Design and research of plateau Pelton turbine model test bench

ABSTRACT

The impact turbine equipment will be seriously disturbed in the high altitude, water temperature, sediment content and other environments in the plateau area, so that it can not run stably. In this paper, the plateau impact turbine model test bed and data acquisition system are designed. According to the standard of general test bed, the basic parameters of the turbine unit are determined by changing the specific speed method, and the working head of the centrifugal pump is set up to simulate the impact turbine by referring to the characteristics of the plateau water flow drop doing work to the turbine. The structure of torsion meter calibration device used in test bench calibration is designed. The efficiency test and runaway test of the turbine model are carried out on the test bench. The experimental results show that the test bench can effectively test the performance and hydraulic performance parameters of the turbine in the plateau environment, and the test accuracy meets the requirements of the turbine model IEC-60193, which provides test support for the performance research and application of the turbine in the plateau environment, and has important engineering application value.

Keywords: Plateau area; Impact turbine; Test bench design; Data collection; Error analysis

1. INTRODUCTION

As a special type of turbine that can utilize altitude to obtain more efficient kinetic energy, the impingement turbine is particularly suitable for use in plateau areas. However, conventional impulse turbines have a series of problems in plateau environments, for example, due to the lower atmospheric pressure and lower gas density in plateau areas, the intake of the impulse turbine is lower, which affects the energy conversion efficiency of the turbine. The high sediment content in the atmosphere and water makes the wear and tear of various components of the hydraulic turbine increase during operation, resulting in lower performance. Meanwhile, the complex climatic conditions in the plateau region, with large changes in air pressure and temperature, can lead to unstable performance of the turbine and even shutdown phenomenon [¹]. Currently, impact turbine test bed models are commonly used in the industry t+o simulate conditions in different environments [²]. The impact hydraulic turbine test bed model has the advantages of high controllability, high safety, high economy and time efficiency, high flexibility and repeatability, and low loss [³], which makes it of greater application value when testing and evaluating hydraulic turbine performance in plateau environments, and at the same time solves the difficulties and unfavorable factors faced in field tests.

Research institutes at home and abroad have carried out a lot of research and practical work on hydraulic turbine model test rigs, and not only have the test methods begun to be diversified, but also the accuracy of data collection and calculation has become higher and higher. Niyonzima J B proposed to use the open flow of an actuator control valve to perform remote efficiency and flow rate performance tests on a small Banki-Michell turbine [⁴]. Deschênes C in 2014 studied different flow phenomena inside the hydraulic turbine to build a vortex turbine test bed within the Laval laboratory to accurately test key parameters of hydraulic flow such as flow velocity, pressure distribution, vortex intensity and turbulence level, and analyzed in depth the direct effect of the runner geometry on the hydrodynamics and the performance of the turbine, which provides a certain guidance to the practical applications [⁵]. Velichkova R modeled the tidal energy turbine model as well as built a test bed in 2022, and measured the flow rate of the river after initial tests, but it is not yet in use [⁶]. Leisten C presented the successful control of the predicted speed of a modeled test bed using a controlled load application system to replace the rotor and motor [⁷]. Although the development of China’s hydraulic turbine test bench is late, the technology has been rapidly upgraded since the opening of the high head test bench in 1984. After the Three Gorges Project, the test technology has leaped, with significant contributions from China Academy of Water Resources and Hydropower, Harbin Electric Power Plant, etc. Tsinghua University has even built the world’s highest altitude test bench to lead the high-altitude design reference.

