JP2014005817A - Uniflow scavenging two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a uniflow scavenging two-cycle engine for enabling consistently normal operation while avoiding abnormal combustion.SOLUTION: A uniflow scavenging two-cycle engine includes: an exhaust port 116 provided at one end in a stroke direction of a piston 112 in a cylinder 110 for exhausting exhaust gas; an exhaust valve 120 for opening/closing the exhaust port; an exhaust control part 154 for opening/closing the exhaust valve; a scavenging port 122 provided in an inner peripheral face on the another end side in the stroke direction of the piston in the cylinder for sucking active gas into a combustion chamber 140 depending on sliding operation of the piston; a fuel injection valve 128 for injecting fuel gas into the active gas to generate pre-mixed gas; and a blow-back detection part 132 for detecting such blow-back that the exhaust gas generated by the combustion behavior of the pre-mixed gas is exhausted via the scavenging port to the outside of the cylinder. The exhaust control part makes a valve opening timing of the exhaust valve earlier when the blow-back is detected than when the blow-back is not detected.

Description

  The present invention relates to a uniflow scavenging two-cycle engine that burns a premixed gas generated by injecting fuel gas into active gas sucked from a scavenging port.

  A uniflow scavenging two-cycle engine (two-stroke engine) also used as a marine engine is provided with an exhaust port at one end of the cylinder in the stroke direction of the piston and a scavenging port at the other end of the cylinder in the stroke direction of the piston. It has been. Then, when the active gas is sucked into the combustion chamber from the scavenging port during the intake (supply) stroke, the exhaust gas generated by the combustion action is exhausted by being pushed out of the exhaust port by the sucked active gas. At this time, a fuel gas is injected into the sucked active gas to generate a premixed gas, and a combustion action is obtained by compressing the generated premixed gas. The piston is caused by an explosion pressure generated by the combustion action. It will reciprocate in the cylinder.

  In such a uniflow scavenging two-cycle engine, for example, as shown in Patent Documents 1 and 2, an exhaust valve that opens and closes an exhaust port is provided. Valve opening timing and valve closing timing are controlled. It is desirable to open the exhaust valve early considering that exhaust gas is surely discharged in the exhaust stroke and the exhaust gas is not retained. On the other hand, if the opening timing of the exhaust valve is advanced, the cylinder The internal pressure will decrease, and the engine output will decrease. Therefore, in consideration of engine efficiency, it is desirable to delay the opening timing of the exhaust valve as much as possible within the range in which the exhaust gas does not stay in the cylinder in the opening / closing control of the exhaust valve.

Japanese Patent Laid-Open No. 03-061611 Japanese Patent Publication No. 06-035830

  However, if the opening timing of the exhaust valve is delayed as described above, the exhaust gas stays in the cylinder for a long time, and in some cases, the exhaust gas is discharged outside the cylinder through the scavenging port. Blowback can occur. When blowback occurs in this way, the amount of active gas sucked into the cylinder is reduced, for example, exhaust gas once discharged from the scavenging port is again sucked from the scavenging port. The exhaust gas generated by the combustion action is extremely hot compared to the active gas sucked from the scavenging port, but if the intake amount of the low-temperature active gas decreases or the retention amount of the high-temperature exhaust gas increases. If the temperature of the piston end surface increases, abnormal combustion such as knocking or pre-ignition may occur, and normal operation may be difficult.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a uniflow scavenging two-cycle engine that avoids abnormal combustion and enables normal operation at all times.

  In order to solve the above problems, a uniflow scavenging two-cycle engine of the present invention is provided at a cylinder in which a combustion chamber is formed, a piston that slides in the cylinder, and one end of the cylinder in the stroke direction of the piston. An exhaust port that is opened and closed to exhaust the exhaust gas generated in the combustion chamber, an exhaust valve that opens and closes the exhaust port, an exhaust control unit that drives the exhaust valve to open or close the exhaust port, and a cylinder A scavenging port that is provided on the inner peripheral surface on the other end side in the stroke direction of the piston and that sucks the active gas into the combustion chamber according to the sliding operation of the piston, and the active gas sucked into the combustion chamber from the scavenging port is fueled In a uniflow scavenging two-cycle engine equipped with a fuel injection valve that injects gas to generate a premixed gas, exhaust generated by the combustion action of the premixed gas A blowback detection unit that detects blowback of gas discharged outside the cylinder through the scavenging port is further provided, and the exhaust control unit detects blowback when blowback is detected by the blowback detection unit. This is characterized in that the opening timing of the exhaust valve is advanced as compared with the case where it is not performed.

