METHOD FOR COLLECTING 1-CYCLE DATA FOR OUTPUT MEASUREMENT AND COMBUSTION ANALYSIS OF LARGE-SIZED LOW-SPEED 4-STROKE ENGINE

Abstract

 A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to an embodiment of the present disclosure includes: creating a graph about compression pressure of a predetermined reference cylinder at rotation angles of a crankshaft by blocking fuel for the reference cylinder and collecting compression pressure data from the reference cylinder; creating a graph about pressure change rates of the reference cylinder at rotation angles of the crankshaft by differentiating the compression pressure data collected from the reference cylinder with respect to the rotation angle of the crankshaft; detecting the position of a compression TDC from the graph about the compression change rates of the reference cylinder at the rotation angles of the crankshaft, and storing the rotation angle value of the crankshaft corresponding to the detected position of the compression TDC; determining a start position of an intake/exhaust TDC by adding a rotation angle value of the crankshaft corresponding to 0.5 cycles to the rotation angle value of the crankshaft corresponding to the position of the compression TDC; and collecting compression pressure of the reference cylinder at rotation angles of the crankshaft for one cycle from the start position of the intake/exhaust TDC.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority of Korean Patent Application No. 10-2018-0046998 filed on April 23, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

Field

[0002] The present disclosure relates to a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine and, more particularly, to a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine, the method being able to collect data for one cycle of a large-sized low-speed 4-stroke engine that is applied to ships, etc.

Description of the Related Art

[0003] In general, a ship engine monitoring device is rising as necessary equipment for maintenance of ship engines. In particular, ship engine monitoring devices necessarily require a technology that minimizes measurement errors to perform precise and accurate measurement on engines, and to this end, various measuring technologies have been developed.

[0004] An indicator for measuring the output of ship engines is representative of the measurement technology of ship engine monitoring devices and is classified into a mechanical type and an electronic type.

[0005] A mechanical indicator has been generally used for ships in the related art, and is mounted on a test cock of an engine and performs measurement by drawing the pressure of a combustion chamber on paper and then calculating the area using a measurer called a planimeter. However, the mechanical indicator has a problem that there is an error of around about 10% between the actual state of an engine and the measurement result due to the proficiency of the person who performs measurement and an error of the measurer.

[0006] Accordingly, recently, electronic indicators compensating for the defects of mechanical indicators are generally used.

[0007] An electronic indicator measures the output of a ship engine, unlikely the mechanical indicator, by drawing a volume diagram through sampling on pressure for one cycle of the engine using digital equipment and by automatically calculating the area.

[0008] However, such indicators are generally optimized to measure the output of large-sized low-speed 2-stroke engines, so it is difficult to measure the output of large-sized low-speed 4-stroke engines.

[0009] That is, specific measurement equipment for measuring the combustion state, the output, etc. of large-sized low-speed 4-stroke engines was not developed and the state of engines was measured using a Pmax gauge or various thermometers and pressure gauges mounted on the engines, so it was impossible to measure accurate combustion state and output of engines in the related art.

[0010] On the other hand, four strokes of intake, compression, explosion (expansion), and exhaust for one cycle of large-sized low-speed 4-stroke engines are performed for two revolutions of a crankshaft. Accordingly, the process of starting with an intake stroke, performing compression, explosion, and exhaust strokes, and then starting again an intake stroke is called one cycle. A TDC (Top Dead Center) shows up twice for one cycle and the two TDCs are called an intake/exhaust TDC and a compression TDC (compression/explosion TDC).

[0011] Accordingly, when a Z-pulse is set for a reference cylinder, a TDC and a BDC (Bottom Dead Center) are determined in accordance with the explosion order in large-sized low-speed 2-stroke engines, so it is easy to collect 1-cycle data by mounting and using an angle sensor. However, when collecting 1-cycle data of large-sized low-speed 4-stroke engines, a Z-pulse of an angle sensor is generated twice, so it is difficult to find out a reference Z-pulse and it is also difficult to always collect constant data.

[0012] Further, it is most important to collect 1-cycle data for accurate output and combustion analysis, and particularly, a TDC error of 1 degree causes an output error of 10%, so accurate data collection is most important.

SUMMARY

[0013] The present disclosure has been made in an effort to solve the problems described above and an object of the present disclosure is to provide a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine, the method being able to perform accurate combustion analysis and output measurement of an engine by obtaining accurate 1-cycle data of a large-sized low-speed 4-stroke engine.

