A test method for rapid evaluation of the antioxidant properties of engine lubricating oils

Abstract

The present invention provides a test method for quickly evaluating the anti-oxidation property of engine lubricating oil, characterized in that it includes the following steps: modifying the oil pan structure to reduce the oil storage capacity of the oil pan; screening out high heat load conditions as test conditions through universal characteristic tests; increasing the engine heat load and the soot generation rate in the lubricating oil by calibrating the engine exhaust pressure under the test conditions; and increasing the engine heat load, mechanical load and the soot generation rate in the lubricating oil by calibrating the engine fuel circulation supply. Beneficial effects of the present invention: a test method for quickly evaluating the anti-oxidation property of engine lubricating oil, which solves the technical problems of large oil consumption, low severity, long test cycle and high test cost in the test evaluation of the anti-oxidation property of lubricating oil with a long oil change cycle of the engine, and can effectively reduce the test sample amount for the evaluation of the anti-oxidation property of engine lubricating oil, increase the test severity, shorten the evaluation cycle, and greatly save the test cost.

Description

Technical Field

[0001] The invention belongs to the field of automobile testing, and in particular relates to a test method for quickly evaluating the anti-oxidation property of engine lubricating oil. Background Art

[0002] Engine lubricating oil plays the role of lubrication, cooling, and sealing during the operation of the engine, and is called the "blood" of the engine. The engine lubrication performance has an important impact on the engine's power, thermal efficiency, emissions, and reliability. Antioxidation is a key property that reflects the oxidation tendency of engine lubricating oil under operating conditions. This property plays a decisive role in the lubricating oil change cycle. Therefore, when evaluating the specifications of engine lubricating oil, antioxidation is a very important assessment item.

[0003] At present, my country's national standards for engine lubricants are equivalent to the American API system. For example, the latest specification CI-4 of GB11111-2006 "Diesel Engine Oil" uses an engine bench 20 years ago to assess the oxidation resistance of diesel engine lubricants. For my country, engine technology has made great progress in recent years towards high rail pressure, high explosion pressure, and long oil change cycle, and has basically achieved technological independence. At present, the oil change cycle of many domestic high-end diesel engine lubricants has exceeded 100,000 kilometers. The oil change cycle of CI-4 diesel engine lubricants is only about 25,000 kilometers, which is far from meeting the current use needs of high-end diesel engines. A large amount of driving test data shows that most diesel engine oils certified by CI-4 specifications will gradually oxidize and deteriorate, darken in color, increase in viscosity, and then fail under long-term operation. Therefore, improving the oxidation resistance of engine lubricants is an important way to meet the demand for long oil change cycles.

[0004] In order to evaluate the performance of engine lubricants, the most practical method is to use a driving test. Most of them need to run for more than 100,000-200,000 kilometers to reach the "critical point" of engine oil oxidation and deterioration, and then evaluate the anti-oxidation property of the lubricant. However, the running time and mileage of the driving test are too long, which is very expensive, and the test boundary conditions are difficult to control and the repeatability is poor. The engine bench method can truly simulate the operating conditions of the engine and conduct the test under specified controllable environmental conditions. It is an effective evaluation method.

[0005] The current engine lubricant specification certification bench method has a significantly lower level of severity in the assessment of anti-oxidation properties, resulting in low differentiation of test results, long test cycles, and high test costs. In order to meet the test and evaluation needs of engine lubricants with long oil change cycles, it is urgent to develop a fast and scientific test method for evaluating the anti-oxidation properties of engine lubricants. Summary of the invention

[0006] In view of this, the present invention aims to provide a test method for quickly evaluating the anti-oxidation property of engine lubricating oil, so as to solve at least one problem in the background technology.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0008] In the first aspect, the present invention discloses a test method for quickly evaluating the anti-oxidation property of engine lubricating oil, which is achieved by performing the following steps:

[0009] Step 1: modifying the structure of the oil pan (1) to reduce its oil storage volume;