  According to the uniflow scavenging two-cycle engine of the present invention, it is possible to always operate normally while avoiding abnormal combustion.

It is explanatory drawing which shows the whole structure of a uniflow scavenging type 2 cycle engine. It is explanatory drawing which shows operation | movement of each control part. It is a flowchart explaining control by an exhaust control part.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is an explanatory diagram showing the overall configuration of a uniflow scavenging two-cycle engine 100. The uniflow scavenging two-cycle engine 100 of the present embodiment is used for, for example, ships. Specifically, the uniflow scavenging two-cycle engine 100 includes a cylinder 110 (cylinder head 110a and cylinder block 110b), a piston 112, a pilot injection valve 114, an exhaust port 116, an exhaust valve driving device 118, and an exhaust valve. 120, a scavenging port 122, a scavenging chamber 124, a fuel injection port 126, a fuel injection valve 128, a rotary encoder 130, a blowback detector 132, and a combustion chamber 140. (Speed machine) 150, a fuel injection control unit 152, an exhaust control unit 154, and the like.

  In the uniflow scavenging two-cycle engine 100, a piston 112 connected to a cross head (not shown) is slidably reciprocated in a cylinder 110 through four successive strokes of intake (supply), compression, combustion, and exhaust. To do. In such a cross-head type piston 112, the stroke in the cylinder 110 can be formed relatively long, and the side pressure acting on the piston 112 can be received by the cross head, so a uniflow scavenging two-cycle engine The output of 100 can be increased. Further, since the cylinder 110 and a crank chamber (not shown) in which the crosshead is accommodated are isolated, deterioration of contamination can be prevented even when using low quality fuel oil.

  The pilot injection valve 114 is provided in the cylinder head 110a above the top dead center of the piston 112, which is one end of the cylinder 110 in the stroke direction, and injects an appropriate amount of fuel oil at a desired point in the engine cycle. Such fuel oil is spontaneously ignited by the heat of the combustion chamber 140 surrounded by the cylinder head 110a, the cylinder liner in the cylinder block 110b, and the piston 112, and burns in a short time. Therefore, the premixed gas containing the fuel gas can be reliably burned at a desired timing.

  The exhaust port 116 is an opening provided at one end of the cylinder 110 in the stroke direction of the piston 112, that is, at the top of the cylinder head 110 a above the top dead center of the piston 112. It is opened and closed to exhaust the exhaust gas. The exhaust valve driving device 118 opens and closes the exhaust port 116 by sliding the exhaust valve 120 up and down at a predetermined timing. The exhaust gas exhausted through the exhaust port 116 in this manner is supplied to the turbine side of a turbocharger (not shown) and then exhausted to the outside.

  The scavenging port 122 is an opening provided on the inner peripheral surface (the inner peripheral surface of the cylinder block 110 b) on the other end side in the stroke direction of the piston 112 in the cylinder 110, and the cylinder 110 according to the sliding operation of the piston 112. The active gas is inhaled inside. Such an active gas includes an oxidizing agent such as oxygen and ozone, or a mixture thereof (for example, air). The scavenging chamber 124 is filled with active gas (for example, air) pressurized by a compressor of a supercharger (not shown), and the active gas is sucked from the scavenging port 122 with a differential pressure in the scavenging chamber 124 and the cylinder 110. Is done. The pressure in the scavenging chamber 124 can be substantially constant, but when the pressure in the scavenging chamber 124 changes, a pressure gauge is provided in the scavenging port 122, and the fuel gas injection amount, etc., according to the measured value, etc. Other parameters may be controlled.

  The fuel injection port 126 has a predetermined interval on the inner circumferential surface of the cylinder 110 (between the exhaust port 116 and the scavenging port 122) in a substantially circumferential direction (allowing displacement not only in the strict circumferential direction but also in the stroke direction). These are a plurality of openings provided with a gap.

