferably 0.6065.

b. The ratio of D2/D1 is greater than 0.81 and less than 0.99, and preferably 0.908.

c. The ratio of H1/D1 is greater than 0.17 and less than 0.47, and preferably 0.344.

d. The ratio of H2/H1 is greater than 0.05 and less than 0.45, and preferably 0.253.

e. The ratio of R1/D1 is greater than 0.13 and less than 0.43, and preferably 0.257.

f. The ratio of R2/D1 is greater than 0.09 and less than 0.25, and preferably 0.133.

g. The ratio of R3/D1 is greater than 0.17 and less than 0.55, and preferably 0.36.

h. The ratio of R4/D1 is greater than 0.08 and less than 0.33, and preferably 0.142.

i. The ratio of R5/D1 is greater than 0.01 and less than 0.02, and preferably 0.14.

Combustion chamber 214 as previously described is composed of a combination of spherical and toroidal surfaces. The spherical surface R1 is formed by the radius R1. The annular surface is formed by radii R2-R5. It should be noted that the transition between the spherical surface R1 and the annular surface R2 is smooth and tangential, the transition between the annular surface R2 and the annular surface R3 is smooth and tangential, and the transition between the annular surface R3 and the annular surface R4 is Smooth and tangential, and the transition between annular surface R4 and annular surface R5 is smooth and tangential. Therefore, there is no flat surface to form the combustion chamber 214 . The curves and smooth transitions as previously described promote smooth flow within the combustion chamber 214 and serve to reduce heat loads within the combustion chamber 214 . Additionally, combustion chamber 214 is symmetrical about axis 216 . Thus, it is much easier to rotate the combustion chamber 214 than an asymmetrical combustion chamber formed within a piston.

It should also be appreciated that faces R3-R5 form a concave combustion chamber 214, distinct from the open combustion chambers described in the prior art.

The improvement in combustion performance and the reduction in pollutant emissions are shown in Figures 6-8. Referring to Figure 6, the power output is the area under each curve. A first actual experiment with a known combustion chamber is shown by curve 224 . Near the peak of curve 224 , simulated trajectories for known combustion chambers yield curve 224 that closely overlaps curve 224 . Trajectory 226 closely overlapping curve 224 confirms the correctness of the simulation. Next, this same simulation was used to simulate the performance of the combustor 214 . A simulation of combustion chamber 214 is shown at curve 228 . It should be noted that the area below curve 228 is slightly larger than the area below curve 224, indicating that the output from the combustion chamber 214 is slightly greater than the known power output of the combustion chamber.

FIG. 7 shows the NOx produced by a known combustor (shown as line 226 ) and the simulation results of NOx produced by the combustor 214 of the present invention (shown by line 228 ). It should be noted that the NOx produced by the combustor 214 of the present invention is significantly less than the NOx produced by the known combustor shown by line 226 .

Figure 8 shows a comparison of simulated soot generated by a known combustor (shown as line 226) and simulated soot generated by the combustor 214 of the present invention (shown by line 228). It should be noted that the soot produced by the combustor 214 of the present invention is significantly less than that produced by known combustors. It should be evident that referring to Figures 6-8, the combustor 214 results in an increase in power output while reducing the NOx and soot produced by the combustor compared to known combustors.

third embodiment

The piston of the present invention and the combustion chamber of the present invention are shown generally at reference numerals "310", "314" in FIG. 9 . Typically, the piston 310 has a centrally located symmetrical upward facing pocket which is used to form a major part of the combustion pan in the cylinder of a diesel engine having a fuel injector for forming a fuel injection stream. Piston 310 can use 2-valve or multi-valve heads. Ideally the fuel is injected near the center of the piston 310 and the injection pattern is radially symmetrical. In a preferred embodiment, the injector emits a fuel spray having six fine sprays that discharge equiangularly with respect to the axis 316 . Piston 310 with combustion chamber 314 effectively reduces diesel engine pollutant emissions such as NOx and soot. Piston 310 is preferably suitable for heavy and medium duty diesel engines.

