Research in the performance improvement of gas-turbine or internal combustion engines commenced immediately after they were created. Until recently, key factors in this field included engine cycle parameters, turbine inlet temperature and total compression ratio. However, further improvement of engine performance can only be achieved by new design solutions, advanced materials, effective and coordinated operation of individual components within an engine’s system, maximum degree of airframe/engine integration, and smart computer-based engine control systems.
However, the increase in the number of techniques employed to improve engine working processes makes engine operational development virtually impossible by conventional methods. Therefore, CAD (computer-aided design[66]) technology is vitally important to research processes for engine components and their optimization. Most improvements in the efficiency of engines and their components can be achieved in the optimization of designs with multiple parameters, the area where developer’s intuition and experience are not sufficient and, in our opinion, where new technological solutions can be found.
CAD techniques, which fully account for gas-dynamics interaction, heat and mass exchange, strength, reliability, production technology, control and cost issues, are evidently effective for the optimization of aircraft engine’s parameters. Yet the research in and analysis of the best technological solutions using traditional techniques for engine component optimization face many difficulties, including:
– optimization of designs witch multiple parameters (tens and even hundreds of variables);
– topological complexity of goal functions and constraints;
– considerable amount of CPU time required;
– multiple criteria of tasks etc.
Currently, few results are known on the practical optimization of aero engine performance.
In this connection, the techno-Pulsar Research and Engineering Enterprise has developed a new, highly effective optimization technology to increase gas-dynamic efficiency (specific fuel consumption, thrust, specific weight, acceleration time, etc.) and cost efficiency (production, operating and modernization costs) for various engine designs. Our technology is based on unique numerical optimization methods which feature the following advantages compared to existing techniques:
– comparatively small number of direct calls to the mathematical simulator of object under research to achieve the result;
– sufficiently high probability of determining global extreme in multi-extreme tasks;
– capability to solve single-criterion and multi-criteria deterministic and stochastic tasks with multiple variables and constraints;
– simple use of all mathematical simulators.
Our technology, designed to form various alternative optimal solutions and provide new methods for improving engine efficiency, fulfills the following tasks:
– optimal design (new engine’s development or existing engine’s modernization);
– search for optimal control laws for controllable engine elements, including the substantiation of their rational quantity and composition;
– optimal design of controllable objects (a combination of optimized design and optimized control tasks).
For example, our technology used to modernize an engine compressor by only reshaping all blade rims and air flow section (140 design parameters were optimized) produced a 3,5-percent increase of compressor efficiency in a wide range of engine ratings.
Our experience indicates that under this technology the volume of computations and the time of overall effort to solve multivariable tasks can be reduced by two to three orders of magnitude. In addition, if a mathematical simulator can not be developed, our methods can be used for optimizing a full-scale object on a test stand.
For example, for the experimental adjustment of microprocessor-based internal combustion engine control systems, fast-running optimization procedures are required to find the requisite solution within a limited number of experiments. The efficiency of our technology was assessed when it was put to the task of fast search for the optimal adjustment of an experimental VAZ car’s engine control system. The task involved the search for optimal gas mixture control, ignition advance angle and exhaust gas recycling. It was necessary to find optimal parameters for each power and speed engine rating which would ensure minimum fuel consumption at specified exhaust gas toxicity levels. Each optimization task (for a given engine rating) was characterized by three variables and three limitations and was solved by 14 experiments, while the traditional method would have required at least 100 experiments.
The resultant analysis demonstrated that our optimization technology can be effectively used for fast experimental adjustment of microprocessor-based engine control systems. It also provides for the stable solution of tasks involving optimal adjustment of these systems, requires a small number of calls for an object under research to determine optimal parameters, and can be used to find a solution in case of errors in the course of experimental adjustment.
Modern CAD technology application in engine-building requires the integration of theoretical/computational research with industrial production.