For turbine data acquisition and analysis, Hasmatuchi V installed a new universal test stand in the hydraulic laboratory, which was controlled through a LabVIEW interface and designed an advanced test stand tuning method to keep the parameters constant, successfully realizing the data storage, acquisition, and sharing of model tests [⁸]. Viral R proposed a computerized data acquisition system for monitoring hydraulic performance parameters and electrical parameters of pumps in order to collect data, and the test results are useful for remote wireless monitoring of small hydroelectric power plants [⁹]. Aiming at the problem of unstable unit operation caused by pressure pulsation in the tailwater pipe of hydraulic turbine, Bay Jingmao used LabVIEW to analyze the time-frequency domain of several working conditions with large amplitude of pressure pulsation under the four water heads, which provides certain guidance for the safe and stable operation of hydraulic turbine [¹⁰]. Zhenkai Zhang, in order to solve the problem of more unknown parameters needed to calculate accurate hydraulic turbine flow, designed LabVIEW’s internal algorithms to measure various parameters in real time and easily, which were successfully used in practical applications [¹¹]. Aiming at the problems of low measurement accuracy, low automation and complicated operation of the traditional hydraulic turbine model test stand, Deyou Li realized data acquisition, data management, curve fitting and other works based on the NI platform, and successfully applied them in the Harbin test stand [¹²]. Huang Tu introduced the design of hydraulic turbine efficiency test system based on LabVIEW, which realized the real-time monitoring and post-analysis processing of each data of the hydraulic turbine efficiency test, and was successfully applied in the actual practical engineering [¹³]. Aiming at the current hydraulic turbine condition monitoring which cannot be centralized in an independent and complete system, Zhou Lihua proposes to design and develop a hydraulic turbine condition monitoring and diagnosis system based on LabVIEW platform, which provides an important technical reference for the field personnel [¹⁴]. In response to the shortcomings of the traditional methods of detecting the operating status of hydraulic turbines, such as complex operation, low efficiency and inaccurate results, Sun Biao designed a hydraulic turbine state analysis system using LabVIEW, which has a better development prospect and practical value in the field-oriented applications [¹⁵].

At present, the hydraulic machinery test bench is mainly in the plains, the test needs to be stabilized before data acquisition and analysis, for the plateau region is still a lack of mature design and corresponding data acquisition system, researchers can not be tested in the real plateau environment, can not get accurate test data, so it is difficult to study in-depth the performance characteristics of the hydraulic machinery in the high-altitude environment.

Based on the above analysis, the main research objectives of this paper are to design an impact hydraulic turbine model test bench based on the plateau environment, which can operate stably in the plateau environment, to develop the corresponding data acquisition system software, to complete the routine test of the hydraulic turbine as well as to realize the collection and analysis of the test data.

2. DESIGN AND CONSTRUCTION OF IMPACT HYDRAULIC TURBINE TEST BED

2.1. Impact turbine overview and test stand requirements

Impact turbine, as the key equipment for water energy conversion, utilizes high-speed water flow to impact the bucket runner to convert water energy into mechanical energy. Its core components include water distribution ring tube, nozzle, runner and frame. Nozzle design and hopper structure are critical to turbine performance, controlling the speed and direction of water flow by adjusting the nozzle shape and angle to optimize energy conversion efficiency. The special design of the hopper converts the impact energy of the water flow into kinetic energy, which pushes the rotor to rotate and in turn generates electricity through the generator. In recent years, technological advances such as visualization tests, computational fluid dynamics, finite element analysis and AI optimization design have significantly improved the performance research and design of impact turbines [¹⁶]. Especially in high plateau environments, its high head and wide range of operating conditions advantages make it a core technology for high head hydropower development. Although China’s impact turbine technology started late, but in the plateau environment has made a series of research results, especially in the past two decades, has made breakthrough progress [¹⁷,¹⁸,¹⁹,²⁰,²¹].

In view of the special environmental conditions in the plateau region, the design of the test stand needs to give special consideration to the influence of thin air and low air pressure on the performance of the hydraulic turbine. According to the standards for general purpose test rigs [²²,²³,²⁴,²⁵], this test rig mainly consists of a centrifugal pump and an impingement turbine unit, with the centrifugal pump head being used to simulate the plateau head in order to assess the performance of the turbine under high altitude conditions. In the design, the pumping unit is placed at the ground level to reduce the vacuum and ensure the efficient operation of the pump. By setting up diversion pipes and high-precision electromagnetic flow meters, precise control and monitoring of water flow are realized to optimize the operating efficiency of the hydraulic turbine. Considering the special characteristics of the plateau environment, the test bench adopts low-temperature-resistant materials and high-pressure equipment to ensure stable operation under low-temperature and high-pressure conditions. In addition, the torque meter is calibrated to improve the precision of measurement in the plateau environment and ensure the accuracy of test data. Through these designs, the test stand is able to simulate the plateau environment and comprehensively evaluate the performance and stability of the hydraulic turbine. The three-dimensional diagram of the test stand is shown in Figure 1.

Figure 1
Three-dimensional drawing of the test bench: 1. Stabilizer tank 2. Centrifugal pump 3. Operator 4. Dynamic motor 5. Hydraulic turbine.

