Mobility at stake: the victory of the "hybrids" is still in doubt
BMP "Puma" of the German army needs a power unit, which could offer more power, located in a limited volume. The MTU 10V 890 meets this requirement, providing exceptional power density.
Excellent mobility in the most difficult conditions is the primary characteristic of all military vehicles. However, to achieve this for armored vehicles is much more difficult, but it is extremely important that they successfully carry out their tasks.
Mobility is very important for armored vehicles, but at the same time it competes with other important characteristics, such as, for example, ensuring the survivability of the vehicle and crew. And here this requirement can easily conflict with the requirement to preserve mobility. However, it is clear that the soldiers, whose safety depends on such machines, need increased off-road maneuverability, fast acceleration and higher speed, and all this without a negative impact on survivability. Such needs make it necessary to develop new power units and undercarriage systems in order to find optimal solutions that can meet these often contradictory requirements. However, in order to comply with them, a combination and balance of a number of design parameters is necessary. These include the characteristics of the suspension system, on which the quality of movement directly depends, the bearing surface of the tracks or wheels, which determines the ground pressure, the vehicle's ground clearance and engine output power. It is believed that the latter characteristic is the most important and most difficult to achieve. This is due to the fact that even in the issue of generating and distributing engine power, the designer needs to make compromises, sometimes even stepping on the throat of his own song. The increase in power in an armored vehicle is limited by factors such as the volume of the engine compartment, the need to maintain a power reserve, limitations on mass, and the need to meet the electricity needs of the onboard systems, such as communication equipment, navigation systems, sensors, and active and passive protection systems.
It is imperative that effective protection against current evolving threats is necessary, especially those that place the greatest demands on the power unit and the undercarriage of the machine. Protection almost inevitably means armor, and armor adds mass. There is a contradiction, which leads to uncomfortable compromises: as the level of threats increases, the level of protection also needs to be increased. Increasing the level of protection, as a rule, translates into a need for additional armor, and additional booking can increase the weight of the car. Saving or improving the performance of the armored vehicle inevitably entails an increase in engine power and efficiency of the transmission and actuators connected to it. However, the weight of the car is also determined by its size: the larger the car and the surface area that must be armored, the heavier it becomes. Thus, the new power unit (engine with transmission and drives) should not only be more powerful, but it should at least fit into the allotted volume or, preferably, have a smaller total volume. This criterion, above all, is absolute for power units designed to modernize existing armored vehicles, but also highly desirable for new platforms.
Armored cars, for example, this MBT Leopard 2A, have special requirements for the developers of engines and transmissions. They need more power to fit in as little as possible.
The generally accepted value of the level of mobility provided by an armored vehicle is the so-called power density or ratio of power (most often in horsepower) to vehicle mass. This ratio, although it does not take into account all the possible factors that determine mobility, is a suitable, albeit a rough criterion, and is useful both as a design parameter and as a tool for comparing different machines. As a rule, the greater the power density, for example, in hp per ton, the better the overall driving performance that the machine will show. Despite the fact that when evaluating a machine, its maximum speed is often taken into account, for a combat vehicle, the acceleration or acceleration of the engine (the ability to quickly and smoothly change from stable operation at minimum power to maximum power mode) may actually be much more important characteristic. Often overlooked in the vehicle’s characteristics is the ability to accelerate quickly and move quickly to a safe place in response to attacking actions is invaluable. It directly affects the survivability of the machine and its crew. Thus, the available power contributes not only to increased mobility, but also survivability, especially when used in combination with self-defense measures, including sensors for determining shot and laser irradiation, as well as passive and active countermeasures.
In the power unit for an armored vehicle, it is extremely important to achieve the required output power in the smallest amount. The key factor contributing to the increase in the mass of the machine is the surface area to be booked.
Power in small
Despite individual cases of the use of gas turbine engines, such as in the main combat family tanks (MBT) M1 Abrams manufactured by General Dynamics, the most popular engine for armored vehicles continues to be a diesel engine, or rather a multi-fuel diesel. One of the leaders in the production of power units is the German company MTU. Its integrated approach consists in the fact that the single “power unit” includes not only the engine, transmission and power drives, but also the subsystems for supplying and filtering air, cooling, generating electricity and others. Each of the components of the power unit is carefully designed and assembled in order to obtain the most compact and efficient solution. MTU recognizes that for the developer and integrator of military vehicles, the ratio of power to volume is a critical factor. Giovanni Spadaro, head of the state-owned enterprises department at MTU, explained that for them “the integration of all components into a single system is very important, we are constantly developing our philosophy of symbiotic development of all parts of the solution being developed. For us, this means that literally everything, architecture, concept, software and all parameters, is aimed at improving the characteristics of the final complete power unit. ” The impact of this approach on the final platform is huge, given the close cooperation with such major leading manufacturers of military vehicles as, for example, Krause-Mafei Wegmann (KMW), Nexter, BAE Systems and General Dynamics. The representative of General Dynamics Land Systems explained: “With regard to the power unit, more power - better, less size - better, cheaper - generally excellent, but with the mandatory increase in safety, reliability, noiselessness and serviceability."