This research for the most part uses the so-called deterministic approach which assumes that its results will be most precisely implemented in production which, however, cannot be provided by the most advanced production technology. At the R@D phases, a required production technology level is only considered in the mathematical model of an object under research, at best. At the same time, during the search for the optimum solution, a real range of design parameters is not considered. As a result, the probability of accurate project implementation at the production phase is low. Therefore, search for the most effective technical solutions without full consideration of the production technology level will not assure parameters specified at the engine development phase. This design solution does not fully correspond to the optimal one, as it does not consider the probability of the project’s implementation. The problem can be successfully solved via the stochastic optimization of the gas-turbine engine and its components, making it possible to achieve a probability of the project’s implementation of almost 1.0, with only an insignificant decrease in efficiency compared to the deterministic solution.
The Techno-Pulsar’s optimization technology can be used to:
– develop engines accounting or a concrete production technology level;
– determine the probability of achieving specified parameters in case of a technology level decrease at some production lines;
– substantiate the requisite production technology level and product production technology requirements for a new product at the R&D phase;
– search for «choke[67] points» affecting engine parameter assurance both at the R&D and production phases;
– introduce certain engine operating features at the R&D phase (for example, only a slight decrease in compressor’s operational performance in the course of its service life in dusty areas by corresponding changes in the geometry of compressor blade).
The list of advantages provided by our technology can be continued. It is noteworthy that the deterministic optimization approach traditionally uses in engine design is only a specific case of stochastic object optimization.
Our technology was used to solve over 500 practical tasks to optimize aircraft gas turbine engines and their components with about 200 articles sent for production development and the update of existing type (a prototype improvement task). The results were implemented at the Lulka-Suturn JSC, Samara-based Kuznetsov Research and Engineering Complex, Snecma, etc. our main task was to increase the efficiency of engine components and reduce fuel consumption. Over 80 percent of results led to efficiency increases of more that one percent. These results were received for the same design configurations and the same number of limitations as those for the prototypes. In fact, our technology provides an opportunity to discover and use to the maximum extent potentialities of existing gas turbine engines which cannot be revealed by the conventional methods.
Our technology was widely proven and recognized by leading Russian and foreign specialists in the aviation engine industry. In part, the technology was demonstrated at the INFO’89, Engines’92, Engines’96 and MAKS’97 international exhibitions.
The technology and its results were discussed at the ISAIF- 1, ISALF-3 and ASME TURBO-EXPO’92, ’93, ’94, ’97, ’98, symposia which led over 20 research reports that were published in the USA, Great Britain, France and China.
We believe that our optimization technology will help develop a new concept for the increase of engine efficiency. It will considerably reduce engine efficiency, enhance the general proficiency level of experts and help cope with difficult and multifaceted problems which will challenge the aviation industry in the future.
EXSERCISES
1. Write 10 questions to the text from the unit.
2. Write out of the text the sentences with the verbs in the Passive voice.
3. Translate any part of the text (1500 signs) in writing.
4. Retell text.
5. Speak on «Usage of the Techno-Pulsar’s optimization technology».
UNIT X. RADAR
Airborne Radar
That Tracks Missiles
Two giants in the airborne radar field have joined to develop new radar that can detect and track, not only ground targets and aircraft, but also cruise missiles. It’s a unique system designed by a unique partnership.
By James W. Ramsey
Existing airborne radars can detect and track moving ground vehicles and aircraft. Now the U.S. Air Force is developing the first airborne surveillance radar capable of detecting and tracking low-flying cruise missiles. And despite budget uncertainties, the development program is on schedule.
Two leading U.S. radar providers, Northrop Grumman and Raytheon, are teamed in a unique partnership to develop the new sensor in the Multi-Platform Radar Technology Insertion Program (MP-RTIP). Northrop Grumman is the prime contractor, but it splits development and initial production work on the new radar system 50-50 with Raytheon. This arrangement to develop the radar for the new E-10A wide-area surveillance (WAS) aircraft and the Northrop Grumman Global Hawk unmanned air vehicle (UAV) seems to be working. «The program is progressing well», declares Col. Joseph Smyth, commander of the E-10/MP-RTIP systems group at the USAF’s Electronic Systems Center.