2.2. Calculation of turbine parameters

According to the characteristics that the working parameters of the impact turbine test bed will be affected in the plateau condition, the bucket turbine is used, and Table 1 shows the basic parameters of this test bed.

Table 1
Basic parameters of the test bench.

HYDRAULIC TURBINE UNIT	SIGN	UNIT	NUMERICAL VALUE
Maximum head of turbine	Hmax	m	130
Minimum head of turbine	Hmin	m	60

According to the above data, referring to the calculation formula of the basic parameters of the impact turbine, the basic parameters of the unit are determined by changing the specific speed method.

From the specific speed formula, it can be obtained:

(1) $$Q=\frac{N}{gH\eta }$$

(2) $$N=\frac{P}{{\eta }_1}$$

Where, N is the rated power of turbine; P is the rated power of turbine-generator unit; η₁ is the rated efficiency of generator; η is the turbine efficiency;

The generator rated power is 0.05MW, and substituting the data into the equation yields a rated flow Q of 0.060 m³/s for the turbine.

It is obtained from the formula for the specific speed of the turbine:

(3) $$n=\frac{n_{s1}{H}^{\frac{5}{4}}}{\sqrt{P_1}}$$

(4) $$N_1=\frac{N}{K_r{Z}_o}$$

Where, n_s1 is the specific speed of the runner corresponding to the nozzle; N₁ is the power of a single nozzle in an impulse turbine; K_r is the number of runners; Z_o is the number of nozzles on a single runner of an impulse turbine;

The value of n_s1 is generally 21–23, for the nozzle impulse turbine rated unit speed is about 40rpm for n₁₁, according to the speed of the impulse turbine to select the generator speed of 1500rpm.

After the water flow is ejected from the nozzle, it first contracts and then disperses, and the diameter of the jet is the diameter of the water flow ejected from the nozzle contracted to its smallest point. For the impact turbine with multiple rotors and multiple nozzles:

(5) $$Q=Kr{Z}_0\frac{\pi d_0^2}{4}{v}_0=Kr{Z}_0\frac{\pi d_0^2}{4}\phi \sqrt{2}gH$$

Where, Q is the total flow of turbine; d₀ is the nozzle jet diameter; v₀ is the nozzle exit jet velocity; φ is the jet velocity coefficient of nozzle;

The velocity coefficient is generally taken as 0.97~0.98, and from the above equation, it can be known that for the impact turbine with single runner and single nozzle as:

(6) $$d_0=0.545\sqrt{\frac{Q}{H^{0.5}}}$$

Substituting the known parameters into Equation (6), the jet diameter d₀ of the impingement turbine can be obtained as 0.037m.

Nozzle in the jet stream, the jet diameter will shrink smaller. Taking into account the contraction of the jet, so the demand for the nozzle outlet diameter d_n is greater than the jet diameter d₀ , the following formula can be used in the calculation:

(7) $$d_n=\epsilon d_0$$

Where, ε is the coefficient;

The coefficient range is generally between 1.05 and 1.25, take the coefficient of 1.10 and substitute it into the formula (7) to calculate the diameter d_n of the nozzle of the impulse turbine as 0.040m.

The runner diameter is calculated as:

(8) $$D_1=\frac{60u}{\pi n}$$

(9) $$u=\phi \sqrt{2}g{H}_{av}$$

Where, u is the total flow of turbine; φ is the nozzle jet diameter; H_av is the nozzle exit jet velocity;

Figure 2
Characteristic curve of power water pump.

Calculated from the above formula, the diameter D₁ of the runner is 0.33m.

The number of buckets for the efficiency of the turbine has a very big impact, the number of buckets is too small, will make part of the jet can not fall on the bucket and the formation of volumetric loss; the number of buckets is too much on the bucket of the water is not favorable, it is generally desirable:

(10) $$Z_0=6.67\sqrt{\frac{D_1}{d_0}}$$

Combined with the design requirements of the test stand and the calculation results, the number of buckets Z₁ of the turbine was selected to be 26.

2.3. Selection of main components of test bench

This test bench mainly consists of centrifugal pump, pressure stabilizing tank, impulse hydraulic turbine unit and flow control and measuring elements. Under the plateau environment, the selection of the main components of the impulse hydraulic turbine test stand needs to take into account the special climatic and environmental conditions of the plateau region, so that the influence of the altitude, atmospheric pressure, air temperature and water temperature on the cavitation of the hydraulic turbine, the installation elevation and the mechanical operation is reduced to the operable range, so as to ensure that the test stand can operate stably and meet the performance requirements under such environment.