[0014] In order to achieve the objects of the present disclosure, a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to an embodiment of the present disclosure includes: creating a graph about compression pressure of a predetermined reference cylinder at rotation angles of a crankshaft by blocking fuel for the reference cylinder and collecting compression pressure data from the reference cylinder; creating a graph about pressure change rates of the reference cylinder at rotation angles of the crankshaft by differentiating the compression pressure data collected from the reference cylinder with respect to the rotation angle of the crankshaft; detecting the position of a compression TDC from the graph about the compression change rates of the reference cylinder at the rotation angles of the crankshaft, and storing the rotation angle value of the crankshaft corresponding to the detected position of the compression TDC; determining a start position of an intake/exhaust TDC by adding a rotation angle value of the crankshaft corresponding to 0.5 cycles to the rotation angle value of the crankshaft corresponding to the position of the compression TDC; and collecting combustion pressure of the reference cylinder at rotation angles of the crankshaft for one cycle from the start position of the intake/exhaust TDC.

[0015] A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to another embodiment of the present disclosure includes: putting a TDC of a predetermined reference cylinder on a TDC marker of a flywheel and matching a Z-pulse signal of an angle sensor to the TDC of the reference cylinder; and collecting combustion pressure data for one cycle by taking an A-pulse or B-pulse signal of the angle sensor as a trigger signal.

[0016] A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to another embodiment of the present disclosure includes: performing setting to recognize Z-pulse signals of an angle sensor, which are generated when a crankshaft is rotated, sequentially as 0 and 1 for one cycle; collecting combustion pressure data for one cycle and determining a TDC at a signal generation point from the collected data; and maintaining or changing signal setting of the angle sensor in accordance with the result of determination, and collecting combustion pressure data for one cycle from a setting position.

[0017] The collecting of combustion pressure data for one cycle and determining of a TDC at a signal generation point from the collected data may determine the TDC at the signal generation point as a compression TDC or an intake/exhaust TDC by comparing an initially collected combustion pressure datum of the combustion pressure data collected for one cycle with predetermined reference pressure.

[0018] The collecting of combustion pressure data for one cycle and determining of a TDC at a signal generation point from the collected data may determine the TDC at the signal generation point as a compression TDC when the initially collected combustion pressure datum is the reference pressure or more.

[0019] The maintaining or changing of signal setting of the angle sensor in accordance with the result of determination, and collecting of combustion pressure data for one cycle from a setting position may: maintain a signal setting order of the angle sensor and collect the combustion pressure data for one cycle sequentially in accordance with the signal setting order of the angle sensor when the TDC at the signal generation point is an intake/exhaust TDC; and change the signal setting order of the angle sensor and collect the combustion pressure data for one cycle sequentially in accordance with the changed signal setting order of the angle sensor when the TDC at the signal generation point is a compression TDC.

[0020] A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to another embodiment of the present disclosure includes: collecting combustion pressure data for 1.5 cycles by taking a predetermined pulse signal of an angle sensor as a start signal; determining a data collection range corresponding to one cycle by comparing an initially collected combustion pressure datum of the combustion pressure data collected for 1.5 cycles with predetermined reference pressure; and collecting the combustion pressure data from the determined data collection range corresponding to one cycle.

[0021] The determining of a data collection range corresponding to one cycle by comparing an initially collected combustion pressure datum of the combustion pressure data collected for 1.5 cycles with predetermined reference pressure may: determine a range from the position where the combustion pressure data are initially collected to the position of a 1 cycle as the data collection range when the initially collected combustion pressure datum is less than the reference pressure; and determine a range from the position of a 0.5 cycle to the position of a 1.5 cycle as the data collection range when the initially collected combustion pressure datum is the reference pressure or more.

[0022] According to embodiments of the present disclosure, accurate combustion analysis and output measurement of an engine are possible by obtaining accurate 1-cycle data of a large-sized low-speed 4-stroke engine.

[0023] Further, since it is possible to obtain 1-cycle data of a large-sized low-speed 4-stroke engine through various methods such as setting a compression TDS and Z-pulse of an angle sensor and comparing initially detected pressure, it is possible to determine accuracy by comparing the obtained 1-cycle data with each other and it is correspondingly possible to improve reliability of work.

[0024] Further, since it is possible to obtain 1-cycle data of a large-sized low-speed 4-stroke engine through a relatively simple method, as compared with the related art, it is possible to improve convenience and workability for an operator and it is also possible to reduce the costs because there is no need for other equipment for obtaining 1-cycle data of a large-sized low-speed 4-stroke engine.