The radar program successfully completed its final design review in June 2004, and a laboratory-based prototype system was tested at Raytheon’s El Segundo, Calif., facility last September.
Following the award of a six-year, $888-million contract for the program’s system development and demonstration (SDD) phase, the companies have been procuring components and preparing to build the first flyable system, scheduled to be tested on a Global Hawk surrogate aircraft in October 2006. At the same time a larger version of the modular scalable radar will be produced for test flight on a Boeing 767-400ER test bed, the anticipated aircraft platform of choice for the E-10A program.
Comparison to JSTARS
Both contractors and the service claim that the new radar will enhance the USAF’s ability to track and identify stationary and moving vehicles, as well as hard-to-detect cruise missiles. It also will perform battlefield command and control functions.
Unlike currently fielded airborne systems, such as the E-8C Joint Surveillance Attack Radar System (JSTARS), the MP-RTIP radar will be able to collect ground moving target indicator (GMTI) imagery and synthetic aperture radar (SAR) still images nearly simultaneously. The radar also will be able to detect, track and identify more targets faster and with higher resolution than ever before, according to Dave Mazur, MP-RTIP program manager at Northrop Grumman’s Integrated Systems sector in El Segundo.
«The key difference in this radar over the JSTARS radar is the fact that it includes missile defense. That capability doesn’t exist today in an airborne platform», – says Mazur. «And this radar, in comparison, offers increased range, accuracy and resolution, and faster revisit[68] time».
The Air Force concurs. «The MP-RTIP being designed for the E-10A will provide five to 10 times the air-to-ground surveillance capability of JSTARS», Col. Smyth adds. What assures this capability is the new radar’s larger aperture, the increased available power to the system, and its active electronically scanned array (AESA) antenna, which automatically scans in both azimuth and elevation, Mazur explains. «That means we can almost instantly revisit several areas at one time. Each pulse can be doing a different technique».
«Not only can you run [software] modes in sequence, you can interleave them», – adds Tom Bradley, Raytheon’s MP-RTIP program manager. He explains that, with one asset tasked to carry out significantly different missions, the platform will be able to collect and integrate «all types of intelligence on ground moving targets, imagery and low-flying threats», and provide the user with a comprehensive threat picture.
Both contractors bring considerable AESA antenna experience to the table. Northrop Grumman has developed radar systems for the new F-22 and F-35 fighters, while Raytheon is providing similar radars for the F-15 and F/A-18E/Fs. (The first operational unit equipped with Raytheon’s AESA radars is an F-15 squadron based in Alaska). Raytheon also is upgrading the active array radar for Northrop Grumman’s B-2 bomber program.
While not planned to replace the E-3A Airborne Warning and Control System (AWACS) radar, MP-RTIP can track conventional aircraft as well as cruise missiles. «The frequency we operate at–X–band–is different from [that used by] AWACS», says Mazur. (The Air Force’s AWACS uses S-band radar.) «This allows us to have a very narrow beam, which allows [the radar] to be very accurate. We need that to track cruise missiles. This is a feature we can exploit to augment the AWACS capability».
An AESA includes thousands of transmit and receive modules that are assembled onto «subarrays»[69] inserted into the antenna. The antenna then sends the radio frequency (RF) signals to a receiver, and the radar support electronics processes them.
While the antenna remains stationary, the beam is steered electronically. And the radar’s electronic scanning capability moves the beam much more rapidly than previous systems, promoting improved radar searching and multiple tracking capabilities. By removing gimbals and other moving parts associated with manually scanned antennas, AESA offers increased reliability, Raytheon and Northrop claim.
Radar Size
The MP-RTIP radar being developed for the E-10A is a side-looking radar, whose antenna aperture units and associated avionics are mounted in a pod underneath the fuselage, forward of the wing root. While the antenna doesn’t move in azimuth or elevation, it does rotate on gimbals 180 degrees to look out the other side of the aircraft.