Centrifugal pump: MD type multi-stage sectional centrifugal pump is selected, which has the characteristics of adapting to high altitude, wear-resistant and long life and suitable for conveying liquids containing solid particles. Considering the head loss and system demand, the centrifugal pump with head greater than 130m is selected.

Pressure stabilizing tank: a tank design with a length of 2.6m and a pipe diameter of 2.6m is used to ensure stable system pressure. According to the needs of the system preliminary selection of 14m³ pressure stabilizing tank, its specific size and volume need to be adjusted according to the actual centrifugal pump parameters.

Solenoid valve and electromagnetic flowmeter: DN200 distribution of direct-acting, normally open type of solenoid valve, to ensure the stability of the fluid channel during the operation of the test bench. DN200 caliber, flange structure, lined with polychloroprene rubber electromagnetic flowmeter, suitable for fluid measurement containing abrasive particles.

Impact turbine unit: A highland impact turbine unit with a bolted connection between the runner and the hopper, hydraulic and manual adjustment of the nozzle mechanism, and a transparent casing to facilitate observation and study of the internal flow pattern was selected. The three-dimensional diagram is shown in Figure 3.

Figure 3
Three-dimensional drawing of hydraulic turbine unit:1.Hydraulic turbine shell 2.Hydraulic turbine.

3. TORQUE METER CALIBRATION

3.1. Torque meter sensor calibration method

Select the force arm lever plus high-precision weights to act directly on the shaft for static calibration of torque. This method belongs to a kind of mechanical calibration method, although the operation process is slow, but it is suitable for various environments, with high precision, small error and good stability. Among them, the measurement of the torque value is optimized and calculated on the basic principle of the product of force arm and force, and the specific formula is:

(11) $$T=(A_{T0}+A_{T1}\times V_1+A_{T2}\times V_1^2)\times g_M\times L_M$$

Where, g_M is the standard weight; L_M is the lever length; A_T is the calibration coefficient;

The design of this test bench requires the application of torque in the vertical direction, and the stability of the overall area in the plateau environment is poor, in order to avoid accidental movement and sliding in the horizontal direction, this device is vertically mounted, the specific schematic diagram is shown in Figure 4.

Figure 4
Schematic diagram of torque meter calibration device: 1. dynamometer motor 2. model unit 3. torque meter sensor 4. cutter bearing 5. steel belt 6. calibration weight 7. loading machine 8. universal drive shaft 9. hydrostatic bearing of hydraulic turbine 10. friction force sensor

3.2. Torque meter calibration test

In this test, the electrical signal generated by measuring the torque is converted to voltage output as a way to get the corresponding load value. The expression of the functional relationship is:

(12) $$T=K_1\times V\times K_0$$

Where, T is the physical quantity; V is the sensor voltage; K is the calibration coefficient;

The main torque transducer calibration data is shown in Table 2.

Table 2
Torque sensor calibration data.

NO	PS (kg)	V (V)	PC (kg)	ΔP = PC − PS(kg)	ERR = ΔP/FS (%)	FS (kg)
1	140	7.53013	140.01179	0.01179	0.00590	200
2	140	7.53011	140.01139	0.01139	0.00569	200
3	120	6.45566	120.02090	0.02090	0.01045	200
4	120	6.45451	119.99955	−0.00045	−0.00023	200
5	100	5.37938	99.99658	−0.00342	−0.00171	200
6	100	5.37906	99.99048	−0.00952	−0.00476	200
7	80	4.30416	79.99179	−0.00821	−0.00411	200
8	80	4.30357	79.98087	−0.01913	−0.00957	200
9	60	3.22843	59.97763	−0.02237	−0.01119	200
10	60	3.22839	59.97690	−0.02310	−0.01155	200
11	40	2.15592	40.02328	0.02328	0.01164	200
12	40	2.15250	39.95971	−0.04029	−0.02014	200
13	20	1.08323	20.06559	0.06559	0.03279	200
14	20	1.07936	19.99355	−0.00645	−0.00322	200

The functional relationship is given by:

(13) $$PC=-0.08813+18.61V$$

The torque calibration and error plots are shown in Figures 5 and 6 respectively.