[0010] Step 2: Through the universal characteristic test, select the high heat load condition as the test condition;

[0011] Step 3: By changing the engine exhaust back pressure under the test conditions, the engine heat load and the soot generation rate in the engine oil are adjusted; the engine exhaust pressure calibration under the test conditions is completed;

[0012] Step 4: By changing the circulating fuel supply of the engine fuel, adjust the thermal load, mechanical load and soot generation rate in the engine oil; complete the calibration of the circulating fuel supply of the engine fuel under the test conditions;

[0013] Step 5: Clean the engine lubricating oil circulation pipeline with the test lubricating oil to be tested;

[0014] Step 6: Add an appropriate amount of the test lubricant to be tested, and take samples of the test oil and perform oxidation value detection and analysis;

[0015] Step 7: Formal start of the engine lubricating oil anti-oxidation rapid evaluation test and start the test timing;

[0016] Step 8: Extract a certain amount of the test lubricating oil to be tested from the engine at regular intervals, and perform physical and chemical index testing and analysis on oxidation value, nitration value, kinematic viscosity, etc.;

[0017] Step 9: Draw the oxidation value curve of the lubricant to be tested from the test start point. If the oxidation value increases slowly, continue to run the bench test and take samples for analysis according to the above rules;

[0018] Step 10: Repeat step 8 until the oxidation value curve of the test lubricant oil to be evaluated shows a sudden increase inflection point, end the test, and record the corresponding test time.

[0019] Furthermore, in the second aspect, this solution discloses a specific implementation process of step 2:

[0020] Step 2.1: Perform universal characteristics test on the engine bench;

[0021] Step 2.2: Based on the universal characteristic test results, select the operating condition with the highest oil temperature in the main oil gallery as the test condition;

[0022] Furthermore, in the third aspect, this solution discloses a specific implementation process of step 3:

[0023] Step 3.1: Run the engine under the test conditions described in step 2.2, and monitor the engine cylinder explosion pressure, pressure rise rate, maximum average cylinder temperature and exhaust temperature data;

[0024] Step 3.2: Within the safety limits of the above-mentioned engine cylinder explosion pressure, pressure rise rate, maximum average cylinder temperature and exhaust temperature monitoring parameters, gradually reduce the engine exhaust back pressure valve opening according to the gradient to increase the engine exhaust pressure.

[0025] Furthermore, in a fourth aspect, this solution discloses a specific implementation process of step 4:

[0026] Step 4.1: Run the engine under the test conditions determined in step 2.2 and the engine exhaust pressure determined in step 3.2, and monitor the engine cylinder explosion pressure, pressure rise rate, maximum average cylinder temperature and exhaust temperature data;

[0027] Step 4.2: Use the upper computer software with calibration function to gradually increase the circulating fuel supply in the test condition area until one or more of the engine cylinder explosion pressure, pressure rise rate, maximum average cylinder temperature and exhaust temperature monitoring parameters described in step B1 are close to the engine safety limit.

[0028] Compared with the prior art, the test method for quickly evaluating the anti-oxidation property of engine lubricating oil according to the present invention has the following beneficial effects:

[0029] (1) The test method for quickly evaluating the anti-oxidation property of engine lubricating oil described in the present invention can simulate the actual use conditions of engine lubricating oil on an engine test bench, thereby realizing a scientific evaluation of the anti-oxidation property of engine lubricating oil;

[0030] (2) The test method for quickly evaluating the anti-oxidation property of engine lubricating oil described in the present invention can significantly reduce the amount of samples used in the evaluation test of the anti-oxidation property of engine lubricating oil, thereby saving resources and energy;

[0031] (3) The test method for rapidly evaluating the anti-oxidation property of engine lubricating oil described in the present invention can adjust the decay rate of the anti-oxidation property of engine lubricating oil and other properties, and adjust the severity of the evaluation test according to actual needs;