The top 312 portion of the piston 310 forms the top margin of the piston 310 . A combustion chamber 314 of the present invention is formed within the top 312 . It should be noted that the combustion chamber 314 is symmetrical with respect to a longitudinal axis 316 of the chamber, and that the longitudinal axis 316 coincides with the central axis of the piston 310 . The various radii (R), diameters (D) and heights (H) described below are clearly shown in the depiction of FIG. 9 .

The combustion chamber 314 formed in the top 312 of the piston 310 is composed of curved surfaces including spherical surfaces and annular surfaces. A spherical surface is indicated by radius RS, and a curved surface, which may be a toroid, is indicated by radius R. Combustion chamber 314 has no flat surfaces. There is a smooth, generally tangential transition between the various curved surfaces forming the combustion chamber 314, as will be described in more detail below.

Generally, the combustion chamber 314 is composed of two spherical surfaces RS1 and RS2, RS1 forms a convex spherical surface, and RS2 forms a concave spherical surface. The spherical surface RS1 is formed at the center of the combustion chamber 314 forming a central stub 317, while the spherical surface RS2 is formed radially outside the spherical surface RS1. The two spherical surfaces RS1 and RS2 are connected by a small annular surface with radius R2 at the bottom of the combustion chamber 314 . The combustion chamber side wall is formed by a curved annular surface having a radius R1. The curved sidewall R1 is connected to the spherical surface RS2 by a curved surface with a radius R3. The sidewall curve R1 transitions to an intersection with the top 312 by means of a small curve such as R4 .

There are a number of parameters that control the geometry of the combustion chamber 314, thereby enabling control of diesel engine combustion performance as well as NOx and soot emissions. The convex spherical surface RS1 formed by the radius RS1 is located in the central bottom space (central portion) of the combustion chamber 14 . The center 318 of the spherical surface RS1 lies on the longitudinal axis 316 of the combustion chamber which preferably coincides with the longitudinal axis of the piston 310 . The distance between the center of the sphere 318 of the spherical surface RS1 and the intersection of the axis 316 and the bottom surface 320 of the combustion chamber 314 is equal to or greater than 0 (as shown in Figure 9, the distance measured upwards from the center of the sphere is a positive value), and should be less than 0.3D1 (D1 is the diameter of the piston 310). Said distance is preferably zero, wherein the center of the sphere 318 coincides with the intersection 322 of the bottom surface 320 and the axis 16 .

A concave spherical surface having a diameter RS2 has its center 324 on the axis 316 and, as shown in FIG. 9 , above the piston 310 . The distance between the center 324 of the spherical surface RS2 and the intersection 322 of the bottom surface 320 and the axis 316 is equal to or greater than 1.0D1, and less than 8.0D1, and preferably 2.5D1 (as shown in Figure 9, from the bottom surface 320 and The distance measured upwards from the intersection of axes 316 is a positive value).

The following ratios define certain parameters of the combustion chamber 314, D2 is the maximum diameter of the combustion chamber 314, D3 is the diameter of the combustion chamber 314 at the intersection with the top 312, H1 is the maximum height of the combustion chamber 314, and H2 is The height from the apex of the convex spherical surface RS1 to the top 312 .

a. The ratio of RS1/D2 is greater than 0.11 and less than 0.44, and preferably 0.245.

b. The ratio of RS2/D2 is greater than 1.5 and less than 30.0, and preferably 3.432.

c. The ratio of D2/D1 is greater than 0.42 and less than 0.88, and preferably 0.635.

d. The ratio of D3/D2 is greater than 0.7 and less than 0.995, and preferably 0.832.

e. The ratio of H1/D2 is greater than 0.13 and less than 0.49, and preferably 0.318.

f. The ratio of H2/D2 is greater than 0.005 and less than 0.49, and preferably 0.073.

g. The ratio of R1/D2 is greater than 0.11 and less than 0.65, and preferably 0.412.

h. The ratio of R2/D2 is greater than 0.01 and less than 0.33, and preferably 0.068.

i. The ratio of R3/D2 is greater than 0.01 and less than 0.33, and preferably 0.068.

