康明斯發動機動力不足常見故障的分析判斷與排除

康明斯發動機動力不足常見故障判斷與排除

一、康明斯柴油發動機動力不足的現象與原因分析 

　　柴油發動機的工作過程經歷進氣、壓縮、作功、排氣四個行程。柴油機在進氣行程中吸入的是純空氣;在壓縮行程接近終了時，氣缸內空氣壓力可達3.5～4.5MPa、溫度高達750～1000K，同時，柴油經噴油泵將油壓提高到10MPa以上，通過噴油器噴入氣缸，在很短時間內與空氣混合后便立即自行發火燃燒。在高壓氣體推動下，活塞向下運動并帶動曲軸旋轉而作功，廢氣同樣經排氣管排入大氣中。

　　康明斯發動機與傳統柴油機最大的不同是采用了PT噴油器，即是將傳統燃油泵的柱塞(產生高壓)與噴油器針閥(控制噴射)集成為一體，取消了高壓油管，有效地消除了在高壓和高速下供油的壓力波動對供油規律的影響，而且有更高的噴油壓力(60～150MPa，甚至更高)，不僅可以滿足強化發動機所需的高噴油壓力和高噴射速率，而且霧化好、充氣效率高，更有利于燃燒和提高發動機性能。

　　發動機動力不足，從理論上講，主要是由于氣缸內混合氣燃燒不良或發動機運動機件摩擦阻力過大。導致燃燒不良的原因很多，例如:燃油供應不足、霧化不良，供油提前角不準、氣缸密封性下降、進氣不足、排氣不暢或配氣相位失準等。摩擦阻力過大的原因主要是發動機運動機件的間隙過小或潤滑油供應不足。

　　發動機動力不足且連續排黑煙，是發動機大多數缸或所有的缸均供油量過多、燃油與空氣混合比例失調、燃燒時嚴重缺氧、柴油燃燒不完全，懸浮游離狀的碳元素隨廢氣一同排出而形成的。若排氣管是斷續排黑煙，且伴有“突突”聲，說明個別缸燃燒不完全。

主要原因為:

①噴油泵調試不當，使供油量過多，燃燒不完全。

②多數噴油器的噴射質量差。

③供油不正時。

④進氣門開啟高度降低、開啟時間推遲，導致進氣不足。

⑤空氣濾清器濾芯過臟或空氣濾清器安裝有誤，使空氣不流暢。

⑥增壓器的增壓效能下降。

⑦燃油質量過差。

　　發動機運轉不均勻，排氣管大量排白煙、高速運轉不良、加速不靈敏，而且溫度易過高，主要的原因則有:噴油提前角過小、噴油器霧化不良、發動機溫度過低、氣缸內有水或油中有水等。

二、康明斯柴油發動機動力不足的故障診斷與處理方法 

　　診斷此類故障時，應從故障特征最明顯處著手，遵循由表及里、先易后難、少拆為益的基本原則。

　　1．排氣管排黑煙 

　　(1)若發動機突然冒黑煙，但運行一段時間后故障自然消失，則多為燃油質量較差所致，由于油中的雜質堵塞噴油器致噴射質量差，排氣冒黑煙，運行一段時間后雜質被高壓油沖掉，此種故障不用處理。

　　(2)若連續排黑煙，可考慮檢查進氣是否通暢、進氣管是否變形增加了進氣阻力。先拆下空氣濾清器蓋，取出濾芯并清理維護后重新試機，觀察排氣管是否仍繼續排黑煙。如果排煙明顯減少，則說明是空氣濾清器過臟或安裝有問題，影響了進氣量，應加強對進氣系統的維護保養。

　　(3)若進氣道氣流通暢，則應檢查供油時間是否過遲，供油過遲會使進入氣缸的燃油來不及充分燃燒就被排出而形成黑煙。

　　(4)多數噴油器的噴射質量嚴重惡化，燃油霧化差，不能適應燃燒室形狀的需要，致使可燃混合氣形成困難，部分燃油轉化成游離碳被排出，這也是導致黑煙的原因之一，故也應對噴油器進行檢查修理。