[0025] Further, it is possible to measure the output of an engine and analyze combustion of the engine by providing accurate 1-cycle data of a large-sized low-speed 4-stroke engine, so it is possible to accurately find out the points in time of fuel ignition and fuel injection in cylinders, the fuel injection amount of the cylinders, knocking, the matching relationship between post-combustion and a turbocharger, etc. In addition, it is possible to selectively adjust the point in time of fuel injection, the fuel injection amount, turbocharger matching, etc., by providing a solution for optimum combustion and it is also possible to improve the lifespan and fuel consumption efficiency of an engine by optimizing combustion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a flowchart showing a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to an embodiment of the present disclosure;

FIG. 2 is a graph showing compression pressure of a reference cylinder at rotation angles of a crankshaft;

FIG. 3A is a graph showing pressure change rates of a reference cylinder at rotation angles of a crankshaft and FIG. 3B is a diagram enlarging the portion A of FIG. 3A;

FIG. 4 is a graph arranging the graphs of FIGS. 2 and 3A with reference to the rotation angle of a crankshaft;

FIG. 5 is a flowchart showing a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to another embodiment of the present disclosure;

FIG. 6A is a diagram showing pulses of an angle sensor and FIG. 6B is a diagram showing a table about resolution of an angle sensor and a crank angle;

FIG. 7A is a graph showing combustion pressure at rotation angles of a crankshaft when a compression TDC was detected first for one cycle and FIG. 7B is a graph showing combustion pressure at rotation angles of a crankshaft when an intake/exhaust TDC was detected first for one cycle;

FIGS. 8 and 9 are flowcharts showing a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to another embodiment of the present disclosure;

FIG. 10A is a graph showing combustion pressure at rotation angles of a crankshaft when an intake/exhaust TDC was detected first for 1.5 cycles and FIG. 10B is a graph showing combustion pressure at rotation angles of a crankshaft when a compression TDC was detected first for 1/5 cycles; and

FIG. 11 is a diagram showing a measurement result created by a combustion analysis device for a large-sized low-speed 4-stroke engine, the device performing combustion analysis on a large-sized low-speed 4-stroke engine.

DETAILED DESCRIPTION OF THE EMBODIMENT

[0027] A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine (hereafter, referred to as '1-cycle data collection method') according to an embodiment of the present disclosure is a 1-cycle data collection method. The 1-cycle data collection method can collect data for one cycle of a large-sized low-speed 4-stroke engine that is applied to ships, etc., and is performed by a combustion analysis device (not shown) that can perform combustion analysis and output measurement on a large-sized low-speed 4-stroke engine for one cycle.

[0028] The combustion analysis device (not shown) may include a plurality of sensor units.

[0029] The plurality of sensor units may include a pressure sensor that detects signals about individual compression pressure and combustion pressure of cylinders and an angle sensor that detects a signal about a rotation angle of a crankshaft.

[0030] The pressure sensor is installed at the test cock (not shown) of an engine (E/G) and can detect individual combustion pressure of a plurality of cylinders of the engine. The pressure sensor is electrically connected with a combustion analyzer to be described, so it can transmit signals about the detected individual combustion pressure of the cylinders to the combustion analyzer.

[0031] The angle sensor is installed at an end of the crankshaft of an engine and detects the rotation angle of the crankshaft, and is electrically connected with the combustion analyzer, so it can transmit a signal about the detected rotation angle of the crankshaft to the combustion analyzer. However, the angle sensor is not necessarily installed at an end of the crankshaft of an engine and may be installed on a rotary body (e.g., a camshaft) that rotates with the crankshaft with a predetermined ratio to the crankshaft. The angle sensor may be installed on the flywheel of an engine when a large-sized low-speed 4-stroke engine is used for power generation, and may be installed opposite the flywheel of an engine when a large-sized low-velocity 4-stroke engine is used as a main engine. A Z-pulse (a signal generating a pulse one time for one revolution) of the angle sensor may be matched with the actual TDC of a predetermined reference cylinder. The reference cylinder may mean a first cylinder that is connected with a crankshaft and generates explosion first when an engine is driven. The actual TDC may mean the center point between the moment when a piston reaches the position of a TDC and a dial gauge stops moving and the moment when the dial gauge starts to move again, when the position of a piston is measured by a dial gauge. For reference, the actual TDC is marked on the flywheel of an engine. For example, the angle sensor may be an encoder having a predetermined resolution.

[0032] On the other hand, an AD converter (not shown) that converts analog signals transmitted from the sensors into digital signals may be further provided between the plurality of sensors and the combustion analyzer.

[0033] The combustion analysis device may include the combustion analyzer.

[0034] The combustion analyzer is electrically connected with the plurality of sensors, so it can receive signals about individual combustion pressure of cylinders detected by the sensors and a signal about the rotation angle of a crankshaft and collect combustion pressure of the cylinders at rotation angles of the crankshaft for one cycle of an engine from the received signals.

[0035] The combustion analyzer can analyze combustion chamber volumes and pressure change rates of the cylinders by introducing the collected data into a predetermined expression and show the analysis result in a plurality of graphs about combustion pressure of the cylinders at rotation angles of the crankshaft, about combustion pressure for combustion chamber volumes of the cylinders, and about pressure change rates of the cylinders at rotation angles of the crankshaft.