The curves and smooth transitions of the combustion chamber 314 as previously described promote smooth flow within the combustion chamber 314 and serve to reduce heat loads within the combustion chamber 314 . Additionally, combustion chamber 314 is symmetrical about axis 316 . Thus, it is much easier to rotate the combustion chamber 314 than an asymmetrical combustion chamber formed within a piston.

The improvement in combustion performance and the reduction in pollutant emissions are shown in FIGS. 10 and 11 . FIG. 10 shows simulation results for NOx produced by a known combustor (shown as line 328 ) and NOx produced by the combustor 314 of the present invention (shown by line 330 ). It should be noted that the NOx produced by the combustor 314 of the present invention (line 330 ) is significantly less than the NOx produced by the known combustor shown by line 328 .

Figure 11 shows a comparison of simulated soot generated by a known combustor (shown as line 328) and simulated soot generated by the combustor 314 of the present invention (shown by line 330). It should be noted that the soot generated by the combustor 314 of the present invention (line 330) is significantly less than the soot generated by the known combustor (line 328).

Fourth embodiment

The piston and combustion chamber of the present invention are shown generally in FIG. 12 by reference numerals "410", "414", respectively. Typically, the piston 410 has a centrally located symmetrical upward facing pocket which is used to form part of a complete combustion chamber within the cylinder of a diesel engine. A combustion chamber 414 is formed within the crown 412 of the piston 410 . The engine has a fuel injector for forming a fuel injection flow relative to the combustion chamber 414 . Piston 410 can use 2-valve or multi-valve heads. Ideally the fuel is injected near the center of the piston 410 and the injection pattern is radially symmetrical about the axis 416 . Piston 410 effectively reduces diesel engine pollutant emissions such as NOx and soot (shown in the graphs of FIGS. 14 and 15 ). Piston 410 is preferably suitable for heavy and medium duty diesel engines.

The top 412 portion of the piston 410 forms the top margin of the piston 410 . A combustion chamber 414 of the present invention is formed within the top 412 . It should be noted that the combustion chamber 414 is symmetrical with respect to the combustion chamber longitudinal axis 416 and that the longitudinal axis 416 preferably coincides with the central axis of the piston 410 . The various radii (R), diameters (D) and heights (H) described below are clearly shown in the depiction of FIG. 12 . RS denotes a spherical radius, and a toroidal surface is indicated by a radius R.

The combustion chamber 414 of the piston 410 consists of curved surfaces including spherical surfaces and toroidal surfaces. Combustion chamber 414 has no flat surfaces. There is a smooth, generally tangential transition between the various curved surfaces forming the combustion chamber 414, as will be described in more detail below.

Generally, the combustion chamber 414 is composed of four combinations of three parameters, as shown in FIG. 12, which include:

(1) diameter group (group);

(2) spherical group;

(3) Altitude groups; and

(4) Ring group.

The diameter set includes three diameter parameters, where D1 is the diameter of the piston 410 , D2 is the diameter of the combustion chamber 414 , and D3 is the diameter of the cavity of the combustion chamber 414 where the combustion chamber 414 intersects the crown 412 . The sphere set includes three spheres with radii RS1, RS2 and RS3 respectively. The height group includes three height parameters, where H1 is the depth of the combustion chamber 414 , H2 is the distance between the piston crown 412 and the apex of the convex spherical surface RS1 , and H3 is the thickness of the cavity of the combustion chamber 414 . The set of rings includes three ring faces including radii R1, R2 and R3, respectively.

The convex spherical surface RS1 is located at the center of the bottom of the combustion chamber 414 forming a central stud 417 . The two spherical surfaces RS2 and RS3 respectively form the side walls of the combustion chamber 414 . The two spherical surfaces RS1 and RS2 are connected by an annular surface R1. The annular surface R1 forms the bottom of the combustion chamber 414 . The two spherical surfaces RS2 and RS3 are connected by a small annular surface R2, thus forming a smooth transition between the two spherical surfaces RS2 and RS3. The spherical surface RS3 transitions into the top 412 by means of a small annular surface R3. The centers of the three spherical surfaces RS1 , RS2 and RS3 are all located on the longitudinal axis 416 of the combustion chamber, forming the centerline of the combustion chamber 414 .

