Cooling water circuit layout of the hottest hydrau

2022-08-16
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Abstract: This paper introduces the working principle of hydraulic retarder, and analyzes the layout of its cooling water path on passenger cars and trucks

key words: hydraulic retarder; Cooling system; Auxiliary braking; Layout

in recent years, the transportation industry urgently needs higher operating efficiency and faster driving speed, resulting in a sharp increase in the requirements for engine power. However, the efficiency of vehicle mounted braking system cannot be improved synchronously due to the limitations of many factors. Especially for passenger cars and some heavy trucks with high safety requirements, the traditional braking system can no longer meet the requirements. It is imperative to install auxiliary braking systems such as hydraulic retarders. But the heat dissipation of hydraulic retarder is a very important problem

1 working principle of hydraulic retarder

hydraulic retarder is a derivative type of hydraulic coupling, although it is not a transmission element, but a braking element for energy consumption and deceleration. When slow braking is to be carried out, the control system pumps the medium (oil) in the oil groove into the working chamber between the stator and the rotor, and the oil produces resistance to the rotor, slowing down the speed of the transmission shaft and producing a slow effect. It relies on the impact of the liquid circulating flow in the working wheel cavity on the fixed wheel blades to convert the kinetic energy of the vehicle into liquid heat energy, and then dissipate the heat energy through a certain cooling and heat dissipation method, so as to realize the deceleration and braking of the vehicle. When the retarder stops working, the oil is discharged from the working chamber due to the centrifugal effect of the oil, and the retarder loses the braking effect. The working diagram of the chemical resistance retarder of polyethersulfone is shown in Figure 1, which has excellent UV resistance and also protects the Polyethersulfone

due to the pressure difference between the inlet and outlet caused by the working fluid in motion, the liquid medium circulates. When flowing through the heat exchanger, the heat energy converted from the kinetic energy of the vehicle is taken away by the cooling water from the engine cooling system and dissipated. For the hydraulic retarder, as long as the cooling system has sufficient heat dissipation capacity, its retarding capacity is infinite. When the hydraulic retarder slows down, the heat generated is transmitted to the cooling system of the vehicle. The physical limit of the retarder's retarding capacity is determined by the cooling energy. The driver can make the best use of the cooling system by using appropriate driving methods. Next, take Voith hydraulic retarder as an example to introduce the layout and connection of the cooling water circuit of the retarder

2 arrangement and connection of cooling water circuit

the cooling water circuit of the hydraulic retarder must be designed so that 100% of the cooling water in the water circuit is fed into the retarder. The minimum flow of cooling water is related to the capacity of the water pump and the resistance of the whole cooling system. When the speed is n=2000r/min, the minimum flow of cooling water shall not be less than 5L/s. The cooling water of the retarder must be introduced after the engine is cooled, that is, it must be connected to the pressure water pipe of the water pump (between the engine and the radiator inlet), as shown in Figure 2:

the general water pipe kit for passenger cars and trucks should include soft and hard pipe parts of the cooling water pipe, soft and hard pipe clamps, solder, etc. In this mode, a dual thermostat with an external thermostat insert is usually used, as shown in Figure 3, to separate the large and small cycles of the engine cooling water circuit and introduce it into the retarder cooler

the cooling water circuit layout of front and rear drive passenger cars and ordinary freight cars is shown in Figure 4

large passenger cars with rear engine and rear drive should adopt the layout as shown in Figure 5

3 precautions for arranging cooling water pipes

the following precautions should be paid attention to when arranging cooling water pipes:

⑴ the cooling water pipes installed in the vehicle must avoid electrification and must be accurately aligned with the nozzle

⑵ all water pipes must be connected with high-performance cooling water pipes, avoiding the use of formed pipes

⑶ the head of the cooling water pipe must be made into beads to prevent slipping. Beaded surface roughness not more than 25 μ m。 The pipe head must be free of burrs or cracks, otherwise the cooling water pipe made of silicone resin will be damaged

⑷ the arrangement of cooling water pipes shall not exceed the highest point of the engine, and there shall be a space with the cockpit of the driver

(5) the cooling system and water pipes must be ventilated reliably

⑥ each water pipe must support extruded polystyrene board, not only for heat preservation, but also fixed on the driving device with pipe clamps, and the maximum spacing between pipe clamps is 1m

⑺ the pipe clamp must not be fixed on the frame in the area where the driving device (engine, transmission, retarder) is located, otherwise there will be a risk of leakage due to vibration. It is only allowed to use the water pipe for vehicle cooling water path, and it cannot be replaced by hose. (end)

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