[0036] Analysis items analyzed by the combustion analyzer, and graphs are described in detail hereafter.

[0037] FIG. 11 is a diagram showing a measurement result created by a combustion analysis device for a large-sized low-speed 4-stroke engine, the device performing combustion analysis on a large-sized low-speed 4-stroke engine.

[0038] Referring to FIG. 11, the combustion analyzer can collect combustion pressure of cylinders at rotation angles of a crankshaft for one cycle of an engine, by taking an A-pulse or B-pulse signal of the angle sensor measuring the rotation angle of the crankshaft as a trigger, and can show the result in a Pθ graph showing the rotation angle of the crankshaft for the cylinders on X-axis and the combustion pressure at the rotation angle on Y-axis. For reference, the crankshaft may be set to rotate 360 degrees per cycle of an engine.

[0039] The combustion analyzer can calculate combustion chamber volumes of the cylinders at rotation angles of the crankshaft, using a predetermined expression, and can show the result in a PV graph showing combustion pressure at the combustion chamber volumes of the cylinders. For reference, a combustion chamber volume, that is, an area in a PV graph may mean the output (indicated horsepower) of a cylinder. Accordingly, the sum of the output of cylinders may mean the output of an engine.

[0040] The combustion analyzer can calculate pressure change rates of the cylinders at the rotation angles of the crankshaft and can show the result in a dP graph showing pressure change rates of the cylinders at the rotation angles of the crankshaft.

[0041] That is, the combustion analyzer, in order to find out fine changes in pressure that are difficult to find out from a Pθ graph, can differentiate the combustion pressure values of the cylinders at the rotation angles of the crankshaft, using a predetermined expression, and show the result in the dP graph.

[0042] The combustion analyzer can further analyze heat generation rates and combustion gas temperature of the cylinders by introducing the data collected from the sensor units into a predetermined expression and can show the analysis result in a plurality of graphs about heat generation rates of the cylinders at rotation angles of the crankshaft and about combustion gas temperature of the cylinders at rotation angles of the crankshaft.

[0043] In detail, the combustion analyzer can calculate heat generation rates of the cylinders at rotation angles of the crankshaft, using a predetermined expression, and can show the result in a heat generation rate graph showing heat generation rates of the cylinders at the rotation angles of the crankshaft.

[0044] The combustion analyzer can calculate combustion gas temperature of the cylinders at rotation angles of the crankshaft, using a predetermined expression, and can show the combustion gas temperature in a combustion gas temperature graph showing combustion gas temperature of the cylinders at the rotation angles of the crankshaft.

[0045] That is, since combustion occurs for a very short time in a combustion chamber, there is a limit in measuring combustion gas temperature in a combustion chamber using existing thermometers. Accordingly, the combustion analyzer can calculate the combustion gas temperature at the rotation angles of the crankshaft using the ideal gas equation of state.

[0046] The combustion analyzer can determine the combustion state of an engine by analyzing at least two or more of a plurality of created graphs.

[0047] In detail, the combustion analyzer can determine a fuel-air ratio state of fuel of cylinders, a fuel injection state of fuel of cylinders, a fuel consumption state of cylinders, a fuel amount state of cylinders, a knocking state of an engine, a post-combustion state of cylinders, and a combustion state of an engine related to at least one of whether the items of maximum combustion pressure of cylinders are matched by analyzing at least two or more of a plurality of graphs.

[0048] The combustion analyzer can further show a table including at least one analysis datum together with a plurality of graphs.

[0049] Referring to FIG. 11, the combustion analyzer can measure the output of an engine and then show the measurement result in a table including at least one datum of the number of revolutions (rpm) of the engine , maximum compression pressure (Pcomp), maximum combustion pressure (Pmax), a crank angle position at maximum combustion pressure, IMEP (Indicated Mean Effective Pressure), IHP (Indicated Horse Power), BHP (Brake Horse Power), ROHR (Rate Of Heat Release), and SFC (Specific Fuel Consumption) for cylinders.

[0050] A method for collecting 1-cycle data according to an embodiment of the present disclosure is described hereafter.

[0051] For reference, components for describing the method for collecting 1-cycle data according to an embodiment of the present disclosure are given the same reference numerals used for describing the combustion analysis device for the convenience of description, and the same or repeated description is not provided.

[0052] First, a method for collecting 1-cycle data according to a first embodiment of the present disclosure is described hereafter.

[0053] FIG. 1 is a flowchart showing a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to an embodiment of the present disclosure and FIG. 2 is a graph showing compression pressure of a reference cylinder at rotation angles of a crankshaft. FIG. 3A is a graph showing pressure change rates of a reference cylinder at rotation angles of a crankshaft, FIG. 3B is a diagram enlarging the portion A of FIG. 3A, and FIG. 4 is a graph arranging the graphs of FIGS. 2 and 3A with reference to the rotation angle of a crankshaft.

