Cause analysis and elimination of excessive temperature of Deutz series air-cooled diesel engine

1 Preface

  Due to the fact that no water cooling system is required for the Deutz series air-cooled diesel engine (hereinafter referred to as diesel engine), it has the advantages of simple structure, low manufacturing cost, good economy, strong environmental adaptability, fast heat engine and good starting performance. However, due to the forced cooling of the diesel engine by wind, if the diesel engine is not properly used and maintained, the temperature of the diesel engine will be too high, resulting in the alarm of the cylinder head temperature alarm and the oil temperature alarm.

  If the temperature of the diesel engine is too high, it will lead to the reduction of power performance, even cylinder pulling, tile burning and other accidents, and even more serious, it will lead to the spontaneous combustion of the engine. In view of the fault phenomenon that the oil temperature of air-cooled diesel engine is too high in the process of use, this paper analyzes the various causes and troubleshooting methods of the fault from different angles, and further demonstrates the typical fault with examples.

2 Introduction to Deutz series diesel engines

  2.1 Scope of application

  Deutz series air-cooled diesel engines are air-cooled V-type diesel engines produced by Deutz (KHD), Germany, mainly 12 and 8 cylinders, which are widely used in railway self-wheel running equipment. The main models are tamping truck DCL-32/DC-32, power stabilizer WD-320, ballast shaping truck SPZ-200/DPZ-350, and screen cleaner QS-650.

  2.2 Technical characteristics

  The diesel engine is of high-speed four-stroke, V-shaped structure, and the included angle of cylinder arrangement is 90 °; Direct injection type ω U-shaped or U-shaped combustion chamber; Gantry crankcase and one cover for each cylinder are adopted, and the crankshaft connecting rod mechanism is multi-support three-layer alloy sliding bearing; Parallel connecting rod and oil-cooled piston with three sealing rings; Horizontal axial flow fan with front stationary blades; Overhead valve with rotating device and valve train adapted to high-speed operation; Oil supply system with automatic injector; Cold start system with flame heater and auxiliary heating device; Rear helical gear drive mechanism.

  2.3 Technical parameters of Deutz diesel engine

  Specific meaning of model code: there are mainly 413 and 513 air-cooled Deutz models, and the meaning of model code is shown in Figure 1.

  See Table 1 for main technical parameters of DEUTZ B/L413F/513/C series air-cooled diesel engine.

  The alarm temperature of diesel engine cylinder head is 175 ℃, the alarm temperature of supercharged diesel engine oil is 125 ℃, and the alarm temperature of non-supercharged diesel engine oil is 115 ℃.

3 Cause analysis of high temperature of diesel engine

  3.1 Cooling system failure

  (1) The radiator is not clean

The cylinder liner, cylinder head, oil radiator and intercooler radiator of turbocharged diesel engine are the main parts of diesel engine heat dissipation. If dust is accumulated on the radiator, it will directly affect the cooling effect of diesel engine. Therefore, these parts should be cleaned regularly, and the oil or oil circuit on the fan, cylinder liner, oil radiator and hydraulic oil radiator should be eliminated at any time to avoid accelerating the accumulation of dust.

  (2) Poor sealing of cooling air guide plate

The cooling air flow diagram of Deutz diesel engine is shown in Figure 2 (cooling air flow diagram).

  The task of the air deflector is to guide the cooling air for the cylinder liner to achieve uniform cooling of the cylinder liner, so the air deflector must be complete, free of cracks and falling blocks, and replaced if necessary. The position of the tie rod of the air deflector should be checked regularly, and the air deflector should be timely adjusted and tightened in case of displacement.

  (3) The top cover plate of the air pressure chamber is poorly sealed

  In order to carry out other maintenance and repair work on the diesel engine, sometimes the cover plate of the air pressure chamber will be removed, so the fastening screws may be lost. Therefore, it is necessary to check whether the fastening screws of the cover plate of the air pressure chamber are complete and tightened, whether the cover plate of the air pressure chamber is deformed and damaged, and whether the sealing strip is complete.

  (4) Cooling fan problem

  The cooling fan inlet is not smooth. If the protective fence plate of the cooling fan is blocked by oil dirt, or dust is accumulated on the stationary blades of the fan, the air conductivity will be affected, thus reducing the inlet air volume and working efficiency of the cooling fan. Therefore, the dirt on the cooling fan and protective fence should be cleaned regularly.

  The oil secondary filter is dirty. The oil fine filter housing is connected with the driving drum of the coupler, so as long as the diesel engine rotates, the oil fine filter housing will also rotate, and the solid foreign matters in the oil will be separated on the inner wall of the oil fine filter housing under the action of centrifugal force, forming the effect of high efficiency fine filter. If the oil is not cleaned for a long time, the inner wall of the oil fine filter will become thicker, the fine filter effect will become worse, and the oil will become dirty, affecting the overall cooling of the diesel engine. Therefore, check and clean the oil fine filter regularly, at least once a year.