  The fuel injection valve 128 is disposed in each fuel injection port 126 and receives a command from the fuel injection control unit 152, for example, and injects fuel gas obtained by gasifying LNG (liquefied natural gas). Thus, the fuel gas is supplied into the cylinder 110. Further, the fuel gas is not limited to LNG, and for example, gasified LPG (liquefied petroleum gas), light oil, heavy oil, or the like can be applied.

  The rotary encoder 130 is provided in a crank mechanism (not shown) and detects a crank angle signal (hereinafter referred to as a crank angle signal).

The blowback detector 132 is provided in the scavenging chamber 124, and exhaust gas generated in the combustion chamber 140 (inside the cylinder 110) in the combustion stroke is discharged to the scavenging chamber 124 (outside the cylinder 110) via the scavenging port 122. Detects the occurrence of blowback. Specifically, the blowback detector 132 detects components in the exhaust gas generated in the combustion chamber 140 (in the cylinder 110), such as a CO ₂ sensor and a NOx sensor, so that the combustion chamber 140 (in the cylinder 110) is detected. ) To the scavenging chamber 124 is detected.

  The specific configuration of the blowback detector 132 is not particularly limited as long as the blowback detector 132 can detect the inflow of exhaust gas from the combustion chamber 140 (inside the cylinder 110) to the scavenging chamber 124. The temperature of the exhaust gas generated in the combustion chamber 140 (inside the cylinder 110) is higher than that of the active gas sucked from the scavenging chamber 124 into the combustion chamber 140 (inside the cylinder 110). It is also possible to configure the blowback detection unit 132 with a temperature sensor to be detected.

  The governor 150 derives the fuel injection amount based on the engine output command value input from the host control device and the engine speed based on the crank angle signal from the rotary encoder 130 and outputs the fuel injection amount to the fuel injection control unit 152.

  The fuel injection control unit 152 controls the fuel injection valve 128 based on information indicating the fuel injection amount input from the governor 150 and the crank angle signal from the rotary encoder 130.

  The exhaust control unit 154 is based on the signal relating to the fuel injection amount from the fuel injection control unit 152, the crank angle signal from the rotary encoder 130, and the blowback detection signal from the blowback detection unit 132. An exhaust valve operation signal is output to 118. Hereinafter, the operation of each control unit in the engine cycle of the above-described uniflow scavenging two-cycle engine 100 will be described.

  FIG. 2 is an explanatory diagram showing the operation of each control unit. FIG. 2 (a) shows the operation of each control unit under a predetermined operating condition of the engine, and FIG. 2 (b) shows a blowback detected under the same engine operating condition as FIG. 2 (a). The operation of each control unit in the case of being performed is shown. As shown in FIG. 2A, in the exhaust stroke after the combustion stroke, the exhaust port 116 and the scavenging port 122 are in a closed state, and the combustion chamber 140 (inside the cylinder 110) is filled with exhaust gas.

  When the piston 112 descends and approaches the bottom dead center due to the explosion pressure generated by the combustion action of the combustion chamber 140, the exhaust control unit 154 opens the exhaust valve 120 through the exhaust valve driving device 118, and the piston 112 slides. The scavenging port 122 opens according to the operation (t1 shown in FIG. 2A). Then, the active gas is sucked from the scavenging port 122, and the active gas rises while forming a swirl for promoting the mixing of the fuel gas, and pushes the exhaust gas in the combustion chamber 140 (inside the cylinder 110) from the exhaust port 116. .

  Then, in the compression stroke in which the piston 112 rises from the bottom dead center toward the top dead center, the scavenging port 122 is closed and the suction of the active gas is stopped. At this time, the exhaust control unit 154 maintains the exhaust valve 120 in an open state, and the exhaust gas in the combustion chamber 140 (inside the cylinder 110) continues to be exhausted from the exhaust port 116 as the piston 112 rises. . During this time, the fuel injection control unit 152 controls the fuel injection valve 128 to the cylinder 110 based on the information indicating the fuel injection amount input from the governor 150, the engine speed derived from the crank angle signal from the rotary encoder 130, and the like. Fuel gas is injected into the inside.

  As a result, the fuel gas is injected into the active gas sucked from the scavenging port 122, and a premixed gas is generated in the combustion chamber 140 (inside the cylinder 110). Thereafter, when the piston 112 further rises and comes closer to the top dead center than the fuel injection valve 128, the exhaust control unit 154 closes the exhaust valve 120 and closes the exhaust port 116 (see FIG. 2A). T3).