[0054] Referring to FIG. 1, the combustion analyzer creates a graph about compression pressure of a predetermined reference cylinder at rotation angles of a crankshaft by blocking fuel for the reference cylinder and collecting compression pressure data from the reference cylinder (S110).

[0055] In detail, the combustion analyzer creates a graph about compression pressure of a predetermined reference cylinder at rotation angles of a crankshaft by blocking fuel for the reference cylinder and collecting data about compression pressure infinitely detected by an angle sensor mounted without specific setting at an end of the crankshaft of the reference cylinder. Accordingly, the combustion analyzer, as shown in FIG. 2, can find out a graph showing the angle of the crankshaft on X-axis and a digital value before converted into an input value on Y-axis. For reference, the cylinder pressure on Y-axis shows a digital value of compression pressure when only air has been compressed.

[0056] The combustion analyzer can remove noise from the collected data to find out accurate positions. For example, the combustion analyzer can configure a high/low pass filter circuit or can perform smoothing through a specific post-processing program to remove noise.

[0057] Next, the combustion analyzer, as shown in FIG. 3A, creates a graph about pressure change rates of the reference cylinder at rotation angles of the crankshaft after differentiating the compression pressure data collected from the reference cylinder with respect to the rotation angle of the crankshaft (S120).

[0058] Next, the combustion analyzer, as shown in FIG. 3B, detects the position of a compression TDC from the graph about the compression change rates of the reference cylinder at the rotation angles of the crankshaft and stores the rotation angle value of the crankshaft corresponding to the detected position of the compression TDC (S130).

[0059] In detail, the combustion analyzer detects the accurate position of a compression TDC by finding out the position of a maximum point (Pcomp) of the compression pressure from the graph about the pressure change rates of the reference cylinder at the rotation angles of the crankshaft, that is, the point where dp/dθ = 0, and stores the rotation angle value of the crankshaft corresponding to the position of the compression TDC. For example, referring to FIGS. 3A and 3B, it can be seen that the compression TDC of the reference cylinder is positioned at 186.6 degrees. That is, this means that the positional relationship between the Z-pulse of the angle sensor and the compression TDC has a difference of 186.6 degrees. For reference, since a loss of angle of a large-sized low-speed 4-stroke engine is ignored, the compression TDC may be the same as the actual TDC.

[0060] The combustion analyzer can offset and store the angle value of the crankshaft corresponding to the position of the compression TDC after detecting the position of the compression TDC and then storing the rotation angle value of the crankshaft corresponding to the detected position of the compression TDC. In detail, the combustion analyzer can measure an angle value of the crankshaft corresponding to position of the compression TDC and then store the values obtained by offsetting a decimal number of the measured angle value. For example, the compression TDC of the reference cylinder shown in FIG. 3B may be stored as 187 degrees from 186.6 degrees through offsetting by the combustion analyzer described above.

[0061] Next, the combustion analyzer determines the start position of an intake/exhaust TDC by adding a rotation angle value of the crankshaft corresponding to 0.5 cycles to the rotation angle value of the crankshaft corresponding to the position of the compression TDC (S140).

[0062] That is, the start position of the intake/exhaust TDC is determined by setting the rotation angle value of the crankshaft corresponding to the compression TDC as a reference point of 0 degree and adding 360 that is the rotation angle value of the crankshaft corresponding to 0.5 cycles to the rotation angle value of the crankshaft that is converted into the intake/exhaust TDC from the compression TDC. Since a large-sized low-speed 4-stroke engine is set to rotate 720 degrees per cycle, 0.5 cycles mean 360 degrees in this case.

[0063] Accordingly, referring to FIGS. 3B and 4, the combustion analyzer determines the position, which is obtained by adding 360 that is the rotation angle value of the crankshaft corresponding to 0.5 cycles to 187 that is the rotation angle value of the crankshaft corresponding to the position of the compression TDC set as 0, as the start position of the intake/exhaust TDC. That is, the combustion analyzer determines the position of 547 degrees, which is a data collection start point, as the start position of the intake/exhaust TDC, by taking the A-pulse of the angle sensor as a start signal.

[0064] Next, the combustion analyzer collects compression pressure of the reference cylinder at rotation angles of the crankshaft for one cycle from the start position of the intake/exhaust TDC (S150).

[0065] In detail, the combustion analyzer determines the start position of the TDC, corrects the angle value of the determined start position of the TDC using an offset value, and then collects compression pressure of the reference cylinder at rotation angles of the crankshaft for one cycle (720 degrees) in accordance with the resolution of the angle sensor from the next angle, by taking 0 degree as the corrected start position of the TDC.

