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Pulsed Portable Magnetohydrodynamic Power

System Program

Daniel W. Swallom, Victor M. Goldfarb, Judy S. Gibbs, and Isaac Sadovnik
Textron Systems Corporation, Wilmington, Massachusetts 01887-2941

Vladimir A. Zeigarnik.
IVTAN Association of the Russian Academy of Sciences, Moscow 127412, Russia

Alexander G. Blokh
Nizhny Novgorod Machine Building Plant, Nizhny Novgorod 603052, Russia

Jury P. Babakov
Federal Center of Dual Technologies "Soyuz," Lubertsy 1400561, Russia


 
1. Nomenclature

2.Introduction

3. Hardware Description

4. System Operation

5. Preliminary AcceptanceTest Program

 

6. Analysis of the Preliminary Acceptance Test Results

7. Acceptance Test Program

8. Analysis of the Test Results

9. Conclusions

10. Acknowledgments

 

A pulsed portable 15-MW. magnetohydrodynamic (MHD) power system, called the mir 3U, was designed, built, and tested. The system is powered by three olid propellant rocket engines that deliver the working Suid to the MHD channels. The magnetic field was provided by four conventional, self-excited ellipsoid copper coils. The power unit is self-contained and operates independently of any external support equipment, The objective of this program was to provide a pulsed power system capable of delivering 15 MW of electrical power to the load for a 6- to 10-s duration with a total system mass of less than 1$,000 kg. During the program, five preliminary acceptance tests and eight final acceptance tests were successfully conducted. These tests achieved the performance goals of the program and demonstrated the capability of the Pamir-3U power system in a variety of operating modes.



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Nomenclature


A* - Nozzle throat area P3 - plasma generator number three pressure
CM1- contactor number one   Q - switch
CM2- contactor number two   R - Protection unit resistor
DA - relative erosion of the throat measured with respect to the initial size RB - Ballast resistance
DC1 -  disconnector number one RL - load resistance
DC2 - disconnector number two   RM - Magnet resistance
IIES - initial excitation system current Rl - test hardware article after first refurbishment
IK1 - MHD channel number one current R2 - test hardware article after second refurbishment
IK2 - MHD channel number two current T - plasma generator charge thermal conditioning temperature
IL - load current   TH - load current transducer
IM - magnet current THB - initial excitation system current transducer
Kl - MHD channel number one TK1 - MHD channel number one current transducer
E2 - MHD channel number two TK2 - MHD channel number two current transducer
K3 - MHD channel number three TM - magnet current transducer
L - magnet inductance   VB - ballast resistor voltage
Pav - average plasma generator pressure VK1,K2 - MHD channel one and two voltages
PL - load power   VK3 - MHD channel three voltage
Pmax - maximal plasma generator pressure   VL - load voltage
PU - Protection unit   VM - magnet voltage
P1 - plasma generator number one pressure   VS - thyristor switches
P2 - plasma generator number two pressure      




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Introduction

THE Pamir-3U Magnetohydrodynamic (MHD) power system program was successfully completed in 1995. The Pamir-3U MHD system is a self-contained, portable power system that can be transported to various operational locations and does not require extensive support equipment to generatethe design power. The objectives of this program were to design, fabricate, test, and deliver a 15-MW, MHD power system, not to conduct developmental research.

A preliminary acceptance test program, consisting of five power tests and several preliminary tests, was conducted during August 1994 at Geodesiya Research and Development Institute, Krasnoarmejsk, Russia. During this test program, net power levels as high as 15 MW. were obtained. Operation of the system in various operating modes was demonstrated, and several tests were conducted where the resistance was variedduring the hot-fire test run. The final Pamir-3U MHD power system acceptance test program was conducted at Aerojet Corporation, Sacramento, California, and consisted of eight hot fire tests. The performance levels of the power system were confirmed during these tests. As a result of the experimentsperformed, the operational ability of the MHD power system to operate in a variety of performance modes and under a variety of operating conditions was confirmed.

Fig. 1. Pamir-3U MHD power system.

The Pamir-3U MHD power system, shown in Fig. 1, is a self-excited pulsed MHD generator driven by three solid propellant plasma generators. The power system consists of three MHD channels designed and built by Nizhny Novgorod, which are placed between the electromagnet coils delivered by Nizhny Novgorod; three plasma generators designed and built by Soyuz; switching and protection equipment and a magnetballast resistor designed and built by Nizhny Novgorod; and the initial excitation subsystem (IES) and the control, measuring, monitoring, and recording subsystem (CMMRS), designed and built by IVTAN.' Textron was the system integrator and importer of the Pamir-3U equipment and overall project manager.

The design requirements for the Pamir-3U MHD generator were established at the beginning of the program. The main system design parameters are listed in Table 1. The system design was based on the previously demonstrated, truck transportable, two-channel IVTAN Pamir-2 MHD power system hardware.' Because the specifications of the sponsoring agency required a higher power level, a third MHD channel was necessary.

In the sections that follow, the program highlights from thehardware description to the final acceptance tests are presented. First, the hardware is described. This is followed by a discussion of th6 system operation. Next, the preliminary acceptance test program and the analysis of the results are presented. Following these sections, a discussion of the acceptance test program and the analysis of the results areshown. The paper concludes with a brief conclusion section.


