Abstract No



Abstract No. : 020-0602

A study on the methodology of engine condition diagnosis using the variation of crankshaft angular speed

Authors

Byeong-Yeol Lee*, Tae-Hyun Baek, Won-Hyeon Kim, Seung-Jin Ha

* : Senior Research Engineer

Tel: 82-52-202-3208 Fax: 82-52-250-9587 E-mail : leeby931@

Hyundai Industrial Research Institute, Hyundai Heavy Industries Co., Ltd.

POMS 22nd Annual Conference

Reno, Nevada, U.S.A

April 29 to May 2, 2011

Abstract

Efficiency improvement in operation and maintenance for low & medium speed engines is a kind of never-ending requirements in the field of maritime and power plant business. For the purpose of improving the efficiency of engine management, a principal factor representing the fitness of engine should be identified. In the traditional EDS(Engine Diagnosis System), gas pressure and gas temperature have been used as the factors. But those factors have limitation in response speed and diagnosis accuracy.

As a new diagnostic factor, EFR(Engine Fitness Ratio) is suggested in this paper. EFR is defined as the ratio of particular frequencies in frequency domain and represents the fitness of an engine. It is calculated from the fluctuation pattern of the crankshaft angular speed. Validation of EFR was verified by experimental method for low speed engine and analytic method for medium speed engine respectively.

1. Introduction

Efficiency improvement in operation and maintenance for low & medium speed engines is a kind of never-ending requirement in the field of maritime and power plant business. For the purpose of improving the efficiency of engine management, a principal factor representing the fitness of engine should be identified. Many techniques have been studied to find out the principal factor. Gas pressure, gas temperature and vibration have been used as diagnostic factor. But, those factors have limitation in response speed and diagnosis accuracy.

Traditional EDS(Engine Diagnosis System) monitors engine condition basically using level comparison method. With this method, the EDS can detect engine troubles only after the condition has been deteriorated severely. To solve this problem, the EDS additionally adopt trend monitoring method. But it is also difficult to detect sudden deterioration of engine condition. With the purpose of solving these problems, we developed the EFD(Engine Fitness Diagnosis) method. EFD monitors the crankshaft speed fluctuation continuously and diagnoses the engine condition.

2. Engine condition diagnosis with EFR(Engine Fitness Ratio)

Instantaneous crank-shaft angular speed of an internal combustion engine fluctuates continuously. This phenomenon is caused by the reciprocating action of piston. The motion of a piston causes acceleration and deceleration on engine crank-shaft. The fluctuation of engine speed exists even at normal operation condition. In this study, EFD monitors and analyzes the speed fluctuation of low and medium speed engines.

Data gathering system of EFD consists of pulse detecting sensors, an analog signal gathering device and a data analysis system. Figure 1 shows the configuration of EFD system.

[pic]

Figure 1. System Configuration of EFD

The speed detecting sensors consists of a speed pulse detecting sensor and a phase detecting sensor. The speed pulse detecting sensor generates one pulse per one fly-wheel tooth. And Phase detecting sensor generates one pulse per one cycle. Phase detecting sensor is installed to detect the TDC of first cylinder. EFD calculates instant angular speed.

[pic] (1)

[pic] : Instant angular velocity

[pic] : Angle of fly-wheel

[pic]: Time interval

With the angular crank-shaft speed, EFD performs FFT(Fast Fourier Transform). EFR can be calculated by equation (2). EFD estimates the condition of an engine with the value of EFR.

[pic] (2)

1X : RPS(Revolution Per Second) of crank-shaft

3. Experimental Verification of EFR Method with Low Speed Engine

Validation of EFR was verified by experimental method for low speed engine. One of the most serious problems in cylinder is misfiring. If there is the misfiring at one cylinder, engine must slow down to avoid the effect of resonance. So, detection of misfiring is critical for the safety of a vessel. We performed misfire detection test with low speed engine. Table 1 shows the specification of the engine used in this test.

Table 1. Specification of Test Engine 6S60MC

|Item |Specification |

|Engine Model |6S60MC |

|Cylinder Number |6 |

|Firing Order |1-4-3-6-5-2 |

At figure 2, left-side shows normal condition signals and right-side shows misfire condition signals. Upper charts show the crank-shaft angular speeds. Misfire makes the pattern of time wave as different one. The difference can be verified with frequency domain data. The medium charts of figure 2 shows the spectrum data in frequency domain. As a result, the EFR at normal condition is 0.03 and the EFR at misfire condition is 1.79.

[pic] [pic]

[pic] [pic]

[pic] [pic]

(Normal Condition) (Misfire Condition)

Figure 2. FFT Result of 6S60MC Engine in Normal Condition

Above experimental result shows EFR represents the condition of engine very well.

4. Analytic Verification of EFR Method with Medium Speed Engine

Validation of EFR for medium-speed engine is verified by analytic method for medium speed engine. Table 2 shows the specification of the medium-speed engine used in this analytic validation.

Table 2 Specification of simulated medium-speed engine

|Item |Specification |

|Engine Model |6H21/32 at 900RPM |

|Cylinder Number |6 |

|Damper |Metaldyne Co. Ltd |

For the analytic validation, we used a torsional vibration simulation model. Figure 3 shows the modeling of simulated medium-speed engine. For the purpose of simulating the situation that one cylinder’s performance is deteriorated. We measured the cylinder pressure at 0%, 25%, 50%, 75% and 100% Load. And we used the measured cylinder pressure data as the input of torsional vibration simulation model.

[pic]

Figure 3. Modelling of simulated medium-speed engine

In the simulation, we changed the performance of 3rd cylinder as 0%, 25%, 50%, 75% and 100%. For example, 0% means misfire is occurred at 3rd cylinder. Figure 4 shows EFR value at each cylinder condition.

[pic]

Figure 4. FFT Result of 6S60MC Engine in Normal Condition

Above analytic result shows EFR_1 and EFR_0.5 represents the change of cylinder performance very sensitively. So we can use EFR as the principal factor representing the fitness of engine.

5. Conclusion

For the purpose of improving the efficiency of engine management, a principal factor representing the fitness of engine should be identified. As a new diagnostic factor, EFR(Engine Fitness Ratio) is suggested in this paper. EFR is defined as the ratio of particular frequencies in frequency domain and represents the fitness of an engine.

Validation of EFR was verified by experimental method for low speed engine and analytic method for medium speed engine respectively. The EFR represented the fitness of engine very well and can be used as a trigger signal for engine condition diagnosis. We expect to enhance our customer service with EFR method.

References

Taner Tuken, 2003, “On-line individual fuel injector diagnostics from instantaneous engine speed measurements”, United States Patent, Patent No : US 6,546,912

William B. Ribbens, Giorgio Rizzoni, 1993, “Method and system for detecting the misfire of an internal combustion engine utilizing angular velocity fluctuations”, United States Patent, Patent No : 5,200,899

Senichi Sasaki, 2004, “Vibration Monitoring for Fault Diagnosis of Cylinders in Marine Diesel Engine”, CIMAC Conference, Paper No. 69

Jianguo Yang, Lijun Pu, 2001, “Fault detection in a diesel engine by analyzing the instantaneous angular speed”, Mechanical System and Signal Processing, Vol. 15, pp.549-564

Mert Geveci, Andrew W. Osburn, 2005, “An investigation of crankshaft oscillations for cylinder health diagnostics”, Mechanical System and Signal Processing, Vol. 19, pp.1107-1134

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