MTU has demonstrated that the adaptation and modification for military purposes of commercial power units is suitable for light and medium armored vehicles, for example, the ARTEC Boxer four-axle combat armored vehicle, in which the MTU 8V199 TE20 diesel engine is installed. However, for heavier armored vehicles and tanks, their engines are needed, such as, for example, the 880 and 890 series engines, designed specifically for installation in heavy military platforms. The capabilities of modern power units are demonstrated in the Puma tracked infantry fighting vehicles. Spadaro said that “the MTU power unit for the Puma car includes a gearbox, a starter / generator and cooling and air cleaning systems. The MTU 10V 890 diesel engine is known for its very high power density and compact dimensions. Compared to other military engines of the same power class, mass and volume were reduced by about 60 percent. " The director of the special engines department at MTU commented that "This unit is more compact than any other previous power unit." The advantages of MTU engines are especially obvious when installing power units in previous-generation machines. Its engines from the EuroPowerPack model range are used by the French company GIAT (now Nexter) to replace the engines of Leclerc-EAU tanks for the United Arab Emirates. The engines of this family are also installed on the Challenger-2E MBT, while a significant amount was saved while simultaneously increasing the power reserve due to reduced fuel consumption.
Caterpillar, known for its heavy construction equipment, has become the main supplier of engines for tactical and armored vehicles. Its proposals for the military are based on ready-made commercial systems operating in many countries around the world. From here and considerable advantages - the decrease in cost connected with volumes of production, and availability of technical support. Nevertheless, the developments of the company are also known for military use, for example, the С9.3 engine with an increased power density of the HP 600. However, the real innovation is that the C9.3 is able to change its nominal power. In order to meet the strict European requirements for exhaust Euro-III, it switches to reduced mode to 525 HP. power. At Caterpillar, they note that “The advantage is that the user can choose the mode of operation. It is possible to achieve maximum performance during active operation in the field, but during training or when working in areas with civilians, you can switch to exhaust control. ” In fact, this “switch” is rooted in technology that Caterpillar has developed for commercial systems.
The company is invariably chosen for programs of replacement and modernization of existing fleets of armored vehicles. For example, its CV8 engine is currently mounted on the British Army's Warrior tracked infantry fighting vehicles. This work is carried out under a contract with Lockheed Martin to upgrade the machine to the WCSP standard (Warrior Capability Sustainment Program - the Warrior BMP capacity extension program), which will extend the operation of machines to 2040 of the year. Caterpillar is also changing the engine of armored vehicles of the American Army Stryker family with an HP 350 power. on the engine С9 power 450 hp The new engine "fits" in the volume, which occupied the previous engine. This replacement is carried out as part of General Dynamics’s proposal to introduce ESR-1 technical changes, which include an 910 ampere generator, suspension upgrades and other improvements.
Caterpillar "war-driven" engines are based on its special-engineered engines for heavy commercial vehicles. This provides benefits in terms of cost, logistics and availability. The С9 engine, part of the Stryker armored vehicle modernization program, is also widely used in construction vehicles.
Electric drives
Traditionally, power from the engine is transmitted to the wheels or tracks mechanically. Electric drives replace this physical connection with electric motors placed in driving wheels or sprockets. The energy for the operation of these electric motors can be taken from batteries, an internal combustion engine, or from both sources at once. In the “hybrid” approach, either a diesel or a gas turbine engine is used, which, being freed from mechanical connections, can now be installed anywhere in the chassis, which gives designers greater freedom in designing. It is also possible to install two engines, as implemented by the company BAE Systems in its mobile test installation HED (Hybrid Electric Drive). The representative of BAE Systems Deepak Bazaz noticed that two HED engines are connected to generators and batteries, which allows working in different modes: one engine runs in idle mode, saving fuel, two engines running when more power is needed, or a machine in silent mode It works only from batteries. The concept of HED is implemented on the tracked AMPV (Armored Multipurpose Vehicle) platform, but it is planned to be made scalable and used on any type of vehicle in mass, both wheeled and tracked. The experimental HED powerplant was modified by BAE Systems for the Northrop Grumman hybrid concept as part of its proposal for the ground combat vehicle of the American Army GCV (Ground Combat Vehicle).