[0032] (4) The test method for quickly evaluating the anti-oxidation property of engine lubricating oil described in the present invention can significantly shorten the test period for evaluating the anti-oxidation property of engine lubricating oil, reduce the error caused by fluctuations in test conditions during long-period evaluation, and effectively improve the accuracy and scientificity of the test results;

[0033] (5) The test method for quickly evaluating the anti-oxidation property of engine lubricating oil described in the present invention can greatly improve the test efficiency of evaluating the anti-oxidation property of engine lubricating oil, reduce the consumption of manpower and material resources, and effectively reduce the test cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0035] Figure 1 It is a schematic diagram of the engine lubricating oil pan modification method described in an embodiment of the present invention.

[0036] Description of reference numerals:

[0037] 1-Oil pan; 2-Lubricating oil suction pan; 3-Lubricating oil level; 4-Pad. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0040] The present invention patent proposes a method for rapid evaluation of the anti-oxidation property of engine oil based on engine bench test. In order to achieve rapid evaluation of the anti-oxidation property of engine oil, it is necessary to design an accelerated degradation test of engine oil. The present invention patent includes the following specific steps:

[0041] Step 1: Low oil capacity oil pan modification

[0042] The present invention patent proposes a method for modifying a low-oil-storage oil pan to reduce the amount of lubricating oil used in the engine, accelerate the oxidation and deterioration of the lubricating oil, and reduce the amount of test samples. The lubricating oil required to maintain normal operation in the engine only accounts for 1 / 2 or less of the total lubricating oil filling volume of the engine body. The remaining lubricating oil is mainly used to supplement the lubricating oil loss caused by long-term operation, and the excess lubricating oil is stored in the oil pan. In the engine bench test, too much lubricating oil will dilute the gradually oxidized and deteriorated lubricating oil, slow down the decay process of the lubricating oil, and cause the evaluation test cycle to be too long. The specific steps of the oil pan modification proposed by the present invention patent are as follows:

[0043] Step 1.1: Remove the engine oil pan.

[0044] Step 1.2: Weld a closed pad 4 at the bottom of the oil pan 1, close to one side wall. The closed pad should avoid the position of the lubricating oil suction plate 2, have good airtightness, and be made of stainless steel and other materials with high stability in high-temperature oil immersion environment. Its size and position can be set according to actual test requirements and specific oil pan structure. Specific requirements are as attached. Figure 1 shown.

[0045] Step 1.3: Install the oil pan and other parts, and connect the engine and test bench accessories normally.

[0046] Step 1.4: Add lubricating oil to keep the lubricating oil level 3 in the oil pan unchanged from that before the modification. The amount of lubricating oil added is calculated according to "lubricating oil filling amount = original lubricating oil filling amount - the volume of the pad under the lubricating oil level".

[0047] Step 2: Screening of high heat load engine test conditions

[0048] The present invention patent proposes a method for screening high heat load test conditions to accelerate the oxidation and degradation of lubricating oil and shorten the test cycle. The heat load of the engine under different operating conditions is different, and the maximum combustion temperature in the cylinder, exhaust temperature, and main oil gallery oil temperature are different. The higher the main oil gallery oil temperature, the faster the high-temperature oxidation rate of the lubricating oil. The specific steps for screening high heat load test conditions proposed by the present invention patent are as follows:

[0049] Step 2.1: Perform universal characteristics test on the engine bench;

[0050] Step 2.2: Based on the universal characteristic test results, select the operating condition with the highest oil temperature in the main oil gallery as the test condition.

[0051] For example, Table 1 shows the test data obtained by using the high heat load test condition screening method proposed in the present invention. As can be seen from Table 1, at the same engine speed, the higher the load percentage, the greater the heat load, and the higher the exhaust temperature and the main oil channel oil temperature. By comparing the test data, it can be found that under condition 8, the exhaust temperature and the main oil channel oil temperature of the test engine both reached the highest. Therefore, condition 8, speed 1800r / min, 100% load can be used as a high heat load test condition for quickly evaluating the antioxidant properties of engine lubricating oil.