The radar antenna for the Global Hawk measures 1,5 feet (0,46 m) tall by 5 feet (1,5 m) long. On the E-10A the antenna is considerably larger: 4 feet (1,2 m) tall by 20 feet (6,1 m) long. (The JSTARS pod measures 2 by 24 feet [0,6 by 7,3 m]).
The MP-RTIP requires a wide body aircraft such as the B767, primarily because of the radar’s height. «You need something with a big enough landing gear, to account for a hard landing with all tires blown, and you are riding on the rims, and your shocks are fully compressed», – Mazur explains. «Our must have adequate clearance, so you don’t go in there and scrape off the radar»
Most of the electronic equipment supporting the radar-including receivers exciters, power conditioning units and processors – are mounted inside the E-lOA’s cargo bay. A separate (helicopter) jet engine, mounted in the cargo bay in a fireproof enclosure, powers the radar.
In terms of radar hardware, Global Hawk bears a «two box» system, with the antenna mounted below the aircraft and the signal processor inside an avionics bay. The radar mode software resides in the signal processor, which is responsible for controlling the radar, running it and processing the data.
Scalable Radar
The USAF’s original intent was to make MP-RTIP a radar upgrade for JSTARS – the service’s airborne ground surveillance, targeting and battle management system–which has been used effectively in the Iraq war. But MP-RTIP evolved into an advanced system that a wide body platform could best accommodate. (JSTARS uses the narrow body Boeing 707.)
MP-RTIP was designed to be scalable radar, using the same basic architecture and common software, but with a smaller aperture to accommodate later model Global Hawks. (A scenario is envisioned using both the Global Hawk and E-10A together for battlefield surveillance and air-to-air detection.)
Teaming Arrangement
Northrop Grumman Integrated Systems is the prime contractor for MP-RTIP, although its program management, modeling and simulation, and Global Hawk flight test activities account for only about 10 percent of the program. The other 90 percent involves the radar’s design, development and testing. These activities are split evenly between Raytheon’s Space, and Airborne Systems unit in El Segundo and Northrop Grumman’s Electronics Systems sector in Baltimore and Norwalk, Conn. All work on MP-RTIP falls under Mazur’s realm of responsibility.
«Northrop Grumman and Raytheon are fierce competitors in the radar world, so bringing these two teams together to work on this program smoothly has been a challenge. But we’ve been very successful at it», – boasts Mazur. (In fact, the Air Force granted the two contractors 100 percent of incentive award fees for successful teamwork in the contract’s first phase.)
As for hardware, Raytheon is providing the MP-RTIP’s «front-end» RF aperture unit (RFAU) antenna assemblies on the E-10A, while Northrop Grumman Electronic Systems provides the radar back-end. «We build the aperture assemblies into an antenna and provide receivers/exciters, cabinets and a radar signal processor», – says Russ Conklin, MP-RTIP program manager for Northrop Grumman Electronic Systems. Northrop Grumman is responsible for the E-10A’s radar integration and testing at its systems integration laboratory in a former Norden facility in Connecticut.
On Global Hawk the contractor’s roles are reversed. Northrop Grumman builds the antenna elements and Raytheon, the back-end. Raytheon is responsible for integration and testing at its systems integration lab in El Segundo. There the software modes are added prior to flight test – and for testing on the Global Hawk.
«We at Raytheon build the currently used Global Hawk radar sensor, which has SAR and MTI [moving target indicator] modes, and we have a lot of experience putting it out in the field», – says Raytheon’s Bradley. «Northrop Grumman is doing Joint STARS and brings that system experience forward».
«Global Hawk is reconnaissance, and Joint STARS is really surveillance», – he adds. «Now you’re creating a platform that can do both. And by adding some air-to-air mode support, it also is going to be doing cruise missile defense».