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Hardware Description

The Pamir-3U MHD power system is designed for the conversion of the kinetic and thermal energies of the ionized pro-pellant combustion products flowing through the magnetic field to electrical energy. The main power unit components are shown in Fig. 2. These components are (1) plasma generators with MHD channels and stops; (2) a magnet system; (3) frame, (4), (5) shields; (6) stops; (7) supports; (8) buses; (9) strapping tapes; (10) base plate; and (11) plate. The shields (4) and (5) and the plate (11) are used for protection of the power unit components and the test site from the heating action of the high-temperature flow of combustion products. The material of the shields is a mineral glass-reinforced plastic of 12-mm thickness. The mass of the power unit with the plasma gen erators is 12,700 kg. The overall dimensions of the unit are a length of 4500 mm, a width of 2000 mm, and a height of 2080 mm.

Table 1. PAMIR-3U system requirements
 
Parameter
Value
Maximum net electrical power output 15 MW
Nominal net electrical power output 10-15 MW
Maximal pulse duration at the load 8.5-9.5 s
Maximum mass 18,000 kg
Overall dimension:  
Length 10 m
Width 2.4 m
Height 2.4 m
Electrical load 0.015-0.025Ω
Portability Transportable by standard flat-bed truck trailer

 

The magnet system is installed on. a frame that is attached to the base plate. The MHD channels are placed between four electrical magnets of the magnet system. The longitudinal axes of the MHD channels are inclined at an angle of 19 deg to the horizontal. The power-producing sections of the MHD chan nels are contained within the magnet system. The plasma generators rest on supports and are attached to them by a yoke with a metal band.

The reactive force arising from the operation of the plasma generators is contained by the stops attached to the base plate. For electrical isolation and prevention of current leakage from the electrical circuit, which contains the electrodes of the MHD channel, the front and back ends of the plasma generators, and the propellant combustion products, there are mineral fiber glass-reinforced plastic insulated plates and isolation blocks made from the same material.

The electrical assembly is made of flat copper buses, (8), which are shown in Fig. 2. The bus cross sections are 100 mm X 10 mm and 80 mm X 100 mm. The buses with a direct operating voltage of 2.5 kV are insulated from the power unit components, which are grounded. For the purpose of decreasing the contact resistance, a tin coating with a nickel precoat is applied to the bus contact surfaces. The bus connections are made with standard fasteners.

The plasma generators use a cesium-seeded solid rocket propellant. The BP-10F plasma charge propellant is a doublebased compound (nitrocellulose and nitroglycerin) with a 95/5 aluminum/magnesium alloy (-20% by mass) and cesium nitrate (-10% by mass) added to the propellant mixture. The SPK-10M and SPK-14S plasma charge compositions are similar, but use potassium nitrate instead of cesium nitrate. The actual percentages varied slightly from batch to batch. The thermal power released during Pamir-3U operations is approximately 600 MW. Under these operating conditions, the combustor stagnation temperature was estimated to be -3900 K, and the MHD channel inlet electrical conductivity was estimated to be in the range of 50 - 60 mho/m. More complete details of the burning rate characteristics of each batch are provided in Ref. 1. The plasma generators were similar in design and performance to those used for the Pamir 2 system.

Fig. 2. Pamir-3U system power unit.

The variations of the plasma generator parameters - mass flow rate (18.5 - 26.0 kg/s), operating time (7.4 - 10.5 s), and combustion pressure (34 - 52 atm) - are caused by variations of the burning rate of the propellant, as well as by the dependence of the burning rate on the initial charge temperature, which is normally 5 - 35'C. For operation of the MHD power system in the maximum pulse-duration mode, a special modification of the plasma generator with the initial charge temperature of O'C and an enlarged throat area of 80 cm' was analyzed and approved for use during the acceptance test program. Similarly, a separate analysis was approved for plasma generator charge operation at 40'C for the acceptance tests. This analysis, which results in the approval of only the plasma charge batch being assessed, is based on archival data of pre-vious batches, mechanical and chemical data of the batch of interest, and actual performance data of the batch during operation. If the appropriate criteria are satisfied, operation at initial charge temperatures outside of the 5 - 350 C range is possible.

The Pamir-3U MHD generator is a Faraday-type generator with continuous electrodes. The generator operates at a relatively high pressure to keep the Hall parameter relatively low. The MHD channel consists of three areas: inlet, power-producing zone, and outlet. In the inlet area, the combustion products are accelerated up to a Mach number of 2.4. In the power- producing zone, the MHD energy conversion occurs. The outlet area is intended for the exhaust of the combustion products and the protection of the magnet system from the heat load of the gas flow. The MHD channel is a heat-sink unit. The heat protection is achieved through heat absorption by the design components that are made from heat-absorbing materials: ceramics and mineral fiberglass-reinforced plastic. The channel exit temperature was estimated to be -3000 K.

Fig. 3. Pamir-3U magnet system.

The power-producing zone of the MHD channel consists of two electrode walls with constant divergence and two parallel insulating walls. The inlet area is 159 mm X 159 mm, and the exit area is 159 mm X 258 mm. The length of the MHD power-producing zone is 1008 mm.

The impact of the high-temperature gas flow and the current density distribution results in a variation of the electrical parameters along the channel length. For the purpose of providing the same resistance of the MHD channel components and for decreasing the MHD channel cost, different materials are used for the interior surfaces of the channel walls. At the MHD channel inlet, where the electric intensity is a minimum and the heat flux is a maximum, the lining is made of a thicker insert of erosion resistant graphite. In the pre-electrode area and at the beginning of the power-producing zone of the insulating walls, where the electric intensity is a maximum and the heat flux is less, the lining is made of modules of a high temperature, electrically insulating ceramic. These modules are plates with a variety of geometric shapes.

To decrease the erosion at the boundaries of the adjacent modules, the intermodule clearances are located not in parallel, but at an angle of 45 or 90 deg to the gas flow direction. The gas-side lining on the insulating walls of the working zone, excluding the inlet part of the working zone, on the insulating walls of the outlet area, and on the outlet area of the electrodewalls is made of panels of a high-temperature, electrically in-sulating, mineral fiberglass-reinforced plastic.