  Method: As shown in Figure 3 (maintenance diagram of oil fine filter), unscrew the hexagon bolt 1, remove the cover 2, unscrew the hexagon bolt 3, and remove the reinforcing ring. Turn the socket wrench to the right, extrude the filter cup 4, remove the filter cover and clean the inside, pay attention to the correct position of the "O" ring when reassembling, and replace the damaged "O" ring immediately. During the test run, check whether the seal is normal.

  (5) The temperature sensor and thermometer are faulty or damaged. A problem with the sensor or thermometer will lead to incorrect display of the engine temperature or false alarm of high temperature. The problem can be solved by replacing the corresponding sensor or thermometer.

  3.2 Insufficient intake of diesel engine combustion chamber

  (1) Air filter clogged

Due to the harsh working environment of railway maintenance machinery, the air filter is easy to be blocked by dust, resulting in insufficient intake of diesel engine, combustion deterioration, higher exhaust temperature and lower power. Therefore, the air filter should be cleaned or replaced regularly as required.

  (2) Air filter maintenance indicator function failure

Check whether the maintenance indicator is damaged. If the maintenance indicator does not work, it is not easy for the operator to observe its internal cleanliness. It may be gradually blocked by dust, which may cause the temperature of the diesel engine to rise, and in extreme cases, the diesel engine will be shut down.

  (3) Air inlet and exhaust pipe leaks

If the intake pipe is not sealed, the power of the diesel engine will be directly reduced. If the exhaust pipe is not sealed, the boost pressure will become very low for the turbocharged diesel engine. If the throttle is increased when the power is not reached, the fuel injection will be excessive, the combustion of the diesel engine will deteriorate, and the thermal load will increase and overheat. In case of unsealing, check whether all sealing rings are complete, all flange screws are tightened, and flange pipe fittings are damaged.

  (4) Intercooler contamination

For turbocharged diesel engines, the temperature of the intake air after passing through the compressor rises sharply, which directly affects the charging volume of the diesel engine, while the intercooler can cool the high-temperature intake air. Normally, when the inlet temperature of cooling fan is 25 ℃ and the inlet temperature of compressor outlet is 150 ℃, the inlet temperature after intercooler can be reduced to about 70 ℃. If the upper part of the intercooler is full of dust, it will directly affect the cooling effect of the intercooler, and it should be cleaned immediately.

  (5) Turbocharger fault

The causes of supercharger failure include: ① the intake volume of diesel engine is reduced due to long-term use or poor dust removal effect of air filter, which may cause overheating of diesel engine. Therefore, the cleaning times of relevant parts shall be increased, and the scale shall be removed and scraped when it is serious. ② Carbon deposits are generated in the supercharger, and the diesel engine's long-term poor combustion can cause carbon deposits to form on both sides of the turbine wheel, between the rotating shaft and the labyrinth seal ring, which affects the function of the supercharger, and further worsens the combustion. The elimination measures are to ensure the good combustion state of the diesel engine and regularly dismantle and inspect the supercharger.

  (6) Poor exhaust

If the exhaust pipe is deformed or blocked, it will directly affect the exhaust of the diesel engine, reduce the amount of fresh air, and affect the speed of the supercharger, resulting in the reduction of the intake pressure, the deterioration of the diesel engine combustion and the temperature rise. Therefore, it is necessary to check and clean the exhaust pipe and other exhaust channels frequently to eliminate the blockage.

  3.3 Fuel system failure

  (1) Injector failure

Generally, the fuel injector leaks or the fuel atomization is poor, which worsens the combustion of the diesel engine and causes the diesel engine to overheat. For this reason, the injection pressure of the fuel injector should be adjusted. If the injection is abnormal, the fuel injector should be replaced and the injection pressure should be readjusted.

  (2) Fuel supply advance angle error

Sooner or later, the fuel injection pump will affect the working performance of the diesel engine, so that the heat released by combustion can not be fully used for work, so it should be adjusted in time. Table 2 shows the injection advance angle and injection pressure of Deutz air-cooled diesel engine.

  (3) Fuel supply advancer failure

The damage of the fuel injector advance will lead to the error of the fuel supply advance angle, affect the working performance of the diesel engine, and cause the diesel engine to overheat. Remove the advance to check the damage and repair it.

  (4) The fuel injection volume of the fuel injection pump is too large

The fuel injection volume of the fuel injection pump should match the altitude of the area where the diesel engine is located. For the diesel engine, the intake volume and fuel injection volume in the combustion chamber are matched. They both determine the power and temperature level of the diesel engine. If the fuel injection volume does not match the altitude of the region, resulting in a large fuel injection volume, the thermal load of the diesel engine will be high, and the fuel injection volume should be adjusted according to the technical parameters of the diesel engine. Table 3 is the reference fuel injection volume for 100 cycles of the injection pump plunger of the Deutz air-cooled diesel engine.