The work of the NATO Technology Research Organization says: “The characteristics of hybrid electric vehicles regarding speed, acceleration, ability to climb and noiselessness exceed those of mechanically driven vehicles ... while fuel savings can range from 20 to 30 percent ". Electric motors also provide almost instant acceleration, good acceleration and better tractive effort. The latter is directly dependent on the improved torque, which is inherent in electric motors. For combat vehicles, this means several advantages: less reaction time when moving to the shelter, more difficult to get and better cross-country maneuverability. HED has two six-cylinder engines, a specially designed transmission from QinetiQ and lithium-ion batteries on 600 volts.
Another attractive aspect of an electric drive is its ability to generate more efficient and high levels of electrical energy. The power plant of the Northrop Grumman / BAE Systems GCV platform will be able to provide 1100 kilowatts, although it is significantly smaller and lighter than traditional power units. However, since energy storage is an important part of a hybrid electric drive, the mismatch of modern batteries becomes a serious problem. Therefore, currently several types of advanced batteries with higher energy density are considered for hybrid vehicles, including lithium-ion, nickel-metal hydride, nickel-sodium-chloride and lithium-polymer. However, all of them are still at the stage of technology development and have certain disadvantages that must be solved before they are considered suitable for use in military applications. Another area of work that needs to be developed so that hybrid drives can be massively mounted on armored vehicles is the removal of the design limitations of modern traction motors. Although successfully integrated into HED demonstration experimental samples, these systems have limitations in size, mass, and cooling. Until these problems are solved, all electrical circuits, despite their advantages, will remain an illusion for armored vehicles.
However, many research organizations retain an interest in the concept of electric drive. For example, in accordance with the contracts of the DARPA Advanced Defense Research Department, QinetiQ will test its concept of hub electric motors (geared motors), setting them up for testing on experimental running models. Numerous gear reducers, differentials and actuators will replace powerful compact electric motors in the wheels of the car. It is possible that this concept can also be implemented on existing wheeled armored vehicles. In fact, in June 2017, the company BAE Systems signed an agreement with QinetiQ to introduce new electric drive technology in combat vehicles. A representative of the company BAE Systems said that this would allow "to offer customers a proven low-cost technology that will enhance the capabilities of current and future combat vehicles."
BAE Systems, in collaboration with QinetiQ, developed and manufactured a demonstration sample of a hybrid HED solution for armored vehicles based on AMPV chassis
Future power challenges
Over the past decade, the needs of military vehicles for electric power have increased several times. Marc Signorelli, head of combat vehicles at BAE Systems, remarked that “in the future, armored vehicles will find it increasingly difficult to meet electricity needs.” Attempts are being made to solve this escalating problem. For example, for machines of the M2 Bradley family, a generator for 300 amperes CE Niehof is considered, and for the new AMPV platform, two generators for 150 are amps. MTU Spadaro stated that “the key factors that influenced and influenced the development of higher power generation solutions are the ever-growing mass of MBT and wheeled vehicles (mainly as a consequence of the requirements for increasing protection levels) and at the same time the need for more electricity for airborne systems of any type, be it electronics, protection complexes and crew comfort, for example, an advanced air conditioning system. ” The company MTU believes that “they are solved by deeper integration of electrical components into the power unit. A good example here is again the above mentioned MTU power unit of the Puma armored vehicle, which includes a starter / generator with a rated power of 170 kW, supplying current to two cooling fans, as well as the refrigerant compressor of the air conditioning system. "
The power of armored vehicles directly affects the combat capabilities and survivability. The main criteria for survival on the battlefield are as follows: “take all measures not to be noticed, if seen, not to be hit, if they are still caught, not to be killed”. The first is promoted by the ability to move to where your opponent does not expect you. The second requires quick acceleration and good maneuverability to find cover and is complicated by the ability of the enemy shooter to effectively capture the target to defeat. And the third is determined by the ability to take appropriate passive protection and use passive and active countermeasures. However, each of these criteria may adversely affect the others. For example, additional armor increases mass and, as a result, mobility.
Progress in the field of power plants for armored vehicles, new engines, transmissions and power drives, innovative methods of integration and layout allow the developers of military equipment to satisfy the most ambitious wishes of customers. Many of the improvements that we see on military platforms are directly taken from commercial projects: engines and on-board computers, digital electronic control, automatic control of system status, electric drives and energy storage, and, finally, practical implementations of hybrid solutions. However, the challenges of this fragile equilibrium are forcing the industry to develop more and more innovative solutions.
On the materials of the sites:
www.nationaldefensemagazine.org
www.mtu-online.com
www.gd.com
www.rheinmetall.com
www.cat.com
www.baesystems.com
www.darpa.mil
www.nato.int
www.armorama.com
defesaglobal.wordpress.com
pinterest.com
www.wikipedia.org
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