[0052] Table 1 Engine high heat load test condition screening test data

[0053]

[0054] Step 3: Engine high exhaust pressure calibration

[0055] The present invention patent proposes a high exhaust pressure calibration scheme to reduce the engine ventilation efficiency, reduce the intake volume, and increase the in-cylinder fuel-air equivalence ratio, thereby increasing the in-cylinder combustion temperature and the main oil channel oil temperature, accelerating the soot generation rate in the oil, and achieving the purpose of accelerating the evaluation of the lubricating oil anti-oxidation test. At present, mainstream diesel engines all use lean-burn combustion technology, and diesel fuel can achieve very complete combustion. On this basis, if the intake volume is reduced, the mixture concentration will increase, the combustion heat release rate and combustion temperature will increase, the heat load of the engine combustion system will increase, and the severity of the lubricating oil anti-oxidation test will increase. By calibrating the engine exhaust back pressure, the engine intake volume can be indirectly adjusted to change the engine's combustion temperature and exhaust temperature. The specific steps of the engine high exhaust pressure calibration scheme proposed by the present invention patent are as follows:

[0056] Step 3.1: Using the oil pan modified in step 1, under the test conditions described in step 2.2, use a combustion analyzer and a bench control system to monitor data such as explosion pressure, pressure rise rate, maximum average temperature in the cylinder, and exhaust temperature;

[0057] Step 3.2: Within the safety limits of the monitoring parameters of the explosion pressure, pressure rise rate, maximum average temperature in the cylinder and exhaust temperature, gradually reduce the back pressure valve opening according to a certain gradient to increase the exhaust pressure;

[0058] For example, Table 2 shows the test data obtained by using the exhaust pressure calibration scheme proposed in the present invention. As can be seen from Table 1, the exhaust pressure of the original engine under the test conditions is 14kPa, the maximum average temperature in the cylinder is 1652℃, and the exhaust temperature is 529℃. After adopting the exhaust pressure calibration scheme proposed in the present invention, the exhaust pressure is increased to 30kPa. Under the condition of ensuring the safe operation of the engine, the maximum average temperature in the cylinder and the exhaust temperature are increased by 180℃ and 67℃ respectively. The thermal load of the engine is significantly increased, the severity of the engine lubricant evaluation test is increased, the high-temperature oxidation of the engine lubricant is accelerated, and the test cycle is greatly shortened.

[0059] Table 2 Engine exhaust pressure calibration test data

[0060]

[0061] Step 4: Engine overload fuel cycle fuel supply calibration

[0062] The present invention patent proposes a method for calibrating the engine overload fuel circulation supply, so as to increase the engine fuel circulation supply under the test conditions, increase the combustion temperature, exhaust temperature and lubricating oil temperature in the cylinder, and achieve the purpose of accelerating the oxidation and deterioration of the lubricating oil. In order to ensure higher durability and reliability, the thermal load and mechanical load of normal mass-produced engines will leave a certain margin below the bearing limit of the piston, cylinder liner and cylinder body. When conducting a lubricating oil bench evaluation test, if a normal mass-produced engine is used without modification, the lubricating oil oxidation rate is slow, the assessment cycle is long, and the discrimination is low. Through engine ECU calibration, the circulating fuel supply can be increased, the thermal load of the test conditions can be effectively increased, and the aging of the lubricating oil can be accelerated. The specific steps of the engine fuel circulation supply calibration scheme proposed by the present invention patent are as follows:

[0063] Step 4.1: Using the oil pan modified in step 1, under the test conditions described in step 2.2, using the engine exhaust pressure calibrated in step 3.2, using a combustion analyzer and a bench control system to monitor the burst pressure, pressure rise rate, maximum average temperature in the cylinder, and exhaust temperature data;

[0064] Step 4.2: Use INCA host computer software to gradually increase the circulating fuel supply in the test operating condition area until one or more of the burst pressure, pressure rise rate and exhaust temperature are close to the engine safety limit.