The basic MP-RTIP software on the E-10A and Global Hawk are common. Both Raytheon and Northrop Grumman, together, are writing the radar operating services (ROS), built-in test (BIT) and calibration. One team member or the other is writing independently each of the three major radar modes: GMTI, SAR and airborne moving target indicator (AMTI).
Fitting MP-RTIP on Global Hawk is a plus for the Е-10А program, Mazur says, because a number of the MP-RTIP modes are common between the two platforms. «We can do a lot of the integration and testing and validation before we get to the E-10A platform, so it helps us save test time on the E-10A portion. It is more expensive to run a B767 than to fly a Global Hawk».
Raytheon also brings it’s transmit/receive (TR) module manufacturing capability to the program. «We have a dedicated factory down in Texas [attained when Raytheon acquired Texas Instruments in Dallas]», Bradley points out.
Both Raytheon and Northrop Grumman Electronic Systems work closely with Mercury Computer Systems, a commercial off-the-shelf (COTS) vendor in Chelmsford, Mass, that provides processors for radar signal processing and the receiver/exciter hardware.
Program Status
The MP-RTIP program was officially launched with a phase 1, three-year $415-million contract awarded to the team in December 2000. With a positive cost performance, the team «under-ran» the contract and continued to work on it into February of 2005, according to Mazur. In July 2003 the radar’s integrated targeting capabilities were demonstrated in a series of virtual war games hosted on Northrop Grumman’s cyber warfare integration network (CWIN), a nationwide virtual battlefield environment.
«We demonstrated that by using three coordinated MP-RTIP wide-area surveillance aircraft dispersed over a large geographic region, a commander could simultaneously defend against cruise missiles fired from multiple locations and conduct a precision strike against a column of enemy armored vehicles», – says Mazur.
In late 2004, after the final design review authorized the Northrop Grumman team to begin building and testing the new radar, the team integrated and tested a laboratory-based prototype of the MP-RTIP radar at Raytheon’s California facility. As part of a risk reduction program, off-the-shelf equipment was used to build Global Hawk radar for initial testing to resolve technical issues well in advance of the production and integration of actual flight hardware.
Originally envisioned as«single string» radar, with only one RF aperture unit and the avionics to support it, MP-RTIP «eventually morphed into a full set of four RFAUs, which is basically what the Global Hawk radar will look like», says Mazur. «In demonstrating this software, we did two air-to-air modes with this prototype radar, using a target generator [in a Raytheon facility] a couple of miles away. That [radar] is going to be taken now and modified into one of the three radars to be delivered for Global Hawk. This one will not fly, but stay in the lab».
Proteus Test
Following build-up of the equipment and software modes for the Global Hawk system, flight tests of the radar are scheduled to start in October 2006. The Northrop-Raytheon team will use the Proteus surrogate, a manned high-altitude, long-endurance aircraft built by Scaled Composites. The radar will be pod-mounted and monitored by a flight engineer on flights near Edwards AFB, Calif. The schedule calls for one flight a week, after which the radar will be integrated into a Global Hawk vehicle for further testing.
Proteus flies at the same altitude as Global Hawk and is more efficient to use than the manned platform for initial tests, Mazur explains. The two-seat Proteus will «drastically reduce the amount of time we have to test on Global Hawk». Also, having a man in the loop allows for more efficient testing, he adds.
With flight test of the MP-RTIP radar less than two years away, «we are well into actual development of the Global Hawk radar, buying material, including processors and computers, having released all the drawings, and putting together plans that say how to actually build the radar», – says Mazur. Software design is complete, but coding and testing continues.
On the E-10A radar, the team is in the initial stage of buying material. It expects to flight test the MP-RTIP on the E-10A in two to three years after the Global Hawk tests begin next year.
EXSERCISES
1. Write 10 questions to the text from the unit.
2. Write out of the text the sentences with the verbs in the Passive voice.
3. Translate any part of the text (1500 signs) in writing.
4. Retell text.
5. 5. Speak on «JSTARS».