The interrelationship of the following parameters controls the geometry of the combustion chamber 14 and the emissions results of a diesel engine using the piston 410 and combustion chamber 414 .

a. The ratio of D2/D1 is greater than 0.43 and less than 0.83, and preferably 0.631.

b. The ratio of D3/D2 is greater than 0.68 and less than 0.998, and preferably 0.883.

c. The ratio of RS1/D1 is greater than 0.08 and less than 0.38, and preferably 0.181.

d. The ratio of RS2/D2 is greater than 0.16 and less than 0.56, and preferably 0.364.

e. The ratio of RS3/D1 is greater than 0.18 and less than 0.48, and preferably 0.282.

f. The ratio of H1/D2 is greater than 0.12 and less than 0.52, and preferably 0.321.

g. The ratio of H2/D1 is greater than 0.006 and less than 0.256, and preferably 0.056.

h. The ratio of H3/D1 is greater than 0.01 and less than 0.45, and preferably 0.05.

i. The ratio of R1/D1 is greater than 0.02 and less than 0.28, and preferably 0.081.

j. The ratio of R2/D1 is equal to or greater than 0 and less than 0.31, and preferably 0.017.

k. The ratio of R3/D1 is equal to or greater than 0 and less than 0.31, and preferably 0.009.

The curves and smooth transitions of the combustion chamber 414 as previously described promote smooth flow within the combustion chamber 414 and serve to reduce heat loads within the combustion chamber 414 . Additionally, combustion chamber 414 is symmetrical about axis 416 . Thus, it is much easier to rotate the combustion chamber 414 than an asymmetrical combustion chamber formed within a piston.

Figure 13 shows a comparison of combustion performance as indicated by in-cylinder pressure, where the area under the pressure curve represents the power output of a diesel engine. It should be appreciated that in Figures 13, 14 and 15, the simulated results of the prior art engine are substantially consistent with the experimental results of the prior art engine, illustrating the accuracy of the simulation. Returning to Fig. 13, the pressure curve B44a of the present invention is slightly larger than the pressure curve B0 of the prior art engine, which illustrates that the performance of the present invention engine is slightly better than the performance of the prior art engine, and the power output of the present invention is higher than that of the prior art The engine is slightly larger.

The improvement in combustion performance and the reduction in pollutant emissions are shown in FIGS. 14 and 15 . Fig. 14 shows the NOx produced by a known combustor (shown as line B0) and the simulation results of NOx produced by the combustor 414 of the present invention (shown as line B44a). It should be noted that the NOx produced by the combustor 414 of the present invention is significantly less than the NOx produced by the known combustor shown by line B0.

Figure 15 shows a comparison of simulated soot produced by a known combustor (shown as line B0) and simulated soot produced by a combustor 414 of the present invention (shown by line B44a). It should be noted that the soot produced by the combustion chamber 414 of the present invention (line B44a) is significantly smaller than the soot produced by the known combustion chamber (line B0).

fifth embodiment

The piston and combustion chamber of the present invention are shown generally in FIG. 16 by reference numerals "510", "512", respectively. Typically, the piston 510 has a centrally located symmetrical upward facing pocket which is used to form part of the combustion chamber within the cylinder of a diesel engine. A combustion chamber 512 is formed in the crown 512 of the piston 510 . The engine has fuel injectors for forming a fuel injection flow relative to the combustion chamber 512 . Piston 510 can use 2-valve or multi-valve heads. Piston 510 effectively reduces diesel engine pollutant emissions such as NOx and soot, as shown graphically in FIGS. 17 and 18 . Piston 510 is preferably suitable for heavy and medium duty diesel engines.

Piston 510 has a symmetrical upward opening combustion chamber 512, which is used to form a major part of a complete combustion chamber in the cylinder of a diesel engine. The engine has a fuel injector for forming a fuel injection stream, so as to reduce such Diesel pollutant emissions of NOx and soot without compromising fuel economy and power output.