Figure 5
Torque calibration diagram.

Figure 6
Error graph.

The final torque meter is calibrated to be within ±0.1% error and the indicator meets the requirements.

4. ANALYSIS OF DATA COLLECTED FROM TEST BENCH MODEL TESTS

4.1. Comprehensive error analysis of the test bed model

Ten repetitive measurements were taken for the same operating condition under stable operating conditions, and the random error of the efficiency test was calculated by analyzing the degree of dispersion obtained from these measurements, the formula is:

(14) $${(E_{\eta })}_r=\frac{T_{0.95}(N-1)\times S_{\overline{\eta }}}{\overline{\eta }}\times 100\%$$

(15) $$T_{0.95}(N-1)=T_{0.95}(10-1)=2.262$$

Where, S is the standard error of the mean of the N efficiencies; T_0.95(N − 1) is the corresponding to a t-distribution value with 0.95 confidence probability and (N − 1) degrees of freedom;

(16) $$S_{\overline{\eta }}=\frac{\sqrt{{\displaystyle \sum _{i=1}^n{({\eta }_i-\overline{\eta })}^2}}}{\sqrt{N(N-1)}}$$

Where, N is the number of measurements;

Ten repeatability tests were conducted at the optimal operating conditions and the random error values of the experimental results were calculated. Table 3 shows the repeatability test data at the optimum efficiency condition (energy) of the impingement turbine model.

Table 3
Repeatability test data for optimal efficiency conditions.

NO.	N11(r/min)	Q11(l/S)	ηhoptM(%)
1	39.25	533.81	89.91
2	39.27	534.72	89.76
3	39.27	534.86	89.82
4	39.27	535.18	89.86
5	39.26	534.92	89.86
6	39.27	534.49	89.97
7	39.27	534.18	89.89
8	39.26	534.24	90.06
9	39.25	534.38	89.8
10	39.25	533.6	89.92

Substituting the data in the above table into the formula gives η_hoptM is 89.885, S_n is 0.0275, and (E_n) is 0.0692%, so the final calculated random error is 0.0692%, and this error is less than ±0.07%, which is in line with the acceptance criteria of the impact hydraulic turbine test bed model.

The system error is finalized by obtaining the square and root calculations of the flow, head, torque, and speed measurement errors.

(17) $${(E_{\eta })}_s=\sqrt{E_Q^2+E_H^2+E_T^2+E_n^2}$$

Where, E_Q is the flow measurement error; E_H is the head measurement error; E_T is the torque measurement error; E_n is the speed measurement error;

The flow measurement error is mainly composed of two parts, which are the primary calibration equipment error and the flowmeter calibration error. The flow measurement error is ultimately derived from the square and root of these two errors.

1. Primary calibration equipment errors.

(18) $$E_{QP}=\sqrt{E_{QH}^2+E_{QF}^2+E_{QW}^2}\le \pm 0.074\%$$

Where, Systematic bias error E_QH ≤ ± 0.07% ;Deflector timing error E_QF ≤ ± 0.022% ;Water density measurement error E_QW ≤ ± 0.01%;

Flowmeter calibration error: through the actual test and calibration data in the error of ± 0.01%.

2. Flow test error.

(19) $$E_Q=\sqrt{E_{QP}^2+E_{QS}^2+}\le \pm 0.074\%$$

Where, E_QS is the flowmeter error;

The measurement error E_H is mainly composed of two parts: static head error and dynamic head error.

Static head error: Part of the accuracy from the calibration pressure calibrator, the other part is the maximum error in the calibration results of the differential pressure sensor, the final result of the size of the error, the formula is:

(20) $$E_{HP}=\sqrt{E_{HPO}{}^2+E_{HPc}{}^2}\le \pm 0.083\%$$

Where, Systematic bias error E_HPO ≤ ± 0.10%; Deflector timing error E_HPC ≤ ± 0.10%;Dynamic head error: generally taken E_HD ≤ ± 0.10% ;

The head measurement error is:

(21) $$E_H=\sqrt{E_{HP}{}^2+E_{HD}{}^2}$$

From equation (18), the head measurement error can be calculated within ± 0.087%.

