Analysis of railway transport snow-blowing equipment operating modes by diesel generator operation parameters

. Ensuring the transportation process in the Siberian region during the winter months involves protecting the railway infrastructure from external climatic factors, such as snow drifts and icing. To ensure timely clearing of tracks, a wide fleet of snow removal equipment on rails is used, the most numerous of which is the snow removal train type SM-2 and its modifications. The technological cycle of such trains can be reduced to three operations: clearing the track and loading snow mass, transportation to the unloading dead end, unloading and returning to the work site. Reducing both fuel and time resources in each technological link is an urgent task for railways. The purpose of the study is to evaluate the capabilities of monitoring the parameters of a diesel generator for more effective planning of operating modes of snow removal equipment. The current strength of three phases of a diesel generator was measured in various operating modes. The values of the current strength when starting electric drives of various train powers are estimated. The duration of operation of a diesel generator in nominal mode is compared with the operational need to set the operating mode in the technological cycle of clearing tracks from snow.


Introduction
To ensure reliable operation of track equipment, various automated control systems are used to determine the critical states of structural elements and machine components.Further improvement of these systems is associated with forecasting the technical condition, which is necessary for planning measures to prevent the occurrence of defects, eliminating the conditions for their occurrence and calculating the service life based on the actual state of components or mechanisms.
One of the implementations of this approach is the introduction of an automated system for monitoring the operation of special rolling stock "SADKO".Today, the system collects data on the actual volumes of snow removed and the length of the track and, based on these parameters, determines the frequency of maintenance of the snow removal train.The limited use of the system is due to the lack of assessment of the actual condition of one of the main and most technically complex units of the diesel generator machine.
The purpose of the study is to develop methods for assessing the condition of a diesel generator based on output power parameters in real operating modes and to determine the relationship between the operating modes of a snow removal train and the operating modes of a diesel generator [1,2,3].

Materials and methods
On a non-self-propelled snowplow -snow removal train SM-2, already equipped with the SADKO system (AS KRSPS), an additional prototype of the diesel generator parameter monitoring system (SMPD) was additionally installed.The choice of metrological parameters of the system was based on the parameters of the generated current by the GSF-200 synchronous generator, the technical characteristics of which are given in Table 1.The diesel generator parameter monitoring system consists of an electronic unit, an engine speed measurement module and a set of contactless current sensors.The system is located in the diesel room of the head car of the SM-2 machine [4,5].Three SC135-500 Hall effect compensation sensors were used to measure the current.Features of current sensors of this type (Table 2) are linearity and fairly high conversion accuracy, low temperature drift of no more than 0.5 mA in the temperature range from -40 to 85 °C.The need to provide sensors with bipolar power supply (-15…+15) V created difficulties in the design of the electronic unit and led to an increase in its cost [6].The sensors have a closed, one-piece design, therefore, when installing them on the flexible phase busbars of the generator, their mounting was dismantled without exposing the insulation, Fig. 1.The electronic unit is installed in close proximity to the generator, and the system measurement mode is started automatically when the "Ground" contact is turned on [7].Based on the calibration results, a connection was established between the measurement results of the SC135-500 sensors and the actual values of the electric current (Fig. 3).The dependence is satisfactorily described by a linear function with a correlation coefficient greater than 0.9999.Using the least squares method, the approximation coefficients a=1.41 and b=-0.04A were determined for the measurement results with SC135-500 sensors to determine the electric current strength: .