[0066] For reference, the positions of the TDCs of the other cylinders except for the reference cylinders are determined in accordance with the explosion order, the TDCs can be determined by inputting the explosion order. For example, when six cylinders are provided, TDCs can be determined with intervals of 120 degrees in accordance with an explosion order of 1-5-3-6-2-4.

[0067] Accordingly, it is possible to remove the process of setting the Z-pulse signal of an encoder to the reference cylinder, so it is possible to quickly and accurately collect data for one cycle.

[0068] Next, a method for collecting 1-cycle data according to a second embodiment of the present disclosure is described hereafter.

[0069] FIG. 5 is a flowchart showing a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to another embodiment of the present disclosure, FIG. 6A is a diagram showing pulses of an angle sensor, and FIG. 6B is a diagram showing a table about resolution of an angle sensor and a crank angle. FIG. 7A is a graph showing combustion pressure at rotation angles of a crankshaft when a compression TDC was detected first for one cycle and FIG. 7B is a graph showing combustion pressure at rotation angles of a crankshaft when an intake/exhaust TDC was detected first for one cycle;

[0070] Referring to FIG. 5, first, an operator puts a TDC of a predetermined reference cylinder on a TDC marker of a flywheel and matches a Z-pulse signal of an angle sensor to the TDC of the reference cylinder (S210). For reference, referring to FIG. 6A, A-pulse and B-pulse of the angle sensor show the resolution of an encoder and may be used as trigger signals for data collection. The trigger signals may be crank angles. That is, FIG. 6B shows resolution of an angle sensor (encoder), an angle between triggers, and the number of data completing one cycle, which are converted from the resolution. Accordingly, a value obtained by dividing 360 degrees by the resolution can be the angle gap of a crankshaft and a value obtained by counting the angle gap can be a movement angle of the crankshaft.

[0071] For example, the Z-pulse signal of the angle sensor is set to be generated one time for one revolution, so when the Z-pulse signal of the angle sensor shows an up-edge, that is, is 5V, a controller (not shown) on a ship is turned on, and accordingly, the operator can check whether the Z-pulse signal of the angle sensor is matched with the TDC of the reference cylinder.

[0072] Next, the operator collects combustion pressure data for one cycle, by taking the Z-pulse signal of the angle sensor as a start signal and the A-pulse or B-pulse signal of the angle sensor as a trigger signal through the combustion analysis device (S220).

[0073] That is, the Z-pulse of the angle sensor is matched to the TDC of a first cylinder (reference cylinder) and then combustion pressure data for one cycle is collected with the A-pulse or B-pulse of the angle sensor taken as a trigger signal. Since an up-edge follows 90° ± 20 in the B-pulse signal of the angle sensor, the offset value when the B-pulse signal is used as a trigger can be set as 0.25 degrees. It is possible to take up-edges of pulse signals as the reference of a start signal and a trigger signal and take down-edges as the reference.

[0074] Accordingly, the combustion analysis device can construct the graphs of FIGS. 7A and 7B using the data collected in the method described above, and can collect 1-cycle data by sequentially arranging the graphs. For example, a plurality of graphs arranged by the combustion analysis device can be arranged such that an intake/exhaust TDC shows up first and a compression/explosion TDC shows up at the middle.

[0075] Next, a method for collecting 1-cycle data according to a third embodiment of the present disclosure is described hereafter.

[0076] FIG. 8 is a flowchart showing a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to another embodiment of the present disclosure.

[0077] Referring to FIG. 8, a combustion analysis device is set to recognize Z-pulse signals of an angle sensor, which are generated when a crankshaft is rotated, sequentially as 0 and 1 for one cycle (S310).

[0078] In detail, the combustion analysis device is set to recognize a Z-pulse signal of an angle sensor, which is generated at the first TDC of two TDCs detected by the angle sensor when a crankshaft is rotated, as 0 and to recognize a Z-pulse signal of the angle sensor, which is generated at the second TDC of the two TDCs, as 1. Accordingly, signals that are detected from the angle sensor infinitely repeat 0 and 1, and any one of two TDCs is a compression TDC and the other one is an intake/exhaust TDC.

[0079] Next, the combustion analysis device collects combustion pressure data for one cycle and determines a TDC at a signal generation point from the collected data (S320).