Torque measurement errors mainly include electromagnetic torque E_T1 and turbine bearing friction torque and wind loss measurement errors E_TF. The torque formula is:

(22) $$T=T_1+T_f+F·L+T_f$$

Where, F is the dynamometer to measure the force of the arm; L is the dynamometer arm length; T_f is the hydraulic turbine bearing friction torque;

The error value of the moment T₁ on the dynamometer arm is E_T1:

(23) $$E_{T1}=\frac{e_{T1}}{T}\le \pm 0.091\%$$

Among them:

(24) $$e_{T1}=T_1{\left[{(\frac{e_f}{F})}^2+{(\frac{e_L}{L})}^2\right]}^{\frac{1}{2}}$$

Where, e_T1 is the absolute error of torque T₁ ; e_f is the absolute error of the force F ; e_L is the absolute error of length measurement L ;

Turbine Bearing Friction Torque and Wind Loss Errors E_TF measured by sensors on the force arms, E_TF ≤ ± 0.07% is measured by sensors on the mounted bearings.

The torque error is:

(25) $$E_T=\sqrt{E_{T1}{}^2+E_{TF}{}^2}$$

From equation (12), the head measurement error can be calculated to be within ± 0.115%.

On the hydraulic turbine model test rig, the main shaft is equipped with a 60-tooth tacho disk for speed measurement. The speed disk was tested at 1000 r/min under standard test conditions and the speed sensor used had a measurement error of ±1 pulse. This error is used to calculate the measurement error E_n of the speed when the sampling period is 20 seconds.

(26) $$E_n=\frac{\mathrm{\Delta }p}{N}\times 100\%$$

The measurement error of the rotational speed is calculated from equation (13) as 0.0054%.

The comprehensive error of the model efficiency test mainly contains three parts, which are the systematic error, random error, and comprehensive error in the determination process of the model efficiency test, which are combined with the above formulas to arrive at the calculation results:

Systematic errors in model efficiency measurements:

(27) $${(E_n)}_s=\sqrt{E_Q^2+E_H^2+E_T^2+E_n^2}\le \pm 0.0184\%$$

Random errors in model efficiency measurements:

(28) $${(E_n)}_r=\frac{T_{0.95}(N-1)\times S_{\overline{\eta }}}{\overline{\eta }}\times 100\%\le \pm 0.10\%$$

Combined error in model efficiency determination:

(29) $$E_{\eta }=\sqrt{{(E_{\eta })}_s{}^2+{(E_{\eta })}_r{}^2}\le \pm 0.20\%$$

4.2. Efficiency and fugitive test results

The efficiency test in this paper adopts constant head and variable speed to reduce the efficiency measurement error due to the head change, and the test is conducted by adjusting the nozzle opening to simulate the different operating conditions encountered by the turbine or pump in the plateau environment, and carry out the efficiency test at different speeds under various openings, and this model test is only carried out under the condition of 1 nozzle, and some of the experimental data under different openings are shown in Table 4. The model test efficiency curve is shown in Figure 7.

Table 4
Efficiency test data.

NO.	A0 (mm)	HM (m)	Q11 (l/S)	QM (l/S)	N11 (r/min)	NM (r/min)	ETAM (%)
1	6	90.18	103.79	11.69	34.2	812.03	84.12
2	6	90.16	103.12	11.61	35.47	841.89	85.6
3	6	90.13	103.53	11.66	36.72	871.6	85.81
4	9	98.06	103.18	12.12	45.71	1131.48	82.92
5	9	106.5	150.94	18.47	34.09	879.43	85.83
6	9	106.55	150.99	18.48	35.28	910.41	86.58
7	12	104.52	193.82	23.5	34.08	871	86.69
8	12	104.59	194.07	23.54	34.84	890.71	87.3
9	12	104.52	194.09	23.53	35.98	919.61	87.63
10	15	107.1	233.37	28.64	34.04	880.68	87.18
11	15	107.13	233.32	28.64	35.17	909.97	87.94
12	15	107.2	233.65	28.69	36.3	939.72	88.56
13	18	104.92	267.29	32.47	34.4	880.81	87.36
14	18	104.95	267.26	32.47	35.53	909.97	88.23
15	18	104.89	267.33	32.47	36.72	940.11	88.8
16	21	105.36	296.94	36.15	34.32	880.67	87.33
17	21	105.24	297.46	36.19	35.45	909.17	87.99
18	21	105.24	296.75	36.1	36.66	940.28	88.99
19	24	103.67	322.34	38.92	34.18	869.93	86.84
20	24	103.68	322.86	38.99	35.38	900.55	87.86
21	24	103.63	323.48	39.05	36.54	929.83	88.72
22	27	101.89	344.16	41.2	34.06	859.62	86.24
23	27	101.88	344.52	41.24	36.05	909.62	88.3
24	27	101.92	344.6	41.26	37.23	939.57	89.24
25	30	100.42	362.44	43.07	34.31	859.51	86.77
26	30	100.46	362.51	43.09	35.5	889.58	87.68
27	30	100.46	362.34	43.07	36.71	919.93	88.79

Figure 7
Efficiency test curve.