The MHD generator electrodes are fabricated from dense, arc-resistive graphite. This material provides acceptable nearelectrode voltage drops and erosion resistance during the normal operating time of 10 s. The electrodes are made as square plates with dimensions of 83 mm X 83 mm. Each of the 24 electrode plates are attached to the electrode wall at one point. The electrodes are connected by a copper current tap attached to the power takeoff bus.

The electrical insulation of the electrodes located on opposite walls along the hot gas surfaces is made in the pre-electrode area and at the beginning of the working area by the application of a high-temperature, electrically insulating mineral fiberglass-reinforced plastic. Electrical insulation is achieved by mounting the electrode and insulating walls on plates of mineral fiberglass-reinforced plastic, and by using a load-bearing shell made from a winding of fiberglass braid.

The Pamir-3U magnet system principal views are shown in Fig. 3. The magnet system consists of four round electromagnets: (1) one left electromagnet; (2), (3) two middle electromagnets; (4) and one right electromagnet; (5), (6) which are separated by glass-reinforced plastic inserts; and (7) tightened by three studs; (8) commutating buses; and (9) protected from the exhaust gases by shields. The right and the left electromagnets each consist of a single electromagnet and cover, and the middle electromagnets, which differ from each other by the commutation of the current buses, consist of two single electromagnets.

For the convenience of the MHD channel installations, the upper inserts (6), shown in Fig. 3, are removable, and the lower inserts are fixed to the middle electromagnets (2 and 3), and the right electromagnet (4). Commutating buses (8) are mounted in the lower part of the magnet system and brought out through the insert windows of the single electromagnet.

The magnet coils are made of copper and are wound in an ellipsoid shape. There are 64 turns per coil. Each coil is insulated through the application of case insulation and its impregnation with an epoxy compound, followed by pressure and temperature polymerization of the insulation. The magnetic field in the magnet central region is 0.247 and 0.204 T/kA for the two side magnets. The magnet temperature at the end of a test run is less than 100'C, and the magnet cooldown time for the next test is less than 24 h.

The IES, which is based on the use of a battery bank, is used to provide the electrical energy necessary for the initial magnetic field over the MHD channel working volume. The system includes a current source, charger, switching, protection and interlock devices, and transducers and measuring instrumentation.

The CMMRS includes the computer for control and recording of the test parameters, the ignition unit used for plasma generator initiation, the control board, the primary electric power supply system, and the connecting cables and fiber-optic lines. The number of channels for measurement and recording is 16, which includes six electrical current measurements, four voltage measurements. four pressure measurements, and two spare channels.

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System Operation

The MHD generators are connected in a series/parallel arrangement. During the initial stage of self-excitation, all three of the MHD generator channels supply power to the electromagnet. During nominal steady-state operating conditions, all three MHD channels operate in the circuit with the electromagnet, but two of them, connected in parallel circuits, also supply power to the load. Figure 4 shows a circuit diagram of the power unit, load circuit, initial excitation system, and the magnet circuit. The detailed description of the Pamir-3U pulsed portable MHD power system and its parameters has been presented in Ref.1.

Fig. 4. Pamir-3U MHD power system electrical circuit.

The MHD power systen operates in the following manner. For the initial state of the MHD power system, all components and subsystems are in the ready mode and available for service. At the very beginning of the operating process, the thyristor switches, VS, are closed (switch Q is closed) by a command from the CMMRS that initiates a discharge from the IES for 1.5 - 1.6 s. Based on the analysis of the operation of the IES, approximately 0.5 s before the magnet current is expected to achieve 3 kA, the CMMRS generates a command to start the plasma generators. This process initiates the MHD channel electrode warm-up, which results in a decrease of the electrode voltage drop. When the magnet current reaches 3 kA, the CMMRS generates a command to the contactor, CM1, and connects the MHD generators to the magnet system, and the MHD power system self-excitation process begins. When thevoltage of the MHD generators exceeds the voltage of thestorage battery, the thyristor switches, VS, disconnect the IES from the magnet system automatically. Then, the switch Q is opened by a command from the CMMRS, and the IES cunent is switched off. For current limitation and in case of excess magnet current over the maximum allowable value, the disconnectors DCI and DC2 switch a ballast resistor into the circuit by a command from the CMMRS. During the self-excitation process, when the magnet current increases up to the specified value, but not more than 16 kA, the CMMRS generates a command to connector CM2 that switches the load into the circuit. After the operation ends, the energy stored in the magnet system is dissipated in the resistances of the magnet system and of the protection unit, PU.

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Preliminary Acceptance Test Program

The preliminary acceptance tests of the Pamir-3U pulsed portable MHD power system were performed in Russia during July and August of 1994 at a test site of the Geodesiya Research Center, Krasnoarmejsk, Russia. The tests were performed for the final adjustment and check-out of all subsystems of the MHD power system in the operational mode. In addition, the tests were used for a demonstration of the MHD power system output parameters and their agreement with the requirements of the technical assignment document.

To obtain test data for the MHD power system operation at loads of 15, 20, and 25 mO in one hot-fire test, two additional connectors were inserted into the load circuit. The generation of the commands for the connectors was provided by the CMMRS. Before the firing run, the initial load resistance of 25 mQ was set. After operation of the contactors, the relevant section of the load was shunted, and the load resistance was sequentially reduced to vatues of 20 and 15 mQ.

The ability to change the ballast resistance by external commutation is also available. The duration of time delays for the control command signal may also be adjusted. These adjustments were performed during the process of the power system preparation for the firing run, and they depend on the operational mode and on the predicted plasma generator parameters.