　　(5)檢查燃油質量是否合乎標準，應使用符合發動機在該地區環境溫度下正常工作的標準柴油。

　　(6)檢查增壓器的工作是否正常。當增壓器失效時，發動機進氣終了的壓力下降，致使壓縮終了溫度、壓力均下降，影響燃油的噴射霧化和燃燒溫度。

　　(7)如噴油泵維修時間不長、排氣管排黑煙，則應考慮是否噴油泵調試不當使供油量過多，對此應重新校正噴油泵在各種工況下的供油量，使之符合規定。

　　(8)若上述均正常，且發動機已運行了很長時間，可考慮檢查氣門開啟的高度和開啟時間是否正確。長時間的使用可使氣門傳動機件磨損，正常的配氣相位和氣門升程失準，進氣量減少，缸內殘余廢氣量相應增加，直接影響燃油的充分燃燒。

　　(9)對于轉速不均、斷續排黑煙、發動機無力的診斷可采用逐缸斷油法檢查。當某缸斷油時，發動機轉速明顯降低，黑煙減少，異響也消失，則說明該缸供油量過多，應對該缸噴油量進行檢查調整。若發動機轉速變化較小，黑煙消失，則說明該缸噴油器噴霧質量差，應對該噴油器進行檢查維修。若發動機轉速仍無變化，則說明該缸不工作，應檢查該缸的高壓供油情況，對PT噴油器進行檢查和調整。

　　2．排氣管排白煙 

　　(1)發動機動力不足，排氣管排灰白煙霧，首先將手靠于消聲器排氣口處，如果手上留有水珠，則應檢查柴油中和氣缸內有無水分。

　　(2)發動機剛發動時冒灰白煙，起因是起動時溫度過低，部分柴油揮發成蒸汽，未經燃燒直接排出所致。若待發動機溫度升高后灰白煙逐漸消失，則屬正?，F象。若發動機剛起動時冒灰白煙，且溫度升高后冒黑煙，則說明氣缸壓力不足，雖然壓燃條件有所改善，但柴油仍不能完全燃燒，使發動機動力不足，應對氣缸壓力進行檢查維修。

　　(3)發動機動力不足，排氣管排灰白色煙霧，通常是噴油提前角過小或噴油器霧化質量不佳所致。若伴隨發動機溫度過高、提速緩慢的情況，則可認為是噴油時間過遲，否則是噴油器霧化質量不佳。由于康明斯發動機采用的是PT噴油器，將傳統燃油泵的柱塞與噴油器針閥集成為一體，因此無論噴油時間過遲還是噴油器霧化質量不佳都要對PT噴油器進行調整。