[0080] In detail, the combustion analysis device can determine the TDC at a signal generation point as a compression TDC or an intake/exhaust TDC by comparing the initially collected combustion pressure datum of the combustion pressure data collected for one cycle with predetermined reference pressure. For example, when the initially collected combustion datum is the reference pressure or more, the combustion analysis device can determine the TDC at the signal generation point as a compression TDC. The predetermined reference pressure means pressure that is the reference for discriminating scavenging pressure and compression pressure, and the scavenging pressure of most engines is less than 5 bar and the compression pressure according to the compression ratios of diesel engines is usually 20 bar or more, so these pressure values are reference pressure for discriminating an intake/exhaust TDC and a compression TDC. That is, engines using Miller cycle show high scavenging pressure, so the reference pressure can be adjusted in accordance with the scavenging pressure. Accordingly, in order to reduce an error, the average value of initially collected five to ten combustion pressure data is calculated, and the average value can be determined as reference pressure allowing for determining a TDC as an intake/exhaust TDC when it is 5 bar or less and as a compression TDC when it is 20 bar or more. The range of the reference pressure may be adjusted in accordance with a setting and the compression ratio of a turbocharger.

[0081] Next, the combustion analysis device maintains or changes signal setting of the angle sensor in accordance with the result of determining the TDC at the signal generation point and collects combustion pressure data for one cycle from a setting position (S330).

[0082] In detail, when the TDC at the signal generation point is an intake/exhaust TDC, the combustion analysis device can maintain a signal setting order of the angle sensor and collect the combustion pressure data for one cycle sequentially in accordance with the signal setting order of the angle sensor. Further, when the TDC at the signal generation point is a compression TDC, the combustion analysis device can change the signal setting order of the angle sensor and collect the combustion pressure data for one cycle sequentially in accordance with the changed signal setting order of the angle sensor.

[0083] That is, when the TDC at a signal generation point is an intake/exhaust TDC, the combustion analysis device can maintain the current state and collect combustion pressure data for one cycle in accordance with the signal setting order (0 and 1) of the angle sensor. On the other hand, when the TDC at a signal generation point is a compression TDC, the combustion analysis device can change the signal setting order (0 and 1) of the angle sensor in the opposite order (1 and 0) and collect combustion pressure data for one cycle.

[0084] Next, a method for collecting 1-cycle data according to a fourth embodiment of the present disclosure is described hereafter.

[0085] FIG. 9 is a flowchart showing a method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine according to another embodiment of the present disclosure, FIG. 10A is a graph showing combustion pressure at rotation angles of a crankshaft when an intake/exhaust TDC was detected first for 1.5 cycles, and FIG. 10B is a graph showing combustion pressure at rotation angles of a crankshaft when a compression TDC was detected first for 1.5 cycles.

[0086] Referring to FIG. 9, a combustion analysis device collects combustion pressure data for 1.5 cycles, by taking a predetermined pulse signal (Z) of an angle sensor as a start signal (S410). For example, 1.5 cycles may mean 1080 degrees.

[0087] Next, the combustion analysis device determines a data collection range corresponding to one cycle by comparing the initially collected combustion pressure datum of the combustion pressure data collected for 1.5 cycles with predetermined reference pressure (S420).

[0088] When the initially collected combustion pressure datum is less than the reference pressure, as shown in FIG. 10A, the combustion analysis device determines the range from the position where a combustion pressure datum is initially collected to the position of a 1 cycle (720 degrees) as the data collection range when the initially collected combustion pressure datum is less than the reference pressure. On the other hand, when the initially collected combustion pressure datum is the reference pressure or more, as shown in FIG. 10B, the combustion analysis device can determine the range from the position of a 0.5 cycle (360 degrees) to the position of a 1.5 cycle (1080 degrees) as the data collection range.

[0089] Next, the combustion analysis device collects combustion pressure data from the determined data collection range corresponding to one cycle (S430).

[0090] Meanwhile, the method for collecting 1-cycle data may be implemented in a form of program commands that may be executed through various computer means and may be recorded in computer-readable recording media. The recording media may include program commands, data files, data structures, etc. The program commands that are recorded on the recording media may be those specifically designed and configured for the present disclosure or may be those available and known to those engaged in computer software in the art. For example, the recording media may include magnetic media such as hard disks, floppy disks, and a magnetic tape, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specifically configured to store and execute program commands, such as ROM, RAM, and flash memory. The program commands may include not only machine language codes compiled by a compiler, but also high-level language codes that can be executed by a computer using an interpreter. Further, a hardware device may be configured to operate as one or more software modules to perform the operation of the present disclosure.

[0091] Further, the method for collecting 1-cycle data may be implemented as a computer program or an application that is stored on recording media and executed by a computer.

[0092] As described above, according to embodiments of the present disclosure, accurate combustion analysis and output measurement of an engine are possible by obtaining accurate 1-cycle data of a large-sized low-speed 4-stroke engine.

[0093] Further, since it is possible to obtain 1-cycle data of a large-sized low-speed 4-stroke engine through various methods such as setting a compression TDS and Z-pulse of an angle sensor and comparing initially detected pressure, it is possible to determine accuracy by comparing the obtained 1-cycle data with each other and it is correspondingly possible to improve reliability of work.