Two types of the plasma generators were used for acceptance tests. Both types are described in Table 2. Technical data and operating parameters of the MHD channels, plasma generators, and propellant charges used for the preliminary acceptance tests conducted in Russia of the Pamir-3U MHD system are listed in Table 3.

The preliminary acceptance test program included five tests. During the test program, the three test objectives, maximum power mode, nominal power mode, and maximum load pulse duration, were demonstrated along with load switching during a test run. Table 3 lists the preassigned data for each test.
 
 

Table 2. Parameters of plasma generators

Plasma generator type Propellant type Chamber pressure, atm
Pressure dependence on time
Operation time, s
GP-77 BP-10F 29-51 Approximately constant 7-12
  SPK-10M 25-45 -------- 8-13
GP-86 BP-10F 25-51 Rising 4-6
  SPK-14S 20-45 ~1.3-1.5 times the initial value 4.5-6.5

a)BP-10F-plasma-generating propellant with ~10% cesium nitrate; SPK-10M, SPK-14S-plasma-generating propellants with ~10% potassium nitrate. b) Chamber pressure for the range of the propellant grain temperatures of 5-35C.

Table 3. Equipment used and operating conditions for the preliminary acceptance tests

Test no Type Plasma generator Operating time, s MHDb

channel

Ballast resistor, mΩ Load resistor, mΩ
Propellant typea T,C Pav, atm
1 GP-86 OI-304 20 ----- 2.6 1,2,3 20 15
2 GP-86 OI-304 20 28-39 5.6 1R1,2R1,3R1 10c 25,20,15
3 GP-86 OI-304 20 36-50 5.1 4,7,8 20 25,20,15
4 GP-77 OI-72 20 39,41,40 9.0 4R1,7R1,8R1 20 20
5 GP-77 OI-72 35 46,46.8,46 8.3 5,6,9 24 16

Table 4. Summary of the preliminary acceptance test results

Test no. Current pulse duration,s Load resistance, mΩ Average electrical output powerb,MW Average magnet current,kA Average plasma generator pressure, atm Plasma generator duration, s
1 2.35 15 11.0 15.8 ------- 5.5
2 2.43 25 10.8 17.0 33.5 5.6
    20 11.7 16.5    
    15 12.1 16.5    
3 3.15 25 12.8(11.9) 15.8 43.0 5.07
    20 14.6(12.6) 16.6    
    15 15(13.6) 16.6    
4 7.13 20 12.9(11.4) 14.1 41.0 9.01
5 6.36 16 15.1(14.0) 14.0 46.3 8.3

The operating parameters of the MHD power system obtained in the acceptance tests are listed in Table 4. The values of parameters given in the tables, except where noted, are the maximal values obtained in the firing runs. Table 5 provides the values for various operating parameters for preliminary acceptance test no. 3, which was a nominal power mode, loadswitching test. In this test, an operation duration of just over 3 s was achieved, which provided approximately 1 s of operation at each load resistance. An electrical power output of 12 - 15 MW was achieved for the various operating conditions during the test run. The Pamir-3U power system load voltage and current are shown in Fig. 5. Table 6 lists the values for the various operating parameters for preliminary acceptance test no. 5. In this test, the maximum power levels were achieved and proper operation of the system was demonstrated. Figure 6 shows a plot of some of the data from this test. Shown in the figures are the electrical load current and voltage and the magnet current as a function of time. Reference 1 contains a complete presentation of each of the tests conducted during the preliminary acceptance test program.

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Analysis of the Preliminary Acceptance Test Results

The purpose of the preliminary acceptance tests was to pro-vide a verification that the Pamir-3U MHD power system could achieve the performance specifications and operate in the various power-producing modes as designed. These tests were conducted in Russia before the system was shipped to the U.S., so that if any equipment modifications or adjustments were necessary, these changes could be performed before shipment was made. After performing the preliminary acceptance test program, no modifications or adjustments were required before shipment to the U.S.

The MHD power system control and recording of the test parameters during the first three. hot-fire tests were performed with a CMMRS. The reserve CMMRS used light tracing oscilloscopes with an accuracy of 5%. In addition, the most important parameters were recorded by a Hewlett - Packard digital recording system with a random error of measurement of 0.2%. For preliminary acceptance tests no. 4 and 5, the standard CMMRS was used. The test parameters were recorded using a multichannel digital voltmeter. The standard CMMRS measurement accuracy is as follows: the load voltage = 1%; plasma generator pressure = 3; and other electric measurements = 3 .
 
 

Table 5. Pamir-3U variable load preliminary acceptance test results

Parameter,Fig.4 Value for load resistance, RL0 Calculated/measured
25 mΩ 20 mΩ 15 mΩ
Load voltage,VL,V 565 540 475 Ma
Ballast resistance voltage,VB,V 296 318 318 Cb
Magnet voltage,VM,V 964 962 932 C
K3 channel voltage,VK3,V 695 740 775 C
K2 channel voltage,VK2,V 565 540 475 M
K1 channel voltage,VK1,V 565 540 475 M
Load current,IL,kA 21.0 23.4 28.7 M
K1 channel current,IK1,kA 16.4 18.5 19.5 M
K2 channel current, IK2,kA 16.4 18.5 19.5 M
Magnet current,IM,kA 15.8 16.6 16.6 M
Initial excitation current,IIES,kA 2.46 2.46 2.46 M
PG1 pressure,P1,atm 36-38 ------ 49-50 M
PG2 pressure,P2,atm 36-38 ------ 49-50 M
PG3 pressure,P3,atm 36-38 ------ 49-50 M
Load power, PL=V2L/RL,MWe 12.8 14.6 15.0 Ca
Load power, PL=VLIL,MWe 11.9 12.6 13.6 Ca
Excitation time,tE,s 1.18 1.18 1.18 M
Total pulse duration in load,tL,s 3.15 3.15 3.15 M
Total PG burning duration, tPG,s 5.07 5.07 5.07 M
Test conditions:

Charge type=OI-304

Fuel temperature=20 C

Ballast resistance=20 mΩ

       


Fig. 5. Performance results from the variable load preliminary acceptance test.
 

