Improving the efficiency of diesel 10D100M
Since 1987, 2TE10U diesel locomotives with 10D100M diesels have been operating on the Belarusian road. Compared to the basic version, the minimum idle speed has been reduced to 270 rpm, the gear ratio from the shaft to the mechanical supercharger has been reduced to 8.87 (instead of 10), the cam profile of the fuel pump drive with a constant plunger speed has been used, and dual-mode injectors have been used. This made it possible to improve the technical and economic performance of diesels.
However, their operational experience has shown a deterioration in the fuel combustion process, increased diesel smoke when operating in partial modes, and ignition of exhaust windows. The large variation in the degree of ignition of exhaust windows in different diesels indicates that the quality of combustion in them is different and depends on the amount of fuel supplied to the cylinder. After examining the process of fuel supply to the cylinders at idle, it was found that the unevenness of its distribution can reach 200%, i.e. the fuel supply to the cylinder stops.
To determine the fuel supply parameters, the fuel equipment with a new fuel pump drive cam profile was tested at the Belarusian State University of Transport (BELGUT) at the Department of Diesel Locomotives and Heat Engines. The test results showed that the fuel supply increases at all speed modes, and the load characteristics are more linear. This is due to an increase in dynamic pressure, as well as a decrease in the amount of fuel flowing from the high-pressure system when the fuel is cut off by the plunger.
The load characteristics of the fuel pump with the new cam profile have a greater steepness in the area of low fuel supplies, since with a decrease in the outlet of the rail, the fuel is additionally cut off by the end of the vertical groove of the plunger. This leads to a sharp increase in the uneven fuel supply through the cylinders when the diesel engine is idling at 20 fuel pumps.
An analysis of the dependencies of the maximum pressures at the ph pump, under the nozzle needle rs and in the pipeline p0 on the cyclic supply for the fuel equipment of the 10D100M diesel engine with serial and new cam profiles showed the following. The residual pressures in the pipeline p0, at the pump ph and under the nozzle needle pc remained almost at the same level at a shaft rotation speed of n = 850 rpm (with a new cam profile) up to a cyclic supply of 0.15 g/cycle.
When applied from 0.15 to 0.38 g/cycle, the pressure of pH and pc increased by 2-3 MPa and decreased by 5-12 MPa with a cyclic supply from 0.38 to 0.54 g/cycle. The pressure at the ph pump at n = 400 rpm (serial) and n = 280 rpm (new cam profile) remained at the same level, and the pressure under the nozzle needle decreased by 2.5 MPa over the entire range of cyclic feeds with the new cam profile. When the 10D100M diesel engine is operating according to the diesel characteristics, there is also a decrease in fuel spray pressure compared to the basic version.
To improve the mixing and improve the quality of fuel combustion in a 10D100M diesel engine, the following technical solutions have been investigated:
-increase the tightening pressure of the nozzle needle from 21 to 28 MPa;
- replacement of ten dual-mode nozzles in the left row with single-mode nozzles with volume displacers;
- turning off the fuel pumps in the left row when the diesel engine is idling;
- adjusting the diesel engine to evenly distribute fuel across the cylinders at idle.
Bench tests of a fuel pump with a new cam profile have shown that an increase in the nozzle needle tightening pressure to 28 MPa leads to an increase in fuel injection pressures at all speed modes. Figures 1 and 2 show the dependences of the maximum pressures ph and pc on the cyclic feed at cam shaft rotation speeds n = 280 and 850 rpm and nozzle needle tightening pressures rz = 21 and 28 MPa.
An increase in the tightening pressure of the nozzle needle leads to a delay in opening the needle and shortening the fuel supply time. In the nominal operating mode, the delay is 0.6, and the reduction in feed time is 2 degrees of cam shaft rotation angle. Turning off one row of fuel pumps at idle allows you to increase the cyclic fuel supply through the nozzle (almost twice), which increases the fuel spray pressure, as the needle rises by a large amount (see Fig. 2).
To assess the impact of the proposed technical solutions on the efficiency of the 10D100M diesel engine, the diesel locomotive 2TE10U-0195(A) was tested at the Gomel depot on the diesel locomotive 2TE10U-0195(A) with fuel consumption measurement for two variants: serial — needle tightening pressure (p3) 21 MPa, dual—mode injectors; experimental - p3 = 28 MPa, single-mode nozzles with volume displacers. The results of fuel consumption measurements based on diesel characteristics are presented in Table 1.
Tests have shown that increasing the tightening pressure of the nozzle needle by 7 MPa increases the efficiency of the diesel engine and practically does not affect the maximum combustion pressure of the fuel through the cylinders in the nominal mode.
When the diesel engine was idling, in both variants, the hourly fuel consumption was measured at ten and twenty fuel pumps. The minimum consumption is fixed when the diesel engine is running on ten fuel pumps in both versions. Increasing the tightening pressure of the nozzle needle and adjusting the uniformity of fuel distribution across the cylinders in idle mode reduced the hourly fuel consumption by 9.3%.
The toxicity of diesel exhaust gases was also investigated at the serial nozzle needle tightening pressure and increased by 7 MPa. During the experiments at the 4th, 8th, 10th and 15th positions of the driver's controller, the concentration of the following exhaust gas components was measured: nitrogen oxide (with subsequent conversion to nitrogen dioxide), carbon monoxide, soot - substances that most pollute the atmosphere
Thus, with an increase in the tightening pressure of the nozzle needle, the content of nitrogen dioxide, carbon monoxide and soot in the exhaust gases decreases. The greatest decrease in nitrogen dioxide content in the exhaust gases (by 50-55%) is observed when the diesel engine is operating in the range from the 10th to the 15th position of the driver's controller. The carbon monoxide content in the exhaust gases (up to 45%) also decreases with increasing load. The greatest reduction in soot content (up to 30%) occurs under medium load conditions
In addition, the toxicity of exhaust gases during diesel engine idling at 10 and 20 fuel pumps with serial and increased nozzle needle tightening pressures was investigated. The measurement results are shown in Table 2.
The table shows that when the tightening pressure of the nozzle needle increases and the diesel engine is running on 10 fuel pumps, the content of nitrogen dioxide, carbon monoxide and soot in the exhaust gases of the diesel decreases, indicating a more uniform distribution of fuel through the combustion chamber. The zones of local over-enrichment of the mixture are reduced, which reduces the emission of incomplete combustion products.
Comparative operational tests of upgraded 10D100M diesels and 2TE10U diesel locomotives were conducted at Gomel depot. They were equipped with single-mode (left row) and dual-mode (right row) injectors with needle tightening pressure increased to 28 MPa, switched to idling mode for ten fuel pumps (instead of twenty). After rheostatic tests, the diesels were additionally adjusted for the uniformity of fuel distribution across the cylinders in idle mode.
Tests have shown that switching diesel engines in idle mode to one row of fuel pumps does not affect the condition of the diesel oil (the oil viscosity is within the normal range). The reliability of the injectors and the average needle tightening pressure drop between the TO-3 are practically the same as for injectors with serial needle tightening pressure.
During the 12 months of operational testing, the volume of transportation work by experimental diesel locomotives amounted to 13% of the total volume of work by 2TE10U diesel locomotives. At the same time, the consumption of diesel fuel per unit of transportation work performed by experimental diesel locomotives turned out to be less by 2.9% compared to serial ones.
Doctor of Technical Sciences R.K. GIZATULLIN,
Candidate of Technical Sciences S.I. SUKHOPAROV,
engineer Yu.G. SAMODUM, BelGUT, Gomel