[0065] For example, Table 3 shows the test data of the engine fuel cycle supply calibration scheme proposed by the patent of this invention. It can be seen from Table 3 that the single-cylinder cycle supply of the original test engine is 230 mg / cycle, the maximum average temperature in the cylinder is 1832°C, and the exhaust temperature is 596°C. After adopting the engine ECU cycle supply calibration method proposed by the patent of this invention, the single-cylinder cycle supply is increased to 254 mg / cycle. Under the condition of ensuring the safe operation of the engine, the maximum average temperature in the cylinder and the exhaust temperature are increased by 70°C and 42°C respectively. The use of this method effectively increases the thermal load of the engine, accelerates the high-temperature oxidation rate of the lubricating oil, and improves the efficiency of the lubricating oil anti-oxidation evaluation test.

[0066] Table 3 Engine fuel cycle fuel supply calibration test data

[0067]

[0068] Step 5: Clean the engine lubricating oil circulation pipeline with the test lubricating oil to be tested;

[0069] Step 6: Add an appropriate amount of the test lubricant to be tested, and take samples of the test oil and perform oxidation value detection and analysis;

[0070] Step 7: Formal start of the engine lubricating oil anti-oxidation rapid evaluation test and start the test timing;

[0071] Step 8: Extract a certain amount of the test lubricating oil to be tested from the engine at regular intervals, and perform physical and chemical index testing and analysis on oxidation value, nitration value, kinematic viscosity, etc.;

[0072] Step 9: Draw the oxidation value curve of the lubricant to be tested from the test start point. If the oxidation value increases slowly, continue to run the bench test and take samples for analysis according to the above rules;

[0073] Step 10: Repeat step 8 until the oxidation value curve of the test lubricant oil to be evaluated shows a sudden increase inflection point, end the test, and record the corresponding test time.

[0074] The test time corresponding to the inflection point of the sudden increase in the oxidation value of the test lubricant to be assessed can characterize the antioxidant property of the test lubricant to be assessed. The longer the test time, the better the antioxidant property of the test lubricant to be assessed. Conversely, the worse the antioxidant property of the test lubricant to be assessed.

[0075] The specific implementation methods of the present invention are as follows:

[0076] 1. The low oil storage capacity oil pan modification scheme was adopted to modify the lubricating oil pan of Weichai WP13 test engine, and a 10L pad was installed in the oil pan, reducing the oil storage capacity of the oil pan from 30L to 20L.

[0077] 2. The engine high thermal load test condition screening scheme is adopted to carry out the engine universal characteristic test, and the speed of 1800r / min and 100% load condition are screened as the test condition.

[0078] 3. The engine high exhaust pressure calibration scheme is adopted to increase the exhaust pressure of the engine under the test condition from 14 kPa to 30 kPa, and the corresponding maximum average temperature in the cylinder and the exhaust temperature are increased by 250°C and 43°C respectively.

[0079] 4. By adopting the engine overload cycle fuel supply calibration scheme, the single-cylinder cycle fuel supply under the engine test condition (1800r / min, 100% load) was increased from 230mg / cycle to 254mg / cycle. While ensuring the safe operation of the engine, the maximum average temperature in the cylinder and the exhaust temperature increased by 70°C and 42°C respectively.

[0080] 5. Use test oil to clean the engine lubricating oil circulation pipeline.

[0081] 6. Add 20L of test oil, take samples of the test oil and conduct oxidation value analysis.

[0082] 7. Under the above test conditions, the engine lubricating oil rapid evaluation bench test is formally run using the calibrated engine exhaust pressure and circulating oil supply.

[0083] 8. Stop the machine every 10 hours, take samples of the test oil, and conduct oxidation value detection and analysis.

[0084] 9. From the start of the test (0h), draw a curve of the oxidation value of the test oil versus the test duration. If the increase in the oxidation value of the test oil sample is ≤10%, continue to run the bench test and take samples for analysis according to the above rules.