  In this manner, the premixed gas burns in the combustion chamber 140, and thus, exhaust, intake, compression, and combustion stroke are repeated as described above. Here, in the combustion stroke, the exhaust control unit 154 opens the scavenging port 122 to reduce the exhaust gas staying in the combustion chamber 140 (inside the cylinder 110) while ensuring the maximum engine output in one cycle. The exhaust valve 120 is controlled to open at approximately the same timing as. For this reason, when the scavenging port 122 is opened, so-called blowback may occur in which the exhaust gas staying in the combustion chamber 140 (in the cylinder 110) is discharged to the scavenging chamber 124 via the scavenging port 122.

  When blowback occurs, exhaust gas is discharged from the scavenging port 122 to the scavenging chamber 124, so that the amount of active gas sucked into the combustion chamber 140 (in the cylinder 110) decreases or the combustion chamber 140 (in the cylinder 110). Or the amount of exhaust gas staying in the chamber increases. Since the exhaust gas is extremely hot compared to the active gas, if the relative amount of exhaust gas in the combustion chamber 140 (in the cylinder 110) increases, the combustion chamber 140 (in the cylinder 110) becomes too hot, and the piston The temperature of the end surface of 112 becomes high, and abnormal combustion such as knocking or pre-ignition may occur.

  Therefore, in the present embodiment, when blowback is detected by the blowback detection unit 132 in the intake (supply) stroke, as shown in FIG. 2B, in the next exhaust stroke, the exhaust control unit 154 controls the exhaust valve 120 to open earlier. More specifically, in FIGS. 2 (a) and 2 (b), if the engine load condition (operating condition) is constant, the exhaust control unit 154 originally has reached the position where the piston 112 has reached the a1 position. The exhaust valve 120 is controlled to open.

  However, when blowback is detected by the blowback detection unit 132, the exhaust control unit 154 performs exhaust when the piston 112 reaches the a2 position on the top dead center side by a distance L from the a1 position. The valve 120 is controlled to open. That is, the exhaust control unit 154 controls the opening timing of the exhaust valve 120 earlier by the distance L when the blowback is detected by the blowback detection unit 132 than when the blowback is not detected. Will be.

  In this way, if the opening timing of the exhaust valve 120 is advanced when blowback is detected, the pressure in the combustion chamber 140 (inside the cylinder 110) decreases when the scavenging port 122 is opened, and is originally sucked. A sufficient amount of active gas can be sucked into the combustion chamber 140 (inside the cylinder 110). Thereby, subsequent blowback can be avoided and normal operation of the engine can be ensured. Further, at the time of detecting the blowback, the temperature of the combustion chamber 140 (inside the cylinder 110) once increased can be lowered by increasing the intake amount of the active gas more than usual, and the blowback continuously occurs. Can be avoided with certainty. Hereinafter, specific control of the exhaust control unit 154 will be described.

  FIG. 3 is a flowchart for explaining the control by the exhaust control unit 154. The processing shown in FIG. 3 is started when it is determined that the piston 112 has reached the top dead center position based on a signal input from the rotary encoder 130.

(Step S201)
The exhaust control unit 154 refers to the operation state map stored in advance based on the information related to the fuel injection amount input from the fuel injection control unit 152, and the piston 112 that is the timing for opening the exhaust valve 120 is displayed. And the position of the piston 112 (hereinafter simply referred to as the valve closing position) at which the exhaust valve 120 is closed are derived. Although detailed explanation is omitted, in the operation status map, the timing for opening and closing the exhaust valve 120 according to the fuel injection amount (engine load status), that is, the valve opening control for the exhaust valve driving device 118 and The position of the piston 112 when starting the valve closing control is stored. When the fuel injection control unit 152 performs fuel injection control, information related to the injected fuel injection amount is output to the exhaust control unit 154, and the exhaust control unit 154 temporarily stores the input information. When the piston 112 reaches the top dead center position, the valve opening position and the valve closing position are derived with reference to the operation state map based on the stored information relating to the fuel injection amount.

(Step S202)
Next, the exhaust control unit 154 determines whether a blowback detection signal is input from the blowback detection unit 132. As a result, if it is determined that the blowback detection signal is input, the process proceeds to step S204. If it is determined that the blowback detection signal is not input, the process proceeds to step S203.