Table 6. Pamir-3U maximum power preliminaryacceptance test results

___________________________________________________________________
 
Parameter, Fig. 4  Value  Calculated/measured
Load resistance, RL

Load voltage, VL

Ballast resistance voltage, VB

Magnet voltage, VM

K3 channel voltage, VK3

K2 channel voltage, VK2

Kl channel voltage, VK1

Load current, IL

Kl channel current, I K1

K2 channel current, I K2

Magnet current, IM

Initial excitation current, IIES

PG1 pressure, P1

PG2 pressure, P2

PG3 pressure, P

Load power, PL = (VL2/RL

Load power, PL = (VLIL

Excitation time, tE

Pulse duration in the load, t

PG burning duration, tPG

Test condition: 

Fuel type = BP-10F 

Charge type = OI-72 

Fuel temperature = 350

Ballast resistance = 24 mΩ 

16 mΩ 

492 V 

336 V 

998 V 

830 V 

504 V 

504 V 

28.5 kA 

20.8 kA 

21.4 kA 

14.0 kA 

2.6 kA 

46 atm 

46.8 atm

46 atm 

15.1 MWe

14.0 MWe

1.395 s

6.36 s

8.3 s

 

Ma

M

Cb

M

M

M

M


 
 
 
 
 
 
 
 

 

 

____________________________________________________________________

The acceptance tests in Russia were conducted using plasma charges whose rated service life had been exceeded. Thus, the prediction of the operating parameters of the plasma charge combustion products was very difficult. Because of this circumstance, the initial test preparation posed some uncertainties. In particular, the selection of the timing of the connection of the load and the ballast resistance to the MHD power system circuit, as well as the ballast resistance value, presented some difficulties.


 

Fig. 6. Performance results from the maximum power preliminary acceptance test.

In test no. 1, the limiting value of magnet current of 20 kA was reached. The magnet current time dependence shows that even before the load and the ballast resistance connection, the magnet current began to stabilize near the level reached. Another anomaly of the first experiment was a premature operation of the dummy load commutators before the planned connection to the channels. Thus, the dummy load resistance value did not change. and was equal to 15 mQ during the entire run.

For test no. 2, the ballast resistance was connected to the magnet circuit from the very beginning. Thus, the self-excitation process was prolonged by artificial means. The dummy load was commutated in this experiment, as well as in the third one, and its value was equal to 25, 20, and 15 mA. The loadcurrent step change corresponds to the recommutation of a dummy load from 25 to 15 mQ. At these load resistances the maximum output power values of 10.8, 11.7, and 12.1 MW" respectively, were reached.

The third test was performed using the standard BP-10F propellant. The facility operated in the standard mode. The maximum output power reached was equal to 12.8/11.9, 14.6/ 12.6, and 15/13.6 MW"corresponding to load resistances 25, 20, and 15 mQ, respectively.

In the fourth test, the dummy load value was not changed. Its nominal value was set equal to 20 mQ. The current pulse duration in the load was 7.25 s. The maximum output powerin the load was equal to 12.9/11.4 MW.. Although the load pulse duration obtained was less than that specified by the design requirements, these test results permitted certain conclusions to be made. For fuel lots with similar burning rates operating at a plasma charge conditioning temperature of O'C with a nozzle throat section area of 80 cm', the extended plasma generator operation time will be about 10 s, and the load pulse duration will be about 8.5 s, which matches the design requirements. This conclusion was later confirmed by the results of the acceptance tests conducted in the U.S.

In the fifth preliminary acceptance test, the plasma generator pressure was less than predicted: 46 atm vs 56 atm. The effect may be explained by the fact that the process of thermally conditioning the charges wasn't properly conducted. The time from the removal of the charges from the thermal conditioning facility until hot-firing exceeded the 3-h time specification. Thus, the effective thermal conditioning temperature may have differed from the 35 C that was specified. In comparing the test no. 5 results with previous data where the thermal conditioning temperature was known, the performance results from this test could be interpreted to indicate that the effective thermal conditioning temperature was closer to 20'C. 0

The self-excitation process was extended and interrupted by the CMMRS. For redundancy, the CMMRS has an algorithm for issuing the command for CM2 operation, not only after reaching the specified current value in magnet system, but also after reaching the specified time of excitation process. Therefore, the magnet current value was equal to 14.4 kA compared to the 16 kA that was calculated. Nevertheless, the maximum output power reached in this experiment was as high as 15.1/ 14 MW.. The pulse duration was equal to 6.36 s.

The results achieved during the Preliminary Acceptance Test Program conducted in Russia demonstrated that the performance objectives of the Pamir-3U MHD power system could be achieved. The facility was operated over the full range of specific load resistances, power-production modes, and facility operating schemes. Satisfactory test results were obtained for the test objectives. A maximum peak power of 15.1 MW. and a maximum average power of 14.4 MW, were obtained.

During the acceptance test program, all elements of the Pamir-3U facility performed as expected. Except for a few minor anomalies that were easily corrected, the entire test operation proceeded without any flaws or test delays caused by the equipment. All Pamir-3U MHD power system and facility components were undamaged during the testing and were ready for the subsequent tests to be performed. All consumable items performed according to their specifications and lifetime requirements. The MHD channels and plasma generator cases are considered consumables, and each component was onlyused for three tests. The overall results of the test programdemonstrated that the Pamir-3U could perform according tospecification, that a test rate of three tests per week can be achieved, and that maintenance and supporting operations can be adequately performed during the nontest periods.