The combustion chamber 512 is located within the piston crown 514 of the diesel engine and mainly includes a set of spherical surfaces, as shown in FIG. 16 . Two spherical surfaces RS1 and RS2 with the concentric center 516 on the combustion chamber axis 518 form the main part of the combustion chamber 512 . The inner spherical surface RS1 is located at the center bottom of the combustion chamber 512 to form a short column 520 with a radius of RS1. The outer spherical surface RS2 forms the lower portion of the sidewall of the combustion chamber 512 and has a radius of RS2. A third spherical surface RS3 having a radius RS3 forms the outer bottom margin of the combustion chamber 512 . A fourth sphere RS4 having a radius RS4 forms the higher portion of the sidewall of the combustion chamber 512 .

Four small annular surfaces R1-R4 serve as transition surfaces between adjacent spherical surfaces and connections to the top 514 . The inner spherical surface RS1 and the outer bottom spherical surface RS3 are connected by an annular surface having a radius R1. The lower side wall spherical surface RS2 and the outer bottom spherical surface RS3 are connected by an annular surface with a radius R2. The lower side wall spherical surface RS2 and the upper side wall spherical surface RS4 are connected by an annular surface with a radius R3. The higher sidewall spherical surface RS4 transitions into or rejoins the piston crown 514 via a small annular surface R4 having a radius R4.

The centers of the spherical surfaces RS1 and RS2 coincide with each other, that is, they have a common center 516 , and the common center 516 is located on the central axis 518 of the combustion chamber 512 . The distance between the common center 516 of the spheres RS1 and RS2 and the intersection of the combustion chamber axis 518 and the combustion chamber bottom surface 522 is equal to or greater than 0 and less than 0.28D1, D1 being the diameter of the piston, and preferably 0.073D1. The center of the sphere RS3 is located on the central axis 518 of the combustion chamber, and the distance between the center of the sphere RS3 and the intersection of the axis 518 of the combustion chamber and the bottom surface 522 of the combustion chamber 512 is greater than 0.75D1, and less than 3.0D1, and relatively The best place is 2.178D1. The center of the spherical surface RS4 is located on the central axis 518 of the combustion chamber 512 , and the distance between the center of the spherical surface RS4 and the intersection of the combustion chamber axis 518 and the top 514 of the piston 510 is equal to H3 . The ratio of H3/D1 is greater than 0.02 and less than 0.42, and preferably 0.051.

The central axis 518 of the combustion chamber 512 may coincide with the central axis 524 of the piston 510, or have an offset, that is, the distance H4 between the central axis 518 of the combustion chamber 512 and the central axis 524 of the piston 510 is equal to or greater than 0 , and less than 0.1D1, and preferably 0. Preferably, axes 518 and 524 coincide.

Other relationships of parameters also control the geometry of the combustion chamber as well as the engine's combustion performance and emissions within the engine, as listed below:

1. The ratio of D2/D1 is greater than 0.43 and less than 0.83, and preferably 0.637, and D2 is the maximum diameter of the combustion chamber.

2. The ratio of D3/D1 is greater than 0.33 and less than 0.83, and preferably 0.548, and D3 is the minimum diameter of the combustion chamber.

3. The ratio of RS1/D1 is greater than 0.05 and less than 0.35, and preferably 0.18.

4. The ratio of RS2/D1 is greater than 0.23 and less than 0.53, and preferably 0.334.

5. The ratio of RS3/D1 is greater than 1.18 and less than 4.18, and preferably 2.18.

6. The ratio of RS4/D1 is greater than 0.18 and less than 0.38, and preferably 0.28.

7. The ratio of H1/D1 is greater than 0.1 and less than 0.4, and preferably 0.2, and H1 is the depth of the combustion chamber.

8. The ratio of H2/D1 is greater than 0.04 and less than 0.24, and preferably 0.144, and H2 is the height of the piston.

9. The radius of the annular surface R1 is equal to the radius of the annular surface R2. The ratios of R1/D1 and R2/D1 are both greater than 0.03 and less than 0.25, and preferably 0.051.

10. The radii of the annular surfaces R3 and R4 are very small. Therefore, the ratios of R3/D1 and R4/D1 are both greater than 0 and less than 0.1.