Results and discussion
Monitoring the operating parameters of a diesel generator under real operating conditions made it possible to obtain a synchronized data array of rotation speed and electric current strength in three phases with a time resolution of 2 s.The monitoring results for one work shift are presented in Fig. 4. Experimental data clearly identifies three operating modes of the generator [8].
In the first mode, there is no generator current, the speed is from 800 to 1200 rpm (item 1 in Fig. 4).The team enters this mode when it starts a shift or there is no need to turn on the electric drive.As a rule, in this mode the snow removal train is transported to the place of work or unloading.In the second mode, the operating frequency is (1400 -1500) rpm, there is still no current on the generator, no current on the generator (item 5 in Fig. 4).The duration of this transition regime is significantly shorter than others.The transition is associated with technological pauses in the operation of the machine due to a train stop or another need to turn off the electric drive.
The third mode is clearly identified by the high operating frequency of the engine (1400 -1500) rpm and the consumed electric current of more than 10 A. In this mode, cleaning (item 2 in Fig. 4) and unloading (item 3 in Fig. 4) take place, movement of snow mass along intermediate cars.The constant component of the current graph in harvesting mode is (50±10) A and is associated with the continuous operation of three consumers: electric drives of the inclined conveyor, feeder and intermediate cars.Individual pulses on the time dependence of the current strength are associated with short-term starts and stops of the electric drives of intermediate cars to move the snow mass inside the train from the head car to the tail car.
The stepped components of the current graph, appearing three times at time intervals (1.2 -1.4) ‧104 s, (2.3 -2.5) ‧104 s and (3.5 -3.7) ‧104 s, correspond to the unloading mode of the snow removal train.A typical view of the unloading schedule is indicated by pos. 3 in Fig. 4. At the beginning of this mode, belt conveyors in three cars are simultaneously launched, then, as the snow mass moves to the tail car with a conveyor for ejection in cars freed from snow, the electric drives of the conveyors are turned off.Each shutdown corresponds to a transition to the lower "stage" of the current graph by 10 A. The time it takes to free one car from the snow mass is on average 240 seconds.
Before and after the unloading mode, a low frequency of generator operation is observed for a long time (item 3 in Fig. 4).This is due to the need to move the train from the place of production to the place of unloading and back.In the absence of electrical energy consumers during this period, the team reduces the rotation speed to 1000 rpm.
From the point of view of economical use of resources, the second, transitional mode, which is directly manually controlled by the train driver, is of greatest practical importance.The rotation speed of the diesel generator must be promptly reduced after shutdown and increased before turning on the electric drives (item 5 in Fig. 4).The share of the third, operating mode relative to the total shift time determines the machine utilization rate.At the same time, the share of the second mode indicates the energy efficiency of the driver's actions in controlling the diesel generator.Based on data on the speed and strength of the electric current (Fig. 4), the operating modes of the generator (Fig. 5), controlled by two different drivers, were identified.The total duration of modes in a work shift shows (Table 3), which allows us to evaluate both the efficiency of using a snow removal train and the energy efficiency of controlling a diesel generator [9,10].In the first shift (Fig. 5 a), the transition mode is prolonged, the share of which is 20%, which is twice as much as the share of time in the second shift of 10% (Fig. 5 b).

Conclusion
A prototype of a system for monitoring the parameters of a diesel generator of a snow removal train was manufactured to record the strength of the consumed electric current and the engine speed.The system is located in the diesel room of the head car of the SM-2 machine.
The experimental results recorded contain data on the current strength from the three phases of the diesel generator and its rotation speed with a sampling time of 2 s.The possibility has been demonstrated and software has been developed to determine the operating modes of a diesel generator: idle, transient and working.It has been established that one of the main reasons for the decrease in energy efficiency is associated with the duration of the transition mode, in which the generator operates at high speeds in the absence of electricity consumers.
The influence of the human factor on the efficiency of using the generator was discovered, which was demonstrated by the example of the results of monitoring the work of two different teams.The duration of the transition process in the first team was 20% of the shift duration, which is twice as long as the transition time of the second team -10%.Further development of the topic may be associated with the creation of an automated system for informing the driver about effective diesel generator control operations and assessing the correctness of the actions.

Fig. 1 .Fig. 2 .
Fig. 1.Layout of current sensors for the GSF-200 generator.The sensors were calibrated on a laboratory bench with an ETRO AD32-T400 diesel generator.RGK CM-10 current clamps of an approved type, registered in the State Register of Measuring Instruments under No. 81401-21, were used as a reference measuring instrument (Fig.2).

Fig. 4 .
Fig. 4. Results of monitoring the diesel generator of a snowplow for one work shift: a -electric current strength of the first phase, b -rotation speed.

Fig. 5 .
Fig. 5. Operating modes of the diesel generator of the snowplow of the first (a) and second (b) teams.

Table 3 .
Duration of diesel generator operating modes in two teams.