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Acceptance Test Program

The acceptance tests of the Pamir-3U MHD power system were performed at the Aerojet test facilities, Sacramento, California, during February 1995. The tests were performed to demonstrate the capability of the MHD system to achieve the requirements of the technical assignment document and to provide confirmation of the system's operability and reliability.

The GP77 plasma generator is designed for operation as a part of the MHD system. Technical data for the plasma generator are given next: combustion products mass flow = 18.5 to 26.0 kg/s, operation time = 7.4 to 10.5 s, plasma generator pressure = 34 to 52 atm, time from grain ignition to achievement of operating conditions = <0.1 s, plasma-generating propellant mass = 200 kg, and charge temperature operating range = 0 to 40'C. Technical data and operating parameters of the MHD generator channels, plasma generators, and propellant charges used for the Pamir-3U MHD facility acceptance tests in the U.S. are listed in Table 7. In addition, the firing conditions of the plasma generators are also included in the table.

The acceptance test program included eight tests. The ninth and tenth tests were considered as a reserve. During this time, the three test objectives, 1) maximum power mode, 2) nominal power mode, and 3) maximum load pulse duration mode, were demonstrated. Table 7 lists preassigned data for each test.

A summary of the results from each of the eight tests that were performed is provided in Table 8. Table 9 provides the values for various operating parameters for a long-duration test. In this test, an operation duration of approximately 9.5 s was achieved with an output power level greater than 10 MW,. For this test, the electrical power delivered to the load was nearly constant over the entire duration of the test. This result along with the plasma generator pressures and the MHD channel, load, and magnet currents and voltages are shown in Fig. 7.

Table 10 lists the values for the operating parameters for a maximum power test. In this test, the maximum power levels were achieved, and proper operation of the system was demonstrated. Figure 8 shows the plots of the test data for this test. The plots show, from top to bottom, the magnet and load voltages; the center channel (magnet), side channels, and load currents; the plasma generator pressures; and the power generated as function of time. Reference 1 contains a discussion of each of the tests conducted during the program.

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Analysis of the Test Results

The maximum power mode was demonstrated in test nos. 1, 2, 4, and 8. The BP-10F plasma charges from the 6-94-L batch and new MHD channel hardware and plasma generator cases were used in these tests. In test no. 1, an average output power of 12.8 MW"a peak output power of 13.6 MW"and a load current pulse duration of 6.72 s were obtained with an initial load resistance of 20 mA.

To achieve a greater output power in test no. 2, the magnetic field was increased by decreasing the ballast resistance and increasing the magnet switching current, which is the magnet current at the time that the load and the ballast resistance were switched into the circuit.

As a result, an average generator output power of 13.4 MW" a maximum generator output power of 14.0 MW., and a load current pulse duration of 6.48 s were achieved in test no. 2 at the same load resistance that was used for test no. 1. The analysis of the current and voltage curves showed that boundary-layer separation appeared to have occurred in generator channel 3, which supplies the magnet current, when the magnet current reached 16.2 kA. This phenomenon was exhibitedby a magnet voltage decrease. This behavior did not occur ingenerator channels 1 and 2, which were supplying the load.Thus, output power in the load was rather stable. The boundary-layer separation phenomenon in generator channel 3 primarily impacts the current dynamics in the magnet system, and it can be eliminated by a variation of the ballast resistance.

Table7. Pamir-3U equipment used and operating conditions


          Plasma generator            
Test GP-77

Gase no.

A*, cm2 OI-72

Batch

T

 C

Pav,atm Pmax,atm Oper.time,s DA,% MHD

channel

Ballast resist, mΩ Load resist, mΩ Swiching current,kA
1 9401 73.48 6-94-L 35 44.7 47.1 8.5 3.0 1 25 20 16
  9402 73.48 6-94-L 35 45.3 48.8 8.5 2.3 2      
  9403 73.48 6-94-L 35 46.3 49.0 8.5 2.6 3      
2 9404 73.48 6-94-L 35 45.1 48.4 8.5 3.0 4 16 20 18
  9405 73.48 6-94-L 35 46.3 8.5 8.5 3.5 5      
  9406 73.48 6-94-L 35 47.5 49.4 8.4 1.7 6      
3 9403R1 73.48 5-94-L 35 44.6 46.8 8.6 2.8 4R1 18 15 14.5
  9402R1 73.48 5-94-L 35 46.6 48.6 8.5 2.8 5R1      
  9401R1 75.69 5-94-L 35 44.2 46.5 8.6 1.0 6R1      
4 9409 73ю48 6-94-L 42 45.6 48.9 8.3 2.6 7 8 15 18
  9407 73.48 6-94-L 42 48.1 50.8 8.3 4.7 8      
  9408 73.48 6-94-L 42 49.3 51.8 8.3 2.7 9      
5 9404R1 80.17 5-94-L 0 31.7 33.0 10.4 0.99 4R2 18 15 12
  9405R1 80.17 5-94-L 0 33.8 35.0 10.4 0.92 5R2      
  9406R1 80.17 5-94-L 0 34.3 35.7 10.4 1.1 6R2      
6 9403R2 75.69 5-94-L 20 37.8 40.3 9.4 1.0 1R1 20 25 14.5
  9401R2 74.7 5-94-L 20 40.1 41.9 9.3 1.7 2R1      
  9402R2 75.38 5-94-L 20 40.0 42.3 9.4 1.7 3R1      
7 9408R1 75.43 5-94-L 0 34.0 34.6 10.2 0.97 7R1 12 15 +
  9407R1 77.58 5-94-L 0 34.0 37.9 10.1 0.79 8R1      
  9409R1 75.39 5-94-L 0 34.9 37.5 10.1 1.38 9R1      
8 9411 73.48 6-94-L 42 46.9 51.3 8.1 3.1 10 14 15 14.5
  9410 73.48 6-94-L 42 46.7 50.2 8.1 2.3 11      
  9412 73.48 6-94-L 42 46.3 49.6 8.1 2.0 12      