The curves and smooth transitions of the combustion chamber 512 as previously described promote smooth flow within the combustion chamber 512 and serve to reduce heat loads within the combustion chamber 512 . Additionally, the combustion chamber 512 is preferably symmetrical about the piston axis 524 but may be offset by a distance H4 as shown in FIG. 16 . Thus, it is much easier to rotate (form) combustion chamber 512 than to form an asymmetrical combustion chamber within a piston.

It should be recognized that in Figures 17 and 18, the simulation results of the prior art engine are basically consistent with the experimental results of the prior art engine (the empirical trajectory and the simulation trajectory, B0 and B0 basically coincide), which illustrates the accuracy of the simulation. The improvement in combustion performance and the reduction in pollutant emissions are shown in FIGS. 17 and 18 . FIG. 17 shows the NOx produced by a known combustion chamber (shown by line B0 ) and the simulation results of NOx produced by the combustion chamber 512 of the present invention (shown by line B27 ). It should be noted that the NOx produced by the combustor 512 of the present invention is significantly less than the NOx produced by the known combustor shown by line B0.

Figure 18 shows a comparison of simulated soot produced by a known combustor (shown as line B0) and simulated soot produced by a combustor 512 of the present invention (shown by line B27). It should be noted that the soot produced by the combustion chamber 512 (line B27) is significantly smaller than the soot produced by the known combustion chamber (line B0).

Obviously, those skilled in the art will recognize that various other embodiments can be conceived within the scope and breadth of the application in addition to the embodiments described herein. Accordingly, the applicant intends to be limited only by the appended claims.

Claims (14)

1. A piston with a combustion chamber used in a diesel engine comprises: A combustion chamber formed on top of a piston having a central axis, the combustion chamber having a side wall surface and a central portion forming a cylinder at least partially formed by a portion of a sphere having a radius, the center of which falls on the central axis of the piston, the side wall surface is formed by a spherical surface connected to the bottom surface; the combustion chamber also has a number of smooth tangential transitions between adjoining smooth surfaces comprising spherical central portions and On the side wall, the combustion chamber is symmetrical with respect to the longitudinal axis of the combustion chamber. 2. Piston according to claim 1, characterized in that the center of the central partial sphere is located at or below the bottom surface of the combustion chamber. 3. Piston according to claim 2, characterized in that the center of the central partial sphere coincides with the intersection of the bottom surface and the central axis of the piston. 4. Piston according to any one of claims 1, 2 and 3, characterized in that the combustion chamber has no flat surfaces. 5. The piston of claim 1 wherein a curved surface forms a concave surface bordering the top of the piston. 6. The piston according to claim 1, wherein the bottom surface of the combustion chamber is formed by a spherical surface combined with the cylinder. 7. The piston according to claim 1, wherein the bottom surface of the combustion chamber is formed by an annular surface combined with the cylinder. 8. A method of forming a combustion chamber for use in a diesel engine, comprising: forming a combustion chamber on top of a piston having a central axis; forming a cylinder having a central portion of the combustion chamber; the central portion is at least partially formed by a portion of a sphere having a radius; Make the center of the ball set on the central axis of the piston; forming a side wall surface of the combustion chamber with a spherical surface connected to the bottom surface, and also providing a plurality of smooth tangential transitions between adjacent smooth surfaces, the smooth surfaces including the spherical central portion and the side wall surface; and The combustion chamber is arranged symmetrically with respect to the longitudinal axis of the combustion chamber. 9. A method as claimed in claim 8, including providing the center of the central portion of the sphere in or below the floor plane of the combustion chamber. 10. A method as claimed in claim 9, including providing the center of the central partial sphere coincident with the intersection of the base plane and the central axis of the piston. 11. A method as claimed in any one of claims 8, 9, 10, comprising forming the combustion chamber without flat surfaces. 12. The method of claim 8, including forming a concave surface bordering the top of the piston with a curved surface. 13. The method of claim 8, including forming a bottom surface of the combustion chamber from a spherical surface combined with the cylinder. 14. The method of claim 8, including forming a bottom surface of the combustion chamber from an annular surface bonded to the post.

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