[0094] Further, since it is possible to obtain 1-cycle data of a large-sized low-speed 4-stroke engine through a relatively simple method, as compared with the related art, it is possible to improve convenience and workability for an operator and it is also possible to reduce the costs because there is no need for other equipment for obtaining 1-cycle data of a large-sized low-speed 4-stroke engine.

[0095] Further, it is possible to measure the output of an engine and analyze combustion of the engine by providing accurate 1-cycle data of a large-sized low-speed 4-stroke engine, so it is possible to accurately find out the points in time of fuel ignition and fuel injection in cylinders, the fuel injection amount of the cylinders, knocking, the matching relationship between post-combustion and a turbocharger, etc. In addition, it is possible to selectively adjust the point in time of fuel injection, the fuel injection amount, turbocharger matching, etc., by providing a solution for optimum combustion and it is also possible to improve the lifespan and fuel consumption efficiency of an engine by optimizing combustion.

Claims

1. A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine, the method comprising:

creating a graph about compression pressure of a predetermined reference cylinder at rotation angles of a crankshaft by blocking fuel for the reference cylinder and collecting compression pressure data from the reference cylinder;

creating a graph about pressure change rates of the reference cylinder at the rotation angles of the crankshaft by differentiating the compression pressure data collected from the reference cylinder with respect to the rotation angle of the crankshaft;

detecting the position of a compression TDC from the graph about the compression change rates of the reference cylinder at the rotation angles of the crankshaft, and storing the rotation angle value of the crankshaft corresponding to the detected position of the compression TDC;

determining a start position of an intake/exhaust TDC by adding the rotation angle value of the crankshaft corresponding to 0.5 cycles to the rotation angle value of the crankshaft corresponding to the position of the compression TDC; and

collecting compression pressure of the reference cylinder at the rotation angles of the crankshaft for one cycle from the start position of the intake/exhaust TDC.

2. A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine, the method comprising:

putting a TDC of a predetermined reference cylinder on a TDC marker of a flywheel and matching a Z-pulse signal of an angle sensor to the TDC of the reference cylinder; and

collecting combustion pressure data for one cycle by taking an A-pulse or B-pulse signal of the angle sensor as a trigger signal.

3. A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine, the method comprising:

performing setting to recognize Z-pulse signals of an angle sensor, which are generated when a crankshaft is rotated, sequentially as 0 and 1 for one cycle;

collecting combustion pressure data for one cycle and determining a TDC at a signal generation point from the collected data; and

maintaining or changing signal setting of the angle sensor in accordance with the result of determination, and collecting the combustion pressure data for one cycle from a setting position.

4. The method of claim 3, wherein the collecting of combustion pressure data for one cycle and determining of a TDC at a signal generation point from the collected data determines the TDC at the signal generation point as a compression TDC or an intake/exhaust TDC by comparing an initially collected combustion pressure datum of the combustion pressure data collected for one cycle with predetermined reference pressure.

5. The method of claim 4, wherein the collecting of combustion pressure data for one cycle and determining of a TDC at a signal generation point from the collected data determines the TDC at the signal generation point as the compression TDC when the initially collected combustion pressure datum is the reference pressure or more.

6. The method of claim 3, wherein the maintaining or changing of signal setting of the angle sensor in accordance with the result of determination, and collecting of the combustion pressure data for one cycle from a setting position:

maintains a signal setting order of the angle sensor and collects the combustion pressure data for one cycle sequentially in accordance with the signal setting order of the angle sensor when the TDC at the signal generation point is an intake/exhaust TDC; and

changes the signal setting order of the angle sensor and collects the combustion pressure data for one cycle sequentially in accordance with the changed signal setting order of the angle sensor when the TDC at the signal generation point is a compression TDC.

7. A method for collecting 1-cycle data for output measurement and combustion analysis of a large-sized low-speed 4-stroke engine, the method comprising:

collecting combustion pressure data for 1.5 cycles by taking a predetermined pulse signal of an angle sensor as a start signal;

determining a data collection range corresponding to one cycle by comparing an initially collected combustion pressure datum of the combustion pressure data collected for 1.5 cycles with predetermined reference pressure; and

collecting the combustion pressure data from the determined data collection range corresponding to one cycle.

8. The method of claim 7, wherein the determining of a data collection range corresponding to one cycle by comparing an initially collected combustion pressure datum of the combustion pressure data collected for 1.5 cycles with predetermined reference pressure:

determines a range from the position where the combustion pressure data are initially collected to the position of a 1 cycle as the data collection range when the initially collected combustion pressure datum is less than the reference pressure; and

determines a range from the position of a 0.5 cycle to the position of a 1.5 cycle as the data collection range when the initially collected combustion pressure datum is the reference pressure or more.

9. A computer-readable recording medium on which a program for executing the method of any one of claims 1 to 8 in a computer is recorded.

Drawing