  3.4 Lubrication system failure

  (1) Abnormal oil level

The oil position in the diesel oil sump is subject to the fact that the crankshaft is not immersed. When the oil level is too high, the crankshaft will stir the oil, thus raising the oil temperature; When the oil level is too low, the circulating load of the oil is large, and the oil temperature also increases. In order to measure the oil level of a diesel engine that has been parked for a long time before starting, and to measure the oil level immediately after the diesel engine is stopped, two kinds of marks are set on the DEUTZ diesel oil scale.

Point mark: after the diesel engine has been parked for a long time, the oil level before starting shall be measured according to the point mark.

Line marking: when the diesel engine stops after idling for 1~2 min, measure the oil level according to the line marking.

  (2) Dirty oil radiator

Dirty oil radiator will reduce the oil cooling effect and increase the oil temperature. The solution is to clean the oil cooler regularly.

  (3) Damaged temperature control valve in oil radiator

The oil temperature control valve is installed in the bypass valve body below the oil radiator. The function of the oil temperature control valve is to ensure the normal operation of the diesel engine during cold start or under high cold and low temperature conditions. At this time, due to the high viscosity and high pressure of the oil, forced cooling is not conducive to the rise of the oil to the normal operating temperature. When the oil reaches 94 ℃, the temperature control valve opens to allow the oil to circulate through the oil radiator for cooling, When the temperature is lower than 94 ℃, the temperature control valve is locked and the oil is directly bypassed to the primary oil filter. When the temperature control valve fails, the circulating oil cannot be cooled by the oil radiator, resulting in an increase in oil temperature.

4 Typical fault analysis

  The model of diesel engine with fault is F12L513F; The name of the mechanical truck where the diesel engine is located is 08-32 tamping truck.

  4.1 Fault phenomenon

When the tamping truck is operating for more than half an hour, the engine oil temperature will alarm and the engine oil pressure will drop by about 1 bar. At this time, the measured engine oil temperature will exceed 110 ℃.

  4.2 Fault analysis

The engine oil temperature overtemperature alarm should be caused by the poor heat dissipation of the diesel engine oil. According to the diesel engine phenomenon, the main reasons for the excessive oil temperature are as follows:

  (1) The cooling fan speed is too low or stops running.

  (2) The poor sealing of the air pressure chamber causes the low pressure of the air pressure chamber and the heat cannot be dissipated.

  (3) Dirty oil radiator surface causes poor heat dissipation of the radiator.

  (4) The oil radiator thermostat does not work properly, causing the radiator to not work.

  4.3 Diesel engine inspection process

  (1) Check that the fan speed is about 4700 n/min and within the normal speed range with a tachometer.

  (2) Check the sealing strip of the air pressure chamber and all wind shields. The sealing strip is intact. When checking the wind deflector, it was found that two fixing bolts on one of the wind deflector were missing, and some cooling air leaked from there. After completing the missing bolts, it is analyzed that the leakage of cooling air here is not enough to make the oil temperature rise to the alarm level.

  (3) Continue to check. Check that the radiator surface is free of oil dirt, and the radiator is well ventilated after blowing its surface with pressure air.

  (4) After disassembling the oil radiator, it was found that there was no oil at the thermostat. After disassembling the radiator thermostat, it was found that the thermostat could not work properly. After replacing a new thermostat, it was found that the measured oil temperature in the oil pan continued to drop while the diesel engine was running, and the oil pressure also returned to normal. When the continuous tamping operation was carried out again, the oil temperature alarm disappeared, and the measured oil temperature in the oil pan remained within the normal range of 90~95 ℃.

  4.4 Fault generation process

Because the thermostat cannot be opened normally, the engine oil has not been cooled by the radiator, resulting in the temperature rise of the engine oil too fast. After continuous operation, the viscosity of the engine oil will drop, and the pressure will drop. If this fault is not handled for a long time, it will also cause serious consequences such as cylinder pulling and bearing.

5 Suggestions

  The cooling effect of the air-cooled diesel engine affects the service life of the diesel engine. The cooling system should be regularly checked and maintained.

  (1) Clean the oil sludge in the centrifugal fine filter of the fan coupler at least once a year to ensure the normal oil supply of the coupler.

  (2) Regularly check the tightness of the air pressure chamber of the diesel engine, check each windshield and sealant strip, and repair and replace the damaged ones in time.

  (3) Regularly check the operation of the thermostat. When the oil temperature in the oil pan reaches 90~95 ℃, the oil radiator should have hot air, that is, the thermostat should be in the open state. If there is no heat dissipation at 95 ℃, check the thermostat.

  (4) Regularly use pressure air to remove oil dirt and dust on the radiator surface, so that the radiator can maintain good heat dissipation effect.