[0085] 10. Repeat step 8 until the oxidation value of the test oil sample at 200h reaches 79.5A / 0.1mm (the oxidation value at 190h is 62.3A / 0.1mm), an increase of 27.6%, and the test is over.

[0086] The test result of the rapid evaluation of the antioxidant properties of the test oil sample is 200 (h).

[0087] Those of ordinary skill in the art will appreciate that the units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0088] In the several embodiments provided in the present application, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the division of the units described above is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. The above-mentioned units may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of the present invention.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A test method for quickly evaluating the antioxidant properties of engine lubricating oil, characterized in that: The steps include: Step 1: modifying the structure of the oil pan (1) to reduce its oil storage volume; Step 2: Through the universal characteristic test, select the high heat load condition as the test condition; Step 3: Adjust the engine heat load and the soot generation rate in the engine oil by changing the engine exhaust pressure under the test conditions; Complete engine exhaust pressure calibration under test conditions; Step 4: By changing the circulating fuel supply of the engine fuel, adjust the thermal load, mechanical load and soot generation rate in the engine oil; complete the calibration of the circulating fuel supply of the engine fuel under the test conditions; Step 5: Clean the engine lubricating oil circulation pipeline with the test lubricating oil to be tested; Step 6: Add an appropriate amount of the test lubricant to be tested, and take samples of the test oil and perform oxidation value detection and analysis; Step 7: Formal start of the engine lubricating oil anti-oxidation rapid evaluation test and start the test timing; Step 8: Extract a certain amount of the test lubricating oil to be tested from the engine at regular intervals, and perform physical and chemical index testing and analysis on oxidation value, nitration value, and kinematic viscosity; Step 9: Draw the oxidation value curve of the lubricant to be tested from the test start point. If the oxidation value increases slowly, continue to run the bench test and take samples for analysis according to the above rules; Step 10: Repeat step 8 until the oxidation value curve of the test lubricant oil to be evaluated shows a sudden increase inflection point, end the test, and record the corresponding test time.

2. A test method for rapidly evaluating the anti-oxidation property of engine lubricating oil according to claim 1, characterized in that: The step 1 is implemented by executing at least one of the following specific methods: Method 1.1: Place filler in the oil pan; Method 1.2: Change the shape of the oil storage area at the bottom of the oil pan to reduce its oil storage volume.

3. A test method for rapidly evaluating the anti-oxidation property of engine lubricating oil according to claim 1, characterized in that: The step 2 includes the following specific processes: Step 2.1: Carry out universal characteristics test on the engine bench; Step 2.2: Based on the universal characteristic test results, select the operating condition with the highest oil temperature in the main oil gallery as the test condition.

4. A test method for rapidly evaluating the anti-oxidation property of engine lubricating oil according to claim 1, characterized in that: The step 3 includes the following specific processes: Step 3.1: Run the engine under test conditions and monitor the engine cylinder explosion pressure, pressure rise rate, maximum average cylinder temperature and exhaust temperature data; Step 3.2: Within the safety limits of the above engine cylinder explosion pressure, pressure rise rate, maximum average cylinder temperature and exhaust temperature monitoring parameters, gradually reduce the exhaust back pressure valve opening according to the gradient to increase the engine exhaust pressure.

5. A test method for quickly evaluating the anti-oxidation property of engine lubricating oil according to claim 1, characterized in that: The step 4 includes the following specific processes: Step 4.1: Run the engine under the test conditions determined in step 1 and the engine exhaust pressure determined in step 2, and monitor the engine cylinder explosion pressure, pressure rise rate, maximum average cylinder temperature and exhaust temperature data; Step 4.2: Use the upper computer software with calibration function to gradually increase the circulating fuel supply in the test condition area until one or more of the engine cylinder explosion pressure, pressure rise rate, maximum average cylinder temperature and exhaust temperature monitoring parameters described in step B1 are close to the engine safety limit.

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