Cummins engine underpowered common fault judgment and exclusion
A Cummins diesel engine power shortage cause analysis
The working process of the diesel engine has experienced an intake, compression, for power, exhaust four stroke. Diesel pure air sucked in the intake stroke; in the compression stroke near the end of the cylinder, the air pressure of up to 3.5 ~ 4.5MPa, ~~ 1000K temperature up to 750, Meanwhile, the diesel fuel by the fuel injection pump hydraulic raise to more than 10MPa injected into the cylinder through the injector itself immediately after a very short period of time is mixed with air pyrophoric combustion. Driven by high-pressure gas piston downward movement and driven by the crankshaft rotation for power, the exhaust gas is the same through the exhaust pipe into the atmosphere.
Cummins Engine with traditional diesel engine is the biggest difference PT injector that is traditional fuel pump plunger (to generate high pressure) and injector needle (control injection) are integrated, and the abolition of the high pressure tubing, effectively eliminate the influence of high pressure and high speed oil supply pressure fluctuations on the oil law, but higher injection pressure (60 ~ 150MPa, or even higher), not only meet the the enhanced engine required high injection pressure and high injection rate, and atomization, volumetric efficiency is high, is more conducive to the combustion and improve engine performance.
Lack of engine power, in theory, primarily due to the poor combustion gas mixture within the cylinder or the engine moving parts, the frictional resistance is too large. Many reasons lead to poor combustion example: fuel supply shortage, poor atomization, fuel supply advance angle are not allowed to cylinder sealing decline, inadequate intake, poor exhaust valve timing inaccuracy. Excessive frictional resistance mainly due to the moving parts of the engine the gap is too small or inadequate supply of such oil.
Lack of engine power, and continuous row of black smoke, the engine most cylinder or cylinder excessive oil, severe hypoxia imbalance of the fuel and air mixture, combustion, diesel combustion incomplete, suspended free-shaped carbon element with the The exhaust gas discharged together formed. If the exhaust pipe is intermittent row of black smoke, and accompanied by "chug" sound, indicating that the individual cylinder combustion is incomplete. The main reason for that: ① injection pump debugging properly, so that the excessive amount of oil, incomplete combustion. ② the majority of the injector injection of poor quality. ③ oil supply is not correct. (4) the intake valve opening height decreased postpone the turn-on time, leading to inadequate intake. (5) air cleaner element too dirty air filter is installed incorrectly, so that the air is not smooth. ⑥ turbocharger supercharging performance drop. ⑦ fuel quality is too poor.
Engine running unevenly, exhaust pipe a large number of rows of white smoke, poor high-speed operation and acceleration insensitive, and easy too high temperature, the main reasons are: injection advance angle is too small, poor atomization of the fuel injector, the engine temperature is too low, within the cylinder, water or oil, water and the like.
Cummins diesel engine power failure diagnostic and treatment methods
Diagnosis of such failure, proceed should be the most obvious fault feature, follow the outside to the inside, the easier issues first, less demolition for the benefit of basic principles.
1. Exhaust pipe smoky
(1) If the engine suddenly black smoke, but running for some time after the fault disappears naturally, is more due to poor fuel quality, due to impurities in the oil clogged injector caused by the poor quality of jet black smoke exhaust run after a period of high pressure oil impurities are washed away, do not have to deal with such a failure.
(2) If a continuous row of black smoke, consider check intake patency and whether the intake pipe deformation increased intake resistance. Remove the air filter cover, remove the filter and clean the machine re-test after maintenance and observation continue smoky exhaust pipe. If the smoke is significantly reduced, the air filter is too dirty or installation problems, affecting the feed rate, should strengthen the maintenance of the intake system.
(3) If the inlet air to flow freely, you should check whether the injection time with late, too late to fully burn oil too late to make the fuel into the cylinder to be discharged and the formation of black smoke.
(4) serious deterioration in the quality of most injector spray fuel atomization, can not meet the needs of the combustion chamber shape, resulting in a combustible mixture formation difficult part of the fuel is discharged into free carbon, which also contributed to the reason of black smoke a fuel injection, it should also inspect repairs.
(5) Check the fuel quality standard, and should be used in line with the engine at the ambient temperature of the area under the normal work standard diesel.
(6) Check the turbocharger is working properly. When the failure of the turbocharger, the end of the engine intake pressure is decreased, resulting in the compression end temperature, pressure drop, and to affect the fuel spray atomization and combustion temperature.
(7) injection pump repair time is not long, smoky exhaust pipe, you should consider whether the injection pump debugging improper excessive oil, this should be recalibrated fuel injection pump in the amount of oil under various conditions compliance.
(8) If the above normal, and the engine has been running for a long time, could be considered the correct check valve opening height and open time. The long period of use allows the valve train engine wear and misalignment normal valve timing and the valve lift, intake air amount reducing cylinder corresponding increase in the amount of residual gas, and directly affect the full combustion of the fuel.
(9) For speed uneven, intermittent row of black smoke check off the oil law-by-cylinder engine unable to be used for diagnosis. When a cylinder off oil, engine speed decreased significantly reduce black smoke, abnormal noise disappeared, the cylinder oil excessive checks adjustment to cope with the cylinder fuel injection quantity. If the engine speed changes, black smoke disappeared, the poor quality of the cylinder injector spray respond to the injector for inspection. If the engine speed remained unchanged, the cylinder does not work, you should check the high pressure fuel supply situation in the cylinder, check and adjust the PT injector.
2. Row of white smoke exhaust pipe
(1) the lack of engine power, exhaust pipe row of gray smoke, first hand against the muffler exhaust port at the hands left drops of water, you should check whether the water in the diesel and cylinder.
(2) when the engine has just launched to take gray smoke, causes the starter when the temperature is too low, some diesel volatile steam without burning directly discharged due. Gray smoke gradually disappear until the engine temperature is elevated, it is a normal phenomenon. If the engine is just starting to take gray smoke, black smoke and the temperature rises, the cylinder pressure, compression ignition conditions improved, but the diesel is still not complete combustion, the engine is underpowered, and respond to the cylinder pressure checks and maintenance .
(3) the lack of engine power, exhaust pipe row of gray-white smoke is usually fuel injection advance angle is too small or injector atomization due to poor quality. Accompanied by excessive engine temperature, slow speed, you can think is the injector too late, otherwise poor quality fuel injector atomization. Cummins Engine PT injector is integration, the traditional fuel pump plunger injector needle as a whole, regardless of injection time is too late or injector atomization quality is poor PT injector must carried adjustment.