ENERGY EFFICIENCY OF DIESEL LOCOMOTIVE HYDRAULIC TRANSMISSION TESTS AT LOCOMOTIVE REPAIR PLANT

Dep. «Locomotives», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipropetrovsk, Ukraine, 49010, tel. +38 (056) 793 19 01, e-mail bodnar@nz.diit.edu.ua, ORCID 0000-0002-3591-4772 Dep. «Locomotives», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipropetrovsk, Ukraine, 49010, tel. +38 (056) 733 19 61, e-mail m.i.kapica@ua.fm, ORCID 0000-0002-3800-2920 Dep. «Locomotives», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipropetrovsk, Ukraine, 49010, tel. +38 (056) 733 19 61, e-mail oalexander@mail.ru, ORCID 0000-0002-7719-7214 Dep. «Locomotives», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipropetrovsk, Ukraine, 49010, tel. +38 (056) 733 19 61, e-mail koroman@ua.fm, ORCID 0000-0003-1416-4770


Introduction
Most locomotives with hydraulic power transmission used in Ukraine require overall or overhaul reconditioning. When performing the overhaul one of the complex and responsible diesel locomotive units is hydraulic transmission. After overhauls the locomotive hydraulic transmission is tested without load for the running-in purpose and with load to check the basic settings. Technical specifications of enterprises, which repair diesel locomotive hydraulic transmission, recommend conducting a certain amount of evaluation and regulatory tests to monitor their condition after repair. The quality of these tests results in the transmission resource and its efficiency.
Problem statement. When conducting the overhaul at the Dnipropetrovsk Diesel Locomotive Repair Plant «Promteplovoz» the most energyconsuming is the diesel locomotives hydraulic transmission test stand. Testing of hydraulic transmission in a wide power range is limited by technical capabilities of equipment and existing limits for energy consumption. In this connection the important task is the development of energyefficient method for locomotive hydraulic transmission testing in locomotive repair plant environment.
Previous studies analysis. The problem of improved testing of locomotives with hydraulic transmission is researched in the works [6,7,9]. The research results can partly be used during bench testing of hydrodynamic transmissions in plant environment.
Industry research laboratory (IRL) «Technical maintenance and diagnostics of locomotives» of Dnepropetrovsk National University of Railway Transport named after Academician V. Lazaryan (DNURT) is working to improve testing of locomotive hydraulic transmissions under the conditions of Diesel Locomotive Repair Plant [5,8,11,12].
In [3,4] the author considered the mutual load system of traction electric machines with direct and pulsating current, which allows to use them while bench testing the hydraulic transmission with electric drive and load.

Purpose
Improvement of the technology of plant postrepairs hydraulic tests in order to reduce electricity consumption while testing.

Methodology
There was proposed an energy efficiency method for diesel locomotive hydraulic transmission testing in locomotive repair plant environment.
Base material. The plant uses a typical stand for testing. It consists of the frame on which there is installed the hydraulic transmission, DC electric drive, DC generator for power take-off, remote control. For generator loading the water rheostat is used.
Block diagram of the stand is shown in Fig. 1. To create a moment of resistance during hydraulic transmission testing the water load rheostat is used; the power consumed by rheostat is defined as The stand monitors the following parameters: − the rotary speed of the electric drive motor m n and the load generator g n ; − the armature current m I and voltage m U and excitation winding m_e U of the drive motor and the load generator g_e U .
− oil temperature at the inlet and outlet of the hydraulic transmission; − pressure in lubrication system; − pressure of the hydraulic transmission feed pump.
Hydraulic transmission of type UGP 750-1 200 is designed for joint operation with diesel engine which develops power from 550 … 880 kW. It is not possible to check hydraulic transmission operation in full load range at the existing stand, as the drive motor rated power is 270 kW. Besides, the moment characteristics of the motor do not match with those of the hydraulic transmission that does not allow using full engine capacity. That is why the post-overall bench tests of the hydraulic transmission are carried out in a limited range of loads.
To improve the hydraulic transmission test stand there are the following options of modernization [5,11].
Replacing of the electric drive motor with diesel engine. Installation of diesel significantly complicates the design and dimensions of the stand. Besides, consideration must be given to the fact that when placing the diesel stand within the workshop the noise and exhaust emissions, which occur during the diesel engine operation, will adversely affect the employees. Given the high cost of diesel fuel and other disadvantages, this method is not rational.
Installing the drive motor, which has diesel relevant nominal capacity, will require more powerful motor control system. Along with the cost of the electric motor, this option would require significant capital investments.
One option for modernization is to install the additional electric motor on the stand for more power to the hydraulic transmission input shaft drive. This option has its advantages if the additional electric motor is powered by the stand load generator.
In terms of energy savings spent on drive motor power, the rational option (Fig. 2) is energy returning from the generator to the electric drive motor. To do this, the power converter is switched on instead of the water rheostat in order to regulate the output voltage of the generator according to the operation mode of the drive motor. Since the load generator power depends on the test mode, it is necessary to use a complex system of energy transformation that will provide the opportunity to supply power to additional motor.
Let's consider in more detail the option of installation of additional electric motor for more power on the hydraulic transmission input shaft.
Block diagram of the updated stand for testing hydraulic transmission is shown in Fig. 3. The motor М and the generator G are electric machines designed for loading hydraulic transmission. The motor М is connected to the hydraulic transmission input shaft directly, and the generator G -to the hydraulic transmission output shaft through reduction gear with angular velocity transmission ratio 2 k .

Fig. 3. Modernization option with installation of additional electric drive motor
Additional drive motor add М , designed to cover all losses in the mutual load stand, is connected to the hydraulic transmission input shaft through reduction gear with angular velocity transmission ratio 1 k . The electrical circuit of the test stand is shown in Figure 4. The armatures of the electric motor М and the generator G are connected electrically, forming a loop. The excitation winding of the motor М and the generator G are powered by національного університету залізничного транспорту, 2015, № 6 (60)  Adjusting the hydraulic transmission load moment is performed by changing the current І in the circuit of the motor М and the generator G .
Voltage stabilization at the armature add М stabilizes the angular velocity in ω of hydraulic transmission input shaft. We assume that one of the conditions of hydraulic transmission testing is as follows The second condition, ensuring relative stability of the hydraulic transmission load moment, is armature current consistency М and G Voltage balance [4] in the main electrical cir- where g E , m E -emf of generator and engine, respectively; R ∑ -total ohmic resistance of the main electric circuit. ; where htr k and 2 k -angular velocity transfer ratios of hydraulic transmission and reduction gear, respectively.
For normal mutual load of identical electric machines М and G it is preferably to ensure the following conditions htr av 1 , where htr av k -average value of adjustable transfer ratio htr k . Balance of mechanical moments can be represented as 2 , Adjustment of the current and therefore the load moment of the tested hydraulic transmission can be performed by changing the magnetic flows of motor М and generator G . For a given value of current and angular velocity ratio the magnetic flow ratio is as follows Then the expression for add М takes the form: where in М and in ω -moment and angular velocity at the hydraulic transmission input; htr η -hydraulic transmission efficiency. 1 1 .
in m add

Findings
Based on the conducted analysis the necessity of improving the plant stand testing of hydraulic transmission was proved. The variants of the stand modernization were examined. The test stand modernization analysis was conducted.

Originality and practical value
The possibility of using electric power load generator to power the stand electric drive motor was theoretically substantiated. A variant of hydraulic transmission test stand based on the mutual load method was proposed.