Table 8. Summary of the U.S.acceptance test resultsa

Test no. Current pulse length,s Total load energy, MJ Average output power, MWe Maximum output power, MWe Average magnet current, kA Average plasma generator pressure, atm Plasma generator duration, s
1 6.72 86.0 12.8 13.6 14.9 45.8 8.28
2 6.48 86.8 13.4 14.0 16.1 46.9 8.26
3 6.70 86.8 13.0 13.3 14.7 45.4 8.32
4 6.20 85.6 13.8 14.9 16.7 48.7 7.92
5 8.92 92.3 10.3 10.6 12.6 34.1 10.32
6 7.48 77.8 10.4 10.9 14.1 40.1 9.27
7 10.4 87.8 10.3b 11.0 13.9 34.3 10.20
8 6.43 89.9 14.0 14.9 15.5 46.6 7.97

Table 9. Pamir-3U maximum duration acceptance test results

Parametr,Fig.4 Peak Average Range Calculated/ measured
Load resistance,RL,m 17.9 16.7 15.4-17.9 C/M
Magnet resistance,RM,m 65.3 60.6 56-65.3 C
Load voltage, VL,V 433 416 363-433 M
Ballast resistance voltage,VB,V 235 226 194-235 C
Magnet voltage, VM,V 1257 812 0-1257/784-840 M
K3 channel voltage, VK3,V 626 622 0-609/617-626 M
K2 channel voltage,VK2,V 648 426 0-648/375-443 M
K1 channel voltage,VK1,V 648 426 0-648/375-443 M
Load,current,IL,kA 25.0 24.0 22.6-25.0 M
K1 channel current,IK1,kA 19.4 18.5 17.4-19.4 M
K2 channel current,IK2,kA 19.2 18.5 17.4-19.2 M
Magnet current,IM,kA 13.1 12.6 0-13.1 M
PG1 pressure,P1,atm 32.9 31.7 26.6-32.9 M
PG2 pressure,P2,atm 35.2 33.8 26.9-35.2 M
PG3 pressure,P3,atm 36.5 34.3 28.6-36.5 M
Load Power,PL,MW 10.4 10.0 8.7-10.4 M
Test conditions:

Fuel type=BP-10F

Charge type=OI-72,5-94-L

Final IIES current=2.7kA

Fuel temperature=0 C

Ballast resistance =19m

       

 

 

Fig. 7. Performance results from the maximum duration acceptance test.

The analysis of the first two test results showed that a further increase in output power would only be possible by increasing the pressure in the plasma generators or by an increase in the combustion product mass flow rate. Under real test conditions, this goal could be achieved only by an increase in the plasma-charge thermal conditioning temperature.

Thus, the thermal conditioning temperature for test no. 4was increased to +42'C. Because this temperature is above the upper limit of +35'C given in the technical speci6cation developed by the manufacturer (Soyuz), special approval was requested and received for a thermal conditioning temperature in test no. 4 of 40 ~ 2'C. Because the thermal conditioning facility was capable of precise temperature control well within this limit, the temperature could be set to the maximum without exceeding the temperature limit. In this test at a load resistance value of 15 mQ, an average channel output power of 13.8 MW., a peak channel output power of 14.9 MW"and a load current pulse duration of 6.2 s were obtained.

Analysis of the current and voltage curves revealed the beginning of boundary-layer separation phenomenon in generator channel 3 at a magnet current of 16.9 kA. A load power decrease within the time interval from 3.2 to 5 s appears to be explained by the onset of this phenomenon in generator channels 1 and 2, which are providing current to the load. This appears to be the case during test no. 4 because these two generator channels were loaded by a lower resistance than in previous tests and their currents were correspondingly more: 15 mQ compared with 20 mQ in test no. 2, and 23.8 kA compared with 22.0 kA, respectively.

On the basis of these results, the last test in the maximum power mode (test no. 8) was carried out at a lower magnetic field to avoid the boundary-layer separation. In this test, an average output power of 14.0 MW., a maximum output power of 14.9 MW"and a load current pulse duration of 6.43 s were achieved under the same test conditions as those in the test no. 4: a thermal conditioning temperature of +42'C and a load resistance of 15 mA. Again, special approval was received in advance from Soyuz for the higher thermal conditioning temperature of 40 ~ 2'C. However, the increase in the average output power cannot be expected to be substantial. This is probably the result of the fact that bouadary4ayer separation occurred in generator channels 1 and 2 during test no. 4, but had no drastic effects. In general, the effect of boundary-layer separation on the Pamir-3U output performance requires further study.

The nominal power mode was demonstrated in tests no. 3 and 6 using the refurbished MHD channels and plasma generator cases and the 5-94-L charge batch. The thermal conditioning temperature for the plasma generators for test no. 3 was +35 C. Under these conditions, an average generator out put power of 13.0 MW"a peak output power of 13.3 MW., and a load current pulse duration of 6.7 s were obtained with a load resistance of 15 mA.
 