(Step S203)
If it is determined in step S202 that the blowback detection signal is not input, the exhaust control unit 154 determines that the piston 112 has been opened in step S201 based on the detection signal input from the rotary encoder 130. It is determined whether or not the valve position has been reached. Then, the process waits until the piston 112 reaches the valve opening position. When it is determined that the piston 112 has reached the valve opening position, the process proceeds to step S205.

(Step S204)
On the other hand, if it is determined in step S202 that the blowback detection signal is input, the exhaust control unit 154 determines that the piston 112 is derived in step S201 based on the detection signal input from the rotary encoder 130. It is determined whether or not the position at the top dead center side is reached by a distance L from the opened valve position. Then, the piston 112 waits until it reaches a position on the top dead center side by a distance L from the valve opening position, and determines that the piston 112 has reached a position on the top dead center side by a distance L from the valve opening position. At this point, the process proceeds to step S205.

(Step S205)
In step S205, the exhaust control unit 154 controls the exhaust valve driving device 118 to control the exhaust valve 120 to open. Thereby, when blowback is not detected, the exhaust valve 120 opens at the timing specified in the driving situation map, and when blowback is detected, the timing specified in the driving situation map. The exhaust valve 120 opens at an earlier timing.

(Step S206)
Next, the exhaust control unit 154 determines based on the detection signal input from the rotary encoder 130 whether or not the piston 112 has reached the valve closing position derived in step S201. The process waits until the piston 112 reaches the valve closing position, and moves to step S207 when it is determined that the piston 112 has reached the valve closing position.

(Step S207)
If it is determined in step S206 that the piston 112 has reached the valve closing position, the exhaust control unit 154 controls the exhaust valve driving device 118 to control the exhaust valve 120 to close. As a result, the exhaust valve 120 is closed at the timing specified in the driving situation map.

  As described above, when the blowback is detected, the exhaust valve 120 is opened earlier than when the blowback is not detected, so that the hot exhaust gas stays in the cylinder 110. Therefore, it is possible to avoid abnormal combustion such as knocking or pre-ignition, and normal operation is possible.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  For example, in the above embodiment, when the blowback is detected, the opening position of the exhaust valve 120 is moved by the distance L, regardless of the driving situation, compared to the case where the blowback is not detected. It was. In other words, in the above embodiment, when blowback is detected, the valve opening timing of the exhaust valve 120 is advanced at a constant timing regardless of the operation state. However, for example, the degree to which the opening timing of the exhaust valve 120 is advanced is set in advance according to the operating condition, and the opening timing of the exhaust valve 120 is determined according to the operating condition when the blowback is detected. It is good also as controlling.

  The present invention can be used in a uniflow scavenging two-cycle engine that burns a premixed gas generated by injecting fuel gas into active gas sucked from a scavenging port.

DESCRIPTION OF SYMBOLS 100 ... Uniflow scavenging type 2 cycle engine 110 ... Cylinder 112 ... Piston 116 ... Exhaust port 120 ... Exhaust valve 122 ... Scavenging port 128 ... Fuel injection valve 132 ... Blow back detection part 140 ... Combustion chamber 154 ... Exhaust control part

Claims (1)

A cylinder in which a combustion chamber is formed;
A piston sliding in the cylinder;
An exhaust port provided at one end of the cylinder in the stroke direction of the piston and opened and closed to exhaust exhaust gas generated in the combustion chamber;
An exhaust valve for opening and closing the exhaust port;
An exhaust controller that drives the exhaust valve to open or close the exhaust port;
A scavenging port that is provided on an inner peripheral surface of the cylinder in the stroke direction other end side, and sucks the active gas into the combustion chamber in accordance with the sliding operation of the piston;
A uniflow scavenging two-cycle engine comprising: a fuel injection valve that generates a premixed gas by injecting fuel gas into the active gas sucked into the combustion chamber from the scavenging port;
The exhaust gas generated by the combustion action of the premixed gas further comprises a blowback detector for detecting blowback discharged outside the cylinder through the scavenging port,
The exhaust control unit
A uniflow scavenging two-cycle engine characterized in that when the blowback is detected by the blowback detection unit, the opening timing of the exhaust valve is made earlier than when the blowback is not detected.

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