Flyaway tests were also conducted with constant head and variable speed, and the flyaway tests were conducted at different opening levels by adjusting the needle opening. At the same time, a simple comparison of the maximum escape speed, the model test in the opening of one nozzle conditions. The test data under different openings and different working conditions are shown in Table 5. The results of the flyaway test under single nozzle condition are shown in Figure 7.

Table 5
Runaway test data.

NO.	A0 (mm)	HM (m)	Q11 (l/S)	QM (l/S)	N11 (r/min)	NM (r/min)	ETAM (%)
1	6	25.06	106.71	6.34	70.39	881.03	−0.03
2	9	24.97	152.94	9.06	71.14	888.81	−0.54
3	12	24.97	195.84	11.61	72.87	910.4	0.34
4	15	25.05	235.05	13.95	74.51	932.27	0.5
5	18	25.04	269.27	15.98	75.12	939.76	−0.13
6	21	25.11	300.46	17.85	75.91	950.9	−0.2
7	24	25.07	325.28	19.31	75.99	951.09	−0.11
8	27	25.03	346.56	20.56	76.38	955.42	−0.1
9	30	25.07	365.07	21.68	76.04	951.73	0.23

The results of the efficiency test show that the turbine has a certain stability under different operating conditions, and thus can also run smoothly in the plateau environment; the ideal efficiency curve usually shows a certain symmetry and reaches a peak at a certain point, which represents the highest efficiency of the turbine at a specific rotational speed, and the trend of the test curve is in line with the ideal state; the efficiency test results of the system have a higher accuracy and stability of this system are high.

From the results of the flyaway test in Figure 8, in the single nozzle conditions, with the opening of the larger and larger, flyaway speed and flow rate increases, and then reach the maximum speed for a period of time after the speed began to decline, the speed of the speed in the A0 = 27 when the speed reaches a maximum, the unit flyaway speed of 76.38r/min, the work of the flyaway speed for the rated speed of the 1.8 ~ 1.9 times, in the maximum flyaway speed Under the working conditions, the fugitive speed is 1.8~1.9 times of the rated speed, and the maximum fugitive speed can be safely operated to meet the test requirements.

Figure 8
Escape test curve.

5. CONCLUSIONS

In this paper, a hydraulic turbine model test rig is designed and constructed to simulate the plateau environment, and a centrifugal pump is used to simulate the working head to successfully test the performance of various components of the impulse hydraulic turbine. Through precise calculation and component selection, the high reliability and stability of the test bench are ensured, and the performance parameters of the hydraulic turbine under plateau are effectively measured.

In order to cope with the impact of the plateau environment on the performance, additional torque meter calibration device is installed to ensure the measurement accuracy through function fitting and error analysis.

The test system follows the IEC-60193 standard[²⁶], and the data acquisition and efficiency test errors are up to the standard, which is suitable for hydraulic turbine model test and acceptance, and lays a solid research foundation. The test bench supports a number of routine tests, including torque meter calibration, efficiency and fugitive tests, and the test accuracy is in full compliance with the IEC standard, which provides powerful data support for the research and application of hydraulic turbine performance.

6. ACKNOWLEDGMENTS

The author is deeply honored and grateful to have the attentive guidance of his teachers, the firm support of his parents, and the warm companionship of his classmates and friends along the way of his education. These valuable experiences have not only shaped the author, but also given him the strength to move forward. The author sincerely wishes that everyone who has helped him will have a successful career and a happy family in the future, and that our friendship will be like a bright star, which will always illuminate each other’s way forward, and we will write a more brilliant chapter together.

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Publication Dates

• Publication in this collection
  09 Dec 2024
• Date of issue
  2024

History

• Received
  31 Aug 2024
• Accepted
  22 Oct 2024