 

Table 10. Pamir-3U maximum power acceptance test results

Parameter, Fig.4 Peak Average Range Calculated/measured
Load resistance,RL,m 18 16.5 15-18 C
Magnet resistance,RM,m 65.3 60.6 56-65.3 C
Load voltage, VL,V 499 472 448-499 M
Ballast resistance voltage,VB,V 231 217 203-231 C
Magnet voltage,VM,V 1700 1015 0-1700/956-1064 M
K3 channel voltage,VK3,V 812 764 0-812/722-806 C
K2 channel voltage,VK2,V 885 481 0-885/457-507 M
K1 channel voltage, VK1,kA 885 481 0-885/457-507 M
Load, current, IL,kA 30.0 29.1 27.2-29.97 M
K1 channel current,IK1,kA 23.7 22.8 21.3-23.7 M
K2 channel current,IK2,kA 23.2 21.8 20.8-23.2 M
Magnet current,IM,kA 16.5 15.5 14.48-16.5 M
PG1 pressure,P1,atm 51.3 46.9 42.5-51.3 M
PG2 pressure,P2,atm 50.2 46.7 41.7-50.2 M
PG3 pressure,P3,atm 49.6 46.3 41.7-49.6 M
Load power,PL,MW 14.9 14.0 12.5-14.91 C
Test conditions:        
Fuel type = BP-10F

Charge type= OI-72,6-94-L

Final IIES current=2.7kA

Fuel temperature = +42 C

Ballast resistance = 14 m

       

 

Fig. 8. Performance results from the maximum power acceptance test.

The main parameters for test no. 6 were as follows: thermal conditioning temperature of +20'C, load resistance of 20 mQ, average generator output power of 10.4 MW"peak generator output power of 10.9 MW"and load current pulse duration of 7.48 s. Estimates showed that the average power would be about 12.5 MW. at a thermal conditioning temperature of +20'C, when using charges from 'the 6-94-L batch. Thus, the overall range of the average power in the nominal operation mode appeared to be 10 - 13 MW, for the charge batches tested.

The maximum duration mode was demonstrated in two tests: tests no. 5 and 7 using a thermal conditioning of 0 C and plasma charges from batch 5-94-L in both tests. For test no. 5, the nozzle throat area and the inserts in the generator channel acceleration zone were bored out to 80 cm'. An average channel output power of 10.3 MW"a peak generator output power of 10.6 MW"and a load current pulse duration of 8.96 s were obtained with a load resistance of 15 mQ. In this test, a maximum energy release in the load of 92 MJ was achieved. The energy was based on the total integrated net power produced by the system during the time that the electrical load resistance was connected to the MHD power system.

In test no. 7, another approach to the maximum duration mode, which is the use of the plasma generator without boring the nozzle throat area, was undertaken. In this case, the load and ballast resistances were switched into the electrical circuit from the very beginning of the run, rather than at the end of the self-excitation stage. As a result, a load current pulse duration of 10.4 s and a peak output power 11 MW. were achieved. The average output power within the quasi-steady state portion (6.75 s) of the load current was equal to 10.3 MW,.

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Conclusions

The results achieved during the acceptance test program demonstrated that the performance objectives of the Pamir-3U MHD power system could be achieved. The facility was operated over the full range of specified load resistances, power-production modes, and facility operating schemes. Satisfactory test results were obtained for these test objectives.

A maximum peak power of 14.9 MW. and a maximum average power of 14.0 MW, were obtained. While these power levels were slightly below the 15-MW. goal, these levels were achieved with plasma charges that were slightly below average in performance. Thus, any subsequent tests performed with plasma charges with average or above average performance would be expected to easily achieve the 15-MW. net output power objective.'

The general relationship between temperature conditioning of the plasma charges, burn rate, stagnation pressure, and output produced by the Pamir-3U system was confirmed. Because of the limited amount of test resources available, specific comparisons at identical operating points with different combustion pressures (thermal conditioning temperatures) were not performed. However, the general trend of increased power output for increased operating pressures was consistent with the results that have been obtained previously.

During the acceptance test program, all elements of the Pamir-3U facility performed as expected. Except for a few minor anomalies, the entire test operation proceeded without any flaws or test delays caused by the equipment. All Pamir-3U MHD power system and facility components were undamaged during the testing and are ready for subsequent tests. All consumable items performed according to their specifications and lifetime requirements.

The test program demonstrated that the Pamir-3U performed according to specification, that a test rate of three hot-fire tests per week can be achieved, and that maintenance and supporting operations can be adequately performed during the nontest periods. No damage was incurred by any of the system and subsystem components during the test program. The hardware is ready for subsequent transportable power requirements to support testing at a variety of locations.

Acknowledgments

This work was performed for the U.S. Air Force, Air Force Materiel Command, Phillips Laboratory, under Contract F29601-93-C-0033. The work was performed by the "IVTAN Association" of the Russian Academy of Sciences (Russia)and Textron Systems Corporation (USA). Major subcontractors that participated in this effort were the Nizhny Novgorod Machine Building Plant (Russia), the Federal Center of Dual Technologies "Soyuz" (Russia) and the Aerojet Corporation USA). The authors would like to thank Naufal L. Aitov, Vladimir I. Okunev, Victor A. Novikov, and Victor Yu. Rikman of the IVTAN Association of the Russian Academy of Sciences; Alexei V. Pisakin, Peter N. Egorushkin, and Boris G.Tkachenko of the Nizhny Novgorod Machine Building Plant;Reginald K. Kuzmin of the Federal Center of Dual Technologies "Soyuz"; and Alvin M. Olson, Roger E. Anderson, Mi-chael A. Fedun, and Garvin R. Hill of the Aerojet Corporation for their contributions to the successful completion of this program.

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    Department of Pulsed MHD Power Systems & Geophysics

 

 2001